Foveal vision power errors induced by spectacle lenses designed to correct peripheral refractive errors

• Main Author: Barbero, Sergio
• Publication Date: 2018
• Other Authors: Ribeiro, Miguel António Faria
• Format: Article
• Language: eng
• Source: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Download full: http://hdl.handle.net/1822/54721
• topic: Radial Refractive Gradient (RRG) spectacles; Spectacles lens design; Spectacles power errors; Ciências Naturais::Ciências Físicas; Science & Technology

Purpose: Radial Refractive Gradient (RRG) spectacles are lenses specifically designed to minimize peripheral hyperopic defocus typically found in conventional spectacles. Our goals were: (1) to demonstrate a method to design such lenses; and (2) to quantify the exact foveal vision power errors induced by them. Methods: The design procedure was based on a point-by-point sequential surface construction algorithm that designs a front aspheric surface (back surface is spherical) to achieve a given overall tangential focal length of the lens. A peripheral refraction model was built based on average peripheral refractive errors from a set of eyes. We designed four negative lenses with optical powers: 2.5, 5.0, 7.5 and 10.0 D, so that the tangential focal length of the lens matches the retinal conjugate surface. Results: The lenses induce very small sagittal power errors in a wide range of offaxis field angles (30°), solving the problem of peripheral hyperopic defocus. However, such designs introduce non-negligible mean power errors (above 0.25 D from 7°, 6.8°, 7.1° and 7.8° for the 2.5, 5.0, 7.5 and 10.0 D lenses, respectively) for foveal vision in a rotating eye. Conclusion: Our results show the unavoidable errors introduced by RRG spectacles when used for dynamic foveal vision. The described method offers valuable information towards determining the best trade-off between controlling power errors for peripheral and foveal vision.