During a follow-up exam, a patient wearing soft lenses reports their vision is clear immediately after a blink and then blurs. What is the most likely cause?

The scenario described indicates that the patient's vision is clear directly after blinking but then becomes blurry. This symptom can often be attributed to issues with the fit of the contact lens. When a lens is fitting too steeply, it can cause excessive interaction with the cornea, which may disrupt the tear film after the initial blink.

Initially, when the patient blinks, tears are spread across the surface of the lens and the eye, providing clear vision. However, if the lens is too steep, it may prevent proper tear exchange or distribution, leading to deterioration in visual clarity shortly after the blink. Thus, the clarity observed right after blinking can diminish as the tear film stabilizes or becomes insufficient, causing blurred vision.

Different fitting issues such as a loose lens or insufficient tear film would lead to both blurriness immediately after a blink and during periods of non-blinking. Similarly, cleanliness issues of the lens surface may not specifically cause clear vision immediately following a blink. Therefore, the characteristic of clear vision post-blink followed by a blur strongly indicates a steep fitting lens as the most likely cause.