Relating risk genotypes for diabetic retinopathy with color vision performance

Abstract

 

Purpose

 

Three genetic markers of erythropoietin (EPO) expression have been recently identified as either risk- or protective-factors for the development of proliferative diabetic retinopathy (PDR). These markers are located at the regions of single nucleotide polymorphisms (SNP) rs1617640, rs507392, and rs551238. Homozygous or heterozygous genotypes at these three locations are significantly associated with a higher or lower risk of PDR in diabetics (Tong et al 2008; Abhary et al 2010). We sought to analyze how the presence of the different genotypes at these 3 SNP locations relates to functional losses observed prior to retinopathy in a group of type 1 and type 2 diabetics.

 

Methods

 

Visual function was assessed by color discrimination thresholds measured along protan, deutan and a tritan axes, as well a MacAdam ellipse (Cambridge Colour Test). The EPO markers were identified after DNA extraction from blood cells by sequencing of PCR products. The functional and the genetic assessments were performed in a group of 29 (13 type 1; 16 type 2) diabetic patients and a group of 17 healthy controls.

 

Results

 

Colour vision thresholds from the patients were higher than controls’ for all three color confusion axes and the ellipse area. The presence of the risk genotype coincided with worse color vision only for the SNP rs1617640. Control subjects with the different rs1617640 genotypes did not have different color vision (figures 1 and 2). The presence of different genotypes for the SNP rs507392, and rs551238 was not associated with different color vision results.

 

Conclusions

 

Diabetic patients who were carriers of the risk genotype at the SNP location rs1617640 - a maker for the development of PDR - were also the patients with worse color vision thresholds The same association was not observed for the other EPO gene SNP locations evaluated. The association between factors related to vascular abnormality (EPO marker) and neural loss (color vision) contribute to the intricate puzzle of the interaction between vascular and neural abnormalities which is at the core of hypotheses about the etiology of diabetic visual losses.

 

 

Color vision thresholds from the diabetics. Carriers of the allele T have higher thresholds.

 

 

Color vision thresholds from controls. Thresholds did not change across genotypes.

 

Keywords: 499 diabetic retinopathy • 471 color vision • 539 genetics