Test-Retest Variability of Multifocal Visual Evoked Potential and SITA Standard Perimetry

Abstract

Abstract: : Purpose: To investigate pointwise test-retest variability of objective perimetry using multifocal visual evoked potential (mfVEP) and subjective perimetry. Methods: mfVEP data were recorded using the AccuMap (ObjectiVision, Sydney, Australia; Version 1.0) and visual field data were recorded using Humphrey Field Analyzer (HFA) (program 24-2, SITA standard). The data were obtained twice within a 6-week period from both eyes of 74 patients (42 males and 32 females) aged 69.80 +/-10.00 years (mean +/- SD) with a range of glaucomatous visual field loss (mean defect -7.64dB, range +1.86 to -28.69dB). The AccuMap system presented a pseudo-random cortically scaled pattern stimulus at 58 locations out to an eccentricity of 32 degrees. For each location the probability of the amplitude falling within the normal range was calculated using the manufacturer's software and normative database. The HFA central 24-2 program presented stimuli at 52 locations. For each location the pattern deviation value was extracted from the visual field chart. Test-retest limits for the number of test locations reaching a given probability value were determined for mfVEP and SITA. The time taken to perform mfVEP was recorded in a subset of patients (n=24) and all patients were asked for their test preference. Results: Both tests showed a large degree of variability with the 95% limits of agreement being slightly larger for mfVEP than SITA (13.57 and 9.88 test locations respectively). The mean time (+/- SD) taken to perform mfVEP was 33.60 +/- 3.02 minutes. Typically SITA takes approximately 20 minutes despite this 73 of the 74 patients preferred the mfVEP test. Conclusions: The test-retest variability was found to be slightly larger for mfVEP than for SITA in an unselected population of patients with glaucoma. The majority of patients preferred the mfVEP to a visual field test although the mfVEP takes longer to perform.

Keywords: perimetry • electrophysiology: clinical • visual fields