American Board of Opticianry (ABO) Practice Test

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What is the total power of the prescription +2.00 -2.00 x 090?

Plano
-2.00
+2.00
+4.00

The correct answer is: Plano

The prescription +2.00 -2.00 x 090 represents a spherical power of +2.00 and a cylindrical power of -2.00 at an axis of 090 degrees. These powers can also be written as Plano for the spherical power and -2.00 for the cylindrical power. The total power of the prescription, also known as the spherical equivalent, is determined by adding the spherical power and half of the cylindrical power. Therefore, the total power of this prescription is +2.00, making option A the correct answer. Option B (-2.00) and C (+2.00) represent individual powers and not the total power. Option D (+4.00) is incorrect as it is the sum of the spherical and cylindrical powers, which is not the correct way to calculate the total power of a prescription.