Lacrimal caruncle

The lacrimal caruncle is a small, pinkish structure located at the medial canthus of the eye. Although often overlooked, it plays a role in ocular surface health and may be involved in various clinical conditions. Understanding its anatomy and microscopic structure is essential for both clinicians and anatomists.

Anatomy of the Lacrimal Caruncle

Location and Boundaries

The lacrimal caruncle is situated in the medial canthus of the eye, adjacent to the plica semilunaris. It lies at the junction where the upper and lower eyelids meet and is closely associated with the lacrimal puncta and the conjunctival sac. Its boundaries are defined by the surrounding conjunctiva, the medial canthal tendon, and the adjacent ocular skin.

Gross Morphology

• Size and Shape: Typically small and rounded, measuring a few millimeters in diameter.
• Surface Features: The surface may appear smooth or slightly lobulated, with fine folds of conjunctival tissue.
• Color and Texture: Pinkish in color due to the vascular supply and slightly elevated compared to the surrounding conjunctiva.

Microscopic Structure

• Epithelium: Covered by non-keratinized stratified squamous epithelium similar to the conjunctiva.
• Glands: Contains sebaceous and sweat glands, contributing to the lubrication of the ocular surface.
• Accessory Structures: Hair follicles may be present, along with connective tissue and a rich vascular network.

Embryology

The lacrimal caruncle develops from the ectodermal tissue of the medial canthus during early embryogenesis. It forms as a distinct structure by the second trimester and continues to mature postnatally. Variations in development can result in accessory lacrimal tissue or minor congenital anomalies, though these are uncommon.

Physiology and Function

The lacrimal caruncle contributes to the maintenance of a healthy ocular surface through several physiological roles. Although its functions are less prominent than the main lacrimal glands, it aids in ocular lubrication and immune defense.

• Lacrimal Secretion Contribution: The sebaceous and sweat glands within the caruncle secrete oils and mucous that help stabilize the tear film and prevent evaporation.
• Ocular Surface Protection: By secreting protective substances and trapping debris, the caruncle assists in maintaining the integrity of the conjunctiva and cornea.
• Immune Defense Mechanisms: The caruncle contains lymphoid tissue that can respond to pathogens, contributing to localized immune defense against ocular infections.

Clinical Significance

Common Conditions

• Lacrimal Caruncle Cysts: Benign cystic lesions can develop due to obstruction of sebaceous or sweat gland ducts.
• Tumors: Both benign (such as papillomas) and malignant (such as basal cell carcinoma) tumors can arise in the caruncle, though malignancies are rare.
• Inflammatory Conditions: Carunculitis involves inflammation, often presenting with redness, swelling, or discomfort in the medial canthus.

Diagnostic Considerations

• Clinical Examination: Inspection with slit-lamp microscopy helps assess lesions, vascularity, and surface changes.
• Imaging: High-resolution imaging may be required for deeper lesions or suspected malignancies.
• Histopathology: Biopsy and microscopic evaluation are essential for definitive diagnosis, particularly for neoplastic or persistent lesions.

Surgical and Therapeutic Management

Management of lacrimal caruncle conditions depends on the nature and severity of the lesion. Both conservative and surgical approaches are utilized based on clinical findings.

• Excision Procedures: Surgical removal is indicated for cysts, papillomas, or suspicious masses. Careful dissection is required to preserve surrounding ocular structures.
• Medical Management: Topical antibiotics or anti-inflammatory medications may be used for mild infections or inflammation.
• Postoperative Care: Includes monitoring for infection, controlling inflammation, and ensuring proper healing to prevent recurrence or scarring.

Variations and Anomalies

The lacrimal caruncle exhibits some anatomical and developmental variations, which can be clinically significant or purely incidental findings.

• Congenital Variations: Some individuals may have accessory lacrimal tissue or minor structural differences present from birth.
• Accessory Lacrimal Caruncle Tissue: Rarely, extra tissue may be located near the medial canthus, potentially causing cosmetic concerns or irritation.
• Age-Related Changes: With aging, the caruncle may undergo slight enlargement, pigmentation changes, or decreased glandular activity, influencing tear film stability.

References

1. Gray H, Standring S. Gray’s Anatomy: The Anatomical Basis of Clinical Practice. 42nd ed. London: Elsevier; 2020.
2. Bron AJ, Tripathi RC, Tripathi BJ. Wolff’s Anatomy of the Eye and Orbit. 9th ed. London: CRC Press; 2017.
3. Kanski JJ, Bowling B. Clinical Ophthalmology: A Systematic Approach. 9th ed. Elsevier; 2020.
4. Rohen JW, Yokochi C, Lutjen-Drecoll E. Color Atlas of Anatomy: A Photographic Study of the Human Body. 8th ed. Wolters Kluwer; 2021.
5. Olver JM, Goss DA. Ocular Surface and Tear Film. In: Albert DM, Jakobiec FA, eds. Principles and Practice of Ophthalmology. 4th ed. Elsevier; 2020: 215–230.
6. Shields JA, Shields CL. Eyelid, Conjunctival, and Orbital Tumors: An Atlas and Text. 2nd ed. Lippincott Williams & Wilkins; 2016.
7. Jordan DR. Anatomy and Pathophysiology of the Lacrimal System. Curr Opin Ophthalmol. 2018;29(5):428–434.