Which of the following options is not a type of refractive error?

Conjunctivitis is the correct choice as it is not a type of refractive error. Refractive errors are conditions that affect how the eye focuses light, resulting in blurred vision, and they include myopia (nearsightedness), astigmatism (uneven curvature of the eye), and presbyopia (age-related difficulty in focusing on close objects).

In contrast, conjunctivitis, commonly known as pink eye, is an inflammation or infection of the conjunctiva—the membrane covering the white part of the eye and the inner eyelids. This condition can arise from various causes, such as allergies, bacteria, or viruses, but it does not involve the eye's focusing ability or structure in the way that refractive errors do. Understanding this distinction is crucial for vision professionals as it helps in correctly diagnosing and managing various eye conditions.