Good question! An odd phenomena in many dogs today is that their eyes are much larger than those of their wolf ancestors. Why? Because we like them that way. People find big, open, honest eyes aesthetically appealing, so dogs have been bred to encourage larger eyes. This means that many of today’s most popular breeds are at extra risk for eye problems, whether minor infections or complete blindness.
You should be checking your dog’s eyes for problems at least once a week (and that “at least” is key, since you should really be doing it several times weekly).
If she has some gooey material, try to remove it immediately with a soft, damp cloth. Crustier eye boogers can be softened with a cloth soaked in warm water, then similarly wiped away. Keep an eye (get it? Eye?) on the color of the discharge, though. If it’s consistently yellow or greenish in color, she may have an eye infection.
Unlike humans, dogs have three eyelids. While it’s completely normal for it to jut out further in certain breeds, in others it can indicate neurological problems. A simple phone call to your vet
should let you know whether or not you need to worry about this. 
Cloudiness in the iris and pupil can often indicate corneal damage and should be addressed as soon as possible. Conditions like sties are fairly common in dogs and appear almost exactly as they do in humans – a reddish, swollen area along one of the rims of the eyelids. You can help your pup feel more
comfortable until you get to the vet by applying a warm, damp cloth to her eye for five-minute periods. Your vet will most likely prescribe a cream to be applied directly to the sty.
Pink eye (also called conjunctivitis) is even more common and comes in several flavors. At its simplest, conjunctivitis is an inflammation of the mucous membrane that protects the eye. It can be caused by an eyelash or hair falling into the eye and developing an infection or bacteria and viruses that can affect both eyes. In nearly all cases, the eye will be bloodshot, discharge from the eye will be yellow or greenish, and the eye will develop a crusty look. The three main types of pink eye are:
In bacterial/fungal conjunctivitis, a foreign body or injury has caused an inflammation and, if
not removed, can grow bacteria and fungus in the eye at an accelerated pace. This causes a
subsequent infection. Your vet will probably use an eye wash to try and flush out the cause of
the infection and may prescribe accompanying medication.
Parasitic conjunctivitis is caused by the invasion of the eye by a parasitic worm.
Your vet will be able to see the worm during an eye exam, so after numbing the area with anesthetic he or she should be able to extract it easily. If not, a special antiparasitic eye wash can be used to kill the worm and stop the infection.
Viral conjunctivitis is caused by the same viruses that cause distemper and hepatitis. The
primary symptom of this type of conjunctivitis is an extremely dry eye or difficulty producing
tears, so your vet will suggest the consistent application of a saline wash to help keep the eyes
moist until the virus has run its course.
Two opposite eye conditions that tend to vary according to breed are watery eye and dry eye. While the symptoms are pretty selfexplanatory, the causes can be different. Watery eye can be traced to anything from a foreign object in the eye to complex conditions involving the third eyelid or glaucoma. Some dogs are simply born with narrow tear ducts. Your vet will be able to determine the cause and corresponding treatment. On the other hand, dry eye is typically caused by inherited disorders or viral/bacterial infections. Because the eyes aren’t moistened by tears, conjunctivitis can form easily. If the condition progresses without treatment, the eyes themselves become cloudy or produce pus and ultimately the cornea can become damaged. Minor cases can often be treated with an eye-moistening solution, while others may require surgery or more intense medication.
Because of their general happy-go-lucky and rough play demeanor, dogs have a tendency toward corneal injury and scratches. While humans damage their corneas with contact lenses, fingernails, and other objects close to their own bodies, dogs are closer to the ground and can experience corneal damage from flying rocks, dirt, other dogs’ claws, and any number of other outside influences. You probably won’t even realize that anything has happened at first, but a cloudy look will develop in the eye over the course of a few weeks. Actual cuts on the eye can develop ulcers or infected areas containing pus. Your dog will probably begin to squint and rub her eye a few hours after the injury occurs.
Because corneal injury can be extremely minor or extensive, your vet’s course of treatment will vary according to the degree of damage. A fluorescent dye is dropped into the cornea to aid in
diagnosis. Because all of the dye is absorbed by the damaged areas, the severity of the injury is almost immediately apparent. 
Dilating the pupil with the same solution used by ophthalmologists helps relieve the pain of corneal damage in some dogs, while others will require additional medication or anti-inflammatory meds.
Cataracts are caused by the clouding of proteins in the eye lens. This cloudiness makes vision difficult or impossible depending upon the extent of the cataract. You’ll notice the whitish-yellow look of the lens immediately, but, unfortunately, the damage will already be done. Cataracts are irreversible. In pups who have become partially or completely blind, a veterinarian may suggest surgery; because the surgery is somewhat intensive, it is only considered when the benefits strongly outweigh the negatives.