Slight redness of the eyes is usually caused by the following reasons: a. Conjunctival congestion caused by excessive eye use and visual fatigue, usually seen after staying up late reading books or playing with cell phones, and also accompanied by symptoms such as eye dryness, tingling, foreign body sensation, slight blurred vision, sore eyes and dizziness. Second, corneoconjunctival dryness, commonly seen in middle-aged and elderly people, occurs when the cornea is exposed to air due to insufficient tear secretion in the eye, which causes eye surface irritation and can also lead to red eyes. Third, conjunctivitis, associated with inattention to eye hygiene, leads to infection of the membranous structures on the surface of the white eyeball, triggering congestion and redness. IV. Reactive conjunctival congestion triggered by lesions within the eye, such as iridocyclitis, uveitis, glaucoma, etc.