RETINAL THICKNESS VARIATION IN THE DIABETIC PATIENT MEASURED BY THE RETINAL THICKNESS ANALYZER

Aim-To evaluate the potential of the retinal thickness analyser (RTA) as an objective tool for assessment and follow up of diabetic macular oedema. Methods-A prototype of the RTA that operates on the principle of laser slit biomicroscopy was used. Retinal thickness was obtained i n 41 eyes of 41 diabetic patients. The clinical diagnosis was cystoid macular oedema (CMO) in 10 eyes, clinically significant macular oedema (CSMO) without retinal cysts in 21 eyes, and ''dry'' macula following grid pattern laser treatment in 10 eyes. The control group consisted of 46 eyes of age matched healthy volunteers. Results-In normal eyes ( 46 eyes), the foveal thickness measured was 178 (SD 44) Irm and the ma cular thickness around the fovea was 311 (51) mu m The eyes with CMO d isplayed the largest foveal thickening, 875 (287) mu m (390% increase compared with normal values). The average thickness of the fovea in th e non-cystoid CSMO group was 427 (175) mu m (144% increase compared wi th normal fovea). The average thickness of the foveal centre in eyes j udged as having ''dry'' macula after laser treatment was 315 (71) mu m (77% increase compared with normal value and a 26% decrease in thickn ess compared with the CSMO eyes). Statistically significant difference s were found in central thickness between these four groups (p = 0.000 1). The average thickness at 500 mu m surrounding the fovea was 566 (2 02) inn in the CSMO eyes compared with 311 (51) mu m in normal eyes (8 0% increase). The ''dry'' macula group (after undergoing laser treatme nts) had an average thickness of 414 (94) mu m (27% decrease compared with CSMO eyes and a 33% increase compared with eyes of healthy contro ls). Conclusions-RTA is a system for quantifying macular thickness and imaging of macular pathology. The system can be a useful tool for dia gnosis of macular diseases and for evaluation of the effect of treatme nt modalities.