The Influence of Fixation Stability on Balance in Patients with a Central Scotoma

Abstract

Purpose: Research has shown that visually impaired people (VIPs) often have problems with balance. To compensate for the loss of a functioning fovea, those affected use their remaining peripheral retina to accomplish daily tasks. This sometimes results in the formation of an unstable, non-central fixation point. The purpose of this study was to determine if reduced balance in VIPs is related to unstable fixation.

Methods: Individuals with a visual acuity of 20/400 or better and a diagnosis of a retinal disorder affecting the macula, were recruited for this study. Fixation stability was determined using the Optos Scanning Laser Ophthalmoscope. Functional balance was measured using the Timed Get-Up-and-Go (TUG), the Functional Reach and the Tinetti Balance Test. Balance confidence was assessed using the Activities-Specific Balance Confidence (ABC) Scale. Additionally, postural response to visual information was assessed using a fully immersive virtual environment also known as the CAVE which is equipped with a magnetic motion tracker system capable of measuring postural reactivity by registering body movement. The examiners conducting the balance tests were masked to the fixation status of the participants.

Results: Participants that scored higher on the ABC scale were found to have the greatest fixation stability or the smallest bivariate normal ellipse (BNE). Those with the shortest TUG time were also found to have the smallest BNE. The results of the Functional Reach and the CAVE appear to be related to each other as well. Those able to reach further showed less postural reactivity in response to the CAVE’s 3D environment. Fixation stability showed no relationship with visual acuity or the results of the Tinetti Balance Test.

Conclusions: The results to date show that there may be a relationship between balance and fixation stability. Those with greater fixation stability are able to move faster and have greater confidence in their balance abilities. It appears that fixation stability or more specifically, BNE is a better predictor of balance abilities than visual acuity.