Scleral lenses are a good option for the vast majority of people with keratoconus. These lenses provide the clearest vision possible by replacing the poor optics of your distorted cornea with a perfectly smooth lens. Because of their large size and the way they fit, they are much more stable than hard rigid gas permeable (RGP) contacts. That’s why scleral lenses are the preferred choice for clear, consistent, non-fluctuating vision for people with keratoconus.
The cornea is the clear dome of tissue that sits in front of the colored parts of your eyes. The beauty of scleral lenses and the reason they work so well is because they are large enough to completely cover your corneas without actually touching them. In fact, they only touch the white part of your eyes.
Think about how sensitive your corneas are. Even the slightest touch makes your eyes water. Even worse, if you touch your corneas, you can damage them and develop permanent cloudy scars, which make clear vision impossible. That’s why doctors agree that it’s best to minimize rubbing between your cornea and contacts.
Fortunately, the white tissues of your eyes are actually very tough. Scleral lenses take advantage of this and rest completely on the white tissues of your eye. In fact, a properly fitted scleral lens should never touch your cornea at all!
This design makes scleral lenses extremely comfortable. Most patients are surprised at how comfortable they are when they first try them on. Most importantly, however, a properly fitted scleral lens eliminates the possibility of corneal scarring caused by the cornea and lens rubbing together.
Finally, scleral lenses are completely customizable. This allows us to design lenses that fit a wide variety of eyes. From the beginning stages of keratoconus all the way to the most advanced stages and even on to transplanted corneas—scleral lenses are a safe and healthy way to give you the best vision possible.
First Generation Lenses
In the early days of scleral lenses, we thought that most eyeballs were round. Looking back, we now realize that this assumption was completely wrong! The vast majority of eyeballs are not round. In fact, a recent study found that only 5% of eyeballs are round.
Due to limited technology, the first scleral lenses were only capable of being designed to fit on round eyeballs. Back then, we didn’t have the ability to completely customize our lenses, either. So, during the fitting process, we picked a small, medium, or large lens and tinkered with different curvature rates until we got the best fit we could. As you can imagine, getting a perfect fit was challenging.
Think about it. Imagine you had a lens that was shaped like half a basketball. Now try fitting that perfectly round lens on a football. The football just wobbles inside the round lens. It doesn’t fit the football at all. It just doesn’t work.
In the same way, using a perfectly round scleral lens on a football shaped eye doesn’t work. If you try this, you’ll find that some areas are too tight, causing pinching and painful pressure on your eyes. You’ll also find that other areas are too loose, making you to feel the edge of the lens every time you blink.
This is why first generation scleral lenses were often uncomfortable. Also, these poorly fitting lenses often caused problems such as mid-day fogging and painful red eyes.
Second Generation Lenses
After we realized that that most eyeballs are football shaped, we started designing lenses to fit on footballs. This worked better and patients were happier. However, we still had a problem: We could change the lens to fit footballs and they were longer, shorter, thinner, and wider—but we always had to assume the eye was shaped like a perfectly symmetric football.
Now we know that eyeballs are not shaped like perfect footballs. In fact, recent studies have revealed that only 30% eyeballs are shaped like footballs. 65% of eyes are not perfectly symmetrical and do not have uniform curves like a football. Unfortunately, the majority of doctors who fit scleral lenses are unable to take advantage of this research because they don’t have the technology to create a custom scleral lens that perfectly fits a patient’s unique eye.
This is why fitting a scleral lens isn’t easy for most doctors. Some doctors struggle with lens after lens, trying to find a good fit through trial and error. We’ve heard stories of patients seeing their doctor more than ten times to try on ten different lenses and still being unable to get a lens that works. It’s frustrating, time consuming, and costly for both patient and doctors alike.
Prosthetic Contact Lenses
BostonSight recognized this problem and developed a system in 1994 that captures a mold of your eye and creates a lens that fits the unique shape of your eye. They call it a Prosthetic Replacement of the Ocular Surface Ecosystem (PROSE) lens.
These lenses are only available in twelve universities in the United States. They cost an average of $15,000 for one set of lenses. The fitting process is rigorous, taking four to twelve day long visits to complete the treatment, with follow up visits as needed during the first six months of wear.
If you are near one of these eye clinics, are able to make an appointment, and don’t mind the time commitment and financial costs, then go for it.
But if not, then read on…