Evaluation Of Anterior Segment Optical Coherence Tomography Findings In Dry Eye Patients

Current definition of dry eye states that it is ‘a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface.’

Worldwide prevalence rates reported in the literature show wide variability and there is lack of standardization of the selected population, dry eye questionnaires, objective tests and dry eye diagnostic criteria. Purpose of our study is to evaluate the Anterior Segment Optical Coherence Tomography (ASOCT) findings in dry eye patients and assess the role of these parameters in Dry Eye Disease (DED) diagnosis

The study was conducted on patients attending the Outpatient Department of the Ophthalmology department of St Stephen’s Hospital, New Delhi during the study period. It was a single-institution, observational study and included 58 eyes of 29 dry eye patients of either sex diagnosed based on Ocular Surface Disease Index (OSDI) scores. Primary and secondary outcome variables measured were the Tear Meniscus Height (TMH) and Tear Meniscus Area (TMA) resepctively, both mesasured on ASOCT.

Patients of either sex, aged 18 years and older with clinically confirmed dry eye disease (based on OSDI score) were included. Patients with previous ocular trauma, prior corneal transplantation surgery or history of surgery of the lacrimal system, recent use of contact lenses, ocular pathologies such as glaucoma, ocular infections or allergy, diabetic retinopathy were excluded. All subjects were tested by a single observer, in a dimly lit room with controlled temperature and humidity. An image of the vertical cross section through the central inferior tear meniscus was used for all scans. ASOCT mesaurements were followed up with routine clinical dry eye tests (Schirmer I test, tear film breakup time and ocular surface staining).

The mean age of the patients studied was 40.21 ± 11.79 years ranging from 22 to 65 years, with 20 male (68.97%) and 9 female (31.03%) subjects. The mean OSDI score in the study was 33.17 ± 11.39. Mean TMH values of all the right and left eyes in the study were 270.69+162.2 µm and 274.69+166.65µm, respectively and had statistically significant difference across the dry eye severity groups. Mean TMA value of all the eyes in the study was 0.04+0.06mm² with statistically significant difference amongst the dry eye severity groups. TMH and TMA values closely matched with dry eye severity. The clinical dry eye tests correlated poorly with OSDI scores, their correlation with the OCT findings was found to be variable and insignificant.

The parameters, Tear Meniscus Height (TMH) and Tear Meniscus Area (TMA ) mesasured on ASOCT, showed consistency in terms of correlation and statistically significant difference amongst dry eye severity groups. The routine clinical tests of dry eye had variable and insignificant results with poor correlation.

The invasive nature of the clinical diagnostic tests could have resulted in unequal reflex lacrimation in different subjects and influenced the test results. Tear Meniscus Height and Tear Meniscus Area values measured on Anterior Segment Optical Coherence Tomography have significance in distinguishing dry eye severity with the advantage of being a non-invasive procedure.