New method for evaluation of early phase tear clearance by anterior segment optical coherence tomography

Abstract

ABSTRACT.Purpose: To describe a new method of measuring early phase tear clearance by anterior segment optical coherence tomography (AS-OCT). Methods: Sixty normal subjects were divided into a young group (30 subjects; 29.6 AE 7.2 years) and an elder group (30 subjects; 71.4 AE 10.8 years). AS-OCT (CASIA SS-1000, Tomey, Japan) with customized software was used to record the tear meniscus at the centre of the lower eyelid. Five microlitres of lukewarm saline solution was dropped into the lower conjunctival sac, and an image of the tear meniscus was obtained immediately and again 30 seconds after natural blinking. The tear meniscus height (TMH) and tear meniscus area (TMA) were measured in the AS-OCT images, and the percentage decrease in the TMH and TMA was used as a measure of the tear clearance. Correlations between tear clearance and clinical features including degree of conjunctivochalasis, degree of protrusion of inferior lacrimal punctum, distance of lacrimal punctum from the Marx line and fluorescein clearance rates were also determined in another healthy population consisting of 30 subjects. Results: The OCT tear clearance rate was 35.2 AE 11% for TMH and 28.1 AE 12.4% for TMA in the young group, and 12.4 AE 7.3% and 6.2 AE 9.1%, respectively in the elder group. The differences were significant for both the TMH (p = 0.017) and the TMA (p = 0.024). The OCT-determined tear clearance was positively correlated with the fluorescein clearance rate, and negatively correlated with the distance between the lacrimal punctum and Marx line, degree of conjunctivochalasis and degree of lacrimal punctum protrusion. Conclusion: AS-OCT can be used as a rapid, non-invasive and quantitative method of determining the early phase tear clearance rate in a normal healthy population.

Effect of non‐invasive tear stability assessment on tear meniscus height

“…Because there is no single diagnostic tool for dry eye, better diagnostic performance should be archived when the tests are used in combination or in appropriate series. Recently, new techniques such as tear meniscus radius measurement with portable slit-lamp mounted, digital meniscometer (Bandlitz et al 2014) or early phase tear clearance using OCT (Zheng et al 2014) have been developed. It is important that TMH should be assessed at least before tests that require forced eye opening.…”

The tear turnover and tear clearance tests – a review

“…New studies show that there is still room for improvement in the field of tear turnover assessment and new techniques are still being developed to assess TTR due to the need to develop more clinically applicable, objective and less time-consuming methodologies. These techniques include measuring tear meniscus dynamics with optical coherence tomography [93,94,95] and tear fluorescein wash-out rate by means of fluorescein profilometry [96].…”

“…This technique was used to study a decrease of tear clearance as a function of age [93] and was compared with the fluorescein clearance test results. In that study 5 µl of 0.9% saline solution was instilled to the eye and changes in tear meniscus morphology (tear meniscus height -TMH and tear meniscus cross-sectional area -TMA) over time were followed [93]. The OCT method of TCR evaluation is less invasive and relatively short (5 minutes).…”

New method for viewing Krehbiel flow by polymethylmethacrylate particles suspended in fluorescein solution

“…; Xu & Tsubota ; Sahlin & Chen ; Zheng et al. ); however, all of these are indirect methods. In addition, some methods require fluorescein dye to be used as a tracer (Jones ; Zappia & Milder ; Webber et al.…”

“…), and another uses anterior segment optical coherence tomography which also requires a special instrument (Zheng et al. ). It would be better if the dynamics of the tear flow in the tear meniscus can be examined by slit‐lamp biomicroscopy because a slit‐lamp is commonly available in the general clinic.…”