The conjunctiva is a transparent, thin membrane that covers the inner surface of the eyelid. It also covers the white part of the eye (sclera). Inflamed conjunctiva leads to conjunctivitis which causes the sclera to acquire a red look. The conjunctiva can also suffer damage from infection, chemical irritation and injury. Other causes are allergic reactions, cancers and dry eyes.
When people become older, the conjunctiva becomes loose. It also develops folds. Some conjunctival diseases can cause corneal scarring. Corneal scarring can lead to loss of sight.
Three parts make up the conjunctiva:
- Bulbar conjunctiva (ocular conjunctiva) – It covers the anterior area of the white sclera. The bulbar conjunctiva is located at the intersection of the cornea and sclera.
- Palpebral conjunctiva (tarsal conjunctiva) – It covers the inner surface of the lower and upper eyelids. The palpebral conjunctiva lines the back of the eyelid before crossing the space between the forniceal conjunctiva (globe). It then folds back on itself as it spreads across the sclera to the cornea. The structure of the conjunctiva makes it impossible for contact lenses to stick behind the eye
- Conjunctival fornices – It forms the intersection between the bulbar and palpebral conjunctiva. Its protective covering is flexible and loose
The conjunctiva comprises an epithelium which contains blood vessels, lymphatic channels, fibrous tissue, plasma cells and so on. The epithelium is three to five cell layers thick.
The following are the functions of the conjunctiva:
- To protect the eye from microorganism infections. It may also protect against foreign bodies like dust and debris
- To help maintain the tear film and prevent the dry eye syndrome
- To help with the smooth opening and closing of the eyelids through lubrication
- To provide nutrients to the eyelids and eye through blood vessels
- It lines the inside of the eyelid and provides cover for the sclera
Associated symptoms & disorders
Conditions associated with conjunctiva may include:
- Inflammatory disorders such as episcleritis, scleritis and conjunctivitis (pink eye). Episcleritis and scleritis are immune-related diseases. Scleritis can destroy vision and the eye. Conjunctivitis is classified as acute or chronic. It can be infectious or allergic.
- Chemosis occurs with a prolapsed conjunctiva due to excess edema in bulbar conjunctivitis. Edema of tarsal conjunctiva causes the emergence of papillae (tiny, fine projections).
- Hyperplasia of lymphoid follicles occurs in viral conjunctivitis giving rise to small swellings. This happens in the tarsal conjunctiva
- Conjunctival pallor, an unhealthy appearance to the palpebral conjunctiva, is indicative of anemia.
- When blood vessels dilate in the conjunctiva, injected conjunctiva arises. Injected conjunctiva causes red eyes.
- Gonococcal is an infection of the conjunctiva. It is passed on to newborns during birth. Failure to treat it can lead to ulcers on the cornea. The eyeball can get perforated and lead to blindness.
- A conjunctival cyst (a transparent sac) results from inflammation. It is also a result of an infection of the eye.
- Chlamydia trachomatis causes a prolonged infection of the conjunctiva. The infection results in trachoma. Trachoma can lead to blindness if not treated.
- Conjunctival hemorrhage refers to bleeding from the small blood vessels.
- When inflammation keeps recurring on the conjunctiva, it gives rise to vernal keratoconjunctivitis. The disease can damage the surface of the cornea.
- Conjunctival lymphoma is a painless tumor located on the front surface of the eye.
- Keratoconjunctivitis sicca refers to persistent dryness in both eyes. Dryness leads to dehydration in the cornea and conjunctiva.
- Conjunctival hemangioma is a benign tumor. There is also the conjunctival nevus, another benign growth in the bulbar conjunctiva
- Conjunctival melanoma is a growth in the bulbar conjunctiva. It is cancerous and lethal because the cancerous cells can enter the eyeball. They can then spread through the bloodstream to the liver, brain, bones and lungs.
- A pinguecula is a harmless, raised yellowish-white growth next to the cornea while a pterygium is a harmful fleshy growth of the conjunctiva into the cornea. A pterygium distorts the cornea’s shape. It can cause astigmatism and other conditions.
Diagnosis of associated disorders
Diagnosis will depend on the problem afflicting the conjunctiva. Generally, the following examinations will take place:
- History of the ailment affecting the conjunctiva, for example, injury.
- An ophthalmic examination which may include vision acuity tests, foreign body examination and so on.
- In case of a tumor on the nasal bulbar conjunctiva, a culture of the lesion or a biopsy may be undertaken.
- The eye care professional may examine a bulbar conjunctiva using a slit lamp. He/she observes the inferior and superior parts of the bulbar conjunctiva. The professional will do so when the patient’s eyelid is held open as he/she looks up or down. For palpebral conjunctiva and fornices, a small cotton swab is used to invert the lid.
- The professional will use a slit lamp to check for a damaged epithelium. He/she will apply a small amount of fluorescein dye to the ocular surface.
Treatment of associated disorders
Treatment for conjunctiva and related diseases is aimed towards reducing or eliminating inflammation. It is also focused on healing infections, lesions, edema and so on.
Antibiotic eye drops and ointments are prescribed for bacterial conjunctivitis. A single ceftriaxone injection together with a single dose of azithromycin are used to treat gonococcal conjunctivitis. Silver nitrate eye drops are routinely dropped into newborns to prevent gonococcal conjunctivitis.
Corticosteroids and cold compresses may help with viral conjunctivitis. Artificial eye drops will provide relief to eyes affected by conjunctival hemorrhage.
Surgery is needed to remove tumors like in the case of conjunctival melanoma. The eye can be removed to save the body from cancerous effects. Also, plaque brachytherapy, a type of radiotherapy, is used to treat conjunctival melanoma. Chemotherapy (drugs) is also used for benign and malignant tumors.
There is also surgical excision of benign tumors such as those found in conjunctival nevus and conjunctival cyst. Surgery to remove redundant conjunctiva is necessary too. In conjunctivochalasis, the eye doctor grasps the conjunctiva using forceps. He/she also uses thermocautery to cause contraction of the redundant tissue.