Published on www.nkcf.org by Shelley I. Cutler, OD, FAAO

Keratoconus is managed by many different contact lens designs. No one design is best for every type of keratoconus. Since each lens design has its own unique characteristics, the practitioner carefully evaluates the needs of the individual situation to find the lens that offers the best combination of visual acuity, comfort and corneal health.

The following is a list of the lens designs available for keratoconus.

Standard rigid lens designs are the simplest fitting choices and achieve their best level of success in early or mild KC. They are generally spherical in curvature and can achieve excellent fitting profiles with sharp clear visual results.

Aspheric lens designs gradually flatten from the center toward the periphery, approximating the steep cone vs. flat periphery curvature relationship seen in keratoconus. These designs are indicated for small to moderate nipple cones. The goal of this lens is to vault the apex of the cone, or lightly touch it, and align the more normal peripheral cornea. Because the nature of an aspheric lens allows for plus power in the periphery, presbyopic keratoconics may find this lens preferable if the fit is acceptable. The lens needs to center for the optics to work.

• ComfortKone™ by Metro Optics is a tri-aspheric lens.

• Contex, Inc. has eight aspherical designs available for KC.

• Ellip-See-Con®-K and the Multi-Curve Sphere are aspheric lens by Conforma.

• Epicon lens is a large, semi-scleral lens made of a new material called carbosilfocon. It is a moldable, flexible material with the health benefits of an RGP lens and comfort approaching that of a soft lens. It is distributed by Specialty Ultravision.

• Flexlens Tricurve Lens is a soft contact lens designed with a thick center that creates more rigidity to maintain visual acuity.

• Flexlens Piggyback Lens is a two lens system: a soft lens that rests on the cornea, with a center area hollowed out to accommodate a small RGP lens.

• Infinity Cone by Infinity Optical, Inc. is designed to fit the periphery of the lens on the outer edge of the cornea as far away from the cone protrusion as practical.

• Macro lens by C & H Contact Lens, a modification of a scleral lens, is slightly smaller than a scleral lens but larger than a corneal lens.

• McGuire lens system, a modification of Soper's design, was introduced in 1978. It is manufactured with a number of blended curves on the back surface of the lens.

• Menicon Decentered OZ design has four spherical curves on the back surface of the lens with the optical zone decentered approximately 1mm. This is a good design for a low, sagging cone.

• NiCone Lens, patented in 1986, is available from Lancaster Contact Lens, Inc. It is a multiple back surface vaulting system.

• Piggyback lens system consists of two lenses – a soft lens that rests against the cornea and an RGP lens worn right over it.

• Porus K ™ by Lens Mode, has a smaller lens diameter that fits over the apex of the cone.

• Rose K is a lens design with a complex, computer generated peripheral curve system designed by Dr. Paul Rose of Hamilton, New Zealand. It is distributed by Lens Dynamics, Inc.

• SoftPerm lens (replaced the Saturn lens) has a rigid center made of RGP material and soft outer rim, or skirt, made of soft lens material. It is available now from CIBA.

• Soper Cone was introduced in the mid 1970's. This is a bicurve contact lens. As the curvature is increased for a given diameter the vaulting effect of the lens is also increased.

• Valley K, by Valley Contax, is a unique design modified after the McGuire lens. Instead of the 4 blended peripheral curves, there are computer-lathed curves halfway in between the basic McGuire curves creating an almost aspheric periphery.

• Super Nova KC, by Innovations In Sight, Inc. is a soft, tri-curve lens design with a thick center that allows the lens to maintain its shape on the irregular corneal surface.

• Scleral (or Haptic) lenses have been around since the 1800’s. With the development of highly oxygen permeable polymers they are again becoming an option for KC. This is a large lens that rests on the sclera (the white part of the eye) and vaults over the cornea with little or no touch. This lens is more popular in Europe than in the US.

• Computer assisted contact lens designs are available from some laboratories. Because they are designed from corneal topography, and the keratoconic cornea can have changes in curvature that are too detailed for the corneal map to reveal, this type of design may or may not work when the lens is placed on the eye and interacts with the ocular environment.

Dr. Cutler is a Contact Lens Consultant and Adjunct Faculty Member at the Pennsylvania College of Optometry and works in a corneal practice specializing in difficult contact lens fits. She has lectured nationally and internationally on various contact lens related topics.