What should a fitter do to decrease overall lens diameter to make a contact lens looser?

Decreasing the overall lens diameter is the correct approach to make a contact lens looser. When the diameter of the lens is reduced, it can cause the lens to fit less snugly on the cornea, as a smaller diameter means less surface area is covering the eye. This can lead to an increase in the movement of the lens during blinking and a more comfortable fit for the wearer, especially if the original lens was too tight.

In the context of contact lens fitting, the overall diameter is a critical factor influencing how the lens interacts with the eye. A looser fit can be particularly beneficial for individuals who experience discomfort or irritation with a tighter lens, as this can allow for better tear exchange underneath the lens and improve overall comfort.

Adjustments in the base curve, thickness, or lens material would not directly result in a looser fit. While changing the base curve might alter the lens's relationship with the curvature of the eye, it primarily affects the fit in terms of how well the lens conforms to the cornea rather than its overall diameter.