Practice Quiz

Ophthalmic Technician

Category - Visual Assessment

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On what principle is the optotype, used in Snellen’s vision chart, based upon?
  1. Each letter subtends an angle of 5 minutes of arc and each limb of the optotype subtends an angle of 1 minute of arc at the nodal point of the eye
  2. Each letter subtends an angle of 15 minutes of arc and each limb of the optotype subtends an angle of 1 minute of arc at the nodal point of the eye
  3. Each letter subtends an angle of 1 minutes of arc and each limb of the optotype subtends an angle of 5 minutes of arc at the nodal point of the eye
  4. Each letter subtends an angle of 15 minutes of arc and each limb of the optotype subtends an angle of 15 minutes of arc at the nodal point of the eye
Explanation
Answer: A - The principle on which the optotype used in Snellen’s vision chart is based on states that each letter subtends an angle of 5 minutes of arc and each limb of the optotype subtends an angle of 1 minute of arc at the nodal point of the eye. Regardless of the size of the optotype, each follows the above principle.
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