A COLLEAGUE ASKED ME ABOUT a keratoconus patient who was fitted for scleral lenses and complained of poor visual acuity. My colleague fit the lenses and measured a toric over-refraction. Therefore, he ordered a scleral lens with a toric front surface. But, with the new delivery came a new visual failure. To his surprise, he found the same residual astigmatism he had measured before. How is this possible?

It is simply because this pseudoresidual astigmatism is actually coma—a higher-order aberration (HOA) generated by the scleral and its decentration. There was a time when we attributed a drop in vision after fitting sclerals to lens flexure, citing topography measurements taken with the lens in place as evidence. This was not the case, as a thick lens is hardly flexing at all.

In keratoconus, the cornea generates HOAs. But it is important to note that those generated by the front surface partially compensate for those of the posterior float (surface). When the scleral lens is worn, the aberrations of the front cornea are dramatically reduced, allowing the aberrations of the posterior cornea to become more pronounced. Often, a patient is not used to such visual stimulation. Add to this the natural inferior-temporal decentration of the scleral lens, which creates coma, and this accurately describes the visual experience of the aforementioned keratoconus patient fitted with scleral lenses.

It has been shown that wearing a scleral contact lens inverts the aberrations that the patient usually perceives (Neal et al, 2024). These “new” aberrations become visually disruptive. The patient complains of reduced vision and image quality. Ghosting superiorly and to the right suddenly becomes trailed pixels interior and to the left.

Manufacturers and researchers quickly found a solution to fix this anomaly. The aberrations on the front surface of the scleral lens are compensated for, thereby canceling out the undesirable optical effects. Some products have been launched on the market, although they are not yet widely available. These are depicted as the lenses of the future and will be fully customizable. While the clinical results of these new HOA-correcting lenses are impressive, the business model supporting them does not seem to stand up to close scrutiny. It may alter the future of this modality.

Up to this point, to prescribe HOA-correcting scleral lenses, practitioners had to plan for 2 or 3 additional appointments for fitting—a highly stable lens required 1 to 2 visits, and repeated aberration measurements required another 1 to 2 visits. This resulted in a chair cost higher than that required for regular scleral lenses. Furthermore, it is difficult to predict which patients will exhibit a “wow” response after all this effort and which ones will merely shrug their shoulders, leaving the practitioner who wanted to give them high-definition vision skeptical.

Now, imagine that in 18–24 months, all these finally satisfied patients will need to renew their lenses. Their aberrations may have changed as well. In this case, we would be back to square one and would need multiple additional exams to finalize the lens replacement. In a busy practice, the growing number of patients requiring multiple exams may clog up the schedule and reduce the potential to help new patients. This economic model does not work well.

Although these customized corrections make sense in principle, practitioners need to find a clinical/business model that makes the process more user-friendly and less time-consuming.