Glaucoma specialists are beginning to realize that much of the conventional wisdom surrounding angle-closure glaucoma is incorrect.
San Francisco-Glaucoma specialists are beginning to realize that much of the conventional wisdom surrounding angle-closure glaucoma is incorrect. Additionally, new risk factors must be identified and better methods for diagnosing and managing this condition also must be established, said Harry A. Quigley, MD.
"The point is that we have something we can understand if we try to work at it physiologically instead of simply measuring how big things are," said Dr. Quigley, the A. Edward Maumenee Professor of Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore.
"That's being done right now in two large longitudinal studies in China," he added. "We should look at the iris dilator's insertion by ultrasound biomicroscopy and see how that relates to mechanisms of the plateau iris eyes and make sure that we don't treat eyes with plateau iris configuration when they don't have continued disease.
"Finally, there would be ways in which we could think about and envision measuring choroidal expansion and provoking it on purpose in a controlled situation and replacing what are now ineffective provocative tests for angle closure with tests that actually tell us whom to treat," Dr. Quigley continued. "The stakes here are extremely high. In China, we're talking about the difference between treating 5 million people and 50 million people."
Dr. Quigley expressed his points regarding angle-closure glaucoma in the Jackson Memorial Lecture during the opening session of the annual meeting of the American Academy of Ophthalmology (AAO). The lecture is named after Edward Jackson, MD, founder of both the AAO and the American Journal of Ophthalmology.
Diagnostic tools that can determine accurately who will develop the disease and which individuals should be monitored but not treated are badly needed, as neither gonioscopy nor ultrasonic biomicroscopy can provide the answer, he added.
Understanding behavior of the eye
He recommended using technology, such as anterior segment optical coherence tomography, to increase understanding of the eye's behavior.
"By looking at anatomy alone, by measuring the size of things, we didn't learn enough about angle closure," Dr. Quigley said. "We have to begin thinking about the dynamic processes in the eye."
With new technology, physicians also can quantify the cross-sectional area of the iris and estimate its volume. Experiments that Dr. Quigley and colleagues have performed under various lighting conditions have demonstrated a strong and consistent relationship in which the iris loses substantial volume when the pupil dilates. Most eyes with angle-closure glaucoma have less change, and this risk factor is statistically provable, he said.
The iris attachment also may affect development of open-angle glaucoma. In some eyes, the attachment of the iris dilator is substantially inside the eye, forming the basis for plateau iris. When the ciliary epithelial connection to the iris dilator happens far into the eye, the articulated connection of the iris to the eye wall takes on a different structure, Dr. Quigley said.
In eyes in which the iris is connected far out toward the cornea, the peripheral iris looks fairly straight, and following iridotomy, most of these eyes will fall open. When the attachment is more centrally located and the connection is more complex, the eye still looks narrow after iridotomy, but the vast majority will not continue to have angle closure or suffer acute attacks, he added.
"In all probability when longitudinal studies are done, we'll find that these eyes are cured of their basic primary angle closure tendency," Dr. Quigley said. "To do iridoplasty on them is probably unnecessary, and we need serious studies looking into the natural history of these eyes with this plateau configuration to tell us which of them should receive iridoplasty, a fairly damaging treatment to the eye."
Poor vitreous fluid conductivity along with choroidal expansion and iris sponginess each represent additional physiologic factors that could be tested as risk factors for angle-closure glaucoma.