Gas Permeable Contact Lenses – Introduction Practice Test

Flexure involves the lens bending on the eye under lid forces, changing the lens’s effective curvature in contact with the cornea. To detect this bending, you want a metric that directly reflects how the on‑eye lens curvature compares to the cornea. The radiuscope with an over-K reading does exactly that: it measures the lens’s curvature relative to the corneal curvature, so changes in the lens shape from flexure produce noticeable shifts in the over‑K value. If the lens flexes, the on‑eye radius changes, and the over‑K reading will move accordingly, signaling flexure. In contrast, keratometer readings only capture the cornea’s curvature and don’t tell you about the lens’s shape on the eye; slit-lamp observations can show movement but aren’t a precise, quantifiable measure of flexure; and an ophthalmic refractometer assesses refraction with the lens not on the eye, so it won’t reveal lens bending.