What is the width of the optic disc in degrees?

• A. 3
• B. 5
• C. 7
• D. 4

Answer: (B)

The width of the optic disc in degrees reflects its angular size on the retina, not just its physical size. In a typical eye, the disc diameter is about 1.5–1.8 mm. Roughly, 1 degree on the retina corresponds to about 0.3 mm near the optic nerve, so 1.5–1.8 mm translates to roughly 5–6 degrees of visual angle. Because exam conventions typically round to a simple value, five degrees is the standard estimate for the optic disc width.

So five degrees is the best fit for the usual, clinically observed width. A disc that’s about 0.9 mm would be closer to about 3 degrees, a diameter around 1.2–1.3 mm to about 4 degrees, and a diameter near 2.0 mm to about 7 degrees; these don’t align as well with the common anatomical range.