What potential problem can occur if the optic zone diameter is larger than the pupil by 1 mm?

• A. Glare/haloes
• B. Increased comfort
• C. Reduced movement
• D. Improved depth perception

Answer: (C)

When thinking about GP lenses, how much the lens moves on the eye with each blink depends in part on how the central optic zone relates to the pupil. If the optic zone diameter is larger than the pupil by about 1 mm, the central, refractive area sits more firmly over the cornea and interacts more with the lid during blinking. That extra central contact and the associated tear film/pressure dynamics can create a bit more suction or friction, which tends to hold the lens in place.

So the most likely consequence is that the lens moves less with each blink. This reduced movement can affect tear exchange and how the lens settles over time. Glare or halos are more often linked to mismatches where the pupil expands beyond the optic zone or edge effects, not simply to a larger optic zone relative to a small pupil. Increased comfort and improved depth perception aren’t direct, predictable outcomes of this particular size relationship.