Abstract
Purpose:
Neuro-ophthalmologists often refer patients for electrophysiology to distinguish between retinal and post-retinal pathology, and to aid in diagnosis. We performed a retrospective review to assess clinical value of visual electrophysiology in identifying causes of visual dysfunction in patients referred from neuro-ophthalmology clinics.
Methods:
A retrospective review of 410 subjects (0.3 - 88 years, mean 43.6 +/- SD 20.0) referred for visual electrophysiology from various neuro-ophthalmologists between 2009-2013 was performed. Most underwent pattern, full-field and multifocal electroretinography and pattern visual evoked potential (VEP) tests. Flash and multifocal VEP were included where indicated. Main outcome measures were the site of pathology and sensitivities for each test.
Results:
158 were referred for poor vision for investigation, 102 for unexplained visual field defects, 97 for miscellaneous visual symptoms and 53 for other reasons. Most subjects referred for poor vision for investigation had electrophysiology findings of retinopathy (37%) or post-retinal pathology (34%), and those with vision poorer than 6/24 more likely having abnormal findings (86% vs 62%, p=0.0020). Among those with unexplained visual field defects, findings of retinopathy, post-retinal pathology and normality were noted in 31%, 24% and 28%, respectively. Most subjects with miscellaneous visual symptoms had normal findings (69%). Among the tests, multifocal ERG was most sensitive for retinopathy (96%) and maculopathy (95%) and pattern VEP was most sensitive for post-retinal pathology (94%). An indeterminate result was noted in 9%.
Conclusions:
Electrophysiology was effective in allowing differentiation between retinopathy, optic neuropathy and electrophysiologic normality in 91% of subjects. Pre-testing provisional diagnoses of retinopathy and post-retinal pathology were revised in 30% and 42% respectively as a result of electrophysiologic testing. A clear understanding of the characteristics of each test used in correlation with the clinical picture and interpretation of all results in totality are important in localising the site of pathology.