Iris prolapse is the protrusion or forward movement of the iris, the tissue that makes up the pupil, through a traumatized or perforated cornea. It is a common sequel to penetrating corneal wounds and/or ruptured corneal ulcers.
Iris prolapse usually has an acute onset. The protruding iris is often covered with a blob of mucus that appears yellow or white. The underlying iris itself is usually brown-black in color.Causes
In dogs, there are several common causes of iris prolapse: A wound such as this can occur when a new puppy is introduced into a household where a cat resides. The puppy runs up to meet the cat and the frightened cat claws the puppy's eye, lacerating the cornea and causing an iris prolapse.
An iris prolapse can also develop if a corneal ulcer deteriorates to the point where the eye is perforated. The iris tissue moves forward to plug the hole in the cornea. This type of prolapse occurs most often in the brachycephalic dogs, which are the flat faced breeds with bulging eyes, such as the Pekingese, pug, Lhasa apso and shih tzu.
Hunting dogs, dogs that are used in the field and dogs that run free are also prone to corneal lacerations that may result in an iris prolapse.
What to Watch For
Swelling and clouding of the eye, particularly the cornea
Ocular pain with marked squinting and tearing
Possible presence of an ocular foreign body
Blood in the eye
Distortion of the pupil
Other signs of injury to the body
A complete history and physical examination are performed to determine the possible cause of the lesion, and to identify any other injuries or abnormalities.
A thorough ocular examination is indicated, but this must be done with caution so that the eye does not rupture. The use of local anesthetic agents or sedation may be required to complete the examination. The appearance of the lesion is diagnostic.
A culture may be taken from the surface of the eye and the cornea may be stained with fluorescein.
The eye exam attempts to determine whether the eye is salvageable or whether it might need to be removed. Your veterinarian may refer your dog to a veterinary ophthalmologist for further evaluation and surgery.
A complete blood count, biochemical profile, and urinalysis are usually within normal limits, but they may be performed as part of a preoperative evaluation.
Iris prolapse is an ocular emergency and requires immediate medical and surgical therapy. Medical treatment includes the following:
Topical antibiotic drops are instituted, often every few hours.
Topical atropine may be started to try and dilate the pupil and pull the remaining iris away from the corneal wound.
Systemic antibiotics are often started by mouth or by injection.
An Elizabethan collar is applied so that the animal does not further traumatize the eye.
Analgesic or anti-inflammatory agents, such as carprofen and butorphanol, may also be started.
The type of surgery recommended depends on the viability of the eye:
If the interior of the eye is reasonably healthy, if there is still some chance of vision, and if the iris prolapse is recent, then the preferred treatment is surgical repair of the eye. Surgical repair involves replacement of any healthy iris or removal of any unhealthy iris tissue, and closure of the corneal defect. If possible, this surgical repair is done immediately.
If the interior of the eye has collapsed, is infected, or is filled with blood, or if the cornea is too damaged to be repaired, then the eye may need to be removed (enucleated).
Home Care and Prevention
If the cornea is surgically repaired, then it is very important to administer all medications precisely as directed by your veterinarian. The treatments following this type of surgery are labor-intensive, and must be done on a consistent schedule. Numerous rechecks are also required to ensure that the eye is healing well and that no complications are developing.
The postoperative care following an enucleation is simpler and may involve giving oral antibiotics and returning for a suture removal in 10 to 12 days. The dog may be required to wear an Elizabethan collar after both surgeries.
Take care when introducing new dogs to households with cats, especially if those cats have front claws. Prior to introduction of the new puppy, clip the nails of the cat short or apply Soft Paws. Keep the puppy restrained (on a leash or harness) and allow the two animals to move closer to each other gradually. Do not allow the animals to be together in an unsupervised setting. Always provide a mechanism for the cat to escape from the dog, by allowing the cat access to a place inaccessible to the dog. Keep the dog away from the cat's food and litter pan. It may take several days to a few weeks before the household cat is comfortable with the new dog and the puppy learns to respect the cat.
If your brachycephalic dog develops a corneal ulcer, see your veterinarian frequently during the healing period, so that any deterioration of the ulcer can be discovered before the cornea perforates. Examine the eyes of hunting and field dogs closely at the end of each session of out door activity.