Specialty Contact Lenses

Introduction

New lens designs and new materials have made contact lenses the choice for vision correction for many people who were not good candidates in the past. Soft toric lenses, which correct astigmatism, are now almost commonplace, as are daily disposable, extended wear and planned replacement lenses. The great majority of contact lens patients use some type of frequent replacement or multi-packaged lenses, making deposits on lens surfaces and other problems associated with standard daily-wear soft lenses a much less common complication.

Eyecare practitioners can now offer their patients lenses, soft or rigid, that are much more oxygen-permeable, allowing the cornea under the lens to breathe almost as well as with no lens in place at all.

There are also recent technology innovations that allow contact lens correction for patients with irregular or scarred corneas, or those with keratoconus to experience better vision than ever before, along with better comfort.

In the late 1950s, contact lenses were a brand new idea; how they fit, moved and their lack of oxygen transmissibility were poorly understood. The only material available to make contact lenses was polymethylmethacrylate (PMMA), a type of plastic that allowed no oxygen at all to pass
through it.

Scleral Lenses

One of the first lens designs was called a scleral lens, so named because it was very large, the edges resting on the sclera, the white of the eye. Both the upper and lower lens margins were well under the eyelids and they were large enough to cover the visible eye and then some. Because no oxygen could get through them, they were often fitted in such a way that an air bubble was captured under the lens. Even so, these scleral lenses were extremely uncomfortable and wear time was greatly limited, usually only about two to three hours.

Now, scleral lenses have returned, this time with much better materials and lens designs that allow them to vault over a scarred cornea or one with an irregular shape. They provide

• Sharper vision
• Greater durability
• Easier handling
• Less risk of complications
• More stability on the eye
• Less risk of accidental loss or displacement
• Comfortable all-day wear

There are three size groups of scleral lenses, depending on what is needed for best functionality. All modern scleral lenses are made with advanced, highly breathable gas permeable materials so plenty of oxygen can reach the cornea, regardless of lens size.

• Corneo-scleral lenses and semi-scleral lenses. These are the smallest of the group, but are still much larger than standard rigid gas permeable (RGP) lenses. The edges of these lenses rest near the junction between the cornea and sclera.
• Mini-scleral lenses vault over the entire corneal surface and rest on the front part of the sclera.
• Full scleral lenses are the largest and provide the greatest amount of clearance between the back surface of the lens and the corneal surface.

Scleral lenses are particularly appropriate for patients with corneal scarring, such as from a continuing condition like keratoconus, or from accidental or surgical trauma. They are also used for patients with eyes that were once considered “hard to fit,” meaning that the shape of the eye made conventional RGPs either uncomfortable or too easily dislodged, or both. They are a good option for people who participate in sports, for example.

Another area where scleral lenses are coming into their own is in the patient population suffering from dry eyes. This is because the generous space between the lenses and the eye surface acts as a tear reservoir to keep the front of the eyes more comfortable and moist. Dry eye patients have never been particularly good contact lens candidates, until now; in fact, scleral lenses may become one of the best tools for treating this condition.

Scleral lenses are custom-made to the individual cornea by an eyecare practitioner to provide the best possible eye health, comfort and vision. Because the lenses are larger than conventional lenses, special fitting tools such as imaging devices are needed to measure the eye and in their manufacture. For these reasons, the cost of scleral lenses will be higher than those for conventional lenses, either hydrogel lenses (soft) or RGPs.

In some cases where there is a medical reason for the use of scleral lenses (as would be the case in keratoconus or accidental trauma scarring, for instance) part of the cost may be covered by either medical or vision insurance. Your eyecare practitioner can provide you with the specific costs for your highly individual eyes.

Ortho-K Lenses

Sometime in the mid-1960s, eyecare practitioners began to notice that young myopic (nearsighted) people who were wearing contact lenses (there were no soft contacts until the early 1970s) were no longer becoming more myopic each year. The lenses had somehow stopped the progression usually seen in this patient population.

Eyecare practitioners began to research this phenomenon and many long-term studies were done to determine if this process could be controlled with the use of specific fitting techniques. Of course, now, with new materials available, orthokeratology (Ortho-K) is one option for reducing or eliminating myopia without surgery.

Ortho-K is a reversible process that gently reshapes the cornea while you sleep; it is suitable for patients with mild to moderate myopia and mild astigmatism. An analogy of how it works is to consider ortho-K to be somewhat like wearing dental braces to straighten and realign the teeth to a specific position. The difference is that the cornea is a highly elastic tissue and it will always revert to its original shape and curvature. For this reason, once the desired reduction in myopia has been achieved, the lenses are worn during sleep so good vision without correction can be enjoyed during the day.

The main purpose of Ortho-K is to be free of both contact lenses and spectacles during the day. It is ideal for individuals involved in sports or for those who work in dry or dusty environments where other types of vision correction may not work well. Ortho-K is especially useful in young people who are becoming more myopic during adolescence, as it will tend to stabilize the refractive error, as long as the patient continues to use the lenses.

Some long-term contact lens patients develop sensitivity to their traditional lenses, even though newer lenses are made with better materials and better designs than in the past. Sometimes known as corneal exhaustion syndrome (CLE), patients who have worn contacts for several years, and notice that their wearing time or lens awareness has increased may have developed CLE. Happily, CLE is not seen as often in recent years, because of better designs and materials.
Normal, healthy corneas are steeper in the center and gradually flatten out as they near the sclera; reverse-geometry lenses are made in such a way that they are flatter in the center, and become steeper towards the lens periphery, which causes the cornea to change its shape from the edges instead of in the center. This new fitting philosophy and lens design leaves the central cornea for the most part “as is.”

While most of the vision changes will happen within the first few days, it may take a few months for maximal results and stability. At that time, the eyecare practitioner will determine the amount of retainer-lens wear will be needed to maintain the new corneal shape.

The entire process of Ortho-K is reversible, non-invasive and can be modified easily. It is especially effective for young patients, or for those who are just not comfortable with the risks associated with refractive surgery.

It is important to understand that Ortho-K is helpful for mild to moderate myopia and astigmatism, but not meant for those with large vision corrections for either myopia or astigmatism, or for those who are hyperopic (farsighted).

People who are not good candidates for Ortho-K include those with:

• Eye disease or abnormality that affects the cornea, conjunctiva or eyelids
• Suffer from dry eye*
• Have allergic reactions that may be worsened by contact lenses
• Have high amounts of myopia or astigmatism, or who are hyperopic (farsighted)
• Have a cornea that is abnormally shaped*

*Patients with these particular problems should ask their eyecare practitioners about the new scleral lenses. (see previous section)

The cost of Ortho-K is higher than the cost of standard contact lenses, both because of how the lenses are made and the duration of treatment; the number of lenses needed depends on the individual patient. In general, the overall cost of Ortho-K is usually about half that of laser refractive surgery.

Soft torics, ortho-K lenses, and all the rest of these specialty lenses provide the eyecare practitioner and patient with more choices and will make it possible for some people to wear contact lenses that formerly could not. Others will allow patients who could not previously wear contacts to use them now, with better optics and lens design characteristics. The reality is that we are all different people and we all desire different things from our vision correction modalities; now, with new lens designs and materials, contact lenses may be possible for some people who had very little luck with them earlier.

If you have been told at any time in the past that you could not wear contact lenses, please, ask us about lens options that may allow you to use and enjoy the freedom that contacts provide.