Infections and Inflammation of the Cornea

A number of corneal diseases involve infection and inflammation, including the following. 


Keratitis is a medical term for inflammation of the cornea. Symptoms include rapid onset of pain and redness of the eye, itching, blurred vision, tearing or discharge from the eye, and sensitivity to light.

Keratitis resulting from an infection is among the leading causes of preventable blindness worldwide. The disease occurs far more frequently in developing countries, with the total number of cases globally estimated at 500,000 a year. The number of cases in the United States range between 25,000 and 30,000 annually. 

What Causes Keratitis?

The most common cause of keratitis is injury or infection, but keratitis may also be noninfectious and develop from a wide range of other conditions.

Corneal infections rarely occur in the normal eye. Viral, fungal, parasitic, and bacterial infections are more common after a minor injury or insult to the surface of the cornea.  They are a result of an alteration in the cornea’s defense mechanisms that allows bacteria or other microorganisms to invade when an epithelial defect (such as a scratch of the cornea) is present. These organisms may come from the tear film or as a result of foreign bodies, contact lenses, or irrigating solutions. The process of corneal destruction can take place rapidly (within 24 hours in the case of virulent organisms), requiring quick recognition and initiation of treatment to prevent vision loss.

Corneal infections are caused by a wide variety of microorganisms, including bacteria, viruses, fungi, and protozoa. Bacteria are the most frequent cause of infectious keratitis. The most common groups of bacteria responsible for bacterial keratitis are streptococcus, pseudomonas, enterobacteriaceae (including klebsiella, enterobacter, serratia, and proteus), and staphylococcusspecies.

Other contributing factors that may impact the severity of the case include the degree of trauma, the presence of underlying ocular surface disease, the use of topical steroids or contact lenses, host immune response, and the time it took to diagnosis and begin treatment 

What Are the Risk Factors for Keratitis?

The most common risk factors for keratitis include:

  • Contact lenses: Wearing contact lenses increases your risk of both infectious and noninfectious keratitis. This is in part from not disinfecting lenses properly, wearing contact lenses while swimming, wearing them longer than recommended, or using water or homemade solutions to store and clean lenses. Keratitis is much more common in people who use extended-wear contacts, or wear contacts continuously, than in those who use daily wear contacts and take them out at night.
  • Impaired or reduce immunity: If your immune system is weakened either from local or systemic disease (i.e., cancer, diabetes, or autoimmune diseases such as lupus or rheumatoid arthritis) or through use of medications (anticancer medications or oral steroids) your risk of developing keratitis is higher.
  • Use of topical corticosteroids: The use of corticosteroid eye drops to treat other ocular disease increases your risk of developing keratitis or worsening an existing case.
  • Neurotrophic keratitis: This corneal degenerative disease is characterized by a reduction or absence of corneal sensitivity. The most common ocular conditions associated with neurotrophic keratitis are herpes zoster keratitis and simplex, topical anesthetic abuse, chemical and physical burns to the eye, contact lens over-wear/abuse, topical drug toxicity, irradiation to the eye, and previous corneal surgery.
  • Eye injury/ocular trauma: If one of your corneas is injured severely or has been damaged from an injury in the past, you may be more vulnerable to developing keratitis. If you live in a warm, humid climate or are involved in agricultural work, your risk of keratitis is increased, particularly if your trauma involved organic plant material. (Plant material can scratch the corneal epithelium and chemicals from the plant can cause inflammation, which may lead to an infection.)

What is the Treatment for Infectious Keratitis from Bacteria? 

Prompt initiation of antimicrobial therapy is the most appropriate treatment. Current guidelines from both the American Academy of Ophthalmology (AAO) and World Health Organization (WHO) recommend broad spectrum topical antimicrobials for initial treatment of suspected bacterial corneal ulcers.  Antibacterial eye drops are usually effective against most forms of bacterial keratitis. More severe infections may require non-commercially available fortified topical antibiotic formulations. Generally, oral antibiotics are unnecessary in bacterial keratitis. In some cases, your cornea specialist may need further tests at a cellular level to diagnose the nature of the infection.

What Are Other Types of Infectious Keratitis? 

Fungal keratitis (or keratomycosis) refers to an infection of the cornea caused by any of the multiple fungi capable of invading the ocular surface. The most common species responsible for fungal keratitis are Candida, Fusarium, and Aspergillus species. The infection typically develops slowly and can be hard to differentiate from more common bacterial infections. Keratomycosis is relatively uncommon in the Western world and most often originates in tropical or semi-tropical regions where climate, agricultural work, and outdoor lifestyle may be important predisposing factors. While there is no consensus on the ideal regimen, topical antifungal drops and systemic antifungal agents can be used to treat the disease.

Herpes simplex virus (HSV) is the most common cause of viral infectious keratitis. HSV causes a spectrum of ocular diseases with many clinical manifestations. It is the most frequent cause of corneal blindness in the United States and the most common source of infectious blindness in the Western world. The prognosis for HSV keratitis, however, is generally favorable with aggressive treatment. These may be followed by reactivations and possibly multiple episodes of stromal keratitis (infection within the stroma of the cornea) lasting for months or years. Treatment generally involves topical antiviral agents and/or systemic antiviral agents.

Herpes Zoster 

Herpes zoster ophthalmicus (HZO) is a viral disease characterized by a painful unilateral skin rash in and around the eye. It is frequently associated with fever, malaise, headache, and pain in the area of the rash. The vesicles typically crust and heal within two to six weeks. HZO occurs typically in older adults but can present at any age and occur after reactivation of latent varicella-zoster virus (VZV, the chicken pox virus) present in the cerebral ganglia in the brain. Severity of the VZV and the immune status of the host are primary factors leading to the development of HZO. 

What Are the Symptoms of Herpes Zoster Ophthalmicus?

Common conditions seen in patients with HZO include cornea epithelial defects, decreased corneal sensation, and ocular inflammation (iritis). HZO iritis is frequently associated with high intraocular pressure.

What is the Treatment for Herpes Zoster Ophthalmicus?

This condition is usually treated with oral antiviral medications for 7-10 days. Skin vesicles can be treated with antibiotic ointments to prevent bacterial superinfection, while the corneal disease is usually treated with artificial tears and nighttime lubricants (ointments). Topical steroids (such as prednisolone acetate 1 percent) are only used if the eye shows signs of interstitial keratitis and uveitis. For episodes of herpes zoster-related scleritis, retinitis, choroiditis, and optic neuritis, systemic steroids by mouth or intravenous administration should be considered. Increased intraocular pressure commonly found in herpes trabeculitis (inflammation of the trabecular meshwork, which drains fluid from inside the eye), also responds to topical steroids in conjunction with aqueous suppressants (including timolol, brimonidine, dorzolamide, and acetazolamide). Pain should be treated with narcotics, if warranted. Capsaicin cream applied to the rash may decrease pain, as well.

Conjunctivitis (Pinkeye) 

Acute infectious conjunctivitis (“pink eye”) is an inflammation of the conjunctiva (the clear membrane that lines the inside of the eyelid and covers the white part of the eye). It is the most common and contagious ocular infection in the United States and throughout the world. Pink eye is usually caused by the following types of human adenovirus:

  • Viral conjunctivitis, which is the most common cause of infectious conjunctivitis both overall and in the adult population. It is more prevalent in the summer. Viral conjunctivitis is highly contagious for up to two weeks following the onset of symptoms. It can be spread by finger contact such as touching the affected eye and then the other eye, or by allowing other people to use your personal items such as pillows, wash cloths, towels, and make-up items. If you wear contacts, you need to remove and discard them and wear glasses until the infection clears up.
  • Bacterial conjunctivitis, which is the second most common cause and is responsible for the majority (50 percent to 75 percent) of cases in children. It occurs more frequently from December through April.

What Are the Symptoms of Pink Eye?

Patients with pink eye will experience dilation of the conjunctival vessels resulting in redness and swelling of the conjunctiva, usually accompanied by discharge. Other symptoms of pink eye include itchiness, a foreign body sensation, tearing, sensitivity to light, and a thick discharge that crusts over the eyelashes at night, making it difficult to open the eyes in the morning.

How is Conjunctivitis Treated?

Treatment for pink eye depends on whether the infection is viral or bacterial. If it’s viral, the conjunctivitis will usually clear up on its own within a week. Your physician may recommend several treatments to relieve any discomfort to your eyes. These include applying warm or cold compresses several times daily, cleaning your eyelids with a wet cloth, and using artificial tears. If the conjunctivitis is severe, topical steroids may be added. If the conjunctivitis is bacterial, your eye professional will prescribe antibiotic eye drops, ointments, or pills. You may need to use these medications multiple times each day over the course of a week.

Allergic Conjunctivitis

Unlike infectious viral or bacterial conjunctivitis, allergic conjunctivitis is triggered by an allergic reaction to substances like pollen or mold spores present in the environment. It presents as an inflammation of the conjunctiva, the clear membrane that lines the inside of the eyelid and covers the white part of the eye. Allergic conjunctivitis is the most frequent cause of conjunctivitis overall, generally affecting between 15 percent to 40 percent of the population.

What Are the Symptoms of Allergic Conjunctivitis?

The signs and symptoms of allergic conjunctivitis include redness of the eyes; itchy, burning, and watery eyes; and mucus discharge

Are There Different Types of Allergic Conjunctivitis?

Seasonal allergic conjunctivitis, or hay fever, is the most common type of ocular allergy. It is related to pollens that release spores during specific seasons. In the New York City area it most commonly occurs in May and June (grass and tree pollen) and in late August and September (ragweed pollen). If you are affected by hay fever and other seasonal allergies, you may also experience symptoms involving the nose and throat. Perennial allergic conjunctivitis is a year-round allergic condition. These allergic responses are often related to animal dander, dust, or other allergens present in the environment year-round. Symptoms of perennial allergic conjunctivitis are similar to seasonal allergic conjunctivitis, but tend to be milder.

What is the Treatment for Allergic Conjunctivitis?

Treatment for allergic conjunctivitis often involves preventive steps to keep symptoms at bay. These include keeping pollen out of your home by shutting windows, ensuring your environment is dust-free, and using an indoor air purifier. If you suffer from itchy and watery eyes, a cool compress applied several times a day can provide relief. Many treatments are available for seasonal allergic conjunctivitis. They include different classes of eye drops such as artificial tears, antihistamine combinations, mast cell stabilizers, non-steroidal anti-inflammatory agents (NSAIDs), and topical steroids. Rarely, we use short courses of oral steroids.

Stevens-Johnson Syndrome

Stevens-Johnson syndrome is a rare, serious disorder of the skin and mucous membranes. It usually involves an idiosyncratic reaction to a medication or an infection. Patients’ reaction to a medication or an infection is often unpredictable and can begin with flu-like symptoms, followed by a painful red or purplish rash that spreads and blisters. The top layer of the affected skin then dies, sheds, and heals. All ages may be affected, and both sexes are equally susceptible. Stevens-Johnson syndrome has a 5 percent to 15 percent mortality rate. Ocular involvement, which occurs in as many as half of patients, varies from mild conjunctivitis to severe perforating corneal ulcers. Blindness occasionally occurs in patients with severe late-phase corneal complications, such as chronic corneal ulceration, vascularization, and perforation.

How is the Condition Treated?

Stevens-Johnson syndrome is a medical emergency that usually requires hospitalization. The first and most important step in treatment is to discontinue any medications that may be causing the condition. Supportive care you’re likely to receive while hospitalized includes fluid replacement and nutrition. Wound care is also essential. Your health care team may gently remove any dead skin and place petroleum jelly (Vaseline) or a medicated dressing over the affected areas. Early intervention is important in preventing ocular complications from Stevens-Johnson syndrome. Ocular lubrication with artificial tears and ointments (preferably preservative-free) should be applied regularly. All Stevens-Johnson syndrome patients need emergent consultation with an ophthalmologist at the time of diagnosis.