Reading Performance in Asymptomatic Carriers From a Very Large Brazilian Pedigree With 11778 Leber’s Hereditary Optic Neuropathy (LHON)

Abstract

Abstract: : Purpose: LHON is a maternally inherited disease, associated with mitochondrial DNA (mtDNA) point mutations and characterized by profound bilateral loss of central vision. The purpose of this study was to determine the reading acuities and the reading speeds on previously described asymptomatic carriers from a very large pedigree with Leber's Hereditary Optic Neuropathy (LHON). Methods: Participants were thirty–nine asymptomatic carriers (10 males, 29 females) from a very large Brazilian pedigree with 11778 LHON mutation, aging from 10 to 59 years (mean = 33.0 ± 14.7; median = 32.1). Inclusion criteria were: informed consent, best corrected visual acuity (ETDRS chart) of 20/25 or better in each eye, absence of self–reported reading and/or cognitive impairments. Reading performance was assessed through a test measuring critical print size and maximum reading speed, using the recently developed and validated 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. MNREAD profiles of reading speed versus text size were compared to profiles found in previously tested normals (Tamaki et al, ARVO 2004). Results: Bilinear least–squares fits of the LHON asymptomatic carriers produced critical print sizes ranging from logMAR –0.17 to logMAR 0.68 (mean: 0.11, standard deviation: 0.18) and were significantly larger than the normal group (t(57) = –3.40, p = 0.001). Maximum reading speeds ranged from 71 to 196 words per minute (mean: 140, standard deviation: 34), and were significantly slower than the normals having a mean maximum reading speed of 200 words per minute (t(57) = 7.34, p < 0.001). Conclusions: Reading performance profiles of these asymptomatic 11778/LHON carriers was characterized by slower reading speeds and larger critical print sizes than previous normative data. These results confirm and extend previous reports of subclinical abnormalities in visual function in asymptomatic carriers from this family.

Keywords: reading • visual impairment: neuro-ophthalmological disease • mitochondria