TFOS DEWS II retains the division of DED into aqueous deficient and evaporative subtypes and underscores that each can lead to the other so that they frequently co-exist. However, TFOS DEWS II also introduces a new classification scheme that ultimately allows the identification of patients with DED who are likely to respond to available treatments.
The classification scheme first considers whether a patient presents with symptoms.
“The fact that patients can have symptoms of dry eye without clinically apparent abnormalities of the ocular surface has been known for some time and increasingly appreciated in the past few years,” Dr. Nelson said. “The members of TFOS DEWS II thought this was a key issue.”
In the classification scheme, patients with symptomatic and asymptomatic presentations are further broken down based on the presence or absence of signs of ocular surface disease (OSD). Asymptomatic patients with no signs are considered normal and require no treatment. Asymptomatic patients with signs of OSD may either be in a prodromal stage and predisposed to develop dry eye or might have a neurotrophic condition such that they do not experience sensations from existing ocular surface damage.
The classification scheme shows that symptomatic patients with no signs of DED could either be in a preclinical state or have a neuropathic condition rather than dry eye. Pain management is the appropriate intervention for the latter patients.
One of the challenges clinicians have faced has been in the care of patients who complain bitterly of symptoms that are associated with DED but who have no signs of OSD. TFOS DEWS II recognizes that the symptoms in these patients probably have a neurogenic etiology, and they need to be treated differently, he said.
Symptomatic patients with signs of OSD may have classic DED or some other OSD that has overlapping clinical features, such as allergy or infection. Triaging questions should enable the differential diagnosis in these cases.
Patients who are determined to have DED are then subtyped according to whether they have an aqueous deficient, evaporative, or mixed condition and managed according to the categorization.