Many types of irregular corneal conditions benefit from contact lens wear. Below the topographical cross-section images provided by the Pacific University College of Optometry demonstrate the appearance of keratoconus, pellucid marginal degeneration and globus keratoconus in comparison to a normal cornea.
The most common lenses for keratoconus and other irregular cornea situations are below. Although the ectatic eyes are steeper in areas, it is actually the irregularity of the surface that is the cause for a decrease in patient visual acuity. Historically, it has been accepted that a rigid lens was needed to optically correct these situations by creation of a tear layer posteriorly while the smooth, polished anterior lens becomes the "new" initial refracting surface of the eye.
Some soft lenses can also supply this effect but it necessitates a steep, thick lens to achieve this. That is, until today. The KeraSoft® IC lens employs a very large posterior fitting zone that drapes over the whole cornea and has limited tear layer effects – instead the aspheric or aspheric toric anterior optic zone provides for vision improvement.
Soft Lenses and Irregular Corneas
Specialty soft lenses can be used in cases of:
- Naturally occurring ectasia
- Post Intacts and Corneal Cross-linking
- Post-surgery ectasia
- Post corneal graft
- Intolerance to other lens systems
Today’s soft lenses and scleral GP lenses work by fitting over the “whole” cornea, limbus and onto the scleral. GP corneal lenses are designed to fit only over the “steepest” portion of the cornea.