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H. Jayaram, L. Membrey, J. Hancox, H. Sheth, A. Laidlaw; The Effect of Simulated Lens Opacity on Colour Vision Evaluated Using the Cambridge Colour Contrast Test, the Ishihara Pseudoisochromatic Plates and the Farnsworth Munsell 100 Hue Test . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4749.
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Purpose: To assess the effect of simulated lens opacity on colour vision. Methods: Five normal subjects within 1 dioptre of emmetropia were tested with pupil dilation. Five monocular goggles were made containing no filter, yellow filter, diffusing filter, 0.9 log unit ND filter and a combination of all 3. ETDRS number of letters, Pelli–Robson Contrast Sensitivity (PRCS), Farnsworth Munsell 100 Hue (FM) results, the first 17 Ishihara Pseudoisochromatic Plates (IPP) and the Cambridge Colour Contrast Trivector (CCCT) thresholds were assessed for each subject with each goggle in random order. Results: The median EDTRS letters was 48 (IQ range 45 to 57) with no filters, there was no significant effect with either the yellow or the ND filter. With the diffusing filter this fell to 0 (IQ range 0 to 0.5) and no letters were read with the combined filter(p<0.001). The mean number of triplets read on the PRCS test was 12 (IQ range 11.5 to 12), again there was no significant effect of either the yellow of neutral density filters but this fell to 1.0 (IQ range 0 to 2.5) with the diffusing filter and 1.0 (IQ range 0.0 to 1.5) with the combined filter (p<0.001). All subjects correctly identified all 17 IPPs with no filter, the yellow and the ND filters. There was no significant effect of the diffusing filter but with the combined filter the median number was 15 (IQ range 13 to 16) (p= 0.03). The square root of the total error score for the FM test was 9.2 (IQ range 7.4 to 10.0) with no filter. There was no significant effect of either the ND or diffusing filters. This increased to 14 .7 (IQ range 14.1 to 15.4) with the yellow filter (p= 0.001) with a predominantly tritan axis and to 20.1 (IQ range 18.2 to 21.4) with the combined filter. The median protan, deutan and tritan thresholds on the CCCT were 46 (IQ range 39 to 57), 43 (IQ range 34.5 to 49) and 100 (IQ range 82.5 to 132) respectively. There was no significant effect of the ND filter. With the yellow filter there was a significant elevation of the tritan threshold to 396 (IQ range 192 to 466) (p=0.03). All thresholds were elevated with the diffusing filter and with the combined filter (p<0.05). Conclusions: These results show that the IPP are little affected by these filters with only a small reduction in the number of correctly identified plates with the combined filter despite large effects seen on acuity and contrast sensitivity. As might be expected both the FM and CCCT show tritan defects with the yellow filter. The CCCT is also affected by the diffusing filter. These results suggest that the FM and the CCCT may be affected by lens opacity.
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