Express the dioptric base curve in diopters when the radius (in millimeters) is given.

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Multiple Choice

Express the dioptric base curve in diopters when the radius (in millimeters) is given.

Explanation:
The dioptric power of a curved surface relates inversely to its radius of curvature, and in keratometry the conversion uses a constant of 337.5. When the radius is measured in millimeters, the base-curve diopters are found with D = 337.5 / r, where r is the radius in millimeters. This means a smaller radius (tighter curve) yields a higher diopter value, and a larger radius yields a lower diopter value. The constant 337.5 comes from the refractive-index difference at the tear film/corneal surface and converting units from meters to millimeters. Therefore, the correct way to express the diopters from the given radius is D = 337.5 divided by the radius.

The dioptric power of a curved surface relates inversely to its radius of curvature, and in keratometry the conversion uses a constant of 337.5. When the radius is measured in millimeters, the base-curve diopters are found with D = 337.5 / r, where r is the radius in millimeters. This means a smaller radius (tighter curve) yields a higher diopter value, and a larger radius yields a lower diopter value. The constant 337.5 comes from the refractive-index difference at the tear film/corneal surface and converting units from meters to millimeters. Therefore, the correct way to express the diopters from the given radius is D = 337.5 divided by the radius.

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