This article was originally published in a sponsored newsletter.

When fitting soft toric contact lenses, a common question is which type of soft contact lens that corrects for astigmatism will provide the best vision.

A study examined the optical quality of two different daily replacement silicone-hydrogel soft toric contact lenses compared to a spherical daily replacement contact lens control.¹ The lenses studied were a prism-ballast (PB-CL) design and a design that was stabilized by the eyelid. The prism-ballast design includes a toric technology that offers uniform horizontal ISO thickness and optimized ballast band design to enhance lens stability and decrease rotation for better visual acuity. The eyelid stabilized design is horizontally symmetrical, does not contain prism in the optic zone and uses four stabilization zones that have a thickness profile gradient that interact with both eyelids to rapidly stabilize and maintain the lens position. The control lens used was a spherical daily replacement silicone hydrogel contact lens.

Eligible participants included soft contact lens wearers from 20 to 39 years old (average age 27) who wore contact lenses more than eight hours per day at least five days per week, without ocular or systemic pathologies and who did not receive any drugs with known effects on visual acuity or accommodation. Twenty soft contact lens wearers (17 females and three males) participated in the study.

This study determined that corrected distance visual acuity and astigmatism obtained with toric contact lenses provided improved vision compared to spherical contact lenses. There was not any difference between toric contact lenses for rotation. Compared to prism-ballast contact lenses, the eyelid stabilized design demonstrated less coma aberration. ESD-CL showed subjective improvement for “blurred vision” and “double vision” compared to spherical lenses. There was no difference between eyelid stabilized design compared to the prism ballast design “blurred vision” and “double vision.”

A different study by Berntsen and colleagues did not find any difference in ocular higher-order aberrations between thin-zone and prism-ballast designs, with the exception of vertical coma.² Less vertical coma was found with the thin-zone lens than different prism-ballast toric lenses. In this study, both vertical and horizontal comas were measured. The majority of the coma was from vertical coma. Notably less coma was found in patients who had the eyelid stabilized design compared to the prism ballast design.

Consistent with previous studies in eyes that have low astigmatism, this study reported that corrected distance visual acuity was better with soft toric contact lenses compared to spherical contact lenses. This study illustrates that based on the design of soft toric contact lenses, there may be disparities in coma and subjective symptoms.

REFERENCES

1. Koh S, Maeda N, Terao M, et al. Optical Quality and Visual Performance With Different Toric Contact Lens Designs. Eye Contact Lens. 2023 Sep 15. [Online ahead of print]

2. Berntsen DA, Merchea MM, Richdale K, Mack CJ, Barr JT. Higher-order aberrations when wearing sphere and toric soft contact lenses. Optom Vis Sci. 2009 Feb;86:115-122.

Melissa Barnett, OD, FAAO, FSLS, is the director of optometry at the University of California, Davis in Davis, specializing in anterior segment disease and specialty contact lenses. She is the past president of the Scleral Lens Education Society. She is an advisor to and/or has received honoraria or travel expenses from AccuLens, Alcon, Allergan, Bausch + Lomb, Bruder, Contamac, CooperVision, Johnson & Johnson Vision, Ocusoft, ScienceBased Health, Shire, Tarsus, and Visus Therapeutics.