The effect of age on binocular functions as measured by stereoacuity, fusion, ocular movements, and ocular alignment

Abstract

Aims: To examine how binocular functions change with increasing age as measured by stereoacuity, motor fusion, ocular movements, near point of convergence (NPC), and ocular alignment. Methods: A preliminary questionnaire survey to establish the professionals’ views on whether age affects distance stereoacuity, fusion and NPC; and what the expected value of stereoacuity was for two age groups using Titmus, TNO and Frisby stereotests. A prospective single-centre cohort study was performed on 77 normal participants aged 10 - 79 years measuring ocular alignment, ocular motility, NPC, motor fusion, and stereoacuity (with Titmus, TNO, Frisby, and Frisby-Davies distance stereotests). Results: The preliminary study results confirmed there was a gap in knowledge regarding any association between age and fusion, and between age and stereoacuity. From the cohort study, all stereotests showed a statistically significant decline in stereoacuity with increasing age (p < 0.05). As age increases NPC declines, this was a statistically significant change (p < 0.05); one year increase in age yielded a 0.032 cm decline in NPC. Age-related changes in positive distance fusion were found- as age increases distance positive fusion declines, which was a statistically significant change (p < 0.05). Age-related changes in positive near fusion, negative near fusion, negative distance fusion, vertical near fusion, vertical distance fusion, ocular alignment, and ocular motility were not found. Conclusions: Overall, stereoacuity was affected by age, but this study challenges the view that other aspects of a binocular vision examination are affected by increasing age. The normative data will provide a baseline from which to compare outcomes in clinical situations.