Abstract
Purpose :
To evaluate the impact of different types of peripheral refractive errors (positive, negative and cylindrical) when subjects perform a functional test of ascending and descending steps.
Methods :
A circular hole subtending 32-degree over the retina was practiced on the surface of four types of ophthalmic lenses: i) plano lenses (null dioptric power), ii) positive and negative lenses (±2 D and ±4 D) and iii) oblique cylindrical lenses (+2 D and +3 D) oriented at 45-degree. The lenses were mounted over standard frames with the hole aligned to the particular line of sight of six subjects, allowing intact vision across the 32-degree central field and inducing a variety of refractive errors in the rest of the peripheral visual field. The task for the subjects was to negotiate a floor obstacle consisting of two ascending steps (13 cm high each), an elevated platform (1 m long) and two descending steps (equal high as the ascending steps). Each subject performed four trials with each spectacle. A camera equipped with a fish-eye lens captured the movement (at 110 Hz) of the subjects’ feet navigating the obstacle. Two LEDs were attached to subjects’ shoes to mark the feet trajectories. Kinovea software was used to track the LED trajectories that were exported and analysed using Mathematica software.
Results :
Average navigation times through the obstacle (with respect to the case of plano lenses) were a 15% (SD ±13%) and a 5% (SD ±10%) slower when subjects wore the +4 D and +2 D lenses respectively. Similarly, with the cylindrical lenses, navigation times were 18±19% (+3 D) and 6±9% (+2 D) slower than with plano lenses. However, with the -2 D negative lenses, navigation times did not increase with respect to plano lenses (-1±9%) and they barely increased with the stronger -4 D negative lenses (6±11%). Kinematic analysis of the trajectories showed a more cautious gait approach (more steps, slower gait) and more foot misplacements when wearing the positive and cylindrical lenses than with negative lenses.
Conclusions :
Superimposed positive and cylindrical peripheral refractive errors had instantaneous effects on functional vision when negotiating steps. These data may be relevant when considering the potential effect in daily activities of increased peripheral refractive errors in cataract patients after implantation of standard intraocular lenses.
This is a 2021 ARVO Annual Meeting abstract.