Comparison between Humphrey Field Analyzer and Micro Perimeter 1 in normal and glaucoma subjects

To determine the correlation between fundus perimetry with Micro Perimeter 1 (MP1) and conventional automated static threshold perimetry using the Humphrey Field Analyzer (HFA) in healthy individuals and in subjects with glaucoma.

In this study, we enrolled 45 eyes with glaucoma and 21 eyes of age-matched, healthy individuals. All subjects underwent complete ophthalmic examination. Differential light sensitivity was measured at 21 corresponding points in a rectangular test grid in both MP1 and HFA. Similar examination settings were used with Goldmann III stimulus, stimulus presentation time of 200 ms, and white background illumination (1.27 cd/m(2)). Statistical analysis was done with the SPSS 14 using linear regression and independent t-test.

The mean light thresholds of 21 matching points in control group with MP1 and HFA were 14.97 ± 2.64 dB and 30.90 ± 2.08 dB, respectively. In subjects with glaucoma, the mean values were MP1: 11.73 ± 4.36 dB and HFA: 27.96 ± 5.41 dB. Mean difference of light thresholds among the two instruments was 15.86 ± 3.25 dB in normal subjects (P < 0.001) and 16.22 ± 2.77 dB in glaucoma subjects (P < 0.001). Pearson correlation analysis of the HFA and MP1 results for each test point location in both cases and control subjects showed significant positive correlation (controls, r = 0.439, P = 0.047; glaucoma subjects, r = 0.812, P < 0.001). There was no difference between nasal and temporal points but a slight vertical asymmetry was observed with MP1.

There are significant and reproducible differences in the differential light threshold in MP1 and HFA in both normal and glaucoma subjects. We found a correction factor of 17.271 for comparison of MP1 with HFA. MP1 appeared to be more sensitive in predicting loss in glaucoma.