Eye Health

Updated 20 May 2015

Causes of eye disease

The eye is a complex organ and there are many diseases or problems by which it can be affected.


The outcome can range from temporary discomfort to total vision loss, which is why all eye problems and diseases should be taken seriously.

If any change in vision is experienced, it warrants immediate medical attention. Many eye diseases have no early symptoms, so by the time a person notices vision changes, a problem may already be advanced. That is why two-yearly regular eye check-ups are absolutely essential, (every year or more frequently if you have an eye problem) according to the Merck Manuals.

Read: Glaucoma

The main causes of eye problems can be divided into five main groups:

•    Inflammation of the eye and surrounding eye structures caused by bacterial, viral, parasitic or fungal infections
•    Injuries to the eye and surrounding eye structures either as a result of trauma or an object in the eye
•    Genetically inherited eye diseases, many of which many of which may only manifest later in life (although some children are born with these conditions). Many of these affect the structures and the functioning of the eye and therefore can impair visual abilities.
•    Diseases or conditions, such as diabetes or migraine, which can affect other organ systems of the body, such as the eyes
•    External causes, such as allergies, and eye strain, owing to over-use, or as a side effect of medication.

Inflammation of the eye

Inflammation of the eye or eyes can be the result of viral, bacterial or fungal infections, sometimes following trauma to the eye, or an allergic reaction. Inflammation of the eye is usually either categorised by the site of the inflammation ( i.e. the conjunctiva) or by its cause.

Eye infections can occur in different parts of the eye and are characterized by redness, itching, swelling, discharge, pain and problems with vision, according to the National Institutes of Health.

Many of these symptoms are also characteristic of eye allergies.

The most common eye infections include:

•    Conjunctivitis
•    inflammation of the eyelash follicles (also known as blepharitis)
•    an external eyelid stye
•    uveitis (a swelling of the middle layer of the eye)
•    scleritis (a severe inflammation of outer protective layer of the eye)
•    iritis (inflammation of coloured tissue around the pupil of the eye)
•    optic neuritis (when the optic nerve becomes inflamed and causes vision loss)
•    a corneal ulcer (most frequently caused by herpes simplex keratitis, fungal keratitis, dry eye, or an eye injury), according to
•    keratitis (an infection of the clear layer of the cornea caused by a virus such as herpes simplex)
•    Sarcoidosis (an inflammatory disease in which clumps of immune cells form in various organs, including the eyes)

Read more on common eye infections and when to see an optometrist 

Injuries to the eye and objects in the eye

Eye injuries can be the result of direct trauma, or the penetration of an object into the eye. These can cause corneal scratches, or far more serious injuries.

Substances, such as acids, oven cleaners and chalk dust can cause serious damage if they get into your eyes. Others, such as shampoo, can cause burning and stinging and short-term discomfort, but will not cause serious long-term injury. A black eye can be the result of being struck in the eye or in the area around the eye, causing bruising around the eye socket.

Trauma to the eye can cause retinal detachment, which is a serious condition that needs immediate medical treatment.

Fractures or cracks in the facial bones surrounding the eye also warrant immediate treatment. These are called fractures of the orbit and according to the Merck Manuals, require immediate medical attention.

Genetically inherited diseases

These can manifest in children, or in adults. These conditions can all cause vision problems, or changes to the appearance of the eye. Here is a list of the most common eye problems that are genetically inherited:

•    Acute glaucoma ()
•    Vision problems like nearsightedness, farsightedness, astigmatism and presbyopia and eye floaters ()
•    Macular degeneration
•    Cataracts
•    Strabismus (squint)
•    Lazy eye (The brain does not receive images from the lazy eye correctly)
•    Retinitis pigmentosa a group of genetic conditions, all of which cause mottled pigmentation of the retina)

Read: Conjunctivitis

Other conditions that affect the eyes

Many other conditions can affect eyesight, such as:

•    Diabetes can cause diabetic retinopathy
•    High blood pressure can cause hypertensive retinopathy
•    Migraine
•    Hyperthyroidism and Graves’ disease can cause bulging eyes
•    Multiple sclerosis can cause a paralysis or weakness of the eye muscles
•    Sarcoidosis causes clumps of immune cells to form in organs such as the eye
•    Myasthenia gravis is a neuro-muscular disorder, which can cause drooping of the eyelid and double vision.

External causes of eye disease

These include allergies, eyestrain, owing to over-use, or as a side effect of medication. Dry eyes are typically caused by environmental factors, and can also be a side effect of certain medications, such as tranquillisers, diuretics, certain blood pressure medications, oral contraceptives and antihistamines, according to the Merck Manuals.

The side effects of many other medications could affect your eye health. Discuss any problems with your doctor, and remember to give your ophthalmologist a full list of the medicines you are taking when you go for your regular eye check-up.

Read More:

What is eye disease?

Symptoms of eye disease

Diagnosing eye disease

Image: Colour eye from Shutterstock


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Megan Goodman qualified as an optometrist from the University of Johannesburg. She has recently completed a Masters degree in Clinical Epidemiology at Stellenbosch University. She has a keen interest in ocular pathology and evidence based medicine as well as contact lenses.

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