Abstract
Purpose: :
Chronic progressive external opthalmoplegia (CPEO) is the most frequent mitochondriopathy and in 80% a multi-system-disorder. Ca. 30% of the patients show a typical retinopathy. We examined a large group of this rare disease without visible retinopathy to detect subclinical involvement of retinal pigment epithelium and differences between the two most frequent underlying mutations of mtDNA.
Methods: :
We examined n = 23 patients (age 27-74, median 54 y.) with clinical, histological and genetic assured CPEO without funduscopic visible retinal changes, single deletion of mtDNA n=13, multiple deletions of mtDNA n=10.All patients got a complete ophthalmological status and electroretinography according to ISCEV-standard.
Results: :
Visual acuity: median 0,9, minimum 0,4, maximum 1,4, mean 0,85.Visual field (horizontal extent): III/4 median 135° (110°-147°), II/2 median 82°, (40°-105°).ERG-amplitudes were described related to age-related standard values (Jacobi et al. 1993), lower limits = 100%.Oscillatory potentials were significant above the lower limit with 210% (p=0,00). Median of photopic b-wave response is with 81% significant below the lower limit (p=0,007). All other responses are near the lower limit of normal range but not significant different (p> 0,05): dark adapted 0,01: 82%, dark adapted 3,0 a-wave: 97%, b-wave: 93%, light adapted 3,0 a-wave: 79%, b-wave: 81% (significant), 30-Hz-flicker: 113%.There is only a low correlation between visual acuity and a-wave photopic ERG (p= 0,02, R=0,497). All other parameters (scotopic ERG versus visual field, photopic ERG versus visual acuity) were not correlated.There was no significant correlation between duration of disease/age and ERG-amplitudes. There were no significant differences between patients with single versus multiple deletions of mtDNA.
Conclusions: :
There is a wide variability of ERG-answers in these patients like known in healthy subjects. Conspicuosly ERG-amplitudes disperse in the range of the lower limit of healthy subjects. This could be a sign of a subclinical deterioration of pigment epithelium allowing a normal visual function in the most cases. There were no differences between patients with multiple versus single deletions in contrast to CPEO-patients with visible retinopathy which is very more frequent in patients with single deletions. A correlation to visual function and to age or duration of the disease could not be demonstrated.
Keywords: mitochondria • retina • electrophysiology: clinical