Red eye
Red eye is a common ocular symptom characterized by visible redness of the eye due to dilation and prominence of superficial blood vessels in the conjunctiva or sclera, typically resulting from irritation, inflammation, infection, allergy, or trauma.[1][2] It may affect one or both eyes and is often accompanied by symptoms such as itching, tearing, discharge, or discomfort, though pain suggests potentially serious underlying issues like acute glaucoma or scleritis.[1][3] Among the most frequent causes are viral or bacterial conjunctivitis, which accounts for many cases and spreads easily through contact; allergic responses to environmental triggers like pollen; and noninfectious factors including dry eye from prolonged screen use or environmental dryness.[1][3] While mild instances frequently resolve with supportive measures such as artificial tears or cool compresses, evaluation by a healthcare professional is essential for cases involving vision changes, severe pain, photophobia, or lack of improvement within days, as these may indicate urgent conditions requiring prompt intervention to prevent complications like corneal damage or vision loss.[1][4]Eye-related conditions and effects
Medical red eye
Red eye, medically termed as such, refers to the visible prominence of superficial blood vessels in the conjunctiva or sclera, resulting from their dilation due to irritation, inflammation, infection, or injury. This symptom arises when blood vessels on the eye's surface expand in response to various stimuli, often presenting unilaterally or bilaterally without inherent threat to vision in benign cases.[2] Conjunctivitis accounts for the majority of instances, comprising infectious (bacterial or viral), allergic, or irritative forms, while other etiologies include dry eye syndrome, subconjunctival hemorrhage, uveitis, acute glaucoma, or trauma.[5][3] Red eye presentations constitute approximately 2-3% of primary care office visits, underscoring their frequency yet variability in severity.[6] Common triggers encompass environmental irritants, allergens, microbial pathogens, or mechanical factors like foreign bodies or contact lens overuse, leading to localized vascular response. Bacterial conjunctivitis, often caused by Staphylococcus or Streptococcus species, features purulent discharge and is more prevalent in winter months (December to April).[7] Viral forms, typically adenoviral, spread via contact and resolve spontaneously within 1-2 weeks but may mimic serious iritis. Allergic reactions involve histamine-mediated vessel dilation, exacerbated by pollen or dust. Non-infectious causes like subconjunctival hemorrhage—often from coughing or minor trauma—resolve without intervention in 7-14 days, whereas scleritis or episcleritis signal deeper inflammation potentially linked to systemic autoimmune conditions.[5][3]| Category | Examples | Key Features |
|---|---|---|
| Infectious Conjunctivitis | Bacterial (S. aureus, H. influenzae), Viral (adenovirus) | Discharge (purulent vs. watery), contagious, self-limiting in viral cases[7] |
| Allergic/Irritative | Dry eye, allergens | Itching, bilateral, no discharge; exacerbated by low humidity or screens[5] |
| Traumatic/Hemorrhagic | Subconjunctival hemorrhage, abrasion | Sudden onset, pain variable; hemorrhage bright red patch without vision loss[3] |
| Inflammatory/Serious | Uveitis, glaucoma, scleritis | Photophobia, pain, vision changes; requires urgent evaluation to prevent damage[8] |