ABO NOCE Basic Opticianry Ophthalmic Optics and Principles 4

Question 1

Using Prentice's Rule, what is the prismatic effect at a point 8 mm from the optical center of a +5.00 D lens?

Accepted Answer

4Δ

Answer

Prentice's Rule: Prism (Δ) = d(cm) × F = 0.8 × 5.00 = 4.00Δ.

Question 2

What is the purpose of the 'crossed cylinder' test in refraction?

Accepted Answer

To refine cylinder axis and power

Answer

The Jackson crossed cylinder (JCC) is used to precisely refine both the axis and power of the correcting cylinder during subjective refraction.

Question 3

What is 'vergence' in the context of ophthalmic optics?

Accepted Answer

The curvature of wavefronts of light

Answer

Vergence describes the degree of convergence or divergence of a wavefront of light, measured in diopters.

Question 4

A lens with a refractive index of 1.74 compared to 1.50 will be:

Accepted Answer

Thinner and lighter

Answer

Higher index materials bend light more strongly, allowing thinner lens profiles; modern high-index materials are also less dense, making lenses lighter.

Question 5

What is the effect of increasing pantoscopic tilt on the effective power of a lens?

Accepted Answer

It induces plus sphere and minus cylinder

Answer

Increasing pantoscopic tilt introduces oblique astigmatism, effectively adding plus sphere power and a minus cylinder component to the lens's effective prescription.

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Practice Test

ABO NOCE Basic Opticianry Ophthalmic Optics and Principles 4