Limitations of correcting spherical aberration with aspheric intraocular lenses.

Purpose: Aspheric intraocular lenses (IOLs) are deigned to correct spherical aberration in pseudophakic eyes. We predict the benefit from correcting spherical aberration based on simulations and aberrometry of pseudophakic eyes implanted with spherical IOLs.

Methods: Ray tracing was performed through a model eye with an equi-biconvex spherical IOL and with a spherical aberration-correcting aspheric IOL.

Correcting ocular spherical aberration with soft contact lenses.

Following aberroscopy, aspheric front surface soft contact lenses (SCLs) were custom-made to correct spherical refractive error and ocular spherical aberration (SA) of 18 myopic and five hypermetropic subjects (age, 20.5 +/- 5 yr). On-eye residual aberrations, logMAR visual acuity, and contrast sensitivity were compared with the best-correcting spectacle lens, an equally powered standard SCL, and an SCL designed to be aberration free in air.

Verification of aspheric contact lens back surfaces.

Purpose: To suggest a tolerance level for the degree of asphericity of aspheric rigid gas-permeable contact lenses and to find a simple method for its verification.

Methods: Using existing tolerances for the vertex radius, tolerance limits for eccentricity and p values and were calculated. A keratometer-based method and a method based on sag measurements were used to measure the vertex radius and eccentricity of eight concave progressively aspheric surfaces and six concave ellipsoidal surfaces.

On- and off-eye spherical aberration of soft contact lenses and consequent changes of effective lens power.

Background: Soft contact lenses produce a significant level of spherical aberration affecting their power on-eye. A simple model assuming that a thin soft contact lens aligns to the cornea predicts that these effects are similar on-eye and off-eye.

Methods: The wavefront aberration for 17 eyes and 33 soft contact lenses on-eye was measured with a Shack-Hartmann wavefront sensor.