Rates of glaucomatous visual field change before and after transscleral cyclophotocoagulation: a retrospective case series

BACKGROUND The primary goal of glaucoma treatment is to lower and control intraocular pressure (IOP) and thereby prevent functional deterioration. For glaucomas that are refractory to medical and incisional surgical therapies, transscleral diode cyclophotocoagulation (TCP) is a well-established procedure to effectively decrease IOP. This study investigated rates of visual field (VF) change in patients with glaucoma before and after TCP. METHODS This retrospective case series investigated rates of VF changes in glaucoma patients before and after they underwent TCP. At least four VF examinations were required, two before and two after surgery. VF examinations were performed using standard automated perimetry and rates of change were calculated by linear regression analysis of mean deviation (MD) values measured over time. RESULTS A total of 46 eyes of 43 patients were included and followed on average 3.6 years before and 2.1 years after TCP. 67 % of the eyes showed further progression of glaucoma following surgery. Mean preoperative MD change was -0.21 dB/year (SE = 0.08, 95 % CI [-0.06, -0.37]). Postoperatively the mean change was -0.26 dB/year (SE = 0.22 95 % CI [0.38, -0.48]) which results in a difference between pre- and postoperative MD rate of 0.05 dB/year (p = 0.824). The mean MD value was worse after surgery and dropped by 1.73 dB (SE = 0.58, 95 % CI [-0.59, -2.87], p = 0.003). Intraocular pressure (IOP) decreased from 23.2 mmHg (SD = 4.67) before TCP to 14.3 mmHg (SD = 3.17) after TCP (p < 0.001). For each 1 mmHg of IOP reduction after surgery, postoperative rate of VF loss decreased by 0.15 dB/year. CONCLUSION Rates of glaucomatous visual field loss did not significantly change after TCP and the majority of the eyes showed further progression of glaucoma after surgery. Mean MD value was considerably lower after TCP.