Anyone who has received a recent diagnosis of keratoconus may feel overwhelmed when considering their treatment options for this corneal disorder. If you are living with this eye disorder and are having difficulty performing routine or preferred activities due to myopia, utilizing some type of contact lens may enable better vision. According to the Centers for Disease Control (CDC), at least 45 million people in the US wear contact lenses.
If you have an astigmatism that precludes the use of soft contact lenses – and have not been able to adjust to Rigid Gas Permeable (RGP) contact lenses (hard lenses) – scleral contact lenses may be a reasonable option for you. At the Precision Keratoconus Center, we can help you to understand whether scleral lenses makes sense for you as an individual with keratoconus.
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How Astigmatism Affects Contact Lens Options
Most people with keratoconus develop progressive myopia (nearsightedness). Soft contact lenses can help people with myopia to more clearly see objects at a distance. However, keratoconus causes most affected young people to have an astigmatism (as well as myopia). Distorted vision linked to an astigmatism in keratoconus is typically caused by an irregularity in the way light passes through the lens of the abnormally long cornea to the retina.
For correction of both myopia and astigmatism, the type of contact lens historically recommended by optometrists has been “hard” (rather than “soft”). For people with keratoconus, wearing “hard” contact lenses can be difficult for the following three reasons (per the American Optometric Association):
- “Hard” lenses can slip off the center of the eye more easily than other types of contact lenses.
- Debris can sometimes get under “hard” lenses (causing irritation or infection of the cornea).
- “Hard” lenses require consistent wear to maintain adaptation.
Additionally, “hard” lenses can increase eye pain in people with keratoconus due to their contact with the cornea.
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How Do Scleral Lenses Differ from Traditional “Soft” and “Hard” Contact Lenses?
Since Dr. Donald Ezekiel first described them at an academic conference in 1983, contact lenses that cover the whole sclera of the eye (inclusive of the cornea and lens) have become increasingly precise. Since these lenses do not “rest” on the cornea, they may be a better choice for someone who cannot tolerate the corneal friction that can occur with traditional contact lenses (whether “soft” or “hard”).
In comparison to RGP lenses, fitting a scleral contact lens to a person’s eye can require more extensive measurements. Not only may a slit-lamp exam be required, but also corneal mapping.
Large diameter contact lenses (e.g., scleral lenses) – with their resting points beyond the corneal border – are among the best vision correction options for irregular corneas (per a monograph of Pacific University’s College of Optometry published in 2015).
The spherical design of scleral lenses involves acquiring measurements of the eye in order to design each of the following three parts of a scleral contact lens:
- Optical zone (center-most zone of the scleral contact lens);
- Transition zone;
- Landing zone
Scleral Contact Lenses in Corneal Transplant Recipients
Corneal transplantation (penetrating keratoplasty) is unsuccessful in 13-31 percent of patients within three years of transplantation. According to the College of Optometrists, the following are three predisposing factors for corneal transplant rejection (besides nonadherence to prescribed daily eye drops):
- Co-disorder of glaucoma;
- Recent decrease in steroid therapy;
- History of Herpes simplex infection in the eye
If you have experienced rejection of a corneal transplant, scleral contact lenses may still be an option for you. Consulting with an optometrist associated with the Precision Keratoconus Center can help you to ascertain the range of treatment options available.