Feb 2, 2013: Kerotaconus
WHAT IS KERATOCONUS?
Keratoconus is a condition that affects the cornea, the front clear window of the eye which normally has a spherical or dome shape. In keratoconus, the cornea becomes progressively thinner causing it to bulge forward and take on a cone-like shape. The central part of the cornea, which is used to bend light, becomes irregular in shape and light is not properly focused on the back of the eye. This is termed irregular astigmatism. In advanced stages, patients may develop scarring of the cornea which limits their ability to see and requires surgical intervention. Not all patients, however, will reach this stage of the disease.
WHO DOES KERATOCONUS AFFECT?
The prevalence of keratoconus is approximately 1/750 to 1/2000 people depending on the study. It usually begins in people during adolescence to early 20’s and may continue to progress in severity as the patient ages into their 30’s or 40’s. The condition is often hereditary and passed down in families. Therefore, it is important for children or siblings of patients with keratoconus to be evaluated. The condition has also been linked to people with severe allergies, connective tissue disease, eye rubbing, Down Syndrome, or a history of poor fitting contact lenses.
A person with keratoconus may experience a gradual blurring of vision, distorted vision, glare, and/or an increase in nearsightedness over time. This condition typically progresses slowly over time and usually affects both eyes, though one eye is usually affected more than the other. In the progressive stage of keratoconus, a person may find that their glasses prescription is changing frequently or that their vision is not clearly corrected with glasses. When this is the case, contact lenses may be recommended for a better quality of vision.
HOW IS IT DIAGNOSED?
Your eye doctor will look for signs of keratoconus during your routine eye examination. This includes checking your glasses prescription and examining your eyes under the microscope. If keratoconus is suspected, a corneal topography may be recommended. Corneal topography is a non-invasive procedure that simply requires you to look in a machine while it maps the shape of your cornea in just seconds.
TREATMENT FOR KERATOCONUS
In those with a mild stage of keratoconus, glasses or soft contact lenses may adequately correct vision. When these options no longer provide good vision, a specialty contact lens may be recommended. These types of lenses include rigid gas permeable lenses, piggyback lens systems, hybrid lenses, or scleral lenses. These lenses mimic the smooth dome-shaped surface of a regular cornea and eliminate the effects of irregular astigmatism.
• Rigid Gas Permeable (RGP) Contacts: These are small hard contact lenses that sit on the cornea and work well in many patients with moderate keratoconus. They are very easy to insert and remove, though comfort may take some adjustment for a first-time wearer.
• “Piggyback” System: This involves wearing a soft contact lens with an RGP lens on top. This helps to improve comfort and prevent dislocation of the RGP in patients who wear these lenses.
• Hybrid Contact lenses: If you know someone who wears “Synergeyes” lenses, they are probably wearing this type of lens. These are a combination of hard and soft lenses. The center of these lenses are an RGP (hard) lens and the perimeter is made of a soft lens material. These lenses are designed to give the vision and oxygen permeability of a hard lens with the comfort of a soft lens.
• Scleral Lenses: This lens is made completely of a hard lens material, though it is closer to a soft contact lens in size. It provides the supreme optics of an RGP lens, and since the edges of the lens do not touch the very sensitive cornea it is surprisingly comfortable to wear.
• Corneal collagen cross-linking: This is a non-invasive procedure designed to prevent (or ideally stop) the progression of keratoconus. It works by strengthening the structure of the cornea using riboflavin drops and UV light. While still in an investigational stage, this procedure is available at certain research clinics and may be promising.
• Corneal Intacs: This procedure involves placing plastic ring implants in the periphery of the cornea which work to flatten the central cone-like shape and change the structure of the cornea.
• Corneal transplant: Also known as a penetrating keratoplasty (PK or PKP.) This procedure is only indicated when a patient can no longer wear specialty contact lenses, or when scarring of the cornea limits their vision.