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Dog: Corneal Ulcers

General information

Other common/scientific names: corneal scratches, corneal erosions

The cornea is the clear, dome-shaped surface that covers the front part of the eye. It is a tough, firm layer which protects the pupil, iris and other interior parts of the eye. The transparency of the cornea allows light to pass through and its curvature gives it focusing power. The cornea has no blood vessels but does contain many nerves making it very sensitive to pain or touch. The eyelids and tear film provide lubrication and nourishment to the cornea.

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Abb. GFTALXGJ: Schematic illustration of the eye, side view, showing the position of the conjunctiva and cornea.

A corneal ulcer results when the surface of the corneal is damaged and layers of the cornea become eroded.

Corneal ulcers can be classified as:

  • Simple, superficial ulcer: Ulcer which is small and involves the outermost layer of the cornea.
  • Deep ulcer: Ulcer where the deeper layers of the cornea are damaged.
  • Indolent ulcers: Ulcer which is chronic, slow healing and recurrent. Indolent ulcers form a lip around the edge of the ulcer preventing it from healing.
  • Melting ulcer: Ulcer where the cornea dissolves and can result in rupture of the eye.
  • Descemetocele: Ulcer that has penetrated through the cornea completely except for the very inner layer of the cornea. A dog with a descemetocele is at high risk for rupture of the eye.

Causes

There are several causes of corneal ulcers. These include:

  • Contact with plants, thorns or bushes. Grass awns can become trapped underneath the nictitating membrane or third eyelid and cause irritation and ulceration to the cornea.
  • Scratches and injuries from another animal. Cats are notorious for causing corneal injuries.
  • Self trauma - rubbing or scratching at an itchy or painful ear or eye can cause injury to the cornea.
  • Chemical irritation such as shampoos or insect repellants
  • Foreign body injury
  • Abnormal eyelashes such as distichiasis
  • Other eye conditions such as keratoconjunctivitis sicca (KCS) and entropion
  • Infections

Cardinal symptom

Painful eye

Symptoms

Corneal ulcers are painful. Signs of eye pain are squinting and holding the eye shut, excessive blinking, excessive tearing and rubbing at the eye. Photophobia is common. Some corneal ulcers result in the cornea appearing cloudy or even red. The conjunctiva may be reddened and swollen. Some dogs will have a constricted pupil.

Diagnosis

A corneal ulcer is diagnosed by applying a special dye to the cornea. This involves placing a thin strip of paper with fluorescein stain impregnated on the tip into the corner of the dog’s eye. If an ulcer is present, the stain will stick to the damaged area and appear a bright green color. The size and depth of penetration of the stain will determine the extent and severity of the ulcer.

Diagnosis of a corneal ulcer must include a complete ophthalmic examination to rule out other eye conditions and remove any inciting factors.

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Abb. GFTAX7XK: Fluoroscein Stain.
This is a photograph of using fluorescein stain to detect a corneal ulcer. Note the orange dye on the tip of the fluorescein strip. The dye turns green when it contacts the eye tissue. The arrow points to a corneal ulcer which has taken up the stain and appears as a green area on the cornea.

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Abb. GFTAYZHA: Fluoroscein Stain.
This is a photograph of a corneal ulcer stained with fluorescein. A light is used to detect the damaged area on the cornea.

Treatment

Treatment of corneal ulcers will depend on the depth and cause of the ulcer. Antibiotic eye drops or ointments are needed to prevent or treat an infection. Eye drops or ointments which cause the pupil to dilate are used to provide pain relief. Anti-inflammatory medications may also be used to provide pain relief. Artificial tears are necessary in the cases where tear production is lacking. Corneal ulcers may require treatment several times a day.

Indolent or chronic ulcers may need to be debrided or scraped to freshen the edges and allow for healing. Severe corneal defects may need special procedures such as a conjunctival flap, third eyelid flap or a temporary tarsorrhaphy to provide protection to the cornea and allow healing.

It is important to administer all medications as recommended by your veterinarian. If you have difficulty applying eye medications to your dog, consult your veterinarian.

Prognosis

A simple, routine corneal ulcer should heal easily. However, deep or melting ulcers can result in rupture of the eye and loss of vision if not treated promptly. Recurrent ulcers can result in scarring and pigmentation of the cornea which reduces vision. Underlying conditions such as KCS can be chronic requiring daily medications which can be both frustrating and expensive.

Tips

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Abb. GFTB5PM0: Applying eye ointment.
This is a photograph of applying eye ointment to a dog’s eye. Care should be taken not to touch the tip of the ointment tube to the eye. Place your hand on the dog’s face, under the eye to steady your hand if the dog moves and prevent touching the eye.

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Abb. GFTB6WDZ: Applying eye drops.
This is a photograph of applying eye drops to a dog’s eye. The dog’s head should be tipped upward to allow the drops to fall into the eye. Place your hand on the dog’s face, under the eye to steady your hand if the dog moves and prevent touching the eye.

CAUTION

If you notice a foreign object in your dog’s eye, do not attempt removal. Contact your veterinarian immediately.

Update version: 4/24/2014, © Copyright by www.enpevet.de
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