A WTR corneal astigmatism allows for better lens centration. Which option reflects this?

• A. WTR corneal astigmatism
• B. ATR corneal astigmatism
• C. Irregular astigmatism
• D. No astigmatism

Answer: (A)

Corneal toricity orientation affects how uniformly a gas-permeable lens can sit and center on the eye. When the cornea has with-the-rule astigmatism, the vertical meridian is steeper and the horizontal meridian is flatter. This setup tends to let the GP lens seat more symmetrically over the central cornea, with the eyelids and tear film helping to stabilize the lens in a centered position. The result is better, more predictable centration of the optical zone.

In contrast, if the cornea is against-the-rule (horizontal steepness), the lens can become less symmetrically supported by the lid and tear layer, increasing the chance of decentration or instability. Irregular astigmatism disrupts a uniform tear lens and prevents consistent centering, and having no astigmatism removes the toric cue that can aid stabilization, making centration less assured than in a regular WTR pattern.

So, the better centration scenario corresponds to the cornea with the vertical steepness of WTR.