Abstract
Purpose: :
To evaluate color vision in DMD subjects and to correlate these findings with the Vignos motor function scale for neuromuscular disorder and with the region of gene deletion.
Methods: :
We evaluated 77 subjects with DMD (age 14.6 ±4.5yrs) classified in 3 groups according with their gene deletion: no deletions (n=29); deletion upstream exon 30 (n=8); deletion downstream exon 30 (n=40). Controls were 35 age–matched subjects. Color vision was evaluated with Cambridge Colour Test (CCT) – Trivector and Ellipses protocols, Neitz Anomaloscope, and two plate tests: Ishihara and AO H–R–R plates. Response reliability was assessed in the CCT with catch trials interspersed in the staircases.
Results: :
Color vision tests could be performed in 63/77 (81%) of the subjects Poor collaboration and difficulty understanding the instructions prevented test performance in the remaining 14 patients, which had deletion downstream exon 30 (8/14) or no deletions (6/14). Color vision losses measured by the CCT were found in 44/63 (69%) subjects, the majority of which (81%) had a red–green defect, confirmed by the Anomaloscope results (Wilcoxon test – Trivector p= .71; Ellipse p< .98). The AO H–R–R and Ishihara plates were less sensitive, revealing respectively, 2% and 9% of red–green color vision losses; and these results did not correlate with the Rayleigh matches (AO H–R–R p= .006; Ishihara p< .001). Red–green defect was present in 14/23 (60%) subjects with no deletion and in 21/32 (66%) subjects with deletion downstream exon 30. All controls and DMD subjects had 100% correct responses to the catch trials. No correlation was found between the score obtained with the Vignos motor scale and CCT color vision thresholds .
Conclusions: :
With the color vision test battery used we observed that red–green losses seem to be more frequent and more severe in subjects with deletions downstream exon 30, which involve the retinal dystrophin isoform Dp260. These findings suggest a secondary effect of the dystrophin mutation in retinal function.
Keywords: color vision • retina • genetics