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Assessment of vergence facility in a sample of older adults with presbyopia
1Clinic Research Unit, Victorian College of Optometry, Carlton, Australia.
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:
Vergence facility was measured in a sample of 50 asymptomatic subjects with a mean age of 58.7 years using 8delta base-in (BI) and 12delta base-out (BO) prisms mounted in clinical flipper frames. Testing was performed for 1 min on four separate occasions over the course of a few weeks.
Results:
Of the 42 subjects that completed the study, vergence facility could be satisfactorily measured on only 21 subjects. The mean vergence facility for this group was approximately 7 cycles per minute (cpm), commensurate with previous results in younger subjects using a similar paradigm. There were no differences in vergence facility between the first and second 30-s periods of testing, nor were there any 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 presbyopia.