Photoreceptor function in eyes with macular edema

PURPOSE. The irreversible loss of visual acuity in macular edema is usually attributed to permanent loss of photoreceptor cells, although there is har dly any information on changes in photoreceptor function in macular edema. The purpose of this study was to assess photoreceptor function in various s tages of macular edema and to relate the findings to visual acuity and angi ographic changes. METHODS, Directional sensitivity (optical Stiles-Crawford effect) and visua l pigment density of foveal cones was measured with a custom-built scanning laser ophthalmoscope (SLO) in 19 eyes of 19 patients. Twelve eyes exhibite d macular edema: five of inflammatory origin, and seven of diabetic origin. Seven eyes with an intraocular inflammatory disease without clinical or an giographic evidence of edema were also included (four of which had previous macular edema and one of which had shown development of macular edema at t he 1-year follow-up). Results of SLO measurements were related to findings using fluorescein angiography and Snellen visual acuity, both assessed at t he time of SLO measurement and 6 months thereafter. RESULTS. Eyes with macular edema exhibited diminished directional sensitivi ty of photoreceptor cells in the fovea compared with eyes without (P = 0.02 ). Visual pigment density of eyes with macular edema was decreased and asso ciated with both initial and follow-up visual function and with the angiogr aphic macular edema grade at follow-up. Abnormal directional sensitivity an d pigment density were already present in eyes with slight edematous change s and normal visual acuity. CONCLUSIONS. Eyes with inflammatory or diabetic macular edema showed decrea sed directional sensitivity and visual pigment density in the macular area. These findings may support a role for SLO measurements in detecting retina l damage due to macular edema.