Influence of accommodation and refractive status on the peripheral refractive profile
- 1Ophthalmic Research Group, School of Life and Health Sciences, Aston University, Birmingham, UK
- 2Bradford School of Optometry and Vision Science, University of Bradford, Bradford, UK
- Correspondence to Dr L N Davies, Ophthalmic Research Group, School of Life and Health Sciences, Aston University, Birmingham B4 7ET, UK;
- Accepted 28 April 2009
- Published Online First 11 June 2009
Aim: The aim of the study was to determine, objectively and non-invasively, whether changes in accommodative demand modify differentially the peripheral refraction in emmetropic and myopic human eyes.
Methods: Forty subjects (19 male, 21 female) aged 20–30 years (mean 22.7 (SD 2.8) years), 21 emmetropes (mean spherical equivalent refractive error (MSE) −0.13 (SD 0.29) D) and 19 myopes (MSE −2.95 (SD 1.76) D) participated in the study. Ametropia was corrected with soft contact lenses (etafilcon A, 58% water content). Subjects viewed monocularly a stationary, high contrast (85%) Maltese cross at 0.0, 1.0, 2.0 and 3.0 D of accommodative demand and at 0, 10, 20 and 30° field angle (nasal and temporal) through a +3.0 D Badal optical system. Static recordings of the accommodation response were obtained for each accommodative level, at each field angle, with an objective, open-view, infrared optometer.
Results: Peripheral mean spherical equivalent (M) data showed that the emmetropic cohort exhibited relative myopic shifts into the periphery, while the myopic group showed hypermetropic shifts. Increasing accommodative demand did not alter the peripheral refractive profile in either the temporal (p = 0.25) or nasal (p = 0.07) periphery with no differential accommodative effect between refractive groups in either the temporal (p = 0.77) or nasal (p = 0.73) field. Significant shifts in the J0 astigmatic component were seen in the temporal (p<0.0005) and nasal (p<0.0005) fields with increasing eccentricity. Interaction effects between eccentricity and accommodative demand illustrated that increasing accommodative demand significantly altered the peripheral refractive profile in the temporal J0 astigmatic component (p<0.0005). The nasal periphery, however, failed to show such an effect (p = 0.65).
Conclusions: Alterations in peripheral refraction augmented by changes in ocular accommodation are relatively unaffected by refractive error for young, healthy human eyes.
Competing interests The authors do not have any proprietary or financial interests in any of the devices or methods presented herein.
Provenance and Peer review Not commissioned; externally peer reviewed.
Ethics approval All procedures were carried out in accordance with the tenets of the Declaration of Helsinki, and were approved by the Institutional Human Research Ethics Committee.
Patient consent Obtained.