Illinois Vision Certification Practice Test

Which statement is TRUE regarding a cylindrical lens?

1. It corrects hyperopia.

2. It causes parallel rays of light to form a line of focus.

3. It only corrects presbyopia.

4. It is not used in vision correction.

The correct answer is: It causes parallel rays of light to form a line of focus.

A cylindrical lens is designed specifically to correct for astigmatism, which is a refractive error caused by an irregular shape of the cornea or lens. The unique structure of a cylindrical lens allows it to focus light into a line rather than a single point. This is particularly beneficial for individuals with uneven corneal curvature, as it addresses the varying focal points associated with astigmatism. The statement that a cylindrical lens causes parallel rays of light to form a line of focus accurately captures this fundamental characteristic. By bending light in a specific way, the lens ensures that light rays entering the eye converge along a line, thus allowing for improved clarity and focus for those affected by astigmatism. The other statements do not reflect the purpose or function of cylindrical lenses accurately. For example, while they can be part of a prescription that addresses hyperopia or presbyopia, they are not exclusively used for these conditions. Additionally, cylindrical lenses are indeed employed in vision correction, contrary to the claim that they are not used for this purpose. This understanding emphasizes the relevance and utility of cylindrical lenses in the broader context of corrective eyewear.