Let’s consider the comfort of firm vs. soft contact lenses. A significant number find both firm and soft contact lenses uncomfortable, a few find firm contact lenses more comfortable, and a greater number find soft contact lenses more comfortable. Some of the comfort experienced by soft lens wearers is because soft lenses are larger.
Let’s consider clarity of vision. Just as soft lenses have the edge in comfort; firm lenses have it in sharpness of vision.
Wouldn’t it be nice if there was a firm lens with the consistent comfort of a soft and the usually sharper vision of more rigid lens? Interestingly enough, there is such a lens.
Today’s firm lenses are approximately 7 to 11mm and soft lenses 13 to 15mm. In 1888 and 1889 Fick, Mueller and Kalt used blown glass to make firm contact lenses approximately 20mm in diameter. These large lenses laid way out on the white part of the eye. When you can make the sclera bear the load – contact lens become quite comfortable.
The problem with glass is that it does not breathe. To allow oxygen to the underlying tissues, a contact lens must be permeable to gases – thus the name “rigid gas permeable” materials. Of course, much to my aggravation, everything today is reduced to initials. In this case “RGP.” These large RGP lenses are called “scleral contact lenses.”
RGP has more advantages than just gas permeability. These materials are easily molded and tooled. As a contact lens material, the optics of RGP is every bit as good as glass, and it’s safer.
Scleral lenses vault over and never touch that clear dome, the cornea, where all other contacts lenses lay. This provides a moisture chamber in which the cornea is bathed constantly. They also have a constant orientation on the clock dial, allowing special optical features.
These features also mean that scleral lenses can be used on damaged, sick or irregular corneas. We encounter patients with keratoconus who see only 20/60 with glasses, are intolerant of standard RGPs, and have only 20/40 in soft lenses. With scleral lenses we can frequently provide them with 20/20 vision – sometimes even better.
Let me close by reiterating that scleral lenses are very comfortable – possibly even more so than soft lenses. They are not limited to special cases. They’re an alternative for any contact lens wearer.
Check out Custom Stable Lens – call us to see if they’re a good fit for you.
Top photo, cropped to fit post: Wikipedia – L8rgator: Dry eye syndrome scleral lens with visible vault, side view. Bottom photo: L8rgator at English Wikipedia