Purchase this article with an account.
Brett G Jeffrey, Donnell A Knighten, Catherine A Cukras, Brian Patrick Brooks, Wadih M Zein; Quantitative Measurement of Color Discrimination with a Low Vision Color Test in Patients with Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1399.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
A quantitative means of assessing the progression of dyschromatopsia in retinitis pigmentosa (RP) is desirable for clinical trials and describing the natural history of RP. The present study evaluates a low-vision version of the Cambridge Color Test (LvCCT) for the quantitative measurement of color vision in RP subjects.
Color discrimination thresholds were measured from 29 subjects aged 13-73 years diagnosed with RP (N=16) or Usher syndrome (N=13). Visual acuity ranged from 20/20 to 20/800. Color thresholds were also measured from 12 healthy volunteers aged 23-61 years. Color discrimination thresholds were measured along 8 axes spaced 45° apart in CIE 1976 L*u*v* space using the LvCCT. Derived parameters included 1) Achromatic area (106 u*v*2) of the chromaticity diagram, calculated as the area inside the polygon formed by connecting threshold points and, 2) Angle of confusion determined from the opposing axes with the largest separation in thresholds.
Log achromatic area (log AA) was significantly correlated with logMAR acuity (p<0.001) but not with any ERG parameter. The log AA of 4 subjects with 20/20 acuity were near normal limits (log mean ± SD = 1.45 ± 0.34) compared with controls (1.12 ± 0.13). Five of 7 subjects with 20/25 - 20/32 acuity had increased achromatic area with mean elevation of 0.9 log units. All 18 subjects with acuity of 20/40 or worse had significantly enlarged achromatic areas; mean elevation rose from 1.7 log units for 20/40 subjects to > 3 log units for acuity worse than 20/250. The angle of confusion revealed a clear tritan defect in all 12 subjects with acuity of 20/40 or better and an enlarged achromatic area. In contrast, 11 of 13 subjects with acuity of 20/50 or worse, the angle of confusion did not align with classic confusion lines; 2 remaining subjects had tritan defects.
These results show that the blue-cone mediated pathway is altered early in RP when acuity is 20/40 or better. With further loss of acuity, the level of dyschromatopsia rapidly worsens as evidenced by the large increase in achromatic area and the non-specific changes in angles of confusion indicating widespread disruption of all cone-mediated function. This study confirms that the LvCCT provides a means of quantifying color discrimination changes in RP subjects including those with very low acuity.  Simunovic MP Vis Res 1998 38:3413-9
This PDF is available to Subscribers Only