Toriques

Toriques are toric lenses designed to correct astigmatism by introducing cylindrical power that varies across the meridians of the eye. The term is used for both contact lenses worn on the cornea and implanted lenses used in cataract or refractive surgery, each providing a cylindrical component in addition to spherical refractive power.

There are two main forms of toriques: toric contact lenses (soft or rigid gas-permeable) and toric intraocular lenses (IOLs) implanted during cataract or refractive procedures. In both cases, the cylinder corrects astigmatism, and correct results depend on precise alignment of the lens cylinder with the eye’s axis. toric IOLs must be oriented at the intended axis within the eye, while toric contact lenses rely on stable positioning on the cornea.

Design and labeling: Lens prescriptions specify sphere, cylinder, and axis. The axis denotes the meridian that receives no cylindrical correction. In contact lenses, stabilization features such as prism ballast, dynamic stabilization, or other geometry help maintain proper orientation on the cornea. Toric IOLs employ dedicated haptics and design features to resist rotation after implantation.

Fitting and outcome: Evaluation uses keratometry or corneal topography to quantify astigmatism and guide selection of cylinder power and axis. For toric IOLs, accurate preoperative measurements and careful intraoperative alignment minimize residual astigmatism; misalignment reduces corrective efficacy, typically by about 3.3% for each degree of rotation away from the intended axis.

Limitations and risks: Toric optics depend on stable orientation. Rotation of a toric IOL or misalignment of a toric contact lens can reduce effectiveness and cause glare or halos. Care considerations include infection risk and comfort with contact lenses, and potential surgical risks with IOL implantation.