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Neruban Kumaran, Caterina Ripamonti, Angelos Kalitzeos, James W B Bainbridge, Michel Michaelides; Severe Loss of Tritan Colour Discrimination in RPE65 Associated Leber Congenital Amaurosis. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4297.
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© ARVO (1962-2015); The Authors (2016-present)
RPE65 associated Leber Congenital Amaurosis (RPE65-LCA) is a progressive Early Onset Severe Retinal Dystrophy that results in profound early dysfunction of rod photoreceptor cells followed by progressive cone photoreceptor degeneration. To date, assessment of colour discrimination has been limited to traditional plate-based colour vision tests. In this study we used three different computerised colour vision tests, which consistently reveal a severe colour discrimination defect, predominantly along the Tritan confusion axis.
6 adult subjects (aged 17 to 21) with molecularly confirmed RPE65- LCA underwent monocular colour discrimination assessment using both the trivector and the ellipse version of the following computerised tests: Cambridge Colour Test (CCT), low vision version of the Cambridge Colour Test (lvvCCT), and the Universal Colour Discrimination Test (UCDT). Stimuli were presented on a calibrated LCD Display++ monitor controlled by the Metropsis software (Cambridge Research Systems Ltd). For comparison, subjects were also tested using the Hardy Rand Rittler (HRR) plates. Each test was repeated three times.
The trivector version of the tests demonstrated that colour discrimination along the Tritan axis was undetectable in 4 subjects, and severely reduced in 2 subjects. These findings were confirmed by the ellipse version of the tests, which showed that the orientation of the ellipse coincided with the orientation of the Tritan confusion axis. Colour discrimination along the Protan and Deutan axes was evident but subnormal in 5 of the 6 subjects, as demonstrated by the areas of the individual colour discrimination ellipses. Four of the 6 subjects were unable to read any of the HRR plates.
Computerised colour vision tests facilitate measurement of colour discrimination in RPE65-LCA. The condition is associated with severe impairment of colour discrimination, particularly along the Tritan axis indicating early involvement of S-cones. This technique is likely to be valuable in measuring the impact of intervention on cone function.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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