Abstract
Purpose :
Recent advances in scleral topography and impression measurements created the opportunity of designing a well-fitting scleral contact lens without the use of a trial lens set. First lens fits have been demonstrated even in complicated cases, where scleral shape irregularities prevent using a trial scleral lens and the contact lens manufacturer needs to rely on the scleral topography or impression measurement alone to generate a lens design. Unfortunately, there is no good technique to estimate the power of the lens, and the scleral lens fitting becomes a two-step process. First, a scleral lens is manufactured using the measurements of the cornea and the sclera. This lens is dispensed and used for an over-refraction measurement. Finally, the second lens is manufactured with the correct prescription. This two-lens process increases the cost of the fitting by adding unnecessary chair time and lens manufacturing steps. The ability to correctly estimate the needed refraction without the trial lens will potentially eliminate one visit and will cut the price of the contact lens manufacturing in half.
Methods :
We attempt to use patient's own cornea as a substitution for a trial lens for final lens power estimation. In many cases, the indication for the scleral lens wear is irregular cornea. In such cases, a special care should be taken to measure the optical properties of the eye. Before fitting a scleral lens the following measurements are performed: (1) total optical path difference (OPD) or wavefront; (2) internal optical path difference (OPD) or wavefront; (3) local SimK values at the steep and flat axis. Using these measurements a lens power is predicted and compared to the final power of the lens dispensed using a standard over-refraction method.
Results :
Preliminary results demonstrate that using the total and internal optical path difference (OPD) measurements in combination with local SimK measurements of the cornea, it is possible to accurately estimate the prescription of the first lens without a trail lens over-refraction.
Conclusions :
For scleral lenses designed using ocular topography or impression measurements this method may simplify the fitting process and cut the manufacturing costs in half.
This is a 2020 ARVO Annual Meeting abstract.