Scleral contact lenses allow cornea subspecialists to deal more effectively with many patients whose corneal disease has frustrated ophthalmologists' best efforts. These patients share a common longing for a remedy to the problems of tear film, ocular surface and optical dysfunctions that prevent the pain-free, aberration-free corneal performance that most people take for granted. The patients' problems are the result of various conditions:
Almost universally, these patients balk at the suggestion that a contact lens will solve their problems. "The patient with severe keratoconus imagines another unstable, uncomfortable lens fit," says Muriel M. Schornack, O.D., with the Department of Ophthalmology at Mayo Clinic in Rochester, Minn. "The patient with dry eye worries about a lens abrading the compromised epithelial layer and worsening the pain from the exquisitely sensitive plexus of corneal nerves. The patient with ocular exposure does not understand how this lens will protect the eye any better than previous methods of therapy. Then we show the patient a scleral lens that has a design radically different from a soft or rigid lens."
Scleral lenses are generally 18 mm or more in diameter. They are supported entirely by a wide flange or haptic that rests on the sclera while completely vaulting the cornea and limbus. A fluid reservoir is maintained between the posterior surface of the lens and the anterior corneal surface. In cross section, the design is similar to a dome on a church.
Scleral support is the key to improved comfort compared with corneal lenses because of the lower density of pain fibers in the sclera than in the cornea. The cornea of a patient with severe dry eye or exposure keratopathy is bathed with fluid continuously. The lack of contact between the posterior lens surface and the cornea keeps the patient with irregular astigmatism comfortable while the spherical anterior surface of the lens neutralizes visual aberration caused by corneal irregularity.
Patients quickly understand the logic and elegance of the design and recognize that this is not a typical contact lens.
Before 2006, Mayo Clinic ophthalmologists referred patients potentially needing a scleral lens to Boston for fitting with the Boston Ocular Surface Prosthesis device (Boston Foundation for Sight, Needham, Mass.), designed by Perry Rosenthal, M.D. This lens, custom fit to the scleral and corneal parameters of each eye, provided excellent results for most patients.
The relatively high cost and limited access to the devices initially, however, hindered widespread application. "We searched for a commercially available lens that could provide similar success for less expense," says Dr. Schornack.
At Mayo, Dr. Schornack began fitting scleral lenses using the Jupiter design scleral lens, available from Visionary Optics (New York) and Essilor Contact Lenses (Dallas).
Since 2006, Mayo has treated 275 eyes of 180 patients. Lens fitting is based on a series of pre-made diagnostic scleral lenses that differ in diameter and base curve. Lenses can be customized to provide excellent vision and comfort for each patient. These lenses cost up to 75 percent less than proprietary designs, and so offer the patient a more affordable alternative for treatment.