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Influence of Refractory Error on the Pattern Reversal VEPs of Myopes and Hypermetropes


Affiliations
1 Assistant Professor, Dept. of Physiology, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Wardha Maharashtra
2 Assistant Professor, Dept. of Anatomy. Mahatma Gandhi Institute of Medical Sciences, Sevagram, Wardha Maharashtra
3 Professor, Dept. of Physiology, AIIMS, Patna, Bihar
4 Professor, Dept. of Ophthalmology, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Wardha Maharashtra
     

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Objective: Multiple factors including age, sex, habituation, refraction, cooperation and technical variables are associated with Visual evoked potential (VEP). We attempted to evaluate the influence of refractory error on the Pattern Reversal Visual Evoked Potential (PRVEP) recordings of a cohort of Indian subjects having myopia and hypermetropia.

Material: This rural hospital based study was conducted in the Neurophysiology unit of the Department of Physiology. The study comprised of pattern reversal visual evoked potential (PRVEP) recordings from 50 hypermetropes and 50 myopes with and without glasses having age in the range of 18-40 years. The recordings were compared with those of 50 age and sex matched controls.

Methods: One channel VEP recordings were performed with the stimulus configuration consisting of the transient pattern reversal method in which a black and white checker board was generated (full field) and displayed on VEP Monitor (colour 14") by an electronic pattern regenerator inbuilt in an Evoked Potential Recorder (RMS EMG EP MARK II). P100 latency and amplitude were measured from the averaged waveforms and analysed by student's "t" test.

Results: P100 latency was increased and amplitude decreased with and without correction of refractive error. The statistical analysis revealed a significant difference (p<0.05) in latency of P100 and amplitude of P100 between controls and myopics with glasses and highly significant difference (p<0.001) in latency and amplitude of P100 between controls and myopics without glasses. The difference in P100 latency and amplitude between controls and hyperopics with glasses and those without glasses were found to be non-significant.

Conclusion: VEPs are affected in subjects with refractive error irrespective of correction given. Among the refractory errors, the VEPs seem to be more affected by myopia than hypermetropia and the probable contributory cause may be the defocusing of the image.

 


Keywords

Refractive Error,Hypermetropes, Myopes, P100 Latency, P100 Amplitude
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  • Influence of Refractory Error on the Pattern Reversal VEPs of Myopes and Hypermetropes

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Authors

Ruchi Kothari
Assistant Professor, Dept. of Physiology, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Wardha Maharashtra
Pradeep Bokariya
Assistant Professor, Dept. of Anatomy. Mahatma Gandhi Institute of Medical Sciences, Sevagram, Wardha Maharashtra
Ramji Singh
Professor, Dept. of Physiology, AIIMS, Patna, Bihar
Smita Singh
Professor, Dept. of Ophthalmology, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Wardha Maharashtra

Abstract


Objective: Multiple factors including age, sex, habituation, refraction, cooperation and technical variables are associated with Visual evoked potential (VEP). We attempted to evaluate the influence of refractory error on the Pattern Reversal Visual Evoked Potential (PRVEP) recordings of a cohort of Indian subjects having myopia and hypermetropia.

Material: This rural hospital based study was conducted in the Neurophysiology unit of the Department of Physiology. The study comprised of pattern reversal visual evoked potential (PRVEP) recordings from 50 hypermetropes and 50 myopes with and without glasses having age in the range of 18-40 years. The recordings were compared with those of 50 age and sex matched controls.

Methods: One channel VEP recordings were performed with the stimulus configuration consisting of the transient pattern reversal method in which a black and white checker board was generated (full field) and displayed on VEP Monitor (colour 14") by an electronic pattern regenerator inbuilt in an Evoked Potential Recorder (RMS EMG EP MARK II). P100 latency and amplitude were measured from the averaged waveforms and analysed by student's "t" test.

Results: P100 latency was increased and amplitude decreased with and without correction of refractive error. The statistical analysis revealed a significant difference (p<0.05) in latency of P100 and amplitude of P100 between controls and myopics with glasses and highly significant difference (p<0.001) in latency and amplitude of P100 between controls and myopics without glasses. The difference in P100 latency and amplitude between controls and hyperopics with glasses and those without glasses were found to be non-significant.

Conclusion: VEPs are affected in subjects with refractive error irrespective of correction given. Among the refractory errors, the VEPs seem to be more affected by myopia than hypermetropia and the probable contributory cause may be the defocusing of the image.

 


Keywords


Refractive Error,Hypermetropes, Myopes, P100 Latency, P100 Amplitude

References