1. Assessment of Anterior Segment Measurements with Swept Source Anterior Segment OCT Before and After Trabectome Surgery Handan Akil, Mayss Al-Sheikh, SriniVas R. Sadda, Brian Francis, Vikas Chopra Doheny Eye Institute, Los Angeles, CA Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, CA Purpose To investigate the changes in anterior segment parameters, as assessed by swept source anterior segment optical coherence tomography (AS-OCT) after Trabectome surgery in patients with open angle glaucoma. Methods Thirty-eight eyes with open angle glaucoma were scanned with swept source AS-OCT (SS-1000 CASIA; Tomey Co. Ltd. Nagoya, Japan) before and 4 weeks after undergoing either combined Trabectome cataract or Trabectome only surgery. The same surgeon (BF) performed the ab interno trabeculotomy on all eyes, using the Trabectome first and then performing phacoemulsification, if indicated, according to the surgical technique described in previous studies. Twenty eyes underwent combined Trabectome surgery and 18 eyes underwent Trabectome only surgery. Images were analyzed with the angle assessment program of the machine itself (Casia software). After the scleral spurs were identified, the software calculated various parameters of the iris, cornea, and lens using automated identification of the anterior and posterior surfaces of the cornea, the iris and the anterior surface of the lens. We were also able to measure the length of the trabecular cleft with the same software in manual mode. The analysis incorporated the anterior chamber parameters by swept source AS-OCT, angle opening distance at 500-750 mm (AOD 500/750), trabecular- iris space area at 500-750 mm (TISA 500/750), angle recess area at 500-750 mm (ARA500/750), trabecular iris angle (TIA 500/750) at surgical quadrants and anterior chamber volume (ACV), anterior chamber width (ACW: from recess to recess), and trabecular cleft length. Results The mean age was 76.32±9.9 years in the combined Trabectome cataract surgery group (male: 11 eyes, female: 9 eyes) and 72.5 ± 7 years in Trabectome only group (male: 8 eyes, female: 10 eyes). At 1 month after surgery, the mean preoperative intraocular pressure (IOP) of 24.2 ± 4.7 mm Hg in the Trabectome only group was reduced by 40% to 14.6 ± 3.2 mm, while the mean preoperative IOP of 25.3 ± 6.4 mm Hg in the combined Trabectome cataract surgery group was reduced by 44% to 14.2 ± 2.8 mm Hg. Conclusions Anterior chamber angle parameters measured with swept source AS-OCT may be useful for evaluating longitudinal changes in glaucoma patients before and after various interventions, in order to evaluate their relationship to other metrics of glaucoma progression. Poster #5128 - C0143, Session #448 Disclosures: Dr. Brian Francis (Allergan (F), Innfocus (F), Lumenis (F), Aquesys (F), BVI Endooptiks (C)); Dr. SiriniVas Sadda (Carl Zeiss Meditec (C,F), OptoVue (F), Optos (C,F), Allergan (C,F), Genentech (C,F)); Dr. Vikas Chopra (Allergan (F)) Figure 1. A cross-sectional OCT image of the nasal angle after combined Trabectome cataract surgery. This frame- averaged image shows that the posterior trabecular meshwork has been removed, leaving a wide trabecular cleft. Figure 2. A cross-sectional OCT image of the nasal angle after Trabectome only surgery. This frame-averaged image shows that the posterior trabecular meshwork has been removed. Medications decreased by 32%, from 2.6 ± 1.2 to 1.7 ± 1.2, in the combined Trabectome group and by 28%, from 2.9± 1.2 to 2.1 ± 1.5, in the Trabectome only group. There was no statistically significant difference between preoperative and postoperative measurements of anterior chamber parameters (p>0.05) in the Trabectome only group. The ACD, ACV and all the angle parameters such as AOD 500/750, TISA 500/750, ARA 500/750 and TIA500 in the combined Trabectome surgery group were significantly different from their preoperative values (p < 0.05). The ACD and TIA500 values showed significantly greater changes from the preoperative values to postoperative first month values in combined Trabectome cataract surgery group compared to the Trabectome only group (p < 0.001) whereas the ACW value was not significantly different (Figure 1-2). There was no statistically significant difference between the two groups for the length of the trabecular cleft (p=0.7). Acknowledgements