Dry Eye

What is "Dry Eye"?

“Dry Eye” occurs when the eye does not produce tears properly, or when the tears are not of the correct consistency and evaporate too quickly. It is a common term we use to describe disease of the tears and eye surface that results in symptoms of discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface.

It is a poor name, as one of the more common symptoms of ‘dry eye’ is watery eyes! It has more accurate names depending on the subtype, such as “dry eye syndrome’, 'ocular surface disease', 'keratitis sicca’, or ‘keratoconjunctivitis sicca', 'dysfunctional tear syndrome', 'lacrimal keratoconjunctivitis', 'evaporative tear deficiency' and 'aqueous tear deficiency.'

What are the Symptoms?

  • Watering eyes, from occasional to all the time. This may be for no apparent reason, or it happens during particular activities, such as when you are using the computer, or in particular environments such as in air-conditioning or in the wind.

  • Eyes appearing red, or feeling tired, sore or heavy.

  • Being unable to wear contact lenses because they are just not comfortable, or they do not provide consistenly clear vision.

  • A feeling that there is ‘something in your eyes’  or that they sting or burn.

  • Eye pain, blurry vision and/or an inability to complete or continue tasks for as long as you would like, such as reading, watching TV or driving.

  • Discomfort, blurring or fatigue when using computers or mobile devices.

How Common is Dry Eye?

Very common. It affects 5-40%  of the general population, depending on the definition and population studied. It is more common in women and especially post-menopausal women.

It is more common in office workers, so the environment and tasks performed influence the condition.

It is rather common in contact lens wearers due to the way the lenses disrupt and influence the tearfilm.

Why are the Tears Important?

The tear film is more complex that you would think, and it serves a number of purposes.

  • It is the first optical surface of the eye, so a smooth tear layer is vital for good vision.

  • The tears capture and wash away foreign material from the surface of the eye.

  • The tears lubricate the eye surface and the lids, to allow the lids to slide up and down comfortably.

  • The type of cells on the surface of the eye must be kept moist with tears of the correct osmolarity (salt concentration) to stay alive.

  • The tears have lots of immune proteins and white blood cells to protect against infection.

  • The tears carry nutrients to the surface of the eye, and take away wastes, as the cornea does not have any blood vessels inside it.

Why are the Tears Important?

The tears have three main components which form blended layers:

  • The layer closest to the eye is the mucous layer. This layer is excreted by cells on the surface of the eye, and it has two main functions – it allows the water in the tears to stick to the surface, and it traps foreign material and fatty substances to allow them to be moved off the eye.

  • The middle layer makes up the bulk of the tears. This is referred to as the aqueous or watery layer. This layer is produced by the large lacrimal gland above the eye, along with lots of small glands in the surface cells of the conjunctiva. This layer contains the salts, proteins, nutrients, etc that are important to the surface of the eye. We produce about 1 gram of tears a day, which is only 20 drops from, say, an eye drop bottle.

  • The final layer is the outer oil or lipid layer. This is a single-molecule thick layer of lipid that coats the aqueous layer. This layer is produced by the 25 or so large Meibomian glands in each eyelid. This layer has several functions. It reduces evaporation of the tears, like a pool cover. It provides a barrier to the tears from rolling over the lid margin, and it helps to smooth out the tear film for good optics.

What Causes Dry Eye?

Wow, where do we start? There are many, many causes of Dry Eye Syndrome. Broadly speaking, either the tears escape too quickly, or the tear components are undersupplied or are in the wrong ratio.

There are two main categories: Evaporative Dry Eye and Aqueous Insufficiency Dry Eye.

Evaporative Dry Eye

  • 80% of ‘dry eye’ is evaporative. This is usually caused by poor oil supply on the tear film, so tears evaporate on the surface of the eye much quicker than they should. It can be made worse by a slow blink rate, as the tears need to be refreshed by blinking every 12 -15 seconds. By far the biggest cause of evaporative dry eye is poorly functioning or blocked Meibomian glands.

  • When the tears dry out, a number of negative things happen to the surface of the eye. Cells start dying, the mucous layer performs a poor job of making a hydrophilic layer, and the osmolarity (salinity) of the tears rises.

  • When the tears become salty, water is pulled out of the surface of the eye, which kills or irritates the surface cells, which can set up inflammation, causing further irritation. In addition, it stimulates extra tears to be produced quickly and in excess to try and protect the ocular surface. These ‘reflex’ tears are in excessive quantity and are of poor quality, being made up mainly made up of water.  Reflex tears do not do a good job of coating and protecting the eyes.

Aqueous Deficiency Dry Eye

  • For the other 20% of ‘dry eye’, it’s because of a lack of aqueous (water) in the tears. This can be due to changes with age, or conditions such as Sjroegren’s Syndrome (dry mucosa such as mouth and eyes), autoimmune disease, or it can be related to medications for high blood pressure and diabetes for example.

  • Of course, it is common for more than one cause to exist at one time.

  • Dry eye syndrome is also affected by hormones, so people who suffer from thyroid disease, women who are pregnant and peri- and post-menopausal women can suffer from episodes of dry eye which can significantly affect the comfort of their eyes.

  • Other factors that can contribute to dry eyes are alcohol, dehydration, systemic disease such as diabetes and arthritis, and nutritional deficiencies such as omega-3 and vitamin A, incomplete blinking. Environmental factors such as wind and air-conditioning, contact lens wear, and past laser refractive surgery and cataract surgery are other causes.

  • Computer users, distance drivers and other people who do a visually demanding task for long periods tend to suffer from dry eye as they subconsciously reduce their blinking rate, allowing the tear film to break up and cause dry patches to appear.

How is Dry Eye Treated?

Treatment plans for Dry Eye Syndrome are tailored to the individual patient. A thorough eye and general health history taking needs to be performed and a thorough examination of the eyes, tear film and eye lids will allow for diagnosis and grading of the condition.

Our services include using the Oculus Keratograph to examine and grade the Meibomian glands, tear film quantity and stability, and to track ocular surface redness. We use TearLab osmolarity testing to help grade severity of dry eye, to predict inflammation, and to track the success of treatments.

  • The most common treatments are to improve the functioning of the oil-producing Meibomian glands. Meibomian glands respond well to in-office and at home manual gland expression, including Blephasteam treatments.

  • It is important to treat anterior blepharitis if it is present. This may require Blephex treatment or prescribed antibiotics or anti-inflammatories, and always involves lid hygiene

  • Anti-inflammatory eye drops may be important in acute dry eye, to break the inflammation before long term treatments soothe the eyes.

  • We can work with your GP to help modify your systemic medication to reduce dryness if appropriate.

  • We can recommend a combination of tear supplementing drops, gels and ointments for the individual case.

 

See also our Services page

An appropriate 'work up' assessment of your eyes can determine what is best for you. We look forward to helping you with your Dry Eyes.

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