For distance vision, the lens needs to be thin and elliptical . For near vision, the lens must be thick and spherical .

Question

BlackTom AI · Accepted Answer

To unpack the statement, we consider how the eye changes focus for distance vs. near tasks.
Option 1: thin and elliptical. For distance vision, the lens becomes flatter (thinner) to reduce its optical power, allowing light from distant objects to focus on the retina. The mention of 'elliptical' describes a non-circular, more flattened curvature shape, which aligns with the idea of reduced refractive strength compared to near vision. In short, distance vision requires a thinner lens with less curvature, which supports this option as correct.
Option 2: thick and spherical. For near vision, the lens increases its optical power by becoming thicker and more curved, enabling the eye to focus on close objects. A more spherical (rounded) surface contributes to higher refractive power, and the lens thickens due to accommodation. Therefore, this describes the near-vision adjustment accurately, making this option correct as well.
A few clarifications to avoid common misconceptions: while the core idea is that distance vision uses a flatter, thinner lens and near vision uses a thicker, more curved lens, real ocular surfaces are not perfect geometric spheres or ellipses, and the shape change is a continuum rather than a binary switch. The key concept is the trend—flatter/thinner for distance, steeper/thicker for near—rather than insisting on exact geometric classifications in every anatomical depiction.

BIOLOGY 211-B09C HW #14: Visual System

For distance vision, the lens needs to be thin and elliptical . For near vision, the lens must be thick and spherical .

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