Evaluation of macular and choroidal thickness in diabetic patients without diabetic retinopathy

Purpose
To compare macular and choroidal thickness in diabetic and healthy eyes using optical coherence tomography angiography.

Material and methods
Sixty-five eyes of 33 patients with type 2 diabetes, without clinically evident diabetic retinopathy and without diabetic macular edema and 34 eyes of 32 healthy volunteers were enrolled in the prospective study. Optical coherence tomography angiography of the retina was performed in all subjects. Retinal thickness in the foveal and parafoveal region was determined based on Retina Map scans. Choroidal thickness was measured manually on horizontal spectral optical coherence tomography scans acquired with AngioVue SOCT in Enhanced HD line mode. Measurements were performed at the foveola, as well as 1.5 mm nasally and 1.5 mm temporally from the site of the first measurement.

Results
There was no difference in the foveal retinal thickness, foveal retinal volume, parafoveal retinal thickness and parafoveal retinal volume between diabetic subjects and healthy controls. In diabetic patients, the mean choroidal thickness at the fovea and at the nasal and temporal parafoveal areas were significantly lower as compared to healthy volunteers.

Conclusions
Diabetic patients without clinically manifest diabetic retinopathy have a significantly thinner choroid at the fovea and parafoveal area than healthy volunteers. There is no difference in the mean retinal thickness at the fovea and parafovea, as well as in the mean retinal volume both at the fovea and parafovea between diabetic and healthy eyes. Enhanced depth optical coherence tomography is a useful tool which can be used for non-invasive evaluation of the retinal and choroidal structure, thickness and volume.