What is dry eye syndrome?
Dry eye syndrome is a condition in which the eyes can’t make enough tears, or the tears evaporate too quickly. This can cause the eyes to become dry, inflamed and uncomfortable. Dry eyes is a catch-all term referring to abnormalities of the tear layer that normally coats the eye, aiding clear vision and protecting sensitive surface tissues. Other names for dry eyes include: dry eye syndrome, chronic dry eye, dry eye disease and keratoconjunctivitis sicca.
Dry eyes is a multifactorial disease of the tears and ocular surface that results in a range of symptoms, including discomfort, visual disturbance, tear film instability and potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface. Dry eye is a disturbance of the lacrimal functional unit, which comprises the lacrimal glands, ocular surface (cornea, conjunctiva and meibomian glands) and eyelids, together with the sensory and motor nerves that link them.
The key features of dry eye syndrome that result in inadequate lubrication are:
- Decreased tear production;
- Increased tear evaporation;
- Incorrect composition of tears.
Patients and symptoms
Dry eye syndrome is a common condition, estimated to affect up to a third of people at some time in their life. The condition is most frequently seen in those over 60 years of age and is more common in women than men. Patients will present with some, or all, of the following symptoms:
- Feeling like there is something in their eye (foreign body sensation);
- Scratchy, gritty eyes;
- Aching or sore eyes;
- Smarting or burning eyes;
- Eyes tire easily, particularly noticeable when reading, watching television or using a computer;
- Contact lens discomfort or intolerance;
- Excessive mucus discharge;
- Watery eyes;
- Eyes easily irritated by smoke;
- Sensitivity to light (photophobia);
- Fluctuating vision;
- Blurred vision, particularly first thing in the morning and/or late in the day;
- Eyelids ‘stick shut’ at night;
- Eyelids feel ‘heavy’.
Dry eye syndrome has a wide range of causes, including:
- Systemic diseases (Sjögren’s, rheumatoid arthritis, lupus, Stevens Johnson, thyroid disease, Bell’s palsy);
- Eye conditions (meibomian gland disease, blepharitis, ocular rosacea, corneal dystrophies);
- Meibomian gland dysfunction (MGD);
- Elective surgeries, such as laser-assisted in situ keratomileusis (LASIK), photorefractive keratotomy (PRK) and blepharoplasty;
- Eyelid conditions (lagophthalmos, ptosis);
- Drug side effects (antihistamines, diuretics, beta-blockers);
- Eye injuries and burns;
- Chemotherapy and radiation;
- Air conditioning, car heaters, air currents;
- Computer vision syndrome – prolonged use of computers;
- Smoky and dusty environments;
- Wearing contact lenses;
- Vitamin A deficiency;
- Neurological lesions (eg Riley-Day syndrome);
- Absence/abnormality of lacrimal gland/ductules;
- Idiopathic reasons;
- Blink disorders.
In addition to observation of symptoms, there are several established tests for dry eye syndrome. These include:
A 5mm x 35mm blotting paper strip is used to measure the quantity of tears produced over a five minute period. A measurement of less than 6mm indicates dry eye syndrome.
- Tear break-up time
Fluorescein is instilled into the eye and the patient is asked to blink several times and then stop. The time between the last blink and the first appearance of a dark spot on the cornea (formation of a dry area) is then measured. A tear break-up time of less than 10 seconds suggests dry eye syndrome.
- Rose Bengal Test
A red dye (Royal Bengal) is instilled into the eye. Aqueous tear deficiency can then be identified via the staining pattern seen using a slit-lamp.
There are also various questionnaires available including The Dry Eye Questionnaire developed by McMonnies and Ho, and the QE5 Questionnaire. To find out more about these please visit the diagnosis section on www.dryeyesmedical.com
Lifestyle and environment factors
Treatment should initially focus on identifying and addressing lifestyle and environmental factors that may cause or exacerbate dry eye syndrome. These include:
- Smoky or dusty environments;
- Air conditioning/heaters in the home or car;
- Prolonged viewing of computer screens;
- Contact lens wear;
- Over rinsing with water or saline;
- Use of redness-relieving eye drops – eg naphazoline, tetrahydrozoline, phenylephrine or herbals such as witch hazel.
The patient’s medication history should also be reviewed, as topical and systemic antihistamines have been associated with dry eye syndrome. Similarly, hormone replacement therapy (HRT), tricyclic antidepressants (TCAs) and selective serotonin re-uptake inhibitors (SSRIs) can aggravate ocular symptoms. Diuretic therapy should additionally be taken into account.
A good level of daily water intake should be encouraged to aid hydration. As omega-3 fatty acids may reduce tear evaporation and inflammation, oral supplements or dietary intake via fish or flaxseed oil is often recommended.
Artificial tears and lubricants
The term ‘artificial tears’ is commonly used to describe drops, solutions and liquid gels applied directly into the eye. Artificial tears don’t have all the components of real tears – they mainly just act as a lubricant. The term ‘ocular lubricants’ generally refers to more viscous products such as ointments.
For mild or moderate dry eye symptoms:
- Artificial tears alone are usually sufficient to provide relief;
- Hypromellose is the most commonly used product, and can be administered frequently;
- Products containing carbomers or polyvinyl alcohol are longer-acting;
- Sodium chloride is short acting and suitable as ‘comfort drops’ or for use with contact lenses.
Sodium hyaluronate is now seen as the new gold standard for dry eyes. It provides immediate and long-lasting relief for dry or irritated eyes and most products on offer are preservative-free, which means they are less likely to cause additional irritation. Some eye drops contain preservatives and can cause irritation. If someone is sensitive to preservatives, uses soft contact lenses or have a chronic condition, consider switching to a product that is preservative-free.
For severe dry eye symptoms:
- Preservative-free artificial tears are suitable, but consider adding an ocular lubricant ointment to use at night;
- Eye ointments containing paraffins physically lubricates and protect the eye surface from epithelial erosion and are particularly useful when the eye is closed during sleep;
- However eye ointments may be uncomfortable and blur vision and should therefore only be used at night and never with contact lenses;
- Artificial tears containing bicarbonate have been shown to promote healing in severe dry eyes.
- Mild; dry eye conditions can usually be managed satisfactorily with artificial tear supplements, lid therapy and other common treatments. Many millions of people may suffer from dry eyes time to time due to environmental factors and many will be unaware of the symptoms.
- Moderate; dry eye may affect vision more, and will probably affect quality of life a lot more because of chronic pain, eye sensitivity, light sensitivity and restricted activities.
- Severe; dry eye may lead to desiccation of the corneal epithelium, ulceration and perforation of the cornea, an increased incidence of infectious disease and, potentially, serious visual impairment and even blindness.
Moorfields Pharmaceuticals is supporting www.dryeyesmedical.com, which is a resource created especially for those involved in the diagnosis and treatment of dry eye conditions. The Dry Eyes Medical website is peer reviewed by a panel of experts. It includes a variety of useful resources, including an adaptation of a diagram taken from the DEWs (Dry Eyes Workshop) report, which outlines the major etiological causes of dry eye. To find out more about the products and services available from Moorfields Pharmaceuticals please visit www.moorfieldspharmaceuticals.co.uk or call 0207 684 9090.