What is dry eye?
The tear film that covers the surface of the eye is produced by glands in the eyelids and around the eye. Tears keep the surface of the eyes wet, which keeps the eyes clean and protects them against infection. If your eyes don’t produce enough tears, or if your tears dry up (evaporate) too quickly or your tears aren’t of the right quality, this will lead to dry eyes.
Dry eye is usually more common as people get older. As we age, our eyelids aren’t as good at spreading tears each time we blink. The various glands in our eyes that produce tears may also become less effective. Essentially, the quality of something known as your tear film gets worse.
Structure of the eye and eye surface
The eye is shaped like a ball, and has a tough white outer layer called the sclera. The surface of the sclera is covered by a thin translucent layer called the conjunctiva. The sclera has a clear section at the front of the eye called the cornea, which is protected by the tear film. Several glands containing cells that produce different substances, in the eyelids and within and under the conjunctiva, help produce the tear film, including the lacrimal glands and meibomian glands.
You cannot cure dry eye but there are some treatments that can help your eyes feel more comfortable. However, dry eye doesn’t usually cause any damage to your eye and typically doesn’t lead to permanent changes to your vision. There are many things that you can try to help you manage it better:
Finding the right eye drops to suit you and trying different things to help cope with the symptoms of dry eye can take some time and commitment but we will get there together.
Each time we blink, our eyelids create a new layer of tears over the front of the eye.
Tears have three main components:
- Mucous inner layer Produced by mucous cells in the conjunctiva. This is healthy in most people.
- Watery (aqueous) middle layer This is produced by lacrimal glands, also known as tear glands, through openings in the upper eyelid. As we get older, particularly in women after menopause, the lacrimal gland produces less watery tears.
- Oily outer layer Produced by the meibomian oil glands in the eyelids, which have openings just behind the eyelashes on both the upper and lower eyelids. Problems with these glands are the most common cause of dry eye syndrome. This smooth layer of tears acts like a waterproof barrier. It stops the watery tears from evaporating.
When you blink, you leave a thin layer, called the tear film, over the front of your eye. The tear film keeps the front of your eye healthy and it also helps the eye focus properly, giving you clear vision. The tear film is made up of three layers: the mucin (mucous) layer, the aqueous (watery) layer, and the lipid (oily) layer. Each one of these layers is needed to keep your tear film healthy.
A smooth layer of tears is essential for sharp vision. If the tear film has patchy areas where it has dried out, the light that hits the eye is scattered and does not focus clearly. A patchy, poor quality tear film also leads to discomfort and irritation.
Signs and Symptoms
Dry eye syndrome, also known as dry eye disease can make your eyes feel dry, scratchy and irritated or watery, and feel heavy and tired at the end of the day. It can also cause excessive watering of the eyes (when they are very dry a reflex reaction in the brain causes more tear production).
Usually, dry eyes does not cause long-term problems with your sight, but can cause fluctuating blurriness. Dry eye is more common, and is exacerbated by time spent in front of computer screens and in air-conditioned environments. One in every three people over the age of 65 experience problems with dry eyes.
Dry eye syndrome can affect anyone at any age, it is more common in women, especially after the menopause or during pregnancy when changes in hormonal levels happen and as we get older.
As we get older we also generally produce less tears, and the eyelids also become less effective at spreading the tears each time we blink.
People who frequently use computer or video screens are also more at risk of developing dry eyes. Using screens for a long period of time can lead to reduced blinking, meaning the tears are not spread across the eye surface as well.
Lack of sleep and excessive stress can lead to dry eye due to oily tear gland dysfunction.
The use of some medicines, including anti-depressants, anti-histamines and oral contraceptives, can also affect the amount of tears produced.
Dry eye syndrome is also more common in people with autoimmune diseases like Sjögren’s syndrome, rheumatoid arthritis and lupus.
Other risk factors for dry eye include long-term contact lens wear, laser or cosmetic surgery, long-term use of glaucoma eye drops and large blebs from glaucoma surgery.
Blepharitis and meibomian gland dysfunction (MGD) are both very common causes of dry eye that can affect your tear film and contribute to dry eye. To learn more about blepharitis and how to treat it click here.
Dry eye syndrome is a chronic, long-term condition and you may need to try several different treatments before you find the right one for you. Treating and managing your dry eye syndrome early can prevent permanent damage to the surface of the eye and therefore stop future vision loss.
Keeping the eye surface and tear film healthy is also important for successful management of glaucoma, especially as many of the eye drops necessary for glaucoma treatment can themselves cause dry eye symptoms.
Dry eye syndrome and glaucoma
Dry eye syndrome and glaucoma commonly appear together because the eye drops used to treat glaucoma can cause dry eye symptoms. Studies suggest that 50–60 per cent of people who are being treated for glaucoma also have dry eye syndrome. Glaucoma is treated as a priority as it can cause vision loss, but dry eye symptoms can also cause constant irritation, and so managing both conditions effectively can be very challenging. Switching to preservative-free glaucoma drops may help those who have dry eye and glaucoma.
Maintaining good oily tear production by gentle daily hot eyelid compresses, addressing lifestyle factors and using artificial tear supplements are the best ways to manage dry eye associated with glaucoma. Both conditions are long-term but manageable – remember we are here to help.
Lack of watery tears
Rapid tear evaporation due to lack of oily tears
Step 1: Evaluate which type of dry eye is present; both types can be present at the same time.
Step 2: Identify and treat or remove any underlying causes. You may be asked to stop certain medications, use a different type of glaucoma eye drop, use a different type of contact lens or reduce the number of hours you wear contact lenses.
Step 3: Treat each type of dry eye in turn.
There are several different options for the treatment of your dry eye syndrome, depending on the type and severity of your condition.
Tear replacement :
Most of the time, dry eye just causes discomfort and can be well controlled with the use of artificial teardrops during the day and possibly gels and ointments last thing at night as they are thicker and last longer.
As the drops are used to relieve the symptoms and are not a cure for the condition, you will probably always need to use them.
Once you have dry eye, you tend to be always prone to it, but you will probably find that there are times when it is better than others.
If you have blepharitis or MGD, practising lid hygiene can really help make your eyes feel more comfortable and reduce the frequency of artificial tear drops required. Please click here for more information on blepharitis and how to clean your eyelids.
Switching to preservative-free glaucoma eye drops is recommended for patients with glaucoma who also have dry eye syndrome.
Reduction of inflammation
Steroid eye drops or topical ciclosporin eye drops may be prescribed if the dry eye condition has led to inflammation of the surface of the eye.
Prevention of tear drainage
When there is lack of watery (aqueous) tears, punctal plugs can be inserted into the tear duct (puncta) to stop tears from draining away and keep them on the surface of the eye for longer. If the plugs help your dry eye but fall out, then punctal cautery can be considered. This is a simple procedure where the opening of the tear drainage tube is permanently sealed.
It is important to treat this condition. Without treatment complications such as scarring of your cornea (the transparent layer oat the front of the eye) and conjunctivitis (inflammation, or infection of your eye) can occur and your eye sight could be permanently affected.