JCAHPO Corrective Lenses 3

Question 1

What does 'base curve' refer to in the context of ophthalmic lenses?

Accepted Answer

The front surface power of the lens

Answer

The base curve is the curvature of the front (anterior) surface of an ophthalmic lens, measured in diopters.

Question 2

A patient with +4.00 D of hyperopia wears contact lenses. After fitting, the over-refraction shows -0.50 D. What is the revised contact lens power?

Accepted Answer

+3.50 D

Answer

Over-refraction result is added algebraically: +4.00 + (-0.50) = +3.50 D.

Question 3

What is the primary advantage of high-index lens materials over standard CR-39 plastic?

Accepted Answer

Thinner and lighter lenses for high prescriptions

Answer

High-index materials bend light more efficiently, producing thinner and lighter lenses for patients with high refractive errors.

Question 4

Which axis orientation describes a 'with-the-rule' astigmatism in spectacle correction?

Accepted Answer

Axis near 90° (vertical)

Answer

With-the-rule astigmatism has the steepest corneal meridian vertical, so the correcting minus cylinder axis is near 180°; however, the plus cylinder axis (and thus the steeper meridian) is near 90°.

Question 5

Anti-reflective (AR) coating on spectacle lenses primarily works by:

Accepted Answer

Destructive interference canceling reflected light waves

Answer

AR coatings use thin film layers that create destructive interference, canceling reflected light and improving light transmission.

(JCAHPO) International Joint Commission Allied Health Personnel in Ophthalmology Practice Test

(JCAHPO) International Joint Commission Allied Health Personnel in Ophthalmology Practice Test

JCAHPO Corrective Lenses 3