Male prevalence of acquired color vision defects in asymptomatic carriers of Leber's hereditary optic neuropathy.
OBJECTIVE
Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease resulting in loss of central vision and dyschromatopsia, caused by mitochondrial DNA point mutations. However, only a subset of the mutation carriers becomes affected, with a higher penetrance in males. This study was conducted to investigate chromatic losses in asymptomatic carriers of the LHON mutation.


METHODS
Monocular chromatic discrimination was studied with the Cambridge Colour Test (CCT; Cambridge Research Systems, Ltd., Rochester, UK) along the protan, deutan, and tritan cone isolation axes in 46 LHON carriers (15 men) belonging to the same LHON maternal lineage and 74 age-matched control subjects (39 men). Inclusion criteria were absence of ophthalmic complaints and clear ocular media. A detailed neuro-ophthalmic examination was performed in all the LHON carriers.


RESULTS
The differences in threshold between carriers and control subjects were significant for the three cone isolation axes at P < 0.0001. Sixty-five percent of the carriers had abnormal protan and/or deutan thresholds; some of those with higher thresholds also had elevated tritan thresholds (13%). The male thresholds were higher and more frequent than those of the women for the protan and deutan axes (ANOVA; P < 0.05), but not for tritan thresholds. In the most severe losses, the women had instances of diffuse defect whereas all the men displayed a red-green defect.


CONCLUSIONS
Male LHON asymptomatic carriers had color vision losses with the red-green pattern of dyschromatopsia typical of patients affected with LHON, which includes elevation of tritan thresholds as well. This predominantly parvocellular (red-green) impairment is compatible with the histopathology of LHON, which affects mostly the papillomacular bundle. In contrast with male losses, female losses were less frequent and severe. These gender differences are relevant to understanding LHON pathophysiology, suggesting that hormonal factors may be of great importance.
Ventura
Dora Fix
DF
Department of Experimental Psychology, University of São Paulo, São Paulo, Brazil.
Gualtieri
Mirella
M
Oliveira
André G F
AG
Costa
Marcelo F
MF
Quiros
Peter
P
Sadun
Federico
F
de Negri
Anna Maria
AM
Salomão
Solange R
SR
Berezovsky
Adriana
A
Sherman
Jerome
J
Sadun
Alfredo A
AA
Carelli
Valerio
V
D000328:Adult; D001938:Brazil; D003119:Color Perception Tests; D003117:Color Vision Defects / Q000453:epidemiology / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics*; D005260:Female; D006580:Genetic Carrier Screening; D006579:Heterozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D029242:Optic Atrophy, Hereditary, Leber / Q000235:genetics*; D010375:Pedigree; D017354:Point Mutation; D015995:Prevalence; D015203:Reproducibility of Results; D012737:Sex Factors
D004272:DNA, Mitochondrial