COT Low Vision and Optical Aids 5 — Questions and Answers
Question 1: Which of the following is a key advantage of an electronic magnification device (CCTV/video magnifier) over optical magnifiers for a patient with severe low vision?
- Lower cost
- Greater portability
- Ability to adjust contrast and reverse polarity (Correct answer)
- No need for lighting
Correct answer: Ability to adjust contrast and reverse polarity
Electronic video magnifiers allow users to adjust magnification, brightness, contrast, and reverse polarity (white-on-black), which optical magnifiers cannot provide.
Question 2: A patient with hemianopia (half-field loss) would MOST benefit from which type of low vision device to expand their visual field awareness?
- High-plus reading spectacles
- Prism or mirror systems (Correct answer)
- Increased magnification telescope
- Pinhole occluder
Correct answer: Prism or mirror systems
Fresnel prisms, sector prisms, or mirror systems are used to shift or expand the field of view for patients with hemianopia, allowing them to detect objects in their blind hemifield.
Question 3: The illumination recommendation for most low vision patients engaged in near tasks is:
- Dim, diffuse overhead lighting to reduce glare
- Bright, directed task lighting from the side or over the shoulder (Correct answer)
- No supplemental lighting beyond ambient room light
- Fluorescent ceiling fixtures only
Correct answer: Bright, directed task lighting from the side or over the shoulder
Most low vision patients benefit from high-intensity, directional task lighting positioned to illuminate the work without causing direct glare in the patient's eyes.
Question 4: When a low vision patient uses a microscopic (high-plus) reading lens of +20D, what is the expected working distance?
- 50 cm
- 25 cm
- 10 cm
- 5 cm (Correct answer)
Correct answer: 5 cm
A +20D lens has a focal length of 1/20 = 0.05 m (5 cm), so the patient must hold reading material at approximately 5 cm from the lens to maintain focus.
Question 5: A COT is instructing a low vision patient on the use of a new optical aid. Which rehabilitation principle is MOST important to address first?
- Selecting the highest possible magnification
- Establishing and training the patient's preferred retinal locus (PRL) (Correct answer)
- Prescribing sunglasses for outdoor use
- Testing distance visual acuity only
Correct answer: Establishing and training the patient's preferred retinal locus (PRL)
Before optimizing optical aids, identifying and training the patient to use their PRL consistently improves the effectiveness of any low vision device and is a foundational rehabilitation step.
Question 6: Which condition would MOST likely lead to referral for orientation and mobility (O&M) training as part of a low vision rehabilitation plan?
- Isolated central scotoma with preserved peripheral vision
- Significant peripheral field loss or tunnel vision (Correct answer)
- Mild reduction in contrast sensitivity
- Unilateral vision loss with full field in the fellow eye
Correct answer: Significant peripheral field loss or tunnel vision
Patients with significant peripheral field loss or tunnel vision have difficulty with mobility, obstacle detection, and safe navigation, making O&M training an essential component of their rehabilitation.
Question 7: Which statement BEST describes the role of the COT during a low vision evaluation?
- Independently prescribing all low vision optical devices without physician oversight
- Performing preliminary testing, assisting with device trials, and providing patient instruction under the supervising physician (Correct answer)
- Diagnosing the underlying cause of the patient's visual impairment
- Determining final spectacle prescription without physician review
Correct answer: Performing preliminary testing, assisting with device trials, and providing patient instruction under the supervising physician
The COT supports the low vision evaluation by conducting preliminary assessments, assisting during device trials, and educating patients, all under the direction and supervision of the ophthalmologist.
COT Low Vision and Optical Aids 5
Which of the following is a key advantage of an electronic magnification device (CCTV/video magnifier) over optical magnifiers for a patient with severe low vision?