Background: Uncorrected hyperopia is the most common refractive error in childhood. Uncorrected hyperopia places an extra demand on the accommodative system for near tasks and evidence suggests associations between uncorrected hyperopia and abnormal visual development, and poorer academic scores. However, it is still unclear when, and at what magnitude of hyperopia, optical intervention is necessary. Methods: Assessment of sustained accommodative and vergence performance was carried out using photorefraction (PowerRefractor 3™, PlusOptix, Germany) in participants aged 5-10 years with (n=80) and without (n=37) hyperopia. Hyperopia was determined by cycloplegic retinoscopy (1% cyclopentolate) and defined as > +1.00D. Emmetropia was defined as -0.25D to less than +1.00D of cycloplegic refraction. Initially, binocular accommodation measures were obtained without spectacle correction while participants engaged in two sustained near tasks at 25cm: an ‘active’ task (reading small print on an Amazon Kindle), and a ‘passive’ task (watching a stop-clay animated movie on an LCD screen). Both tasks were undertaken for 15-minutes. Measures were repeated after a week with spectacle correction for participants who were hyperopes. Other baseline clinical measures including presenting visual acuity (crowded logMAR letters), stereoacuity (Frisby stereotest) and reading speed (Wilkin’s Rate of Reading test) were assessed. Individual lens calibration slopes were used within the photorefraction data. Results & Conclusion: Results of this PhD work demonstrate that: •Accommodative response during sustained near tasks does not differ significantly between uncorrected hyperopes and emmetropes. •Instability of the accommodative and vergence responses increases with increasing hyperopia. •The instability of accommodative and vergence responses is a factor which is often over-looked and could contribute to asthenopia •Hyperopic spectacle correction is beneficial to optimise the accommodative response.
- Refractive Error
Focussing on Near Work:: the Impact of Uncorrected Hyperopic Refractive Errors
Ntodie, M. (Author). May 2019
Student thesis: Doctoral Thesis