What is dry eye?
Dry eye is a condition which commonly effects people of all ages. It is more appropriate to refer to the condition as a ‘tear film abnormality’ rather than dry eye as often people with ‘dry’ eyes will complain of their eyes being very watery.
The tears have several important functions.
- They keep the front surface of the eye (the cornea) moist and comfortable. This helps to keep the vision clear. If it starts to dry out the vision will start to blur.
- They flush out debris and waste products from the eye, and help clear away dust and small foreign bodies that often get into the eye.
- They provide nutrients to the eye to keep it healthy, and carry substances which help to prevent or fight infection.
The tear film is made up of three microscopic layers: a mucous layer, closest to the surface of the eye, a watery (aqueous) layer, and an oily (lipid) layer on the front surface of the tear film. The different components of the tears are produced by a variety of glands located in the conjuctiva and eyelids.
These layers are in a fine balance. The balance often be disturbed by lack of production of one or more of these three main constituents. The tear film will then either not be produced in sufficient quantity or will evaporate from the eyes too quickly.
Normally the tear film is spread over the eye with each blink. Most people tend to blink about once every 12 seconds. If the tear film evaporates too quickly or is not produced in sufficient quantities, the eye often dry out between blinks.
What are the symptoms of dry eye?
People with dry eye will usually complain of one or more of the following symptoms:
- sore or stinging eyes
- sandy, gritty or scratchy eyes
- foreign body sensation
- burning or irritated eyes
- sensation of dryness
- persistently watery eyes
- blurred vision
- red eyes
- decreased tolerance to contact lenses
Why do some people get watery eyes when their eyes are dry?
If the tear film has a lot of watery (aqueous) tears but lacks a good layer of oil, the watery tears evaporate or run off the eye quickly, the cornea becomes exposed and irritated, resulting in the textbook, gritty eye feeling. The irritation triggers more watery tears which are there to flush away grit and debris, but they don’t lubricate the eye, so they don’t stop the irritation. The key is to improve the quantity and quality of the tear film’s oil.
What causes dry eye symptoms?
There are many different causes of dry eye symptoms. The following are some of the most common.
Dry or windy weather, heaters and air conditioning often alters the evaporation of tears from the surface of the eye. Cigarette smoke often exacerbates the irritation if the tear film is unstable.
When concentrating we tend not to blink as often, so using a computer, watching television, driving or reading often causes irritation if the tear film is unstable.
Contact lens wear
Wearing contact lenses often results in changes in tear film stability and evaporation. Symptoms of dry eye are one of the major reasons for people deciding to stop wearing contact lenses.
As we age there is a normal reduction in tear production. At 65 years of age the tear glands produce about 40 per cent of the lubricating tears they produced at 18 years of age.
During pregnancy and after menopause, hormonal changes often results in changes in tear film stability and tear production.
The contraceptive pill often affects the hormone balance mentioned above.
Certain prescription drugs including anti-histamines, diuretics and anti-anxiety pills often alter tear stability. Some anti-allergy and common cold or influenza medications can also cause symptoms of dryness.
Blepharitis and meibomian gland dysfunction
Blepharitis is a condition affecting the eyelids. In blepharitis, the meibomian glands that produce the oily layer of the tears often become blocked, and the oils produced tends to be of poor quality, resulting in tears that break down very quickly, exposing the cornea and causing gritty, irritated eyes. Bacteria associated with the blepharitis also sometimes produce substances that disturb the tear film.
Arthritis and related conditions
Arthritis is often be associated with dryness of mucous membranes and tear film instability. Sjogren’s syndrome is a condition characterised by rheumatoid arthritis, dry eyes and a dry mouth.
Excessive tear drainage
The tears normally drain from the eye through a channel to the nose. If this drainage is too fast the tears usually don’t remain on the eye for long enough, resulting in dry eye symptoms.
How is dry eye diagnosed?
We conduct tests which investigate tear production and tear evaporation, and often instill dyes into the eye which allow detection of areas of dryness or irritation.
How is dry eye treated?
The way in which dry eye is treated depends on the type and severity of the condition.
Mild dry eye is best managed by using ocular lubricants or ‘tear supplements’. Tear supplements are not drugs and do not ‘cure’ dry eye, but they do provide symptomatic relief by effectively replacing the tears, moisturising and lubricating the eye.
There are many different tear supplements available. Most come in the form of drops. Some drops are thicker and stay on the eye longer than others that are more watery. Sometimes a gel or ointment is preferred in moderate or severe cases. After examining you, we’ll recommend the tear supplement that is best for you.
If dry eye is associated with blepharitis, treatment of the underlying condition often provide relief.
If the dry eye is associated with reduced tear production or excessive tear drainage, an option is to block the lower punctum to reduce the drainage and keep the tears in the eye for longer. This often be achieved with temporary or permanent plugs.
For very severe dry eye, a scleral lens which is filled with a lubricant and domes over the cornea is fitted to the eye. Our 3D scanner allows us to customize the lens to your eye, making it thinner, lighter and healthier – all to maximize your comfort.
What else can be done to reduce dry eye symptoms?
- Avoiding environments that aggravate the condition often reduce dry eye symptoms.
- Wearing wrap-around sunglasses or side-shields on your spectacles often protect the eye from the drying wind.
- Ultrasonic cold water humidifiers in the home or workplace often improve comfort.
- Taking frequent breaks when working on the computer or concentrating on blinking more frequently often be beneficial.
- Periodic cold compresses or bathing the eyes with saline often also assist.