Pantoscopic tilt in spectacle-corrected myopia and its effect on peripheral refraction.

Spectacles are a common option for the correction of myopia in children and young adults. Visual scientists striving to explain the process of emmetropization and myopia progression have been interested in peripheral refraction, as well as on-axis performance. Using a ray tracing technique and mathematical eye models for myopia, this study assessed the effect of pantoscopic tilt on peripheral refraction in spectacle-corrected myopia. At the centre and throughout the periphery of corrected models, hyperopic shifts in the mean spherical equivalent component were found in all meridians. Horizontally, hyperopic shift tends to incline uniformly with the increase in pantoscopic tilt, but this did not occur in the other meridians. No change in the trend of the horizontal J180 refraction component was found with changes in pantoscopic tilt among all myopic errors. The J45 component produced considerable shifts in the horizontal periphery, which increased with increase in pantoscopic tilt. The ray tracing technique provides considerable information about the relationship between peripheral refraction and aberrations, with the tilt of the correcting spectacle lens. Larger degree of tilt on high myopic prescriptions seems to produce considerable non-uniform, hyperopic shifts, along with astigmatism and coma, in the peripheral visual field. These effects may be sufficient to play a role in the progression of myopia; however, further studies are required to fully understand this relationship.