The distance of 22.22 mm in the Reduced Eye model is associated with which concept?

• A. Anterior chamber depth
• B. Axial length
• C. Pupil diameter
• D. Lens thickness

Answer: (B)

In the Reduced Eye model, the distance of 22.22 mm represents the axial length—the straight-line distance along the optical axis from the cornea to the retina. This fixed distance is used to relate angles in the visual field to linear sizes on the retina, making angular measurements easy to translate into retinal image sizes (retinal image size ≈ angular size in radians × axial length). The other options—anterior chamber depth, lens thickness, and pupil diameter—are different anatomical distances that are not set to this standard value in the Reduced Eye. Eyeballing the concept this way helps you see why 22.22 mm is tied to axial length: it’s the fundamental distance that connects what you see in space to what lands on the retina in this simplified model.