Evaluation of Choroidal Thickness in Type 2 Diabetes Using Spectral-Domain Optical Coherence Tomography

Microvascular changes induced by diabetes mellitus (DM) are the primary cause of diabetic retinopathy (DR) and choroidopathy. There is a lack of evidence linking diabetic retinopathy (DR) to changes in choroidal thickness (CT), so we designed this study to investigate this relationship. The choroidal thickness of DM patients, with or without DR, was compared to that of controls (subjects without diabetes) using spectral domain optical coherence tomography (SD-OCT).

We recruited 132 participants for a prospective observational study. Choroidal thickness at five points: subfoveal and at 500 and 1000 µm, both temporally and nasally to the fovea, was measured. OCT measurements, insulin use, lipid profiles, age, gender, fundus examination, and glycaemic control were recorded. The inferential and descriptive statistics were applied.

When compared to DM patients without DR, CT showed a trend toward lower values; however, only CT at 1000 μm temporal to the fovea (300.25 ± 65.37 μm in control group 1, 304.82 ± 76.71 μm in group 2, and 271.84 ± 65.07 μm in DR group 3) reached statistical significance (p = 0.05). Each diabetic subgroup did not differ in sub-foveal choroidal thickness (SFCT) (p = 0.586). Patients without DME (289.53 ± 63.86 μm) and those with DME (289.83 ± 100.99 μm) had comparable SFCTs (p = 0.992).

When comparing diabetic patients with and without diabetic retinopathy to healthy controls, there are differences in CT (increased, decreased, or no change). The atrophy and dropout of the choriocapillaris in eyes with diabetic retinopathy may be the cause of the decrease in CT in DR patients that our study revealed.

DR patients showed a statistically significant decrease in CT at the 1000 μm temporal to fovea choroidal subregion compared to DM patients without DR. These results suggest that diabetes induces pathological changes in the choroid, resulting in retinopathy.