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S. C. Reddy, K. Boyd, H. Cho, A. Shrivastava; Evaluation of Anterior Segment Morphology After Laser Peripheral Iridotomy Using Cirrus HD-OCT in a Bronx Population. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5536.
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To quantify the postoperative changes in the anterior chamber angle and anterior chamber depth (ACD) after peripheral laser peripheral iridotomy (LPI) utilizing Cirrus HD-OCT in patients being treated for narrow anatomic angles in a Bronx population.
This is a prospective study of 20 eyes with narrow anatomic angles, necessitating LPI in a tertiary referral practice in the Bronx, NY. Twenty eyes of 19 phakic patients undergoing LPI were imaged utilizing a 5-line raster anterior segment OCT protocol, 10-15 minutes after instillation of one drop of pilocarpine 2% and iopidine 0.5%. Scans were performed by a single skilled operator in the superotemporal quadrant of the operative eye (approximately 11 o’clock OD; 1 o’clock OS). LPI was performed by one attending physician utilizing a combined argon and ND:Yag laser technique in the superotemporal quadrant. The treated eye was re-imaged in the region of the LPI, with visualization of the iridotomy. ACD was calculated utilizing the Cirrus HD-OCT measuring tool from the LPI site to the corneal endothelium on the post-treatment scan. Using anatomic landmarks, the site of LPI was extrapolated in the pre-treatment images, and ACD was calculated. Additionally, the angle was manually quantified utilizing the following technique: hard copies of the scans were obtained, and a line extended from the anterior iris surface towards the angle. A second line was drawn from the corneal endothelium. The angle subtended by the intersection of these two lines was measured, serving as an approximation of the anterior chamber angle in degrees. Statistical analysis was conducted to detect a difference between pre- and post-treatment ACD and angle measurement.
Mean ACD before laser was 394.3 um and 686.6 um after laser. Paired t-test showed a significant difference in ACD pre- and post-laser (P<0.001). Mean angle measurement was 14.3 degrees before and 25.2 degrees after LPI, which was a significant difference (P<0.001).
The Cirrus HD-OCT 5-line raster scan can resolve changes in angle morphology after LPI in our population, and can quantify the immediate postoperative effects on the anterior segment. Further study will be performed to determine if these extremely significant changes are maintained after the immediate postoperative period. The use of OCT technology has substantially improved our ability to identify patients with pathology, and will continue to serve as a useful tool in their management.
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