Macular Inner Retinal Layer Thinning in Diabetic Patients Without Retinopathy Measured by Fourier Domain Optical Coherence Tomography

Abstract

Purpose: : Diabetes may lead to ischemia and retinal tissue injury even in early stages of diabetic retinopathy. We aimed to compare values of macular inner retinal layer (MIRL) thickness obtained by a Fourier Domain Optical Coherence Tomography (FD-OCT) device between diabetic patients without retinopathy and healthy subjects.

Methods: : We prospectively enrolled 26 type-II diabetic patients without clinical signs of retinopathy and 27 healthy subjects. Patients with other ocular or systemic diseases were excluded. All patients underwent MIRL thickness measurement by FD-OCT (7x7 mm macular grid; RTVue). The macular inner retinal layer thickness is provided by the Ganglion Cell Complex scan (comprised by the retinal nerve fiber, ganglion cell and inner plexiform layers). If both eyes were eligible, one was randomly selected.

Results: : Mean age was similar between diabetic (53.6±12.3 years) and non-diabetic patients (59.2±11.5 years; p=0.12). There were no significant differences regarding optic disc area and cup-to-disc ratio between groups (p>0.08). Average MIRL was significantly thinner in diabetic patients compared to controls (91.8 vs 96.2 µm; p=0.04). Regional analysis revealed superior MIRL to be significantly thinner in diabetic patients than controls (p=0.04). No difference was found when considering inferior MIRL values (p=0.08). In 75% of the diabetic eyes classified as abnormal (p<1%) by the device software, the juxtafoveal area was the affected (thinned) one.

Conclusions: : Diabetic patients without retinopathy have reduced average MIRL values when compared to normal subjects. This difference seems to be more pronounced in the superior macula, mainly juxtafoveally. Possible implications of these findings require further investigation.

Keywords: diabetes • ganglion cells • imaging/image analysis: clinical