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C. Tamaki, C.S. Kallie, V. Carelli, A. Berezovsky, P.A. Quiros, C.F. Chicani, F. Sadun, A. DeNegri, A.A. Sadun, S.R. Salomao; Comparing Reading Performance of Unaffected Carriers Leber’s Hereditary Optic Neuropathy (LHON) to Two Different Control Groups . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3471.
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© ARVO (1962-2015); The Authors (2016-present)
Leber’s Hereditary Optic Neuropathy (LHON), caused by mitochondrial point mutations, is characterized by profound bilateral loss of central vision in affected individuals. However, carriers are usually thought of as having normal visual function. The purpose of this study was to compare reading performance of unaffected carriers with performance of spousal controls, and controls from a different geographic location.
Participants included twenty normal controls (10 males & 10 females), ranging from 14 to 48 yrs (µ = 27.1), fifty–six unaffected carriers (20 males & 36 females), ranging from 8 to 77 yrs (µ = 33.0) and thirty–one normal spouses (18 males & 13 females), ranging from 17 to 63 yrs (µ = 40.3). Inclusion criteria were informed consent, best corrected visual acuity (ETDRS chart) of 20/40 or better in each eye, and absence of self–reported reading and cognitive impairments. Reading performance was assessed by measuring critical print size (CPS) and maximum reading speed (MRS) using the Portuguese version of the MNREAD reading acuity charts. MNREAD was presented binocularly at a distance of 40 cm, with appropriate reading addition for patients over age 40, under controlled illumination conditions.
As found previously by Tamaki, et al (ARVO 2005), carriers were different than controls in both CPS (t(94) = 5.49, p < .001) and MRS (t(94) = 7.91, p < .001). Although carriers were different than controls, they were not different than spousal controls in CPS (t(112) = 1.67, p = .097) or MRS (t(112) = 1.93, p = .057). Spouses were also different than the other controls.
Geographic location has an impact on both maximum reading speed and critical print size. The most notable effect was found in the mean difference between CPS of spouses, and the other controls. The mean difference in CPS was 0.35 logMAR larger (about three and one half lines on the MNREAD chart) for spouses than for the other controls. Additionally, spouses read an average of 81 words per minute slower than the other controls. This study indicates the importance of carefully selected internal controls in studies such as the LHON project.
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