Caring for eye problems
Care for eye injuries should not be something that is put off, and being aware of some common problems will help you keep your dog's eyes sharp
By Ben J. Character
The eyes are amazing little organs. Functionally they are made up of various components including, the globes themselves, the lid, which help protect, glands to produce tears, and the optic nerve, which transmits signals to the brain.
Of course, within the globe are more structures that contribute to the function of the eye. The cornea is the clear window through which the eye receives light. This light is then regulated by the iris, the colored part of the eye, which works like the diaphragm of a camera. Next the lens focuses the light so that it strikes the retina correctly. The retina, which is literally a blanket of photoreceptors, receives the light photons and converts them in electrical signals that are sent to the brain. Behind the retina is a sheet of specialized cells, called the tapetum lucida, that reflect light and improve night vision (also what you see at night when you shine a flashlight at a critter). And of course, the last step in the process is for the brain to process these electrical signals into recognizable mental images.
The eyes, like all other complex systems, are irreducibly complex. One way to consider this is that if one part is not working correctly then the final product of the system will not be produced normally — or at all. For this reason and because of the important role that vision plays in the work that our dogs perform, eye care is a critical component of maintaining high performance in your dog.
Fortunately, because the eyes are so well designed they usually just role along without much need for attention. Unlike ears that need to be cleaned, stomachs that need to be fed, and muscles that need to be worked, unless there is an eye problem they are frequently taken for granted. But care for injuries or problems with your hunting dog's eyes should not be something that is put off, and being aware of some common problems will help you keep your dog's eyes sharp.
The most common eye injury is probably related to trauma to the cornea. Corneal ulcers and superficial lacerations can occur from a variety of sources. Briars, small sticks, foreign bodies and trash can get into the eye damaging the cornea.
The cornea is a very sensitive part of the eye because it needs maximum protection. The eyelids form the primary barrier to corneal damage. The blink reflex is super quick and blocks most projectiles and other traumatic objects from reaching the cornea. Our dogs also have an extra eyelid (called the "third eyelid" or nicitans membrane), which works as a secondary barrier to trauma. In addition to these physical barriers, the cornea has a super-sensitive network of nerves contained within it. Frequently the most injury prone areas of the body (ear pinna, toes, nose, etc) also are the most sensitive, making reflex protection mechanisms quicker and more successful. The old saying goes, "the eyes are the windows to the soul," and when the cornea is damaged it is as if the window has become dirty, scratched up, or possibly even broken.
Corneal ulcers, inflamed eyes
| About Ben Character | |
|
Dr. Character is a freelance writer and private veterinary practitioner
concentrating on sporting dog issues. He has practiced large and small animal medicine and surgery since graduating from Auburn University. Recently, he went on to complete post-doctoral studies at Mississippi State University. Dr. Character is a certified PennHIP member and writes for magazines such as Retriever Journal and Pointing Dog Journal. He is an avid outdoorsman who resides in Union, Alabama, south of Tuscaloosa, with his wife and two children. |
Corneal ulcers are not full-thickness injuries, instead only the top few cellular layers are damaged. But, corneal ulcers produce intense pain to the globe. A dog with corneal damage will usually squint or possibly even refuse to open the eye. There is frequently a large amount of discharge from an eye that has a corneal ulcer secondary to an increase in tear production to the point that the lacrimal drainage system is overwhelmed and the tears spill out of eye. Generally speaking this discharge is not colored or thick, but rather watery and clear.
Treatment of corneal ulcers generally consists of an antibiotic ointment and something for pain. Atropine ophthalmic ointment has a long lasting effect and is commonly used to reduce spasms inside the eye and decrease pain. Contrary to this, effects produced from ophthalmic antimicrobial ointments are short-lived making their constant presence in the eye recommended. The ointment preparations generally last for up to two to three hours in the eye before being washed out by tears, while solutions, or drops, only last at most half that time. So, when treating an eye condition using ophthalmic ointments or drops be sure to apply often.
In some cases, foreign bodies trapped in the eye can cause corneal ulcers. The most common occurrence of this is when grass seeds become stuck behind the third eyelid of the dog. These seeds possess tiny barbs that tend to hook onto the lining of the eyelid preventing their removal. The consequence is that every time the eyelid is blinked it rubs the seed (or other foreign body) across the cornea acting as an abrasive and preventing the fragile outer layer from ever completely healing. In such cases, no matter how long or diligently you apply medications these ulcers will not heal until the foreign object is removed.
Sometimes such foreign objects do not actually become trapped, but instead simply create significant irritation. Other irritating sources include, wind (usually happens after riding in the bed of a truck), dust/sand, and chemicals, such as shampoos and other soaps. Simple conjunctivitis from these causes usually shows up as a very red and swollen eye, yet the dog will continue to hold the eye open normally. In some of these cases there will be discharge from the eye, but this discharge is generally a thicker, mucoid or yellowish type versus the clear and more watery discharge seen with an ulcer.
It is important to verify the difference between the ulcer and simply an inflamed eye because their treatments are somewhat contradictory. While antibiotics may be beneficial to both, the eye with conjunctivitis will respond more quickly if ophthalmic treatments containing a mild steroid are used. The danger is that if there is an ulcer present, steroids, such as hydrocortisone, will prevent healing and can even make the ulcer worse. In the most severe cases, the use of steroid can allow opportunistic bacteria to take hold which release enzymes into the ulcer and literally melt the cornea away resulting in permanent disfunction and sometimes the need for enucleation (removal of the eye).
The good news is that a simple conjunctivitis is usually easy to treat. If you have any doubt concerning the possibility of an ulcer, your veterinarian can stain the eye to determine if the cornea has been damaged.
The last few common problem areas for eyes involve the eyelids. As mentioned, eyelids take the brunt of the trauma directed to the eye. They are prone to lacerations and abrasion from charges into thick cover. Many sporting dog owners are familiar with a condition known as "cherry eye" where the third eyelid gland swells and protrudes up next to the globe, but there are a few other problems that the eyelids can develop.
Entropion
Entropion (en-tro' peon) is a condition in which the eyelids tend to roll in toward the eye. This problem is generally seen early in life since it is fundamentally a conformational defect. Definitive correction usually requires surgery to pull the lid back into correct position, but sometimes tacking will be successful in young puppies. Entropion causes problems for the dog because when the lid rolls in the eyelashes are suddenly in the wrong position and become foreign bodies scratching on the cornea. If not treated, corneal ulcers and chronic irritation leading permanent scarring or pigmentation of the cornea are possible, both of which can cause severe vision impairment.
Ectropion
These same consequences can occur from the condition opposite of the entropion called ectropion (ek-tro' peon). Ectropion is commonly seen in hound breeds. The eyelids droop so much that a flea could swim laps in the resulting tear pool. Generally speaking, bird dogs don't have a major problem with ectropion, but it is seen to some extent in the spaniel breeds. Ectropion can also occur secondary to lacerations and other trauma to the lower lids that results in either gaps or scars that contract and pull the eyelid down and away from the globe. In either case, the solution is to repair the lid via reconstructive surgery. These eyes will be less likely to be irritated or incur trauma from outside sources once the droopy lid is repaired.
