This is due to a structure in the back of the eye called the tapetum lucidum. This is a reflective layer in the back of the eye that sits just in front of the blood filled layer called the choroid. The job of this layer of the eye is to reflect light back onto the retina a second time to amplify light in dark conditions. The color of the tapetum and its reflection can vary from a green, blue, orange or yellow hue. This coloration often changes over the first 3 months of life. Some dogs, similar to humans, do not have a tapetum. This is most common in dogs with blue eyes. Thus, when a photograph is taken, the tapetum is not present to create the colored reflection and therefore the red blood vessels in the back of the eye are visualized. This creates the “red eye” look.
If you notice a change in how your dog’s eyes are reflecting over time (duller or brighter) or there is a difference in the reflection between eyes, it is advisable to have the eyes examined. It could indicate an eye disease that needs to be addressed.
Have you ever noticed that when you look at your dog or cat’s eye in the dark, they glow a yellowish/green color? Have you ever wondered why your pet doesn’t get “red eyes” in photographs?
Why Are Dogs Eyes Reflective?
Dogs’ eyes glow in the dark for the same reason cats’ eyes glow too – it’s because of their night vision. Simply put, nocturnal and cathemeral (active both during the night and day) animals have reflective eyes to help them see better under reduced visibility.
The way that works is that these animals’ eyes have a reflective surface at the back of the eye. This surface is called a tapetum lucidum and it’s located between the optic nerve and the retina. The purpose of the tapetum is precisely to reflect all incoming light back through the eye. This helps the dog see better because the light has to go through the eye’s visual cells (eye cones and rods) a second time.
Essentially, the tapetum lucidum gives the dog’s eyes a second chance to detect any information in the light they’ve seen, no matter how dim it is. The fact that the light is then reflected out of the eye, while spooky, is just a side-effect.
The reason the tapetum lucidum is reflective is due to the presence of zinc and/or riboflavin in the pigment of its cells. As Dr. Cynthia Powell of the Colorado State University explains it “Zinc is a metal, and riboflavin is an amino acid and both act as reflective agents. Depending on how densely packed these cells are with zinc or riboflavin, the glow color can vary from animal to animal and breed to breed.”
Do All Dogs’ Eyes Glow the Same?
The tapetum is a unique biological feature. Like anything else on a dog, it doesn’t develop exactly the same way in every dog. It’s another thing that makes your pup unique!
Some dogs have a larger tapetum than others. Furthermore, the cellular makeup can vary. Remember: The tapetum tissue gets its reflectivity from zinc or riboflavin.
In some dogs, the tapetum has more zinc. Others might have more riboflavin, while others have a healthy mix of both.
Interestingly, some dogs don’t have tapetum at all! Recent estimates show that around 1.9 percent of dogs lack the tapetum. It’s a small percentage, but they exist.
As you probably guessed, those dogs don’t have night vision. But their eyes can still glow in the right conditions as light reflects off the blood vessels in the back of the eyes!
Overall, the color of that signature eye glow varies based on the cellular makeup of your dog. Factors like breed, eye color, and coat color come into play.
So what color can you expect to see from your dog’s eyes?
Below is a general color chart to give you a better idea of the color variation. It includes some popular breeds and coat colors. These colors are the norm. However, there are no guarantees.
There are some canine outliers with unique tapetum tissue. If anything, use this color chart as a loose guide rather than concrete scientific evidence.
Curious about puppies? If you spend a lot of time around young dogs, you know that their eyes change dramatically as they grow. You can’t even see their eye color at birth because they keep them close for several weeks!
When they finally crack those eyes open and look into the world for the first time, the eyes are noticeably brighter than adults of the same breed.
The eyes lack pigmentation for several months. Eventually, they develop into the dog’s “true” eye color. As you can imagine, the color of the reflected glow differs, too.
The glow is usually the same as blue-eyes dogs when the eyes are light and pigment-free. It’s orange or red. The color will gradually change over several weeks and months.
By the three-month mark, most puppies are at their final color. The same goes for the reflected glow.