HIGH ASTIGMATISMToric Designs and Indications
Jessica Conroy OD, FAAO
Sphere Power Effect (SPE) Bitoric
- Rotates on the eye without induction of power and without affecting vision1
- Has two base curve radii and two different powers1
Cylinder Power Effect (CPE) Bitoric
- Can NOT rotate on the eye without induction of power; affects vision1
- Has two base curve radii and two different powers1
Back Toric
- Toric on back surface and spherical on front surface of lens
- Spherical power is made possible due to the induction of cylinder power when back toric lens is fit1
- Amount of cylinder included = 0.456 times the back surface toricity1
- Requires well-centered and stable lens1
- Minimizes flexure, flare, and lens rocking1
References
- Bennett ES, Henry VA, Kinoshita BT, Lampa M. Correction of Astigmatism. In Bennett ES, Henry VA. Clinical Manual of Contact Lenses, 5th ed., Wolters Kluwer, Philadelphia, PA, 2020:388–439.