The lacrimal caruncle is a small, soft, pink nodule situated at the inner corner of the eye, a spot known anatomically as the medial canthus. This structure maintains the health and comfort of the ocular surface. Understanding the caruncle’s anatomy helps explain common occurrences, such as the crusting that appears after sleep.
Defining the Caruncle and its Location
The caruncle, formally known as the caruncula lacrimalis, is nestled within the lacus lacrimalis (tear lake) at the nasal side of the eye, where tears collect before drainage. Unlike the surrounding clear conjunctiva, the caruncle is specialized tissue containing elements typically associated with skin. This composition includes sebaceous glands, sweat glands, and fine hairs that sometimes protrude from its surface. The caruncle sits next to the plica semilunaris, a small crescent-shaped fold of conjunctiva.
The Physiological Role of the Caruncle
The primary function of the caruncle is directly related to the secretions produced by its specialized glands. The sebaceous (oil) and sweat glands within the tissue contribute oil and mucus to the tear film. This oily mixture stabilizes the outermost layer of the tear film, slowing tear evaporation and keeping the eye moist. The secretions also collect and trap tiny particles and debris that enter the eye. By gathering this foreign matter at the inner corner, the caruncle assists in keeping the ocular surface clear and supports waste removal.
Common, Temporary Changes in Appearance
Because the caruncle is exposed and constantly secreting, it is often the site of minor, temporary changes. Mild redness (hyperemia) or slight puffiness (edema) can occur due to temporary irritation or environmental factors like dust or wind. These changes are frequently observed during allergy season, where histamine release can cause the caruncle and adjacent plica semilunaris to become inflamed and itchy. The accumulation of white or yellowish crusting, often called “sleep” or rheum, appears after waking. This discharge is a collection of the caruncle’s normal secretions—oils and mucus—mixed with dust and sloughed-off skin cells swept to the inner corner during sleep. Pigmentation variations are also normal, as the caruncle can contain melanocytes, leading to small, benign brown spots or nevi.
Specific Medical Conditions
While the caruncle is susceptible to specific medical conditions, Carunculitis refers to the inflammation or infection of the caruncle tissue itself, causing persistent swelling, redness, and tenderness beyond simple allergic irritation. This condition often involves the blockage or infection of the internal oil and sweat glands. Another common issue is the formation of caruncular cysts, which are small, benign retention cysts resulting from a blocked glandular duct. These cysts appear as small, raised bumps on the surface. Lesions and tumors, though rare, can also arise, including benign growths like papillomas or nevi, and malignant tumors. Persistent swelling, pain, a change in size or color of a lesion, or discharge that does not resolve should prompt a consultation with an eye care professional.