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A. Colenbrander, D.C. Fletcher; Contrast Sensitivity and ADL Performance . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5834.
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© ARVO (1962-2015); The Authors (2016-present)
The Mixed Contrast Reading Card (MCC) with alternating high and low (10%) contrast lines is a simple screening test for contrast sensitivity (CS). The difference in the number of lines read with high contrast (HC) and low contrast (LC) convincingly demonstrates contrast deficits.
To evaluate the relation of contrast deficits to ADL problems.
Consecutive Low Vision patients were tested. Tests included the MCC, ETDRS acuity, MN–read, Mars letter contrast. ADL problems were scored from recorded patient histories and interviews. Five general rubrics were used: reading, writing, face recognition, mobility and homemaking.
(1) In 300+ normal eyes (VA > 20/40) the HC–LC difference was 1 or 2 lines. This value does not change with age. In a Low Vision population the most common difference was 4 or 5 lines; differences up to 10 lines were recorded, some patients could not see even the largest LC print. (2) The HC reading acuity correlates tightly with the MN–read acuity (R2 = 0.86). The HC–LC difference correlates with the Mars rating, but only weakly (R2 = 0.18).
(3) Among 140 low vision patients (VA 20/20 to 20/800) there was no correlation (R2 = 0.003) between VA and HC–LC difference.
(4) The correlations with ADL scores are all weak, but trends are in the direction suggested by clinical experience. The overall ADL score was influenced equally by VA and CS. Reported reading difficulties were influenced more by VA, but writing and homemaking were influenced more by CS. Face recognition correlated more with measured reading performance. Mobility correlated slightly more with VA.
(1) The MCC provides a reliable screening test. (2) The MCC and Mars (or Pelli–Robson) tests measure different aspects of CS (slope vs. peak of the CS curve). Based on this weak correlation 1 line MCC difference is equivalent to about 1.5 Mars letters or 0.5 P–R triplet. (3) In retinal problems (image processing) CS and VA are independent variables. This is clearly different from optical problems (image formation) where blur affects both VA and CS. This difference is often overlooked in discussions of CS.
(4) Our current global scoring method for ADL problems is not sensitive enough to pinpoint CS–specific problems. There is a need for more specific rating instruments.
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