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Correction of residual astigmatism can improve visual acuity in keratoconus

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PHILADELPHIA – Scleral lenses that correct for higher-order aberrations may provide the best possible vision for patients with keratoconus, Muriel M. Schornack, OD, FAAO, reported in a poster here at Optometry’s Meeting.

However, such lenses are not yet commercially available, she said.

While Schornack presented two case reports where front-surface toric scleral lenses improved acuity in two patients with keratoconus, “Further study may more precisely define the percentage of patients who could benefit from toric scleral lenses and the magnitude of improvement in visual acuity that could be expected,” she said in the poster.

Schornack, from the department of ophthalmology at Mayo Clinic, Rochester, Minn., said that, historically, gas-permeable (GP) lenses have been used to manage keratoconus because of their ability to neutralize optical aberrations resulting from corneal surface irregularities.

“However, large-magnitude higher-order aberrations have been reported in keratoconus,” she said in the poster. “This could explain reduced visual acuity in some GP wearers with primary corneal ectasia despite a lack of corneal scarring.”

Today, higher-order aberrations can be accurately measured, but incorporating the necessary correction into traditional spectacles or contact lenses has been a challenge due to the need for precise centration and rotational stability in regard to the visual axis, Schornack said.

“Translational and rotational stability of scleral lenses has led to considerable interest in using these devices as a platform for delivery of optical correction for higher-order aberrations in patients with keratoconus,” she said.

“Adjustment of front-surface eccentricity of a proprietary scleral lens may reduce higher-order aberrations and improve visual acuity,” Schornack said in the poster. “Simple spherocylindrical overrefraction can determine the necessary power, and this correction can be incorporated into commercially available scleral lenses.” – by Nancy Hemphill, ELS

Disclosure: Schornack has no relevant financial disclosures.