Eccentric small-zone ray tracing wavefront aberrometry for refraction in keratoconus.

Area of Science:

• Ophthalmology
• Optometry
• Vision Science

Background:

• Keratoconus (KC) is a progressive corneal ectasia affecting visual acuity.
• Accurate objective refraction is crucial for managing KC and optimizing vision.
• Standard autorefraction may not fully capture the complex refractive errors in KC.

Purpose of the Study:

• To compare objective refraction using small-zone eccentric laser ray tracing (LRT) wavefront aberrometry versus standard autorefraction in KC.
• To assess if visual acuities achieved with these refractions differ between KC eyes and healthy eyes.

Main Methods:

• A prospective case-control study involving 29 KC eyes and 29 healthy controls.
• Refractions derived from LRT (central and eccentric zones) and standard autorefraction were used to determine uncorrected (UCVA) and spectacle-corrected (SCVA) visual acuities.
• Spherical equivalent (M) and astigmatic power vectors (C0, C45) were calculated; Pentacam HR® provided keratometry readings.

Main Results:

• Eccentric LRT measurements, particularly from the upper nasal zone, yielded better SCVA in KC eyes more frequently than standard autorefraction (p < 0.001).
• KC eyes exhibited worse UCVA and SCVA, with a pattern of inferior myopia and superior hyperopia compared to controls.
• While central LRT data yielded the best SCVA in controls, multiple eccentric LRT refractions showed similar SCVA in KC eyes.

Conclusions:

• Eccentric LRT measurements demonstrated superior performance in achieving better SCVA in KC eyes compared to standard autorefraction.
• Eccentric LRT offers a promising, valuable tool for subjective refraction in the challenging cases of keratoconus.