ABO Low Vision & Rehabilitation 4 — Questions and Answers
Question 1: Which of the following is the correct definition of 'legal blindness' in the United States for purposes of federal benefits eligibility?
- Best-corrected visual acuity of 20/200 or worse in the better eye, OR visual field of 20 degrees or less in the better eye (Correct answer)
- Visual acuity of 20/400 or worse in both eyes without correction
- Best-corrected acuity of 20/100 or worse in both eyes
- Total absence of light perception in both eyes
Correct answer: Best-corrected visual acuity of 20/200 or worse in the better eye, OR visual field of 20 degrees or less in the better eye
U.S. federal law defines legal blindness as BCVA ≤ 20/200 in the better-seeing eye or a visual field diameter ≤ 20° in the better eye.
Question 2: A patient uses a 10D spectacle-mounted magnifier for near work. Approximately how far from the eye should the reading material be placed for optimal focus?
- 10 cm (Correct answer)
- 25 cm
- 40 cm
- 50 cm
Correct answer: 10 cm
The focal length of a 10D lens is 1/10 = 0.10 m = 10 cm, so material must be placed at 10 cm from the lens for the emergent rays to be parallel (focused at infinity).
Question 3: Which instrument is considered the gold standard for mapping the central visual field and identifying scotomas in low vision patients with macular disease?
- Goldmann kinetic perimetry
- Humphrey automated static perimetry (10-2 pattern)
- Microperimetry (fundus-controlled perimetry) (Correct answer)
- Tangent screen testing at 1 meter
Correct answer: Microperimetry (fundus-controlled perimetry)
Microperimetry simultaneously maps visual sensitivity and retinal fixation behavior on a fundus image, making it the gold standard for evaluating macular scotomas and PRL in low vision.
Question 4: When fitting a patient with a prism half-eye spectacle for a hemianopia, the base direction of the Fresnel prism is placed toward the blind field. This displaces images in which direction?
- Toward the apex of the prism, away from the blind field
- Toward the base of the prism, into the seeing field
- Toward the blind field, expanding its apparent boundary (Correct answer)
- No image displacement occurs; only magnification changes
Correct answer: Toward the blind field, expanding its apparent boundary
A prism displaces images toward its apex; because the base is toward the blind field, the apex points into the seeing field, and images in the blind field are shifted toward the seeing side — effectively moving blind-field objects into the patient's seeing hemifield.
Question 5: An elderly low vision patient reports difficulty recognizing faces but can still read large print. This symptom pattern most suggests damage to which visual processing pathway?
- The ventral ('what') stream, possibly involving the fusiform face area (Correct answer)
- The dorsal ('where') stream controlling spatial awareness
- The optic radiations in the temporal lobe
- The magnocellular pathway for motion detection
Correct answer: The ventral ('what') stream, possibly involving the fusiform face area
Face recognition is processed by the ventral stream, particularly the fusiform face area; selective impairment of this function with preserved reading suggests a cortical or higher-order perceptual deficit.
Question 6: In the context of low vision rehabilitation, 'relative distance magnification' is achieved by:
- Using a stronger convex lens to enlarge the retinal image
- Moving the object closer to the eye to increase the visual angle (Correct answer)
- Adding a Galilean telescope to the spectacle frame
- Increasing the ambient illumination on the object
Correct answer: Moving the object closer to the eye to increase the visual angle
Relative distance magnification works by reducing the viewing distance; halving the distance doubles the visual angle and thus the effective magnification without any optical device.
Question 7: Which functional goal is most appropriate to establish first when beginning a low vision rehabilitation program with a newly diagnosed patient?
- Achieving 20/20 acuity with optical aids
- Identifying the patient's own priority tasks and setting patient-centered functional goals (Correct answer)
- Prescribing the highest magnification device available
- Training the patient to use a white cane immediately
Correct answer: Identifying the patient's own priority tasks and setting patient-centered functional goals
Patient-centered goal setting ensures rehabilitation targets what matters most to the individual, improving motivation, compliance, and ultimately functional outcomes.
ABO Low Vision & Rehabilitation 4
Which of the following is the correct definition of 'legal blindness' in the United States for purposes of federal benefits eligibility?