ASSESSMENT OF VERGENCE FACILITY IN A SAMPLE OF OLDER ADULTS WITH PRESBYOPIA

Purpose. The aim of this study was to establish whether assessment of vergence facility is clinically useful in older adults with presbyopia and to determine pilot normative data for this age range. Methods. Ve rgence facility was measured in a sample of 50 asymptomatic subjects w ith a mean age of 58.7 years using 8(Delta) base-in (BI) and 12(Delta) base-out (BO) prisms mounted in clinical flipper frames. Testing was performed for 1 min on four separate occasions over the course of a fe w weeks. Results. Of the 42 subjects that completed the study, vergenc e facility could be satisfactorily measured on only 21 subjects. The m ean vergence facility for this group was approximately 7 cycles per mi nute (cpm), commensurate with previous results in younger subjects usi ng a similar paradigm. There were no differences in vergence facility between the first and second 30-s periods of testing, nor were there a ny differences in average vergence facility over the 4 test occasions. Test-retest repeatability, however, was poor. The BI prism phase took longer, on average, to fuse than the BO prism phase (BI 5.2 s and BO 3.7 s). Conclusions. Our results show a high degree of variability in vergence facility in older subjects with presbyopia. More research is required before deciding whether measurements of vergence facility are of use in investigating binocular vision of older patients with presb yopia.