Chiasmal coefficient of flash and pattern visual evoked potentials for detection of chiasmal misrouting in albinism

The diagnosis of albinism can be confirmed by electrophysiological examination, when chiasmal misrouting can be demonstrated. The present study describes a quantitative analysis method for this purpose. A chiasmal coefficient (CC) was calculated by correlating the differential potential over left an...

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Bibliographic Details
Published in:Documenta ophthalmologica 2003-03, Vol.106 (2), p.137-143
Main Authors: POTT, J. W. R, JANSONIUS, N. M, KOOIJMAN, A. C
Format: Article
Language:English
Subjects:
Adolescent
Adult
Albinism, Oculocutaneous - physiopathology
Biological and medical sciences
Child
Child, Preschool
Electrodiagnosis. Electric activity recording
Electrooculography. Electroretinography
Electroretinography
Evoked Potentials, Visual
Humans
Infant
Investigative techniques, diagnostic techniques (general aspects)
Medical sciences
Nystagmus, Congenital - physiopathology
Optic Chiasm - physiopathology
Optic Nerve Diseases - diagnosis
Optic Nerve Diseases - physiopathology
Pattern Recognition, Visual
Photic Stimulation
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Summary:The diagnosis of albinism can be confirmed by electrophysiological examination, when chiasmal misrouting can be demonstrated. The present study describes a quantitative analysis method for this purpose. A chiasmal coefficient (CC) was calculated by correlating the differential potential over left and right hemisphere, when stimulating left versus right eye. This CC will be negative in albinism and positive in normal individuals. VEPs were recorded in 20 control subjects, four children with congenital motor nystagmus and six children with albinism. In up to 25% of the controls the CC was negative, when using flash VEP. However, with pattern VEP all had a positive CC. All children with albinism had a negative CC. Three of the four patients with congenital motor nystagmus had a positive CC, and one child had a small negative value with flash stimulation. In conclusion, determination of CC is a valuable and objective analysis method for electrophysiological determination of chiasmal misrouting. The method is relatively simple and only needs two electrode tracings. One should be aware of false-positive results when using flash stimulation. Whenever possible pattern stimulation should be used.
ISSN:0012-4486
1573-2622
DOI:10.1023/A:1022526409674