2.3.1. Questionnaire

All participants underwent a symptom evaluation using the Ocular Surface Disease Index (OSDI)© questionnaire (Allergan, Inc., Irvine, CA, USA). Briefly, the OSDI questionnaire consisted of 12 questions, each question graded from 0 to 4. The total OSDI scores on the scale of 0 to 100 were then calculated with the OSDI© (Allergan, Inc., Irvine, CA, USA) formula (sum of scores) × 25/(12 questions), with higher scores representing greater symptoms severity [18].

#### 2.3.2. Strip Meniscometry

Strip Meniscometry (SM) Tube (Echo Electricity Co., Ltd., Fukusima, Japan) has been performed as in previous studies [15,16]. Briefly, one end of the strip was held by the investigator against the lower tear meniscus for five seconds, and the length of wetting of the thread read directly from the millimeter markings provided.

#### 2.3.3. Fluorescein Breakup Time (TBUT)

Briefly, a minimally wet (saline) fluorescein strip (Fluorets, Bausch and Lomb, Rochester, NY, USA) was used to instill fluorescein dye. The procedure for this step has been previously described [19,20].

#### 2.3.4. Schirmer's I Test

The Schirmer's I test was done with standard 5 mm wide test strips (Clement Clark®, Essex, UK) with a notch for folding, and without prior anesthesia. The strips were positioned over the inferior temporal half of the lower lid margin in both eyes, and participants' eyes subsequently closed. After 5 min, the extent of tear wetting of the strip was measured to the nearest mm using a ruler [19].

#### 2.3.5. Meibomian Gland Dysfunction Examination

The characteristics of the meibum secreted was evaluated by one ophthalmologist using the right thumb with gentle pressure, under slit-lamp microscopy and graded as follows: 0: clear meibum, 1: colored meibum with normal consistency, 2: viscous meibum, 3: inspissated meibum, and 4: blocked meibomian gland. This was used as a measure of MGD severity.

#### 2.3.6. Slit-Lamp Examination

Other clinical features were examined using a slit lamp biomicroscope. This included scurfing/crusting, subtarsal papillary reaction [19,21], and regularity of the eyelid margin [22]. Corneal sensitivity was also screened using a cotton wisp [23].

#### *2.4. Statistical Analysis*

Statistical analysis was performed using StataCorp. 2013. Stata Statistical Software: Release 13.1. College Station, TX: StataCorp LP.

The SM variable was evaluated for its frequency distribution and normality. The univariate association of SM with continuous variables was evaluated by categorizing these variables into binary categories, and the association evaluated with the T-test. Whenever there were more than two categories, analysis of variance was used to determine the statistical significance. Univariate logistic regression was performed between meniscometry category and sex, age, ethnicity, and the six ocular surface signs (tear break up time (TBUT), fluorescein corneal staining, Schirmer's I test, NLMEG, presence of scurf, and inferior fornix papillary grade).

Multivariate logistic regression was performed with meniscometry category as the dependent variable. We performed models using only the clinical signs and demographics of patients, as well as models introducing the predisposing factors of dry eye such as concomitant drugs and

medical conditions. We performed logistic regressions with two thresholds for SM as the dependent variable. Statistical significance was based on alpha of 0.05.
