To patients, scleral lenses certainly don’t look comfortable, but modern technologies such as wavefront-guided lenses and hydrophilic polyethylene glycol (PEG) polymer coatings are defying those perceptions. With the wavefront-guided lenses designed for individual patients and PEG polymer coatings improving the devices’ wettability, comfort is the name of the game. But researchers wondered if those very advancements were causing measurable changes in aberrations. Any effect that a lens coating could have on the patient’s actual vision could render either wavefront-guided or conventional lenses useless or, at the very least, send manufacturers back to the drawing board. Luckily, a Texas-based research team found that whether lenses are wavefront-guided or not, any changes in aberrations caused by polymer coatings are clinically and statistically insignificant.
The research involved two uncoated control lenses and 14 experimental lenses (two repeated builds of seven aberration designs: one spherical, two coma and four full wavefront-guided second- to fifth-order aberrations). The aberrations were then measured by two operators before and after the coating was applied.
The median change in aberrations due to coating was 0.012μm and the maximum change in visual image quality due to coating was 0.073µm. The researchers speculated this equated to an approximate one-letter change in acuity. Longitudinal variability of the control lenses was low, all less than 0.017μm. Although the differences between repeated builds of all lenses was less than 0.25D and not statistically significant, relatively, manufacture constituted the major variability and difference between repeated builds was at least four times greater than the effect of coating (median, 0.167μm; range, 0.088μm to 0.312μm).
|Hastings G, Zanayed J, Nguyen L, et al. Do polymer coatings change the aberrations of conventional and wavefront-guided scleral lenses? Optom Vis Sci 2020;97:28-35.|