Final answer:
A rigid lens showing no apical clearance indicates a flat fit, where the contact lens is too flat for the cornea's curvature. This can lead to discomfort and potential damage to the eye. Adjusting the fit is essential for the wearer's comfort and eye health.
The correct answer is options C
Step-by-step explanation:
A rigid lens showing no apical clearance is an indication of a flat fit. When fitting contact lenses, the term 'apical clearance' refers to the space between the apex of the cornea and the contact lens. If there's no apical clearance, this means the lens is sitting too close to the cornea, suggesting that the fit of the lens is too flat for the curvature of the eye's surface. A proper contact lens fit is crucial to ensure comfort, adequate oxygen transmission to the cornea, and to prevent potential damage to the eye.
In contrast, astigmatism is an irregularity in the curvature of the cornea that causes vision to be blurry or distorted at all distances. Contact lenses designed to correct astigmatism, typically called toric lenses, incorporate a cylindrical correction to compensate for this uneven curvature. A steep fit would signify a lens that has too much curvature compared to the cornea, while an alignment fit aims for uniform contact with the cornea's surface.