Serial Evaluation of Pectinate Ligament Morphology Is Not Useful in Predicting the Onset of Intraocular Pressure Elevation in Dogs With Primary Angle Closure Glaucoma.

Objective: To determine whether serial evaluation of pectinate ligament morphology could aid in predicting the onset of elevated intraocular pressure (IOP) in eyes predisposed to primary angle closure glaucoma (PACG).

Animals studied: The second eye of dogs affected with PACG (20) that had already developed elevated IOP in the first eye and normal dogs (12) with no history of glaucoma.

Procedures: Serial goniophotographs of all quadrants of the iridocorneal angle were obtained every 9 months over approximately 18 months in normal dogs. Images were obtained every 3 months in dogs with PACG until that eye developed elevated IOP. A modified ZibWest score was calculated for each image. The earliest ZibWest score was then compared with the last ZibWest score for each eye. Additionally, matched images from the same quadrant from the first and last time point were presented to masked experienced evaluators to see whether the progression of abnormalities could be detected.

Results: A difference in ZibWest scores between the first and the last time point for each eye was not detected across all dogs (p = 0.3673), within dogs affected with PACG (p = 0.2665), or normal dogs (p = 0.3953). Experienced evaluators were unable to detect significant progression of pectinate ligament abnormalities.

Conclusions: Serial gonioscopic evaluation of pectinate ligament morphology does not appear to be useful in the prediction of the time of onset of elevated IOP in dogs with PACG.