Which curve would a fitter modify to allow more tear flow under the edge of a rigid lens?

The posterior peripheral curve is the correct choice when considering how to modify a rigid contact lens to enhance tear flow under the edge of the lens. This curve is located on the back surface of the lens and is crucial for facilitating proper alignment with the cornea while ensuring adequate movement of the lens. When a fitter modifies the posterior peripheral curve, they effectively change the relationship between the lens and the cornea, allowing for increased space that can accommodate a greater volume of tears. An optimal amount of tear flow is essential for maintaining lens comfort and health, especially in rigid gas permeable lenses.

Modifying this curve can also help in reducing lens bearing on the cornea and can assist with the overall fit, making it more successful in retaining tears between the lens and the eye. Other curves, such as the optical curve, anterior peripheral curve, and anterior central curve, might influence the lens's fit and performance; however, they do not directly enhance tear flow underneath the lens edge in the same way that a change to the posterior peripheral curve does.