Conjunctiva Anatomy and Function
The clear, protective tissue that covers the white of the eyes
Medically reviewed by Bryan M. Wolynski, OD
The conjunctiva is a thin layer of clear tissue that lines the inside of the eyelid and covers the white of the eye (sclera). This mucous membrane makes fluids to keep the eye moist, produce tears, and protect it from foreign bodies and infections.
This article covers the anatomy of the conjunctiva as well as diseases and conditions that can affect the white of the eye and inner eyelid.
Conjunctiva Anatomy
The conjunctiva is made up of cells and tissues that have specific jobs. For example, goblet cells secrete mucus and a layer of cells called the stratified squamous epithelium provides structural stability to the eye.
What is the Difference Between Sclera and Conjunctiva?
The sclera is the white part of the eye. The conjunctiva is the protective layer (membrane) that covers the sclera.
The conjunctiva has three parts:
The bulbar conjunctiva is the segment that covers the sclera but not the cornea (the clear dome in front of the eye).
The palpebral conjunctiva is the segment that covers the inner surface of the upper and lower eyelids.
The fornix conjunctiva is a flexible segment between the bulbar and palpebral conjunctivas that lets the eyelid and eyeball move freely.
The parts form a continuous closed structure that keeps objects, like contact lenses, from slipping behind the eyeball.
Function of the Conjunctiva
The main function of the conjunctiva is to keep the eye moist. It provides lubrication to the eyes by making mucus and tears. These fluids form a covering (tear film) that has three layers: innermost mucus layer, the middle watery layer, and the outer oily layer.
The tear film has a few important jobs:
Barrier protection: The tear film is a barrier against harmful microorganisms like bacteria or viruses. It also protects the cornea from grit and other debris that can cause scratches.
Lubrication: The tear film lets the eyelid open and shut smoothly without irritation. The outermost oily layer prevents the evaporation of fluids, which helps maintain consistent levels of moisture between blinks.
Visual acuity: All the layers create a smooth optical surface that is needed for healthy, non-distorted vision.
Eye health: The tear film has substances in it that promote wound healing, suppress inflammation, neutralize free radicals, and create a hostile environment for bacteria and other disease-causing organisms.
The lacrimal glands make the watery portion of tears, but the conjunctiva is also capable of producing tears, just in smaller quantities.
Associated Conditions
Several conditions can negatively affect the conjunctiva. The surface of the eye is exposed, so it is susceptible to problems like infection, trauma, allergic reactions, and dryness.
Here are some of the most common conjunctival disorders.
Conjunctivitis
Conjunctivitis is also known as pink eye, an inflammation or infection of the conjunctiva. Bacterial or viral forms of conjunctivitis are highly contagious. Other forms are triggered by an allergy or exposure to harsh chemicals.
Symptoms of conjunctivitis include:
Pink or red discoloration of one or both eyes
A gritty sensation in the eye
Crusty discharge from the eye
Itchy or burning eyes
Excessive tearing
Swollen eyelids
Blurred vision
Increased sensitivity to light
Verywell / Emily Roberts
Related: Symptoms of Pink Eye (Conjunctivitis)
Injected Conjunctiva
Injected conjunctiva is a term used to describe bloodshot eyes. The eyes look red because of the widening of blood vessels in the conjunctiva.
Bloodshot eyes can be caused by dry air, sun exposure, dust, foreign body, allergies, infection, or trauma.
Symptoms of injected conjunctiva include:
Eye redness
Eye pain or burning
Eye itchiness
Swollen eyes
Eye tearing
Conjunctival Hemorrhage
A subconjunctival hemorrhage is bleeding of the eye that’s caused when a blood vessel bursts under the conjunctiva. The bleeding can look like a tiny speck of redness on the white of your eye.
If the opening is big, the bleeding can spread beneath the conjunctiva and create a large irregular patch of bright red blood. In rare cases, the bleeding can turn the entire white of the eye red.
A subconjunctival hemorrhage can be caused by:
Straining while coughing, sneezing, vomiting, or using the toilet
An eye injury
Eye infections
Rubbing the eye too hard
Wearing contact lenses
Taking Coumadin (warfarin) or other blood thinners
A subconjunctival hemorrhage is usually harmless and will get better on its own without treatment within a couple of weeks.
However, if you get these bleeds often, you should see a healthcare provider. Getting frequent or recurrent subconjunctical hemorrhages can be a sign of an underlying condition like a blood clotting disorder, hypertension, or other systemic disease.
Conjunctival Nevus
A conjunctival nevus is a visible spot on the conjunctiva. It is sometimes called an eye freckle. It’s not usually cancerous, but if you have one, your eye health provider will want to monitor it over time to make sure it does not get bigger. An increase in size of a conjunctival nevus can be a sign of melanoma.
Conjunctival Hyphemia
Conjunctival hyperemia is when there is a build-up of excess blood in the eye. It’s visible through the thin, clear film that covers it. There are many possible causes of the condition and most of them are not serious. Allergies, infections, and dry eye are a few common causes, as are certain medications used to treat eye problems.
Related: Why Do I Have Blood in My Eye?
Conjunctival Lymphoma
Conjunctival lymphoma is a rare type of eye cancer that usually looks like a painless, pink patch on the eye. The tumor is often hidden behind the eyelids and only found on a routine eye exam.
Symptoms of conjunctival lymphoma include:
Blurred vision
Seeing spots or floaters
Eye redness
Dry eyes
Eye irritation
Light sensitivity
Yellowish eye discoloration
A swollen eyelid
Conjunctival Hemangioma
A conjunctival hemangioma is a condition you are born with (congenital), though it can be something you get later on (acquired). The condition causes blood vessels to clump on the white part of the eye. Sometimes, the hemangioma causes a visible bump that looks like a tiny blood blister.
Symptoms of a conjunctival hemangioma include:
A clump of blood vessels that form a bright red bump
Eye irritation, particularly when blinking
Spontaneous eye bleeding if vessels are ruptured
A conjunctival hemangioma is usually not harmful but should be checked regularly by a provider for any changes or signs that it’s getting worse. It can be surgically removed for cosmetic reasons or if it causes eye irritation.
Conjunctivochalasis
Conjunctivochalasis is a common, age-related disorder of the conjunctiva. It looks like folds in the conjunctiva that develop between the eyeball and eyelid.
The folds are usually found along the lower lid margin and interfere with the normal distribution of tears. That’s why the condition can lead to dry eye disease.
Symptoms of conjunctivochalasis include:
A gritty sensation in the eye
Dry, burning eyes
Eye redness
Stringy mucus in or around your eyes
Light sensitivity
Difficulty driving at night
Difficulty wearing contact lenses
Chemosis
Chemosis is irritation of the conjunctiva that causes swelling and inflammation. In some cases, the swelling can look like a blister as it bulges around the edges of the cornea.
Symptoms of chemosis include:
Eye redness
Swelling of the conjunctiva
Itchy eyes
Blurred vision
Difficulty focusing
Eye tearing
Allergies, eye infections, or simply rubbing the eye too aggressively are common causes. Other causes include eye infections, eye surgery, and hyperthyroidism (overactive thyroid gland). Unlike conjunctivitis, chemosis is not contagious.
When to See a Provider
Talk to your healthcare provider if you notice changes to how your eyes look or feel, or if you have any problems with your vision. They might want you to see a provider who specializes in eye health to have your eyes checked and diagnose and treat any problems.
Having regular eye exams is also important to your health, not just your vision. You should have your eyes checked yearly even if you do not wear glasses or contacts.
Summary
The conjunctiva is a thin layer of clear tissue that lines the inside of the eyelid and covers the white of the eye. It keeps your eyes moist, helps make tears, and protects your eyes from infections and injuries. That said, injuries and infections can affect the conjunctiva and cause symptoms like pain and redness.
If you notice any changes to your eyes or vision, talk to your provider. It’s also important to keep up with regular eye health checkups.
Read the original article on Verywell Health.
