Original article
Functional Defects in Color Vision in Patients With Choroideremia

https://doi.org/10.1016/j.ajo.2015.06.018Get rights and content

Purpose

To characterize defects in color vision in patients with choroideremia.

Methods

Thirty patients with choroideremia (41 eyes) and 10 age-matched male controls (19 eyes) with visual acuity of ≥6/36 attending outpatient clinics in Oxford Eye Hospital underwent color vision testing with the Farnsworth-Munsell 100 hue test, visual acuity testing, and autofluorescence imaging. To exclude changes caused by degeneration of the fovea, a subgroup of 14 patients with a visual acuity ≥6/6 was analyzed. Calculated color vision total error scores were compared between the groups and related to a range of factors using a random-effects model.

Results

Mean color vision total error scores were 120 (95% confidence interval [CI] 92, 156) in the ≥6/6 choroideremia group, 206 (95% CI 161, 266) in the <6/6 visual acuity choroideremia group, and 47 (95% CI 32, 69) in the control group. Covariate analysis showed a significant difference in color vision total error score between the groups (P < .001 between each group).

Conclusions

Patients with choroideremia have a functional defect in color vision compared with age-matched controls. The color vision defect deteriorates as the degeneration encroaches on the fovea. The presence of an early functional defect in color vision provides a useful biomarker against which to assess successful gene transfer in gene therapy trials.

Section snippets

Methods

Patients were assessed as part of an ongoing choroideremia gene therapy clinical trial, approved by the National Research Ethics Service Committee for West London & GTAC (ClinicalTrials.gov identifier NCT01461213) and conducted in accordance with the Declaration of Helsinki. Patients with a clinical diagnosis of choroideremia, referred for consideration of inclusion in the gene therapy project, attending outpatient clinics at Oxford Eye Hospital were included in the analysis. The ethics

Results

The order of the caps was recorded and partial error scores calculated at each position (Figure 1).

The total error score was calculated from the partial error scores. Age adjustment was made by including the covariate age in the analysis to control for the change in test performance due to age.11 Descriptive statistics are shown in Tables 1 and 2.

A significant difference in color vision total error score between each of the subgroups of choroideremia eyes (mean error score of 206 in the group

Discussion

In summary, the results showed a significantly reduced color vision total error score in each of the groups of patients compared to age-matched normal control subjects. The reduction in color vision does not follow a specific axis and is generalized across the spectrum, varying between patients. However, a decrease in sensitivity to the red subset of caps was detected. Simulated visual field loss in the normal control subjects shows that visual field does not account for the extent of the color

Jasleen K Jolly is an optometrist working for the Nuffield Laboratory of Ophthalmology, University of Oxford, and Oxford Eye Hospital. She studied at Cardiff University and the University of Manchester, working across the world in various settings to gain a wide range of experience. She is actively involved in clinical research in the fields of retinal gene therapy, cataract surgery outcomes and low vision. Her main interest is improving outcome measures following gene therapy treatments.

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    Jasleen K Jolly is an optometrist working for the Nuffield Laboratory of Ophthalmology, University of Oxford, and Oxford Eye Hospital. She studied at Cardiff University and the University of Manchester, working across the world in various settings to gain a wide range of experience. She is actively involved in clinical research in the fields of retinal gene therapy, cataract surgery outcomes and low vision. Her main interest is improving outcome measures following gene therapy treatments.

    Robert E MacLaren is the 2015 RP Scientist of the Year, receiving the John Marshall Award, RP Fighting Blindness. He was recipient of the Jessie Mole Medal in 2014; awarded annually for retinitis pigmentosa research; together with The Euretina Lecture, awarded annually to the lead retina specialist in Europe. He is a Professor of Ophthalmology at the University of Oxford, with honorary clinical posts at the Oxford Eye Hospital and Moorfields Eye Hospital.

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