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Whenever I would take flash photos, or when my dog's face is shone in light, his right eye would reflect greenish light. The other eye has no reflection of light at all. I hadn't really thought about it until yesterday night.

I turned off all the lights, so that it was really dark. I turned on the flashlight on my cell phone, and flashed it in his eyes to check if it's only one eye that reflects. This time I'm sure it's only his right eye that reflects the greenish light.

Is there any reason I should be concerned about it only being his right eye reflecting greenish light?

I want to go to the vet for check-up but I heard it's expensive so... I want to know if it's okay or not... then I'll decide to go to the vet :) Thanks.

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  • Does your dog have blue eyes, by chance? – augurar Dec 28 '14 at 8:14
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The green shine is caused by tapetum lucidum. My Dachshund has it as well, although in both eyes, and the shine is actually very dim. As to your dog's differing appearance of her eyes,

Found on a forum called the Naked Scientists:

I'll have a go at it...

Here's what we know. The tapetum lucidum, formed by the choroid at the back of the eye, is wedged between layers of blood vessels on either side but itself is avascular. It is responsible for reflecting light of various colours, producing the characteristic iridescence seen in flash photography of animals and in front of car headlights, and is believed to be a nocturnal adaptation by increasing stimulation of the photosensitive cells of the retina.

In dogs and cats, the tapetum is made up of cells. These cells contain crystalline rods that are arranged in such a way that they split the light that hits them into its various colour components. A similar effect is seen in herbivores, but the structure of the tapetum varies in that it is fibrous (collagenous) rather than cellular, and it is the arrangement of the collagen fibres within the structure that is responsible for splitting light. The tapetum is absent in humans and pigs.

So here's what I think might be happening:

1) The eye that appears red lacks a tapetum lucidum and the result is the typical 'red-eye' seen in humans due to the appearance of the blood vessels of choroid and the underlying the cornea.

2) The dog has different crystalline or cellular arrangements in its eyes causing the reflected light to correspond to the different wavelengths. Interestingly, tapetum appears a blue-green colour in the Dutch sheep dog but an orangy colour in the Old English sheepdog.

3) The dog is slightly bung eyed and light is hitting the structure at a slightly different angle in one eye than in the other, affecting the way the light is reflected (but being an appauling physicist, I have no idea whether or not that is valid.)

So, my guess would be that your dog has tapetum lucidum in one eye and not the other, or he has it in both eyes, but one of them is a "lazy eye" or angled slightly differently, so the shine does not occur at the same angle when viewed by you. (More probably the first).

Edit: I now realize that I never really answered your question. No, there is no worry due to the single eye shine. Your dog will be able to see a minor bit better in very low light in the eye with the shine, but it should not affect his overall health.

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The greenish light you're seeing is a reflective layer of tissue found in most animals that have evolved to see in the dark called Tapetum lucidum. The way it allows animals to see better in the dark, is by increasing the amount of light the eyes can use through reflection.

The tapetum lucidum /təˈpiːtəm/ (Latin: "bright tapestry", plural tapeta lucida) is a layer of tissue in the eye of many vertebrates. Lying immediately behind the retina it reflects visible light back through the retina, increasing the light available to the photoreceptors, though blurring the initial image of the light on focus. The tapetum lucidum contributes to the superior night vision of some animals.

Source: http://en.wikipedia.org/wiki/Tapetum_lucidum

Diagram of a cat's eye (Source)

So, when you shine a light in the eyes of an animal, if they have the Tapetum lucidum in their eye, their eyes can appear to shine in different colors depending on the way the light reflects against it.

Some of the common colors you can see from eyes are green, yellow, and blue, except for animals that don't have the Tapetum lucidum, their eyes appear red. That's how you happen to get the red-eye effect when photographing humans.

As for your question about why one eye might have this effect, while the other one doesn't. My best guess is that it's genetic, and the the Tapetum lucidum in the left eye is smaller, or a different shape to where it doesn't refract light in the way that you would be able to see it.

I wouldn't say that it's an emergency that you have to take your dog to the vet immediately for, but I would definitely bring it up the next time you take him in.

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  • There are some factual errors in this answer. 1) The tapetum lucidum does not "amplify" light, it merely reflects it back past the retina so it has greater chance of stimulating the photoreceptors. 2) The reason for the colors is not refraction but iridescence caused by thin film interference. – augurar Dec 28 '14 at 8:19
  • Basically, by reflecting the light it gives the photoreactive chemicals in the retinal cells a second chance to grab and react to the photon, if it was perfectly reflective that would double the eye's sensitivity to low light levels; it isn't that good but it does help. Now if only mammalian eyes were as well-designed as those of octopi, and didn't block part of the light with blood vessels... – keshlam Jul 17 '15 at 4:31
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Please have your dog's eyes checked by a veterinarian. I fostered a dog with dry eye. She lost her sight in one eye, that eye did not reflect light. If your dog has one eye that does not reflect light, his sight in his other eye is even more important. Make sure he does not need an inexpensive medication ($20/month) to save his vision in his other eye from dry eye. If this is the case, both eyes should be treated, since the condition is painful.

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  • I agree, it should be checked. His eye should reflect light. You should get some kind of shine showing that he has a healthy retina. That's how doctors tell quickly if a human's eye isn't healthy, no retinal reflex. No shine. Please get him checked. – user5973 Oct 19 '15 at 17:45

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