What are Scleral Lenses?
Scleral lenses are very large diameter gas-permeable lenses ranging from 14mm to 20mm that completely vault the cornea, “land” and rest on the white part of the eye called the sclera, and create a reservoir of tears.
Because of their size and this tear reservoir, they are typically extremely comfortable and at times may provide better vision correction than other standard contact lenses, glasses, and even surgery.
The lenses are made of materials that let oxygen pass through the lens and provide a thin cushion of fluid that stays between the lens and eye that makes them very comfortable, reduces redness and creates a healthy environment for the eye.
The lens is appropriate for most prescriptions and is available for patients who need help reading (multifocal / bifocal) and those with astigmatism (torics).
Who is a candidate for Scleral Lenses?
Scleral lenses may be the best strategy for providing patients with optimal visual correction, particularly in patients who have the following conditions such as:
• Pellucid marginal degeneration
• Post-penetrating keratoplasty (corneal transplant surgery)
• Post-radial keratectomy
• Post-LASIK ectasia
• Salzmann nodular degeneration and other corneal degenerations
• Servere dry eye, Sjogren’s KCS, Steven’s Johnson syndrome
• Congenital Nytagmus
• Normal corneas – athletes and active individuals, patients requiring bifocal correction too!
Scleral Lenses deliver:
» Consistent morning until night comfort
» Clear vision that does not fluctuate
» A healthy environment for your eyes
» Astigmatism correction
» Peripheral vision without halos or glare
» Lenses that provide excellent vision and that will not come out of the eye during sports activities
» Lenses that keep your eyes moist and comfortable regardless of your activities
The geometry of the Onefit P+A is specifically designed for corneas with a normal prolate profile, astigmatism, post grafts ( prolate profile ) or moderately irregular corneas such as emergent or fruste keratoconus cases. It also is available with multifocal optics, delivering superior visual performance for today’s active presbyopes.
Onefit is designed to vault a given topography with an optimal sag height, and is specified by the value of the base curve in mm; simplifying the fitting process and making it more user-friendly.
Onefit is supported by the conjunctiva and the fluid layer under the lens, rather than by the cornea. It is designed to vault the entire corneal surface including the limbal area. However, the clearance over the cornea varies from center to the periphery to optimize oxygen transmission to the tissue, especially over the limbus where the stem cells are located. Current published work indicates that fluid layer thickness is an important concern with scleral lenses. With an estimated DK value of 80, an excessively thick fluid layer under the lens can deprive the cornea and stem cells of sufficient oxygenation.
Onefit was designed to maximize oxygen transmission when combining the lens and tear layer thickness. For this reason the lens is thinner over the limbus compared to other designs. Its unique geometry reduces the tear layer from the center out to the limbal area. Optimum results in fit and corneal health are achieved with a clearance of 170 to 185 microns at the apex of the cornea, or in the area where the cornea is steepest ( e.g. host-graft corneal junction ) with limbal clearance not exceeding 40 microns. The lens peripheral edge should align with the conjunctiva. Onefit is manufactured in materials offering a minimum permeability of 100 DK.
Based on clinical trials, every 0.10 mm change in the base curve value results in an average variation in central clearance of 30 to 35 microns. For example, if the base curve is steepened by 0.10 mm the apical clearance will increase by 30 to 35 microns. On the other hand, if the base curve is flattened by 0.10 mm the apical clearance will be reduced by approximately 30 to 35 microns.
“As a long-time contact lens wearer, I have tried many different lenses. I am farsighted and have astigmatism and have worn soft toric lenses as well as gas permeable lenses.
I am an outdoor enthusiast and enjoy softball and golf, but I have always had trouble with debris getting behind my gas permeable lenses or fluctuating vision with soft toric lenses.
I am so happy with my Onefit™ P+A lenses and I can wear them all day with comfort. No longer do I have to worry about inconsistent vision or windy, dusty environments. I love these lenses!”
“LB, 47-year-old female, Richmond, VA”