There are a variety of reasons a patient may need a specialty lens. These include irregular corneas due to scarring or keratoconus, changes in corneal shape after LASIK, dry eyes, and even some high prescriptions.
Keratoconus is a dystrophy of the cornea. The cornea normally has a round dome shape. In keratoconus the cornea progressively thins, which allows it to bulge forward unevenly. This uneven bulging causes distorted vision. Keratoconus can be mild, moderate or severe. In mild keratoconus patients can usually still see well with glasses or conventional contact lenses. Sometimes patients with mild keratoconus see better with custom soft contact lenses. In moderate or severe cases-custom designed contact lenses utilizing rigid material usually provide better vision than glasses. These lenses may be corneal RGPs, hybrid or sclerals (see below for further information) The reason these contact lenses can provide better vision in these cases is that they provide a new spherical or dome shaped surface for the images to enter the eye. For more information about keratoconus please visit www.nkcf.org.
In the early stages of keratoconus, many patients will see adequately with glasses or soft contact lenses. As the keratoconus progresses and the cornea thins and becomes more irregular, the vision is often not adequate unless a custom contact lens is used. The contact lenses for keratoconus must be carefully fitted and monitored. Because the cornea continues to change shape, the lenses may need to be re-fitted in one to two years. It is important to have the fit of lenses for keratoconus evaluated every year for any needed changes.
Keratoconic corneas all have a unique shape. Because these shapes are irregular, keratoconus lenses must be custom designed and manufactured for each eye. Trying diagnostic lenses on the eye during the fitting process speeds things up considerably. We carry many fitting sets in stock and can borrow fitting sets from our laboratory when we need additional options. Lenses we consider for keratoconus include rigid lenses such as RoseK, scleral lenses such as Blanchard OneFit, Zenlens, Boston Sight, Jupiter, Acculens etc. , soft lenses such as Kerasoft or Arc and finally hybrid lenses (rigid lens with a soft skirt) such as Synergeyes Ultrahealth. We have been having great success with these newer lenses for keratoconus due to increased patient comfort versus conventional sized rigid lenses.
Some patient experience regression or even corneal irregularities after LASIK. Because LASIK removes some of the tissue from the cornea, these eyes can be a bit more complicated to fit. The normally round dome-shaped cornea is now flat across the top and may no longer do well with a round dome-shaped contact lens draped across the front of the eye. In these cases we use specialty contact lenses such as reverse-geometry RGPs, Kerasoft, ARC or scleral lenses.
Patients who have had radial keratotomy often experience fluctuation in vision throughout the day. In the worst cases, they experience blur that is not correctable with glasses or even conventional contact lenses. For these patients custom soft or scleral lenses can often provide stable, clear vision.
For high astigmatism we often utilize custom soft and hybrid lenses.
For mild to moderate dry eyes, some of the newer daily disposable soft contact lenses can be a viable option. For moderate to severe dry eye, scleral lenses can be life-changing. Scleral lenses keep a bath of fluid in front of the cornea while the lens is on the eye--often greatly improving comfort. We now have a new coating called Tangible Hydrapeg that can be applied to the front surface of the lenses which further enhances the wettability and comfort. Dry eye diagnosis such as Sjogren’s Syndrome often allow the lenses to be billed to insurance as medically necessary.
We have seen an increase in patients getting fit for orthokeratology corneal reshaping lenses. Recent studies show that orthokeratology lenses can slow down the progression of myopia in children. Patients love that the lenses are worn only at night, allowing for clear vision during the day without lenses.
These are large diameter rigid gas permeable lenses that rest on the white part of the eye, called the sclera, and vault over the cornea. The size can be an alarming prospect for some, but scleral lenses have many advantages. Because of their size, they do not fall out and dust or dirt particles cannot get under them during wear. They are surprisingly comfortable to wear, because the edges of the lens do not interact much with the eyelid.
Hybrid contact lenses are a rigid gas permeable contact lens with a soft skirt. The soft skirt can increase comfort and help with centration. These lenses can be a nice option for both regular and irregular corneas.
Kerasoft lenses are an exciting new addition for mild to moderate keratoconus as of 2012. These lenses are highly customizable soft contact lens for irregular corneas. They are made of an extremely oxygen permeable silicone hydrogel material. They are quarterly replacement.