Corneal Dermoids: All You Need to Know

What’s that lump on my eye? Before you panic, perhaps you should consider the possibility that it is a corneal dermoid, a relatively common benign cyst that is both easy to remove and mostly harmless if treated in a timely manner by an ophthalmology professional.

Corneal dermoids are among the most often-seen kinds of ocular choristoma. An ocular choristoma is what ophthalmologists and other clinicians use to refer to a mass of tissue that is in the wrong place. These so-called tumors, benign in nature, often present as a yellowish or whitish mass on the anterior surface of the eyeball and cornea.

In the case of these dermoids, the wrong place that this cyst or benign tumor is in is specifically on the anterior segment of the eye; it really shouldn’t be on the eye at all. The name dermoid gives a pretty big hint about where these abnormalities on the cornea actually come from. Histopathological analysis on these ocular dermoids shows they are composed of elements of the skin, or dermis. They contain ectodermal elements, keratinized epithelium, hair follicles, sebaceous and sweat glands, nerves, smooth muscles and, even more rarely, teeth. They also contain mesodermal elements like fibrous tissue, fat, blood vessels and cartilage

Corneal dermoids are some serious-looking solid mass lesions, but are generally considered to be benign. There are many things that may go through your mind when you discover a lump on the anterior segment of your eye, but don’t fret before your ophthalmologist appointment. In the following article, you will learn about the types of corneal dermoid that exist and the names they go by, as well as possible causes, symptoms, and treatments.

Types of Corneal Dermoids

There are many names for the many types of dermoids that can appear on the corneal surface, and every doctor is different in the nomenclature they use for these.

One of the more common names you might sometimes hear from an ophthalmology professional for corneal dermoids are limbal dermoids. Limbal dermoids are so named for their position on the limbus region, which is what ophthalmologists call the junction between the cornea and sclera. The limbus, which is the area where the epithelium thickens at the junction between the cornea and conjunctiva, is an extremely important region of the eye, as it contains limbal stem cells, and is thus a common area for conjunctival and various types of other tissue to accumulate.

Another type, or rather another commonly heard term for corneal dermoids is epibulbar dermoid. Don’t let this confuse you, though — this is just another name for a limbal dermoid that occurs at a particular place on the conjunctiva, in the inferotemporal quadrant of the limbus. For more information on epibulbar dermoids, check out this case report on epibulbar dermoids in younger patients (age 9-months to 6-years-old) for interesting information on how these types of dermoids are diagnosed and treated.

One final and commonly used term for dermoids in general, and specifically ocular and corneal dermoids, is lipodermoid. This is just a kind of dermoid composed mainly of fat cells, instead of the usual stuff like skin and hair follicles. Now that we’ve established the different types of corneal dermoids and the names that refer to them, let’s move on to potential causes.

Corneal and limbal dermoids are usually assigned a grade. The modern grading system assigned comes from a 2018 retrospective study by Zhong et al. Dermoids are graded on a scale of I-III, from a composite score of corneal involvement, conjunctival involvement, and surface shape. Grade I dermoids are smaller and involve very little of the cornea and conjunctiva, and are small and regular in shape; grade III dermoids involve large and irregular swathes of the cornea, conjunctiva, and many structures of the anterior chamber and corneal stroma.

What Causes Corneal Dermoids?

Corneal dermoids are an ocular abnormality that can appear at any age or at any stage in life, from children to adults. They can appear in the left eye or the right eye and in a variety of positions on the cornea, as outlined in the section above. Pediatric cases across a variety of ages are more common for most types of dermoids, such as in this case report of a 25 day-old infant with otherwise normal ocular health. They can appear in adults as well, but are far less common.

So now that we’ve established that corneal dermoids can appear in almost any patient, the question remains of why they appear. The answer to this question is not simple; most ophthalmologists have no idea where the vast majority of these ocular dermoids come from.

However, an article by the Columbia University Department of Ophthalmology shines some light on some potential pathological causes.

The first potential cause listed is oculoauriculovertebral dysplasia, which is also known as Goldenhar syndrome. Goldenhar syndrome is a congenital disorder with prevalence between 1:3500 – 1:7000 live births and comes with a variety of ocular, cardiac, skeletal and central nervous system complications. Epibulbar dermoids are a signature of this disease, so if you have epibulbar dermoids this might be a potential avenue of exploration.

Another disease that ocular dermoids are found in is Duane Retraction Syndrome, a congenital strabismus syndrome that leads more commonly to epibulbar dermoids. Other symptoms of Duane Retraction Syndrome outside of strabismus are head tilting. Patients with Duane Retraction Syndrome normally have good visual acuity, except when the disease is accompanied by amblyopia, which is quite rare.

Other potential causes of these dermoids are coloboma (extra thickness) of the upper lid, and lacrimal stenosis, which is just a narrowing of the tear duct. Next, we’ll take a look at some of the symptoms that can result from these types of tumors.

Symptoms and Complications

The most obvious symptom is the cyst or lesion itself — a yellowish or whitish mass on the anterior surface of the eye. Corneal dermoids are by nature benign cysts and are rarely life-threatening, but they can cause some nasty complications.

Aside from the obvious aesthetic concerns like redness, the most common complications arise when the tumor gets too large and impedes eyesight, leading to lower visual acuity. Astigmatism is the most common symptom as the tumor warps the shape of the corneal surface, which may also lead to amblyopia. If you find that a mass on your eye is getting large and may be affecting your vision, it might be time to follow up with an ophthalmologist to see what your options are.

Treatment and Management

Treatment options for these benign cysts vary and depend mostly on the size and grade of the tumor.

The most common type of intervention is surgical and involves an excision of the tumor in which the mass is removed from the surface of the eye. In their 2014 article, Lang et al. describe various types of surgical procedures and techniques used for the removal of corneal dermoids. These include bare excision, amniotic membrane transplantation, and sometimes penetrating and lamellar keratoplasty. The treatment depends on the lesion itself — how large it is, the grade it is, and how it affects visual acuity.

The good news is that most surgeries that excise the tumor do not result in complications, though they all do have their risks like perforation, infection, epithelial defects and recurrence. A skilled surgeon and postoperative treatments like Mitomycin-C can help ensure that this relatively routine procedure goes smoothly.

At the end of the day it is always best to book an appointment with your doctor if you suspect that you might have an ocular or corneal dermoid. Proper diagnosis and treatment is key to prevent complications like loss of visual acuity, so it’s best not to wait.

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