Balance is essential for healthy aging, as studies have linked poor balance to an increased risk of falls, nursing care admissions, and mortality. Balance is regulated by multiple systems, including also the visual system. According to researches, as people get older, the visual system plays a bigger role in maintaining postural stability. However, in older ages, vision impairment becomes increasingly widespread, leaving visually impaired seniors without proper postural control.
Studies have found a link between poor vision and worse balance. Many population-based studies, for example, have found a relationship between various measures of visual function (e.g. visual acuity, visual field, and motion detection threshold) and balance issues. Patients with glaucoma, cataract, or age-related macular degeneration (AMD) showed worse balance.
The result of this Canadian longitudinal study showed that visual acuity is associated with failing the balance test even after adjusting for a self-report of cataract, glaucoma, or AMD, indicating that other ocular factors may affect balance. They also discovered that persons who said they had had cataract in the past (whether it was removed or not), were more likely to fail the balance test three years later. Surprisingly, they did not find any linkage between AMD or glaucoma and failure on the balancing test, however, this could be due to their self-reporter nature or the fact that most cases were mild or early stage.
Even after adjusting for cataract, AMD, and glaucoma, visual acuity was linked to failing the balancing test, suggesting that uncorrected refractive error may be the cause. Uncorrected refractive error, the most common cause of vision loss worldwide, has previously been linked to balance. Using cross-sectional data, Willis and colleagues discovered that both visual impairment owing to uncorrected refractive error and visual impairment due to reasons other than uncorrected refractive error were linked to balance test failure.
The failure of the balancing test was also linked to cataracts. Surprisingly, individuals who had a cataract removed had the highest chance of failing the balancing test, followed by those who still had a cataract in their eyes. Cataract surgery not only eliminates the cataract but also corrects the refractive error in that eye to a significant extent by inserting a correct-power intraocular lens. There are various possible explanations for why we discovered that cataract surgery was linked to decreased balance. Firstly, there is a period of time between first-eye and second-eye cataract surgery that might result in a person’s eyes having drastically differing refractive abilities. Glasses can be used to fix this. If people are hesitant to pay for new glasses during this time and instead wait until after the second-eye cataract surgery, they may experience unequal refractive powers in both eyes and impaired stereopsis, which can lead to poor balance. However, even when the difference in visual acuity between the two eyes was taken into account, the link between cataract removal and the development of balance issues remained. Secondly, even after second-eye cataract surgery, a person may have some residual refractive defect that cannot be fully repaired. 77 % of patients who were advised by their surgeons to get distance correction spectacles did so. Adjusting for visual acuity, on the other hand, had no effect on the link between cataract removal and subsequent balance issues. Third, those who have had cataract surgery may have other visual changes that influence their balance. We didn’t have data on measures of visual function other than acuity, such as contrast sensitivity, visual field, or motion detection, even though we accounted for AMD and glaucoma and the association remained unchanged. Finally, those who have had their cataracts removed may have other health issues that impair their balance. Adjusting for ADL impairment, diabetes, and stroke did not affect the relationship much. We were eventually unable to determine why persons who had cataract surgery were more prone to experience balance issues.
To summarize, visual impairment is associated with the start of balance issues. These findings suggest that patients with vision loss should pay more attention to balance issues and that interventions to improve balance should be considered in groups with irreversible vision loss.
Source: Kahiel, Z., Grant, A., Aubin, M. J., Buhrmann, R., Kergoat, M. J., & Freeman, E. E. (2021). Vision, Eye Disease, and the Onset of Balance Problems: The Canadian Longitudinal Study on Aging. American Journal of Ophthalmology, 231, 170–178. https://doi.org/10.1016/j.ajo.2021.06.008