In the literature, terms such as ''lacrimal groove'' [12], ''nasal canal'' [23], ''nasolacrimal duct'' [27] or ''nasolacrimal canal'' [17, 26, 27] have been used for the nasolacrimal groove formation, but according to Gray's Anatomy [25], the above formations describe different regions. The structure bordered by the anterior lacrimal crest of the maxillary bone and the posterior lacrimal crest of the lacrimal bone is known as the lacrimal groove. Here is located the lacrimal fossa, which houses a pit for the lacrimal sac [10]. When the lacrimal groove is followed inferiorly, it is bordered by the inferior nasal concha and continues as a canal, which is called the nasolacrimal canal. The groove seen along the nasolacrimal canal is known as the nasolacrimal groove (NG). Inside the canal is the nasolacrimal duct, which is responsible for the drainage of tears. Under normal conditions, tears secreted from the lacrimal gland are directed medially and into the upper and lower caruncles with the contraction of the orbicularis oculi muscle. After reaching here, the tear passes first to the lacrimal sac and then to the nasolacrimal duct and reaches the inferior nasal meatus in the nasal cavity [25].
The nasolacrimal duct can be obstructed by acquired or congenital diseases. Congenital nasolacrimal obstruction affecting newborns and infants (5–20%) causes excessive lacrimation (epiphora) due to inadequate drainage of tears from the eye to the nasal cavity, resulting in discomfort and ocular infections [4, 15]. Although obstructions are seen at different points of this lacrimal drainage system, the most common (70%) obstruction is seen at the entrance at the level of the NG [8]. Historically, the first methods used to treat this condition involved conservative measures, but significant advances in surgery and technology have expanded treatment options [4, 5, 24]. Dacryocystorhinostomy, which can be done externally or endoscopically, is still the backbone of therapy today, with a success rate of over 90% [2, 11, 14].
Although various attempts at nasolacrimal duct recanalization and subsequent intubation with less invasive alternatives have been made over the last twenty years, considerable work has to be done before they can match the success rates of dacryocystorhinostomy surgeries [13].
The use of coronary angioplasty balloons in the treatment of congenital nasolacrimal duct obstructions, punctocanaliculoplasty, and revision dacryocystorhinostomy has the potential to greatly alter the health economics of lacrimal drainage diseases in impoverished nations [1, 3, 6]. Therefore, the anatomical features of the NG should be well known in order to determine new interventional techniques or to increase the success rate of existing interventions.
The NG is important for tear drainage and overall ocular health. Despite its importance, there has been little research on the detailed morphometric measurements and morphological aspects of this anatomical component. The current study aims to contribute comprehensive information on the morphometry, morphology, and variability of the nasolacrimal groove. The morphometry of the nasolacrimal groove was analyzed in detail to clarify the anatomy and characteristics of the nasolacrimal groove. We think that the findings obtained from this study may be useful in preoperative planning for interventions in the nasolacrimal duct.