Abstract
Purpose:
To provide a preliminary evaluation of abnormalities in total retinal thickness (TRT), photoreceptor cell outer segment thickness (OST), and photoreceptor inner segment ellipsoid (ISE) light reflectance in diabetic subjects with minimal or no retinopathy using spectral domain optical coherence tomography (SD-OCT).
Methods:
SD-OCT imaging of the macula was performed in one eye of 5 diabetic subjects (ages 25 - 64 years) and 5 healthy control subjects (ages 31 - 56 years). Six radial B-scans arranged according to the clock hours and centered on the fovea were obtained using a commercially available instrument (Optos). A customized automated software algorithm (Matlab) was utilized to segment the images and provide metrics of TRT, OST, and the ratio of ISE intensity to retinal pigment epithelium (RPE) intensity (ISE/RPE intensity). Measurements were made using a grid composed of 40 points arranged in four concentric rings (1°, 3°, 6°, and 12° radii) centered at the fovea. The central ring was composed of 4 points and the more peripheral rings were composed of 12 points, arranged according to the clock hours. Measurements within rings were averaged for each subject. To determine the effects of diabetes and retinal eccentricity on these metrics, a two-way analysis of variance was performed. Linear regression analysis was used to describe the relationship between ISE/RPE intensity and OST.
Results:
TRT and OST were significantly lower in diabetic subjects as compared to controls (p = 0.006 and p < 0.001, respectively). In diabetic and control subjects, OST progressively decreased as retinal eccentricity increased. ISE/RPE intensity was significantly lower in the diabetics, compared to the controls (p = 0.03) and decreased significantly with increasing eccentricity (p = 0.02). A linear relationship between ISE/RPE intensity and OST (R = 0.38, p = 0.016, N = 40) was observed, indicating that reduced ISE light reflectance was associated with OST.
Conclusions:
In our sample of diabetic subjects with minimal or no retinopathy, structural changes of the retina were observed including reduced total retinal thickness, photoreceptor outer segment thickness, and ISE light reflectance compared to healthy controls. These preliminary results suggest that outer retina abnormalities in diabetic subjects may precede clinically-apparent signs of retinopathy.
Keywords: 499 diabetic retinopathy •
550 imaging/image analysis: clinical •
552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)