Topographic evaluation of toric soft contact lens correction.

The anterior surface of the eye provides the greatest refracting surface to the optical system of the eye because of the large difference in refractive index between air and tissue. When a contact lens is placed on the eye, its anterior surface becomes the greatest refracting surface. Toric soft contact lenses have been designed to neutralize ocular astigmatism. We observed that topographic analysis of toric soft contact lenses on an astigmatic eye demonstrated residual astigmatism on the anterior surface of soft toric contact lenses. In this paper we show toric soft contact lens surface astigmatism by videokeratoscopy and interpret the origins of the astigmatism.

Surface topography of soft contact lenses for neutralizing corneal astigmatism.

We compared the surface topography of 38 soft contact lenses in situ to the corneal topography of 17 patients. The analyzed lenses consisted of patients' spherical and toric lenses as well as additional spherical lenses of various thicknesses. Thirteen brands of contact lenses were worn; corneal astigmatism ranged from 0.12 to 3.81 D. Our hypothesis was that toric soft contact lens neutralization of corneal surface astigmatism occurred through the creation of a more spherical anterior surface. Videokeratoscopy was used to analyze corneal surface changes with contact lens wear. The correction of astigmatism for toric corneas (toricity > 0.75 D) fit with toric lenses (i.e., the difference between the surfaces of the cornea and anterior lens) showed surface astigmatism neutralization of only 34 +/- 38%. The greater the astigmatism, the greater the neutralization. Spherical lenses not only failed to mask corneal toricity, but actually increased it. The topographic map can be a valuable asset for analyzing and possibly improving contact lens fitting of toric contact lenses.

Rigid gas permeable contact lens correction of aphakia following congenital cataract removal during infancy.

Rigid gas permeable (RGP) contact lenses were prescribed and worn with little difficulty by 10 consecutive aphakic infants. Fluoroperm 92 lenses were used instead of silicone lenses (Bausch & Lomb) because of their lower cost, ease in handling, flexibility in design, and better neutralization of astigmatism. Lenses were worn on a daily wear basis (with occasional overnight wear) to reduce the risk of keratitis. Keratometry readings were taken at the time of surgery with the patient in a supine position. Trial lens fitting was performed 1 to 7 days later using a Burton Lamp. None of the patients developed keratitis, corneal neovascularization, or the sucked-on-lens syndrome. The lenses were well tolerated and the parents soon became adept at handling them. We now use RGP lenses as our lens of choice when treating aphakic infants.