The Family of Scleral Lenses
So, what is a scleral lens? To answer that question there needs to be a brief study of ocular anatomy. The cornea is the clear dome that initiates the focusing of light in the eye. Outside the cornea lies the ‘White of the Eye”, also known as the sclera. The junction between these two structures is the limbus. The cornea is more sensitive than the sclera. For example, if you use your finger and touch your cornea, you flinch from a piercing pain, however, if you touch your scleral area there is only a dull awareness. Therefore, contact lenses which rest on the sclera are MUCH MORE comfortable, by and large, than those which only rest on the cornea.
The second point to recognize is that there are essentially two different types of materials which make today's contact lenses: Soft lenses and Rigid Gas Permeable (RGP) lenses. The predecessors of the RGP lens were the Hard Lens. Whereas the hard lens was made of a material which did not allow the passage of gases, all RGP lenses (as their name implies) do. Today, the RGP materials are fantastically better in allowing the passage of gases (oxygen and CO2) which allows a much healthier lens-to-eye relationship.
So, what is a scleral lens? Today, a scleral lens is any RGP lens which is larger in diameter than the cornea. Even though all soft lenses have this larger diameter, they are not referred to as scleral lenses. See the photo which shows varying diameters of contact lenses.
There is some argument in the community of thinkers who like to name contact lenses. Dr. Wilcox likes to break down the naming of these large RGP lenses based upon how they fit the eye. The growing diameters of the “Family of Scleral Lenses” change from Corneal-Scleral to Semi-Scleral to Scleral lenses. A nice summary written by Dr. Wilcox, published in 2012 Scleral Lens Classification: A Different Approach.
Though the Wilcox Eye Center fits a significant number of soft lenses, the HUGE differences between Soft and RGP lenses are: (1) the significantly improved optics provided by the RGP lenses (2) the surprisingly fantastic comfort of all scleral lenses and (3) fact that scleral RGP lenses vault the cornea which is very healthy for the healthy eye but more importantly the patient with irregularly shaped corneas from ocular disease or previous surgeries. Look at the images of how the patient with Keratoconus who was previously fit (before presenting to the Wilcox Eye Center) in a corneal lens which rubbed a scar into his cornea. Dr. Wilcox instead fit him in a vaulting Semi-Scleral lens which gives him much better vision, comfort and health. He can avoid a corneal transplant which poorly fit lenses may precipitate.
Are you a candidate for one of our scleral lenses? If you are asking that question, then probably yes. Typically the healthy eyes are fit in the smaller Corneal-Scleral lenses. Those with high astigmatism, those that need multifocal and, those that have difficulty or poor vision wearing soft lenses also benefit. The other groups of people classically associated with the various scleral lenses are those with corneal diseases and post-corneal surgical complicated vision.
Here are some links which will give you a bounty of information. Remember, most of the information in these links apply to the largest lenses for the sickest eyes. Many, many normal with complicated prescriptions, dry eyes, previously poor multifocal optics… are successful with “smaller scleral lenses”.
- Scleral Lens Education Society
- Eef Van der Worp's “A Guide to Fitting Scleral Lenses”
- ICD 16.5 - Irregular Corneal Design
Please read or watch the testimonials of some of our patients who benefit from the various contact lenses designs.
We look forward to exceeding your expectations!