Conjunctiva

The conjunctiva is a thin mucous membrane that covers the inner eyelid and protects the front surface of the eyeball. It plays an important role in protecting the eye from external influences and in regulating moisture.

What is the function of the conjunctiva?

The conjunctiva forms a protective barrier against external irritants and infections.

It regulates the moisture of the eye by producing and distributing tear fluid. Additionally, it functions as a sensor for pain and other stimuli, underscoring its importance for the eye.

• Protective Function: The conjunctiva forms a protective barrier that shields the eye from external foreign bodies such as dust, dirt, and microorganisms. By creating a physical barrier, it prevents these substances from entering the eye.
• Moisture Regulation: By producing and distributing tear fluid, the conjunctiva helps keep the surface of the eye moist. This supports the health and function of the eye by lubricating the surface and providing necessary moisture.
• Sensory Perception: The conjunctiva contains sensory nerve endings that can detect pain and other stimuli. These sensory abilities allow it to respond to potentially harmful or irritating influences and protect the body accordingly.
• Immune Defence: The conjunctiva contains various immune system cells that can fight infections and regulate inflammatory responses. These immune cells play a crucial role in defending against pathogens and maintaining eye health.
• Support of the Tear Film: The conjunctiva not only produces tear fluid but also helps to stabilise the tear film. An intact tear film is essential for maintaining clear vision by smoothing the eye surface and evenly distributing the tear film over the entire eye when blinking.

How is the conjunctiva structured?

The conjunctiva is divided into four different sections:

1. Conjunctiva Tarsi (Tarsal Conjunctiva): This section of the conjunctiva covers the inside of the eyelids, primarily the underlying cartilaginous structures known as tarsi. The conjunctiva tarsi is characterised by numerous small openings, which are the excretory ducts of the Meibomian glands that produce lipids (fats) that stabilise the tear film.
2. Conjunctiva Fornicis (Fornix Conjunctiva): This region of the conjunctiva is located in the folds between the eyelids and the eyeball. It forms the transition zone between the conjunctiva tarsi and the conjunctiva bulbi and includes the area where the eyelid glides along the eyeball.
3. Conjunctival Sac: The conjunctival sac, a cavity between the conjunctiva and the eyeball, plays a crucial role in moisture regulation and lubrication of the eye. It primarily facilitates the distribution of tear fluid and provides space for the movement of the eyeball within the eye socket.
4. Conjunctiva Bulbi (Bulbar Conjunctiva): The conjunctiva bulbi is the largest section of the conjunctiva and covers the front surface of the eyeball. It extends from the limbus, the transition zone between the cornea and conjunctiva, to the inner eyelid. This region of the conjunctiva plays an important role in protecting the eye from external influences and supports the moisture regulation of the eye by producing and distributing tear fluid.

Histological Structure

Histologically, the conjunctiva consists of several layers under the microscope:

• Stratified Epithelium Tissue: The outermost layer of the conjunctiva consists of multiple layers of cells. These cells protect the eye and help produce and distribute the tear film that keeps the eye moist and protected from damage.
• Connective Tissue Layer (Lamina Propria): Below the stratified epithelium tissue is a layer of connective tissue. This layer serves as a supporting structure for the conjunctiva and helps maintain its shape and integrity.

In the epithelial layer of the conjunctiva, there are also special cells known as goblet cells. These produce mucus for the tear film that lubricates and protects the eye.

The conjunctiva is also rich in nerves. These nerves mainly originate from branches of the trigeminal nerve, a very important nerve in the face. This allows the conjunctiva to perceive sensations such as touch, irritation, and pain, and respond accordingly.

What injuries and diseases affect the conjunctiva?

Various injuries and eye diseases can affect the conjunctiva. One of the most common diseases of the conjunctiva is conjunctivitis.

Conjunctivitis (Pink Eye)

An inflammation of the conjunctiva can be caused by infections (viral, bacterial, or allergic) or irritants such as smoke and chemicals. Conjunctivitis symptoms include redness, itchy eyes, burning, increased light sensitivity, increased tear flow, and sometimes purulent discharge.

Wondering how to treat conjunctivitis? The treatment depends on the cause of the conjunctivitis.

Viral conjunctivitis usually resolves within 1-3 weeks on its own and only requires moisturising drops. Bacterial conjunctivitis is often treated with antibiotic eye drops or ointments. In allergic conjunctivitis, antihistamines or mast cell stabilisers may be prescribed.

The prognosis depends on the cause of the conjunctivitis. Most cases heal without long-term consequences, but untreated bacterial conjunctivitis can lead to complications such as corneal ulcers.

Pterygium (Surfer's Eye)

Pterygium is a benign growth of connective tissue on the cornea that is often caused by excessive UV radiation. It can cause irritation, a foreign body sensation in the eye, and, in advanced cases, even visual disturbances.

Small pterygia often requires no treatment, but in progressive or symptomatic cases, surgical removal may be necessary. After surgery, corticosteroid drops may be used to reduce inflammation.

The prognosis after surgery is generally good, but there is a risk of pterygium regrowth.

Pinguecula

A yellowish benign growth on the conjunctiva, often caused by increased UV radiation. It is usually harmless but can cause irritation, especially if it becomes inflamed.

Pinguecula typically require no treatment unless they cause bothersome symptoms. In such cases, corticosteroid eye drops or artificial tears may be used to relieve discomfort. The prognosis is generally good, and pingueculae rarely cause serious problems.

Chemical Burns

Contact with caustic chemicals can cause severe damage to the conjunctiva, leading to intense eye pain, redness, and in severe cases, loss of vision.

Immediate flushing of the eye with plenty of water is crucial to dilute the chemical and minimise damage. Afterwards, medical treatment with eye drops or ointments may be necessary to relieve pain and inflammation. The prognosis depends on the severity of the burn. In severe cases, permanent damage, including vision loss, may occur.

Subconjunctival Haemorrhage

Bleeding under the conjunctiva, often caused by trauma, excessive coughing or sneezing, or high blood pressure. They manifest as red spots on the white of the eye and are usually harmless but can be alarming.

Subconjunctival haemorrhages typically require no specific treatment and resolve spontaneously within one to two weeks. The prognosis is generally good, and the haemorrhage usually clears without complications.

It is important to have any injury or disease of the conjunctiva examined by an ophthalmologist to receive appropriate treatment and avoid potential complications.

How are conjunctival diseases diagnosed?

The diagnosis of conjunctival diseases is typically made through a comprehensive examination by an ophthalmologist. Initially, a thorough medical history is taken, asking about symptoms, past diseases, and potential excessive UV exposure.

Next, the surface of the eye is visually inspected for redness, swelling, or other abnormalities.

A slit-lamp examination allows for a detailed view of the conjunctiva under high-resolution light to detect even the smallest changes. If an infection is suspected, samples may be taken for further testing. Additionally, allergy tests may be conducted if an allergic reaction is suspected.

Based on the examination results, the ophthalmologist can recommend appropriate treatment, ranging from topical medications to surgical interventions, depending on the diagnosis.