Choroidal thickness in patients with diabetic retinopathy analyzed by spectral-domain optical coherence tomography

Abstract

Purpose: This study was designed to examine choroidal thickness in patients with diabetes using spectral-domain optical coherence tomography.

Methods: Forty-nine patients (49 eyes) with diabetes and 24 age-matched normal subjects underwent high-definition raster scanning using spectral-domain optical coherence tomography with frame enhancement software. Patients with diabetes were classified into 3 groups: 11 patients with mild or moderate nonproliferative diabetic retinopathy and no macular edema, 18 patients with nonproliferative diabetic retinopathy and diabetic macular edema, and 20 patients with treated proliferative diabetic retinopathy and no diabetic macular edema (treated proliferative diabetic retinopathy). Choroidal thickness was measured from the posterior edge of the retinal pigment epithelium to the choroid/sclera junction at 500-μm intervals up to 2,500 μm temporal and nasal to the fovea.

Results: Reliable measurements of choroidal thickness were obtainable in 75.3% of eyes examined. Mean choroidal thickness showed a pattern of thinnest choroid nasally, thickening in the subfoveal region, and thinning again temporally in normal subjects and patients with diabetes. Mean subfoveal choroidal thickness was thinner in patients with diabetic macular edema (63.3 μm, 27.2%, P < 0.05) or treated proliferative diabetic retinopathy (69.6 μm, 30.0%, P < 0.01), compared with normal subjects. There was no difference between nonproliferative diabetic retinopathy and normal subjects.

Conclusion: Choroidal thickness is altered in diabetes and may be related to the severity of retinopathy. Presence of diabetic macular edema is associated with a significant decrease in the choroidal thickness.

Fig. 1

Graph of mean CT in normal subjects and diabetic patients. Mean CT at each of the 11 locations measured at 500-μm (0.5 mm) intervals temporal (T) and nasal (N). P value represents the result of statistical analyses (analysis of variance).

Fig. 2

Representative scans with CT measurements on Cirrus HD-OCT high-definition 1-line raster scans. Perpendicular lines were drawn from posterior edge of RPE to choroid/sclera junction using Cirrus HD-OCT software. Choroidal thickness was measured in the fovea and at 500-μm intervals nasal and temporal to the fovea with the measurements expressed as micrometers (red lines). Note that the choroid is thickest at center, thinner temporally, and thinnest nasally. A. Representative scan from a normal subject; (B) representative scan from a patient with mild non-proliferative diabetic retinopathy; (C) representative scan from a patient with moderate nonproliferative diabetic retinopathy and diabetic macular edema; (D) representative scan from a patient with treated proliferative diabetic retinopathy, note that there is a disruption in the photoreceptor inner/outer segment junction probably because of the retinal ischemia.

Fig. 3

Graph of mean subfoveal CT in normal subjects and diabetic patients. P values represent the results of posttest comparison with Tukey multiple test.