When fitting with a rigid gas permeable contact what is a good diameter to start with?

When fitting with a rigid gas permeable (RGP) contact lens, starting with a diameter of 9.5mm is often recommended. This size is considered a good middle ground that typically accommodates a wide variety of corneal sizes and shapes.

A diameter of 9.5mm provides sufficient coverage of the cornea while also allowing for proper edge fit and comfort. It strikes a balance between too large, which may lead to movement issues, and too small, which may not provide adequate coverage and could potentially cause lens instability or discomfort.

Fitting with a 9.5mm diameter lens allows for additional adjustments during the fitting process to tailor the lens to the individual patient’s anatomy. Adjustments can include changes in diameter or base curvatures depending on the specific needs of the wearer, such as the shape of their cornea or their prescription. Thus, starting at 9.5mm is practical for most fitting scenarios.