What base curve should be chosen for this patient given the data?

• A. 44.50D, 7.50 mm
• B. 44.00D, 7.60 mm
• C. 43.25D, 7.90 mm
• D. 43.8125D, 7.70 mm

Answer: (D)

A gas-permeable base curve should closely match the corneal curvature so the lens sits with mild apical clearance and stable centration. The data show a keratometry value around 43.81 D, which converts to a corneal radius of about 7.70 mm (using the standard keratometric relation r ≈ 337.5 / D). Choosing a base curve near 7.70 mm gives a lens that aligns well with the cornea, providing gentle central clearance without excessive bearing, which is the aim for a stable, comfortable GP fit.

If you pick a flatter curve (larger radius) you’d see too much clearance and potential lens wobble; if you pick a steeper curve (smaller radius) you’d risk central bearing and tightness. Thus, the base curve that best matches the measured corneal curvature is the one at roughly 7.70 mm.