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Roopa V. Vemala, Sobha Sivaprasad, John L. Barbur; Early Detection of Colour Vision Loss in Age Related Maculopathy. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5174.
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Early changes in age related maculopathy (ARM) are graded based on drusen and/ or retinal pigment epithelium on colour photographs to stratify the risks of conversion to advanced disease as typified by the AREDS classification. However, loss of visual performance may precede these structural retinal changes and may be a valuable tool for further risk stratification. In this study we evaluated the changes in colour vision in patients with early ARM using the colour assessment and diagnosis (CAD) test (Expert Rev. Ophthalmol. (2011), 6, 409-420) and correlated these changes to the structural changes seen on fundus photography, spectral domain OCT (SD-OCT) and auto-fluorescence retinal imaging.
Red-green (RG) and yellow-blue (YB) thresholds were measured using the CAD test. The statistical variability of these thresholds in normal subjects under monocular viewing conditions has been established in earlier studies. For the purpose of this study, the changes in colour vision were graded into four groups, based on the median standard normal CAD threshold: I (Mild): 2.5 - 6; II (Moderate): 7-12; III (Severe): 13-18; IV (Very severe): 19-36 CAD units. 67 eyes of 40 patients with early ARM were examined in this study. All patients were asymptomatic and had a visual acuity of 6/12 or better in the study eye. The fundus photographs were graded based on AREDS classification. The other parameters assessed included photoreceptor layer (PRL) thinning over drusen and drusen volume measured on Spectralis SD-OCT and the pattern of auto-fluorescence.
The colour thresholds were outside the normal range in all eyes. 22% had Mild, 42% Moderate, 10% Severe and 42% Very severe loss. In AREDS Level 2 (n=13); 43% had Mild, 50% had Moderate and 7% had severe loss. In AREDS Level 3 (n= 52) 25% had Mild, 48% had moderate 10% had Severe and 17% had Very severe loss. In AREDS grade 4 (n=2) 50% had Severe and 50% had Very Severe loss. The colour vision loss did not correlate to the AREDS classification of severity of the macular abnormalities.
These findings reveal loss of colour vision in early AMD with drusen in all subjects. The loss is particularly severe when drusen is present in the centre of the macula.
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