Acta Medica Medianae (Dec 2004)
VISUAL EVOKED POTENTIALS AND „PATTERN” ELECTRORETINOGRAM IN HIGH MYOPIA
Abstract
In patients with high myopia one can notice characteristic degenerative changes of eye base that affect, in the initial phase, the posterior side of the eye, and in the developed form, the peripheral parts of retina. This paper points to the potential of application of electrophysiological methods, visual evoked potentials and PERG in assessment of the degree of the degenerative disease and following of its progression.n 15 eyes with high myopia we performed testing by means of visual evoked potentials and „pattern” electroretinogram and compared the received results with the values obtained from the controls. Structured VEP and „pattern” electroretinogram (PERG) was performed on Mistral-Medelec computerized machine; with angle of stimulation CHESS of 30 minutes, screen angle of 15–19 degrees and maximal CHESS contrast. We performed a total of 128 stimulations with use of surface skin electrodes and stimulus frequency of 2 Hz.In patients with high myopia, visual acuity was between 1.0 and 0.1. The average latency value of P-100 waves of PVEP in patients with high myopia was 119.4 msec and was in correlation with the reduction of visual acuity of the researched eye (p<0.05).The average values of P-100 waves amplitudes were statistically significantly lower compared to the control group (3.9 msec).The amplitude values P1 and N2 of PERG were significantly lower compared to the values from the control group (p<0.01). The decrease in amplitude value was in correlation with the decline of visual acuity and the degree of degenerative changes at eye base. Latency values of P1and N2 waves of PERG were slightly prolonged without any statistical significance.Considering that „pattern” electroretinogram maintains electrical activity of inner layers of retina, most of all of ganglion cells, and PVEP records the electrical response of ganglion cells which mostly originate from macula, these methods can, therefore, give us an insight as to the degree of their damage in high myopia. In this way we can use these methods in evaluation of these patients and the assessment of functional retina damage in progressive myopia.
