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D. M. O. Bonci, M. Gualtieri, M. Neitz, J. Neitz, A. L. A. Moura, F. M. Damico, D. F. Ventura; Color Vision and Spatial Contrast Sensitivity in Patients With the Risk Allele for Diabetes Proliferative Retinopathy: Preliminary Data. Invest. Ophthalmol. Vis. Sci. 2010;51(13):120.
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Erythropoietin (EPO) is a potent angiogenesis promoter. A genetic marker associated with diabetic microvascular proliferation has been identified in the EPO gene promoter. The expression of the T allele is associated with higher intraocular concentrations of EPO, and therefore it is considered to be a risk factor for the development of proliferative diabetic retinopathy (PDR). In this study, we correlated luminance spatial contrast sensitivity (LSCS) and color vision in type 2 diabetics without retinopathy with the genetic marker for PDR.
We evaluated fifteen patients (7F, 8M, mean age = 58 ± 8 years) with diagnosis of type 2 diabetes without retinopathy. Color discrimination thresholds were measured along the protan, deutan, and tritan axes, as well as a MacAdam ellipse at CIE coordinates u’ = 0.1977 v’= 0.4689 using the Cambridge Colour Test (Cambridge Research Systems). LSCSs were measured with the Psycho software (Cambridge Research Systems). The thresholds were measured at 0.2, 0.5, 1.0, 2, 5, 10 and 20 cpd. The EPO marker was identified by direct sequencing.
Six patients were homozygous for the risk allele T, 4 had the genotype GG and 5 patients were heterozygous (TG). Although LSCS was higher in GG patients than in TG and TT patients, there was no statistical significance in the LSCS results (p=0.16) (Table 1). On the other hand, there was a statistically significant difference in color vision thresholds (Table 2) when the group GG was compared to the groups with a risk allele (TT and TG) (p=0.01).
These preliminary results suggest a stronger association between the risk allele for PDR and losses in color vision, compared to losses in LSCS. Further studies are necessary to establish if color vision sensitivity is more susceptible to damage than LSCS in eyes with high EPO level.
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