Visual evoked potentials under luminance contrast and color contrast stimulation in glaucoma diagnosis

Purpose: To evaluate the diagnostic value of visual evoked potential (VEP) assessment with luminance-contrast and color-contrast stimulation in the de tection of glaucoma. Patients and Methods: The study included 59 patients (96 eyes) with glaucam atous changes of the optic disc and visual field defects and 58 central eye s of 29 healthy patients. Four types of pattern VEP stimulation (0.9 cycle/ degree) were performed in all patients: achromatic, alternating sine-wave s tripe pattern: 6 reversals per second, contrast of 10% (activation of predo minantly the magnocellular pathway); isoluminant, red-green stripe pattern: 83.3 milliseconds onset, 83.3 milliseconds offset, contrast of 30% and 80% (activation of predominantly the parvocellular pathway); and blue grating with yellow background adaptation: 200 milliseconds onset, 500 milliseconds offset (activation of the blue-sensitive pathway). Results: The glaucoma group and the control group differed significantly (P < 0.01) in the peak times of all chromatic VEP responses and to a lesser d egree in the achromatic VEP. Considering the amplitudes, only the low-contr ast red-green stimulus showed a statistically significant reduction in glau coma. At a predefined specificity of 90%, in separating patients with glauc oma from healthy control subjects, the peak time of the blue-yellow VEP had a high sensitivity (90%), whereas the sensitivity of the achromatic VEP wa s low (31%). The red-green VEP showed a sensitivity of 73% using low contra st and 71% using high contrast. In a paired correlation analysis with visua l field defects, all stimulations showed significant (P < 0.05) results. Co rrelation coefficients were highest (R = 0.79, P < 0.01) for the peak time of the blue-yellow VEP. Conclusions: VEP measurements with presumable stimulation of single neurona l pathways can detect,glaucomatous optic nerve damage in a considerable fra ction of patients with visual field loss. Occipital responses to chromatic stimulation seem to be more sensitive to glaucoma damages than do responses to achromatic pattern reversal stimulation.