When the Tear Film and Ocular Surface Society (TFOS) published the Report of the TFOS International Dry Eye Workshop in 2007, which later became known as TFOS DEWS, the scope of dry eye disease (DED) was expanded. Then, in 2017, TFOS DEWS II was published in The Ocular Surface journal, updating how DED is understood and managed.
Perhaps one of the most important updates in DEWS II is the understanding that identifying subgroups of DED is important for classification, however they should be viewed as part of a “spectrum of disease, rather than being distinct pathophysiological entities.” [i] Dry eye disease is complex and the approach to diagnosing and managing it is multifaceted. Recognizing this paves the way for a personalized treatment plan.
Dry Eye Disease Definition
TFOS DEWS II defines dry eye as being “characterized by a loss of homeostasis of the tear film, and accompanied by ocular symptoms, in which tear film instability and hyperosmolarity, ocular surface inflammation and damage, and neurosensory abnormalities play etiological roles.” [i]
Having a common definition is important in guiding diagnostic methods and treatments.
Dry Eye Disease Diagnosis https://www.tearfilm.org/public/TFOSDEWSII-Executive.pdf
The DEWS II report establishes guidelines for diagnosis of DED. They include a multi-step approach.
- Triaging Questions/ Risk Factor Analysis – Screening questions help to identify possible causes of symptoms that might mimic DED, for example allergies. [ii]
- Symptom Assessment – DEWS II recommends using the Dry Eye Questionnaire-5 (DEQ-5) or the Ocular Surface Disease Index (OSDI) to indicate whether or not a patient might have DED. A positive symptom score on either assessment indicates that a more a more detailed examination is warranted to look for clinical signs of DED. [ii]
- Diagnostic Tests – In addition to symptoms, the clinical protocol for DED diagnosis “requires the presence of at least one abnormal homeostatic marker.” [i] Clinical tests include:
- Tear Break-Up Time (TBUT) – a measure of how long it takes for the tear film to evaporate after blinking.
- Schirmer’s Test – a measure of tear production
- Corneal Staining – when special dyes are used to highlight damage or dryness on the surface of the cornea
- Eyelid examination – checking for signs of blepharitis, which can contribute to dry eye
- Further Tests– After a diagnosis has been confirmed (at least one positive symptom score and one or more positive homeostatic markers), further subtype classification tests are warranted. [ii] These include:
- Meibography
- Lipid interferometry
- Tear volume measurement
Dry Eye Disease Subtype Classifications
The subtype classification tests help to determine where DED falls on the spectrum between two subtypes – aqueous deficient dry eye (ADDE) – dry eye caused by reduced tear production from the lacrimal glands [ii], and evaporative dry eye (EDE) – dry eye caused by problems with the oily layer of the tear film, leading to increased tear evaporation. [ii] These tests also help to understand the severity of DED and guide patient-specific treatment strategies.
Dry eye disease is a complex condition that can cause a variety of symptoms. DEWS has played a significant role in improving understanding and management of DED by introducing a comprehensive definition, a multi-stage diagnostic approach and a focus on individualized treatment plans.
[i] https://www.aao.org/eyenet/article/the-tfos-dry-eye-workshop-ii
[ii]Â https://www.tearfilm.org/public/TFOSDEWSII-Executive.pdf