AOA Optics and Refraction 2

Question 1

The vertex distance is clinically important because:

Accepted Answer

Changing it alters the effective power of high-powered lenses

Answer

The effective power of a lens changes with vertex distance; for powers >±4D, failure to account for vertex distance during refraction and dispensing introduces clinically significant error.

Question 2

Snellen acuity of 20/40 means the patient can resolve at 20 feet what a normal eye resolves at:

Accepted Answer

40 feet

Answer

Snellen notation is a ratio: the numerator is the testing distance (20 ft) and the denominator is the distance at which the letter subtends 5 arc minutes for a normal observer.

Question 3

With-the-rule astigmatism is defined as when:

Accepted Answer

The steepest corneal meridian is vertical (near 90°)

Answer

With-the-rule (WTR) astigmatism has maximum corneal power vertically (90°±30°), which is the most common pattern in children and young adults.

Question 4

The Purkinje-Sanson images are reflections from the four surfaces of the eye used to:

Accepted Answer

Locate the position of the crystalline lens and assess its clarity

Answer

The four Purkinje-Sanson images are virtual reflections from the anterior cornea, posterior cornea, anterior lens, and posterior lens, used historically to locate the lens and detect cataracts.

Question 5

Which lens aberration causes peripheral blur and is addressed by aspheric lens designs?

Accepted Answer

Oblique astigmatism (marginal astigmatism)

Answer

Oblique astigmatism occurs when oblique rays through the peripheral lens produce different focal distances in the sagittal and tangential planes, causing peripheral distortion corrected by aspheric designs.

AOA - American Optometric Association Practice Test

AOA - American Optometric Association Practice Test

AOA Optics and Refraction 2