For an interpalpebral GP lens fit, should you use a smaller or larger OAD?

• A. Smaller OAD
• B. Larger OAD
• C. Same as corneal diameter
• D. Depends on keratometry

Answer: (A)

When the GP lens is fitted interpalpebrally, the lids are the main shaping force on the lens edge during blinking. A smaller overall diameter keeps the edge well within the palpebral aperture, reducing lid–edge contact and friction. This helps the lens stay centered under the lids, maintains a stable tear reservoir beneath the lens, and minimizes lid-driven decentration or rubbing. If the diameter is too large, the edge can encroach on lid tissue during blink, leading to edge lift, instability, and discomfort. Keratometry and corneal diameter influence optics and basic fit, but for interpalpebral wear the lid dynamics favor a smaller OAD.