Chapter 77: Epiphora

Web Chapter 77


Epiphora



Epiphora is defined as an overflow of tears from the conjunctival sac, as may occur with dysfunction of the lacrimal drainage system or with excessive lacrimation that results from ocular pain or irritation (Web Box 77-1). Chronic epiphora leads to staining of the facial hair and moist facial dermatitis, which results in a noncosmetic appearance and an unpleasant odor. Determination of the cause of epiphora is essential before treatment can be instituted and requires a mechanistic approach at first. Conditions that lead to excessive lacrimation should be ruled out before congenital or acquired dysfunction of the lacrimal drainage system is diagnosed. Other causes of epiphora include the irritating or painful conditions of entropion, corneal ulceration, anterior uveitis, and glaucoma (these disorders are addressed in other chapters in this section of Current Veterinary Therapy). Management of epiphora involves identifying and treating the underlying cause. When surgical treatment of the eye or adnexa is recommended to correct a cause of epiphora, referral to a veterinary ophthalmologist is recommended.



Web Box 77-1   Causes of Epiphora





General Principles


The nasolacrimal apparatus in dogs and cats comprises an upper and a lower punctum, which open into the upper and lower canaliculus, respectively. The canaliculi meet at the nasolacrimal sac and continue as a single nasolacrimal duct into the nose or nasopharynx. Several tests can evaluate nasolacrimal drainage system patency. These include applying topical fluorescein and observing it when it exits at the nares, flushing the duct with a nasolacrimal cannula or intravenous catheter, and imaging using dacryocystorhinography and computed tomography.


The results of these tests must be interpreted carefully. In some animals, the nasolacrimal duct opens into the pharynx, so that dye is not seen at the nares despite normal patency. These animals may be noted to swallow after the duct has been flushed, and the swallowing is used as an indicator of patency. Furthermore, during the flushing, the lids are everted so that the patient’s normal anatomy and physiology of the nasolacrimal drainage apparatus are altered. Therefore a positive result indicates a patent duct, but this finding does not prove that tears can drain under normal physiologic conditions. Additional diagnostic tests may help to establish an accurate diagnosis in patients with epiphora. These include Schirmer tear test, cytologic examination and microbial culture of nasolacrimal system discharge, retrograde flushing of the nasolacrimal system, orbital ultrasonography, and magnetic resonance imaging.



Congenital Disorders



Epiphora in Small Breeds


Shallow orbits, as seen in brachycephalic dogs and cats, cause prominent globe positions and as a result very tight-fitting lids with small lacrimal lakes. Because of this, tears are more likely to spill over onto the face than to remain in the lake and drain through the nasolacrimal puncta and duct. These animals also have hairs that originate from the medial caruncle and canthal area and act as a wick, which facilitates drainage of tears onto the face (Web Figure 77-1). In many animals, the punctum, although normally developed and in the correct location, is occluded due to entropion of the medial lower lid or the entire medial canthal region. When the lid rolls inward, the punctum is compressed, which prevents normal tear drainage and irritates the cornea due to the resultant trichiasis. Thus careful examination of the medial canthal region and the nasolacrimal system is necessary for determination of all the factors that lead to epiphora.



Treatment consists of surgical correction of the abnormal lid position. A Hotz-Celsus procedure can be used to correct lower medial entropion but tends to make an already large palpebral fissure even larger and may reduce the ability to blink. For this reason, a medial canthoplasty with removal of the caruncle and usually about one fourth of the upper and lower eyelid margins is performed. This corrects the macropalpebral fissure, caruncular trichiasis, and lower medial entropion while enhancing tear access to the nasolacrimal puncta (Gelatt, 2007). Cryoepilation of the caruncular hair also can be helpful if surgery is not an option. Seldom is there complete resolution of the epiphora because the shallow orbit persists.


Treatment with oral tetracycline (50 mg per dog daily) or metronidazole (100 to 200 mg per dog daily) meets with variable success in dogs to reduce staining of the facial hair and thereby make the epiphora less noticeable. Pet owners may obtain tylosin tartrate (sold under the trade name Angel Eyes), which promises stain-free eyes. All these drugs may alter tear composition and reduce bacterial growth but do not affect tear production. Keeping the facial hair short and clean is beneficial and preferable in most cases, especially if the problem is minor. Removal of the third eyelid gland is a poor choice of therapy because of the risk of keratoconjunctivitis sicca in predisposed animals.

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Jul 18, 2016 | Posted by in PHARMACOLOGY, TOXICOLOGY & THERAPEUTICS | Comments Off on Chapter 77: Epiphora
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