American Board of Ophthalmology (ABO) Practice Exam

Which type of distortion is commonly associated with high minus lenses?

1. Barrel distortion

2. Pincushion distortion

3. Chromatic aberration

4. Spherical aberration

The correct answer is: Barrel distortion

The choice of barrel distortion in relation to high minus lenses is correct because this type of distortion results from the optical characteristics of such lenses. High minus lenses, which have a strong concave shape, cause incoming light rays to converge inward more directly than they would with less powerful lenses. This compression of light rays leads to an apparent expansion of objects seen through the edges of these lenses. Consequently, straight lines may bow outward, which is the defining feature of barrel distortion. Barrel distortion typically manifests when the magnification decreases towards the edges of the field of view, creating the illusion that objects are bulging outwards. High minus lenses exacerbate this effect, especially at the periphery of the lens, leading to noticeable distortion. In contrast, the other types of distortions mentioned do not apply in the same way with high minus lenses. Pincushion distortion, for instance, would result in lines appearing to bow inward, which is more characteristic of high plus lenses or certain types of digital processing. Chromatic aberration involves the dispersion of light into different colors, irrelevant to the specific distortions observed in high minus lenses. Spherical aberration relates to the inability of a lens to bring all colors to the same focal point due to its shape,