Abstract
Purpose: :
INS is associated with decreased high spatial frequency acuity and/or retinal dystrophy. It is due to associated sensory system deficits or genetic origin. This study was to examine visual function in patients with INS.
Methods: :
Electorophysiology (Flash Electretinogram (ERG), Sweep and Pattern Visual Evoked Potenital (VEP) and acuity tests (Teller Card Acuity and HOTV) were recorded in 12 children (8.4 months to 16 years old) and 5 adults (32 to 58 years old). The INS was either idiopathic or associated with albinism, retinal dystrophy, high myopia, congenital night blindness or achromatopsia.
Results: :
The ERG responses were similar in children and adults. INS patients associated with retinal dystrophy, high myopia, congenital night blindness and achromatopsia displayed abnormal rod and/or cone and moderate acuity deficit (mean±sd=0.61±0.3 LogMAR). INS associated with albinism showed subnormal cone but normal rod ERG and normal parafoveal VEP but mild deficit in visual acuity (mean±sd =0.56±0.03LogMar). Idiopathic INS usually displayed normal ERG, subnormal sweep VEP and mild deficit in visual acuity (mean±sd =0.57±0.04 LogMar).
Conclusions: :
INS displayed reduced responses in visual electrophysiology and deficit in visual acuity. Abnormal rate of rod ERG is 33% and cone ERG is 40%. The abnormal rate of VEP is 71%. The rate of deficit in visual tests is 86%. However, the abnormality in visual functions depends on the types of INS. Different intervention plan is necessary for different types of INS.
Keywords: nystagmus • electrophysiology: clinical • visual acuity