To evaluate differences in the overnight corneal swelling response between hydrogel toric and equivalent powered spherical contact lenses, 16 subjects participated in an overnight in-clinic test session. After 8-9 hours of sleep the mean percent central corneal swelling was 10.984% for the eyes wearing the toric lenses and 10.074% for the eyes wearing the spherical lenses. There was a statistically significant difference in the mean percent corneal swelling induced by the two groups (P < 0.05 one-tailed repeated measures paired t-test). Qualitative evaluations showed 25% more striae and epithelial punctate staining in the toric group as well. These findings suggest that there is a corneal health basis for prescribing equivalent powered spherical hydrogel contact lenses rather than toric lenses to low cylinder astigmatic patients.
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