Which technique is NOT used to minimize rotation of soft toric contact lenses?

Which technique is NOT used to minimize rotation of soft toric contact lenses?

• A. Prism ballasting
• B. Periballasting
• C. Slab off
• D. Truncation

Answer: (C)

Stabilizing rotation of soft toric contact lenses comes from shaping how the lens sits on the eye so gravity and lid interaction keep it oriented consistently. To minimize rotation, designers use ballast or geometric modifications that create a predictable preferred orientation. Prism ballasting adds a prism-like bias in the lens, usually by making the lower portion thicker or heavier, so the lens tends to settle in a stable, downward-facing position with the axis aligned. Periballasting similarly shifts mass around the periphery to resist rotation and maintain orientation. Truncation involves removing a small wedge or section of material to create a flat edge or altered thickness, which interacts with the eyelids to help lock the lens in place. Slab off, by contrast, is a spectacle-lens technique used to introduce a vertical prism effect in one eye to compensate for anisometropia or prism imbalance. It is not a method used to minimize rotation of soft toric contact lenses, which is why it isn’t part of the stabilization approaches for toric lenses.

Stabilizing rotation of soft toric contact lenses comes from shaping how the lens sits on the eye so gravity and lid interaction keep it oriented consistently. To minimize rotation, designers use ballast or geometric modifications that create a predictable preferred orientation.

Prism ballasting adds a prism-like bias in the lens, usually by making the lower portion thicker or heavier, so the lens tends to settle in a stable, downward-facing position with the axis aligned. Periballasting similarly shifts mass around the periphery to resist rotation and maintain orientation. Truncation involves removing a small wedge or section of material to create a flat edge or altered thickness, which interacts with the eyelids to help lock the lens in place.

Slab off, by contrast, is a spectacle-lens technique used to introduce a vertical prism effect in one eye to compensate for anisometropia or prism imbalance. It is not a method used to minimize rotation of soft toric contact lenses, which is why it isn’t part of the stabilization approaches for toric lenses.