Toric base curves observed on a GP lens are most indicative of which issue?

Toric base curves observed on a GP lens are most indicative of which issue?

• A. Warpage
• B. Flexure
• C. Decentration
• D. Tear exchange

Answer: (A)

Toric back curves on a gas-permeable lens indicate deformation of the lens itself, i.e., warpage. GP lenses are designed with a spherical back surface to match a spherical cornea. When the back surface becomes toric, it means the lens has warped from its original shape, often due to heat or chemical exposure during cleaning, improper storage, or repeated disinfection. This permanent change alters how the lens sits on the eye, typically affecting fit and alignment. Flexure is a bend that occurs while the lens is worn under eyelid pressure and is usually temporary; once the lens is off the eye, the back surface tends to return toward its original shape, so toricity won’t persist as evidence of flexure. Decentration refers to the lens not centersing over the pupil, which can result from fit issues but doesn’t by itself indicate a toric back surface. Tear exchange describes fluid movement under the lens and is unrelated to the curvature of the lens’ back surface.

Toric back curves on a gas-permeable lens indicate deformation of the lens itself, i.e., warpage. GP lenses are designed with a spherical back surface to match a spherical cornea. When the back surface becomes toric, it means the lens has warped from its original shape, often due to heat or chemical exposure during cleaning, improper storage, or repeated disinfection. This permanent change alters how the lens sits on the eye, typically affecting fit and alignment.

Flexure is a bend that occurs while the lens is worn under eyelid pressure and is usually temporary; once the lens is off the eye, the back surface tends to return toward its original shape, so toricity won’t persist as evidence of flexure. Decentration refers to the lens not centersing over the pupil, which can result from fit issues but doesn’t by itself indicate a toric back surface. Tear exchange describes fluid movement under the lens and is unrelated to the curvature of the lens’ back surface.