Non-retinovascular leakage in diabetic maculopathy

Diabetic macular oedema is the leading cause of vision deterioration in diabetic retinopathy. Extracellular fluid within the retina, which distorts the retinal architecture, was assumed to be strictly of retinal vasculature origin. However, there is some experimental evidence supporting clinical observations suggesting a possible role of the retinal pigment epithelium (RPE). An unusual form of diabetic maculopathy is presented in which the RPE and the subretinal space play the main role.

Fluorescein angiograms of 1850 non-proliferative diabetic retinopathy (NPDR) patients were examined. Nineteen eyes (14 patients, 1% of NPDR patients) met the criteria-mainly having minimal diabetic retinopathy with only a few microaneurysms and no clinically significant macular oedema (CSMO). Early phase angiograms were compared with late phase angiograms.

It was found that in all 19 eyes the area of diffuse RPE late phase leakage was spread around the macular area. No cystic changes or cystoid macular oedema were present in any of the eyes and the visual acuity was 6/10 or better in all the eyes.

Possible changes occur in the RPE that may be responsible for the late leakage in NPDR patients-namely, diabetic retinal pigment epitheliopathy. These changes are associated with a breakdown of the outer blood-retinal barrier, consisting of leakage through RPE cells. No focal or diffuse leakage across the RPE has been reported in the literature related to the fluorescein angiograms in diffuse diabetic maculopathy.