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The lacrimal apparatus refers to the group of structures responsible for producing and removing tears. It includes the lacrimal gland, which secretes tears, and the duct systems that dispose of these tears. The lacrimal apparatus is responsible for secreting tears that serve to moisten, cleanse, lubricate, and provide immune protection to the surface of the eye.From: Bailey & Love's Essential Clinical Anatomy [2019], The Concise Handbook of Human Anatomy [2019], Fundamentals of Pharmacology [2019]
The lacrimal apparatus includes the lacrimal gland, the gland of the third eyelid, Harders gland when present, accessory lacrimal glands, goblet cells, meibomian glands, and the drainage apparatus. These glands secrete the precorneal tear film. The precorneal tear film serves to maintain an optically uniform ocular surface, is a source of corneal oxygen and a small percent of corneal glucose, provides lubrication, maintains corneal hydration, contains antibacterial lysozyme, and aids in the mechanical removal of debris. Once formed, tears must be removed and this is achieved by the movement of the eyelids in the act of blinking, which close from lateral to medial, displacing the tears toward the lacrimal drainage apparatus. The drainage system consists of the upper and lower puncta, at the medial canthus, the upper and lower canaliculi into which they drain, the nasolacrimal sac where the canaliculi meet, and the nasolacrimal duct proper which drains into the nasal passage in most animals. Exceptions to this include the rabbit and the pig, which possess a single punctum in the lower and upper eyelids. Although the majority of tears leave via the nasolacrimal system, 10 to 25% are lost through evaporation.174
Helen Whitwell, Christopher Milroy, Daniel du Plessis in Forensic Neuropathology, 2021
The orbit is a pyramidal, bony cavity in the face. It contains and protects the eye with its associated muscles, nerves and vessels and the lacrimal apparatus. The roof is formed by the orbital part of the frontal bone, separating the orbit from the anterior cranial fossa and containing a small fossa for the lacrimal gland. The lesser wing of the sphenoid contributes to the roof at its apex. The medial wall is formed by the thin bone of the ethmoid, frontal, lacrimal and sphenoid bones. It is indented by the fossa of the lacrimal sac and nasolacrimal duct. The lateral wall comprises the frontal process of the zygomatic bone and the greater wing of the sphenoid, and is vulnerable to direct trauma. It serves to separate the orbit from the temporal and middle cranial fossae. The floor is made up from the maxilla, zygomatic and palatine bones, with a thin inferior wall partly separated from the lateral wall by the inferior orbital fissure. At the apex of the orbit lies the optic canal, located medial to the superior orbital fissure, which carries the optic nerve and associated structures into the orbit.
The lacrimal apparatus consists of the following: Lacrimal punctum is located at the medial canthus – upper and lower canaliculi lead from it to the lacrimal sac, travelling beneath the upper and lower limbs of the medial canthal ligament.Lacrimal sac drains into the nasolacrimal duct, which empties into the inferior meatus of the lateral wall of the nose; the sac is pulled open during contraction of the palpebral fibres of orbicularis oculi and closes by elastic recoil. Valves in the canaliculi prevent reflux.
Stella Y. Chung, Leon Rafailov, Roger E. Turbin, Paul D. Langer
Dacryocystitis is the most common infection of the lacrimal apparatus, typically occurring as a result of nasolacrimal duct obstruction. While the pathogens that cause dacryocystitis are similar to those found in the upper respiratory tract and on the skin, recent studies suggest an increasing trend of rarer gram-negative bacteria and methicillin-resistant Staphylococcus aureus (MRSA) infections in both acute and chronic types of dacryocystitis. 1–6 In addition to the shifting trends within the microbiologic spectrum of dacryocystitis, a recent study reported that approximately one-third of bacterial isolates are resistant to initial oral antibiotic therapy.6 Another study reported a higher incidence of organisms, particularly the Pseudomonas species, which were resistant to commonly used antibiotics such as ampicillin, cephalexin, and cefuroxime.2
Zhenyang Zhao, Richard C. Allen
A quantitative evaluation for tear production is carried out by Schirmer’s test, which remains the gold standard for diagnosing alacrima. Schirmer I is performed without topical anesthetics and tests for both basal and reflex secretion. A result of less than 5 mm of wetting after 5 minutes on Schirmer I confirms alacrima. The basal secretion rate, which is tested by Schirmer II, is variable among alacrima cases possibly relating to the remaining function from accessory lacrimal glands. The use of Schirmer III test, which anaesthetizes the cornea with nasal stimulation, is occasionally reported, but is difficult due to lack of patient cooperation, especially in children.49 The phenol red thread test can be useful in pediatric patients, which is less invasive with a shorter testing time. However, a result of less than 5 mm after 15 seconds has high sensitivity but low specificity.69 Once alacrima is determined, a focused ophthalmic exam should be conducted to evaluate the lacrimal apparatus for lacrimal duct abnormalities, the pupillary reaction for tonic pupil or anisocoria, the ocular surface for associated complications and the fundus exam for retinopathy or optic neuropathy. An orbital ultrasound, CT or MRI could be performed to look for any anatomical or developmental anomaly of the lacrimal glands.
Lauge Hjorth Mikkelsen, Natacha Storm Würtz, Steffen Heegaard
The ocular adnexa (OA) consist of the eyelids, conjunctiva, lacrimal apparatus, and orbital soft tissue [1]. Ocular adnexal lymphoma (OAL) is a broad term encompassing all types of malignant lymphoproliferative diseases of the OA. Lymphoma is the most frequent malignancy of the OA and comprises 1–2% of all lymphomas and 5–10% of all extranodal lymphomas [2,3]. Lymphoma may be divided into Hodgkin- and non-Hodgkin lymphoma (NHL), the latter being by far the most frequent. NHL may be further subclassified according to the presumed cell of origin as defined by the World Health Organization (WHO) Classification of Tumors of Hematopoietic and Lymphoid Tissue [4]. In this review, we will not consider Hodgkin lymphoma of the OA, as it is exceedingly rare in this location.