CLINICAL

  specialty contact lenses

Conquer Complex Corneas

Scleral lenses provide vision correction, comfort and therapy.

JENNIFER S. HARTHAN, O.D., F.A.A.O. GLENVIEW, ILL., LOUISE SCLAFANI-McCLIMAN, O.D., F.A.A.O. CHICAGO, ILL.

When a patient who has high astigmatism (more than 2.50D) and/or corneal irregularity presents desiring or requiring contact lens wear, many of us use all our strength not to grimace in response. After all, these patients are notoriously challenging to fit in traditional GP or custom soft lenses due to their displaced corneal apex or high levels of corneal toricity, both of which contribute to lens decentration. As the cornea becomes more irregular, the fitting process becomes more complex.

The good news: Scleral contact lenses have enabled these patients to achieve successful wear. As a happy, satisfied patient becomes a loyal patient who sings your praises to family and friends, you should become a scleral contact lens provider.

Here, we provide an overview of scleral lenses, the array of ocular conditions for which they are being prescribed and some fitting pearls.

Overview

Scleral lenses rest on the sclera and completely vault the cornea and the limbus. As a result, they create a smooth refractive surface, enhancing vision for patients who have high astigmatism and/or corneal irregularity.

In addition, scleral lenses, by virtue of their design, prevent pressure on the corneal apex, and thus, minimize the potential for corneal scarring.

Also, their large size provides increased comfort, as the lid margin interacts with the surface of the lens rather than the lens edge.

Further, with the development of hyper-permeable lens materials and advanced peripheral systems (e.g. toric peripheral curves and quadrant-specific designs), scleral lenses are now often indicated for regular cornea patients who have unsatisfactory vision with other lenses, those who are non-adapts to corneal GP lens wear and in the rehabilitation of ocular surface disease (OSD).

(Visit the Scleral Lens Education Society at www.sclerallens.org for additional information on scleral lenses.)

1: Note the corneal staining pre-scleral lens fit on this ocular surface disease patient. The patient developed OSD from chronic graft-versus-host disease.

2. The patient experienced adequate central vault with a scleral lens.

3. Note the improvement in corneal staining after three weeks of scleral lens wear.

Ocular conditions

Practitioners have begun prescribing scleral lenses to patients who have keratoconus, pellucid marginal degeneration, graft-versus-host disease, Stevens-Johnson syndrome, exposure keratopathy, neurotrophic keratopathy, chemical burns, ocular cicatricial pemphigoid, corneal irregularity status post-penetrating keratoplasty, non-healing epithelial defects, limbal stem cell deficiency or other ocular surface diseases. The reasons: The lenses provide elevated oxygen permeability and corneal vault to allow for increased tear exchange.

Advanced OSD and resultant corneal disruption can lead to corneal complications and irregularities. As a result, patients who have OSD and also require refractive correction may experience difficulties in achieving both an acceptable quality of vision and improvement in their ocular surface with traditional contact lens designs. Scleral lens designs give practitioners the ability to both protect the cornea and provide better vision in a single lens.

Although small diameter corneoscleral and corneal GP lenses can work well for many OSD patients, for others, the eye is somewhat limited in the lenses’ tear reservoir capacity. So, even with maximum topical and systemic therapy, these patients’ ocular conditions may still be difficult to manage.

The tear film reservoir accumulated under a large diameter (>18.2 mm) scleral lens provides optical assistance for clear vision and a way to reduce mechanical disruption to the ocular surface. And in patients who have epithelial defects and severe ocular surface disruption, the area under the lens remains bathed with fluid during lens wear. The lenses may be filled with preservative-free tears, autologous serum eye drops or sodium chloride inhalation solution, thus providing nutrition to the ocular surface and, in some instances, allowing for the lenses to be worn on an extended wear basis. An example: a non-healing epithelial defect. Wearing the lens on an extended-wear basis serves as a bandage lens and assists in corneal healing.

Fitting pearls

Before and after lens wear, obtain sodium fluorescein and lissamine green staining of the cornea and conjunctiva to determine corneal health.

When inserting a scleral lens, the appropriate corneal clearance is 150 microns to 400 microns, depending on lens design and ocular condition. (It may be appropriate to have 400 microns or more of clearance under the scleral lens in ocular surface disease patients; however, close observation, which is relative to each patient, is warranted to monitor for corneal hypoxia and endothelial compromise.) These lenses require fitting beyond the limbus, so you must consider the scleral architecture when deciding on a lens design. Most scleral lens designs have toric scleral zones and quadrant-specific peripheries to enhance alignment and comfort on eyes that have a highly irregular scleral shape.

Finally, review handling and management with the patient, and monitor closely for potential complications, such as hypoxia, neovascularization and infiltrative and infectious events.

A welcoming smile

Scleral lenses have become an option for individuals who not only need a refractive correction but also have irregular corneas and severe OSD. By becoming familiar with these designs, you’ll no longer have to fight the instinct to grimace when a high astigmatism and/or corneal irregularity patient presents wanting or needing contact lenses. In addition, you’ll facilitate healing in OSD patients and prevent or prolong the need for a corneal transplantation — a win for these patients and your practice. OM

Dr. Harthan is an associate professor at the Illinois College of Optometry and is chief of the Urgent Eyecare Service at the Illinois Eye Institute. She works part time in a private practice in Glenview, Ill., where she specializes in complex contact lens fits and ocular surface disease. Dr. Harthan is experienced with a wide variety of contact lens fittings, including specialty lenses. E-mail her at JHarthan@ico.edu.

Dr. Sclafani-McCliman is an associate professor of ophthalmology and director of optometric services at the University of Chicago. Her main interests include contact lenses, corneal disease and emergency eye care. E-mail her at lsclafan@surgery.bsd.uchicago.edu, or send comments to optometricmanagement@gmail.com.