A teenage athlete recently presented to the clinic for a second opinion about astigmatism in his left eye. He’s a baseball player and has gradually noticed more difficulty seeing the threads on the baseball when batting. Uncorrected visual acuity was 20/15 in the right eye and 20/20 in the left eye. The patient had seen another eyecare practitioner who confirmed the presence of astigmatism but said that it was not significant enough to correct optically.
The patient’s manifest refraction was OD –0.50 –0.75 x 165 and OS plano –1.25 x 002. His astigmatism was significant and was likely contributing to his vision difficulties while playing baseball. I recommended a daily disposable toric soft contact lens.
A short time prior to this patient encounter, I had performed objective vision screenings with an autorefractor on more than 200 collegiate athletes. I was surprised by the number of athletes who measured low-to-moderate levels of astigmatism (i.e., –0.75D to –1.50D) with the autorefractor who did not wear spectacles or contact lenses. Further, the autorefractor indicated that a large number of the athletes currently wearing contact lenses had significant residual astigmatism.
Both of these experiences made me ponder why so many patients who have low-to-moderate levels of astigmatism are not being adequately corrected. Is it because fitting toric contact lenses requires more chair time compared to fitting spherical equivalent or aspheric lenses? Are toric contact lenses fit less frequently because of higher fitting fees and material costs? Is there a false assumption that spherical equivalent or aspheric lenses provide the same image quality that toric lenses do?
Modernize Your Approach
The concept of “masking” astigmatism with soft contact lenses dates back to more than 30 years ago. Snyder and Talley (1989) utilized three spherical soft lens brands to “mask” –0.50D to –1.00D of refractive astigmatism and concluded that spherical soft contact lenses were unable to predictably mask low amounts of astigmatism. In another study, Morgan et al (2005) compared the visual performance of an aspheric soft contact lens to a toric soft contact lens and found that high-contrast and low-contrast visual acuity were better with the toric soft lens by approximately a half-line or more.
Modern soft contact lenses for astigmatism are significantly improved in design, stability, material, and comfort compared to early toric soft contact lenses. As a result, modern toric lenses offer improved visual performance compared to masking with spherical or aspheric contact lenses. Richdale et al (2007) examined the visual performance of four brands of spherical and toric lenses in individuals who had refractive astigmatism and found that the subjects wearing toric contact lenses saw three to 12.5 letters of acuity improvement compared to the spherical contact lenses. Cox et al (2018) compared results of two patient-reported measures—National Eye Institute Refractive Error Quality of Life Instrument (NEI-RQL-42) and Convergence Insufficiency Symptom Survey (CISS)—to determine whether there was a significant difference when astigmatic subjects wore a toric soft contact lens and a spherical contact lens. Subjects wearing toric lenses scored better than did those wearing spherical lenses.
Today’s patients spend more time on computers and electronic devices. Logan et al (2020) measured near visual performance on digital devices in patients wearing spherical and toric soft lenses. They noted a greater benefit when reading small print up close with toric lenses
Although fitting spherical or aspheric lenses to mask low-to-moderate levels of astigmatism may be quicker and less costly for astigmatic patients, visual performance data indicates that patients perform better when wearing toric lenses compared to spherical or aspheric lenses. The next time a patient who has low-to-moderate astigmatism enters your clinic, consider fitting him or her with a toric contact lens for optimal visual performance. CLS
For references, please visit www.clspectrum.com/references and click on document #311.