Angle closure involves interplay of multiple anatomical, physiological factors

HYDERABAD, India — New imaging technologies have enabled specialists to determine that an interplay of multiple anatomical and physiological factors are involved in the pathogenesis of angle closure.

“We have been able to learn quite a lot on angle closure by using imaging technologies, particularly [ultrasound biomicroscopy] and anterior-segment [optical coherence tomography]. We are studying new risk factors such as iris thickness, smaller anterior chamber width area and volume, and greater lens vault,” Tin Aung, MD, said at the joint meeting of the Asia-Pacific Academy of Ophthalmology and All India Ophthalmological Society.

Tin Aung

Besides the well-known mechanisms such as pupil block and plateau iris, there are other mechanisms that play a role in angle closure, Aung said. Uveal effusion was found to be present in a high percentage of eyes with angle closure.

“We don’t know yet if uveal effusion, which disappears with [laser peripheral iridotomy], is the result or a contributing factor of the angle closure process,” Aung said.

Dynamic factors are also involved. Eyes with angle closure were found to retain more iris volume with pupil dilation and to have a slower speed of pupil constriction in response to a change from darkness to light.

“Iris dynamics may be a contributing factor to angle closure,” Aung said.

The Valsalva maneuver, frequently performed in daily activities, may also increase the risk of acute angle closure in predisposed eyes.

“It narrows the angle, makes the anterior chamber shallower and the iris thicker, as well as increasing IOP,” Aung said.

Angle closure is not a homogeneous disease, and these factors may contribute in various proportions in different cases, he said.

Disclosure: Aung has no relevant financial disclosures.