You may have heard of a specific type of specialty contact lens called a scleral lens. Scleral lenses are needed in cases where the patient has extreme discomfort and/or dryness with soft contact lenses and cannot tolerate them, or soft lenses can no longer correct the vision adequately due to irregularities of the cornea. These are not the only reasons, but the most common. Because these lenses have a rigidity component to them, they can help change the way light hits the surface of the eye and correct the vision in a better way than soft lenses can. Because soft lenses only “drape” over the surface of the eye like a blanket, they cannot correct for irregularity of the surface. Irregularities of the corneal surface can happen due to many reasons such as keratoconus, pellucid marginal degeneration, scarring from a previous infection (ulcers, wounds, herpes simplex and/or zoster), history of either partial or full thickness transplant, and many more. Soft lenses can also act like little sponges on the surface of the eye and absorb tears, making dry eye worse and the lenses intolerable.
Scleral contacts are rigid and gas permeable, meaning they allow oxygen through the lens to nourish the cornea. The main difference from their smaller cousins, RGP lenses, is that the scleral lenses are much larger, and do not touch the cornea (clear covering over the colored part of the eye) at all. Scleral lenses rest on the white part of the eye, or the sclera. The lens is filled with sterile saline and inserted into the eye with the saline still in the bowl, so that the saline is in constant contact with the surface of the eye, allowing for continuous hydration and adequate correction of corneal irregularities. These lenses have been around for decades, but it’s only been recently that several advancements have been made.
When ordering a scleral lens for a patient, we as the doctor have the option of adding “aberration control” to the design of the lens. Aberrations are imperfections caused by the optics of the lens and the eye itself that cause the vision to be slightly limited. For example, a person wearing scleral lenses may be reading the 20/20 line perfectly, but can’t pinpoint something in their vision that is making it seem “off.” This may be a slight distortion, shadow, or differences in focus when looking at certain colors. We can control for some of these aberrations by adding in aberration control to the design of the lens. There are other aberrations, called higher-order aberrations, that we have not been able to control for in the past. However, with new equipment available to detect these types of aberrations, companies are now coming out with new designs of scleral lenses that can control the higher order aberrations, allowing for even better-quality vision.
Scleral lenses previously were single vision only, meaning they only focused at 1 distance. Most people prefer that to be their distance vision and opting to wear readers over top of the lenses to see up close. In recent years, many companies have come out with a multifocal design, allowing the wearer to see at distance, intermediate, and near without having to put readers on. The important aspect to remember with using a multifocal design is that it can cause a minor decrease in the distance vision clarity.
People who wear scleral lenses but also have double vision usually must wear prescription prism glasses over top of the lenses to correct for the double vision. In some designs of new scleral lenses, we can now add the prism correction directly to the scleral lens, eliminating the need for additional prism glasses. This is only available in few brands of scleral lenses and must be small amounts of prism.
Some patients with glaucoma have had treatments such as surgical procedures and/or implants that make fitting scleral lenses difficult due to the changes these treatments make to the curvature of the front of the eye. For example, some glaucoma patients have a tube or valve implant that reroutes the fluid on the inside of the eye, thereby lowering the pressure. Before, we could not fit a scleral lens on this type of eye, because it would smash the implant down and cause other issues. Now there are designs of scleral lenses that allow for small notches and elevations on the edge of the lens that can fit over the tube, not disturbing it at all.
New technology and designs of lenses are being researched and tested every day, all meant to make scleral lenses more comfortable and accessible to any eyeball and allow for the best possible vision. If you’re interested in scleral lenses or have questions, don’t hesitate to reach out to Sure Vision to make an appointment.
