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Dermoid Cyst

What is a dermoid?

A dermoid is an overgrowth of normal, non-cancerous tissue in an abnormal location. Dermoids occur all over the body. The ones in and around the eye are usually comprised of skin structures and fat [See figure 1].

Where are dermoids found around the eyes?

There are two main dermoid types that occur on or around the eyes. An orbital dermoid is typically found in association with the bones of the eye socket. A epibulbar dermoid is found on the surface of the eye, either at the junction of the cornea and sclera (limbal epibullar dermoid) or more posteriorly on the eye where the conjunctiva that covers the eye meets the conjunctiva that covers the lid (posterior epibulbar dermoid or lipodermoid).

What does an orbital dermoid look like?

An orbital dermoid presents as an egg-shaped mass under the skin adjacent to the bones of the eye socket. The mass is soft. The skin overlying the mass is normal in appearance. Dermoids can remodel the bone adjacent to them so that they often sit in a depression in the bone. Sometimes dermoids are dumbbell-shaped with one half of the mass on the outer part of the rim of the eye socket and the other part in the inside of the rim of the eye socket. Dermoids are cysts and are typically filled with a greasy material that is yellow in color.

Fig. 1 A dermoid is an overgrowth of normal, non-cancerous tissue in an abnormal location.

Where are orbital dermoids usually found?

Orbital dermoids usually form anteriorly in the eye socket where two of the facial bones that form the eye socket touch each other. The most common place for dermoids to occur is in the upper and outer part of the eye socket near the end of the eyebrow. They can also occur adjacent to the nose but are rarely found in association with the bones in the lower part of the eye socket. Rarely orbital dermoids are found more posteriorly in the eye socket.

Do orbital dermoids need to be removed?

Because there is a small risk that orbital dermoids can rupture and cause an inflammatory reaction, it is usually recommended that they be removed.

How are orbital dermoids removed?

The skin overlying the dermoid is opened and the surrounding tissues are dissected until the dermoid is revealed. The dermoid is then carefully dissected free from the surrounding tissue. The excised mass is typically sent to a pathologist who can confirm the identity of the tissue.

Do orbital dermoids cause vision loss?

Not usually.

Are orbital dermoids found in association with other diseases?

No.

What does a posterior epibulbar dermoid or lipodermoid look like?

A posterior epibulbar dermoid is typically yellow in color and soft in consistency, molding to the curve of the eye. The conjunctiva overlying it may be thickened. Occasionally there is one or more hairs sticking out from the mass.

Fig. 2 Posterior epibulbar dermoid.

Where are posterior epibulbar dermoids usually found?

Posterior epibulbar dermoids are usually found under the outer upper eyelid in the recess where the eyeball meets the eyelid [See figure 1]. Depending on their size, they may be visible only when the upper lid is lifted or if larger they may be seen with the eyelids in the usual position.

Do posterior epibulbar dermoids need to be removed?

Not always. If they are small and not bothersome to the patient or patient?s family, posterior epibulbar dermoids can be left alone.

How are epibulbar dermoids removed?

Posterior epibulbar dermoids are usually not attached to the eyeball itself. They are attached to the conjunctiva that covers the eye. They often extend posteriorly into the eye socket and usually cannot be entirely removed. Excision involves stripping the dermoid free of the overlying conjuctiva, clamping the mass at the most posterior extent of the dissection and removing the anterior part of the mass. The excised mass is typically sent to a pathologist who can confirm the identity of the tissue.

Do posterior epibulbar dermoids cause vision loss?

Not usually.

Are posterior epibulbar dermoids associated with other diseases?

Yes, sometimes. They can be found in persons with Goldenhar syndrome, linear nevus sebaceous syndrome, and encephalocraniocutaneous lipomatosis.

What does a limbal epibulbar dermoid look like?

A limbal dermoid is a yellowish-white, firm round elevated mass attached to the eyeball. The mass can be comprised of fat, hair follicles and fat glands. Sometimes there is one or more hairs sticking out from the mass [See figure 3].

Fig. 3 Limbal epibulbar dermoid.

Where are limbal dermoids usually found?

They are found on the surface of the eye one the cornea or at the junction of the cornea and sclera.

Do limbal epibulbar dermoids need to be removed?

Usually. Because they can cause eye irritation and because the appearance is abnormal, epibulbar dermoids are usually removed.

How are limbal epibulbar dermoids removed?

The dermoids are cut flush with the surface of the eye. Sometimes the dermoid extends into the sclera and/or the cornea and care must be taken to avoid entering the eye when excising them. After excision, the site where the dermoid lay can be covered by a piece of transplanted cornea.

Do limbal dermoids cause vision loss?

Often. Occassionally the dermoid is so large that it blocks visual input from entering the eye. More often however, the vision loss occurs because the presence of the dermoid causes the cornea of the affected eye to have an irregular shape. This warping of the cornea can cause a large amount of astigmatism and a blurred image. The blurred image encourages the developing brain to ignore the input from the affected eye, thus causing vision loss through amblyopia. Forutunately, amblyopia if detected during childhood can often be successfully treated (amblyopia).

Does the risk of vision loss go away after the dermoid is removed?

Usually not. Even though the dermoid is gone, the warpage it causes in the cornea remains and the risk of amblyopia developing remains.

Are limbal dermoids associated with other diseases?

Yes, sometimes. They can be found in persons with Goldenhar syndrome, linear nevus sebaceous syndrome, and encephalocraniocutaneous lipomatosis.