A team of scientists have used national registries of more than 3.4 million Swedes aged 40 to 80 to study the association between dog ownership and cardiovascular health. Their study shows that dog owners had a lower risk of death due to cardiovascular disease or to other causes during the 12-year follow-up.
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If we humans had to name the sense that was most vital in helping us navigate the world, many would choose vision. Sure, hearing is highly advantageous; and some might argue that taste, touch and smell help make life worth living. But if you stop and consider, even our human language is oriented toward the visual: we “see” the point; have high “regard” for things we like; share different “views” on a subject. But dog vision is a much different use of this sense.
How dogs see and use sight is very different from us humans. Woman and dog in glasses. Photography by Dirima / Shutterstock.
Few individuals would examine their brand-new smartphone by giving it a few experimental sniffs. Yet that’s exactly how our dogs acquaint themselves with new situations. For canines, noses and tongues easily trump eyes when it comes to sensory input.
That certainly doesn’t mean dog vision is useless — but “contributory” might be a reasonable term. In fact, most vets would agree that blind and low-vision canines can learn to get along perfectly well by letting their snouts and taste buds lead the way.
“Blind canines generally adapt quickly to their environments, especially if furniture placement and routines are kept consistent,” notes Dr. Lisa McIntyre, owner and founder of The Welcome Waggin’ mobile veterinary service. “They rely on senses such as hearing and smell much more than they rely on their vision to assess and navigate their surroundings.”
Placed side-by-side, diagrams of the canine and human eye might initially seem comparable. The basic apparatus is, in fact, fairly similar. Eyelids protect the cornea, which is a transparent covering for the iris and pupil. The iris narrows or widens to allow light into the eyeball’s interior structure. This light travels through a lens, which focuses the light as it hits the retina toward the back of the eye. The retina converts the light and sends the optic nerve a signal, which allows the brain to interpret whatever is in the visual field.
Examined from several perspectives, however, dog vision and what dogs see clearly differs from human vision and what humans see. Here are a few distinctions worth noting.
Did you ever notice the placement of your dog’s eyes? Photography ©MichaelRenee | Thinkstock.
Look directly at your dog for a moment. Notice the eye position? Instead of pointing straight ahead, the eyes of most canines are actually directed slightly outward. Proportionally, they’re also spaced more widely than human eyes.
In her book Inside of a Dog: What Dogs See, Smell, and Know, cognitive scientist Alexandra Horowitz observes that this placement facilitates enhanced peripheral vision and “a panoramic view of the environment: 250 to 270 degrees, as contrasted to humans’ 180 degrees.” The trade off, unfortunately, is that canine depth perception can be somewhat compromised when there’s less overlap in the visual field.
Another discernible difference is pupil size. The pupil is the black center of the eye that admits light. In humans, its size can vary considerably — huge when we’re afraid, dramatically diminished when we glance at the noon sun. Horowitz observes that canine pupils tend to be more fixed in size, regardless of external stimuli. She also notes that humans have a more prominent sclera, or “white area,” which makes the direction of our focus fairly apparent. Because most canines have relatively little sclera showing, the precise object of their attention isn’t always easy to identify.
Dog eyes also have a nictitating membrane — essentially, a third eyelid. “This membrane helps protect the cornea and clear away debris, like a windshield wiper,” Dr. McIntyre explains. “It also contains a gland that helps supply tears to the eye; plus lymphoid tissue, which can help discourage infection.” The membrane normally isn’t in plain sight from day to day, but Dr. McIntyre notes that you might glimpse it when your dog is asleep. It’s also more visible when it’s functioning as an active barrier to wind, dirt or sand.
In both humans and canines, the eye’s retina contains two types of receptors: rods and cones. Rods help the eye perceive motion and shades of light. Cones let the eye perceive color and fine detail. Horowitz explains that dogs have a lower cone density than humans. This can impact things like visual acuity and the ability to distinguish levels of brightness.
In humans, there’s an area called the macula in the central part of the retina. Within the macula, cone concentration is highest. In contrast, Dr. McIntyre explains that dogs have a horizontal band called a “visual streak.” She describes this as the area of greatest visual acuity, with the highest concentration of cones and lowest concentration of rods. She also explains that the width of this area generally depends upon the length of the snout; with shorter-nosed canines tending toward much shorter streaks. Horowitz notes that dogs with longer streaks have better panoramic and peripheral vision.
One popular misconception is that dogs can’t see any color. That’s untrue — but because they have a higher number of rod cells and fewer cone cells, says Dr. McIntyre, “they’re not able to see details or colors as well as humans.” Horowitz points out that “the density of rods in dogs’ eyes varies, but they have as much as three times as many rods as we do.”
Dr. McIntyre explains that the human retina contains three types of cones, each sensitive to a different range of the color spectrum. These cones allow us to see shades of blue, green and red. Canines, in contrast, only have two types of cones: sensitive to yellow and blue. That means a dog’s color perception is similar to that of a human with red/green color blindness. “A dog’s world mainly appears in varying shades of yellow, blue and violet,” Dr. McIntyre explains. “So, an orange Frisbee will appear yellow on green grass — which, to a canine, also looks yellow!”
Some dog parents are moderately freaked out when they see their dog’s eyes shining eerily in photographs. Horowitz explains that this glow is due to a unique feature called the tapetum lucidum (in Latin, “carpet of light”). This thin, triangular film of tissue sits behind the canine retina, and rebounds light like a mirror. Rods therefore get a bonus chance to capture the visual.
In part, that’s why dogs have such superior low-light and night vision. Dr. McIntyre notes that this enhanced acuity is also due to the higher number of rod cells, which help canines see more shades of gray, black and white.
This higher concentration of rods also helps dogs perceive movement, explains Dr. McIntyre. Canines can perceive a higher “flicker rate” than humans. “Our world is seen through a series of snapshots that are fused together to form a static image,” she notes. “We humans see about 60 images per second; while dogs see around 70 to 80 snapshots per second.”
Why are most dogs able to find that orange Frisbee so readily? “Because they can easily see it sailing through the air,” Dr. McIntyre says, “and they can also track it by its distinctive smell.”
In numerous ways, our dogs are a lot like us. But next time you watch your pooch navigate the living room, chase a toy or focus on the treat in your hand, take some of these visual variances into account. Our canines sit faithfully by our side as we regard the world together. Yet on many occasions what we actually see can be remarkably, distinctively different.
Thumbnail: Photography by fotoedu/Thinkstock.
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Concerned about your eyesight? Check out University Health News’ piece on Eating for Eyesight: Which Foods Protect Your Eyes? >>
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You could say fall is her favorite 🍂
By: http://ift.tt/2iqzjVnPosted by Cool Animals on Monday, October 23, 2017
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We’re deep into fall now.
And this pup’s deep in the leaves!
Too adorable.
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If you’re anything like me, your dog is the apple of your eye, and one of the dearest creatures in the world. Your dog’s ocular health may not be the first thing you think of in the morning, but your dog relies on her eyes just as much as you do. Cherry eye in dogs is a condition that doesn’t affect all pups, but can affect any dog’s tear production and eye health.
The signs of a case of cherry eye in dogs are easy to spot; caught and treated quickly, it’s possible to reverse the deleterious effects. In severe cases, though, your veterinarian or a veterinary ophthalmologist may have to perform surgery to prevent long-term eye problems. Let’s talk about cherry eye in dogs and see how to treat it!
An example of cherry eye in dogs. Photography ©Flickr user Chris via Creative Commons License. Some size modifications have been made to fit this site.
All dogs have a third eyelid, which is also called a nictitating membrane, as well as two glands that produce tears to lubricate their eyes. The nictitating membrane, based in the lower eyelid, is a sort of secondary shield for the eyes. It protects dogs’ eyes from wind, dust, and other foreign objects as they play or work. The nictitating membrane has its own dedicated tear gland. This tear gland produces anywhere from 35 percent to 50 percent of the total moisture in a dog’s eye, and is thus an essential component to overall eye health in dogs.
Cherry eye in dogs occurs when the connective tissue that holds the gland in place is weak, faulty or otherwise damaged. The nictitating membrane’s tear gland comes loose and prolapses from its little pocket and out of the bottom or corner of the dog’s eye, usually closest to the nose. This bulbous, fleshy, red protrusion of the gland from the lower eye is the primary symptom of cherry eye in dogs, and gives the condition its colorful, fruited moniker. If your dog has, or has had, cherry eye, you should be especially watchful. Extended or recurring cases of cherry eye can lead to decreased tear production and other eye problems.
Cherry eye in dogs is a congenital disorder, passed on from generation to generation. Beyond genetic predisposition, it is still unknown what precisely causes cherry eye to manifest. We do know that the ligaments and connective tissues that hold the tear gland of the nictitating membrane fail to keep it in place, and that there are a number of dog breeds that are statistically more likely to suffer from cherry eye.
Owners and prospective owners of Basset Hounds, Beagles, Bloodhounds, Boxers, Bulldogs (English and French), Cavalier King Charles Spaniels, Cocker Spaniels, Lhasa Apsos, Neapolitan Mastiffs, Newfoundlands, Pekingese, Poodles (especially Miniature), Pugs, Saint Bernards, Shar-Peis, Shih Tzus, and terriers (including the Boston Terrier, Bull Terrier and West Highland White Terrier) should be aware of the increased risk for cherry eye in these breeds. Breeds with shorter muzzles, along with toy or teacup varieties in general, are at higher risk for cherry eye. However, cherry eye can happen to any dog, and at any age.
Caught early enough, I’ve come across many online accounts of successful massage treatment of cherry eye in dogs. Using a combination of a warm, moist cloth and dog-safe eye drops, the home method of treatment involves calming the afflicted dog and gently massaging the prolapsed tear gland of the nictitating membrane until it sucks back into place. Even when this technique is successful, though, there is no guarantee that the cherry eye is gone for good. A dog with a resolved case of cherry eye may have it recur, and a dog who has had cherry eye in one eye is at higher risk of having it happen in the other as well.
The safest bet is a visit to the veterinarian, who can accurately determine the specific reason for your dog’s cherry eye. Since there is no fixed cause, an early consultation can help ensure your dog’s long-term eye health. There are three common surgical options for cherry eye. In the first case, the vet may be able to stitch the prolapsed tear gland back into place. In other cases, a veterinary surgeon may find the connective tissue too weak to cradle the gland properly. For situations like these, the surgeon will attempt to create a new pocket or envelope to hold it in place permanently.
The third option was, in past years, the most common, and involved complete removal of the cherry-eyed tear gland. Removal of the prolapsed gland is an option of absolutely last resort. Removal of the affected tear gland will require lifelong after-treatment with artificial tears to prevent chronic dry eye and secondary problems that can occur when there’s insufficient production of lubrication for a dog’s eyes.
Left untreated, a dog with cherry eye is at greater risk for long-term health problems. The longer the gland is prolapsed, the greater the risk of associated problems. Proper blood flow to the gland is restricted. The gland may swell the longer it is exposed. Pawing, scratching or rubbing the affected eye may irritate it further, and create opportunities for secondary bacterial or viral infections to take hold.
In most cases, caught early enough, cherry eye in dogs is successfully treated or managed with minimal veterinary assistance, hopefully before your dog needs surgery.
Tell us: Have your dogs ever had an occurrence, or repeat instances, of cherry eye? Were you able to attend to the problem under your own auspices, or did a vet need to perform surgery? Share your experiences with cherry eye in dogs in the comments below!
Thumbnail: Photography ©Flickr user Litherland via Creative Commons License. Some size modifications have been made to fit this site.
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Sadie, my chocolate Labrador Retriever, came into our lives when she was 5 years old. Her elderly owner had passed away, and she had nowhere to go, so we took her in and fell in love with her immediately. Sadie loved everyone and, in typical Lab style, enthusiastically invaded the personal space of anyone who met her, saying hello by sticking her nose straight into their crotch area. While this made perfect sense to Sadie — she was simply gathering information about them through their unique scent signatures — it caused untold amounts of embarrassment for our guests and drew numerous apologies from us. We love our dogs, but sometimes their behavior is not socially acceptable and can be downright embarrassing, especially when guests come into the home. Is your dog embarrassing in front of guests? There are ways you can prevent and change these behaviors.
Use a baby gate to keep your dog contained, preferably one that lets your dog see your visitors. Photography courtesy Melissa Kauffman.
The best way to deal with any faux pas is to put a management plan in place before you do any training. Think about how you can change your environment to prevent the behavior from happening in the first place. The less your dog can practice the behavior, the easier it will be to change it.
Some management tips include:
For dogs who like to sniff certain delicate areas, hang a bag with an even more enticing smell outside the door, such as liver or a hot dog, and have the person hand feed or toss treats toward the dog on the ground as they enter. This is sometimes called the Go Find It game and is a great way to put a dog’s energy into searching for something else than saying an embarrassing hello.
If your guests do not want to handle food, you can play the game with your dog as your guest comes in. You can also teach your dog a “leave it” cue and then redirect him to something else such as a toy or treat, or you can teach him to target a person’s hands for a treat/petting as an alternative.
I taught Sadie to grab one of her toys and show it proudly to my guests instead of sniffing their “regions of interest.” Any other incompatible behavior like rolling over for a belly rub or running and sitting on a mat can be put on cue. Practice makes perfect!
Humping is another embarrassing dog behavior and occurs when dogs get overexcited or anxious, so try to limit your dog’s arousal levels by teaching calming behaviors including “settle.”
Learn more about dog body language that can help predict when your dog is getting excited, and teach him an alternative behavior before the humping occurs. You can also advise visitors on how to be calm in your home to set your dog up for success and not raise the level of his excitement, frustration or anxiety.
Small children tend to get humped first. If you know you have young ones coming over, have a special toy at the door they can give your dog when entering. If your dog is kid friendly, have two toys so that older children can toss one after the other (while avoiding taking the toy from the dog).
Show younger children how to stand still and “be a tree” to help set the dog up for success and limit his exuberance around greetings. You can show kids how smart your dog is by teaching him another behavior such as walking away and lying on a bed, doing a play bow or some other kind of activity that encourages your dog’s energy to go elsewhere.
One of the biggest faux pas dogs make is when they toilet in a home they are visiting. Be sure your dog has eliminated before arriving at a friend’s home, or ask that the same thing be done before a friend’s dog comes over to yours. Keep your dog in a smaller space, such as a tiled kitchen until he is relaxed.
Avoid vertical surfaces or expensive rugs, and keep your dog tethered to you until he is calm in the new environment, and you are sure he will not eliminate. Explore new environments together to prevent marking in new places. If you know your dog is likely to mark, allow him some playtime in the backyard first before coming inside.
Following these few simple guidelines will set your dog up for success and save you from having to endure embarrassing situations.
Tell us: Is your dog embarrassing in front of guests? Does your dog hump, jump or sniff your company? How do you handle it?
Plus, what if your dog snaps at a guest? Whole Dog Journal tells you how to handle the situation>>
Thumbnail: Photography ©madcorona | Thinkstock.
Victoria Stilwell, renowned dog trainer, TV personality, author and public speaker, is best known as the star of the hit TV series It’s Me or the Dog, through which she reaches audiences in more than 100 countries. Appearing frequently in the media, she’s widely recognized as a leader in the field of animal behavior, is editor-in-chief of positively.com, CEO of the VSPDT network of licensed trainers and the founder of the Victoria Stilwell Academy for Dog Training & Behavior — the leader in dog trainer education. Connect with her on Facebook and on Twitter at @VictoriaS.
Editor’s note: This article appeared in Dogster magazine. Have you seen the new Dogster print magazine in stores? Or in the waiting room of your vet’s office? Subscribe now to get Dogster magazine delivered straight to you!
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