Changes in Waveguiding Cone Photoreceptors and Color Vision in Patients With Diabetes Mellitus.

Purpose: Although it is well known that photoreceptor damage and color vision loss occur in patients with diabetic retinopathy (DR), the relationship between structural and functional changes in diabetes mellitus (DM) remains unclear. Using highly sensitive measures of photoreceptor structure and function, we aim to determine whether early loss of color sensitivity in DM is also accompanied by decreased cone density. Methods: Monocular data from 26 patients with DM and 25 healthy controls were examined to assess cone photoreceptor metrics, using confocal adaptive optics scanning light ophthalmoscopy, and red/green (RG) and yellow/blue (YB) color vision thresholds, using the Colour Assessment and Diagnosis test. Results: Both RG and YB thresholds were significantly greater in patients with DM than in the healthy controls (RG and YB = P < 0.001), and there were statistically significant differences between the 2 groups in confocal cone density at 1 degree (P = 0.024), and intercell regularity at both 1 (P = 0.013) and 2 degrees (P = 0.012). In patients with DM, cone density was inversely correlated with YB (at 0.5, 1 and 2 degrees, all P values < 0.041), but not for RG color vision thresholds. Conclusions: This is the first study to investigate the relationship between cone metrics and color vision in patients with DM. The results reveal a significant inverse relationship between confocal cone density and color vision thresholds at the locations assessed within the foveal region. These findings represent a significant advancement in oculomics research.