Scleral lenses have been an optical game-changer for many of our patients. Their combined comfort and crisp optics make them a great choice for patients who have irregular corneas and ocular surface disease. Here are a few scleral lens optical “pearls.”

Tip #1: Over-Refract the Best Base Curve

With corneal GP lenses, we often make changes to the base curve (BC) and power of a lens based on how the lens is fitting. During a diagnostic fit, we may stop applying lenses if we are certain what BC would be needed for the final prescription. We then use the over-refraction (OR) and the SAM-FAP (steeper add minus/flatter add plus) rule to determine the final lens power.

Scleral lenses are much thicker than corneal GPs are and also have much thicker tear films. Because of this, the “thick-lens” optics effects are greater, and the SAM-FAP rule may not be as accurate when making large changes. So, when practical, be sure to do an OR with as close to the final BC as possible for best power accuracy.

Tip #2: Rotation for Torics

If your patient has significant residual astigmatism (RA) with a diagnostic lens, toric optics can be added. However, the lens must position with rotational consistency for a good optical effect (Figure 1). When changes to the transition or landing zones are made, this can cause the ordered lens to rotate to a different position.

Because of this, I will often order the spherical equivalent for the first lens and wait to reorder with toric optics once I know how the ordered lens will align on the eye. I also like to confirm the amount of RA to make sure that it is consistent (see Tip #3).

As with soft torics, be sure to use the LARS rule (left add, right subtract) to adjust the contact lens axis. This ensures that patients are looking through the correct axis in the presence of the contact lens rotation.

Tip #3: Decentered Lenses/Breakthrough HOAs

Patients who have irregular corneas have decreased vision with glasses in large part due to higher-order aberrations (HOAs). Keratoconus, for example, tends to result in large amounts of coma. Scleral lenses are able to correct some, but not all, of the HOAs when using spherical optics. When doing a sphero-cylindrical over-refraction (SCOR), you are using regular optics to attempt to correct irregular optics. The result can be a SCOR that improves but doesn’t perfectly correct vision, and it can be inconsistent on repeated measurements. Inferior decentration of the lens can also result in coma and inconsistent OR.

If you have access to an aberrometer, taking measurements with lenses on can help differentiate RA that is “real” from “breakthrough” HOAs. Improving lens centration by optimizing the fit can help, and there are now lenses available with aberration control to help in these cases.

Conclusion

I hope that these tips help you better manage your scleral lens cases. As always, lab consultants are an excellent resource for optimizing these lens fits. CLS