What is a scleral lens and how does it function?
A scleral lens is a hat-shaped lens with a 22 mm diameter. Unlike smaller contact lenses the scleral lens does notrest upon the sensitive cornea but on the white, insensitive tissue of the eye, known as the sclera. The space between the lens and the cornea is filled with artificial tears, see FIGURE 2. This liquid layer corrects the irregular surface of the cornea, therefore improving vision, and maintains a pre-corneal reservoir. It also provides continuous hydration, soothing the dry eye and thus reducing discomfort and pain. The rigidity of the material provides optical correction and mechanical protection. The lens is made of a material highly permeable to oxygen, allowing the cornea to breathe. Scleral lenses are also comfortable to wear.
(FIGURE 3) Modern gas-permeable scleral lenses have a unique and valuable function, with both visual and therapeutic applications
Scleral lenses are indicated for several ocular conditions and can often be fitted successfully when corneal and hydrogel contact lenses fail.
A scleral lens provides the following:
- optical correction of irregular corneas (e.g. with keratoconus and corneal scarring)
- relief from symptoms such as pain and photosensitivity (e.g. from dry eyes)
- mechanical protection (e.g. with scarred eyelids or entropion)
- facilitation of the healing process (e.g. with recurrent corneal erosions)
The scleral lenses developed and used in our practice have additional, unique advantages, in that they can also be fitted to toric eyes. This has extended their use considerably and has lead to significant increases in comfort, vision improvement and the length of time they may be worn (FIGURE 4).?