Tuesday, October 04, 2005

References

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]


[PREVIOUS]

Sunday, October 02, 2005

Chapter 6- Approaching Different Kinds of Cataract

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

      1. Attend to any vitreous in anterior chamber – staining with Kenalog helps to visualize the clear vitreous [view video]
      2. Use iris hook to stabilize anterior lens capsule
      3. Capsular tension ring (CTR) with or without Cionni modification
      4. IOL in bag – mild cases aided by CTR/Cionni ring
      5. Iris fixated posterior or anterior IOL
      6. Angle supported IOL
      7. Sulcus sutured posterior chamber IOL
      8. 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

[PREVIOUS] [REFERENCES]

Chapter 5 - Managing Surgical Complications

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

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


[PREVIOUS] [NEXT]

Chapter 4- Post-Operative Care

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):

  1. pull a stitch (i.e. cylinders at axis of stitch is greater than 2 D on MR)
  2. give glasses (i.e. no stitch to pull or cylinder is less than 2 D on MR)
  3. 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


[PREVIOUS] [NEXT]

Chapter 3 - Staining the Lens Capsule

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)


[PREVIOUS] [NEXT]

Chapter 3 - ophthalmic viscoelastic devices (OVD)

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



[PREVIOUS] [NEXT]

Saturday, October 01, 2005

Chapter 3 - Phaco Machine Settings Primer


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)
  1. 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




  2. 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]


[PREVIOUS] [NEXT]

Chapter 3 - Phacoemulsification Step-by-Step

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



  1. 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.


  2. 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.


  3. 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].


  4. Place ophthalmic viscoelastic device (OVD) into anterior chamber. One method is the Arshinoff shell technique: 1st 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.


  5. 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




  6. 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.




  7. 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.


  8. 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:


    1. There are numerous ways to disassemble a lens nucleus:

  9. 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 ].

  10. 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.

  11. 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.

  12. 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. [click here for larger image]

    4. 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]

  13. 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


[PREVIOUS] [NEXT]