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Vandana R Minnal, Alice Chuang, Laura Baker, Lauren S Blieden, Nicholas P Bell, Robert M Feldman; Evaluating the effect of laser peripheral iridotomy on iridotrabecular contact in eyes with primary angle closure. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4837.
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© ARVO (1962-2015); The Authors (2016-present)
Primary angle closure glaucoma is a leading cause of bilateral blindness worldwide. These eyes often demonstrate iridotrabecular contact (ITC) on gonioscopic exam and on imaging with anterior segment optical coherence tomography (ASOCT). If untreated, areas of ITC might form peripheral anterior synechiae (PAS). Laser peripheral iridotomy (LPI) is the first-line treatment for this condition. The purpose of this study is to determine the extent of ITC using ASOCT before and after LPI in eyes with primary angle closure.
Eighteen eyes of 18 patients scheduled to undergo LPI were enrolled. This included 14 females and 4 males with an average age of 57.8 (+/- 10.4) years. Patients underwent slit lamp examination, gonioscopy, and ASOCT imaging using the CASIA SS-1000 (Tomey, Nagoya, Japan) at baseline and 3 months after LPI. Circumferentially, 128 2D images of each eye were obtained and analyzed. ITC was defined as iris touching any part of the trabecular meshwork (TM). The average extent of ITC at baseline, 3 months after LPI, and average difference were calculated.
Upon baseline gonioscopic examination, 8 patients were open to only Schwalbe’s line, and 10 were open to anterior TM. Nine patients had no PAS, and 8 had 1 to 7 clock hours of PAS. One patient had inadequate preoperative gonioscopy. Three months after LPI, all eyes were noted to have patent iridotomies, and on gonioscopy, 4 were open to scleral spur, 10 to posterior TM, 3 to anterior TM, and 1 to Schwalbe’s line. Seven patients had no PAS, and 11 had 1 to 7 clock hours of PAS. At baseline, ASOCT image analysis revealed an average of 246.09 (+/- 78.90) degrees of ITC, with a range of 79 to 360 degrees. Three months after LPI, the average extent of ITC was 183.44 degrees (+/- 98.19), with a range of 23 to 347 degrees. The average change was -62.66 degrees (+/- 91.93) with a range of -223 to +178, which was statistically significant (P=0.01).
This study demonstrates a significant reduction in the extent of ITC after LPI. It also demonstrates that the extent of ITC can be measured using the CASIA SS-1000 ASOCT.
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