Dry Eye and glaucoma

How to recognise dry eye?

Dry eye is a common eye condition affecting thousands of New Zealanders daily. Like open-angle glaucoma, dry eye syndrome increases with aging. Studies suggest that 40-50% of glaucoma patients have dry eye syndrome, with women more likely to have it. People with glaucoma are at higher risk of dry eye because some glaucoma treatments can worsen the ocular surface and increase the tendency to dry the eye.

In some cases, dry eye can affect your quality of vision and sensitivity to light. The most frequently reported dry eye symptoms are grittiness, burning, or a sensation of sand or grit in the eyes. However, you might be surprised to learn that dry eyes can also cause excessive watering of the eyes (epiphora).

Why does this happen?

The thin layer of tears covering your eye keeps it lubricated, nourished, and ,protected, and it has three main components. Mucins are at the base to help anchor the tear film in place, a watery layer with nutrients is in the middle (aqueous), and oil is on the surface to reduce evaporation. The various glands that produce these components must all function to create
a healthy tear film of adequate quantity and quality. Unfortunately, when this tear film becomes dysfunctional in dry eyes, it causes the eye’s surface to become inflamed, resulting in chronically red, irritated eyes.

• This is either because of a lack of tear quantity (volume) or quality.
• A tear film lacking in quantity is described as ‘aqueous deficient’;
  a truly ‘dry’ dry eye.
• One lacking in quality is described as ‘evaporative’ since it evaporates too rapidly, causing irritation and consequent eye-watering.
• Evaporative dry eye is approximately nine times more common than aqueous deficiency.

Why does tear film become dysfunctional?

Usually, a combination of factors is responsible for developing a dry eye.

• Age and Gender: Dry eye becomes more common with increasing age and is particularly prevalent in post-menopausal women.
• Environment: Air-conditioned, centrally heated, smoky, polluted, or windy settings, as well as computer use, can aggravate dry eye.
• Contact lenses: Contact lenses disrupt the natural tear film, causing excessive tear film evaporation.
• General health: Rheumatoid arthritis, diabetes, thyroid disease, and other immune disorders such as Sjögren’s syndrome are more commonly associated with dry eye
• Oral medications: Some medications for allergy, depression, or acne, for example, can affect the tear film, such as eye surgery, especially laser surgery (e.g., LASIK).
• Eye drops: Glaucoma is associated with a higher incidence of dry eye because of the medications used to treat the condition.

Many eye drops for glaucoma contain preservatives, which after repeated application over a long period, can damage the superficial cells of the ocular surface, making the eye’s surface less wettable and resulting in the development of dry eye signs and symptoms.

What can you do about it?

Improve the environmental conditions: Minimise exposure to air-conditioning and central heating. Enhance the moisture level around the eyes using humidifiers and/or wrap-around style spectacles to create a humidified local environment protecting the eyes from airflow. Breathable foam inserts forming a seal around the eye are another option with wrap-around glasses or sunglasses.

Minimise use of cosmetics: Cosmetics and face creams worn on the face and around the eyes will migrate over the eyelid margins. This can disrupt the tear film, exacerbating dry eye, so try to minimise make-up use.

Optimise your workspace: Adopt a slight downward gaze at the computer screen where possible to minimise the exposed eye area. Lowering your screen prevents excessive drying of the eye surface. Improve your blinking by practicing complete and regular blinking at least once every 5 or 6 seconds. Blinking exercises can be done anywhere at any time, and there are even Phone Apps to help.

‘Blink reminder’ apps are designed for dry-eye computer users and are free to download. (go to glaucoma.org.nz to find out more).

Adjust your diet: Increasing your dietary intake of essential fatty acids (EFA) to include Omega 3 can help reduce dry eye symptoms. Good natural sources of Omega 3 include oily fish (such as salmon) and linseed (or flaxseed) oil. In addition, Lacritec and Theratears have supplemental products specially formulated for dry eyes. AFT’s eye drops NovaTears®+ Omega-3 also contain it.

It is also essential to stay hydrated, so drink plenty of water.

Perform eyelid hygiene: Tear film quality can adversely affect a lack of oils due to blocked glands (meibomian gland dysfunction). Thoroughly cleaning your eyelid margins, ideally with commercially prepared lid cleansers from your pharmacy, helps to remove any crusts (signs of blepharitis) from around the eyelashes. Warm compresses,
using a wheat or flaxseed bag heated in the microwave (Figure1 ), helps unblock the glands by melting the oils.
After warming the eyelids for at least 5 minutes, it’s helpful to roll your finger gently over your eyelids, towards the edges (i.e., rolling with a downwards motion for the top lid and upwards for the bottom lid) to help squeeze the oils out of the glands (Figure 2). It should be noted that these are chronic eyelid conditions and so need regular and long-term commitment if management succeeds.

Eyelid position correction: The eye’s surface can also become dry because tears are not evenly distributed across the ocular surface. This can occur because of lumps on the eye’s surface, such as pingueculums or pterygia. For tears to be spread evenly over the surface, the eyelids must be in good contact with the eye surface. Eyelids that are floppy, lax or turned out (ectropion) can also worsen the tendency to dry eye. While artificial tear drops can help, surgical eyelid position correction may be required.

Use artificial tears: Dry eye is most commonly managed with artificial tear supplements (drops). Most drops are best suited to aqueous deficient dry eye by boosting tear volume, but some newer products target the tear film oil layer to cater to those with evaporative dry eye. The products range in viscosity (runniness). Gloopy eye drops provide the most prolonged relief from symptoms but causes transient blurring on application. This is well tolerated by patients with moderate to severe dry eye, but those with milder symptoms might prefer a less viscous (a runnier) eye drop. While generally safe, the main precaution is to restrict excessive use of preparations with preservatives, as preservatives can cause ocular surface toxicity and worsen dry eye symptoms.

Consider punctal plugs: Punctal plugs are another solution for a dry eye that doesn’t produce enough tears (aqueous deficiency). Punctal plugging is when tiny silicone plugs are inserted in the drainage channels (puncta) on the inner corners of your eyelid margins, stopping the tears (or tear supplements) from draining out, keeping the eye’s surface wetter
for longer.

Review medication side effects: If prescribed medications cause significant dry eye, your general practitioner (GP) or specialist might consider alternatives. However, the benefits of your medication often outweigh the side effect of dry eye, and other means of managing the dry eye must be sought.

What does the future hold for dry eye: Preserving the ocular surface is key in glaucoma patients, particularly those with existing dry eye disease and younger patients who may have decades of therapy ahead of them. New Zealand’s lack of subsidised preservative-free glaucoma medications was highlighted as a future challenge for ophthalmologists treating glaucoma.

Professor Jennifer Craig, from the University of Auckland, authored this clinical article for Contact Lens Update Issue 70. “Taking DED management to the next level.”

Glaucoma New Zealand supports research in this area in the hope that we will see a wider variety of eye drops available for New Zealand glaucoma patients in the not-too-distant future.