What are Eye Infections?
 

Eye infections are when microorganisms—such as bacteria, viruses, or fungi—invade any part of the eyeball or surrounding tissues and cause damage. Because the eye is a delicate organ with direct proximity to the brain and optic nerve, evaluating the precise location and depth of an infection is critical for preserving vision. Non-infectious inflammatory conditions can also mimic symptoms of eye infections, and an evaluation is still warranted because these conditions can also lead to serious complications. 

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Common Types of Eye Infections
 

Conjunctivitis
 

       Viral Conjunctivitis
 

• Symptoms: watery or thin discharge, prominent redness, gritty feeling, itching. May begin in one eye and spread to the other within a couple of days.

• Key Features: highly contagious; frequently accompanies a common cold, sore throat, or upper respiratory infection. Enlarged, tender lymph nodes in front of the ear (preauricular lymphadenopathy) are common.

       Bacterial Conjunctivitis
 

• Symptoms: thick, yellow or green purulent discharge that causes the eyelids to stick shut upon waking, redness, swelling, and irritation.

• Key Features: contagious

       Non-infectious Conjunctivitis
 

• Symptoms: itching, bilateral redness, clear watery discharge, and swelling.

• Key Features: not contagious; usually associated with seasonal allergies, pet dander, environmental irritants, or dry eyes. 

Infectious Keratitis (Corneal Infection)

      Bacterial or Fungal Keratitis
 

• Symptoms: severe eye pain, marked redness, extreme photophobia (sensitivity to light), blurred vision, feeling like a foreign object is stuck in the eye, and a visible white or cloudy spot on the cornea.

• Key Features: strong association with contact lens use (especially sleeping in lenses or poor hygiene), corneal trauma, or contaminated water exposure.

      Herpetic Keratitis (Herpes Simplex Virus / HSV)
 

• Symptoms: eye pain, redness, tearing, light sensitivity, and recurrent blurred vision.

• Key Features: Caused by the herpes simplex virus reactivation. Often presents unilaterally with classic "dendritic" (branching tree-like) corneal ulcers seen on specialized staining.
   

Hordeolum (Stye)
 

• Symptoms: localized, painful, red bump or pimple near the eyelid.

• An acute bacterial infection of an eyelash follicle (external) or meibomian oil gland (internal). 

Anterior Blepharitis
 

• Symptoms: flaking & crusting by eyelashes, redness, itchiness, inflammation

• May also have noninfectious causes.

Preseptal Cellulitis
 

• Symptoms: swelling around the eye, redness, warmth

Postseptal / Orbital Cellulitis
 

• Symptoms: pain with eye movement, eye bulging, vision changes, swelling around the eyes, redness, warmth

• This is an emergency

Infectious Retinitis 
 

• Symptoms: vision changes, floaters, light sensitivity, and sometimes pain

• May also have noninfectious causes

Dacryocystitis

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• Infection of the lacrimal sac, usually resulting from obstruction of the nasolacrimal duct, which normally drains tears into the nose. It may cause pain, swelling, redness, excessive tearing, and purulent discharge near the inner corner of the eye.

Endophthalmitis
 

• A severe intraocular infection, particularly following eye surgery, intravitreal injections, or penetrating trauma. Symptoms can include worsening vision, pain, redness, and sometimes hypopyon. An ophthalmic emergency.

Herpes Zoster Ophthalmicus
 

• Symptoms: Painful, blistering rash affecting one side of the forehead, scalp, eyelid, or tip of nose. Eye redness, tearing, photophobia, and blurred vision may also occur.

• Key Features: Caused by reactivation of the varicella-zoster virus involving the ophthalmic branch of the trigeminal nerve. The infection can involve the cornea and other internal eye structures, potentially threatening vision.

Major Risk Factors
 

• Contact Lens Misuse: Sleeping in contact lenses not approved for overnight wear, wearing lenses longer than recommended, using tap water to clean or store lenses, swimming or showering while wearing lenses, or failing to properly clean and replace contact lens cases. Even lenses approved for overnight wear carry an increased risk of serious corneal infections, including bacterial keratitis.

• Eye Trauma, Surgery, or Foreign Bodies

• Advanced age

• Dry Eye Disease

• Poor hygiene: rubbing eyes with unwashed hands, sharing makeup, sharing towels.

Treatment & Management
 

Viral conjunctivitis: artificial tears, cold compresses, hygiene

Bacterial conjunctivitis: warm and cold compresses; artificial tears; topical antibiotics when appropriate

Allergic conjunctivitis: allergen avoidance, antihistamine/mast-cell stabilizer drops, cold compresses

Hordeolum: warm compresses; antibiotics only for selected indications

Blepharitis: lid hygiene, warm compresses, targeted treatment when indicated such as with antibiotics or antimite medicine. 

Preseptal cellulitis: oral antibiotics and close follow-up

Infectious keratitis: same-day ophthalmology assessment and organism-directed treatment

Orbital cellulitis: emergency hospital evaluation, imaging when indicated, and IV antibiotics

Dacryocystitis: Systemic antibiotics and warm compresses. Abscess formation may require drainage by an ophthalmologist. Recurrent infections or persistent obstruction may require a procedure called dacryocystorhinostomy, which creates a new pathway for tear drainage.

Endophthalmitis: immediate ophthalmology management, often intravitreal antibiotics

Infectious retinitis: Requires urgent ophthalmology evaluation and organism-specific treatment, which may include systemic or intraocular antimicrobial therapy.

Herpes zoster ophthalmicus: Systemic antiviral medication, ideally initiated within 72 hours of rash onset, although treatment may still be beneficial afterward. Urgent ophthalmology evaluation is indicated when ocular involvement is suspected.

                                                                    General Self-Care & Hygiene
 

• Stop Contact Lens Wear if eye infection suspected. Replace current lenses and storage cases.

• Wash hands thoroughly after touching the face.

• Discard any eye makeup used around the infection, do not share makeup, do not share towels

Non-Infectious Mimics of Eye Infections
 

• Subconjunctival Hemorrhage: A broken blood vessel on the white of the eye causing a bright red patch. It is entirely painless, has no discharge, does not affect vision, and resolves spontaneously.

• Dry Eye Disease: A condition caused by inadequate tear production, excessive tear evaporation, or abnormalities in the tear film. Symptoms include burning, redness, gritty or foreign-body sensations, fluctuating blurry vision, and sometimes excessive reflex tearing. Common contributing factors include aging, certain medications, environmental conditions, reduced blinking, meibomian gland dysfunction, rosacea, and autoimmune disorders such as Sjögren's syndrome.

• Episcleritis: Inflammation of the tissue layer below the conjunctiva, causing localized redness. It is mainly  idiopathic and associated with autoimmune disorders. It may sometimes be associated with infections. It is usually mild and self-limiting. 

• Scleritis: Inflammation of the layer beneath the conjunctiva and episclera, causing localized or diffuse deep red/purple discoloration and intense aching pain. This requires an urgent opthalmology evaluation. It may sometimes be associated with infections. 

• Uveitis: Intraocular inflammation of the middle layer of the eye beneath the sclera. Anterior uveitis usually causes deep, aching eye pain, severe photophobia, and a red ring around the cornea (ciliary flush), whereas posterior uveitis may cause floaters or blurred vision without pain. This requires an urgent opthalmology evaluation. It may sometimes be associated with infections. 

• Acute Angle-Closure Glaucoma: A rapid spike in intraocular pressure causing severe eye/head pain, hazy vision, halos around lights, a hazy cornea, and nausea/vomiting. This is a critical ocular emergency. 

• Ocular Rosacea: Chronic inflammation affecting the eyelids and ocular surface that may occur with or without facial rosacea. Symptoms can include red or bloodshot eyes, burning, stinging, itching, gritty/foreign-body sensation, dryness, tearing, light sensitivity, and recurrent eyelid irritation. Common findings include blepharitis, meibomian gland dysfunction, eyelid-margin redness, and recurrent styes/chalazia. More severe disease can involve the cornea (keratitis) and potentially threaten vision, requiring urgent ophthalmologic evaluation.

• Posterior Blepharitis: redness, irritation, eyelid swelling especially by the inner eyelid edge, affecting the meibomian glands. 

Red Flag Symptoms 
 

Seek immediate evaluation from an optometrist, ophthalmologist, or emergency room if you experience any of the following "red flag" signs:
 

• Severe, deep, or throbbing eye pain.

• Pain with eye movement

• Change in vision (double vision, blurriness, partial loss, or total loss of sight).

• Significant sensitivity to light (photophobia) making it difficult to keep the eye open.

• A visible white, gray, or cloudy spot on the clear cornea.

• The affected pupil is abnormally sized, shaped, or unreactive to light.

• Swelling, redness, and severe pain extending around the eye

• History of recent eye surgery, eye trauma, or high-risk contact lens exposure (such as swimming in lakes/hot tubs with lenses).

• New flashes, floaters, or a dark curtain/shadow across the vision
   

                                                                                References & Guidelines
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• Centers for Disease Control and Prevention (CDC). Clinical Overview of Pink Eye (Conjunctivitis).

• Centers for Disease Control and Prevention (CDC). Healthy Contact Lens Wear and Care.

• American Academy of Ophthalmology (AAO). Clinical guidance on red eye, corneal infection, and ophthalmic emergencies.

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