title: Anterior Segment Optical Coherence Tomography for Tear Meniscus Evaluation and its Correlation with other Tear Variables in Healthy Individuals.
abstract: BACKGROUND
  Dry eye is one of the most common ocular diseases in this cyber era. Despite availability of multiple tests, no single test is accurate for the diagnosis of dry eye. Anterior segment optical coherence tomography is the recent tool which can be added in the armentarium of dry eye tests.
  
  
  OBJECTIVE
  To evaluate tear meniscus with anterior segment optical coherence tomography and its correlation with other tear variables in normal healthy individuals.
  
  
  METHODS
  In this prospective cross-sectional observational study, right eye of 203 consecutive patients were studied. All the patients were divided into three groups Group 1, 2 and 3 according to their age ≤20 years, 21-40 years and >40 years respectively. All patients underwent routine ophthalmologic examinations along with slit-lamp bio-microscopy for tear meniscus height measurement, tear film break up time, Schirmer's I test (with anaesthesia) and optical coherence tomography imaging of inferior tear meniscus height. After focusing of the instrument with a Cross Line (CL) centered on lower tear meniscus at 6'0 clock of cornea, a 6 mm long scan was obtained. The tear meniscus height (μm) and tear meniscus area (mm(2)) were measured manually with help of callipers by joining upper corneo-meniscus junction to the lower lid-meniscus junction and tear meniscus height and area within the plotted line respectively and calculated by using the integrated analysis available in the custom software.
  
  
  RESULTS
  There was significant decrease in the all tear variables with the increase in the age. According to age groups in group 1, the mean Schirmer's (24.0±4.9)mm, tear film break up time (11.1±1.9) sec, tear meniscus height on slit lamp (600.2±167.3)mm were higher but decreased in group 2 (21.5±5.4,10.8±1.4, 597.5±186.3) and group 3 (19.8 ± 5.1, 10.2 ± 1.6, 485.6 ± 157.7) respectively. Schirmer's test values and tear film break up time were similar in both sexes (p=0.1 and p= 0.9). Tear meniscus height on slit lamp and Optical coherence based tear meniscus area were similar in both sexes (p=0.5 and p=0.1). However, tear meniscus height on optical coherence tomography was significantly higher in females (p=0.04). Value of Schirmer's and tear film break up time (r =0.2; p= 0.001) and Schirmer's and tear meniscus height on slit lamp (r=0.6; p<0.001) had positive correlation. Tear meniscus height and tear meniscus area on optical coherence tomography had positive correlation (r =.9; p<0.001).
  
  
  CONCLUSIONS
  On optical coherence tomography tear meniscus height and area significantly correlated. Despite higher values of Schirmer's, tear film break up time, Slit lamp based tear meniscus height in younger age group the tear meniscus height and tear meniscus area with optical coherence tomography were lower.
authors.affiliation: Assistant Professor, Department of Ophthalmology, HIMS, Swami Rama Himalayan University , Swami Ram Nagar, Jolly Grant, Dehradun, Uttarakhand, India .
authors.forename: Anuradha
authors.initials: A
authors.lastname: Raj
authors.affiliation: Professor, Department of Ophthalmology, HIMS, Swami Rama Himalayan University , Swami Ram Nagar, Jolly Grant, Dehradun, Uttarakhand, India .
authors.forename: Renu
authors.initials: R
authors.lastname: Dhasmana
authors.affiliation: Professor, Department of Ophthalmology, HIMS, Swami Rama Himalayan University , Swami Ram Nagar, Jolly Grant, Dehradun, Uttarakhand, India .
authors.forename: Ramesh Chander
authors.initials: RC
authors.lastname: Nagpal
keywords: Tear film break up time; Tear meniscus area; Tear meniscus height