As humans age our vision changes. These changes are often slow to develop, but eventually, we reach a day where we find ourselves struggling to read the small print on a menu in front of us. Are humans the only species that experience this, or do dogs also have age-related vision changes?
While humans tend to become more farsighted as they age, it turns out our dogs become more nearsighted. A study by the team at Nestle Purina Research Center found that as dogs age, objects far away become more blurry; in other words, they become more nearsighted.
To determine this, the research team used an autorefractor to measure the optical status of 12 beagles between the ages of 1 and 14. Over the course of the study, each dog underwent five measurements under direct and indirect light for each eye, for a total of 20 daily eye measurements.
What they found was that there was a significant difference in the eyesight of the young and senior dogs. When measuring changes in the eye, a unit of measurement called a diopter is used. Diopters measure the refractive error of the eye that is causing the vision impairment.
A positive refractive error means that the eye is farsighted whereas a negative refractive error means that the eye is nearsighted. In the study, the dogs between the ages of 10 and 14 were measured of having refractive errors around -2.5 diopters.
Unless you’re an eye specialist, you probably can’t even begin to imagine what a refractive error of -2.5 diopters actually looks like. That’s where pictures come in!
Looking at the eye tests above, dogs with -2.5 diopters see somewhere between the 2D and 3D chart.
When humans start to experience age-related eye changes, we have the option to purchase corrective glasses. Unfortunately, dogs do not have the same luxury – at least not yet; but can you image how adorable doggy glasses would be?
As your dog ages, keep in mind that vision is one of the changes their body will be going through. Making sure that you use a combination of vocal and hand signals, and not standing too far away when you use hand signals, are easy ways to ensure your dog’s changing vision has as little impact as possible.
H/t to Psychology Today