My technician and I just got back from a wonderful veterinary ophthalmology conference and would like to share some things we learned. Cats and Dogs are susceptible to several disease states of the eye. Most of these problems are best handled by Veterinary Ophthalmologists- specialists that have an additional 4- 5 years of training and internships in their area of specialty. Here’s a kitten with normal eyes.
Eye Discharge
What causes discharge from the eyes? Sometimes, there is something stuck on the surface or in the conjunctiva of the eye (called a foreign body). Some animals’ eyelids roll inward, and the lashes rub on the cornea. Other animals’ eyes roll outward and collect debris that irritates the cornea. Some lids even have extra lashes that scrape the cornea. Small tumors or growths can be present. All of these problems can cause discharge from the eye. The tear ducts can also become plugged and cause spillage of the tears and secondary bacterial infections. Sometimes, animals have to have surgery (usually performed with a laser) to correct these problems.
Here’s a dog with abnormal discharge from the eyes due to its breed.
Corneal Damage
The cornea is the outermost layer of the eye, and in certain breeds (brachycephalic- Frenchies, Boston Terriers, Bulldogs, etc). In these breeds, the eye sticks out farther than it normally does and predisposes these dogs to injuries. Corneas can be injured by trauma or damaged by viral or bacterial agents. There is also a disease that lowers tear production called Keratoconjunctivitis Sicca. The lowered tear production leaves the cornea dry and susceptible to ulceration. We can diagnose a corneal ulcer by applying a tiny bit of stain to the surface of the eye and seeing if it is taken up by the cornea. We can also diagnose lack of tear production with tear measurers we put in the corner of the eye. Here’s a dog whose eyes have been stained. Notice the stain coming from his nose also.
Diseases Affecting the Iris
The iris is the colored part of the eye that surrounds the pupil. There are several diseases that can affect the iris. Inflammation of the iris is called uveitis and is quite common in both cats and dogs. There are several causes of uveitis, including viral, fungal, parasitic, bacterial, and neoplasia (cancer). Uveitis is quite painful and is generally treated with anti-inflammatories and antibiotics or other medications to resolve the underlying cause. Here’s a kitty with abnormal pigmentation of the iris.
Diseases Affecting the Lens
The lens of the eye sits in the middle and is responsible for the focus part of vision. Two common diseases of the lens are nuclear sclerosis and cataracts. Nuclear sclerosis is just an age-related dense packing of the lens fibers and results in the grey/blue tinge we see in older animals. It does not affect vision. Cataracts is often caused by underlying problems such as diabetes and have effects on both the vision and sometimes the other structures of the eyes. It is necessary to dilate the eye to distinguish between these two conditions. Cataracts cause blindness and sometimes discomfort. Cataracts can be easily removed and replaced by normal lenses by veterinary ophthalmologists. Here’s a little chihuahua with a cataract.
Glaucoma in Animals
The most painful condition of the eye is called glaucoma and is defined as an increase in the intraocular pressure of the eye. The fluid that is continuously produced in the eye is incapable of draining out of the eye and causes increased pressure and eventual irreversible blindness. This is a condition that must be diagnosed by an instrument that measures the intraocular pressure and needs to be treated early to retain vision. It is treated with a combination of medical therapy and surgery.
Problems With the Retina
There are also several problems that can occur with the retina- the back of the eye. Sudden acquired retinal degeneration (SARD) is a poorly understood sudden blindness that occurs most often in overweight, middle-aged female dogs but can occur in any dog. One of my close friend’s dogs suffered sudden, complete blindness from this disease 3 years ago and is managing to function quite well by accentuating the use of his other senses. His owner taps the ground and snaps her fingers to guide him, and he follows his nose and proceeds carefully in unfamiliar territory.
Animal of the Month
Our animal of the month is a little Boston Terrier named “Steve,” whose sister had accidentally poked him in the eye with a stick while they were playing outdoors. Steve came to us rapidly blinking and squinting his left eye. His left eye was discharging an excessive amount of tears, and Steve was obviously in quite a bit of pain.
I performed a Schirmer Tear Test to see if the tears were being normally produced, and they were. Then, we stained the eye to see if the cornea was ulcerated. There was a tiny area that did stain, which told us that the cornea was damaged. The area was so small that the amount of pain that Steve was exhibiting was disproportional to the type of injury.
I examined the eye carefully with an ophthalmoscope, and I could see that the fluid inside the eye was cloudy and reactive to something, but I couldn’t see well enough to make a diagnosis. I put Steve on a strong anti-inflammatory and pain medication and numbed the eye. Steve was referred to one of our local veterinary ophthalmologists.
Using their specialized, powerful optical equipment, they were able to see a tiny splinter of wood deeply embedded in the eye. And much to Steve’s relief, they were able to extract the splinter.
Conclusion
Please inform your veterinarian as soon as possible if your pet has ocular discharge, is squinting, blinking excessively, or holding an eye closed, or if the eye appears cloudy to you. Otherwise, they may not be able to enjoy all of this lovely sunshine we are finally being blessed with!
