Color Vision Is Worse in the Diabetics With Risk Genotype for Retinopathy as Shown by Erythropoietin Expression Markers: Preliminary Data

Abstract

Purpose: : Genetic markers for the expression of the glycoprotein, erythropoietin (EPO), have been identified. Homozygous genotypes for the alleles (T, G) related to EPO expression are considered risk factors (TT) or protective factors (GG) for the development of diabetic retinopathy. In this study we sought to investigate the relationship between the EPO genotypes and color discrimination in pre-retinopathic type 2 diabetics.

Methods: : Color discrimination thresholds were measured in 14 type 2 diabetic subjects (7 male; 57.64 ± 7.78 yrs old; 5.5 ± 4 yrs of disease) using the Cambridge Colour Test (Cambridge Research Systems, Ltd). Thresholds were measured along the protan, deutan and a tritan axes, as well a MacAdam ellipse at CIE coordinates u’ = 0.1977 v’= 0.4689. After the functional assessment, the EPO markers were identified by direct sequencing.

Results: : Six patients were homozygous for the risk genotype TT, 3 had the protective genotype GG, and 5 patients were heterozygotes. Thresholds and color-ellipse areas from the patients homozygous for the risk factor genotype (TT) were consistently worse than those from diabetics with the GG genotype in all the parameters measured (Table 1).

Conclusions: : These preliminary results suggest association between genetic markers and pre-retinopathic functional visual changes. If verified by further study, they can provide additional valuable tools for early detection and clinical management of patients more susceptible to diabetic visual damage.Table 1: Mean ± standard error for color discrimination thresholds

Keywords: color vision • diabetic retinopathy • gene screening