If an optical cross has the following powers: 035= -1.25/125= -2.00, what is the prescription?

To arrive at the correct prescription from the given optical cross, it's important to first understand how to interpret the power readings indicated.

In the optical cross notation provided (035 = -1.25/125 = -2.00), we notice two powers of the eye:

1. At the axis of 035 degrees, the power is -1.25 diopters.

2. At the orthogonal (90 degrees offset) from 035, which is 125 degrees, the power reading is -2.00 diopters.

The next step involves determining the prescription format. A prescription typically includes a sphere power, a cylinder power, and an axis. In this case, the spherical component can be thought of as the average of the two power values, while the cylinder component represents the difference between the two powers.

To calculate the cylinder power, we find the difference between the two measurements:

• Cylinder = -1.25 - (-2.00) = -1.25 + 2.00 = +0.75

The cylindrical power is therefore +0.75 diopters.

For the prescription, the sphere component is taken as the more negative value (which in this case is -1.25) and the cylinder is noted