Lacrimal Gland – Function, Anatomy and Diseases
The lacrimal gland is an exocrine gland that produces tear fluid, keeping the surface of the eye moist, nourished, and protected.
Things worth knowing about "Lacrimal Gland"
The lacrimal gland is an exocrine gland that produces tear fluid, keeping the surface of the eye moist, nourished, and protected.
What is the Lacrimal Gland?
The lacrimal gland (Latin: Glandula lacrimalis) is an exocrine gland located in the upper outer region of the eye socket (orbit). Its primary function is to produce the aqueous component of tear fluid, which keeps the surface of the eye and conjunctiva moist, nourished, and protected. The lacrimal gland is part of the lacrimal apparatus, which also includes the drainage pathways through which tear fluid is channelled away from the eye.
Anatomy and Structure
The lacrimal gland is paired, meaning one gland is present in each eye. It lies beneath the bone of the frontal skull (fossa glandulae lacrimalis) in the upper outer orbit and is divided into two lobes by the levator palpebrae superioris muscle:
- Orbital lobe (Pars orbitalis): The larger, upper portion situated deep within the orbit.
- Palpebral lobe (Pars palpebralis): The smaller, lower portion located within the upper eyelid, visible when the eyelid is everted.
Approximately 10 to 12 fine ducts open into the upper conjunctival fornix, delivering tear fluid onto the surface of the eye.
Function of the Lacrimal Gland
The lacrimal gland continuously produces a small amount of basal tear fluid to keep the ocular surface moist. In response to irritation or emotional stimuli, tear production can increase significantly (reflex tears or emotional tears). Tear fluid serves several important purposes:
- Lubrication: Prevents drying of the cornea and conjunctiva.
- Nourishment: Supplies the avascular cornea with oxygen and nutrients.
- Protection: Contains antibacterial substances such as lysozyme, immunoglobulins, and lactoferrin, which defend the eye against infection.
- Optical clarity: Maintains a smooth corneal surface for clear vision.
Diseases of the Lacrimal Gland
Dacryoadenitis
Dacryoadenitis is an inflammation of the lacrimal gland. It may be acute (e.g., caused by viruses such as mumps or Epstein-Barr virus) or chronic (e.g., associated with autoimmune conditions such as Sjogren syndrome). Symptoms include swelling, redness, and pain in the outer upper eyelid area.
Sjogren Syndrome
Sjogren syndrome is an autoimmune condition in which the immune system attacks the lacrimal and salivary glands, leading to chronically dry eyes (keratoconjunctivitis sicca) and dry mouth. It predominantly affects middle-aged women and may occur in isolation or alongside other autoimmune diseases.
Tumors of the Lacrimal Gland
Tumors of the lacrimal gland are rare but can be either benign (e.g., pleomorphic adenoma) or malignant (e.g., adenoid cystic carcinoma). They typically present as a slowly progressive swelling in the outer upper eyelid and require thorough diagnostic evaluation including imaging and tissue biopsy.
Dry Eye Syndrome
Reduced function of the lacrimal gland can lead to dry eye syndrome, medically termed keratoconjunctivitis sicca. Affected individuals experience burning, a foreign body sensation, redness, and blurred vision. Causes include age-related changes, hormonal influences, certain medications, and autoimmune diseases.
Diagnosis
Several diagnostic methods are used to assess the lacrimal gland and its function:
- Slit-lamp examination: Detailed inspection of the ocular surface and eyelids.
- Schirmer test: Measurement of tear production using a strip of filter paper placed under the lower eyelid.
- Imaging (CT or MRI): Cross-sectional imaging of the orbit to identify tumors or inflammation of the lacrimal gland.
- Biopsy: Tissue sampling when a tumor or systemic disease is suspected.
Treatment
Treatment of lacrimal gland disorders depends on the underlying cause:
- Inflammation: Antiviral or antibiotic therapy for infectious causes; corticosteroids for inflammatory or autoimmune conditions.
- Dry eye syndrome: Lubricating eye drops (artificial tears), punctal occlusion, or in severe cases immunosuppressive eye drops (e.g., cyclosporine A).
- Tumors: Surgical removal, with radiotherapy or chemotherapy added depending on the nature and extent of the tumor.
References
- Remington, L. A. - Clinical Anatomy and Physiology of the Visual System. 3rd edition, Butterworth-Heinemann, 2012.
- Drake, R. L.; Vogl, A. W.; Mitchell, A. W. M. - Gray's Anatomy for Students. 4th edition, Elsevier, 2019.
- Baum, J. L. - The Lacrimal Gland. In: Albert & Jakobiec's Principles and Practice of Ophthalmology. 3rd edition, Saunders Elsevier, 2008.
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