Definition
Conditions in which the eye does not bend (refract) incoming light correctly onto the retina, producing a blurred image. The most common types are nearsightedness (myopia), farsightedness (hyperopia), astigmatism (uneven curvature of the cornea or lens), and presbyopia (age-related loss of near focus). These disorders are typically corrected with eyeglasses or contact lenses.
Plain English
Vision problems where the eye can't focus light properly, so things look blurry. Glasses or contacts usually fix it.
Context Anchor
Seen in night vision discussions because small focusing problems can become more noticeable when light is low and visual details are harder to pick out.
Derivation
From Latin refringere, 'to break up' — light is 'broken' or bent as it passes through the eye. A refractive disorder is one where that bending doesn't land the image cleanly on the retina.
Why Pilots Care
Uncorrected refractive disorders reduce the amount of usable light that reaches the retina at night, slowing dark adaptation and raising the chance of missing runway lights, obstacles, or terrain.
Analogy
It is like a camera that is slightly out of focus: the scene is there, but the image is not sharp until the focus is corrected.
Intuition Check
Do not read “refractive” as “reflective.” This term is about how the eye bends light to focus an image, not how it bounces light back.
Example Sentence 1
Pilots with refractive eye disorders must wear their prescribed glasses or contacts while flying if their medical certificate requires it.
Example Sentence 2
Even mild refractive eye disorders can delay the eyes' adjustment to darkness, so pilots complete a thorough preflight vision check before night flights.