Eye disease · Overview

Red eyes

Red eyes

Dr. med. Ken Selde

FMH specialist doctor for ophthalmology and eye surgery

Red eyes have a wide variety of causes, with symptoms ranging from watering to long-term pain. It is therefore recommended that you seek clarification from a specialist.


Red eyes are the most common complaint prompting patients to visit the ophthalmologist. It is without a doubt the clearest sign that something is wrong with the eye. Red eyes may occur on one side only, both sides at once, or in succession.



There can be a wide variety of causes: it may be a harmless issue, a serious one, or in rare and extreme cases a problem which could result in blindness. The simplest option is to differentiate between causes coming from outside the body (exogenous) or inside the body (endogenous):


Exogenous causes:

  • Foreign bodies
  • Dust
  • Irritants such as cosmetics
  • Allergies
  • Sun
  • Wind
  • Contact lens remnants
  • Tobacco smoke
  • Lack of sleep
  • Air conditioning
  • Accident, impact injuries etc.


Endogenous causes:

  • Infections – bacterial, viral, fungal
  • Specific allergies
  • Burst blood vessels
  • Immune reactions, allergies, rheumatic conditions
  • Inflammation of the eyelid
  • Eyelid deformities
  • Incorrectly positioned eyelashes
  • Incomplete eyelid closure
  • Styes
  • Dry eyes
  • Corneal diseases
  • Scleral diseases
  • Iris diseases
  • Retinal diseases
  • Optic nerve diseases
  • Thyroid disorders
  • Hypertension
  • Diabetes mellitus
  • Brain diseases
  • Glaucoma
  • Medication etc.


Symptoms cover an entire spectrum, ranging from no symptoms at all to sharp, blunt, throbbing, or long-term pain, in extreme cases with nausea or even vomiting. Vision is generally impaired, the eyes may water or be sensitive to glare, color vision is affected, and in extreme cases, the patient sees rainbow colors around lights and so on.


An ophthalmologist will diagnose the cause in each particular case using the patient’s medical history, physical microscopic examinations, swabs, and often also interdisciplinary consultation with colleagues. Unfortunately, this list does not make it clear whether or not you are dealing with an emergency, which is why it is important to consult an ophthalmologist.