Tuesday, March 07, 2006

Section 2-C. Epidemiology of Primary Angle Closure Glaucoma

Primary angle-closure glaucoma (PACG) is usually associated with elevated intraocular pressure, optic nerve damage, and resultant visual loss. The aqueous fluid drainage angle becomes progressively narrower (usually with age) and eventually, the intraocular pressure increases as a result of decrease in aqueous fluid drainage.

Epidemiology of PACG is less studied than that of open angle glaucoma. However, it is no less important. In fact, PACG may account for 64% of all glaucomas in Mongolia, and 50% of all glaucomas worldwide. In the white, Hispanic, and black populations, angle-closure glaucoma is present in 0.1 - 0.6% of the older population (Table 2-3). However in Asian populations, angle-closure glaucoma is present in 0.3% (Japan) to 2.7% (Alaska) of the older population.

Table 2-3. Prevalence of angle closure glaucoma in different world populations

Race / Location

Prevalence of Angle Closure Glaucoma
in older age population (generally over age 40)

White populations (Europe, Australia)

0.1 – 0.6 %

Asian populations (Alaska, Japan, Mongolia, Singapore, India)

0.3 – 2.7 %

Hispanic population (US)

0.1 %

Black populations (Africa)

0.5 – 0.6 %




Blindness can occur in angle closure glaucoma as well. In fact, the rate of blindness from angle closure glaucoma may be even higher than that of open angle glaucoma. Blindness in one eye occurs in 10 –50% of Inuit and Chinese patients with angle closure glaucoma. In East Africa, blindness in both eyes occurs in 21% of angle-closure glaucoma patients.


Figure 2-1. A photograph of an eye in acute angle closure glaucoma. The eye is very red and the patient was in pain. The intraocular pressure was 62 mmHg (normal 10 - 21). Notice the bleeding spot at 1 o’clock (arrow) where laser iridotomy surgery was performed.

Figure 2-2. Slit lamp picture of an eye in acute angle closure glaucoma. Notice the drainage angle represented here by 2 intersecting lines is very narrow. The angle is also called “irido-corneal” angle because it is formed by the iris and cornea.




Because acute angle-closure glaucoma can be prevented with a laser surgery (see Figure 2-1, chapter 9 will cover this in more detail), there is a great interest in population screening for early detection of angle closure glaucoma. In reality however, screening for angle-closure glaucoma has been difficult. There are several methods for detection of narrow (or closed) drainage angle (Figure 2-2). Some are simple (for example, oblique flash light test), while others require special equipment (for example, Van Herick’s test utilizing the slit lamp instrument that most ophthalmologist use for examining the eye). Unfortunately, none of these methods meet all the criteria for effective mass screening, which requires quick, easy administration by minimally trained personnel at low cost. Studies are under way to look for most effective methods to screen for and prevent angle-closure glaucoma in high-risk Asian population. The population screening and preventive treatment of angle closure glaucoma is particularly important in Asian countries where the prevalence of angle closure glaucoma is relatively high. Such screening and preventive treatment of angle closure glaucoma can have major impact on public health in those populations.

References


  1. Allingham RR, Damji K, Freedman S, Moroi S, Shafranov G. Clinical Epidemiology of Glaucoma. In: Shield’s Textbook of Glaucoma. 5th Ed. Philadelphia: Lippincott Williams and Wilkins; 2005; p170-190.

  2. Kwon YH, Caprioli J: Primary Open Angle Glaucoma. In: Duane’s Clinical Ophthalmology, Tasman W, Jaeger EA, eds.; Philadelphia: J.B. Lippincott Co.; 1999;, Chapter 52:1-30.

  3. Kwon YH, Kim C, Zimmerman MB, Alward WLM, Hayreh SS. Rate of visual field loss and long-term visual outcome in primary open angle glaucoma. Am J Ophthalmol. 2001; 132(1): 47-56.

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