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Milton Hom, Justin Kwan; Prevalence of dry eye sub-types and severity of evaporative dry eye using objective tests. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4339.
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© ARVO (1962-2015); The Authors (2016-present)
Dry eye have been defined as two basic sub-types: aqueous tear deficient (ATD) and evaporative dry eye (EDE). Until recently, the overlap between sub-types (known as Mixed) has not been documented much. Also, there is a scarcity of information regarding prevalence of severity levels within EDE. We looked at the prevalence of dry eye categories and severity of EDE in consecutive patients.
Objective tests were performed to classify the dry eye into three categories: ATD, EDE or meibomian gland dysfunction (MGD) and Mixed. EDE was determined by meibomian gland expression of Grade 1 or higher. ATD was determined with Schirmer I score (without anesthesia) of 5mm or lower. The average measurement of both eyes were used. Mixed was determined as a combination of ATD and EDE. The EDE category was broken further down by expression. Gland expression was performed with firm digital pressure and graded in 0.5 increments, from Grade 0 to 4. The grades were 0: clear, low viscosity, easily expressible; 1: clear to mildly opaque, few particles, low viscosity; 2: opaque or many particles, medium viscosity; 3: opaque, solid (toothpaste); 4: not expressible.
166 patients were studied. 77 patients were classified as ATD, EDE or Mixed. EDE only was 67.5% (52/77), ATD only 24.6% (19/77) and Mixed was 7.8% (6/77). Within ATD, 76% (19/25) was pure ATD and 24% (6/25) was Mixed. For EDE, 89.6% (52/58) was pure EDE and 10.3% (6/58) was Mixed. Out of the total number of patients, 34.9% (58/166) were classified as EDE with Grade 1 or higher, while 65.1% (108/166) had a normal quality of expressed meibum. Within the EDE category, 67.2% (39/58) were Grade 1.0 to 1.9, 22.4% (13/58) were Grade 2.0 to 2.9, 6.9% (4/58) were Grade 3.0 to 3.9 and 3.4% (2/58) were Grade 4.0.
Mixed category of EDE and ATD was the smallest sub-type, while EDE formed the largest, followed by ATD. Within the EDE/MGD classification, about 2/3rds was classified as mild. Less than 5% was classified as non-expressible. According to the MGD workshop, the descriptors for meibum expressed would classify the majority of this cross section as subclinical MGD to symptomatic minimal MGD.
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