Contact Lens – New “Scleral Lens” for Keratoconus and other Difficult Fits
The newest technology in contacts is the “Scleral Lens.”
I have been really pleased with the results when using this new lens (called the ICD 16.5). I have been using it since May, 2014. It is easy to evaluate, consistent in lens performance and has become my “go to” lens for difficult fits. It expands my ability to fit many of the most visually challenged patients.
For most contact lens wearers, soft contact lenses are very successful. They provide great vision, they are very comfortable, and today’s materials provide a healthy alternative to glasses. For some patients, it is a little more difficult. Corneal scars, diseases, degenerations, dry eye and previous surgeries may make everything much more complicated.
The human cornea usually has a very predictable shape, and today’s contact lens manufacturers have designed their soft disposables to fit our corneas in a way that gives us good vision and comfort. If that normal curvature is altered, the vision may not be adequate, and the fit may not be optimum for all day wearing. There are several corneal disorders that alter this normal architecture:
Keratoconus is a corneal degeneration that will change the corneal shape, causing significant visual distortion. Researchers believe that it is caused by the collagen fibers of the cornea not linking properly with each other, allowing the cornea to bulge over time. Keratoconus typically induces high and irregular astigmatism. While mild amounts of astigmatism are common, the particular kind of astigmatism found in keratoconus is difficult to correct with glasses.
Corneal scars from injury or disease can also cause the irregularity on the eye’s surface, resulting in visual distortion that can’t fully be addressed with glasses and conventional contact lenses.
Previous surgery can also change the natural smooth contour of the cornea. This can be intentional, as seen with refractive surgery and corneal transplants. If the irregularity causes distortion of the vision, then special contact lenses maybe needed.
Whatever may be the cause of the misshapen cornea, soft contacts only drape over this shape, therefore not correcting it. Rigid Gas Permeable contacts have been very useful in masking the distortions by giving the light we see a new, smooth contour to bend upon. The space between the rigid lens and the cornea is filled in with tears, and the distortion disappears.
The main issue, however, with Rigid Gas Permeable Lenses has always been comfort. They sit directly on the very sensitive cornea. The scleral lenses are much larger in diameter. They vault the cornea completely, landing on the conjunctiva, which is much less sensitive. Good vision is achieved by masking the corneal warpage, and good comfort is achieved by avoiding the cornea altogether.
The fact that the scleral lens does not touch the cornea is very useful. In certain cases, such as corneal transplants, protecting the cornea is important in preventing complications. The space between the contact lens and the cornea is filled with non-preserved saline. This may be helpful in cases of severe dry eye, where not enough tears are produced to keep the corneal surface healthy. The saline bathes the cornea all day, providing a great environment for normal corneal function and good vision.
Posted on November 07, 2014 by Dr. Dennis Miller, OD