What is the lacrimal duct?
The lacrimal duct is part of the nasolacrimal system. The nasolacrimal system consists of a series of narrow tubes that allow tears to drain from the eye. The nasolacrimal duct begins with two small openings in the eyelids near the nose; one of these openings is located on the upper eyelid and one is on the lower eyelid. These two small ducts meet in a single, larger nasolacrimal duct, which extends down to the nasal passages. This system allows excess tears to drain from the eye to the nose and mouth.
What is a lacrimal duct obstruction?
In some dogs, this nasolacrimal duct can become obstructed, or blocked. Obstruction may result in tears overflowing and running out of the eye. This overflow of tears can lead to moisture and tear staining below the eye. The lower nasolacrimal duct is most commonly affected, and obstruction of the lower duct results in more clinically visible effects.
What are the possible causes of lacrimal duct obstruction?
Nasolacrimal duct obstruction can have a variety of causes.
In some cases, the obstruction is related to the shape and size of the dog's head and muzzle. Obstruction may also be caused by a hereditary defect in the formation of the nasolacrimal duct. This defect results in the lack of an opening where the nasolacrimal duct meets the conjunctiva (pink tissue surrounding the eye). This is referred to as imperforate puncta. This condition is most commonly seen in Cocker Spaniels, although other breeds may be affected.
In other cases, lacrimal duct obstruction develops after birth. Inflammation or infection, within the eye or lacrimal duct, may lead to swelling that blocks the duct. Obstruction may also be caused by tumors that develop along the duct, or by foreign material lodged within the lacrimal duct.
What are the clinical signs of lacrimal duct obstruction?
The signs of nasolacrimal duct obstruction are largely cosmetic in nature. Most affected dogs have excessive watering of the eyes, or reddish-colored tear staining of the face.
"Most affected dogs have excessive watering of the eyes, or reddish-colored tear staining of the face."
In chronic or severe cases, however, bacteria may begin to grow in the moist hair around the eyes. You may notice that your dog’s face develops a foul odor, due to the presence of these bacteria. Dogs may also develop a skin infection below the eyes, resulting in redness, itching, swelling, and/or hair loss.
How is lacrimal duct obstruction diagnosed?
Nasolacrimal duct obstruction is often diagnosed using a dye known as fluorescein. This dye fluoresces (glows) under a black light, allowing your veterinarian to visualize even small amounts of dye. Several drops of this dye are placed in the eyes; from there, the dye should travel down the nasolacrimal duct and be visible in the mouth and nose. If the dye does not appear in the nasal cavity within 5-10 minutes of administration, this suggests a nasolacrimal duct obstruction.
"Nasolacrimal duct obstruction is often diagnosed using a dye known as fluorescein."
In a sedated patient, your veterinarian may examine the eye with magnification to ensure that there is a duct opening visible at the eye. If this opening is visualized, a cannula (thin tube) can be inserted into the opening and used to flush saline into the nasolacrimal duct. This may be enough to alleviate mild obstructions, but can also assist the veterinarian in the diagnosis of more severe obstructions.
In some cases, further diagnostic tests may be recommended. These tests might include imaging, such as X-rays, CT, or MRI, to rule out tumors that could cause obstruction. Your veterinarian may also recommend bacterial culture to identify infection, or other tests depending on your pet's condition.
How is lacrimal duct obstruction treated?
Many cases of nasolacrimal duct obstruction are caused by inflammation. In these causes, anti-inflammatory medications and antibiotics may alleviate the obstruction. Use all medications as recommended by your veterinarian, and return for all scheduled rechecks, in order to maximize the chances of resolving your dog’s lacrimal duct obstruction.
"Many cases of nasolacrimal duct obstruction are caused by inflammation."
In other cases, surgery may be required for treatment. Surgery may be used to enlarge the opening to the duct, remove tumors that are compressing the duct, or remove foreign bodies from the duct. In more severe cases, a stent may be placed to allow flow through the lacrimal duct.
What happens if lacrimal duct obstruction is not treated?
Without treatment, nasolacrimal duct obstruction will cause continued issues with tear staining. Untreated dogs also have an increased likelihood of skin infection around the eyes, due excessive moisture.