The Scleral Lenses Solution  -  Onefit
scleral lens

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.

Keeping the Harvitt-Bonanno and Holden-Mertz criteria in mind, 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.