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The conjunctiva – the transparent protective layer of the eye
We only feel the conjunctiva of our eyes when it is irritated or inflamed. This layer of transparent tissue performs important tasks for the eye. Here is an overview of the structure and function of the conjunctiva.
What is the conjunctiva?
The conjunctiva is a very flexible layer of tissue and is one of the mucous membranes of the human body. In simple terms, the conjunctiva forms the connection between the eyeball and the eyelids. With each blink, it wipes the surface of the eye and distributes tear fluid on the cornea.
How is the conjunctiva structured?
The structure of the human eye is very complex, and the conjunctiva is part of this sophisticated sensory organ. It covers the white sclera of the eye to the edge of the cornea but is also found on the inside of the upper and lower eyelids. Therefore, from a medical aspect, it is divided into two parts, namely the conjunctiva bulbi, which covers the front part of the eyeball, and the conjunctiva tarsi on the inner sides of the eyelids.
The tissue is very flexible, otherwise blinking would not be possible. The conjunctiva of the eye contains goblet cells and accessory lacrimal glands. Apart from the actual lacrimal glands of the human eye, these accessory glands are also involved in the production of tear fluid. On the pale sclera, the fine blood vessels of the conjunctiva are easily visible to the naked eye. If the conjunctiva is irritated, then the eye appears red.
At the transition between the eye socket and the upper or lower eyelid, the conjunctiva forms a small, slit-like cavity called the conjunctival sac. This is bounded by small folds at the transition of the conjunctiva between the eyeball and the eyelid. If the eyes are inflamed or dry, eye drops and eye ointments are applied into the conjunctival sac.
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What is the function of the conjunctiva?
As inconspicuous as the conjunctiva may be, it performs some extremely important tasks for the eye:
- It primarily serves as a protection against pathogens and external stimuli. Because the eye and eyelid are connected, no foreign bodies can enter the eye.
- However, the conjunctiva also contributes considerably to the formation of the tear film.
- If the lacrimal glands are inactive, the conjunctiva can take over the wetting of the eyes to a certain extent via the accessory glands. This is because the goblet cells are involved in the formation of the mucous mucin layer. It ensures the stability and adhesion of the tear film, as the aqueous component would otherwise flow out of the eye.
- Furthermore, the conjunctiva enables the frictionless movements of the eye in all directions and the opening and closing of the eyelids.
What is conjunctivitis?
Inflammation of the conjunctiva, known as conjunctivitis, is one of the most common diseases of the conjunctiva and can affect anyone. Its cause can be a viral, bacterial or fungal infection, but also simply an irritation caused by wind, smoke or an allergy. It is therefore divided into
- infectious conjunctivitis
- non-infectious conjunctivitis
Inflammation can be clearly recognised by the redness of the otherwise white sclera. Other symptoms include:
- itching
- burning
- watery eyes
- sticky eyelids
- foreign body sensation
- increased sensitivity to light
- possible swelling of the eye
Caution: Infectious conjunctivitis is very contagious! To avoid transmitting the pathogens, increased attention should be paid to hygiene and contact with other people avoided.
What other diseases of the conjunctiva are there?
Heavy strain on the eye can sometimes cause bleeding under the conjunctiva. For example, the strong pressure of coughing can damage the fine blood vessels. But also vascular diseases or high blood pressure are often triggers of these unsightly haemorrhages of the conjunctiva of the eye. In most cases they are harmless but should nevertheless be examined by a doctor.
In general, redness or other discoloration may indicate a disease of the eye. An eye specialist can identify the causes during the examination and prescribe treatment with appropriate medication.