Tuesday, December 12, 2006

Section 9-B: Risk Factors for acute angle closure glaucoma

There is variation in the size of the human eye. Some individuals have eyes that are slightly smaller than the average. In such smaller eyes, there is relatively less space for the normal structures of the eye (ciliary body, lens, and iris) and consequently, these eyes have “crowded” drainage angle. The result is narrower drainage angles with less space between the lens and iris and higher risk for pupillary block and acute closure of the drainage angle (Figure 9-1). The drainage angles of smaller eyes are therefore at higher risk of becoming critically narrow or closed. Consequently, acute angle closure glaucoma occurs most commonly in people with traits that are associated with smaller eyes (Table 9-2).

Table 9-2. Risk factors for acute angle closure glaucoma.
Female gender
Older age
Large natural lens (cataract)
Far-sightedness (Hyperopia)
Short axial length of the eye
Dim illumination
Certain medications

Acute angle closure glaucoma is more common in females because females have eyes that are generally smaller than those of males. Similarly, angle closure glaucoma occurs more frequently with increased age, because as the lens of the eye grows larger with age, the anterior segment of the eye becomes more crowded and the drainage angle becomes narrower. People with eyes that are physically smaller are generally far-sighted (hyperopic) and require more corrective power for seeing nearby objects than faraway objects. Such far-sighted individuals are at greater risk for acute angle closure glaucoma, because the drainage angle in their smaller eyes is more crowded than in individuals with normal sized eyes.

The risk for pupillary block and angle closure is increased when the pupil is dilated by dim illumination or by medication. As the pupil gets bigger, the bulk of the iris moves towards the angle causing it to become more crowded and narrower. Dilation of the pupils can cause narrow angles in susceptible individuals to become abruptly closed.

When critically narrow angles are observed by an eye doctor, preventative laser surgery (laser peripheral iridotomy) is recommended to reduce the risk of angle closure glaucoma occurring (see Section 9-D).


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