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On‐eye spherical aberration of soft contact lenses and effective lens power
Author(s) -
Dietze H. H.,
Cox M. C.
Publication year - 2002
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1046/j.1475-1313.2002.00086_6.x
Subject(s) - spherical aberration , zernike polynomials , optics , cornea , human eye , wavefront , pupil , contact lens , lens (geology) , paraxial approximation , refractive error , optical aberration , physics , visual acuity , beam (structure)
Purpose: Soft contact lenses (SCL) produce a significant level of spherical aberration (SA). A simple model assuming that a thin SCL aligns to the cornea predicts that these effects are similar on‐eye and off‐eye. We investigate the effect SA has on the power of an SCL on‐eye. Methods: The wavefront aberration for 17 eyes and 33 SCL on‐eye was measured with a Shack–Hartmann wavefront sensor. The Zernike coefficients describing the on‐eye SA of the SCL were compared with off‐eye ray tracing results. Paraxial and effective lens power changes resulting from the SCL‐induced SA were determined. Results: The model predicts the on‐eye SA of SCL closely. The SA induced by spherical SCL partly cancelled the ocular SA for 11 of the subjects. The power change resulting from SCL‐induced SA is ±0.5 D for a ±7.00 D spherical SCL on a 6‐mm pupil. Power change is negligible for SCL corrected for off‐eye SA. Conclusions: For thin SCL the level of SA is similar on‐eye and off‐eye. SCL corrected for off‐eye SA are aberration free on‐eye but the benefit depends on the individual level of ocular aberrations and the viewing condition. The effective power change of spherical SCL depends on pupil size and can be significant for large pupils even for moderate refractive errors. For SCL without aberration correction, for higher levels of ametropia and large pupils, the SCL power should be determined with trial SCL with their power and p ‐value similar to the prescribed lens.