Inefficacy of Aspheric Soft Contact Lenses for the Correction of Low Levels of Astigmatism

Abstract

The purpose of this article is to compare the visual performance of a toric soft (TS) contact lens (SofLens 66 Toric; Bausch & Lomb, Rochester, NY), an aspheric soft (AS) contact lens (Frequency Aspheric; CooperVision, Fairport, NY) and a spectacle correction (SC) in subjects with low levels of astigmatism. One eye of 30 subjects with refractive astigmatism of -0.75 DC or -1.00 DC was tested. After pupil dilation, each subject was fitted with all three forms of correction in random order. Subjects were masked from the contact lens type. High-contrast visual acuity (HCVA) and low-contrast visual acuity (LCVA) were recorded for each correction using 2-mm, 4-mm, and 6-mm artificial pupils. With a 2-mm pupil, HCVA was similar for the TS lens and the SC (p = 0.13); better HCVA was demonstrated with the TS lens than with the AS lens (p = 0.001). With 4-mm and 6-mm pupils, HCVA was poorer with the AS lens than with the SC (p < 0.002) and TS lenses (p < 0.0001). The difference in HCVA between the TS and AS lenses was two letters, three letters, and one line with pupil sizes of 2 mm, 4 mm, and 6 mm, respectively. LCVA was similar for the three refractive conditions with the 2-mm pupil size. With 4-mm and 6-mm pupils, LCVA was similar for the TS lens and SC, but better than the AS lens by approximately one line in each case (all p < 0.0001). For small pupil sizes, there is little difference in HCVA and LCVA between various refractive corrections. However, for larger pupils, HCVA and LCVA are superior with TS contact lenses and SC versus AS contact lenses by approximately a half-line or more, which is considered to be clinically significant. Superior vision can be achieved for low astigmatic contact lens wearers using TS rather than AS contact lenses.