Refractive Errors and Vision Conditions

Vocabulary flashcards defining common vision conditions and refractive errors, including myopia, hyperopia, presbyopia, and astigmatism.

Myopia (Nearsightedness)

A refractive error where light rays entering the eye converge in front of the retina rather than directly on it, occurring when the eyeball is too long relative to its focusing power or the cornea is excessively curved, causing nearby objects to appear clear while distant objects appear blurred.

Hyperopia (Farsightedness)

A refractive error where parallel light rays entering the eye focus behind the retina when the eye is at rest, typically occurring because the eyeball is too short front-to-back or the focal power of the lens and cornea is too weak, causing distant objects to usually be seen clearly while close objects appear blurred.

Presbyopia

An age-related loss of accommodation where the crystalline lens gradually loses its elasticity, reducing the eye's ability to change shape and focus on close objects; it is a natural aging process of the internal lens mechanism rather than a structural eyeball length defect.

Astigmatism

A refractive error caused by an irregular, asymmetrical curvature of the cornea or crystalline lens (shaped more like a football than a basketball), where light rays entering along different meridians focus at different focal points relative to the retina, leading to distorted or blurred vision at all distances.