Conjunctivitis, commonly known as pink eye, is an inflammation of the conjunctiva, the thin, clear membrane that covers the white part of the eye and the inner surface of the eyelids. When the small blood vessels in this membrane become inflamed, they become more visible, giving the eye its characteristic reddish or pink appearance. For the vast majority of people, pink eye is a temporary and self-limiting condition that does not cause permanent vision loss. While the symptoms can be uncomfortable, blurred vision is usually a temporary result of discharge or inflammation. Permanent vision damage is an extremely rare complication, occurring only in severe, untreated cases or those caused by specific, aggressive pathogens.
The Primary Causes of Pink Eye
Conjunctivitis is broadly categorized into three main types, each with a different cause and method of transmission. Viral conjunctivitis is the most common form, highly contagious, and often caused by the same viruses responsible for the common cold. This type typically produces a watery discharge and can be spread through respiratory droplets or by touching contaminated surfaces.
Bacterial conjunctivitis is less frequent, but also very contagious. This infection is characterized by a thick, sticky discharge that can cause the eyelids to crust over and stick together, particularly upon waking. Bacteria from a person’s own skin or respiratory system, or contact with contaminated items like uncleaned contact lenses, are common sources.
The third major type is allergic conjunctivitis, which is not contagious. It occurs when the immune system reacts to allergens like pollen, dust mites, or pet dander. This form usually affects both eyes and is often accompanied by intense itching and a clear, watery discharge.
How Conjunctivitis Affects Vision
The common symptoms of pink eye, such as a gritty feeling, redness, and discharge, are usually confined to the conjunctiva and do not directly damage the structures responsible for sight. Any temporary blurriness experienced is typically due to a buildup of discharge or excessive tearing on the eye’s surface. This superficial blurring resolves completely once the inflammation subsides and the discharge clears.
Permanent vision impairment only becomes a possibility if the infection extends beyond the conjunctiva to affect the cornea, the clear, dome-shaped outer layer of the eye. This serious complication is known as keratitis. Severe bacterial infections or aggressive viral strains, like the herpes simplex virus, can cause keratitis and lead to open sores called corneal ulcers.
If these corneal ulcers are left untreated, the resulting deep inflammation can lead to corneal scarring. Scarring creates an opaque spot that blocks or distorts the path of light entering the eye, which can result in a permanent reduction in vision. This represents the primary mechanism by which conjunctivitis can result in long-term damage.
Recognizing Serious Symptoms and Seeking Care
While most pink eye cases resolve without intervention, certain symptoms act as warning signs that require immediate medical attention. One significant red flag is severe eye pain, especially pain that feels deep within the eye, rather than just the surface irritation typical of mild conjunctivitis. This intense discomfort can suggest that the deeper layers of the eye, such as the cornea, are involved.
Another important symptom to watch for is a sudden or persistent change in vision, such as noticeable blurring that does not clear after blinking or wiping away discharge. Sensitivity to light, known as photophobia, is also a serious sign, as it indicates a potential irritation or inflammation of the cornea. Other concerning indicators include intense redness that worsens rapidly, or the appearance of a white spot on the cornea.
Patients who wear contact lenses must be especially vigilant, as they are at a higher risk for developing keratitis and corneal ulcers. Any contact lens wearer who develops pink eye symptoms should stop wearing their lenses immediately and seek prompt care if symptoms do not improve quickly. Immediate medical evaluation is also necessary for any newborn baby presenting with red, sticky eyes, as infant conjunctivitis can be particularly severe.
Treatment and Preventing Spread
Treatment for pink eye depends entirely on the underlying cause, which is why accurate diagnosis is helpful. Viral conjunctivitis has no specific treatment and is managed with supportive care, such as cool compresses and artificial tears, allowing the virus to simply run its course over one to two weeks. Bacterial conjunctivitis is often treated with antibiotic eye drops or ointments, which can speed recovery and reduce the risk of complications.
Allergic conjunctivitis is managed by avoiding the allergen and using cool compresses, sometimes along with antihistamine eye drops or oral medications to control the immune response. Regardless of the cause, preventing the spread of infectious pink eye relies heavily on rigorous personal hygiene. Consistent and thorough handwashing is the single most effective measure for limiting transmission.
It is also important to avoid touching or rubbing the affected eye and to never share personal items like towels, washcloths, or pillowcases. Contaminated items such as eye makeup or contact lenses and cases used during an infection should be discarded to prevent reinfection. These practical steps help contain the highly contagious viral and bacterial forms of the infection.