Many dog owners wonder whether dogs are nearsighted. This is a great query after all since it can allow us a deeper understanding of man's best friend.
There is recently a lot of interest in discovering how dogs perceive the world around them. This can ultimately make us better owners, since knowing how well a dog can see can help us better understand them.
Is Nearsightedness the Same as Myopia?
Yes, nearsightedness is the same as myopia. Nearsightedness is a common vision problem where the affected animal or person would see nearby objects clearly, but struggles seeing objects farther away. Such far-away objects would therefore appear blurry.
In humans, nearsightedness is easily diagnosed through the use of a special vision test, where a person is placed at a distance from a chart featuring letters.
The chart is known as the "Snellen eye chart" to honor its inventor the Dutch ophthalmologist Herman Snellen, who developed it in 1862.
This eye chart simply consists of eleven lines of letters, with the first line displaying a single very large letter and subsequent rows having more letters that become increasingly difficult to read since they gradually decrease in size.
The person being tested will cover one eye and stand 6 meters or 20 feet away and attempt to read the letters aloud. The last row the person can read with accuracy reflects the visual acuity of the open eye.
Testing Dogs for Nearsightedness
While dogs obviously cannot read the eye charts developed by humans, there are other tests that can be conducted to determine how well or how bad dogs can see. This would require a visit to a specialist who can examine the dog's visit using specialized tools.
The specialists in the field are veterinary ophthalmologists, ideally Diplomates of the American College of Veterinary Ophthalmologists (DACVO).
Such specialists can measure a dog's nearsightedness and farsightedness using a special tool that is known as a retinoscope.
A retinoscope shares the same technology as retinoscopes used to test vision in small children or humans who cannot communicate verbally.
So Are Dogs Nearsighted?
Interestingly, when a dog's vision is tested, it often turns out that the dog is neither near-sighted nor far-sighted, however there are various exceptions to the rule.
For instance, it has been found that certain breeds of dogs are predisposed to vision problems. The onset of such vision problems seems to be correlated with aging.
This seems to be the opposite of what happens in humans, considering that as humans age, they tend to become more farsighted meaning that they struggle seeing near objects with clarity (hence, why with age, many people must rely on reading glasses).
In one particular study, conducted on beagles by a team of researchers, an autorefractor (a reliable alternative to retinoscopy) was used to measure the beagles' vision in order to detect changes that occur as a result of aging.
The findings suggested that, yes, dogs become more near-sighted as they age. Indeed, just as it happens in humans, dogs appear to experience ocular changes associated with aging such as the hardening and clouding of the lens and the accumulative oxidative damage from UV sunlight.
What Dog Breeds are More Likely to Become Nearsighted?
More studies have been conducted on dogs and their predispositions for nearsightedness. In particular one study tested various breeds for their predisposition for developing myopia.
One particular study conducted by Murphy and colleagues (1992) revealed that German Shepherds, Rottweilers, and Miniature Schnauzer breeds had an increased prevalence of myopia, especially in older dogs with nuclear sclerosis.
In particular, 64 percent of the tested Rottweilers, 50 percent of the tested Miniature Schnauzers and 53 percent of the tested German shepherds resulted being myopic.
Interestingly though, among the German shepherds participating in a guide-dog program, only 15 percent were found to be affected by the condition.
This may suggest that German shepherds with poor focusing abilities had been screened out from the guide-dog program due to behavioral shortcomings occurring during their training.
For sure, with this data in mind, it becomes fundamental testing dogs for myopia before enrolling them in certain canine sports or employing them for various utilitarian tasks where acute vision is important.
Other dog breeds with a significant prevalence of myopia include English Springer Spaniels,Toy Poodles and Collies.
- Hernandez J, Moore C, Si X, Richer S, Jackson J, Wang W (2016) Aging Dogs Manifest Myopia as Measured by Autorefractor. PLoS ONE 11 (2): e0148436. doi:10.1371/journal.pone.0148436
- Myopia and Refractive Error in Dogs, Investigative Ophthalmology & Visual Science, Vol. 33, No. 8, July 1992. Christopher J. Murphy,* Karla Zodnik,^ and Mark J. Mannisf.
- Mutti D.O, Zadnik K, Murphy C.J. Naturally occurring vitreous chamber-based myopia in the Labrador retriever. Invest. Ophthalmol. Vis. Sci. 1999;40:1577–1584.
- Kubai M.A, Bentley E, Miller P.E, Mutti D.O, Murphy C.J. Refractive states of eyes and association between ametropia and breed in dogs. Am. J. Vet. Res. 2008;69:946–951
- Steven Lindsay, Handbook of Applied Dog Behavior and Training, Adaptation and Learning