Certified Paraoptometric (CPO) Practice Exam 2025

What power might a spherical lens have?

1. -1.00 or +3.00

2. -2.00 or +1.00

3. 0.50 or +2.50

4. -3.00 or +0.50

The correct answer is: -2.00 or +1.00

The power of a spherical lens is measured in diopters and indicates how much it converges or diverges light. Spherical lenses typically can have a wide range of powers, both positive and negative. The correct answer encompasses a reasonable range of typical powers for prescription lenses. In this case, the values presented suggest both a higher negative power (-2.00) and a lower positive power (+1.00), which are common within the scope of lens prescriptions. This combination reflects a realistic scenario where a patient may need a correction for myopia with a negative value, while also needing a slight correction for hyperopia with a positive value. The other options display power values that, while possible, may not uniformly reflect the practical range of spherical lens powers traditionally seen in clinical practice. Specifically, combinations such as +3.00 or higher negative values may not be as frequently used together, and lighter powers may not reflect severe refractive errors. Thus, the combination in the selected answer presents a balanced and plausible set of lens powers, aligning well with typical prescriptions encountered in optometric practice.