Welcome to the first edition of Toric Tips! Although toric lenses are not new, this newsletter will cover some fitting pearls for this contact lens modality. It continues to surprise, and even shock me at times when this situation occurs in my practice. It is likely familiar to you, too. A new patient with astigmatism wearing spherical contact lenses presents for an examination. When asked, adequate vision and comfort is reported with their habitual contact lenses. With refraction, at least 0.75 to 1.00D of astigmatism is present in each eye. When fit with toric contact lenses, significantly improved vision is reported. When the patient is asked if toric contact lenses have been tried previously, the answer is typically "no."
Why was the toric contact lens option not presented? Was astigmatism not found on refraction? Was the "adequate" vision acceptable to the patient and/or practitioner? What are best practices for patients with astigmatism? What does the literature say?
Forty-five percent of prospective contact lens patients have ≥ 0.75 diopters of cylinder. Fifty percent of patients with > 0.75 diopters of cylinder have between 0.75 and 1.00 diopters of cylinder.1 Interestingly, those who drop out of contact lenses, 65% have 0.75 cylinder or more in at least one eye.
A study compared the visual outcome of spherical and toric lenses in patients with low astigmatism.2 All 41 patients had myopia between 0.50D to 6.00D and astigmatism not more than -1.25D in at least one eye. Twenty-seven patients were bilateral fits and 14 were unilateral fit in one eye only (seven right and seven left eyes). The study determined that monocular and binocular high and low contrast logMAR visual acuities were significantly better with toric lenses compared with spherical lenses (p < 0.01). There was a significant improvement in both subjective and objective vision in myopic patients with low astigmatism corrected with toric lenses compared with spherical lenses.
A different study evaluated vision with spherical and toric soft contact lenses in myopic and astigmatic eyes.3 Fifteen patients (30 eyes) with myopia between -0.50D and -6.00D and cylinder between -0.75D and -2.00D were fit with four brands of spherical and toric lenses. Visual acuity was improved in both groups with toric contact lenses. In eyes with low astigmatism, visual acuity improved from 3 to 5.5 letters with toric compared to spherical contact lenses. In eyes with moderate astigmatism, visual acuity improved from 8 to 12.5 letters with toric compared to spherical contact lenses. Additionally, lens brand had a measurable effect on acuity for toric contact lenses.
These studies demonstrate the importance of using contact lenses including toric lenses for patients with astigmatism. Evaluate for the presence of astigmatism and offer contact lens options for your patients. Soft toric, hybrid and scleral lenses are all available options to correct astigmatism. In order to prevent contact lens drop out, correct the cylinder.
1. Holden BA. The principles and practice of correcting astigmatism with soft contact lenses. Aust J Optom 1975;58: 279–99.
2. Cho P, Cheung SW, Charm J. Visual outcome of Soflens Daily Disposable and Soflens Daily Disposable for Astigmatism in subjects with low astigmatism. Clin Exp Optom. 2012 Jan;95(1):43-7. Epub 2011 Nov 25.
3. Richdale K, Berntsen DA, Mack CJ, et al. Visual acuity with spherical and toric soft contact lenses in low- to moderate-astigmatic eyes. Optom Vis Sci. 2007 Oct;84(10):969-75.
Dr. Melissa Barnett is a Principal Optometrist at the UC Davis Eye Center in Sacramento, specializing in anterior segment disease and specialty contact lenses. Dr. Barnett is the Past President of The Scleral Lens Education Society. She lectures and publishes extensively on topics including dry eye, anterior segment disease, contact lenses and creating a healthy balance between work and home life for women in optometry.