Rarebit perimetry: normative values and test–retest variability


Dr. Chee-Fang Chin, 11 Jalan Tan Tock Seng, Tan Tock Seng Hospital, Singapore 308433. Email: chee_fang@yahoo.com


Background:  We aim to establish normative values and evaluate test-retest variability for the central and foveal field tests of version 4 of rarebit perimetry.

Design:  This was a prospective study undertaken in collaboration between Tan Tock Seng Hospital, Singapore, and Singapore Polytechnic.

Participants:  Fifty-four normal subjects were recruited and included in the study.

Methods:  Subjects underwent rarebit perimetry testing, studying the central and foveal fields. All subjects repeated the test within 1 month of the initial visit. The ‘mean hit rates’ of one eye of every subject were analysed.

Main Outcome Measures:  Mean hit rates of subjects were analysed to establish normative values for the central and foveal fields. Test-retest variability was also analysed.

Results:  Overall normative mean hit rates were 86.3 ± 13.95% for the central field and 91.6 ± 6.35% for the foveal field. For every increasing year of age, we found a 0.47% decrease in the central mean hit rates (P < 0.001). Normative mean hit rate for central and foveal fields were 90.6 ± 12.3% and 98.2 ± 3.7% respectively, in ‘young’ subjects, and 81.9 ± 15.6% and 85.0 ± 9.0% respectively, in ‘mature’ subjects. We found no significant test–retest variability in the foveal field (P = 0.554). There was significant test–retest variability in the central field (P < 0.001), but the difference was a 3.5 unit mean hit rate increase, which may be clinically significant.

Conclusions:  Rarebit perimetry is repeatable and reliable. We have established normative values for two age groups.