Your patient has 10/100 vision at 10 feet. What is the JND?

Your patient has 10/100 vision at 10 feet. What is the JND?

• A. 0.50
• B. 2.00
• C. 4.00
• D. 1.00

Answer: (D)

JND is the smallest change in visual acuity a person can detect when reading a chart. It represents how little a patient must improve or worsen to notice a difference. From 10/100 at 10 feet, the baseline acuity corresponds to a certain step on the chart. In this exam’s scoring, the smallest reliably noticeable change from that starting point is represented as 1.00. So the Just Noticeable Difference in this context is 1.00. The other numbers would imply bigger leaps than the smallest detectable step (for example, a much larger change like 2.00 or 4.00, or a smaller fractional change like 0.50), which isn’t the minimal detectable difference at this acuity level.

JND is the smallest change in visual acuity a person can detect when reading a chart. It represents how little a patient must improve or worsen to notice a difference.

From 10/100 at 10 feet, the baseline acuity corresponds to a certain step on the chart. In this exam’s scoring, the smallest reliably noticeable change from that starting point is represented as 1.00. So the Just Noticeable Difference in this context is 1.00.

The other numbers would imply bigger leaps than the smallest detectable step (for example, a much larger change like 2.00 or 4.00, or a smaller fractional change like 0.50), which isn’t the minimal detectable difference at this acuity level.