To estimate the proportion of potential soft contact lens wearers requiring an astigmatic correction and to estimate the proportion of astigmats who can be accommodated with toric soft lenses of varying prescription range.
A database of 11,624 spectacle prescriptions was used to calculate the prevalence of astigmatism for various thresholds (0.50-2.00 DC) by eye and by patient. The coverage of various prescription ranges was estimated using a subset of the database comprising those patients with at least 0.75 D of astigmatism in at least one eye (n = 5,444).
The prevalence of patients showing astigmatism of 0.75 and 1.00 D or greater in at least one eye was 47.4% and 31.8% and, in both eyes, 24.1% and 15.0%, respectively. The proportion of eyes showing astigmatism greater than or equal to 0.75, 1.00, 1.50, and 2.00 D was 35.7%, 23.4%, 10.8%, 5.6%, respectively. The prevalence of astigmatism of 0.75 D or greater was almost double in myopes compared with hyperopes: 31.7% vs. 15.7%. The prevalence of with-the-rule (WTR) astigmatism was higher than against-the-rule (32.9% vs. 29.1%); the proportion was also higher for WTR in eyes with astigmatism ≥0.75 D (15.3% vs. 14.5%). We estimate that approximately one third of potential contact lens wearers require astigmatic correction. A stock range of toric soft lenses in sphere powers +6.00 to −9.00 D, three cylinder powers, and 18 axes requires nearly 3,000 prescriptions and provides coverage for 90% of astigmats.
These findings provide an estimate of the proportion of soft contact lens patients requiring an astigmatic correction and some useful insights into the proportion of astigmats covered by toric soft lens stocks of varying range.
From the Visioncare Research Ltd (G.Y., C.H.), Farnham, UK; Johnson & Johnson Vision Care (A.S.), Wokingham, UK.
The author has no funding or conflicts of interest to disclose.
Address correspondence and reprint requests to Graeme Young, Vision Care Research, Craven House, West Street, Farnham, Surrey GU9 7EN, UK.
Accepted October 31, 2010.