Reference values of the lacrimal punctum and vertical canaliculus OCT-parameters and their variability

Relevance In order to study the condition of the horizontal section of the lacrimal ducts (LSLD), ultrasound biomicroscopy is used, which is a contact method that has a mechanical effect on tissues, and non-contact optical coherence tomography (OCT), which has a higher resolution. The lacrimal punctum profile on OCT scans has a gentle temporal and steep nasal edge, the lumen of the canal narrows in depth and has a V-shape, in some cases with an ampulla at the beginning. The OCT parameters are assessed: the outer and inner diameter of the lacrimal punctum, the width of the lumen and the length of the vertical segment of the lacrimal canal, the depth of the lacrimal well in the lumen of the lacrimal punctum. The method for measuring all parameters, with the exception of the inner diameter of the lacrimal punctum, is standardized. Spectral OCT of the lacrimal punctum and canal was first used by Wawrzynski J.R. et al., the results are presented in the table [1]. Later, other researchers also evaluated the OCT parameters of these structures in the norm. The internal diameter of the lacrimal punctum was estimated by Alam R.S. et al. at the level of the initial narrowing of its lumen, and by Livan Turkoglu E.H. et al. at the level of 100 μm from its external diameter [2, 3]. The obtained data are presented in the table. The above studies did not take into account the dependence of the lacrimal duct sizes on ethnicity, gender and age. Singh S. et al. evaluated the OCT parameters of the lacrimal punctum and canaliculus in representatives of the South Asian population (see table) [4]. The variability of the sizes of these structures depending on gender and age was analyzed by Naz H. et al., dividing healthy volunteers into 4 age groups (see table) [5]. The authors noted an increase in the external diameter of the lacrimal punctum from the 3rd to the 5th decade of life and its subsequent decrease. The internal diameter, on the contrary, narrowed from 21 to 65 years, after which it expanded, apparently due to age-related changes in the surrounding tissues. All dimensions were higher in men, which may also explain the more pronounced age-related narrowing of the lacrimal well in women, especially in postmenopausal age. The depth of the lacrimal well decreased with age from 85–91 to 40%. The ampulla of the lacrimal canaliculus was detected in 8.5% of cases, more often in people under 50 years of age. Conclusion Thus, OCT of the lacrimal punctum and vertical segment of the lacrimal canaliculus allows for accurate measurements of the parameters of these structures for the purpose of diagnosing diseases and assessing the effectiveness of treatment. However, further studies with a larger sample size are required to create a normative database and implement it in clinical practice. Key words: OCT; lacrimal punctum; vertical segment of the lacrimal canaliculus; horizontal section of the lacrimal ducts