Purpose: To test the ability of multi-focal objective perimetry (MOP) to detect glaucomatous field defects.
Method: The ObjectiVision System provided different random patterns to each of 58 points extending out to 32 degrees nasally. A multichannel visual evoked potential (VEP) was recorded (occipital cross electrodes, 7 mins/eye). 100 patients with confirmed glaucomatous visual field defects (age 61.7+/-14.8, mean MD -6.6+/-4.3) were tested and compared to the normal data base of 100 normals (age 58.9+/-10.7). If both eyes had a field defect the eye with the lesser defect was chosen for the purpose of determining sensitivity. The amplitude and inter-eye asymmetry coefficient for each point of the field was calculated and a severity score was derived for each subject.
Results: In 95/100 glaucoma cases (95%) the Humphrey field defects were demonstrated by VEP amplitude reductions identifying a cluster of 3 or more abnormal points (with at least 2 points p<0.02). Two more cases were identified on pattern deviation plots only while in one further case with early glaucoma, inter-eye asymmetry analysis identified the field defect. Topographic location was strongly correlated with Humphrey fields. In 37 glaucoma cases the fellow eye had a normal visual field. In 21 (56.7%) of these cases the MOP showed a defect in the second eye on one or both analyses. The severity index score showed a good correlation with Humphrey MD (r=0.67 right eyes, r=0.69 left eyes, r=0.42 eyes with lesser defect).
Conclusions: MOP can objectively map the visual field and identify glaucomatous visual field defects. It may have the potential for identifying defects earlier than white-on-white perimetry.