Meniscometry

Objective assessment of the lower tear meniscus — an important reservoir of the preocular tear film.

How to do the test

Ask the patient to look straight ahead at a distant target, either over your shoulder or at a fixation light placed in front of the opposite eye. Allow a short period for the patient's blinking to stabilise.

The room should be free from significant air draft, particularly around the eye being tested, as airflow can alter the tear meniscus and affect the measurement.

1. Focus the tear meniscus

Once blinking has stabilised, identify the lower tear meniscus, seen as a bright reflection along the lower lid margin.

Bring the meniscus into sharp focus and position it in the centre of the red triangle displayed on the live video screen.

2. Check the analysis graph

When the meniscus is adequately focused and positioned, a graph will appear in the analysis window.

For a good-quality measurement, the graph should approximate the characteristic bi-peaked pattern shown in the reference image.

3. Capture the measurement

When the graph is satisfactory, click the Bluetooth switch or press any key on the keyboard.

OSDx will then automatically capture and validate the measurement. If the acquisition is accepted, the result fields will be populated automatically.

Tip: A sharply focused meniscus and a clean, approximately bi-peaked graph are the best indicators that the measurement is ready to be captured.

Clinical importance

The tear meniscus contains a substantial proportion of the tear volume present on the ocular surface. Its dimensions therefore provide useful information about tear volume and aqueous tear availability. Meniscometry is non-invasive and is particularly useful when performed early in the examination, before procedures that may stimulate reflex tearing.^1,2

A reduced tear meniscus supports aqueous-deficient dry eye, whereas an unusually large meniscus may occur with reflex tearing or impaired tear drainage. Meniscus measurements should always be interpreted with symptoms, ocular-surface findings and other tear-film tests rather than as an isolated diagnostic test.^3,4

Parameters reported by OSDx

TMH

Tear Meniscus Height is the vertical height of the lower tear meniscus. It is the most familiar clinical measure of meniscus size and provides a practical surrogate for tear volume. Normal values depend on the imaging method, but a lower TMH around 0.2–0.3 mm is commonly reported in healthy eyes; values below about 0.2 mm increase suspicion of aqueous tear deficiency.^3,5

TMR

Tear Meniscus Radius (TMR) describes the radius of curvature of the meniscus profile. A smaller radius generally corresponds to a smaller tear reservoir. Meniscus radius, like TMH, has been shown to discriminate tear-deficient eyes from controls and adds geometric information that height alone cannot provide.^1,6

Meniscus Angle

Meniscus Angle is OSDx's geometric descriptor of the relationship between measured TMH and TMR. It may be thought of as an estimate of the apparent angle formed by the tear meniscus profile at the lid margin. Although analogous to a contact-angle concept, it should not be interpreted as a conventional corneal or material wetting contact angle. Its main value is to describe meniscus shape and to complement TMH and TMR during serial assessment.

Suggested terminology: “Meniscus Angle” is preferable to “Contact Angle” in the user interface and report because it avoids implying a standard physicochemical contact-angle measurement.

How to interpret the result

Low TMH with a small TMR: supports a reduced tear reservoir and may be seen in aqueous-deficient dry eye.
Higher TMH: may reflect adequate tear volume, but excessive values can occur with reflex tearing or reduced lacrimal drainage.
Serial measurements: are most useful when acquisition conditions and test sequence are kept consistent.
Interpret the three parameters together: TMH describes height, TMR describes curvature, and Meniscus Angle provides a compact descriptor of meniscus geometry.

Test sequence matters. Prolonged forced eye opening and other ocular-surface procedures can alter TMH. Meniscometry is best performed before tests likely to stimulate tearing.²

Reference values

Published TMH values vary with technique and population. Healthy-eye means close to 0.20–0.30 mm are common in non-invasive imaging studies. One study reported 0.20 ± 0.05 mm in normal subjects versus 0.14 ± 0.03 mm in aqueous-deficient dry eye, while another OCT study found a diagnostic threshold of approximately 0.21 mm.^2,4

Because measurements obtained by different instruments are not necessarily interchangeable, OSDx values are best interpreted in the clinical context and compared longitudinally using the same acquisition method.⁷

References

1. Nichols KK, et al. International Workshop on Meibomian Gland Dysfunction: Report of the Diagnosis Subcommittee. Invest Ophthalmol Vis Sci. 2011;52:2006–2049.

2. Koh S, et al. Effect of non-invasive tear stability assessment on tear meniscus height. Acta Ophthalmol. 2015;93:e135–e139. PMID: 25308575.

3. Doughty MJ, Laiquzzaman M, Button NF. The tear (lacrimal) meniscus height in human eyes: a useful clinical measure or an unusable variable sign? Cont Lens Anterior Eye. PMID: 16303478.

4. Application of anterior segment optical coherence tomography for measuring tear meniscus height in the diagnosis of dry eye diseases. PMID: 19957689.

5. Dry eye disease: an introduction. PubMed PMID: 40115641. Figure reference describes normal TMH as 0.2–0.3 mm.

6. Mainstone JC, Bruce AS, Golding TR. Tear meniscus measurement in the diagnosis of dry eye. Curr Eye Res. 1996. PMID: 8670769.

7. Baek J, Doh SH, Chung SK. Comparison of tear meniscus height measurements obtained with the Keratograph and Fourier domain optical coherence tomography in dry eye. Cornea. 2015;34:1209–1213. PMID: 26266429.