COT Low Vision and Optical Aids 4 — Questions and Answers
Question 1: A patient with a central scotoma due to macular degeneration is being taught eccentric viewing. Which direction should they typically be instructed to look to use their preferred retinal locus (PRL)?
- Directly at the target
- Slightly to one side of the target (Correct answer)
- Downward from the target
- Upward from the target
Correct answer: Slightly to one side of the target
Patients with central scotomas use eccentric viewing by shifting their gaze so that the image falls on a functioning area of the retina peripheral to the scotoma, which is typically to one side of the target.
Question 2: Which low vision aid is MOST appropriate for a patient who needs to read price tags and labels while shopping?
- Stand magnifier
- Hand magnifier (Correct answer)
- Spectacle-mounted magnifier
- CCTV/video magnifier
Correct answer: Hand magnifier
A hand magnifier is most practical for spot-reading tasks like price tags and labels because it is portable, easy to use briefly, and requires no special positioning.
Question 3: When prescribing a telescope for a patient with low vision, the primary trade-off compared to a higher-magnification telescope is:
- Decreased image brightness
- Reduced field of view (Correct answer)
- Increased weight
- Longer working distance
Correct answer: Reduced field of view
Higher magnification telescopes provide greater enlargement but significantly reduce the field of view, making scanning and mobility more challenging.
Question 4: A patient uses a 4X hand magnifier to read standard print. If the patient wishes to switch to a stand magnifier that delivers equivalent magnification, what should the COT consider about the stand magnifier's labeled power?
- It will always equal 4X
- It may be labeled higher than 4X due to vergence differences (Correct answer)
- It will always be labeled lower than 4X
- Labeled power is irrelevant for stand magnifiers
Correct answer: It may be labeled higher than 4X due to vergence differences
Stand magnifiers have a built-in object distance that produces divergent light, so patients using them with spectacles experience less net magnification than the labeled power; thus equivalent performance may require a higher-labeled stand magnifier.
Question 5: Which contrast-enhancement technique is MOST beneficial for a low vision patient with reduced contrast sensitivity?
- Increasing room temperature
- Using yellow-tinted lenses or filters (Correct answer)
- Reducing ambient lighting
- Wearing a wide-brimmed hat
Correct answer: Using yellow-tinted lenses or filters
Yellow or amber tinted lenses and filters enhance contrast by blocking short-wavelength (blue) light scatter, improving edge definition for patients with reduced contrast sensitivity.
Question 6: A patient with 20/200 visual acuity wants to watch television from 10 feet away. Which type of low vision aid is BEST suited for this distance task?
- Handheld magnifier
- Reading spectacles with high plus power
- Monocular or binocular telescope (Correct answer)
- Stand magnifier
Correct answer: Monocular or binocular telescope
Telescopes are designed for distance tasks and allow the patient to magnify a distant target such as a television while maintaining a practical viewing distance.
Question 7: When evaluating a low vision patient's functional reading ability, which measure BEST reflects real-world reading performance beyond just letter acuity?
- Snellen chart distance acuity
- Reading speed in words per minute with continuous text (Correct answer)
- Color discrimination threshold
- Contrast sensitivity at high spatial frequencies only
Correct answer: Reading speed in words per minute with continuous text
Reading speed with continuous text (assessed with tools like the MNRead chart) captures the patient's ability to read fluently and reflects functional reading performance better than letter acuity alone.
COT Low Vision and Optical Aids 4
A patient with a central scotoma due to macular degeneration is being taught eccentric viewing.
Which direction should they typically be instructed to look to use their preferred retinal locus (PRL)?