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A closer look at dry eye syndrome


29 Apr 2010

Definition of dry eye syndrome

Dry eye syndrome 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 syndrome 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 are:

  • Decreased tear production;
  • Increased tear evaporation;
  • Incorrect composition of tears.

Dry eye is a catch-all term referring to abnormalities of the tear layer which normally coats the surfaces of the eyes, providing clear vision and protecting sensitive surface tissues. Other names for dry eye syndrome include chronic dry eye, dry eye disease and keratoconjunctivitis sicca.

How dry eyes develop

Mucous-secreting cells create the mucin layer. Mucous coats the cornea and protects the surface. The superficial lipid layer of the tear film is derived from the meibomian glands, embedded within the eyelids. The gland ducts open on the eyelid margin. The lipid layer serves to reduce evaporation of underlying aqueous fluid in the open eye. Abnormalities in the secreted lipids result in increased evaporation of tears.

The aqueous layer of the tear film is produced by the lacrimal gland, beneath the upper eyelid. This layer provides moisture, oxygen and electrolytes to the cornea. The concentration of the aqueous layer increases as a result of dry eye and can lead to increased tear osmolarity. In severe dry eyes the tear hypertonicity has been shown to cause ocular surface disease.

Eye surface inflammation is the key mechanism of ocular surface injury in dry eye and results in further cell damage. Inflammation may be initiated by dryness, hypertonicity of tears, microtrauma from eyelids, proinflammatory substances released by the lacrimal glands and a reduced supply of supportive factors from tears. Inflammation is enhanced by cytokines secreted by damaged surface epithelial cells and lymphocytes and leukocytes that leak out from dilated conjunctival blood vessels. Ocular surface inflammation reduces surface wettability and tear film stability1. 

Symptoms

Patients will present with some or all of the following symptoms:

  • Eyes tire easily, particularly noticeable when reading, watching television or using a computer;
  • Eyes feeling sore or gritty;
  • Sensitivity to light (photophobia);
  • Excessive mucus discharge are also common symptoms.

Mild

dry eye conditions can usually be managed satisfactorily with artificial tear supplements, punctal plugs, lid therapy and other common treatments. Millions of people may suffer from dry eyes time to time 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 blindness.

Epidemiology and causes

Dry eye syndrome is an extremely common eye condition and has a wide range of causes, including:

  • Smoky and dusty environments;
  • Rheumatoid arthritis;
  • Menopause;
  • Air conditioning;
  • Car heaters;
  • Air currents;
  • Elective surgeries such as LASIK.

It has a higher prevalence among women and those over 60 years old.

Diagnosis and treatment

Dry eye syndrome can be confirmed by assessing tear break-up time or carrying out the Schirmer or Rose Bengal test.

The most widely used and accepted treatments for dry eye syndrome are summarised below. While we hope that you will find this useful, please note that it is not intended to be a recommend treatment protocol, as each patient’s symptoms and circumstances are unique and will often require a combination of therapies.

New educational resource

Dryeyesmedical.com has been developed to provide a comprehensive source of advice, information and up-to-date learning about dry eye syndrome, particularly for health and medical professionals practicing in the UK.

The content is impartial and broad-ranging and includes a range of resources developed specifically for health professionals. These can be used for training purposes, and also for educating patients about dry eye syndrome. There are also posters to download including ‘how to use eyedrops’.

Dryeyesmedical.com details the symptoms and the commonly used tests to diagnose dry eye syndrome. It summarises the most widely used and accepted current treatments for dry eye syndrome, including ocular lubricants (artificial tears), anti-inflammatories, anti-allergy treatments, dietary and oral therapies and surgical options.

The latest research papers into dry eye syndrome will be stored in the research library of the website for use by medical professionals. In addition, submissions are invited from those wishing to publish their research on our site, or post previously published research.

For those suffering from dry eye syndrome, the Patient Zone will provide user-friendly information to support diagnosis and treatment advice. There is also a series of patient fact sheets, including ‘how to use eye drops’.

References
1. Yang C, Sun W, Gu Y (2004). A clinical study of the efficacy of topical corticosteroids on dry eye. Prog Retin Eye Res; 23(4): 449-74. 


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