Keratoconus is a disease of the cornea, the eye’s clear front part. The cornea becomes progressively thinner and less able to keep its shape against the intraocular pressure (IOP – the eye’s internal pressure). The eyes are filled with fluid that exerts outward pressure against the eyeball wall and the cornea is part of that wall.
The cornea gradually bulges forward as it thins, changing from its proper round shape to a cone-like shape – hence the name Keratoconus, from Greek words meaning cone-shaped cornea. The bulging cornea distorts vision, making it blurry, creating multiple images, and increasing the eye’s light sensitivity. Over time, the person becomes more nearsighted and astigmatic because of the steeper corneal curvature and its irregularity.
The cause(s) of Keratoconus are not known although some related factors have been observed:
- It seems to run in families, suggesting a genetic cause
- For unknown reasons, it occurs more often in people with Down syndrome
- It has been associated with allergic conditions such as eczema and dermatitis and asthma
- It can occur after over-exposure to the sun’s UV rays
- In some cases it appears to arise from chronic eye irritation such as that caused by ill-fitting contact lenses
- It is associated with excessive eye rubbing
- It may be associated with certain forms of eye surgery
Keratoconus can develop in one eye or in both and often begins during adolescence or young adulthood. It usually proceeds slowly and is not quickly detected, although in some cases it happens quickly.
Because Keratoconus is progressive, with vision changing over time and becoming worse, there is usually a series of treatments. Glasses may first be used but they become inadequate fairly soon.
- Contact Lenses – At first, soft contact lenses can help, but at some point the bulging makes them inadequate and the patient uses rigid gas-permeable (RGP) contacts. Their rigidity helps correct the conical shape, smoothing it down. However, they can be uncomfortable to wear.Another option is to “piggyback” two types of contact lens on top of each other. Soft lenses are placed on the cornea and RGP lenses on top of the soft lenses. This increases comfort because the soft lenses cushion the RGP lenses. Modern contacts are permeable enough that oxygen can still reach the cornea through two lenses. That is important because the cornea has no blood supply to bring it oxygen.
- Scleral Lenses – These contact lenses are larger in diameter than standard contacts and their edges rest outside the cornea, on the sclera (white part). This takes the pressure off the cornea for greater comfort. There are also semi-scleral lenses with a smaller diameter.
- Intacs – In 2004, the FDA approved Intacs for treating keratoconus. These are not contact lenses, but are curved segments of plastic that are inserted beneath the corneal surface, around its periphery. By gently pushing against the corneal edge, they flatten the top corneal curvature providing clearer vision.
When all types of contact lenses become inadequate, Intacs can be used instead, and when vision continues to deteriorate, they can be replaced with other Intacs customized for your new prescription. You can read more on our page about Intacs vs. Laser Vision Correction.
- Surgery – When both contact lenses of any kind and Intacs cease to be helpful, Dr. Kelly can do a corneal transplant. The entire cornea may be replaced, or it may be just a partial-thickness replacement. This improves vision but most people still need some kind of eyewear for fully clear vision.
To learn more about Keratoconus, please contact our eye care office for a complimentary consultation with Dr. Kelly. We serve Manhattan and Long Island in New York and we hope to meet with you soon.