Keratoconus is one of the more challenging yet more rewarding conditions that we treat in our offices. Individuals with keratoconus have a thinning of their corneas that causes a protrusion and irregular steepening. This creates an irregular surface that inappropriately focuses light on the retina even with the best refractive correction.
Although corneal crosslinking is a treatment to prevent progression, often these individuals will still be left with irregular astigmatism that needs to be corrected.
Starting points of treatment
In milder cases of keratoconus, simply correcting the refractive error with a standard soft toric contact lens may correct vision to levels that are adequate for the patient. Standard soft contact lenses are often prism ballasted and thus have a thicker profile than a standard spherical lens.
Previously from Dr. Brujic and Dr. Kading: Glasses and contact lenses: Have they become a commodity?
Soft contact lenses help improve some of these patients’ vision better than what can be obtained through a standard spectacle lens. As keratoconus progresses, there are other options to correct vision. Soft contact lenses specifically designed to correct keratoconus and the higher order aberrations associated with them are available in both hydrogel and silicone hydrogel options.
When a soft contact lens doesn't improve vision to adequate levels, we consider a corneal gas permeable (GP) contact lens. Theses lenses create a more regular surface by masking many of the irregularities that the keratoconic cornea naturally contains.
Because of their small diameter, GP lenses are relatively easy to place on the eye—even for neophyte wearers. Additionally, there is adequate tear exchange for appropriate corneal support with corneal GP lenses, but there may be initial lens awareness.
Contemporary corneal GP lenses, which are slightly larger than traditional corneal GP lenses, have helped alleviate initial symptoms of keratoconus. Hybrid lenses with a gas permeable center and scleral lenses can introduce GP optics without the initial awareness associated with corneal GP lenses.
Hybrid lenses now have designs that are specifically made for keratoconus patients. They have a central GP material that has a high Dk and a soft skirt that is created out of silicone hydrogel material.
Scleral lenses may be the answer
Scleral lenses and improved designs and materials have changed the way that keratoconus is managed. Scleral lenses, as their name implies, are fit so that the lens rests on the conjunctiva and underlying sclera. Although we categorize this as a contact lens, the scleral lens never actually touches the cornea when fit appropriately.
You may have heard success stories with patients fit in scleral lenses and seen discussion in literature regarding the finer points of fitting these contact lenses. If you are not currently fitting scleral contact lenses but are interested in working with them, we recommend three things to prepare yourself and your practice to fit scleral lenses.