The Quantification Of Visual Acuity And Parameter Of Pattern Reversal Visual Evoked Potentials Using Mathematical Modeling Procedures

Objective: In the forensic clinical medicine it is difficult to use an objective method for assessing visual acuity of the traumatic eyes. The Pattern Reversal Visual Evoked Potential(PRVEP). a gross electric signal generated by the occipital cortex, in response to spatial pattern stimuli, has been used to evaluate the visual acuity objectively. The constancy of the first positive wave at approximately 100 msec makes the latency of P₁₀₀ wave the most often useful measurement in the clinical electrophysiology. The purpose of this research is to explore the relation among the parameter of P₁₀₀ elicited by pattern stimuli, spatial frequency and visual acuity in the traumatic eyes.Methods: Different kinds of outpatients with 98 traumatic eyes and 23 eyes of high myopia were enrolled from in West China Hospital, Sichuan University. Traumatic eyes were divided into the group of traumatic optic neuropathy, the group of traumatic cataract, the group of traumatic mydriasis and the group of traumatic retinopathy. 199 eyes were the control group of the eyes without disease or trauma. The reversal pattern grating of five check size( 117, 58, 29, 14, 7 min of arc) were used as stimuli. The reversal rate of the stimuli was 2.9Hz. and the contrast level was 100%. The pattern threshold for VEP's was estimated by determining the smallest element when elicited a VEP significantly. The latency andamplitude of P1Oo wave were recorded while the threshold stimulus was given. The SPSS of statistical soft was: used to describe the datum and analyse the relationship of the parameter of Pioo wave, spatial frequency and visual acuity.Results: There are high correlation between spatial frequency (X) and the log visual acuity (Y), then the respective regression equations are deduced to evaluate the visual acuity. The equation of traumatic optic neuropathy isY=⁰. 114-0. 010X (r=0. 756, p< 0.01), traumatic cataract is Y=-0. 392 -0. 01IX (r=-0. 681, p< 0. 01), traumatic mydriasis isF=⁰. 154-0. 01IX (r=-0. 653, p < 0.01), traumatic retinopathy is Y =⁰. 200-0. 014X (/^-0.827,p< 0.01), high myopia is Y = -Q. 249-0. 010X (r=-0. 665, p <0.01), and the control group is Y =0.041-0. 01IX(r=-0. 544, p < 0.01). There is a correlation is showed between the latency of Pioo wave (X) and the log visual acuity (Y) in all the checked eyes. The equations areshowed as follows: the group of traumatic optic neuropathy } =-1.485 +0. 008X(r=0. 621, p< 0. 01), traumatic cataract Y=-l. 761+0. 007X (r= 0. 606, p< 0. 01), traumatic mydriasis Y=-\. 404+0. 007X (r=0.661,/? < 0. 01), traumatic retinopathy f = -1. 810+0. 008X (r=0. 771, p< 0. 01) , high myopia Y=^l. 775+0. 010X (r=0. 393, p < 0. 0 1), and the controlgroup Y =-l. 132+0. 008X (r=0. 499, p < 0.01). There is a good correlation between PRVEP estimated acuity by the mathematical model and visual acuity.Conclusion: The VEPs can be used to evaluate the visual acuity. This method is applied to forensic medicine expertise and has more accurate and objective results.