CO CO Optical Devices & Low Vision Rehabilitation 2 — Questions and Answers
Question 1: Eccentric viewing training teaches patients with a central scotoma to:
- Ignore the blind area completely
- Use an intact peripheral retinal area as the preferred retinal locus (PRL) (Correct answer)
- Improve fixation by patching the fellow eye
- Read exclusively with high-power magnification
Correct answer: Use an intact peripheral retinal area as the preferred retinal locus (PRL)
Eccentric viewing training helps patients with central scotoma develop a preferred retinal locus in intact peripheral retina as a functional substitute for the damaged fovea.
Question 2: Telescope magnification is calculated as the ratio of:
- Exit pupil diameter to entrance pupil diameter
- Eyepiece lens power to objective lens power (Correct answer)
- Objective lens power to eyepiece lens power
- Field of view to angular subtense
Correct answer: Eyepiece lens power to objective lens power
Telescope magnification equals the power of the eyepiece divided by the power of the objective lens (equivalently, focal length of the objective divided by focal length of the eyepiece).
Question 3: A patient with homonymous hemianopia may benefit from which optical device to improve awareness of the blind hemifield?
- High-add reading glasses
- Reverse telescope (minifier)
- Sector prism or mirror placed on the hemianopic side (Correct answer)
- Tinted lenses
Correct answer: Sector prism or mirror placed on the hemianopic side
Sector prisms or Fresnel prisms placed on the hemianopic side of spectacles redirect images from the blind hemifield into the seeing field to alert the patient to objects.
Question 4: In orthoptic management of accommodative esotropia, bifocal or progressive addition lenses are prescribed to:
- Increase accommodative effort
- Reduce near accommodative demand and the associated convergence excess (Correct answer)
- Correct anisometropia
- Stimulate the amblyopic eye
Correct answer: Reduce near accommodative demand and the associated convergence excess
Bifocal or progressive addition lenses reduce near accommodative demand in patients with accommodative esotropia, lessening the convergence excess that drives the near deviation.
Question 5: The magnification needed for a low vision patient is estimated by the formula:
- Required magnification = desired VA denominator ÷ current VA denominator (Correct answer)
- Required magnification = current VA denominator ÷ desired VA denominator
- Required magnification = lens power × working distance
- Required magnification = 1 ÷ current VA in decimal
Correct answer: Required magnification = desired VA denominator ÷ current VA denominator
The required magnification equals the desired visual acuity denominator divided by the current visual acuity denominator (e.g., 20/200 needing 20/40 requires 200/40 = 5× magnification).
Question 6: Compared to hand magnifiers, spectacle-mounted magnifiers offer the primary advantage of:
- Lower cost and portability
- Hands-free use for sustained near tasks (Correct answer)
- Greater working distance from the page
- No adaptation period required
Correct answer: Hands-free use for sustained near tasks
Spectacle-mounted magnifiers provide hands-free magnification, allowing patients to use both hands freely for near tasks such as reading or craftwork.
CO CO Optical Devices & Low Vision Rehabilitation 2
Eccentric viewing training teaches patients with a central scotoma to: