dry eye dx and tx
Consider Scleral Lenses for Ocular Surface Disease
BY KATHERINE M. MASTROTA, MS, OD, FAAO
In July 2009, at age 78, ophthalmologist Solomon Leibowitz retired from practice at Omni Eye Services. Dr. Leibowitz, an icon and Distinguished Alumnus of the famed New York Eye and Ear Infirmary in New York City, honored Omni Eye Surgery with his association for many years.
Among ophthalmologic books, instruments, and other memorabilia that Dr. Leibowitz so kindly made me caretaker of was a pair of PMMA scleral contact lenses fitted for one of his patients approximately 50 years ago. Pictured in Figure 1, nestled in their velvet-lined tin case, is a pair of one of the earliest functional contact lenses.
Figure 1. An early pair of PMMA scleral lenses.
Rocky Start, Promising Future
Scleral, or haptic, contact lenses rest solely on the sclera, completely vaulting the cornea and limbus. Primitive scleral lenses were made of glass, and later in a variety of materials, most notably polymethyl methacrylate (PMMA). PMMA was not a purpose-designed lens material and thus had the disadvantage of negligible oxygen transmission and a relatively hydrophobic surface. Corneal hypoxia induced by these PMMA scleral lenses caused microcystic corneal epithelial edema, otherwise know as Sattler's Veil or Fick's Phenomenon.
In spite of these issues, early sclerals did establish that a smooth layer of fluid retained over an irregular corneal surface can improve vision. We have since come to recognize that modern-design scleral contact lenses manufactured in highly oxygen permeable materials are viable choices in fitting irregular, diseased, or "dry-eye" corneas.
The aqueous layer beneath the scleral lens optic masks corneal irregularity, improving vision. By maintaining a pre-corneal tear reservoir, scleral lenses are becoming a recognized treatment modality for dry-eye affected corneal surfaces that are recalcitrant to currently accepted firstline therapies. Providing complete cover and a continuous layer of hydration to the compromised cornea, scleral lenses reduce discomfort and aid in corneal healing. The rigidity of the material offers mechanical protection from the environment and from lid abnormalities such as entropion or trichiasis.
Of note, scleral contact lenses have been successfully fit on patients who suffer from limbal stem cell deficiency, Sjögren's syndrome, Graft Versus Host Disease, neurotropic keratitis, Stevens Johnson syndrome, and keratoconus as well as on post-trauma, post-burn, and post-corneal transplant patients.
Well Worth the Effort
Most scleral lenses are 18mm to 23mm in diameter. Smaller semiscleral and intralimbal GPs starting at diameters of 13.5mm are available as well.
Sclerals must vault the central cornea, achieve complete limbal clearance, and align with the lenssupporting scleral conjunctiva. After topographic evaluation and initial diagnostic lens selection, fluorescein patterns can guide you to necessary lens adjustments.
Your most challenging dry eye patients may benefit from the use of scleral lenses; restoring their vision and comfort will make them your most grateful patients. Embrace the challenge. CLS
Dr. Mastrota is secretary of the newly formed Ocular Surface Society of Optometry (OSSO). She is center director at the New York Office of Omni Eye Services and is a consultant to Allergan, AMO, B&L, Inspire, and Cynacon OcuSoft.