Abstract
Purpose::
To evaluate test-retest variability (TRV), long term fluctuation (LF) and the learning effect (LE) in normal subjects tested with the Rarebit Perimetry (RP).
Methods::
This is longitudinal study. One eye was randomly chosen from 25 healthy subjects (normal visual field, untreated IOP below 21 mmHg, no family history of glaucoma). All were free of ocular disease and the refractive errors ranged between +5 and -7 diopters. All the subjects were examined with Rarebit Perimetry (RP), program ‘rabbit test’. Each subject was tested once in the first session, three times in the second session and once in the third and fourth sessions. The TRV was evaluated analyzing the three visual fields of the second session, while for the LF the first exam of each session was utilized. Both TRV and LF were studied as the average fluctuation values of all the indices tested or as a point-wise fluctuation. To study the LE, the results of the first session were compared with those of the second, the third and the fourth session. Mean hit rate in percentage (MHR%), mean hit rate standard deviation (MHRsd), number of hit rate (num HR), hit rate in percentage (HR%), hit rate standard deviation (HRsd), time and mean rate time (MRT) were used in this study.
Results::
LF and TRV ranged from 0.06 to 3.28 dB for all the RB indices. When the point-wise fluctuation was analyzed, the values ranged from 1.79 dB + 3.84 to 9.38 dB + 6.46 for TRV and from 1.86 dB + 3.26 dB to 11.37 + 8.44 for LF. A learning effect was present in the first session for MHR%, MHRsd and num HR.
Conclusions::
TRV and LF and were similar to those known to occur with the conventional threshold perimetry when they were compared to the literature data. A learning effect was present in the first session for MHR%, MHRsd, numHR and it should be taken into account for the clinical use of this test.
Keywords: visual fields • perimetry • receptive fields