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

To evaluate the diagnostic value of visual evoked potential (VEP) assessment with luminance-contrast and color-contrast stimulation in the detection of glaucoma.

The study included 59 patients (96 eyes) with glaucomatous changes of the optic disc and visual field defects and 58 control eyes of 29 healthy patients. Four types of pattern VEP stimulation (0.9 cycle/degree) were performed in all patients: achromatic, alternating sine-wave stripe pattern: 6 reversals per second, contrast of 10% (activation of predominantly 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).

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 degree in the achromatic VEP. Considering the amplitudes, only the low-contrast red-green stimulus showed a statistically significant reduction in glaucoma. At a predefined specificity of 90%, in separating patients with glaucoma from healthy control subjects, the peak time of the blue-yellow VEP had a high sensitivity (90%), whereas the sensitivity of the achromatic VEP was low (31%). The red-green VEP showed a sensitivity of 73% using low contrast and 71% using high contrast. In a paired correlation analysis with visual field defects, all stimulations showed significant (P < 0.05) results. Correlation coefficients were highest (R = 0.79, P < 0.01) for the peak time of the blue-yellow VEP.

VEP measurements with presumable stimulation of single neuronal pathways can detect glaucomatous optic nerve damage in a considerable fraction 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.