Which symptom indicates a flat fit for RGP lenses?

The presence of excessive movement during blinking is a key indicator of a flat fit for rigid gas permeable (RGP) lenses. When the lenses are flatter than the corneal curvature, they tend to move excessively on the eye during blinking due to a lack of adequate centration and fitting with the ocular surface. This excessive movement can lead to discomfort and inadequate visual acuity because the lens may not maintain a stable position on the cornea.

In contrast, the other symptoms do not directly indicate a flat fit. Decreased sensitivity might be related to other issues or conditions affecting the cornea and is not specific to lens fit. Pooling of tears could indicate an overly steep fit or other ocular issues, while improved visual acuity is generally not linked to fitting issues but rather indicates that the lens is appropriately centering on the cornea. Thus, detecting excessive movement during blinks is critical for assessing the suitability of the lens fit.