Ametropia/Ophthalmic Optics Flashcards

Anisometropia is clinically significant when the difference in refractive error between the two eyes exceeds approximately:

Answer: 1.00 D

A difference of 1.00 D or more between eyes is generally considered clinically significant anisometropia that may affect binocular vision.

What is the prismatic effect at a point 8 mm below the optical center of a -5.00 D lens (Prentice's rule)?

Answer: 4.0Δ base-up

P = c × F = 0.8 cm × 5.00 = 4.0Δ; a minus lens produces base-up prism in the inferior portion (base toward optical center).

Which of the following best describes 'lenticular myopia'?

Answer: Myopia caused by increased curvature or index of the crystalline lens

Lenticular myopia results from optical changes within the crystalline lens, such as increased curvature, thickness, or index of refraction.

The power of a spherical refracting surface is calculated using which formula?

Answer: P = (n' - n) / r

The power of a single refracting surface is P = (n' - n) / r, where n' is the exit medium, n is the entry medium, and r is the radius in meters.

A patient with high myopia (-10.00 D) is best served by high-index lens materials primarily because:

Answer: They reduce lens thickness and weight

Higher index materials allow the same power to be achieved with less curvature, resulting in thinner and lighter lenses for high prescriptions.

Slab-off (bicentric grinding) is used in spectacle lenses to compensate for:

Answer: Vertical prism imbalance at near in anisometropic patients

Slab-off creates vertical prism in one lens to equalize the differential vertical prismatic effect that occurs at the near reading position in anisometropia.

Which of the following is the correct definition of the 'far point' in hyperopia?

Answer: A virtual point located behind the eye

In hyperopia, the far point is a virtual conjugate point located behind the eye because the relaxed eye's focal point falls behind the retina.