Effect of Refractive error on VEP in Myopic Boys and Girls

Abstract

Introduction: Visual evoked potentials (VEPs) are summated electrical signals generated by occipital regions of the Cortex in response to visual stimuli & recorded from human scalp. It tests the function of visual pathway from retina to occipital cortex and more sensitive to changes in the visual stimuli. It is very useful when causes of poor vision are uncertain. VEP amplitude and latencies are affected by multiple variables like age, gender, eye dominance, eye movement, visual acuity and refractive errors. To determine the influence of refractive error on VEP this study was done in myopic boys and girls. Methods: 40 controls, 17 boys, 23 girls were selected.40 myopic subjects, 17 boys, 23 girls with refractive error in a range of 1to 8.5 Dioptres were participated. All were aged between 17-21.Refractive error was measured by auto refractometry. VEPs were performed by checkerboard reversal stimuli system. Results: Statistical analysis showed significant prolongation of P100 latency [P100L] in myopic subjects with a P value of < 0.0001. Reduction in P100 amplitude was found and it was significant at P< 0.1 .The results were also compared separately for boys and girls.P100L was significant with a P value of < 0.0001 for boys and it was significant with a P value of 0.0007 for girls. With regard to amplitude, reduction in amplitude was observed with a significant P value of 0.0369 for boys and insignificant reduction in amplitude with a P value of 0.4103 for girls. Pearson's correlation study revealed negative correlation for VEP-L and weak positive correlation for VEP-amplitude. Conclusion: During VEP recording, the subject is advised to wear corrective lenses and this study can be used to prevent misinterpretation of VEP findings.