Rod photoreceptor function in children with mitochondrial disorders.
OBJECTIVE
To test the hypothesis that function of the rod photoreceptors is abnormal in pediatric patients with mitochondrial disorders.


METHODS
Patients (n = 22; median age, 5 years) with a deficiency of 1 or more of the mitochondrial enzyme complexes, or a mutation in mitochondrial DNA, were studied by means of scotopic, full-field electroretinography (ERG). The conditions of ERG testing allowed derivation of the parameters of the activation of rod phototransduction from the ERG a-wave, and postreceptoral function from b-wave and P(2) stimulus-response functions. The deactivation of phototransduction was studied in 5 patients. The patients' ERG responses were compared with those of healthy control subjects (n = 25).


RESULTS
Responses from 19 patients were sufficient for analysis of rod photoreceptor and postreceptoral function. Saturated amplitudes of the rod photoresponse and b-wave sensitivity were significantly depressed in the patients. Saturated amplitudes of rod cell and P(2) responses were correlated. The kinetics of deactivation of phototransduction were slowed even if the kinetics of activation were normal.


CONCLUSIONS
In patients with mitochondrial disorders, some abnormalities of the scotopic ERG responses originate in the rod photoreceptors, but postreceptoral processes may also be abnormal. From a practical perspective, ERG testing can contribute to diagnosis of mitochondrial disorders.
Cooper
Linda L
LL
Department of Ophthalmology, Children's Hospital Boston and Harvard Medical School, Mass 02115, USA.
Hansen
Ronald M
RM
Darras
Basil T
BT
Korson
Mark
M
Dougherty
Frances E
FE
Shoffner
John M
JM
Fulton
Anne B
AB
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004272:DNA, Mitochondrial; D003623:Dark Adaptation; D004596:Electroretinography; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008931:Mitochondria, Muscle / Q000201:enzymology; D028361:Mitochondrial Diseases / Q000503:physiopathology*; D010088:Oxidoreductases / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000503:physiopathology*; D014785:Vision, Ocular / Q000502:physiology
D004272:DNA, Mitochondrial; D010088:Oxidoreductases