If you fit a spherical contact lens, what term describes the remaining astigmatism?

If you fit a spherical contact lens, what term describes the remaining astigmatism?

• A. No astigmatism
• B. Increased astigmatism
• C. Eliminated astigmatism
• D. Residual astigmatism

Answer: (D)

When you wear a spherical contact lens, it mainly neutralizes the spherical part of refraction, but it does not correct the cylinder that causes astigmatism. The remaining astigmatism after using a spherical lens is called residual astigmatism. This term describes the amount of astigmatism that still exists once the spherical correction is in place. It differs from having no astigmatism (which would mean the cylinder was fully corrected) and from any idea that the astigmatism was eliminated or increased by the lens. If astigmatism is significant, toric lenses or other options are needed to address that residual cylinder.

When you wear a spherical contact lens, it mainly neutralizes the spherical part of refraction, but it does not correct the cylinder that causes astigmatism. The remaining astigmatism after using a spherical lens is called residual astigmatism. This term describes the amount of astigmatism that still exists once the spherical correction is in place. It differs from having no astigmatism (which would mean the cylinder was fully corrected) and from any idea that the astigmatism was eliminated or increased by the lens. If astigmatism is significant, toric lenses or other options are needed to address that residual cylinder.