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What Is Trichiasis and
How Can It Produce Eyelid Spasms?
Wade D. Brock, M.D.
Lanning B. Kline, M.D.
Department of Ophthalmology
University of Alabama at Birmingham
Trichiasis is the misdirection of eyelashes against the eyeball. We frequently see patients with trichiasis in our office as ophthalmologists. It is appreciated less frequently in offices outside of our specialty. Patients with normal corneal sensation will report feeling as if something has gotten into their eye or that something is "sticking" their eye. Usually, it is difficult for the patient to recall exactly when these symptoms started because they are frequently intermittent before they become down right irritating. Occasionally, people will report that their problems began after facial trauma, ocular surgery, or an eye infection.
To better understand trichiasis and how it relates to blepharospasm, it is helpful to be familiar with: 1) the anatomy of the eyelid; 2) the mechanism of the normal blink reflex.
First, let's cover the anatomy. The lid margin can be thought of as a flat platform. The part of the eyelid against the eyeball is covered by conjunctiva. If you look in a mirror and pull your lower eyelid down toward your cheek with your finger, the conjunctiva is the pink tissue you see beneath your eyeball on the inner aspect of the eyelid. Anterior to (i.e. in front of) the conjunctiva is the skin. The line at which the skin and conjunctiva meet is referred to as the mucocutaneous junction. Directly in front of the mucocutaneous junction are the openings of the meibomian glands, and anterior to this is a "gray line". Your eyelashes will normally arise just in front of the gray line.
Now let's go over the mechanism of blinking: Blinking can be triggered by stimulation of the eyelid, eyelashes, cornea or conjunctiva. Each of these areas has sensory nerve receptors to detect touch. These receptors take the message of touch to nerve bodies located in the trigeminal ganglion at the base of the brain. The message is then relayed to motor nerve bodies in the brain stem. The motor nerves take the message of touch to the muscles that cause the eyelid to close.
So now that you know about the normal eyelid, you may be wondering how things go wrong. How do people get trichiasis? There are several reasons trichiasis occurs, but the most common causes in the general population are involutional (age-related) or scarring.
Sometimes trichiasis occurs because aging brings about changes in the eyelid anatomy. This condition is known as involutional entropion. Entropion means that your eyelid margin rolls in toward your eyeball. You can imagine how this could cause trichiasis. Rarely this constant irritation may result in ulceration of the cornea.
Another common cause of trichiasis is scarring of the skin or conjunctiva. Trauma that results in laceration to the eyelid may lead to scarring and misdirection of eyelashes. Another cause of scarring can be a number of autoimmune diseases that target the conjunctiva or inner aspect of the eyelid. Trichiasis results from scarring of the eyelid in one of two ways. As scarring occurs, the eyelid may tend to shorten and roll in toward the eyeball. In other cases there is aberrant growth of eyelashes from an abnormal location of the eyelid.
It is important to know whether or not you have trichiasis before receiving botulinum toxin, because in this case, botox will not completely solve the problem. You see, botox blocks the motor response of the blink reflex. But if there are lashes touching your cornea, and the sensory pathway of the reflex is still intact, the induced blinking may override the botox effect. So if botox is not the answer, you might ask, "What is the solution for trichiasis?" It really depends on the cause.
In the best case scenario there will be a single lash touching the eyeball. There will not be major scarring nor will there be significant entropion. The lash can simply be plucked out with a pair of forceps by your ophthalmologist. More frequently, there are several lashes touching the eye. These can also be removed with forceps. Unfortunately, one can expect lashes to grow back to an irritating length in 3 to 5 weeks. If this continues to occur, a second option is to remove a full thickness section of the eyelid or to perform cryotherapy.
Full thickness wedge resection is useful when less than about one third of the lid is involved and is frequently the choice for repair when the skin of the eyelid is scarred. Local anesthetic injection to the eyelid is required. This is followed by removing a full thickness pentagonal wedge of eyelid. The two cut ends of the eyelid are then carefully reapproximated with suture to recreate a smooth lid margin platform without any aberrant lashes.
Cryotherapy is the actual freezing of the affected eyelid. Local anesthetic injection to the eyelid will be necessary. This is followed by freezing the eyelid where the lashes are troublesome. Routinely, this area is frozen twice, over a period of 30 seconds each. The lashes are then removed with forceps and hopefully will not grow back. It should be mentioned that full thickness resection and cryotherapy must be used cautiously in patients with autoimmune diseases that target the conjunctiva, because disrupting the tissue with surgery may make the scarring worse.
Finally, if the cause of trichiasis is due to involutional entropion, a larger surgery is required. This is frequently performed in an operating room under local anesthetic. A description of this procedure is really beyond the scope of this article. An ophthalmologist or ophthalmic plastic surgeon can recognize if this surgery is necessary.
There can be no doubt that the advent of botulinum toxin has significantly improved our treatment of benign essential blepharospasm. For thousands of patients it has brought a great deal of improvement in their lives. If you are a patient who has experienced the benefits, you understand this better than anyone. While you may continue your treatment with a qualified specialist, we encourage you to have a complete eye examination. This will exclude other ocular or eyelid factors such as trichiasis that may be contributing to your blepharospasm.
Originally published in Benign Essential Blepharospasm Research Foundation Newsletter, Volume 22, Number 3, page 10 (2003)
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