Cataract Surgery for Greenhorns

Ophthalmology Competencies: ACGME Competencies

noreply@blogger.com (MedRounds Publications) — Fri, 06 Jan 2006 01:27:00 +0000

Ophthalmology Competencies: ACGME Competencies

VIDEO: Adjusting Chair Height

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VIDEO: Using the microscope foot pedal for cataract surgery.

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References

noreply@blogger.com (MedRounds Publications) — Tue, 04 Oct 2005 20:47:00 +0000

Koch, Paul S., Simplifying phacoemulsification safe and efficient methods for cataract surgery, 5th ed, Thorofare, NJ Slack, 1997. [book]

Seibel, Barry. Phacodynamics: Mastering The Tools And Techniques Of Phacoemulsification, 4th ed. Thorofare, NJ Slack, 2004. [book]

U.S. Dept. of Health and Human Services. Practice Clinical Guideline #4 - Cataract in Adults: Management of Functional Impairment , AHCPR Publication No. 93-0542, February 1993. [cited October 1, 2005] [external link].

Arbisser LB. Managing intraoperative complications in cataract surgery. Curr Opin Ophthalmol. 2004 Feb;15(1):33-9. [pubmed]

Bellucci R. Anesthesia for cataract surgery. Curr Opin Ophthalmol. 1999 Feb;10(1):36-41. [pubmed]

Horiguchi M, Miyake K, Ohta I, Ito Y. Staining of the lens capsule for circular continuous capsulorrhexis in eyes with white cataract. Arch Ophthalmol. 1998 Apr;116(4):535-7. [pubmed]

Kallio H, Rosenberg PH. Advances in ophthalmic regional anaesthesia. Best Pract Res Clin Anaesthesiol. 2005 Jun;19(2):215-27. [pubmed]

Linebarger EJ, Hardten DR, Shah GK, Lindstrom RL. Phacoemulsification and modern cataract surgery. Surv Ophthalmol. 1999 Sep-Oct;44(2):123-47. [pubmed]

Naor J, Slomovic AR. Anesthesia modalities for cataract surgery. Curr Opin Ophthalmol. 2000 Feb;11(1):7-11. [pubmed]

Tognetto D, Cecchini P, Ravalico G. Survey of ophthalmic viscosurgical devices. Curr Opin Ophthalmol. 2004 Feb;15(1):29-32. [pubmed]

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Chapter 6- Approaching Different Kinds of Cataract

noreply@blogger.com (MedRounds Publications) — Sun, 02 Oct 2005 13:56:00 +0000

Ectopia lentis

Displacement of the lens

Subluxed - partially displaced within pupillary aperture
Luxated or completely displaced from the pupil congenital, developmental, or acquired

Epidemiology

Trauma is the most common cause.
Greater than 50% of patients with Marfan's syndrome exhibit ectopia lentis

Pertinent clinical features

Sub or total luxation of the lens
Phacodonesis
Marked lenticular astigmatism
Iridodonesis
Impaired accommodation

Non-traumatic differential diagnosis
Primarily ocular

Pseudoexfoliation
Simple ectopia lentis
Ectopia lentis et pupillae
Aniridia
Congenital glaucoma

Systemic

Marfan's syndrome
Homocystinuria
Weil-Marchesani syndrome
Hyperlysemia
Ehlers Danlos
Sulfite oxidase deficiency

Surgical therapy options

ICCE
Phaco/ECCE

Attend to any vitreous in anterior chamber – staining with Kenalog helps to visualize the clear vitreous [view video]
Use iris hook to stabilize anterior lens capsule
Capsular tension ring (CTR) with or without Cionni modification
IOL in bag – mild cases aided by CTR/Cionni ring
Iris fixated posterior or anterior IOL
Angle supported IOL
Sulcus sutured posterior chamber IOL
Contact lens or spectacles

Intumescent Cortical Cataract

Etiology

Opacification of the cortical lens fibers
Swelling of the lens material creates intumescent cataract

Clinical features

Initially vacuoles and water left in the lens cortex
Wedge shaped opacities or cortical spokes
Progresses to form white intumescent cortical cataract
Risk of phacolytic glaucoma

Risk factors

Smoking
Ultraviolet light exposure
Diabetes mellitus
Poor nutrition
Trauma

Phaco/ECCE

Capsular staining techniques
Capsulorhexis techniques

Initial small tear
Removal of liquid cortical material to relieve capsular tension
Liberal use of viscoelastic material

Complications of surgery

Increased risk of capsular radial tear
Increased risk of vitreous loss
Increased risk of loss of lens material into vitreous

Hypermature Cataract

Etiology

Opacification of the cortical lens fibers
Swelling of the lens material creates intumescent cataract
Degenerated cortical material leaks through capsule leaving wrinkled capsule
Pertinent clinical features
Wrinkled anterior capsule
Increased anterior chamber flare
Calcium deposits in lens
White cortical material
Risk of phacolytic glaucoma

Phaco/ECCE

Capsular staining techniques
Capsulorhexis techniques

Initial small tear
Removal of liquid cortical material
Use of viscoelastic material in anterior chamber and bag

Complications of surgery

Increased risk of capsular radial tear
Increased risk of vitreous loss
Increased risk of zonular dialysis
Increased risk of loss of lens into the vitreous

Morgagnian Cataract

Etiology

Opacification of the cortical lens fibers
Can be swelling of the lens material as in intumescent cataract
Can be wrinkled capsule as in hypermature cataract
Hallmark sign - liquefied cortex allows nucleus to move freely in bag

Pertinent clinical features

Wrinkled anterior capsule
Increased anterior chamber flare
Dense brown nucleus freely moving in capsular bag
Calcium deposits within the lens

Phaco/ECCE

Capsular staining techniques
Capsulorhexis techniques

Initial small tear
Removal of liquid cortical material to decompress the pressure in the lens bag.
Use of viscoelastics material in anterior chamber and bag to stablize the anterior capsule during the CCC.

Stabilize nucleus with viscoelastic

Complications of surgery

Increased risk of capsular radial tear
Increased risk of vitreous loss
Increased risk of zonular dialysis
Increased risk of loss of lens into the vitreous

Anterior Polar Cataracts

Etiology

Opacity of the anterior subcapsular cortex and capsular
Bilateral
Non progressive usually
Frequently autosomal dominant

Clinical features

Usually asymptomatic with good vision
Central opacity involving the anterior capsular
Associated with microphthalmos, persistent papillary membrane, anterior lentic
Differential diagnosis includes penetrating capsule trauma

Phaco/ECCE - with capsulorhexis start away from polar cataract make bigger and go around polar cataract if possible

Posterior Polar Cataracts

Etiology

Opacity of the posterior capsular cortex and capsule
Familial autosomal dominant bilateral; sporadic unilateral
Slowly progressive

Pertinent clinical features

Good vision but at nodal point more symptomatic than anterior polar
Central opacity involving the posterior capsule
Glare
Differential diagnosis includes

Posterior subcapsular cataract
Penetrating capsule trauma
Mittendorf dot

Phaco/ECCE

No hydrodissection
Sculpt out a bowl to relieve capsular tension
Gentle hydrodelineation
Leave central opacity or take at the end of surgery

Complications

Increased risk of posterior capsular tear
Increased risk of vitreous loss
Increased risk of loss of lens material into vitreous

Perforating and penetrating injury of the lens

Etiology of this disease

Penetrating injury results in cortical opacification at site
Rarely can seal resulting in a focal opacity
Usually progresses to complete opacification

Pertinent clinical features

Focal cortical cataract
White cataract with capsular irregularity/scar
Full thickness corneal scar

Laboratory testing

B-scan ultrasound - check if posterior capsular intact? Is there an intraocular foreign body?
CT scan to rule out intraocular foreign body

Phaco/ECCE

Capsular staining to identify traumatic tear
No hydrodissection if posterior penetration suspected
Usually can aspirate in younger patients without need for nucleofractis

Complications

Increased risk of anterior radial capsular tear
Increased risk of vitreous loss
Increased risk of lens material in vitreous
Increased risk of retinal detachment

Diabetes mellitus and cataract formation

Etiology

Increased aqueous glucose concentration drives glucose into lens
Glucose converted into sorbitol that is not metabolized by lens
Sorbitol creates an osmolar gradient forcing hydration of the lens
This sorbitol induced lenticular hydration

Decreases accommodation
Changes the refractive power of the lens
Generates cataract

Pertinent clinical features

Snowflake or true diabetic cataract

Bilateral
Posterior and anterior subcapsular, cortical vacuoles and clefts

Typical nuclear, cortical, or posterior subcapsular cataracts

Phaco/ECCE

Indicated when view of posterior pole is poor
Standard technique

Complications

Exacerbation of diabetic macular edema

Focal or grid laser therapy prior to surgery if indicated/possible
Sutured wound to allow early laser therapy if indicated

Increased risk of cystoid macular edema

Pretreatment with steroid and non-steroidal drops
Prophylactic treatment for 1-3 months with steroid and/or non-steroidal drops (prednisolone and ketorolac drops)

Cataract Associated with Uveitis

Etiology

Posterior subcapsular cataract

Initially an iridescent sheen appears in the posterior cortex
Followed by granular and plaque like opacities

May progress to or involve anterior subcapsular cortical fibres
May present as cortical cataract without posterior subcapsular component
Associated with uveitis and corticosteroids to treat uveitis
May progress rapidly to a mature cataract

Pertinent clinical features

Central opacity of the posterior cortical fibers
Cortical cataract
Posterior synechiae
Papillary membrane
Anterior chamber cell or flare

Prior to phaco/ECCE

Several months without inflammation
1 week prior to surgery suppresses immune system

Topical agents in those patients who typically quiet with topical agents alone
Oral prednisone in those that typically require oral steroid with a flare
Consider intraoperative IV steroids

Phaco/ECCE

Synechiolysis with viscoelastic agents/hooks
May require iris hooks to stabilize floppy iris and control papillary aperture
Capsular dye to allow continuous tear
IOL material acrylic=heparin coated PMMA better than silicon
Consider aphakia in children with juvenile rheumatoid arthritis (JRA)

Complications of cataract surgery

Increased risk of post operative inflammation
Increased risk of post operative pressure spike
Increased risk of cystoid macular edema
Consider using steroid and non-steroidal drops for months following surgery

Exfoliation Syndrome (Pseudoexfoliation)

Etiology

Systemic disease in which a fibrillar material is deposited in the eye

Similar material to the basement membrane proteoglycan
The material is found throughout the body

Within the eye the fibrillar material comes from the lens capsule, iris, and ciliary body
The zonules are weak in this condition
Often asymmetric or even unilateral
Glaucoma develops when the fibrillar material blocks the trabecular meshwork

Epidemiology

Patients tend to be over 60 years of age
Geographic clustering suggests a hereditary pattern

In Scandinavia for example pseudoexfoliation causes 75% of glaucoma

Glaucoma develops in 22-82% of patients with exfoliative material
Increased incidence of age related cataract

Pertinent clinical features

Ground glass appearing deposition of fibrillar material on anterior lens capsule

Iris may sweep material into rings on the lens capsule
Best viewed with dilation

Transillumination defect and fibrillar material at the papillary margin
Open angle with brown clumps of fibrillar material on trabecular meshwork
Flakes of fibrillar material on corneal endothelium
Evidence of zonular weakness

Phaco or iridodonesis
Lens subluxation or even luxation

Phaco/ECCE

Use of iris hooks for capsular support during phacoemulsification
Use of capsular tension ring with or without Cionni modification [view video]
Placement of AC IOL, sutured Cionni ring with capsular IOL, sutured PC IOL
Sutured iris IOL
Consider surgery sooner while zonules are relatively strong
Minimize zonule stress during surgery

Complications of phaco/ECCE

Increased risk of capsular radial tear
Increased risk of zonular dialysis
Increased risk of loss of lens material into vitreous
Increased risk of late dislocation of IOL capsular bag complex into vitreous
Post operative intra-ocular pressure spike

Completely remove OVD
Intra-operative miotic
Postoperative aqueous suppressant

Conclusion

This eBook is written for the young surgeon learning cataract surgery. I hope you have found this educational material useful during your training. This eBook is currently being expanded to discuss the topics presented here in detail. Good luck!

Tom Oetting, MS, MD

Associate Professor of Clinical Ophthalmology, University of Iowa

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Chapter 5 - Managing Surgical Complications

noreply@blogger.com (MedRounds Publications) — Sun, 02 Oct 2005 13:08:00 +0000

Vitreous Prolapse

Causes of Vitreous Prolapse

Capsular tear

Anterior tear extending posteriorly - most common cause
Posterior tear - secondary to phaco too deep, I/A, or another instrument
Pre-existing condition, e.g.: posterior polar cataract, iatrogenic from prior pars plana vitrectomy, penetrating lens trauma

Zonular dialysis

Iatrogenic from forceful rotation or pulling on the capsule
Pre-existing condition, e.g.: trauma, pseudoexfoliation, Marfan's

Signs of Vitreous Prolapse

Denial
Chamber deepens
Pupil widens
Lens material no longer centered
Particles no longer come to phaco or I/A
Lens no longer rotates freely

Basic Principles of Vitrectomy

Close the chamber [view video]
Separate irrigation and cutter
Cut low / Irrigate high [view video]

Vitreous Presenting early in case - while most of crystalline lens is in eye

Strongly consider converting to ECCE

If topical, do subtenons injection for additional anesthesia [view video ].
Close temporal incision with 10-0 nylon suture and follow ECCE steps except use lens loop
Have Wescott scissors ready when looping out lens to cut vitreous
Close with 3-4 Vicryl safety sutures

Sometimes you can proceed with Phaco very carefully

Seal off capsular hole with liberal use of Viscoat (cohesive OVD will not work)
Keep phaco occluded in the lens as much as possible
Consider using sheets glide to seal off hole -- trap nucleus in AC
Work with one or two large pieces (rather than chopping into many small bits which may fall into the posterior-pole of the eye)

Following removal of residual nucleus

Anterior vitrectomy, perform Weck cell vitrectomy (i.e., using a Weck cell sponge to pull vitreous from wound and cutting vitreous with Wescott scissors. Remember that tugging on the vitreous also applies forces that are tugging on the retina where the vitreous is attached.)
Dry removal of residual cortical material with syringe on 27 gauge cannula
Use J-cannula if needed for subincisional material
Consider staining with Kenalog
Place IOL if possible in sulcus or AC IOL (if AC, don't forget peripheral iridotomy to prevent pupil block glaucoma)
Use Miochol to bring pupil down, which seats sulcus IOL. Also, peaked pupil helps to detect vitreous that is coming forward into the anterior chamber.

Vitreous Presenting Mid-Case - while removing cortical material

Most common time vitreous presents
Place viscoat in area of tear or dialysis before removing instruments
Anterior vitrectomy

Split into an irrigating cannula (e.g. 23 guage cortex extractor) and the vitreous cutter (without sleeve)
Suture wound and use two paracenteses one for the cutter and one for irrigating cannula
Irrigate high and cut / suck low – creates a pressure gradient to push the V back . [view video]
Settings: low vacuum in the 100 range, low bottle height in the 50 range, max cut rate
Try to get some of the residual cortical material

Following anterior vitrectomy

Dry removal of residual cortical material with syringe on 27 gauge cannula
Use J-cannula if needed for subincisional material
Consider staining with kenalog (see below)
Place IOL if possible in sulcus or AC (if AC don't forget peripheral iridotomy) . [view video]
Miochol to bring pupil down

How to deal with Vitreous Presenting late in the case - while placing IOL

Stabilize the IOL by placing one haptic out of the wound or in the AC
Perform anterior vitrectomy as described above - attempt to get the cutter below the IOL
Place both haptics in the sulcus if possible (cannot use the Alcon SA60 lens in sulcus)
Use Weck cell sponge to ensure wound is clear of vitreous
Consider stain (see below)
Use Miochol in the anterior chamber to check pupil

Staining the Vitreous with Kenalog
[view video]

Great idea by Scott Burk at Cincinnati Eye
Prepare Kenalog by removing preservative and diluting 10:1

Modified Method (of Burk):

TB syringe to with 0.2 ml of well shaken Kenalog (40 mg/ml)
Remove the needle and replace with a 5 (or 22) micron syringe filter (Sherwood Medical)
Force the suspension through the filter and discard the preservative filled vehicle
The Kenalog will be trapped on the syringe side of the filter
Transfer the filter to a 5 ml syringe filled with balanced salt solution (BSS)
Gently force the BSS through the filter to further rinse out preservative
Repeat rinsing a few times
Place a 22 gauge needle on the distal end of the filter
Draw 2 ml of BSS into the syringe through the filter to resuspend the Kenalog
The Kenalog (now without preservative) will stain vitreous strands white

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Chapter 4- Post-Operative Care

noreply@blogger.com (MedRounds Publications) — Sun, 02 Oct 2005 12:08:00 +0000

Phacoemulsification

Usually requires 2 or 3 post operative visits

same afternoon 4-6 hours later (to catch IOP peak) or next AM
(optional) one week later (to check on inflammation)
3-4 weeks later to give glasses

First Visit	RAPD, VFF to CF
	VA	expect about 20/40 better with pinhole
	Slit Lamp Examination (SLE)	expect corneal edema proportional to ultrasound time 1-2+ cell and flare look for corneal abrasion especially if patched
	IOP	if < 8 look hard for leak with Seidel test if 9 - 29 probably OK if > 30 start with CoSopt, Alphagan recheck in 45 min if > 40 suppress aqueous and bleed until pressure is stable <30 consider seeing the next day lower these guidelines in patients with history of diabetes, anterior ischemic optic neuropathy, etc
	Usually can see fundus without dilation. Document no RD or choroidal
	Plan	Tobradex 1 drop qid (or separate floroquinolone and prednisolone acetate) follow up 2-4 weeks later in routine cases see patients one week later with IOP spike, vitreous loss, history of uveitis next day with wound leak, big corneal abrasion, etc...
	give	a simple large print post operative instruction sheet

Week #1	RAPD, VFF to CF
	VA	expect about 20/30 pinhole 20/20
	SLE	expect little corneal edema and trace to 1+ cell and flare
	Consider fundus exam with poor vision, diabetes, floaters, etc..
	plan	taper Tobradex: 1 drop tid for 7 more days, then 1 drop bid for 7 days, etc. or (stop fluoroquinolone/taper steroid as above) follow up usually 3-4 weeks later full activity

Week #2-4	RAPD, VFF to CF
	VA	expect about 20/25 pinhole 20/20
	Manifest Refraction (MR)	consider suture induced astigmatism
	plan	give manifest refraction (MR) for glasses
		follow up 1 year

ECCE or ICCE

Usually at least 3 post operative visits

same afternoon 4-6 hours later (to catch IOP peak) or next AM
one week later (to check on inflammation)
4-5 weeks later to check astigmatism for suture removal or give glasses

Much of the emphasis is on suture removal for astigmatic control

Day #1	RAPD, VFF to CF
	VA	expect about 20/200 better with pinhole
	SLE	expect significant corneal edema 2-3 +cell and flare look for corneal abrasion especially if patched
	IOP	if < 8 look hard for leak with Seidel test if 9 - 29 probably OK if > 30 start with CoSopt, Alphagan recheck in 45 min if > 40 suppress aqueous and bleed until pressure is stable <30 consider seeing the next day lower these guidelines in patients with history of diabetes, anterior ischemic optic neuropathy, etc
	Usually can see fundus without dilation and, document no RD or choroidal.
	plan	fluoroquinolone 1 drop qid prednisolone acetate 1 drop qid Cyclogyl 1% bid follow up one week later usually see patient next day with wound leak, big corneal abrasion, etc.
	Give	a post operative instruction sheet

Week #1	RAPD, VFF to CF
	VA	expect 20/100 and about 20/50 with pinhole keratometry for fun -- expect about 7 diopters of astigmatism don't waste time with refraction
	SLE	expect little corneal edema and 1-2+ cell and flare
	usually can see fundus when on cyclogyl, document no RD
	plan	Discontinue antibiotic (tell patient to keep bottle in refrigerator for suture removal) Discontinue Cyclogyl if inflammation is less than 1+; o/w continue Taper Prednisolone: 1 drop qid for 7 more days, then 1 drop tid for 7 days, then 1 drop bid for 7 days, then 1 drop qd for 7 days, then discontinue
	Follow up 5 weeks later (allows healing time before suture removal)

Week #6	RAPD, VFF to CF
	VA	expect 20/80 and about 20/40 with pinhole
	keratometry	expect about 5.0 diopters at 90 don't get confused and read backwards e.g. for 5.0 D at 90: left dial could read 40 D right dial reads 45 D
	Manifest Refraction (MR)	Start with streak retinoscopy or auto refract (usually on with clear media) Start with 2/3 of cylinder from K's and adjust SE to -1.0 (usually very close)
	SLE	Look at the wound and decide which sutures look tight.
	suture lysis	Indicated when cylinder is >= 2 D on Manifest Refraction (MR), or >= 3 D on K's (if you did not do Manifest Refraction (MR)) if less than 2 D on Manifest Refraction (MR), stop, high fives, don't cut anything Remove tightest suture near axis of cylinder on Ks only cut one suture at week 6-8 visit can cut two beyond week 8 If tight axis is between sutures cut both (think vectors)
	plan	Full activity Antibiotic drop 1 drop qid for 4 days (following each suture removal)
	follow up	If no sutures need to be removed (will never happen) give glasses -- usually +2.5 D add for bifocals with manifest refraction (MR) follow up 1 year. otherwise return every 1-2 weeks for additional suture lysis

After that,	you really have about three three choices (don't stall): pull a stitch (i.e. cylinders at axis of stitch is greater than 2 D on MR) give glasses (i.e. no stitch to pull or cylinder is less than 2 D on MR) get FFA or OCT because you suspect CME
	Don't waste time thinking about other possibilities because not everybody is going to be 20/20.

WARNING SIGNS OF POST-SURGICAL INFECTION (ENDOPHTHALMITIS)

increased pain
sudden drop in vision
increased redness
mucopurulent discharge
usually occurs within 1-2 weeks post-operatively
when in doubt, see your patient

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Chapter 3 - Staining the Lens Capsule

noreply@blogger.com (MedRounds Publications) — Sun, 02 Oct 2005 11:31:00 +0000

The white cataract used to be one of the most difficult surgeries to do. Capsular staining, however, has changed these cases from complex to routine. Capsular stains (e.g., indocyanine green and trypan blue) are useful whenever the capsule is hard to see, for instance:

Classic white cataract
Traumatic cataract with possible anterior capsular tear
Dark red or brown cataract with limited red reflex
Started rhexis and then lost capsule in an area of cortical spokes or dense portion of cataract

Indocyanine Green (ICG)

reference: Horiguchi M, Miyake K, Ohta I, Ito Y. Staining of the lens capsule for circular continuous capsulorrhexis in eyes with white cataract. Arch Ophthalmol. 1998 Apr;116(4):535-7. [PUBMED]

ICG is used to stain the lens capsule
The ICG is washed out with OVD
Leaving the anterior capsule green in contrast to the white cataract
CCC is performed in the usual fashion but easily visualized
Useful for delineating anterior capsular trauma
Stain in the vitreous may be toxic to the retina so use the least amount possible
Preparation:

Draw up 0.5 cc of aqueous solvent (comes with ICG) into syringe
Place aqueous solvent into vial of 25 mg ICG and shake
Draw up 4.5 cc of BSS into syringe
Place BSS (original article was BSS+; but BSS OK) into ICG vial and shake some more
Osmolarity is 270 (plasma 285)
Final concentration is 0.5%

Trypan Blue (Vision Blue)

Approved by the FDA for capsular staining in winter 2005
Cheaper, better, faster
Already mixed for capsular staining

Surgical Technique for either stain

Place paracentesis
Fill anterior chamber with air
Can place some dispersive OVD at wound if air leaks
Drop/rub ICG solution or Trypan Blue onto anterior capsule with cannula
Fill anterior capsule with OVD
Make typical wound into anterior chamber
Perform CCC (capsule will be green or blue, lens will not)

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Chapter 3 - ophthalmic viscoelastic devices (OVD)

noreply@blogger.com (MedRounds Publications) — Sun, 02 Oct 2005 11:19:00 +0000

There are two basic categories of ophthalmic viscoelastic devices (OVD): [view video]

[click on image for larger view]

Different jobs demand different OVDs

1. Maintain space:	e.g. AC during rhexis bag during IOL insertion	cohesive best
2. Create space:	e.g. Creating sulcus shift lens material	cohesive best
3. Sealing off:	e.g. Sealing capsular tear keeping iris away	dispersive best
4. Coating:	e.g. Protect corneal endothelium lubricate cornea [view video]	dispersive best

Removal of OVD

Removal

Dispersive harder to remove

Short molecules don't stick together during I/A
but short molecules create less post op IOP spike

Cohesive is easier to remove

Longer molecules stick together during I/A
Longer molecules block the trabecular meshwork for big IOP spike

Adaptive OVD

Properties of dispersive OVD at high shear rate (e.g. during phaco)

Properties of cohesive OVD at low shear rate (e.g. during IOL placement)

Very long fragile chain molecules that break with flow rate

One product on market -- Healon 5

Form anterior chamber, which will cause intraocular pressure problems if not removed.

Arshinoff Shell

Phase I during CCC

First place dispersive OVD
Then place cohesive OVD just over lens
Then dispersive is pushed up to coat endothelium
As soon as phaco starts cohesive is aspirated and dispersive coating remains

Phase II during IOL insertion

First place cohesive OVD in the bag
Then place dispersive OVD just inside wound to seal prior to IOL placement
When IOL is inserted, dispersive helps to keep cohesive in place; bag formed

Properties of Cohesive & Dispersive OVDs During Key Steps of Phacoemulsification

Step	Cohesive	Dispersive
CCC	Easy to fill AC Can suddenly lose OVD through wound	Must completely fill AC Stays in AC
Phaco	Goes away with first vacuum	Stays on endothelium Particles can stick to endothelium Increased risk of burn
IOL insertion	Easy to open/maintain bag Easy to remove material	Hard to remove residual material

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Chapter 3 - Phaco Machine Settings Primer

noreply@blogger.com (MedRounds Publications) — Sun, 02 Oct 2005 03:47:00 +0000

Four main components and software to tie them together

Pump - most important variable

Parameters are dependant on tubing diameter and compliance

Parameters are dependant on phaco needle diameter

Allows removal of the emulsified lens material

Set low during sculpting and higher during quadrant removal and chopping

Irrigation System

Typically is just an adjustable bottle held high to allow infusion of fluid

Machine can adjust bottle height

Machine can turn fluid on and off

Ultrasound (U/S) hand piece

Vibrates needle at a set rate in the 20,000 to 40,000 HZ range

Increasing the ultrasound power increases the excursion of the needle

With increasing load the frequency and excursion lessens

Modern multiple crystal hand pieces can better handle load

Footswitch

Typically controlled with dominant foot (without shoes)

Accelerator like pedal is common across all brands

Position 0 - everything is off

Position 1 - irrigation is on, no pump, no ultrasound

Position 2 - irrigation is on, pump is on, no ultrasound

Position 3 - irrigation is on, pump is on, ultrasound is on

Phaco Pumps

Please read the classic definitive text for more details: Barry S. Seibel, Phacodynamics, Slack

Flow rate: amount of fluid passing through the tubing (cc/min) also aspiration flow rate

Vacuum: difference in fluid pressure among two points, e.g. tip of needle and AC (mm Hg)

Vacuum based Pumps – e.g. Venturi pump ( Millennium, Accurus ), diaphragm

Increasing pump power increases vacuum directly and flow rate indirectly

Venturi pump requires external source of compressed air

This has limited acceptance of this pump (make sure your ASC has the proper air lines)

Compressed gas flows over open top of rigid cassette attached to tubing

Flow of gas creates vacuum much as flow over wing creates lift

Flow rate is dependant on resistance of flow

Roughly analogous to electric current voltage relationship (Ohm's law)

i=e/r where e = voltage (analogous to vacuum)

i = current (analogous to flow rate)

r = resistance (analogous to tubing and occlusion)

more flow rate with less resistance (fixed vacuum)

more flow rate with more vacuum (fixed resistance)

Pump settings -- No settings for flow rate only vacuum

Fixed: no matter how deep the into position 2 or 3 vacuum is fixed

Great for chopping and quadrant removal

Variable: vacuum increases from 0 to max when deeper into pos 2 or 3

Great for I/A can slowly increase vacuum to just what you need

Flow based pumps – e.g. peristaltic pump ( Infinity, Sovereign, and Legacy )

Increasing pump power increases flow rate directly and vacuum indirectly

Vacuum is dependant on resistance of flow

Roughly analogous to electric current voltage relationship (Ohm's law)

e=ir where e = voltage (analogous to vacuum)

i = current (analogous to flow rate)

r = resistance (analogous to tubing and occlusion)

more vacuum with more resistance (fixed vacuum)

more vacuum with more flow rate (fixed resistance)

Pump Settings

Set vacuum cutoff and flow rate

Vacuum cut off

Seems like you are setting the vacuum

Really setting the vacuum at which the pump stops

Increasing the vacuum does not increase pump speed

Flow rate or Aspiration FR rate (AFR) sets pump speed (cc/min)

with modern peristaltic pumps (eg. Infiniti ) for each foot position you can have:

Fixed or variable flow

Fixed or variable vacuum cut off

Variables affecting Phacoemulsification

Flow rate	Vacuum Cut off	Comment/Application
Fixed	Fixed	Independent of depth in foot position Low numbers good for sculpting
Fixed	Variable	More depth higher vacuum cut off Limited control Typical I/A setting on Alcon 20,000
Variable	Fixed	More depth faster pump More control pump speed changes Bimodal setting on Alcon 20,000
Variable	Variable	Both change with depth in foot position Feels like a venturi pump

Phaco Pump Comparison

Pump	Pros	Cons
Vacuum e.g. Venturi	Less posterior occlusion surge Better for vitreous removal Material comes to tip easily	Need source of compressed gas Need rigid cassette
Flow e.g. Peristaltic	Better for sculpting No need for compressed air	Post occlusion surge Need occlusion for vacuum to build

Ultrasound Control

Four ultrasound modes: continuous, pulse, burst, and hyperpulse
Continuous

Phaco is on in position three
Usually increasing ultrasound power with depth into foot position

Pulse

Phaco pulses with duty cycle on and off
Usually with equal on and off time or 50% duty cycle (time on/cycle time)
Usually the rate (or inverse of duty cycle) is fixed (Hz)
Usually increasing ultrasound power with depth into foot position

Burst

Bursts of power come with off time that decreases with depth into foot position
Usually when floored in position 3 -- ultrasound power becomes continuous
ultrasound power is fixed

Hyperpulse

Uses short on time pulses e.g. 25% on; 75% off
Fixed duty cycle; fixed pulse rate
Usually increasing ultrasound power with depth into foot position

Advantages & Disadvantages of Various Modes

Mode	Advantages	Disadvantages	Applications
Continuous	Simple	Repels nuclear material Hot	Sculpting
Pulse	Less hot	Can repel nuclear material	Choo choo chop Segment removal
Burst	Less hot Holds material well		Chopping
Hyperpulse	Followability with Long off cycle Cool with long off cycle		Sculpting Bimanual small incision

My Typical Settings

[click on table for larger view]

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Chapter 3 - Phacoemulsification Step-by-Step

noreply@blogger.com (MedRounds Publications) — Sun, 02 Oct 2005 02:36:00 +0000

Please read the following textbook for additional information- Koch, Paul S., Simplifying phacoemulsification safe and efficient methods for cataract surgery (5th ed), Thorofare, NJ Slack, 1997.

Phacoemuslifcation Step-by-Step

Indications: Most common method of cataract removal.

Contraindications: few, maybe: almost no zonular support or extremely hard lens.

Pre-op: orbital massage can be used to compress vitreous – use Honan balloon or super pinky to decrease intraocular pressure.

Anesthesia:

Topical +/- intracameral non preserved lidocaine

Retrobulbar and lid block

Subtenon's block

Rarely general anesthesia, e.g.: claustrophobia, dementia, tremor

Complications of Anesthesia:

Retro-bulbar hemorrhage: If this occurs, then delay case and consider cantholysis.

Inject/perforate eye ball with needle during a retrobulbar block: If this occurs, then delay case and cryo/laser area, and pray. Call risk management.

Subconjunctival Hemorrhage: This is not serious, and forget about it.

STEPS

Rarely superior bridle suture used (infraducts eye to allow superior exposure).

Potential complications: a) driving needle into vitreous – if this occurs then delay case and cryo/laser area.

Paracentesis with #75 blade, or some other sharp knife, mark #75 with ink. Fixation with 0.12 forceps or with fixation ring helps to stabilize the eye.

Potential complications:

a) put in wrong place – if this occurs, then make another paracentesis;

b) too small – if this occurs, then make another wound;

c) too big – if this occurs, then suture later;

d) nick lens capsule – if this occurs, include nick during capsulorhexis;

e) nick iris – this is not serious and forget about it.

If topical case, then instill lidocaine (1% non-preserved in TB syringe with Troutman 27 or 30 g). There is some debate about utility of instilling lidocaine in the anterior chamber.

Potential complications:

a) stings – this is normal and reassure the patient;

b) put in wrong medicine – if this occurs, then wash out anterior chamber and pray;

c) Cornea epithelial toxicity from anesthetic – I recommend coating the cornea with dispersive OVD [view video].

Place ophthalmic viscoelastic device (OVD) into anterior chamber. One method is the Arshinoff shell technique: 1^st dispersive (e.g. Viscoat), then cohesive (e.g. Healon). The Arshinoff shell technique provides two advantages: dispersive OVD coats corneal endothelium and protect from ultrasound energy and cohesive OVD maintains chamber during the first part of procedure. Alternatively, use just one type of OVD. Healon is the cheapest at the VA hospital.

Potential complications:

a) shoot loose cannula into anterior chamber – if this happens, then tighten it better next time;

b) Air bubbles – if this happens, then suck out the air with syringe or place OVD distal and force out.

Wound -- Comes in three main types: limbal, scleral, and corneal.

Advantages of a limbal wound: Easy to convert to ECCE, Instruments don't distort cornea, and Great for greenhorns.

Disadvantages of a limbal wound: Induces astigmatism, Always requires suture, iris prolapse more common, Requires conjunctival manipulation & cautery, eye is red after surgery.

Advtanges of a scleral wound: Rarely induces astigmatism and seals nicely.

Disadvantages of a scleral wound: Hard to convert to ECCE, Technically difficult, Iris prolapse more common, Requires conjunctival manipulation & cautery, Instruments distort cornea, and Eye is red after surgery.

Advantages of a corneal wound: Rare astigmatism, No cautery or conjunctival manipulation, and Eye is white after surgery.

Disadvantages of a corneal wound: Hard to convert to ECCE, Technically difficult, Instruments distort cornea, and Possible increased risk of endophthalmitis. [VIEW VIDEO OF PERITOMY TO PREVENT CONJUNCTIVAL DONUT DUE TO TRAPPED FLUID]

Style	Advantages	Disadvantages
Limbal	Easy to convert to ECCE Instruments don't distort cornea Great for greenhorns	Induces astigmatism Always requires suture iris prolapse more common conjunctival manipulation & cautery Eye is red after surgery
Scleral	Rarely induces astigmatism Seals nicely	Hard to convert to ECCE Technically difficult Iris prolapse more common conjunctival manipulation & cautery Instruments distort cornea Eye is red after surgery
Cornea	Rare astigmatism No cautery or conjunctival manipulation Eye is white after surgery	Hard to convert to ECCE Technically difficult Instruments distort cornea possible increased risk of endophthalmitis

Capsulorhexis – most important step of this surgery. Anterior chamber must be filled with viscoelastic. There are two basic techniques: continuous curvilinear capsulorhexis (CCC) and can opener.

Advantages of the CCC: Less risk of vitreous loss, IOL is very stable, and Less risk of PCO.

Disadvantages of the CCC: Hard to do, May need capsular stain with poor red reflex, and Needs relaxing incisions for ECCE.

Advantages of Can Opener Technique: Easy to do, Red reflex not required, and Allows ECCE nucleus expression.

Disadvantages of Can Opener Technique: Increased risk of vitreous loss, IOL is less stable, and Increased risk of PCO. We will discuss the CCC because this is the preferred surgical technique. The goal of CCC is to produce a central circular opening slightly small than the optic diameter.

There are three basic techniques for CCC (only way to learn about this is to watch videos):
- a) Cystitome - initial cut and control of tear with cystitome (best with cohesive OVD) [view video];
- b) Combo - initial cut with cystitome, most of tear with forceps (most common technique) [view video];
- c) Forceps - use sharp forceps to cut and then grab capsule to complete tear.

Potential complications:
- a) Poor red reflex – if this occurs then, stain the lens capsule with Trypan Blue or ICG;
- b) Tear starting to go radial – if this occurs then, add OVD;
- c) Radial tear - Use scissors to restart in other direction, Relaxing tear 180 across, Can opener and conversion to ECCE, or Debulk lens by sculpting out bowl prior to hydrodissection;
- d) if too small, then enlarge after placing IOL;
- e) if too big, then forget about it because this is not a serious issue;
- f) zonular laxity – if there is evidence of zonular laxity during the case, then consider placing iris hooks to stabilize the capsular bag.

Hydrodissection - This is the second most important step of the procedure. Skip this step with posterior polar cataract, perforating lens trauma or early post vitrectomy cataract. Use balanced salt solution in 3 cc syringe with troutman 27 gauge or similar. Inject fluid just under capsule to cleave cortex from capsule. Look for a fluid wave. Don't stop till you get enough. Don't stop till you get enough! Rotate lens to ensure the job is done because if the lens does not rotate then you will not be able to perform the cataract extraction. May prolapse lens with a large capsulorhexis, which can be a good thing if you want to phacoemulsify the lens in the anterior chamber.

Potential complications:

a) No fluid waive – if this occurs, then try again in different spot, increase force, or use bursts and gently push on nucleus between bursts;

b) Iris Prolapse - Remove dispersive OVD. If using a clear cornea wound, then use sub-incisional iris hook [view video ];

c) Prolapse nucleus – if this occurs then, Brown technique or Pop n Chop, flip into ciliary sulcus, or push back into bag;

d) Blowout post capsule – too late, but was this because of s/p vitrectomy, trauma or posterior polar cataract? If this occurs and the lens drops, then clean up the vitreous in anterior chamber, place IOL, and call your retina surgeon.

Phacoemulsification (phaco): The goal is to remove lens with the minimum ultrasound to reduce damage to the cornea. Trend is to use increasing vacuum and decreasing ultrasound power to remove nucleus. Phacoemulsification of the nucleus can be done by several techniques:
- a) Endocapsular - keeping the nucleus in bag during phaco;
- b) Supracapsular - prolapsing nucleus into sulcus during phaco;
- c) Anterior chamber shell - prolapsing shelled out nucleus into anterior chamber;
- d) ½ bag ½ anterior chamber --tipping nucleus on side ½ in bag; ½ in anterior chamber – a.k.a., Brown Technique, Pop-n-Chop.
  [view table summarizing the advantages and disadvantages of phacoemulsification techniques ].

There are numerous ways to disassemble a lens nucleus:

a) sculpting out a bowl and then collapsing material into center;

b) divide and conquer is a classic technique, and all phaco surgeons must master this technique;

c) chopping - horizontal chop, vertical (quick) chop, stop n chop.
[view table summarizing the advantages and disadvantages of different fragmentation techniques ].
[view table of possible complications during phacoemulsification ].

Cortical Aspiration - Aspiration is used to grab and peel the cortex off not suck it up. Dangerous procedure and is the most common time for vitreous loss in experienced surgeon. Sub-incisional removal is the most difficult, especially with a small rhexis. Adequate hydrodissection makes this step easier.
[view table of possible complications during cortical aspiration ].

Fill Bag with OVD - Form the lens bag not the sulcus. Use cohesive OVD in the bag. Consider dispersive OVD adjacent to wound to seal – Arshinoff Shell -- this method uses two OVDs sold in a rather expensive kit. Place OVD ahead of the cannula -- don't pierce the post capsule with cannula.

Wound may need to be extended to allow placement of the lens - PMMA IOL (doesn't fold) needs a wound that is slightly more than optic size. Many injected IOL's don't need extension from incision for phaco needle. Well constructed wound that is a bit bigger seals better than a stretched small wound.

Lens is placed into capsular bag [ view video ]:
1. A) PMMA IOL - Grasp IOL and trailing haptic with forceps (e.g. Kelman-McPherson), place leading haptic into bag; optic into AC; release forceps, place trailing haptic into bag with hook or forceps.
2. B) Folded IOL - Folded and placed in special forceps. Incision size grows a bit with increased power of IOL – 3.5 mm range. Moustache style fold: wider incision but haptics flow into bag. Axial style fold: smaller incision but haptics need guidance.
3. C) Injected IOL - Many different systems available. For instance, the single piece acrylic (Alcon SA 60) and plate IOL is most simple [view video]. Three piece IOL requires some haptic care and manipulation. Be careful of Descemet's membrane with IOL insertion (especially with injectors).
[click here for larger image]

Is the IOL right side up? - Correct side up looks like 7-O-L-even.

[click here for larger image]

IOL is designed for right handed surgeon to easily rotate it.

When the IOL is upside down, the IOL looks like an S so Stop.

Upside down angulated 3 piece IOL creates myopic shift with anterior IOL shift

[

click here for larger image

]

Make sure that both Haptics are in the Bag

May need to add OVD - often some is lost during insertion of IOL

Most common cause of decentration: one haptic in bag; one in sulcus

Bag has less space than sulcus - ½ in IOL shifts toward sulcus haptic

[click here for larger image]

Rotate IOL so that Haptics are 90 degrees from the wound
- Set yourself up for the next step, which is irrigation and aspiration (I/A)
- Allows I/A tip to get under IOL to remove OVD under IOL
- Frees most common site of residual cortical material from haptic

Special IOL Placement Conditions

Anterior Capsular Tear

Single piece acrylic in the bag - creates little tension on the bag

3 piece with both haptics in the sulcus

Zonular Dialysis

Capsular Tension Ring with any IOL

3 piece IOL with PMMA haptic oriented toward weak area of zonules

Posterior Capsular Tear

Dispersive OVD in the post capsular hole -- gently place IOL into bag

Place 3 piece in sulcus +/- capture of optic by centered anterior CCC [view video]

No Capsular Support

AC IOL: there are 3 sizes depending on white to white size

Iris Sutured PC IOL

Scleral Sutured PC IOL

Iris Clip IOL (Artisan™ - not approved by FDA for aphakia yet)

Potential Complications	What to do about it
Place IOL up-side down	Can leave as is - accept myopic shift, or Take one haptic out of wound with Sinsky hook Fill with OVD above and below IOL One hook above and one below -- Flip IOL
Inadvertent sulcus placement	Fill with OVD -- Rotate into bag with hook If a 3 piece can leave in sulcus with myopic shift Do not leave single piece acrylic (Alcon SA60) in sulcus
IOL doesn't center	Usually one haptic in sulcus one in bag dial both into bag or both into sulcus Possible zonular dialysis if nearly centered leave it alone rotate IOL carefully for best centration with 3 piece often haptics best at weak area check wound for vitreous consider placement of CTR place miochol to help check for vitreous Haptic damage (especially with 3 piece IOL) may have to replace IOL
Tear in Descemet's	Use care to not extend tear Place Air Bubble at end of case – post op position wound up -- bubble seals Descemets
Marred IOL	If not central forget about it If central replace IOL
Lens Material behind IOL	Rotate haptic 90 deg from wound Toe down with I/A and get under IOL With aspiration tip showing at all times aspirate

14. Sutures are preplaced

Pre-place sutures while OVD maintains chamber

Usually need 2 interrupted or one X suture with 6 mm scleral tunnel

Usually need 1 interrupted suture with 3 mm limbal wound

Usually need no sutures with proper 3 mm wound of cornea or sclera

15. OVD is removed with I/A device

As always keep tip opening up

Go under IOL to remove OVD, especially if you have been having IOP problems post op

Potential Complications	What to do about it
Chamber Instability	Increase bottle height Check Tubing and fluid level Wound too big? -- suture end of the wound Decrease vacuum
Catch Iris [view video]	Reflux fluid Continue and maintain your bearings
Grab capsule and tear zonules	Capsular tension ring Place dispersive OVD in weak area

16. Sutures are tied

/1/1 for 10-O nylon in the sclera

2/1/1 for 10-O in clear cornea to allow small knot to rotate and bury

17. Other

Give antibiotic ointment or drops, we rarely give subconjuntival antibiotics

Consider postoperative povidine iodine

Patch to protect cornea if retrobulbar or topically, if subtenons anesthesia was used

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Chapter 3 - Old School

noreply@blogger.com (MedRounds Publications) — Sat, 01 Oct 2005 03:54:00 +0000

Old School Cataract Surgery Techniques

intracapsular cataract extraction (ICCE) - lens with capsule removed [VIEW VIDEO]

extracapsular cataract extraction (ECCE) - lens removed and much of lens capsule left in place. Can be done via two approaches: manual or planned ECCE done with expression of nucleus through large; or, phacoemulsification ultrasound device breaks up nucleus through small incision. [VIEW VIDEO]

Pars plana lensectomy (PPLx) is an approach by retinal surgeons often at time of vitrectomy.

Comparison of Cataract Surgery Techniques

[CLICK ON TABLE FOR LARGER VIEW]

ICCE – [view video]
Indications: rarely indicated today - I have only done five cases. Unstable lenses with severe zonular laxity.
Be Careful: children, capsular rupture, high myopia, Marfans, vitreous present.
Pre-op: orbital massage or osmotic agents to reduce vitreous pressure.
Anesthesia: Retrobulbar and lid block. Rarely general anesthesia, e.g., claustrophobia, dementia, tremor.
Procedure:

Superior bridle suture

May need a scleral support ring in high myopes

Peritomy of about 170 degrees

Limbal incision of about 170 degrees chord length in the 11-12 mm range

Safety sutures are preplaced - usually 7-O Vicryl

Small peripheral iridotomy is placed

Alpha-chymotrypsin was placed to degrade zonules (no longer available)

Anterior surface of the lens is dried with a cellulose sponge

Cryo probe is placed on mid-periphery of the lens and frozen

Lens is removed with a side to side motion through incision

Wound is closed with safety sutures

Vitreous is attended to if needed

Anterior chamber lens is placed

Wound is closed with 10-O nylon

Planned ECCE (with nucleus expression) – [VIEW VIDEO]

Indications: Still indicated today. Hard lenses with tentative corneal endothelium (weak indication).
Contraindications: poor zonular support.
Pre-op: consider orbital massage or osmotic agents to reduce vitreous pressure
Anesthesia: Retrobulbar and lid block, sub-tenon's block, or rarely general anesthesia, e.g., claustrophobia, dementia, tremor.
Procedure:

Procedure Superior bridle suture

Peritomy of about 170 degrees

Initial limbal groove in sclera with a chord length in the 11mm range

Initial entry into anterior chamber to allow capsulotomy (3 mm)

Instill viscoelastic (see appendix 2)

Remove anterior capsule (usually with can opener approach)

Mobilize lens (physically with cystitome or with hydrodissection--be careful)

Extend initial incision to full length of groove (with scissors or knife)

Safety sutures are preplaced usually 7-O vicryl

Lens removed with lens loop or with counter pressure technique

Wound is closed with safety sutures

Cortical material is removed using I/A device (either automated or manual)

Instill ophthalmic viscoelastic device (OVD)

Lens is placed in the posterior chamber

Wound is closed with 10-O nylon

OVD is removed

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Chapter 3 - Anesthesia

noreply@blogger.com (MedRounds Publications) — Wed, 28 Sep 2005 14:21:00 +0000

Table: Comparison of the different modalities of anesthesia

[CLICK ON TABLE FOR LARGER IMAGE]

Coating the cornea with OVD protects the epithelium [view video].

The Retrobulbar Block [view video] provides effective anesthesia and akinesia for cataract surgery.

The Advantages of Retrobulbar Anesthesia:

Great for long cases (>45 minutes)

Great for inexperienced surgeon (get akinesia, proptosis)

Helps to increase exposure

Nystagmus (can be used for Yag laser with nystagmus also)

The Disadvantages of Retrobulbar Anesthesia:

Blood thinners increase risk of retrobulbar hemorrhage (several studies -- bleeding risk low for ASA & coumadin)

Monocular (RB injection often forces admission until patch removed)

Long axial eye length increases risk of globe perforation

May be risky with the presence of scleral buckle

Steps to perform a Retrobulbar Block [view video]:

Place 1 drop (gtt) of topical anesthetic into both eyes

Clean lower lid with alcohol wipe

Fill 5cc syringe with mixture of 1% lidocaine/0.375% bupivacaine and Wydase (HYALURONIDASE) without epinephrine

Place blunt 23 gauge needle (1.5 inch flat grind) on syringe

Start at the junction of the lateral 1/3; 2/3 junction of the lower lid

Use the index finger of non-dominant had to create space between floor and globe

Aim perpendicular to lid until passing through the septum (1st pop)

Then redirect more superior advancing about 1 - 1½ inches (2nd pop) into muscle cone

First pull syringe back to ensure you are not in a blood vessel

Inject 4 cc slowly into retrobulbar space

Retract needle until just under skin (in orbicularis muscle) and inject remaining 1 cc

Have patient look straight ahead during procedure

Apply pressure on closed eye for a minute or so – be alert for retro bulbar hemorrhage

Subtenon’s Anesthesia [view video] will provide additional anesthesia during a topical case if needed.

The Advantages of subtenon’s anesthesia:

Great when Topical case getting complicated (e.g., Convert to ECCE, anterior vitrectomy)

Great for patients on blood thinners and concerned with risk of retrobulbar injection

The Disadvantages of subtenon’s anesthesia:

Conjunctiva gets red and sore

Conjunctival chemosis can be a problem

Steps to perform a subtenon’s block [view video]:

Give topical anesthesia (probably already done if converting from topical case)

Prepare 3cc syringe with 1% lidocaine / 0.375% bupivacaine

Place lacrimal canula with gentle curve to approximate that of the globe

Pick a quadrant for the block (best to go for a lateral quadrant to avoid oblique muscle)

Have the patient look away from the chosen quadrant to increase exposure

Use 0.12 forceps to retract conjuctiva

Make small incision down to sclera with wescott scissors

Redirect wescott scissors with curve down and bluntly dissect through quadrant

Dissect past the equator (similar to using stevens tenotomy scissors in peds/retina)

Use 0.12 Forceps for counter traction

Place canula through incision and direct past the equator before injecting

The mixture should flow easily and cause minimal chemosis

If not redissect with the wescots and get more posterior

The Advantages of Topical Anesthesia:

Experienced fast surgeon

Monocular patients get fast rehabilitation

On blood thinners and concerned with risk of retrobulbar injection

The Disadvantages of Topical Anesthesia:

Greenhorn surgeons need akinesis

Cannot use in patients with nystagmus

The Steps for Topical Anesthesia:

Intracameral 1% nonpreserved lidocaine can supplement topical

Many studies have shown no benefit

If the case is long or if iris is moving it seems to help in my hands

Usually placed just after paracentesis is formed

Use about 0.5 cc

May sting a bit so I usually warn the patient: “I'm giving you the rest of the numbing medicine and you may feel it for a second or two and then it will be very easy for you.”

Table: Comparison of the different types of anesthetics

[CLICK ON TABLE FOR LARGER IMAGE]

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noreply@blogger.com (MedRounds Publications) — Tue, 27 Sep 2005 14:10:00 +0000

TITLE PAGE

1) Assessment

2) Preoperative

3) Surgery

4) Postoperative

5) Managing Complications

6) Approaching the Unusual Cataract

REFERENCES

Chapter 2 - Operating Microscope Basics

noreply@blogger.com (MedRounds Publications) — Tue, 27 Sep 2005 13:40:00 +0000

Learn how to use your foot pedal and practice before your first case. [VIEW VIDEO]

[CLICK ON IMAGE FOR LARGER VIEW]

-Ask yourself: “where will I be sitting?

Are you operating from a superior approach: 1) Superior is better when you may have iris trauma (tolerated better under the lid); 2) superior is best for ECCE, ICCE, trabeculectomy, and junior phaco

Typical phaco is from a temporal approach to avoid the brow

Proper Sequenceto adjust Equipment to your body. [VIEW VIDEO]

1) Place retrobulbar block first

2) Put assistant's eyepiece and camera on proper side of microscope

3) Push center focus and center XY position buttons on microscope (at UI same button)

4) Adjust ocular inter-pupillary distance and zero both objectives

5) Lower surgeon’s chair

6) Raise bed height to allow both feet under bed onto both pedals

Dominant foot – phaco pedal
Non dominant foot microscope footswitch
Take off shoes

7) Manually move microscope into focus

8) Raise surgeon chair height enough to allow surgeon to see comfortably into oculars

9) Prep and Drape

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Chapter 2 - Selecting the Intraocular Lens

noreply@blogger.com (MedRounds Publications) — Tue, 27 Sep 2005 12:53:00 +0000

SELECTING THE INTRAOCULAR LENS (IOL)

Brief History of the IOL

-Harold Ridley placed first lens in 1949, a huge polymethyl-methacrylate (PMMA) Intraocular Lens (IOL) (about the size of the cataract)

-1950s rigid anterior chamber lenses were used with ECCE and ICCE

bullous keratopathy was common

chronic inflammation led to cystoid macular edema (CME) and glaucoma

-Later iris fixation lenses were used to avoid contact with the angle

Some IOLs would suture onto the iris

Others would clip on (used today as the Artisan lens)

These lenses would frequently dislocate

-Closed loop flexible anterior chamber lens were next and kept PK corneal transplant surgeons in business

-Rare and weird names for IOL: pseudophakos, lenticulus

Today

-Modern open loop flexible anterior chamber lenses are a great success

-The development of viscoelastics (OVDs) allows safe placement

Posterior chamber lenses are most commonly used today

3 basic materials – PMMA, acrylic, silicone

PMMA is the time tested material but requires a large incision

Use the largest optic that can fit incision, e.g., 6.5 or 7 for ECCE

Most surgeons use foldable acrylic or silicon lens to allow small incision

-Accomodating IOL has been approved by the FDA

-Multifocal (Restore™, Rezoom™, Array™) and toric lenses (Staar™) are available

IOL material considerations

[CLICK ON TABLE FOR LARGER VIEW]

IOL design considerations

[CLICK ON TABLE FOR LARGER VIEW]

Four things you need to know to calculate correct IOL power:

1) Desired postoperative SE

-Usually -0.50 to -1.00 diopters (D) is the plan. Why?

Myopia is better than hyperopia if your calculations are off

-1.00 D gets you about 20/40 at far and you can see well at mid distance

A spectacle overcorrection of -1.00 will eliminate induced IOL magnification.

Sometimes however you may not want a spherical equivalent (SE) of -0.50 to 1.00 D

-the fellow eye has a significant refractive error and must be matched

anisometropia > 3.0 D is not well tolerated

-you are confident and want to go closer to plano – good luck

-patients wants this to be a reading eye with goal of -2.00 D or so

2) Axial eye length (AEL)

-Contact probe ultrasound AEL device

Contact probe on eye measures distance to fovea

Pushing on the eye with probe introduces error (AEL too short)

Re-measure when AEL difference between eyes >0.3mm

Re-measure when AEL <22 or >25

-OCT (IOL Master)

Measure both eyes

Less dependant on technician for accuracy

Fails in dense nuclear sclerosis (NS) or even mild posterior sub-capsular cataract (PSCP)

-Immersion ultrasound

Gold standard when in doubt

Significant technician skill required

Should get whenever patient is getting B scan anyway for dense cataracts

3) The power of the cornea

-Keratometric measurement of both eyes -- should be about the same

Autorefractor

IOL Master measures K's for you

Keratometer/corneal topography

-Difficult when patient has had refractive surgery

4) The post operative position of the IOL

-The more anterior the IOL the less power the IOL needs

-Goal is to place a posterior chamber (PC) lens

These can end up in the bag (best) or sulcus (anterior to ant. capsule)

Placement in the sulcus creates about a 0.75 D myopic shift in glasses

-Always plan to have available anterior chamber (AC) lenses

These are placed anterior to the iris with haptics that settle into the angle

These are used when the capsule is lost and cannot hold an IOL

When too small they can tilt and when too large they can hurt

Estimating the IOL power for emmetropia:

-Formulas started with a theoretical model by Fydorov, Collenbrander et all, 1970s

-Based on geometric optics

-Power = N/(AEL-ACD) – N/(N/K-ACD)

where: Power is the expected power of IOL for emmetropia post op

N is the aqueous and vitreous refractive index

ACD is the post operative AC depth of the IOL

AEL is the axial eye length as measured via an ultrasound device

K is average of the two keratometric axes

-But you don't know ACD or post operative depth of the IOL pre op!

Useful Formulas use regression analysis or other tricks to estimate ACD

[CLICK ON TABLE FOR LARGER VIEW]

Selecting the IOL power for your patient

-The SRK computes the lens power for emmetropia; but, you probably want -0.50 to -1.00 D

-The ultrasound or IOL Master produces a table with IOL power mapped to desired post op. SE

Roughly a change in IOL power 1.5 results in spherical equivalent (SE) change of 1.0 D

For instance, formula gives 19 D for emmetropia, about 20.5 D will give -1.00 D SE post op.

-If your estimated IOL power is unusual you are probably wrong

Double check your calculations

Trust what happened with the other eye's IOL if applicable

Ask yourself was the patient very hyperopic as a young person (e.g., in the big war)

-Estimate the power for both the AC and the PC lens and compare several formulas

-Then if convinced that the calculations are right, make sure the IOL powers are available

-Be sure that all lenses possibly needed for your case are in OR

You will need a posterior chamber lens for the bag

A Sulcus Lens: the more anterior Sulcus lens will need 0.5-1.0 less diopters of power and cannot use single piece acrylic (Alcon SA60 lens) in sulcus.

AC lenses: typical AC lenses come in 3 diameters: 12.5, 13.0, and 13.5 mm and sized at surgery by adding 1 mm to the “white to white” horizontal limbal diameter.

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Chapter 2 Preoperative Preparation - Consent

noreply@blogger.com (MedRounds Publications) — Mon, 19 Sep 2005 05:12:00 +0000

Consent
The Consent is the most important part of the pre-operative visit.

There are five essential parts of a consent:

identify yourself

describe all options - cataract surgery or hold off on cataract surgery

describe the procedure

describe potential risks - 1/100 chance vision will be worse after surgery

describe potential benefit - 9/10 chance vision will be normal with glasses following surgery

Talk your patient through the procedure briefly:

we replace your cloudy natural lens with a clear artificial lens

use the words: injection (with RB), cut, and possible stitches in your discussion

explain that we do not use the laser. (There is much confusion about Yag capsulotomy for secondary cataract)

we may patch your eye overnight following the surgery

we will prescribe new glasses when the eye is stable – 2-4 weeks post-op

Benefits:

95% of patients are better than 20/40

96% of patients are better vision than pre-op

I lower these percents with increasing retinal or optic nerve disease

Risks:

1% vision worse than pre-op

death (loss of eye (irregular pupil (1:100)

posterior capsule opacity (PCO) cataract ( 1:20 requiring laser in 2 years with the Alcon SA60/MA60 intraocular lenses)

Document

Functional visual disability, give examples

Complete consent form legibly

In patient's chart write something like: “I discussed the risks and benefits of cataract surgery with Mr. Jones and his son in terms they seemed to understand. Mr. Jones expressed to me that he understood the small but real risk of surgery, including loss of vision as outlined in the consent form, and he decided to have surgery.”

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Chapter 1 Assessment - Difficulty Factors

noreply@blogger.com (MedRounds Publications) — Sun, 18 Sep 2005 14:42:00 +0000

Why should you assess the difficulty during the preop?

Which surgeon should do case (e.g., Attending vs. 1st year resident)
Estimate length of case
Determine need for additional supplies/equipment
Determine the type of anesthesia

Difficulty Factors (in decreasing order of importance):

Zonular laxity (e.g., due to pseudoexfoliation syndrome, history of trauma, Marfan's syndrome)
Small pupil size (why is it small? pseudoexfoliation syndrome, diabetes after laser treatments, central posterior synechaie (CPS), floppy from Flomax)
Cannot lay flat for very long, e.g. COPD, claustrophobia, tremor, severe obesity
Big brow limiting superior access
Narrow angle limiting anterior chamber space
Predisposition to corneal decompensation, e.g., corneal guttata, posterior polymorphous dystrophy (PPMD), and hard nucleus
Poor red reflex due to a white or black cataract making case difficult.
Previous surgery, such as existing trabeculectomy surgery or pars plana vitrectomy (PPVx)
Predisposition to exposure, eg: botox treatment with lid paralysis, previous lid trauma, and diabetes.
Patient is taking anticoagulants, e.g., coumadin, aspirin, or Plavix.
Monocular

Table: Factors Affecting Difficulty

[CLICK ON TABLE TO EXPAND]

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Chapter 1 Assessment - Evaluation of Patients with Cataract

noreply@blogger.com (MedRounds Publications) — Sun, 18 Sep 2005 13:18:00 +0000

Ask yourself?

Is the cataract causing the visual decline?
Is the cataract secondary to a systemic or ocular condition?
Could the eye/patient survive cataract surgery if indicated?
Surgery is indicated for patients with symptoms that disrupt their daily activities.

Symptoms of a cataract

Visual acuity -- usually a gradual decline over years with posterior sub-capsular cataract (PSCC). Visual Acuity (VA) can decline over days. Often near VA decline is greater than far VA decline in PSCC.
Glare -- night driving problems, halos, especially with PSCC and cortical.
Myopic shift -- “second sight”, especially in nuclear sclerotic cataract.
Diplopia -- monocular, especially in PSCC and cortical

Indications for cataract surgery

Functional, functional, functional.
Document difficult with reading, driving, glare, recognizing faces
If the patient is having difficulty with daily tasks, then this is the indication for surgery.
Read: US Dept. of Health and Human Services Practice Clinical Guideline #4 - Cataract in Adults: Management of Functional Impairment
Must document functional decline (in Iowa, we use a form with the patient's signature)
Best corrected Visual Acuity <= 20/50 at far or near acceptable to VA Hospital, Medicare, etc.
Best corrected Visual Acuity > 20/40. Concentrate documentation on functional disability, eg. monocular diplopia, glare disability, occupational impairment, ect...
Uncommon indications: lens induced disease, eg. phacomorphic glaucoma, or medical need to visualize the fundus, eg. view to help exam for diabetic retinopathy.

General Issues

Can your patient lay flat for 30-60 minutes? The surgery may be more complicated when there is back pain, chronic obstructive pulmonary disease (COPD), or Congestive Heart Failure(CHF). Consult with their family physician to help address general medical issues before surgery.
Can your patient lay still? The case may be more difficult with young males, tremor, or claustrophobia. If laying still is a problem, then consider general anesthesia for the patient's safety and to reduce intraoperative complications. The risks and benefits of general anesthesia should be discussed with the patient.
Look at the medicine list. Is your patient taking coumadin, Plavix, or aspirin (ASA), and if so can they/should they stop these anti-coagulants? Is the patient taking Flomax (tamsulosin) for their prostate? – Flomax has been associated with intraoperative floppy iris syndrome (IFIS). [VIEW VIDEO IN EXTERNAL VIDEO PLAYER]:

consider iris retractor to help with IFIS
Chronic Steroid Use – usually no need for stress steroid dose unless patient is scheduled for general anesthesia.
Does your patient have latex and drug allergies? Surgery by have to performed with latex-free materials and gloves.
Can your patient tolerate their post operative care? Do they need help putting in their drops? Monocular patients may need significant post-operative help (eg. admission if patched post-operatively).

Past Ocular History

Complete the manifest refraction in both eyes. Fellow eye (non-operative eye) refraction may be needed to help with intra-ocular lens (IOL) selection. Document the VA in both dim and bright light conditions (room lights on and trans-illuminator 45 degrees to side) to check for glare symptoms. When the vision is poor – document no improvement with +/- 3 diopters lenses.
Examine Pupils. Check relative afferent pupil defect (RAPD) – as always critical – especially if patient's vision remains poor after surgery. Dilated pupil Size – useful when selecting among surgeons (see difficulty factors).
Check Confrontation Visual Field (CVF). If the cataract is dense, then check Light Perception (LP) in all four quadrants (instead of echo).
Keratometer readings of both eyes -- do prior to other cornea manipulations.
External Exam - Document if there is abnormal tear function, lid malposition/exposure, blepharitis, or spasm. If the patient has a prominent brow, then consider a temporal approach or schedule for a more experienced surgeon.
Slit Lamp Exam - Document cornea guttata, posterior-polymorphous dystrophy (PPMD), map-dot-fingerprint dystrophy (MDF), or corneal exposure problems. Document lens hardness, phacodonesis, pseudoexfoliation( PXF), or posterior polar cataract.
Gonioscopy - Important if you need to place an anterior chamber lens. Especially important with history of uveitis and possible anterior synechiae.
Dilated Fundus Exam - Not mandatory to complete a dilated fundus exam if you or trusted colleague have looked recently. Dilation the day before will inhibit dilation the day of surgery, which is undesireable. If the vision is poor, then ask yourself if the poor view matches the poor vision of the patient. If not, then the cataract may not be the cause of visual decline. Look carefully at patients with diabetes, and consider pre-operative fluorescein angiogram or OCT. Document normal macula, appearance of optic nerve, and posterior vitreous detachment if present.
Special Tests: The use of the potential acuity meter (device that projects an eye chart around lens onto the retina) is rarely helpful. With no view, consider echography, but echography is not necessary without RAPD and there is LP in four quadrants on CVF. Specular microscopy for corneal endothelial cell count is rarely needed, e.g. FDA Studies, Fuchs' dystrophy. Consider pachymetry in patients with corneal edema, e.g. Fuchs' dystrophy.

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Chapter 1 Assessment - Types of Cataracts

noreply@blogger.com (MedRounds Publications) — Sun, 18 Sep 2005 12:38:00 +0000

Classic Types of Cataract

CLICK ON TABLE FOR LARGER SIZE

Nuclear Cataract

Epidemiology / Risk Factors

Age
Riboflavin, vitamin C, vitamin E and carotene may decrease risk of nuclear sclerosis
Cigarette smoking increase the risk of nuclear sclerosis

Symptoms / History

Gradual progressive loss of vision
Second sight -- development of myopia due to increased lenticular refractive index
Monocular diplopia
Decreased color discrimination especially blue

Clinical features

Central yellow to brown discoloration of the lens
Myopic shift
Bilateral
Decreased penetration of cobalt blue slit beam through lens

Posterior Sub-Capsular Plaque (PSCP)

Epidemiology/Risk Factors

Younger patients than with nuclear or cortical cataracts
Diabetes mellitus
Radiation
Corticosteroids
Uveitis and retinitis pigmentosa
Smoking

Symptoms/history

Progressive loss of vision, sometimes rapid
Glare, halos
Monocular diplopia

Clinical features

Axial opacity of the posterior cortical material that initially has an iridescent sheen and appears in the posterior cortex that is followed by granular and plaque like opacities.
Can be confused with posterior polar cataract and mittendorf dot
Can see with direct but best viewed with red reflex through slit lamp

CLICK ON IMAGE FOR LARGER SIZE

Cortical Cataract

Epidemiology/Risk Factors

Younger patients than with nuclear cataracts
Diabetes mellitus
Sunlight
Trauma
Smoking

Symptoms/history

Progressive loss of vision, sometimes rapid
Glare, halos
Monocular diplopia

Clinical features

Opacity of the cortical fibers from posterior to central
Sometimes wedge shaped forming cortical spokes
Can progress to intumescent or hypermature cataract
Usually medial and inferior from UV exposure

CLICK ON IMAGE FOR LARGER SIZE

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TITLE PAGE

noreply@blogger.com (MedRounds Publications) — Sun, 18 Sep 2005 11:31:00 +0000

Cataract Surgery for Greenhorns
Table of Contents
Chapter 1 - Assessment
Chapter 2 - Preoperative
Chapter 3 - Surgery
Chapter 4 - Postoperative
Chapter 5 - Managing Complications
Chapter 6 - Approaching the Unusual Cataract
References

Thomas A. Oetting, MS, MD
University of Iowa
VAMC Iowa City

Copyright © 2005 Thomas A. Oetting, MS, MD

Published and distributed by MedRounds Publications, Inc.
All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher.
Published in The United States of America.

DISCLAIMER

The following material is intended for licensed physicians trained to practice medicine. The practice of medicine has associated risks and complications. The Authors and MedRounds Publications, Inc. do not intend for this material to replace proper medical and surgical training, and we shall not be liable to any user of our materials or any third person as a result of use of our educational materials. Although the published material has been reviewed by licensed physicians for accuracy at the time of publication, medicine and the standard of care may change quickly. Physicians are reminded, therefore, that guidelines for care can change and opinions can be controversial. Neither MedRounds Publications, Inc., the sponsors nor contributing institutions, nor the individual authors and editors are responsible for deletions or inaccuracies in information or for claims of injury resulting from any such deletions or inaccuracies. We advise physicians to consult the primary research literature before implementing any new treatments.

The author has no financial interests in the commerical products discussed in this publication.

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Cataract Surgery for Greenhorns

Ophthalmology Competencies: ACGME Competencies

VIDEO: Adjusting Chair Height

VIDEO: Using the microscope foot pedal for cataract surgery.

References

Chapter 6- Approaching Different Kinds of Cataract

Ectopia lentis

Intumescent Cortical Cataract

Hypermature Cataract

Morgagnian Cataract

Anterior Polar Cataracts

Posterior Polar Cataracts

Perforating and penetrating injury of the lens

Diabetes mellitus and cataract formation

Cataract Associated with Uveitis

Exfoliation Syndrome (Pseudoexfoliation)

Conclusion

Chapter 5 - Managing Surgical Complications

Vitreous Prolapse

Causes of Vitreous Prolapse

Signs of Vitreous Prolapse

Basic Principles of Vitrectomy

Vitreous Presenting early in case - while most of crystalline lens is in eye

Vitreous Presenting Mid-Case - while removing cortical material

How to deal with Vitreous Presenting late in the case - while placing IOL

Staining the Vitreous with Kenalog [view video]

Chapter 4- Post-Operative Care

Phacoemulsification

ECCE or ICCE

Chapter 3 - Staining the Lens Capsule

Indocyanine Green (ICG)

Trypan Blue (Vision Blue)

Surgical Technique for either stain

Chapter 3 - ophthalmic viscoelastic devices (OVD)

Different jobs demand different OVDs

Adaptive OVD

Arshinoff Shell

Chapter 3 - Phaco Machine Settings Primer

Four main components and software to tie them together

Phaco Pumps

Ultrasound Control

My Typical Settings

Chapter 3 - Phacoemulsification Step-by-Step

Chapter 3 - Old School

Chapter 3 - Anesthesia

Table of Contents

Chapter 2 - Operating Microscope Basics

Chapter 2 - Selecting the Intraocular Lens

Chapter 2 Preoperative Preparation - Consent

Chapter 1 Assessment - Difficulty Factors

Chapter 1 Assessment - Evaluation of Patients with Cataract

Chapter 1 Assessment - Types of Cataracts

TITLE PAGE

Staining the Vitreous with Kenalog
[view video]