Comparison between MP-1 and Humphrey visual field defects in glaucoma and retinitis pigmentosa

To compare MP-1 microperimeter and Humphrey Field Analyzer (HFA) defects, in patients with retinitis pigmentosa (RP), a disease primarily affecting the photoreceptors, and in patients with glaucoma, a disease primarily affecting postreceptoral ganglion cells, and to analyze the similarities and differences between the results.

Eleven patients (11 eyes) with RP and 10 patients (10 eyes) with primary open-angle glaucoma (OAG) underwent MP-1 and HFA visual field testing (10-2 pattern). All tested eyes had defects encroaching within 10° of fixation. MP-1 total deviation (TD) probability defects, derived from a previously collected normative database of 50 subjects, were compared to HFA TD defects and to the local defect map of the MP-1. Test duration was compared between instruments.

In RP patients, MP-1 scotomata were deeper and wider than HFA defects; however in OAG, the opposite was observed. Examination duration in both patient groups was 12 to 14 min for the MP-1 and 6 min for the HFA. The MP-1 local defect map tended to overestimate defects compared to the MP-1 TD analysis.

The differences in results between the MP-1 and HFA for the two groups of patients with RP and OAG can be attributed to the different adaptation levels and to the dynamic range of test lights available for the two instruments. The clinician should also be aware of the possible consequences of the differences in the method of derivation of normative data for the two instruments, as this may affect the interpretation of visual field results.