Spectral OCT can be used to measure tear meniscus

Issue: November 2012

Spectral optical coherence tomography was shown to be highly sensitive and specific for diagnosing dry eye and correlates well with the Schirmer’s test when measuring lower tear meniscus parameters, according to a recent study published in Optometry and Vision Science.

A total of 111 eyes in consecutive patients were enrolled in the study to evaluate the use of lower tear meniscus measurements obtained with spectral optical coherence tomography (OCT) in quantitative tear evaluation and diagnosis of dry eye syndrome. Patients underwent a general ophthalmic examination, and lower tear meniscus was evaluated using the RTVue (Optovue, Fremont, Calif.) with cornea-anterior segment lens short. Tear meniscus cross-section area (TMA), tear meniscus height (TMH) and tear meniscus depth (TMD) were measured. OCT measurements were taken immediately after blinking to avoid the effects of delayed blinking.

Schirmer’s test results and the tear meniscus parameters from the spectral OCT were compared in regard to sensitivity and specificity. The highest correlations were TMA (86.11% and 85.33%), followed by TMH (80.56% and 89.33%), and the weakest were TMD (77.78% and 52.7%).

“It confirms that spectral OCT can be used both for quantitative evaluation of the tears and diagnosis of dry eye syndrome. It has high sensitivity and specificity in diagnosis of dry eye syndrome.” Bartlomiej J. Kaluzny, MD, the study’s co-author, told PCON in an interview. “It does not provide direct cutoff values, but the clinician is informed which values to expect in the case of dry eye syndrome, with the use of Optovue. We should be aware that results obtained with different OCT devices may differ.”

Positive correlations were also found in the break-up time after fluorescein solution instillation and subjective symptoms.

According to Zhou et al., spectral OCT can measure the lower tear meniscus with better reproducibility than previously used OCT instruments. Their results in a separate study showed better coefficient of variation for meniscus height and area measurements than previous OCT results.

Several technologies can be used to assess the tear meniscus, but have the disadvantage of invasiveness, Kaluzny and colleagues said.

A traditional noninvasive method of measuring the tear meniscus is at the slit lamp. However, it does not always easily identify the tear meniscus, the authors said, and the instillation of fluorescein may interfere with the tear volume.

Spectral OCT provides noncontact imaging of the tear meniscus and gives “noninvasive, quick and objective measurements,” Kaluzny said. It also provides detailed tomograms on which the meniscus is seen clearly and also has a high acquisition speed to evaluate the meniscus changes over time.

Two drawbacks for using OCT to measure tear meniscus are the relatively high cost of the instrument and the fact that it provides information only on the quantity of tears. In addition, this type of testing may have lower reliability in patients with ocular surface disorders such as conjunctival folds, disorders of the eyelid margin and conjunctivochalasis, according to Kaluzny. – by Cheryl DiPietro

References:

Czajkowski G, Kaluzny BJ, Laudencka A, Malukiewicz G, Kaluzny JJ. Tear meniscus measurement by spectral optical coherence tomography. Optom Vis Sci. 2012;89(3):336-342.
Zhou S, Li Y, Lu AT, et al. Reproducibility of tear meniscus measurement by Fourier-domain optical coherence tomography: a pilot study. Ophthalmic Surg Lasers Imaging. 2009;40(5):442-447.
Bartlomiej J. Kaluzny, MD, can be reached at the department of ophthalmology, Nicolaus Copernicus University, Bydgoszcz, Poland; bartka@by.onet.pl.

Disclosure: None of the authors has a financial interest related to this topic.