The Pattern-ERG and Pattern-VEP with variable degrees of central occlusion in unilateral glaucoma patients and glaucoma suspects

Purpose: To determine the sensitivity of a paracentral Pattern-ERG and Pattern-VEP in the identification of dysfunct on in patients known to have, or suspected to have, glaucoma in one eye only. Methods: A reversing (6.1 Hz); black / white (100% contrast); checked pattern (4C min. of arc); extending elliptically 24 degrees superiority, inferiorally and temporally, and 30 degrees nasally; was presented on a computer screen. Pattern-ERG and Pattern-VEP recordings of three averages of 125 reversals were obtained with 3, 6, 12, 18 and 24 degree circular portions of the central fields eliminated. Using the relative amplitudes of the Pattern-ERG P50 and N90, and Pattern-VEP P100; absolute P100 implicit time; rate of decay of P50 and N90 amplitudes with increasing central occlusion; the masked examiner was to identify the abnormal eye. The choice was corroborated with the patient's clinical and perimetric (Humphrey 24-2) data. Results: The most useful parameters in distinguishing the normal from the abnormal eye were the relative P50 amplitudes and the P100 implicit time. Selective stimulation of the paracentral (i.e. arcade region) field did not prove helpful in contrasting the normal from the abnormal eye. Conclusion: Both P-ERG and P-VEP may be helpful in providing objective functional data on patients suspected of having glaucoma on one eye.