Evaluation of Anterior Segment Changes Following Laser Peripheral Iridotomy Using Pentacam Scheimpflug Imaging System in Eyes with Primary Angle Closure (PAC)

Primary angle-closure glaucoma (PACG) is a major form of glaucoma in Asia. It is a leading cause of blindness worldwide. Laser peripheral iridotomy (LPI) is the standard firstline intervention in both acute and chronic forms. It is successful in preventing recurrence of acute attacks and virtually eliminates the risk of an acute attack in the fellow eye. Peripheral iridotomy eliminates pupillary block, allowing the convex iris to flatten and widening the anterior chamber angle (Figure 1). Such changes in anterior chamber angle morphology are difficult to assess. Gonioscopy is difficult to perform in a reproducible fashion, limiting the ability to quantify changes after LPI. Ultrasound biomicroscopy (UBM) gives reproducible images of the cross-sectional anterior chamber angle anatomy, with very high resolution. The OCULUS Pentacam is a rotating Scheimpflug camera that non invasively assesses the anterior segment of the eye. It takes about 2 seconds to generate an image of the anterior eye. The Pentacam instrument acquires Scheimpflug cross sectional images of the anterior segment. Information from 25,000 data points is used to calculate corneal thickness, corneal curvature, anterior chamber angle, volume, and depth, from the height data it generates from the imaged points. This gives reproducible information for anterior chamber biometry. In this study, we aimed to know the effects of peripheral laser peripheral iridotomy (LPI) on peripheral anterior chamber depth (PACD), central internal anterior chamber depth (ACD) and anterior chamber volume (ACV) using Pentacam. This is the only instrument which is giving a quantitative estimation of anterior chamber volume.