ABO Low Vision & Rehabilitation 4

Question 1

Which of the following is the correct definition of 'legal blindness' in the United States for purposes of federal benefits eligibility?

Accepted 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

Answer

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?

Accepted Answer

10 cm

Answer

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?

Accepted Answer

Microperimetry (fundus-controlled perimetry)

Answer

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?

Accepted Answer

Toward the blind field, expanding its apparent boundary

Answer

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?

Accepted Answer

The ventral ('what') stream, possibly involving the fusiform face area

Answer

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.

ABO - American Board of Optometry Practice Test

ABO - American Board of Optometry Practice Test

ABO Low Vision & Rehabilitation 4