Safety of medication reduction for Primary Angle Closure (PAC) – a longitudinal follow-up study Poemen PM Chan1,2, Vivian SM Chiu1, Gilda WK Lai1, Christopher SK Leung1,2 1. Department of Ophthalmology & Visual Science, Faculty of Medicine The Chinese University of Hong Kong 2. Hong Kong Eye Hospital, Hong Kong SAR. Purpose To investigate the safety of reducing medication use in primary angle closure (PAC) patients with intraocular pressure (IOP) of less than 30 mmHg. Methods Eyes with PAC is defined as IOP >21mmHg associated with non-visibility of trabecular meshwork (TM) for >180o – with or without the presence of PAS (hence, include both appositional and synechial closure). All eyes with PAC underwent peripheral laser iridotomy (PLI). IOP lowering agents were taken off from these patients. Baseline assessment included IOP measurement by Goldmann applanation tonometre, slit-lamp examination, indentation gonioscopy and ocular biometry. Patients were recruited for followed up if IOP>21mmHg without medication at baseline and without any functional or structural glaucomatous damage. Subjects were excluded at baseline assessment if they have (1) IOP >30mmHg, or (2) glaucomatous visual field defect. All patients were regularly followed up for at least 1 year. They would receive medications or further interventions if (1) IOP was >30mmHg, (2) confirmed glaucomatous VF defect, (3) confirmed structural optic disc damage on examinations with 90D lens or OCT, or (4) symptomatic such as eye pain or seeing halos. Results   Baseline 1 Year P value Age (years) 70±9 --- Sex (male:female) 7:25 Right:Left 29:28 Axial Length (μm) (range) 22.55±0.83 (20.83 to 24.55) Spherical equivalent refraction (diopter) (range) +0.89±1.66 (+4.75 to -3.50) IOP(mmHg)(range) 21.9±3.2 (16 to 30) 23.3±3.06 (18 to 31) 0.041 CCT (μm) 542.26±33.66 543.05±36.10 0.661 Average Shaffer Gonioscopy Grading† 1.45±0.89 1.58±0.94 0.097 Degree of PAS (o)† 211.98±114.73 198.40±121.64 0.146 Mean deviation (dB) 2.82±2.50 -2.31±1.90 0.564 Pattern standard deviation (dB) 2.23±1.22 2.11±0.94 0.755 Visual field index (%) 96.69±4.04% 95.29±15.39% 0.546 OCT average RNFL thickness (μm) 92.00±10.53 89.98±11.42 0.007 OCT Rim area (mm2) 1.23±0.22 1.23±0.24 0.600 OCT Disc Area (mm2) 2.03±0.36 2.03±0.37 0.500 OCT Cup volume (mm2) 0.22±0.18 0.666 OCT vertical CDR 0.55±0.13 0.375 OCT average CDR 0.60±013 0.60±0.13 0.126 Fifty-seven eyes with PAC of 32 patients were successfully recruited. They all had documented history of at least 180o of angle closure (Shaffer grading ≤1) before underwent PLI. They were followed-up every 6 month. The baseline demographics and one year outcomes are listed on table 1. There is no glaucoma progression according to the standard visual field criteria (a cluster of ≥3 non-edge points in the pattern standard deviation plot in a single hemifield with p <5%, one of which had p <1%). Although there is a decrease in MD (2.82 ±2.50dB at baseline to -2.31 ±1.90dB) at one year, there is no statistically significant changes of MD, PSD and VFI (p= 0.564, p=0.755 and 0.546 respectively). There is no changes of the OCT parameters apart from a decrease in the average RNFL thickness (92.00±10.53 to 89.98 ± 11.42; p=0.007) assessed by OCT ▲Table 1 Baseline demographic and outcomes after one year. *pair t test † gonioscopy after peripheral laser iridotomy A previous study has shown that moderate to low risk ocular hypertensive eyes could be safely followed-up without medication for one year.1 The current study showed that eyes with PAC within the IOP ranged of 21 to 30mmHg, could also be safely monitored without any intervention for at least one year. Longer follow-up with other technique (e.g. glaucoma progression analysis) are required to determine the clinical significance of the 2 μm thinning of the average RNFL. Conclusion References 1. Chan PP, Leung CK, Chiu V, Gangwani R, Sharma A, So S, Congdon N. Protocol-driven adjustment of ocular hypotensive medication in patients at low risk of conversion to glaucoma. Br J Ophthalmol. 2015 Sep:99(9):1245-50.