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HomemieyecareRedefining Dry Eye

Redefining Dry Eye

Tear Film & Ocular Surface Society – The Dry Eye Workshop Report

Optometry and health care have always been a combination of both art and science. In recent times, however, there has been a move towards more evidence-based practise, embracing science to provide the best patient care.


An excellent example of evidencebased practise is the 2007 Report of the International Dry Eye Workshop (DEWS). A collaborative effort by a large group of international experts in the field, the DEWS has provided improved understanding of dry eye in the areas of definition, epidemiology, pathogenesis, clinical manifestation and treatment options. A similar workshop, sponsored by the National Eye Institute (NEI), was conducted in 1994.

The latest report, compiled over a threeyear period, involved more than 60 international researchers, clinicians and industry specialists, and delivered an:

‘evidence-based review of the present state of knowledge for dry eye disease and the methods used to evaluate, diagnose, and manage the disorder.’

The result of the workshop was an encyclopaedic document on dry eye disease, including the collection and validation of the most recent data, a comprehensive exploration of the literature and the deliberations of many clinicians and scientists. This document is freely available at: www.tearfilm.org

This global collaborative effort was organised and sponsored by the Tear Film and Ocular Surface Society (TFOS), and headed by Dr. David A. Sullivan of the Schepens Eye Research Institute U.S. Australian representatives included Professor Deborah Sweeney and Professor Mark Wilcox of the Institute for Eye Research and the School of Optometry and Vision Science, University of New South Wales (UNSW).

Defining Dry Eye

A significant outcome of the workshop has been a re-definition of ‘dry eye’. This was initiated by the DEWS Definition and Classification Subcommittee and involved a revision of the 1995 NEI/Industry Dry Eye Workshop definition.

The classifications aqueous-deficient dry eye and evaporative dry eye were removed and the roles of tear hyperosmolarity and ocular surface inflammation, and the effects of dry eye on visual function, were integrated into a new definition:

‘Dry eye is a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface.’

The Subcommittee also developed a threepart classification system of dry eye based on the aetiology, mechanisms and severity of the disease.

Aetiopathogenic classification: This classification reflects a more contemporary understanding of dry eye disease and incorporates the multiple causes of dry eye. Aqueous deficient dry eye is categorised into two major groupings: Sjogren syndrome dry eye and non-Sjogren syndrome dry eye. Evaporative dry eye may be intrinsic (e.g. meibomian gland lipid deficiency, poor lid congruity or low blink rate), or extrinsic (e.g. vitamin A deficiency, contact lens wear and a range of ocular surface diseases.)

Mechanistic classification: The core mechanisms of dry eye disease are thought to be hyperosmolarity and tear film instability. The different aetiologies of dry eye often act through common pathways, with interacting mechanisms producing vicious circles and subsequent worsening of the condition.

Severity grading scheme classification: Based on the scheme of the Delphi Panel Report, this classification includes clinical signs and symptoms such as severity and frequency of discomfort, visual symptoms, corneal and conjunctival staining, and the presence of meibomian gland dysfunction.

Incidence Rate

The DEWS Epidemiology Subcommittee reviewed prevalence and incidence data from various populations, and concluded that five to 30 per cent of adults aged 50 years and older had some degree of dry eye. The common clinical impression that dry eye affects more women than men was confirmed, suggesting that hormonal changes are a significant factor. Severe symptoms and/or clinical diagnosis of dry eye in women may be more common in Hispanic and Asian populations compared to Caucasian.

Risk Factors

Common risk factors for dry eye identified by the Epidemiology Subcommittee include old age; female gender; post-menopausal oestrogen therapy; a diet low in omega 3 essential fatty acids; refractive surgery; vitamin A deficiency; radiation therapy; bone marrow transplantation; hepatitis C and certain classes of systemic and ocular medications, including antihistamines.

Diagnosing and Monitoring

One of the main challenges identified by the Epidemiology Subcommittee in dry eye diagnosis is the lack of reliable diagnostic tests to distinguish between those with or without dry eye. In addition, there is no apparent correlation between reported ocular symptoms and the results of clinical tests traditionally used to diagnose dry eye.

Dry eye questionnaires have the advantage of being the easiest to duplicate of the commonly used diagnostic tests. The clinical value of dry eye questionnaires was reviewed, with the conclusion that further research was required to better understand the relationship between the frequency and severity of dry eye symptoms. This would enable clinically meaningful changes in dry eye symptom scores to be captured.

The DEWS Diagnostic Methodology Subcommittee assessed various tests used to diagnose and monitor dry eye, with the following recommendations:

  • Symptom questionnaire
  • Evaporimetry to assess the evaporation rate of tears
  • Non-invasive tear film break-up time
  • Fluorescein break-up time
  • Ocular surface staining grading with fluorescein/yellow filter
  • Schirmer tests with and without anaesthetic
  • Tear osmolarity and tear meniscus assessment
  • Lid and meibomian morphology and meibomian expression

A template on how to employ each of these tests can be found at: www.tearfilm.org

It would be cumbersome to use all of the recommended tests on an individual patient to diagnose dry eye. However, it is incumbent on the clinician to familiarise themselves with the various tests to allow appropriate selection in individual cases.

Management and Treatment

Treatment of a condition will usually follow diagnosis. The section on Management and Therapy in the DEWS report may be the most useful for everyday practise. The Management and Therapy Subcommittee assessed current therapeutic methods of managing dry eye, ranging from conventional artificial tears/lubricants to the more recent immunomodulator therapy of cyclosporine.

The effectiveness of each therapeutic option was assessed.

Tear supplements

While studies often show a degree of improvement in subjective symptoms, the report noted a difficulty in demonstrating objective improvements on the ocular surface and in tear film abnormalities. It also acknowledged a lack of existing clinical evidence establishing the superiority of one lubricating agent over another. However, the report did comment in reference to lubricating agents that, ‘the absence of preservatives is of more critical importance than the particular polymeric agent used in ocular lubricants’, an observation that will come as no surprise to the experienced clinician.

Topical agents

The Subcommittee examined several potential topical agents currently considered by pharmaceutical companies for stimulating aqueous and/or mucous secretion. Two oral cholinergic agonists, pilocarpine and cevilemine, have been evaluated in clinical trials for the treatment of Sjogren syndrome associated keratoconjunctivitis sicca and were found to significantly improve symptoms of dryness and increase aqueous tear production. One side effect of this type of treatment is excessive sweating, which was found in 40 per cent of patients.

Tetracycline is a recommended treatment for acne rosacea and chronic posterior blepharitis due to its anti-inflammatory, anti-bacterial and angiogenic properties.

Cyclosporine was another topical agent recommended in the report, with studies showing significant improvement in patient symptoms.

Other recommendations included serum as natural tear substitute, punctual plugs, contact lenses, dietary supplementation with essential fatty acids and environmental strategies.

Further Information

For keen researchers and scientists, the DEWS Report also details the design and conduct of clinical trials investigating therapeutic interventions for dry eye disease.

The report of the DEWS Research Subcommittee also includes an evaluation of research investigating the basic mechanism underlying dry eye disease. Several areas have been identified as requiring further research, including the determination of the role of the meibomian gland in various forms of dry eye and the mechanism of tear dysfunction. The critical need to understand the structure of the lipid layer and how it changes in meibomian gland dysfunction (MGD) was also a key agenda item.

It is with no surprise that an MGD Workshop has since been established by the TFOS to investigate this common ocular problem, and will operate similarly to the DEWS Workshop. Three renowned Australian researchers will be part of this challenging endeavour – Associate Professor Eric Papas and Professor Mark Wilcox of the Institute for Eye Research and Professor Fiona Stapleton, Head of the School of Optometry and Vision Science at UNSW.

The MGD Workshop report is scheduled to be published by early 2010. Clinicians and researchers around the world will be keenly anticipating its release and the next significant step in the international effort to beat dry eye.

Key Points

Definition of Dry Eye

Disease of the tears and ocular surface, resulting in symptoms of discomfort, visual disturbance and tear film instability.

Incidence

Five to 30 per cent of adults, aged 50 years and older have some degree of dry eye; affects more women; more common in Hispanic or Asian populations.

Diagnosis

Further research required to better understand relationship between objective ocular findings and subjective symptoms.

Therapeutic Treatment

To manage dry eye: tear supplements,topical agents and many other options.


Nikki Peng B. Optom (Hons) is a clinical optometrist at the Institute for Eye Research.

The author would like to thank Daniel Tilia, Jennie Diec, Nicole Carnt and Percy Lazon de la Jara for their assistance and the support of staff at the Institute for eye Research.

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