How does corneal topography influence toric lens selection?

• A. It helps determine lens color.
• B. It helps predict fit, centration, and rotation stability for toric designs.
• C. It measures tear film osmolarity.
• D. It is not used for toric design.

Answer: (B)

Corneal topography maps how the cornea curves in different meridians, showing both the amount of astigmatism and its axis. Toric lenses have different powers in two meridians, so knowing where the cornea is steep or flat helps predict how the lens will sit on the eye. This information guides selecting a toric design with the right base curve and diameter to achieve a stable, centered fit and minimize rotation. If the lens rotates, the cylindrical correction won’t align with the corneal astigmatism, so predicting potential rotation helps choose the axis and design that maintain stability and reduce residual astigmatism.

Color of the lens is unrelated to how toric optics are fitted. Tear film osmolarity is a tear physiology measure, not a factor in toric lens geometry or orientation. And saying it's not used for toric design ignores the essential role topography plays in aligning toric corrections with the corneal meridians.