A patient diagnosed with a -2.50 rigid diagnostic lens has an over-refraction of -0.75 -0.25 x 98. What lens power should be ordered?

To determine the appropriate lens power to order for this patient, it is important to analyze both the prescription for the rigid diagnostic lens and the over-refraction results.

The patient was initially fitted with a -2.50 rigid lens. The over-refraction indicates that when the patient was tested with that lens, they needed an additional correction of -0.75 for sphere power and -0.25 for cylinder power at an axis of 98 degrees.

When calculating the new lens prescription, you begin with the original lens power of -2.50. Adding the sphere component from the over-refraction directly to this value:

• Start with the original lens: -2.50

• Add the over-refraction sphere: -2.50 + (-0.75) = -3.25

At this point, we also consider the cylinder power from the over-refraction (-0.25), but since the lens powers are combined for the final prescription and don’t alter the spherical equivalent, we focus on the spherical result. Therefore, the new lens prescription for the patient would be -3.25 for the spherical component.

This calculation accurately reflects the total lens power that would be required for optimal vision correction based on the diagnostic fit and the