CO CO Optical Devices & Low Vision Rehabilitation 1 — Questions and Answers
Question 1: Low vision is generally defined as best-corrected visual acuity of:
- Better than 20/40
- 20/70 or worse in the better eye (Correct answer)
- 20/40 in either eye
- Less than 20/200 exclusively
Correct answer: 20/70 or worse in the better eye
Low vision is defined as best-corrected visual acuity of 20/70 or worse in the better eye that cannot be improved with standard optical correction.
Question 2: Fresnel press-on prisms incorporated into a spectacle lens are primarily used to manage:
- Presbyopia
- Diplopia caused by strabismus (Correct answer)
- Myopic astigmatism
- Color vision deficiency
Correct answer: Diplopia caused by strabismus
Fresnel press-on prisms are used to neutralize diplopia by redirecting the visual axis in patients with strabismus, especially when deviation may change over time.
Question 3: Which low vision device uses a strong convex lens resting on reading material to magnify near objects?
- Galilean telescope
- Stand magnifier (Correct answer)
- Reverse telescope
- Prism half-glasses
Correct answer: Stand magnifier
Stand magnifiers use a strong convex lens mounted at a fixed focal distance and rest directly on reading material to provide stable near magnification.
Question 4: When prescribing base-out prism for a patient with esotropia and diplopia, the prism functions by:
- Increasing the angle of deviation
- Redirecting the visual axis nasally to align the diplopic images (Correct answer)
- Reducing accommodative effort
- Expanding the peripheral visual field
Correct answer: Redirecting the visual axis nasally to align the diplopic images
Base-out prism redirects the visual axis nasally, compensating for esotropia and aligning the diplopic images to eliminate double vision.
Question 5: Bioptic telescopes are primarily prescribed to:
- Treat amblyopia in children
- Allow patients with low vision to meet driving visual acuity requirements (Correct answer)
- Improve stereoacuity
- Eliminate diplopia at near
Correct answer: Allow patients with low vision to meet driving visual acuity requirements
Bioptic telescopes are miniature telescopes mounted superiorly in spectacle lenses that allow patients with low vision to spot-check acuity for driving in states that permit bioptic driving.
Question 6: According to Prentice's Rule, the prismatic effect in prism diopters equals:
- Lens power divided by decentration in cm
- Lens power in diopters multiplied by decentration in centimeters (Correct answer)
- Lens power squared
- Decentration in mm divided by lens power
Correct answer: Lens power in diopters multiplied by decentration in centimeters
Prentice's Rule states that prismatic effect (Δ) = lens power (D) × decentration (cm), essential for calculating induced prism from decentered lenses.
CO CO Optical Devices & Low Vision Rehabilitation 1
Low vision is generally defined as best-corrected visual acuity of: