What is an important factor to assess when choosing contact lenses for a patient with high astigmatism?

When selecting contact lenses for a patient with high astigmatism, the centering ability of the lens is particularly crucial. This is due to the nature of astigmatism, which involves the cornea or lens having an irregular shape that causes blurred vision. High astigmatism typically requires toric lenses, which are designed with different curvatures in different meridians to correct for the refractive error.

For these lenses to provide optimal vision correction, they must remain properly centered on the eye. If a toric lens rotates or shifts during blinking or eye movements, the specific area designed to correct the astigmatism may no longer align with the visual axis, resulting in compromised vision. Therefore, the ability of the lens to maintain its position on the eye is a deciding factor in achieving the best visual outcome for the patient.

While lens material, thickness, and curvature are also important considerations in determining the overall comfort and effectiveness of contact lenses, they are secondary to ensuring the lens remains centered. A well-centered lens will always provide better visual performance compared to one that may be made from an excellent material or of an appropriate thickness but tends to shift or rotate in the eye.