What Is Conjunctivitis?
Conjunctivitis is inflammation of the conjunctiva, which is the thin translucent tissue that lines the inner surface of the eyelid and the outer surface of the sclera, a tough white outer coating, or wall, of fibrous tissue that covers the entire eyeball except for the cornea.
Conjunctivitis is usually associated with redness of the white part of the eyes, light sensitivity (photophobia), excessive tearing, ocular discomfort (gritty sensation, itching, burning), and/or discharge.
There are many different causes of conjunctivitis. Some types of conjunctivitis are infectious, while others are not. These can generally be differentiated from one another based on history and an examination by an eye doctor.
"Infectious" means that the person with infectious conjunctivitis can transmit it to another person. There are several types of infectious conjunctivitis: viral and bacterial, including gonococcal and chlamydial:
1. Viral Conjunctivitis
Most cases of infectious conjunctivitis are caused by viruses. Often, viral conjunctivitis is associated with, or follows, an upper respiratory infection, sore throat, or cold, and is usually bilateral (affecting both eyes).
The virus most commonly responsible is adenovirus, of which there are 51 subtypes. Three serotypes of adenovirus (8, 19, and 37) can cause a more severe form of conjunctivitis called epidemic keratoconjunctivitis (EKC). A serotype is a group of closely related microorganisms that share a characteristic set of immune responses. Symptoms with EKC tend to be more severe, the course is longer, and there is involvement of the cornea.
Viral conjunctivitis generally resolves on its own without treatment, usually over the course of approximately one week.
Since these viruses are highly contagious, it is important to observe precautions to prevent transmission: avoid touching the eyes and wash the hands frequently. Because tears shed virus particles, people with viral conjunctivitis should not share pillows or towels with others while infected. Those who work with sick people or children should consider staying home from work until the infection has resolved.
The symptoms can be alleviated with artificial tears (chilled for a soothing effect) or cool compresses. Antibiotic drops or ointment are not indicated, as these are anti-bacterial, not anti-viral. Rarely, in cases of conjunctivitis associated with a herpes infection, an antiviral agent may be prescribed in oral and/or eyedrop form.
If there is significant inflammation or corneal involvement, steroids may be prescribed, although these typically do not shorten the course of the disease.
Individuals who have been prescribed steroids require close follow-up, because steroids can cause a variety of serious side effects: increased intraocular (within the eye) pressure; development of cataracts; an increase in the pressure inside the eye; and possibly glaucoma if used long term.
To avoid a rebound of inflammation and symptoms when stopping steroids, the steroid treatment must be tapered off carefully under the guidance of an eye doctor, rather than stopped abruptly.
2. Bacterial Conjunctivitis
Bacterial conjunctivitis can be caused by a variety of bacteria, ranging from those that commonly reside on our skin (Staph aureus) to more aggressive bacteria (Neisseria gonorrhea). Bacterial conjunctivitis is usually bilateral (both eyes), though there can be a delay of several days for onset in the second eye. There is typically a thick, pus-like discharge from the eyes.
Some bacterial conjunctivitis will resolve spontaneously without treatment, though antibiotics can speed recovery and prevent reinfection. To treat bacterial conjunctivitis, the eye doctor will take a swab of the eye discharge to determine what kind of bacteria are causing the infection and tailor the treatment accordingly. Antibiotic drops or ointment are usually prescribed.
Since these bacterial viruses are contagious, it is important to observe precautions to prevent transmission: avoid touching the eyes and wash the hands frequently.
3. Gonococcal Conjunctivitis
Rarely, bacterial conjunctivitis may be caused by aggressive bacteria such as Neisseria gonorrhea (gonococcal conjunctivitis). This is the same bacteria associated with sexually transmitted diseases. Persons diagnosed with this condition should undergo general sexually transmitted disease (STD) testing, and their partners may also require evaluation.
Gonococcal conjunctivitis can be quite severe, and the bacteria can penetrate the cornea, as well result in corneal ulcers and even perforation and infection within the eye (endophthalmitis).
Gonococcal conjunctivitis requires aggressive treatment, including intramuscular or intravenous antibiotics (usually ceftriaxone) and strong topical antibiotics administered frequently. If there is co-infection with other STDs, those must be treated as well.
4. Chlamydia Trachomatis
Chlamydial infection can also cause conjunctivitis. Chlamydia trachomatis is a bacteria of which there are multiple serotypes. A serotype is a group of closely related microorganisms that share a characteristic set of immune responses. Serotypes D-K cause sexually transmitted diseases as well as conjunctivitis.
Chlamydia trachomatis is often spread in a genital-ocular fashion, or occasionally through eye-to-eye spread. Symptoms usually involve redness, irritation, and watering, and can be chronic, lasting months, sometimes improving and sometimes relapsing. There may also be involvement of the cornea.
Infection of this type is diagnosed by cultures or by Polymerase Chain Reaction (PCR), a test for the Chlamydia genes or DNA. Treatment involves topical drops or ointment and systemic oral antibiotic therapy (often doxycycline or azithromycin). The person and his or her partner also must be referred for STD testing.
The A-C serotypes of Chlamydia can cause a chronic conjunctival inflammation called trachoma. Trachoma, though uncommon in the United States, is the leading cause of preventable blindness in the world.
This condition is associated with inflammation and scarring of the conjunctiva and cornea. Inflammation and scarring of the eyelids can alter the eyelid position and the growth of eyelashes to cause trichiasis, a condition in which the eyelashes touch the cornea and can cause damage to the corneal surface.
Over time, trachoma can lead to opacification (clouding) of the cornea and vision loss. Trachoma is treated by corneal specialists and active infection involves systemic (often azithromycin, doxycycline, or erythromycin) and topical antibiotics. The long term consequences of this condition to the eyelids are treated with surgery to correct the lid position or trichiasis.
Corneal scarring is repaired by corneal surgery, usually through corneal transplantation (penetrating keratoplasty), in which a human donor cornea is sutured in to replace the opacified, damaged cornea.
Keratoprosthesis may also be performed, whereby the opacified cornea is replaced by an artificial cornea, especially if prior corneal transplants have failed or there is felt to be a possibility for high risk of transplant failure.
Allergic conjunctivitis is inflammation of the conjunctiva caused by allergy-inducing substances such as dust, pollen, and pet dander. These substances activate the immune system and prompt cells (called mast cells) to release inflammatory chemicals, such as histamine. This results in redness, irritation, tearing, light sensitivity, and especially, itching. People with allergic conjunctivitis are likely to have a history of other allergic symptoms including sneezing, itchy nose, and runny nose.
Allergic conjunctivitis can be treated by avoiding known triggers, and by topical drops that either stabilize the mast cells responsible for the inflammation (lodoxamide, cromoglycate, and others), act as antihistamines (levocabastine, emadastine, and others), or both (olopatadine, ketotifen, and others).
In severe cases, steroids may be required. Cyclosporin, an anti-inflammatory drop, may also be used. Oral antihistamine and anti-allergy medications may also be helpful. Artificial tears can help remove allergen particles from the ocular surface and sooth the eye.
There are two additional types of allergic conjunctivitis that are less common than typical allergic conjunctivitis: atopic keratoconjunctivitis and vernal conjunctivitis:
1. Atopic keratoconjunctivitis
Atopic keratoconjunctivitis is seen in people with a history of atopy (eczema, asthma, and allergies), in which there is allergic inflammation of the conjunctiva and cornea. It is a bilateral (both eyes) disorder that can lead to significant inflammation and scarring of the eyelids, conjunctiva, and corneas. It tends to have a chronic improving and relapsing course and can cause sufficient scarring to cause vision loss.
Treatment for atopic keratoconjunctivitis is similar to that of allergic conjunctivitis, but more aggressive anti-inflammatories or immunosuppressants may be required to block the immune response responsible for this condition. Significant end-stage corneal scarring from atopic keratoconjunctivitis may require corneal transplantation.
2. Vernal conjunctivitis
Vernal conjunctivitis is a bilateral (both eyes) recurrent allergic disorder most commonly seen in children, especially males. It tends to resolve by adulthood, although some persons then develop atopic keratoconjunctivitis. Persons with this type of conjunctivitis also have a history of atopy (eczema, asthma, and allergies). Symptoms often peak seasonally, most often during the spring and summer, though there may be mild symptoms throughout the year.
The conjunctiva are red, swollen, and irritated. There may be a ring or scattered white, gelatinous inflammatory deposits in the limbal area (the area where the conjunctiva meets the cornea). The cornea may have erosions, ulcers, and abnormal blood vessel growth.
Treatment involves topical drops such as those described above for allergic conjunctivitis. Steroid drops are frequently required to quiet a flareup of the condition. Occasionally, systemic anti-inflammatory agents are necessary for severe disease, and surgery may also be required for corneal plaques (a collection of tissue on the cornea) or non-healing corneal ulcers.
Other Less Common Types of Conjunctivitis
Conjunctivitis may also be caused by local irritation from contact lenses or topical drops, or by a variety of less common ocular conditions that can be diagnosed through ophthalmologic examination.