Background-Diabetic macular oedema is the leading cause of vision dete
rioration in diabetic retinopathy. Extracellular fluid within the reti
na, which distorts the retinal architecture, was assumed to be strictl
y of retinal vasculature origin. However, there is some experimental e
vidence supporting clinical observations suggesting a possible role of
the retinal pigment epithelium (RPE). An unusual form of diabetic mac
ulopathy is presented in which the RPE and the subretinal space play t
he main role. Methods-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 minim
al diabetic retinopathy with only a few microaneurysms and no clinical
ly significant macular oedema (CSMO). Early phase angiograms were comp
ared with late phase angiograms. Results-It was found that in all 19 e
yes the area of diffuse RPE late phase leakage was spread around the m
acular 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. Conclusions-Possible changes occur in the RPE that may be respo
nsible for the late leakage in NPDR patients - namely, diabetic retina
l pigment epitheliopathy. These changes are associated with a breakdow
n of the outer blood-retinal barrier, consisting of leakage through RP
E cells. No focal or diffuse leakage across the RPE has been reported
in the literature related to the fluorescein angiograms in diffuse dia
betic maculopathy.