Retinal fixation impairment in diabetic macular edema

PURPOSE: To evaluate the characteristics of retinal fixation in patients with diabetic macular edema using microperimetry. METHODS: One hundred seventy nine eyes (98 patients) with untreated diabetic macular edema underwent best corrected visual acuity determination (Early Treatment Diabetic Retinopathy Study charts), digital color stereoscopic fundus photos, fluorescein angiography and Optical Coherence Tomography assessment of macula. Fixation and retinal thresholds were determined with an automatic microperimeter. RESULTS: Best corrected visual acuity (approximate Snellen equivalent) was: 20/25 or better in 90 (52%) eyes, 20/50 to 20/32 in 39 (22.5%) eyes, 20/200 to 20/62.5 in 35 (20.2%) eyes and inferior to 20/200 in 9 (5.2%) eyes. Fixation was central in 128(71.51%), poor central in 26(14.53%) and predominantly eccentric in 25(13.97%) eyes; stable in 133(74.3%), relatively unstable in 42(23.46%) and unstable in 4(2.23%) eyes. Both fixation location and stability were not significantly influenced by edema characteristics (diffuse, focal, cystoid, spongelike, with or without subfoveal neuroretinal detachment), (P > 0.05), whereas they were significantly influenced by the presence of subfoveal hard exudates, (P = 0.004 and P = 0.0046, respectively). Site and stability of fixation were significantly associated, (P < 0.0001). Retinal pseudofovea would have been covered by laser photocoagulation in 24(47%) eyes with poorly central and predominantly eccentric fixation and in 29(63%) eyes with relatively unstable and unstable fixation. CONCLUSION: Microperimetry shows that fixation location and stability in patients with diabetic macular edema are independent of edema characteristics, except when subfoveal hard exudates are present. Location of pseudofovea may influence treatment strategy.