Scleral contact lenses: How they can help you
If you've been told in the past that you cannot wear contact lenses because of an
irregular cornea or other problems, you may want to get a second opinion and ask your eye care professional about scleral contact lenses.
What are scleral lenses?
Scleral contacts are large-diameter gas permeable contact lenses specially designed to vault over the entire corneal surface and rest on the "white" of the eye (sclera). In doing so, scleral lenses functionally replace the irregular cornea with a perfectly smooth optical surface to correct vision problems caused by keratoconus and other corneal irregularities.
Also, the space between the cornea and the back surface of a scleral lens acts as a fluid reservoir to provide comfort for people with severe dry eyes who otherwise could not tolerate contact lens wear.
Types of scleral contact lenses
Scleral contacts are noticeably larger than standard gas permeable contact lenses. They have a diameter equal to or greater than that of soft contact lenses.
The smallest scleral contact lenses are approximately 14.5 mm in diameter, and the largest can be up to 24 mm.
Typically, lenses that are 18 mm or smaller are subcategorised as mini-sclerals.
The average human cornea is approximately 11.8 millimeters in diameter, so even the smallest scleral contacts are designed to cover the entire corneal surface.
In comparison, most conventional gas permeable contact lenses are 9.0 to 9.5 mm in diameter and cover only 75% to 80% of the cornea.
Another category of gas permeable lenses bridges the size gap between conventional GP lenses and mini-sclerals. These lenses, called corneo-scleral lenses, generally are approximately 13 to 15 mm in diameter.
Corneo-scleral lenses often are a good choice for people who require larger-than-normal GP lenses for greater comfort. They also are frequently used when contact lenses are needed after LASIK or other corneal refractive surgery to correct irregular astigmatism.
The size of scleral lenses that is best for you often is determined by the degree of complexity of your eye condition. Milder forms of keratoconus and irregular astigmatism from corneal grafts and refractive surgery often are easily managed with scleral lenses at the smaller end of the spectrum.
Smaller scleral and mini-scleral contacts can be easier to apply, may be less costly, and may require fewer care products.
More complex conditions, including advanced keratoconus, pathologically dry eyes or severe ocular surface disease that might require a large tear reservoir, often are fitted with larger scleral lenses, as they have more capacity to hold fluid or bridge large changes in corneal curvature.
During your contact lens exam and fitting, your eye care professional will determine the best scleral lens type and size for your specific needs.
Scleral contact lenses for keratoconus
Many eye care professionals recommend scleral contact lenses for a variety of hard-to-fit eyes, including eyes with keratoconus.
In cases of early keratoconus, standard gas permeable contact lenses may be used. However, if these lenses do not center properly on your eyes, move excessively with blinks, or cause discomfort, switching to larger scleral contact lenses may solve the problem.
Because scleral lenses are designed to vault the corneal surface and rest on the less sensitive surface of the sclera, these lenses often are more comfortable for a person with keratoconus.
Also, scleral lenses are designed to fit with little or no lens movement during blinks, making them more stable on the eye, compared with traditional corneal gas permeable lenses.
Scleral contact lenses for other eye problems
In addition to keratoconus, scleral contact lenses can be used for eyes that have undergone a cornea transplant, and for people with severe dry eyes caused by conditions such as Sjogren's syndrome, graft-versus-host disease (GVHD) and Stevens-Johnson syndrome.
Advances in lens design technology are allowing manufacturers to design scleral lenses that can correct more conditions than ever before, including bifocal scleral contacts for the correction of presbyopia.
Special-effect scleral contacts
Sometimes the terms scleral lenses or sclera lenses are used to describe special-effect contact lenses that dramatically alter the appearance of the wearer's eyes.
However, most special-effect contact lenses are soft lenses that bear little resemblance to scleral gas permeable contacts — other than their large diameter to fully mask the cornea. Also, soft special-effect contacts usually are designed for cosmetic purposes only and not for vision correction.
Scleral contact lens cost
Scleral contact lenses are custom-made for each wearer, so fitting scleral contacts demands greater expertise and more time than fitting standard soft or rigid gas permeable contact lenses.
Often, computerized maps of the curvature of the entire cornea are generated to facilitate the lens fitting, and several trial lenses of different sizes and curvatures may be applied to the eye during the fitting process.
Also, depending on the complexity of the problem and how the individual eye tolerates the scleral lens, adjustments of lens parameters may be needed, which will require additional lenses to be made and exchanged. The entire scleral lens fitting process can take several visits to determine the optimal lens for each eye.
While many individuals who use scleral lenses have worn soft or corneal GP lenses in the past, the process for applying and removing scleral lenses may take some practice. The additional time needed to master this, due to the larger size of the lenses and the fluid reservoir under the lenses, needs to be taken into consideration during the fitting process.
For these and other reasons, scleral contact lenses typically cost significantly more than standard contacts. Ask your eye care professional for details.
Page published on Monday, 14 March 2022