What is a distichia (rarely spelled as dystichia)?
A distichia (plural distichiae) is an eyelash that arises from an abnormal location on the eyelid or grows in an abnormal direction. Distichiae usually emerge along the margin of the eyelid through the duct or opening of the meibomian gland, although they may arise at other locations along the eyelid margins. The condition in which these abnormal eyelashes are found is called distichiasis.
"There are usually multiple distichiae..."
There are usually multiple distichiae, and sometimes more than one arises from each duct. In some cases, there may be an entire row of extra eyelashes. Even though dogs do not have eyelashes on their lower eyelids, distichiae may be found on either the upper or lower eyelid. In most cases, they will be found bilaterally, or on both eyes.
Distichiasis is similar to, but not the same as, ectopic cilia, a condition that also occurs in dogs (for more details on this condition, please see the handout "Ectopic Cilia in Dogs").
What causes distichiasis?
"...but the condition is recognized as a hereditary problem in certain breeds of dogs."
All eyelashes, like all hairs, arise from hair follicles. With distichiasis, the hair follicles develop in abnormal locations, often deep within the meibomian glands. Since the meibomian glands produce lubricants for the eye, their openings are located along the inner margin of the eyelids. As the eyelash grows, it follows the duct of the gland and exits through the gland opening; thus the distichiae will be directed towards the eye (rather than away from the eye as would be normal for an eyelash). The reason why the follicles develop in this abnormal location is not known, but the condition is recognized as a hereditary problem in certain breeds of dogs. Distichiasis is a rare disorder in cats.
What breeds are more likely to have distichiasis?
The more commonly affected breeds include:
- American Cocker Spaniel
- Cavalier King Charles Spaniel
- Shih tzu
- Lhasa apso
- Shetland sheepdog
- Golden retriever
- Chesapeake retriever
- Boston terrier
What are the clinical signs of distichiasis?
The symptoms or clinical signs will vary with the severity of the condition, including the number of extra eyelashes, their size and their stiffness. In some cases, when the extra eyelashes are very soft, the patient does not show any symptoms. In other cases, the distichiae irritate the eye and cause inflammation, eye discharges and pain; left untreated the cornea may become ulcerated. You may notice redness or inflammation of the eye and/or the conjunctiva, excessive tearing (epiphora) or other discharges from the affected eye, and excessive blinking (blepharospasm). Due to pain, your dog may squint, keep the sore eye tightly closed or rub or paw at the eye. If there is a corneal ulcer, the affected part of the cornea often appears bluish and may be less shiny in appearance.
With chronic or long-standing distichiasis, the dog will often develop corneal scarring (white areas on the cornea), hyperpigmentation (dark areas on the cornea), or corneal neovascularization (abnormal formation of blood vessels across the surface of the cornea).
How is distichiasis diagnosed?
"A thorough eye examination, including fluorescein staining of the cornea and an assessment of the degree of tear production in the eyes, is usually necessary to assess the extent of any accompanying corneal injury..."
Diagnosis is usually made by identifying lashes emerging from the meibomian gland openings or by observing lashes that touch the cornea or the conjunctival lining of the affected eye. A thorough eye examination, including fluorescein staining of the cornea and an assessment of the degree of tear production in the eyes, is usually necessary to assess the extent of any accompanying corneal injury and to rule out other causes of the dog's clinical signs. Some dogs will require topical anesthetics or sedatives to relieve the intense discomfort and allow a thorough examination of the tissues surrounding the eye.
How is the condition treated?
Asymptomatic dogs with short, fine distichia may require no treatment at all. Patients with mild clinical signs may be managed conservatively. Conservative management mainly consists of the use of ophthalmic lubricants to protect the cornea and coat the lashes with a lubricant film; in some cases, the distichiae may be manually removed. This option is the choice for a patient with mild epiphora or if the distichiae are few in number and fine in texture. If the dog develops corneal ulcers from the distichiae, or if the dog continues to rub or paw at its face, indicating that the condition is irritating to him or her, surgical correction is the treatment of choice. The goal of surgery is two-fold, first to remove the offending eyelashes and second to kill the hair follicles so that the distichiae do not recur.
If only one or two distichiae are present, the surgeon may completely remove the affected portion of the eyelid to eliminate the misplaced follicles. If multiple eyelashes are present, the surgeon may use electrocautery, cryosurgery, or electroepilation to destroy the follicles, or may surgically split the affected lid and remove the tissues where the abnormal eyelashes are growing. All surgical treatments require general anesthesia.
Your veterinarian may recommend referral to an ophthalmologist for surgical treatment, especially in severe or complicated cases.
What are the risks?
"Left untreated, distichiae that are causing clinical signs will continue to cause irritation and pain, and the irritation may lead to severe corneal ulcers and secondary bacterial infections."
Left untreated, distichiae that are causing clinical signs will continue to cause irritation and pain, and the irritation may lead to severe corneal ulcers and secondary bacterial infections. These may lead to blindness or loss of the eye. The dog may further irritate the eye by scratching or rubbing at it.
Complications associated with electrocautery and cryosurgery may include excessive scarring of the eyelids. Regrowth of hairs may occur, requiring the need for repeated surgery.
What is the prognosis for a dog with distichiasis?
The prognosis is excellent for those dogs that do not show any clinical signs associated with their distichiae. For dogs with mild clinical signs, the likelihood that the condition can be managed with conservative treatment is good. In these cases, it is important to administer all medication and return for follow-up examinations as directed by your veterinarian. The prognosis for surgical correction of this condition is also generally good. Following surgery, post-operative rechecks are necessary for several months to monitor for regrowth of the eyelashes. Your veterinarian will discuss a diagnostic and treatment plan that is tailored to your dog's individual case to help you successfully treat this condition.
There is no preventative care for distichiasis, although veterinarians strongly discourage the breeding of two affected dogs to each other because of the hereditary nature of this condition.