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Conjunctivitis (Pink Eye): Causes, Symptoms, and Treatment

Written by Andrew Le, MD

UpdatedMay 29, 2024

Conjunctivitis, often colloquially referred to as pink eye, refers to inflammation of the conjunctiva – the transparent, delicate mucous membrane that lines the inside of the eyelids and covers the white areas of the eyes.

Conjunctivitis accounts for 1% of all primary care and emergency room visits. The hallmark symptom of this condition is the red or pinkish discoloration in the sclera (whites of the eyes), arising from dilation of the conjunctival blood vessels in response to irritation, infection, or allergy.

This article will provide an extensive overview of the epidemiology, pathophysiology, risk factors, diagnostic workup, management approaches, and preventative strategies pertinent to conjunctivitis.

🔑 Key Takeaways

  • Viral conjunctivitis is the most prevalent infectious cause (75% of cases), while bacterial conjunctivitis accounts for around half of the remaining infectious cases. Allergic conjunctivitis also affects up to 30% of the general population.
  • Conjunctival inflammation arises from direct infection, allergic reactions, or irritative exposure to chemicals/toxins - resulting in the release of inflammatory mediators and vasodilation of fine blood vessels.
  • Risk factors include contact lens use, exposure to infected individuals, compromised immune system, history of atopy, environmental irritant exposure, and young age.
  • Key distinguishing clinical features help identify the specific conjunctivitis subtype to guide appropriate treatment – viral, bacterial, allergic, or irritant.
  • Preventative approaches targeting improved hygiene, avoiding allergens, public health initiatives, and newborn prophylaxis help reduce the societal burden of conjunctivitis.
  • While typically benign, improper conjunctivitis diagnosis/management heightens the risk for recurrent inflammation, permanent corneal damage, and vision changes - highlighting the need for timely assessment.
  • Conjunctivitis represents an extremely prevalent ocular condition with the potential for significant discomfort and vision sequelae, warranting increased clinical suspicion and public health measures.
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Epidemiology and Prevalence

In the US, conjunctivitis is a significant condition, being the most common ocular diagnosis in emergency departments, accounting for almost one-third of all eye-related encounters in these settings​​. This high incidence in emergency departments indicates the widespread nature of the condition, though it should be noted that this only represents cases severe enough to require emergency care and might not fully represent primary care visits.

Globally, allergic conjunctivitis is quite common, affecting around 10% to 30% of the population. These statistics highlight the widespread nature of this type of conjunctivitis across various regions.

Regarding viral conjunctivitis, it remains the most common overall cause of conjunctivitis, accounting for up to 75% of infectious conjunctivitis cases​​​​. In contrast, bacterial conjunctivitis, while still prevalent, is encountered less frequently and is the second most common cause of infectious conjunctivitis​​.

Anatomy and Pathophysiology

The conjunctiva is a transparent mucous membrane composed of non-keratinized stratified squamous epithelial cells interspersed with goblet cells. It mechanically lines the inside of eyelids and sclera, fulfilling several ophthalmic functions:

  • Secretion of mucus and tears to lubricate and protect the eye’s surface
  • Facilitates eyelid movement over the globe of the eye
  • Forms a physical barrier against external pathogens and irritants
  • Allows light transmission to the cornea and internal eye structures

Under normal conditions, the conjunctiva appears relatively colorless. However, when its tiny blood vessels become engorged and dilated in response to inflammation, it leads to the hallmark reddish discoloration seen in conjunctivitis. There are three main mechanisms by which inflammation of the conjunctiva blood vessels occurs:

  1. Infection: Bacterial or viral conjunctivitis triggers an immune reaction and release of inflammatory mediators to combat foreign pathogens. This collateral damage leads to vasodilation and fluid leakage.
  2. Allergy: Exposure to specific allergens activates antibody release. These trigger mast cells within conjunctiva to degranulate, releasing histamine and other inflammatory molecules, which dilate blood vessels.
  3. Irritation: Direct toxicity from exposure to irritant chemicals or physical factors induces cellular damage within the conjunctiva. This stimulates an acute inflammatory response, including vasodilation.

Causes and Risk Factors

Four main etiologies account for the vast majority of acute conjunctivitis cases:

  1. Viral Conjunctivitis: The most common infectious culprit with approximately 80,000 cases per 100,000 instances of acute conjunctivitis. It is primarily caused by adenoviruses entering the eye via infected respiratory droplets or contaminated hands/objects.
  2. Bacterial Conjunctivitis: Account for less than half of infectious cases. Commonly caused by Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae type B, amongst others. Spread by contact with infected eye discharge.
  3. Allergic Conjunctivitis: Due to IgE-mediated hypersensitivity reactions to common environmental allergens like pollens, animal dander, dust mites etc., triggering histamine release. Hereditary influences also play a role.
  4. Irritant Conjunctivitis: Results from direct exposure of eyes to noxious external agents like chemicals, smoke, and particulates, which induce localized cellular damage and inflammatory reaction.

Various risk factors can predispose individuals to developing conjunctivitis. Among these include:

  • Contact lens usage: Improper lens hygiene habits make users more prone to infectious and irritative conjunctivitis
  • Exposure to infected persons: Facilitates transmission of contagious viral or bacterial conjunctivitis
  • Compromised immunity: Those with weakened immune systems are more susceptible to eye infections
  • Atopic history: Patients with conditions like asthma, eczema, etc. are at higher risk for developing allergic conjunctivitis
  • Environmental factors: Certain geographic regions have higher pollen counts or pollution levels that can irritate eyes
  • Young age: Childhood conjunctivitis is more common due to immunologic factors and transmission potential

Signs and Symptoms

Source: AOA

Conjunctivitis can produce an array of eye symptoms that often provide clues towards etiological classification:

General Symptoms

Regardless of the cause, most cases present with sore, irritated eyes accompanied by varying degrees of:

  • Redness: Engorged blood vessels in covering conjunctiva
  • Itching/burning sensation
  • Excess tearing/discharge: May appear watery, mucousy or purulent
  • Eyelid swelling, pain with blinking
  • Gritty or foreign body sensation in the eye
  • Photophobia: Mild light sensitivity/discomfort

Type-Specific Manifestations

Certain clinical features help differentiate infectious, allergic, and irritative subtypes:

Viral Conjunctivitis

  • Watery discharge
  • Mild grittiness
  • Possible cold symptoms

Bacterial Conjunctivitis

  • Copious, opaque and purulent discharge - Yellow or green
  • Matting of lashes
  • Eyelid crusting

Allergic Conjunctivitis

  • Severe itching and irritation
  • Significantly impacts both eyes

Irritant Conjunctivitis

  • More acute onset following exposure
  • Excessive tearing

Diagnostic Approach

Since management differs based on underlying etiology, determining the exact conjunctivitis trigger is crucial. A systematic diagnostic workup typically involves:

  • History and Physical Exam: The patient’s account of symptom qualities and timing provides early clues to guide the diagnosis. The eye exam assesses for characteristic signs like discharge characteristics, lid involvement, and conjunctival injection. Visual acuity and corneal staining may be conducted to evaluate for other potential etiologies.
  • Microbiology: Culturing eye discharge samples can identify pathogenic organisms. This is especially useful in cases of neonatal or particularly severe conjunctivitis to detect gonorrheal or chlamydial infections which can lead to corneal damage if left untreated.
  • Allergy Testing: Prick skin testing and serum IgE levels help confirm hypersensitivity reactions in those with predominantly allergic manifestations. This allows identification of the specific allergenic triggers.

In severe or refractory cases, additional advanced tests like Schirmer testing, cytology, immunoassays, and biopsy may also be considered to fully elucidate the underlying etiology.

Treatment Overview

Conjunctivitis therapy mainly centers on three aspects– addressing the underlying cause, managing bothersome symptoms, and preventing transmission in infectious cases:

  1. Etiological Treatment: Bacterial infections are directly treated with antibiotic drops/ointments. Cool compresses, oral antihistamines, and mast cell stabilizers manage allergic reactions. Identifying and eliminating irritants resolves those cases.
  2. Symptomatic Relief: Lubricating drops, cold compresses, oral analgesics, and anti-inflammatories help to alleviate discomfort.
  3. Transmission Precautions: Frequent handwashing, avoiding eye rubbing, contact lens handling precautions, and social isolation during contagious periods helps prevent person-to-person spread.

Most viral conjunctivitis cases are self-limited and clear within 7-14 days without intervention. Mild irritation or allergy cases also generally resolve after allergen avoidance and simple self-care measures. However prompt medical attention is warranted if any visual changes, intense pain, or sensitivity to light occur as this may indicate a more significant underlying disorder.

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While conjunctivitis itself poses minimal long-term consequences, a lack of early diagnosis or improper management can result in adverse sequelae like:

  • Recurrent conjunctival scarring
  • Chronic papillary hypertrophy
  • Corneal injury
  • Vision impairment

Rapid institution of appropriate therapy is thus crucial. Additionally, prompt intervention is especially vital in neonatal cases which can permanently damage the developing eye.

Preventative Strategies

Various evidence-based prevention approaches can curb the incidence of conjunctivitis by disrupting transmission pathways and minimizing exposures:

  • Personal Hygiene: Simple measures like handwashing before touching eyes, daily towel/pillowcase replacement, and not sharing cosmetics significantly reduce the spread of pathogens.
  • Appropriate Contact Lens Hygiene: Includes lens case cleaning and scheduled replacement as well as avoidance of exposure to contaminated water sources.
  • Allergen Avoidance: Controlling home and workplace dust, dander, and irritants through cleaning, air filters, etc. lessens ocular allergic responses.
  • Public Health Measures: Improved sanitation infrastructure, disease outbreak vigilance, community education, and access facilitation to medical care represent helpful population-based interventions.
  • Chemoprophylaxis: Antibiotic ointment application after birth protects infants from high-risk infections that can scar vision.

📓 Related Articles

For further discussions related to vision, please refer to these articles:

Wrap Up

Conjunctivitis is an extremely prevalent condition and a common reason for seeking medical care. Understanding the varied causes, presentations, and complications enables accurate diagnosis and optimal management.

Combining appropriate treatment with sound preventative strategies offers the best opportunity to reduce individual risk and societal burden exerted by this common affliction. While largely benign, conjunctivitis can lead to marked discomfort and potential vision disturbances warranting timely medical assessment, especially when indications of more serious pathology arise. Increased general awareness and additional research remain valuable avenues for combating this ubiquitous problem.

FAQs on Conjunctivitis

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Can I wear contact lenses with Conjunctivitis?

No. It's best to avoid wearing contact lenses until the infection clears up.

Is Conjunctivitis contagious?

Viral and bacterial conjunctivitis are contagious, but the allergic type is not. Contagious forms can spread through direct or indirect contact.

Can Conjunctivitis cause permanent vision damage?

It rarely leads to permanent vision damage. Prompt treatment usually prevents complications.

How do I clean my eyes if I have Conjunctivitis?

Clean your eyes gently using a damp, clean cloth, wiping from the inside corner outward. Avoid reusing the cloth to prevent reinfection.