At Zacks Eye Clinic in central London we have optometrists who specialise in treating keratoconus with specialist contact lenses.
Keratoconus is a degenerative condition of the eye whereby the cornea (the transparent front part of the eye) becomes cone-shaped causing visual distortion. The condition typically presents in adolescent years affecting one eye worse than the other and affects approximately 1 in a 1000 people. Keratoconus has been shown to run in certain families and environmental factors have been thought to trigger its onset. Diagnosis is confirmed by mapping the front surface of the eye with a corneal topographer.
Refractive Treatment for Keratoconus
In the early stages of keratoconus, spectacles or soft contact lenses can correct the mild astigmatism. As the condition progresses, rigid, gas-permeable contact lenses, (RGP) and other more specialist contact lenses can provide a good level of visual correction, but do not slow down progression of the cone. Surgical techniques can sometimes help in the more advanced stages.
Soft Contact Lenses for Keratoconus
Soft contact lenses tend to be very comfortable, however they wrap around the eye conforming to the front surface so usually don’t provide the best visual correction for keratoconus. Special soft contact lenses designed especially for keratoconus are thicker than regular soft lenses in order to retain their shape. Recently they have become available in silicone hydrogel materials which are very oxygen permeable.
Rigid Gas Permeable Contact Lenses (RGP’s) for Keratoconus
Rigid Gas Permeable contact lenses work by holding tear fluid in the gap between the irregular corneal surface and the rigid back surface of the contact lens to neutralise the irregular front surface of the eye. They are available in extremely permeable materials and often provide the best level of vision for keratoconic patients, so are most frequently fitted as a first choice option when keratoconus has been detected.
Hybrid and Piggyback Contact Lenses for Keratoconus
Hybrid and piggyback designs combine the comfort of a soft lens with the visual acuity of an RGP lens. Hybrid designs have an RGP centre with a soft surround whereas piggyback fitting places an RGP lens on top of a soft lens. The latest materials mean that these systems can now be used to treat the majority of patients with keratoconus more effectively than ever before.
Scleral Contact Lenses for Keratoconus
Scleral contact lenses are very large rigid gas permeable contact lenses which fit onto the sclera or white of the eye. They are useful for cases of advanced or irregular keratoconus and usually offer improved stability and comfort. These lenses can also be used to treat other conditions, such as dry eye.
Mini Scleral/Semi Scleral Contact Lenses for Keratoconus
Semi-scleral RGP lenses are bigger than a conventional corneal RGP lens and smaller than a full scleral lens. They can provide good vision with a stable, comfortable fit, vaulting over the cornea. Light in weight, high in oxygen permeability and easy maintenance often makes them an appealing option for keratoconic patients.
Cross-linking for Keratoconus
Corneal collagen crosslinking with riboflavin, also known as CXL, CCL, Holcomb C3-R and KXL has shown success in retarding or stopping progression of keratoconus by increasing the cornea’s mechanical strength.
Intrastromal corneal ring segments for Keratoconus
The principal intra-stromal ring available is known by the trade name Intacs. Internationally, Ferrara rings are also available. The segments push out against the curvature of the cornea, flattening the peak of the cone and returning it to a more natural shape.
Keraflex (Avedro, Inc.) (Microwave thermokeratoplasty)
Microwaves cause collagen fibres to shrink, producing corneal flattening. Riboflavin drops are then administered over the treatment area and ultraviolet light is administered to crosslink the corneal collagen and maintain the flattening.
Penetrating Keratoplasty refers to the replacement of the host cornea with a donor cornea. It may be considered in cases of severe cornel scarring, where less invasive treatment has failed.
Contact lenses are usually required after corneal surgery to achieve good visual acuity and a new fitting is required.