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A. Colenbrander, D.C. Fletcher; Evaluation of a new Mixed Contrast Reading Card . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4352.
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Purpose:To evaluate a new rapid screening test for clinical practice that combines reading performance and contrast deficit testing into a single test. Methods: The mixed–contrast reading card (MC card) presents alternate lines of high and low (10%) contrast for each print size: Print sizes follow the logMAR progression. All sentences are of equal length to allow reading speed measurements. The card thus allows determination of THRESHOLD reading acuity (smallest size read) as well as FUNCTIONAL reading acuity (smallest size read fluently, "critical print size") for high contrast (HC) as well as for low contrast (LC). 37 low vision patients with a wide variety of pathologies were tested on the MC card, Pelli–Robson contrast, Lea contrast, MN Read acuity and ETDRS acuity. Further studies are ongoing at several locations and include (1) normal patients of all ages, (2) routine exams of elderly patients and (3) low vision patients. Results: In the Low Vision group, ETDRS acuity ranged from 20/20 to 20/697 (median 20/120). All subjects showed a decreased ability to read LC vs. HC print with a difference ranging from 2 to 12 lines (mean 5.6). MN Read scores were highly correlated with the MC–card HC scores, but not with the LC scores. ETDRS acuity scores were correlated with the MC–card HC minimum size read, but not with the LC minimum size. Significant reductions in Pelli–Robson and Lea contrast correlated highly with reductions in MC–card LC scores. Conclusions:The mixed–contrast reading card provides an effective means to introduce contrast testing into general practice without the time consuming use of separate tests for high and low contrast. The MC–card HC score correlates well with ETDRS acuity and MN Read tests. The MC–card LC score correlates well with Pelli–Robson and LH contrast tests. By testing reading performance the test assesses a larger retinal area than does letter acuity. This is significant since early AMD may show only localized para–foveal contrast changes (MacKeben et al., p. 158 in: Vision Rehabilitation, Swets & Zeitlinger, 1999). From tests on 75 seniors (ages 42–86, median 70) it appears that a 1 or 2–line difference is normal, 3 lines is marginal, 4 or more is abnormal. Testing takes little more time than testing for high contrast alone.
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