This article describes the conjunctiva anatomy as well as diseases and conditions that can adversely affect the white of the eye and inner eyelid.
Conjunctiva Anatomy
The conjunctiva is made up of cells and tissues that serve specific functions. These include goblet cells that secrete mucus and a layer of cells called the stratified squamous epithelium that provide structural stability.
The conjunctiva itself is divided into three segments:
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 allow the eyelid and eyeball to move freely.
These segments form a continuous “closed” structure that prevents objects, like contact lenses, from slipping behind the eyeball.
Function of the Conjunctiva
The primary function of the conjunctiva is to lubricate the eye by producing mucus and tears. Together, these fluids form a layer, called the tear film, which consists of the innermost mucus layer, the middle watery layer, and the outer oily layer.
The tear film serves several important functions:
Barrier protection: The tear film creates a barrier against harmful microorganisms like bacteria or viruses. It also protects the cornea from grit and things that can cause scratches. Lubrication: The tear film allows the eyelid to open and shut smoothly without irritation. The outermost oily layer also prevents the evaporation of fluids, ensuring consistent levels of moisture between blinks. Visual acuity: Together, the layers of fluids create a smooth optical surface that you need for good, non-distorted vision. Eye health: The tear film contains substances that promote wound healing, suppress inflammation, neutralize free radicals, and create a hostile environment for bacteria and other disease-causing organisms.
While the lacrimal glands are tasked with producing the watery portion of tears, the conjunctiva can also produce these fluids, albeit in smaller quantities.
Associated Conditions
Several conditions can affect the normal functioning of the conjunctiva. Because the surface of the eye is exposed, it is susceptible to many problems including infection, trauma, allergic reactions, and dryness.
Here are some of the most common conjunctival disorders.
Conjunctivitis
Conjunctivitis, also known as pink eye, is inflammation or infection of the conjunctiva. Some bacterial or viral forms of conjunctivitis are highly contagious. Other forms may be triggered by an allergy or exposure to harsh chemicals.
Symptoms of conjunctivitis include:
Pink or red discoloration of one or both eyesA gritty sensation in the eyeA crusty eye dischargeItchy or burning eyes Excessive tearingSwollen eyelidsBlurred visionIncreased sensitivity to light
Injected Conjunctiva
Injected conjunctiva is a term used to describe bloodshot eyes. The eyes appear red because of the dilation (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 rednessEye pain or burningEye itchinessSwollen eyesEye tearing
Conjunctival Hemorrhage
A subconjunctival hemorrhage is bleeding of the eye caused by the rupture of a blood vessel under the conjunctiva. This can lead to a tiny speck of redness on the white of your eye.
If the rupture is larger, the bleeding can spread beneath the conjunctiva, creating a large irregular patch of bright red blood. In rare cases, the bleeding can make the entire white of the eye turn red.
There are many things that can cause a subconjunctival hemorrhage, including:
Straining while coughing, sneezing, vomiting, or using the toiletAn eye injuryEye infectionsRubbing the eye too hardWearing contact lenses. Taking Coumadin (warfarin) or other blood thinners
A subconjunctival hemorrhage is usually harmless and will resolve on its own without treatment within a couple of weeks.
Conjunctival Lymphoma
Conjunctival lymphoma is a rare type of eye cancer that usually appears as a painless, pink patch on the eye. The tumor is typically painless and usually hidden behind the eyelids. This disease is often discovered during a routine eye exam.
Symptoms of conjunctival lymphoma include:
Blurred visionSeeing spots or floatersA fleshy bump on the eyeEye rednessDry eyesEye irritationLight sensitivityYellowish eye discolorationA swollen eyelid
Conjunctival Hemangioma
A conjunctival hemangioma is a congenital condition that causes blood vessels to clump on the white part of the eye. It can sometimes cause 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 bumpEye irritation, particularly when blinkingSpontaneous eye bleeding if vessels are ruptured
A conjunctival hemangioma is usually harmful but should be examined regularly for any changes or signs of progression. It can be surgically removed for cosmetic reasons or if it causes eye irritation.
Conjunctivochalasis
Conjunctivochalasis is a common, aging-related disorder of the conjunctiva. It is characterized by the presence of folds in the conjunctiva that typically develops between the eyeball and eyelids.
The folds, usually found along the lower lid margin, interfere with the normal distribution of tears. This can lead to dry eye disease.
Symptoms of conjunctivochalasis include:
A gritty sensation in the eyeDry, burning eyesEye rednessStringy mucus in or around your eyesLight sensitivityDifficulty driving at nightDifficulty wearing contact lenses
Chemosis
Chemosis is the irritation of the conjunctiva that can cause it to swell and become inflamed. In some cases, the swelling can look like a blister as it bulges around the edges of the cornea.
Symptoms of chemosis include:
Eye rednessSwelling of the conjunctivaItchy eyesBlurred visionDifficulty focusingEye tearing
Most cases are caused by allergies, eye infections, or simply rubbing the eye too aggressively. Other possible causes include eye infections, eye surgery, and hyperthyroidism (overactive thyroid gland).
Unlike conjunctivitis, chemosis is not contagious.
