GPLI Toric and Spherical Lens Calculator

This calculator combines a spherical GP lens design nomogram developed by Dr. Ed Bennett with a GP toric lens calculator developed by Dr. Tom Quinn. This combined calculator was made possible via the assistance of Dr. Todd Zarwell of

This is a dynamic empirical method of determining GP spherical lens power, base curve radius, overall diameter and peripheral curve values for patients manifesting ≤2D of corneal cylinder. For patients with >2D of corneal astigmatism, a GP toric lens will be recommended and the toric lens powers, base curve radii, and overall diameter will be provided via dynamic “on-eye” optical crosses.

Instructions: Simply input the patient’s keratometry (or simulated “K”) values, and tap “return.” The refraction and recommended lens design parameters will be provided. As with any empirical calculator, there is no guarantee of first fit success; however, the resulting design should be a very good starting point toward successful GP lens wear.