ABO NOCE Basic Opticianry Refractive Errors and Their Optical Correction

Question 1

Which refractive condition results from the axial length of the eye being too long, causing parallel light to focus anterior to the retina?

Accepted Answer

Myopia

Answer

In myopia (nearsightedness) the eyeball is axially too long, so the focal point of parallel rays falls in front of the retina. Concave (minus) lenses are prescribed to diverge light and shift the focus back onto the retinal plane.

Question 2

A patient's prescription reads +3.25 DS. Which refractive error does this correct?

Accepted Answer

Hyperopia

Answer

Plus (convex) lenses converge light and correct hyperopia, where the eye is too short and incoming light would focus behind the retina without correction. The +3.25 DS brings the focal point forward to land on the retina.

Question 3

In the prescription -2.00 -1.50 x 090, what does the cylindrical component (-1.50 x 090) correct?

Accepted Answer

Astigmatism

Answer

The cylinder power and its axis correct astigmatism — a refractive error caused by an unequally curved cornea or lens that produces two separate focal lines instead of a single focal point. The axis 090 indicates the meridian of no cylinder power (the sphere-only meridian).

Question 4

At approximately what age does presbyopia typically become clinically symptomatic, requiring a reading addition?

Accepted Answer

40–45 years

Answer

Presbyopia results from progressive hardening of the crystalline lens, which reduces accommodative amplitude. Symptoms typically become noticeable around age 40–45, and the required add power continues to increase until approximately the mid-60s.

Question 5

What is the spherical equivalent of the prescription -3.00 -2.00 x 180?

Accepted Answer

-4.00 D

Answer

Spherical equivalent (SE) = sphere + (cylinder ÷ 2) = -3.00 + (-2.00 ÷ 2) = -3.00 + (-1.00) = -4.00 D. The spherical equivalent represents the single sphere power that most closely approximates the mean refractive effect of a sphero-cylindrical lens.

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Refractive Errors and Their Optical Correction