Abstract
Purpose: :
To investigate whether colour vision deficiency (CVD) in patients with Stargardt disease (STD) is predominantly in the red-green axis (R/G) as is often described. If present, whether the R/G defect is a pseudoprotanomaly. And, to establish whether a correlation exists between best-corrected visual acuity (BCVA) loss and degree of CVD.
Methods: :
A retrospective, cross-sectional study of 31 patients (62 eyes) with STD who underwent CV testing using Ishihara, Tritan Plate & Hardy-Rand-Rittler (HRR) pseudo-isochromatic (PIC) plates and the Panel D-15 test (PD-15) under standardised C-light. In addition, 9 patients underwent Nagel anomaloscopy. All patients had a clinical diagnosis of STD, confirmed by identification of mutations in ABCA4.Eyes were allocated to 5 groups based on BCVA.
Results: :
CV was normal in 9/62 eyes (15%).All tests showed a progressive increase of the number of R/G CVDs as BCVA declined.In 53 eyes with BCVA below 0.75, R/G CVD of the deutan type were established in about 50% with Ishihara plates.The Tritan plate showed R/G CVD in all BCVA groups.Results of the HRR test showed a R/G CVD in at least 50% of eyes for all BCVA categories. Where specificity of the R/G CVD could be established, a more equal distribution between deutan and protan subtypes was noted.With the PD-15 test, a progressive increase of the number of R/G CVDs of the protan type became apparent as BCVA decreased further below 0.5. In contrast, the ratio of R/G CVDs of the deutan type remained fairly constant.Both HRR and PD-15 tests showed additional Blue/Yellow (B/Y) CVDs predominantly in groups with lower BCVA. In eyes with BCVA <0.1 these additional B/Y CVDs tended towards scotopisation on PD-15.Overall, PIC plates & PD-15 tests showed aspecific R/G CVDs in 53 eyes.However, anomaloscopy performed in 9 patients, revealed a pseudoprotanomaly in 8 and a pseudodeuteranomaly in 1.
Conclusions: :
CV can be normal in eyes with STD and good BCVA.In those STD eyes with BCVA below 0.75, CVDs were initially and predominantly of the R/G type, with additional B/Y defects manifesting as BCVA declined, eventually leading to scotopisation.Surprisingly, in eyes with BCVA below 0.50, the Ishihara test showed a deutan type R/G CVD in 50%.A predominance of pseudoprotanomaly was evident only on anomaloscopy.
Keywords: color vision • retinal degenerations: hereditary • clinical (human) or epidemiologic studies: prevalence/incidence