Determination of Visual Acuity in Children Using Sweep Visual Evoked Potential Compared to Conventional Measuring Techniques

摘要

Background: Accurate measurement of vision in children especially the preverbal or the mentally incapacitated is a challenge. Sweep VEP (sVEP) is a non-invasive, objective tool that allows visual threshold to be quantitatively estimated. Objective: To demonstrate the applicability of using the sVEP method in measuring visual acuity in children. Methods: sVEP was used to test visual acuity in 15 children (2-13 years) with variable visual disabilities. Standard visual evoked potential (VEP) recording techniques were employed. The stimulus was a horizontal-oriented, sine wave grating that swept up the spatial frequency spectrum. Grating acuity was estimated by linear extrapolation to zero voltage of the highest spatial frequency peak in the VEP amplitude versus spatial frequency function (excluding noise). The visual acuity was further estimated with conventional visual acuity measuring techniques according to age and  mental capacity of each child. Visual acuity resulting from sVEP test was compared to conventional techniques. Electrophysiological studies including VEP, ERG and EOG were also done. Results: Two patients were normal; the rest had various ocular pathologies with or without developmental problems as cerebral palsy. Ocular pathologies encountered were strabismus, albinism, nystagmus, optic atrophy, aphakia and pseudophakia with secondary glaucoma. Nine eyes showed matching acuities in absence of obvious ocular pathology. The rest had mismatched acuities. All patients with diminished retino-cortical transmission as diagnosed with VEP, regardless the cause, showed better visual acuities with the sVEP than conventional measuring techniques. Conclusion: In subjects with normal conventional VEP, visual acuities measured by sVEP and conventional methods matched. Patients with diminished VEP and in the presence of ocular pathology the sVEP acuity exceeded that measured by conventional tools, which rendered its reliability questionable in these conditions. [Egypt J Neurol Psychiat Neurosurg.  2014; 51(4): 405-411] Key Words: visual acuity, visual evoked potential, pediatric, sweep VEP.