Limbal dermoids are benign congenital tumors that contain choristomatous tissue (tissue not found normally at that site). They appear most frequently at the inferior temporal quadrant of the corneal limbus. However, they may occasionally present entirely within the cornea or may be confined to the conjunctiva.[1] They may contain a variety of histologically aberrant tissues, including epidermal appendages, connective tissue, skin, fat, sweat gland, lacrimal gland, muscle, teeth, cartilage, bone, vascular structures, and neurologic tissue, including the brain.[2, 3, 4] Malignant degeneration is extremely rare. See the image below.
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Limbal dermoid in the left eye of a 13-year-old male patient.
The most common system for classifying dermoids is based on the location of the lesion and separates the lesions into 3 broad categories. The most common dermoid is the limbal dermoid, in which the tumor straddles the limbus. Limbal dermoids are usually superficial lesions but may involve deeper ocular structures. The second type involves only the superficial cornea, sparing the limbus, the Descemet membrane, and the endothelium. The third type of dermoid involves the entire anterior segment, replacing the cornea with a dermolipoma that may involve the iris, the ciliary body, and the lens. Also see Dermoid, Orbital.
Several theories have been proposed to explain the development of limbal dermoids. One theory suggests an early developmental error resulting in metaplastic transformation of the mesoblast between the rim of the optic nerve and the surface ectoderm. Another proposed mechanism is sequestration of the pluripotential cells during embryonic development of the surrounding ocular structures. The exact pathogenesis probably varies from case to case.
Limbal dermoids generally are not inherited, although some exceptions have been reported. Familial presentation of limbal dermoids in association with systemic disorders, such as Goldenhar syndrome, is well recognized and follows a multifactorial pattern of inheritance.[5] Two rare forms of epibulbar dermoid (ie, the annular limbal form, the corneal dystrophy form) presenting in multiple family members have been reported.
The estimated worldwide incidence of limbal dermoids ranges from 1 case per 10,000 population to 3 cases per 10,000 population.
In a study at the Armed Forces Institute of Pathology, 7.5% of epibulbar lesions examined were choristomas. According to this study, 52% of epibulbar choristomas were located in the bulbar conjunctiva, 29% at the limbus, 6% on the cornea, 4% at the caruncle, and 2.5% in the conjunctival fornix or the palpebral conjunctiva.[6]
In a study of epibulbar choristomas in patients with Goldenhar syndrome, 14% were nasal, 86% were temporal, 16% were superior, and 84% were inferior.[5]
Mortality/Morbidity
Visual morbidity may result from encroachment of the lesion into the visual axis, development of astigmatism, or formation of a lipid infiltration of the cornea, which obstructs the visual axis.
Large limbal dermoids can be cosmetically disfiguring.
Staphyloma formation adjacent to dermoids has been reported and may be associated with spontaneous perforation of the cornea or the sclera.
Race
No racial predisposition exists.
Sex
Limbal dermoids occur with equal frequency in males and in females.
Age
Limbal dermoids are present at birth but may not be recognized until the first or second decade of life. They may also appear to enlarge as the body matures.
In a study conducted at the Armed Forces Institute of Pathology, 36% of epibulbar lesions removed in the first decade of life were choristomas. They constituted about 23% of epibulbar lesions removed in the second decade of life, 7.2% of lesions removed in the third decade, and 0.9% of lesions removed in the fourth decade.[6]
In another study conducted at the Wilmer Ophthalmologic Institute, epibulbar choristomas constituted 33% of epibulbar lesions removed before age 16 years and 2.2% of epibulbar lesions removed after age 16 years.
Prognosis is generally favorable. A scoring system for limbal dermoids has been proposed based on extent of corneal involvement, area of conjunctival involvement, and surface shape.[7] . This system may have prognostic value in predicting long-term visual acuity and helps to unify management planning.
Most epibulbar dermoids are located at the inferior temporal limbus.
Rarely, they may only affect the cornea or the bulbar conjunctiva.
Epibulbar dermoids have a dome shape, and the surface may appear keratinized.
Hair follicles and cilia may be visible.
The dermoid appears fleshy and may have fine superficial vascularization.
Associated ocular abnormalities include colobomata of the eyelids, Duane retraction syndrome and other ocular motility disorders, lacrimal anomalies, scleral and corneal staphylomata, aniridia, and microphthalmia.
Associated systemic abnormalities include preauricular appendages and auricular fistulae (in combination with limbal dermoids constituting Goldenhar syndrome). Other abnormalities include hemifacial microsomia, microtia, and vertebral anomalies.
The acronym SCALP syndrome is used to describe individuals with the constellation of clinical findings including nevus sebaceous, central nervous system malformations, aplasia cutis congenital, limbal dermoid, and pigmented nevus. Three cases have been described in the literature.[8]
Some dermoids may appear to extend into the conjunctival fornix or lateral canthus. These lesions may contain connective tissue that entangles with the orbital fat and muscle tissue belonging to the extraocular muscles.
Radiologic imaging with an MRI can be useful in identifying such lesions, especially if surgical management is being considered.
Limbal dermoids contain choristomatous tissue, including epidermal appendages, adipose and lachrymal gland tissue, smooth and striated muscle, cartilage, brain, teeth, and bone. Lymphoid nodules and vascular elements also have been reported. Immunohistochemical studies have demonstrated that limbal dermoids share antigenic expression with the basal limbal epithelium and the stem cell niche of normal human hair follicles.[9] The surface of the dermoids consists of corneal or conjunctival epithelium. The lesion may be cystic or solid. Note the histological image below.
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Histopathological section demonstrating a pilosebaceous unit.
Treatment of limbal dermoids may consist of periodic removal of irritating cilia, topical lubrication to prevent foreign body sensation, or excision of the lesion if it is causing significant cosmetic disfigurement or interfering with vision.
Surgical treatment should be instituted only when the risk of subsequent scar formation or surgical complications are outweighed by the likelihood of improving the patient's vision or cosmetic appearance.
A superficial sclerokeratectomy, cutting flush with the surface of the globe, is the procedure of choice for removal of the dermoid. Excised tissue always should be sent to the pathologist for examination.
Attempts at complete removal are unnecessary. The lesion may extend into the deeper structures of the eye and the risk of perforation increases if attempts are made to remove the lesion completely.
The exposed sclera should be covered by relaxing the adjacent conjunctiva and sewing it into the scleral defect. If a deep excision is necessary, then a lamellar keratoplasty can be performed to reinforce the site of excision.
Large patches of bare sclera can be treated with application of single or multilayered amniotic membrane graft tissue. The amniotic membrane can be secured to underlying sclera using sutures and/or fibrin-glue adhesive.[10]
Mark D Sherman, MD, Assistant Clinical Professor, Department of Ophthalmology, Loma Linda University School of Medicine; Private Practice, Pacific Eye Surgeons
Disclosure: Nothing to disclose.
Specialty Editors
Simon K Law, MD, PharmD, Clinical Professor of Health Sciences, Department of Ophthalmology, Jules Stein Eye Institute, University of California, Los Angeles, David Geffen School of Medicine
Disclosure: Nothing to disclose.
J James Rowsey, MD, Former Director of Corneal Services, St Luke's Cataract and Laser Institute
Disclosure: Nothing to disclose.
Chief Editor
Hampton Roy, Sr, MD, Associate Clinical Professor, Department of Ophthalmology, University of Arkansas for Medical Sciences
Disclosure: Nothing to disclose.
Additional Contributors
Andrew W Lawton, MD, Neuro-Ophthalmology, Ochsner Health Services
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