Ocular motor triad with single vision contact lenses compared to spectacle lenses

Abstract 

Aim

Theoretically myopes are required to exert more accommodation and vergence when wearing single vision contact lenses compared to glasses and hypermetropes less. This study aims to quantify the effects clinically.

Method

Thirty subjects (21 female, nine male, average age 21.0±2.2 years) with a range of refractive errors (−7.87D to +3.50D) viewed in a random order, static targets at 0.1, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0D accommodative demand that were matched for angular subtense. The subjects were fully corrected with spectacles and daily disposable contact lenses to their full prescription. Accommodation was monitored objectively with the PowerRefractor and Shin-Nippon SRW5000 and vergence and pupil size with the PowerRefractor.

Results

Myopes exerted greater accommodative effort for viewing near targets with contact lenses than glasses and hypermetropes less (r²=0.35, p=0.001 PowerRefractor). Myopes also exerted greater vergence effort for viewing near targets with contact lenses than glasses and hypermetropes less (r²=0.22, p<0.01).

Conclusion

Theoretical calculation of the accommodative and vergence requirements with glasses compared to contact lenses reflect clinical findings, although there is reasonable variability between individuals.

Keywords: Accommodation, Vergence, Photoretinoscopy, Myopia, Hypermetropia