Red eyes can indicate a relatively benign condition, such as staying up late and feeling fatigued or getting a small foreign body such as an eyelash into the eyes. Red eyes can be the result of conditions that cause inflammation, and can also result from an eye infection, such as conjunctivitis or herpes simplex. Red eyes can also be a symptom of eye trauma, such as corneal abrasion, foreign body, or chemical burns of the eyes.
01 Red Eye
Animation credit: American Academy of Ophthalmology