The Effects of Visual Blur on Human Locomotion and Prehension: Investigating the Impact of Second-Eye Cataract Surgery on Skilled Action

Cataract removal surgery is the most commonly performed surgery in the British Health Service. Due to the increasing demands on a stretched healthcare system, access to second-eye cataract removal surgery (SES) is sometimes limited despite a lack of investigation into the effect of the monocular blur associated with a cataract on skilled action.
A systematic review (Chapter 2) was conducted to synthesise the current understanding of the effects of SES on motor function. A narrative synthesis of 13 studies revealed that while SES appears to be associated with a trend towards better motor function, more data from objective measures are needed to reach firm conclusions. To achieve this at a time posing unique logistical challenges, new methodologies to facilitate remote data collection needed to be established. First, it was established that the effect of vision on motor function could be measured remotely (Chapter 3), and online measures of contrast sensitivity and visual acuity were developed and validated (Chapter 4).
A browser-based heading perception test was conducted to better understand the mechanisms underlying the impact of SES on steering. The 49 participants' results indicated that an individual's ability to perceive heading from optic flow significantly reduces under monocular blur conditions with a heavily degraded flow field. This is similar to the benefits associated with SES on nighttime driving. Furthermore, in the first investigation into the effects of visual blur on prehension, monocular blur altered the kinematics of reach-to-grasp movements compared to full vision. Together, these findings indicate the potential benefits of timely SES over first-eye cataract removal (FES). Justifying a future scheme of work investigating how these changes observed in a laboratory setting map onto changes in an individual's ability to perform activities of daily living.