A patient fit with a 44.00D lens and a power of -2.00 is re-fit with a base curve of 44.50. What power will now be required?

In contact lens fitting, the relationship between the base curve of the lens, its power, and the fitting relationship on the eye is crucial for achieving optimal vision correction and comfort. When changing the base curve of a contact lens, you must adjust the power to maintain equivalent optical correction.

A base curve that is steeper (increased number, such as changing from a 44.00D to a 44.50D) increases the effective power of the lens. This change occurs because a steeper lens surface causes light rays to bend more sharply, resulting in a greater total power.

When the patient was originally fit with a lens that had a power of -2.00D, that lens had a suitable relationship with the 44.00D base curve for their vision correction. However, fitting them with a steeper base curve of 44.50D means that the power needs to be adjusted to properly focus the light entering the eye.

For every 0.50D increase in base curve, typically, the power of the lens must decrease by approximately 0.50D to provide the same visual correction. Thus, moving from a 44.00D base curve to a 44.50D requires a shift from -