What is it?
‘Dry eye’ is an umbrella term for a range of conditions where the tear film fails to keep the front surface of the eye moist and nourished.
Today we break down dry eye into three separate categories. Each has a completely different underlying cause. Understanding this is the key to developing a treatment strategy.
Evaporative tear dysfunction (ETD)
This is by far the commonest cause of dry eyes. It results from meibomian gland dysfunction, a type of blepharitis. There is adequate tear production but the tears evaporate quickly. Successful treatments target the oil glands in the eyelid. These include short courses of medium strength steroid eye drops and a three month courses of doxycycline tablets. Most patients also benefit from warm compresses and omega-3 supplements. Meibomian Gland Expression can also be very helpful.
Secretive tear dysfunction (STD)
Some patients do not make enough of the watery component of the tears. This is much less common and is often associated with conditions that affect other parts of the body, such as rheumatoid arthritis and Sjogrens syndrome. Patients with STD are usually treated with tear supplements and low dose steroid eye drops. Some patients need to use serum eye drops, made from their own, or donated blood.
Distributive tear dysfunction (DTD)
This is the rarest type of ‘dry eye’. In these patients the eyelids fail to spread an adequate layer of tears evenly across the eye. Poor lid function after a stroke or Bell’s Palsy are two examples of DTS. Eyelid surgery is often required.
How is it diagnosed?
The diagnosis of dry eye is made by assessing a patient’s symptoms, looking for characteristic changes on the surface of the eye and performing a few simple tests.
The symptoms of dry eye vary depending on the severity.
Mild dry eye symptoms include:
Severe dry eye symptoms include:
- Fluctuating vision
- Sensitivity to light
- Reduced vision
Patients with dry eyes usually have obvious changes in the way they blink, the eyelids, the tears and on the surface of the eye. These are assessed with the slit lamp microscope. The examination is aided by adding a small amount of an orange dye called fluorescein to the tears and then viewing with a blue light.
Common changes in dry eye include:
- A low volume tear ‘prism’ along the lower eyelid margin.
- Tiny ‘pot-holes’ called punctate epithelial erosions on the surface of the cornea, seen as bright blue dots.
- Thinning of the oily layer of the tear film which appears as expanding dark areas. The time these areas take to develop is known as the Tear Break Up Time. The break up time is reduced in patients with dry eye.
This is a simple test used to determine tear production. Small strips of a special paper are hooked over the lower eyelid. After 5 minutes the strips are examined. In very dry eyes the paper remains completely dry.
Some patients, particularly those with secretive dry eye or aqueous insufficiency, have inflammation in the lacrimal gland and elsewhere in the body. The most common example is patients who have rheumatoid arthritis. Blood tests can detect inflammation and the presence of such diseases. This helps both to confirm the diagnosis and plan treatment of the dry eye and other disease.
Most dry eye can be treated medically.
There are some simple things you can do to help dry eyes.
- Avoid conditions that encourage evaporation of the tears such as air conditioning and hot dry heat from heaters and hairdryers.
- Wrap around sunglasses reduce wind movement across your eyes
Artificial tear supplements
Many people with dry eyes need to top up their natural tear production with artificial tears. You do not need a prescription to buy or use most artificial tears.
As you can see from the table below, there are many different types of artificial tears. Some artificial tears are very watery, others are very thick. Some drops have preservative, others do not. Some cannot be used by contact lens wearers. Everyone’s eyes are different and it may take a while to find the drop that is right for you.
Using artificial tear drops
The table below contains the name, lubricant and preservative of all the artificial tear drops currently available in New Zealand. The table is designed to help patients take control of their dry eye treatment by making therapy logical.
Start with a ‘thin’ drop. If it doesn’t seem to work, try using it more frequently or try another thin drop with a different preservative. Use the drops regularly. Dry eye treatment often fails because treatment is inadequate. If you don’t get relief, use a thicker drop.
If you develop an allergy (redness, itch etc) try a different preservative or a non-preserved drop. Use preservative-free drops if drops are required more than 6 times a day.
Ointments are usually too thick to use during the day. They are best used just before bed to give lasting relief overnight.
|Thin drops:||Aquify Comfort drops||Sodium hyaluronate||Sodium Perborate|
|Blink Tears||Polyethylene glycol / Hyaluronic acid||Ocupure|
|Blink Contacts||Sodium hyaluronate||Ocupure|
|Genteal||Hydroxypropyl methylcellulose||Sodium Perborate|
|Polytears||Hypromellose / Dextran||Polyquad|
|Refresh Optive||Carboxy methylcellulose Sodium / Glycerin / Erythritol / Levocarnitine||Purite|
|Refresh Tears||Carboxy methylcellulose||Purite|
|Systane||Polyethylene glycol / Propylene glycol / Hydroxypropyl Guar||Polyquad|
|Systane Ultra||Polyethylene glycol / Propylene glycol / Hydroxypropyl Guar||Polyquad|
(Currently unavailable in NZ
|Propylene glycol / Hydroxypropyl Guar / mineral oil||Polyquad|
|Tears Naturale II||Hydroxypropyl methylcellulose / Dextran / Glycerin||Polyquad|
|Visine||Hydroxypropyl methylcellulose||Benzalkonium Chloride|
|Thick drops||Blink GelTears||Polyethylene glycol||Ocupure|
|Refresh Liquigel||Carboxy methylcellulose||Purite|
|Vistil Forte||Polyvinyl alcohol||OXYD|
|Preservative free drops||Bion Tears||Hydroxypropyl methylcellulose||None|
|Blink Tears preservative free||Polyethylene glycol||None|
|Genteal single use||Hydroxypropyl methylcellulose||None|
|Polytears free||Hypromellose / Dextran||None|
|Refresh||Polyvinyl alcohol / povidone||None|
|Refresh Celluvisc||Carboxy methylcellulose||None|
|Refresh Plus Tears||Carboxy methylcellulose||None|
|Systane preservative free||Polyethylene glycol / Propylene glycol / Hydroxypropyl Guar||None|
|Systane Ultra preservative free|
(Currently unavailable in NZ)
|Polyethylene glycol / Propylene glycol / Hydroxypropyl Guar||None|
|Thera Tears non preserved||Carboxy methylcellulose (hypotonic)||None|
|Tears Naturale Free||Hydroxypropyl methylcellulose / Dextran / Glycerin||None|
|Ointment||Genteal Gel||Hydroxypropyl methylcellulose / Carbopol||Sodium Perborate|
|Polyvisc||Paraffin / Wool fat||None|
|Refresh Lacrilube||White petrolatum / Mineral oil||Chlorobutanol|
Many patients with reduced tear production have inflammation of the surface of their eyes. To test for this, and see if symptoms can be improved, Dr McKellar usually prescribes a short course of low potency topical steroid eyedrops. Patients who find their eyes are more comfortable can then use low dose steroids or other anti-inflammatories such as cyclosporin or diclofenac.
Artificial tears are very helpful in patients with mild and moderate dry eye but they are not the same as natural tears. Sometimes it is necessary to preserve what tears are being made.
This is achieved by reducing or totally blocking the flow of tears from the eye. The easiest way is to occlude the puncta, the tiny openings that form the entrance into the tear drainage system.
There are two ways to reduce outflow:
- Punctal plugs
- Punctal cautery
Tiny cotton-reel shaped silicone plugs can be inserted into the puncta. Originally designed as a temporary solution, punctal plugs can be left in for long periods. The advantages of punctal plugs are:
- They are simple to place
- Occlusion is temporary
- The plugs are easy to remove if the patient develops watery eyes
The puncta can be permanently occluded by the creation of scar tissue with heat.
The advantages of permanant occlusion are:
- Occlusion is permanent
- Scar tissue is more effective than plugs
FAQs and Links
How can my eyes be dry if they still water sometimes and I can still cry?
Dry eye occurs when the average amount of tears is low. Most patients can still produce a few tears when really necessary.