Author(s): Chitra Munusamy Rajendran, Anjana Ramanathan
BACKGROUND Glaucoma is a chronic progressive optic neuropathy characterised by optic nerve head changes and field defects due to apoptosis of ganglion cells, with raised intraocular pressure being the most important risk factor. Traditionally Armaly’s cup/disc (C/D) ratio was considered as a standard method of evaluation of optic nerve head. The Disc Damage Likelihood Scale DDLS relies on the optic nerve as a direct indicator of disease. Because the scale divides glaucomatous progression into 10 stages, it can also aid to monitor the disease progression. DDLS helps in quantification of the amount of damage that the optic nerve has sustained. This study correlates the DDLS score with the visual field indices establishing a structural and functional correlation. We wanted to analyse Disc Damage Likelihood Ratio in patients with established open angle glaucoma and to correlate it with field defects and to thereby obtain an anatomical versus functional correlation. This study also evaluates the diagnostic ability of disc damage likelihood scale in glaucoma. METHODS 50 cases of established open angle glaucoma were included in this study. For all cases visual fields were recorded by Octopus 301 using G1 program and TOP strategy. After field testing, DDLS scores were calculated after dilatation. The DDLS score and field parameters of the patients were analysed. RESULTS Of the 50 patients included in this study, 70% were on topical antiglaucoma medications and 30% had undergone trabeculectomy. DDLS score and average loss variance showed a strong positive correlation as the r value was 0.95. CONCLUSIONS Disc diameter evaluation is an important part of optic nerve head evaluation. In cases with asymmetry of the cup disc ratio between two eyes, asymmetry of the disc size should also be considered if the neuroretinal rim is healthy. Disc Damage Likelihood Scale (DDLS) is a better indicator of optic nerve head status and has strong positive correlation with visual field indices.