What causes distichiasis, also known as double eyelashes?

Distichiasis (pronounced dis-tic-KAI-asis) is an uncommon condition that results in two rows of eyelashes. The rows may be complete rows, a few extra lashes or a single lash growing next to another. Distichiasis can cause a range of symptoms from minor discomfort to extreme problems.

These eyelashes grow from the eyelid’s inner lining instead of along the eyelid’s edge like normal eyelashes . This can cause the abnormal eyelashes to touch the eyeball. This growth can cause damage to the cornea and cause related eye problems that require medical attention.

Distichiasis can be congenital (meaning present at birth) or acquired later in life. It is more common to acquire this condition later in life. Those with congenital distichiasis may tolerate symptoms well and avoid diagnosis until age 5 or older. Acquired distichiasis may be caused by chronic irritation at the site of the eyelashes, severe inflammation of the eyelid or a chemical injury to the eyes.

Your eye specialist can diagnose the condition during a comprehensive eye exam using a slit-lamp .

Are there differences between normal eyelashes and those that grow as a result of distichiasis? In some cases, the lashes are full and very similar to the normal-growth lashes. But most often, they are thinner than normal lashes. While they typically grow inward toward the eye, they are also usually softer and shorter. This allows many patients with congenital distichiasis to live without symptoms until around 5 years of age. Elizabeth Taylor is a famous example of someone who was known for her eyes. Not only did she have violet eyes , she had an amazing set of lashes.

Cari Nierenberg writes in her NBC News health article , “It's hard to imagine that some of the first words heard by the parents of Elizabeth Taylor, the actress considered the world's most beautiful woman in her heyday, was that their newborn daughter had a mutation.”

You guessed it, Taylor had twice as many eyelashes as most of the actresses of her day. In her case, it played to her advantage later in life. While she was one of the lucky ones who enjoyed benefits to her twin set of lashes, the medical condition we now know as distichiasis isn’t so nice for some people.

Not everyone with the condition is as lucky as Elizabeth Taylor. Some experience minor discomfort, while others experience complications and symptoms requiring professional eye care.

Some people with distichiasis may not have symptoms at all. However, depending on several factors, including how the additional lashes may rub against the cornea , symptoms may include:

• Light sensitivity (called photophobia )

• Eye redness

• A gritty feeling known as foreign body sensation

• Soreness, inflammation or injury to the cornea

• Tender eyelid bumps called styes

SEE RELATED: Epiblepharon

Lymphedema distichiasis syndrome (LDS) is almost always associated with congenital distichiasis.

LDS affects the transport of fluid throughout the body in such a way that it can cause swelling or puffiness in a person's arms, hands, fingers, legs, feet and toes (the extremities).

Normally, the lymphatic system makes and moves immune cells and fluids around the body. When working properly, your body’s lymphatic system maintains proper fluid levels, absorbs fats, produces white blood cells that help your body’s immune response and removes waste and abnormal cells.

More simply stated, your lymphatic system is all about the transport of fluid throughout the body, and LDS interrupts that system. It can result in several complications, including:

• Swelling of the extremities

• Entropion

• Ptosis

• Cleft lip and palate

• Webbed neck

• Vertebral anomalies

• Congenital heart defects

Another symptom of LDS is, of course, distichiasis.

According to the U.S. National Library of Medicine , all people with LDS have their extra eyelashes when they are born. The age at which LDS presents varies, but it most often happens during puberty.

Patients without symptoms usually do not need treatment. If you’re experiencing symptoms, you can seek treatment with your eye doctor . The symptoms and risks of your specific condition will determine the type of treatment your specialist will recommend. Options may include:

Non-surgical treatments

• Eye drops or ointments to relieve some symptoms.

• Soft contact lenses to provide a barrier between the cornea and the eyelashes.

Surgical treatments

• Epilation (plucking — at your eye doctor's office) may be helpful for those with only a few extra lashes.

• Cryosurgery may be effective for those with a larger number of lashes by freezing the lash follicles to destroy them.

• Radiofrequency (RF) ablation can provide relief by destroying lash follicles using a very small wire to apply RF to the root.

• Lid splitting surgery may be used in extreme cases and involves an incision near the lashes to treat them directly.

If distichiasis is causing symptoms and is left untreated, the cornea could be at risk of scarring, thinning or ulceration .

Humans aren’t the only ones who can have this condition. Dogs can experience distichiasis as well. Symptoms of distichiasis in dogs are typically similar to those in humans. However, since our k9 friends can’t speak like us, here are a few things to watch out for in your friend’s behavior:

• Eye redness

• Squinting

• Discharge and rubbing

• Signs of a corneal ulcer

• Swollen eye(s)

Distichiasis in dogs is recognized as a hereditary trait in certain breeds, including the more commonly affected breeds:

• American Cocker Spaniel

• Cavalier King Charles Spaniel

• Shih Tzu

• Lhasa Apso

• Dachshund

• Shetland Sheepdog

• Golden Retriever

• Chesapeake Retriever

• Bulldog

• Boston Terrier

• Pug

• Boxer Dog

• Pekingese

Like with their human counterparts, an eye exam is necessary to diagnose the condition in dogs. Treatments may include similar non-surgical and surgical options as for humans.

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