Dog Eye Anatomy
Dog Eye Anatomy is a reflection of the eye as a complicated organ,
containing many parts. These functional parts, i.e. sclera,
cornea, iris, pupil, lens, retina, lacrimal gland etc. are contained in
a bony socket called a “orbit”. Along with these dog eye parts,
vessels, nerves and tear drains are also part of the orbit, which play
important role in the normal functioning of a dog eye. Along with other
eye problems, there are various conditions which are related to
abnormal canine eye anatomy. These conditions are mostly treated with
minor to major surgical procedures along with the use of specific
therapeutics and supportive remedies, such as natural extracts to
Dog Eye Anatomy Diagram
This picture is reprinted with permission by the
Pet Nutrition, from the Atlas of Veterinary Clinical Anatomy. These
illustrations should not be downloaded, printed or copied except for
Functional Layers of a Dog Eye:
On basis of function, the dog eye has three different layers:
- Fibrous Tunic: This part forms the outer
most opaque layer and is comprised of collagen
and fibrous tissues, called sclera. Sclera majorly forms the posterior
eye, while anterior or the front part of the eye is the cornea, which
transparent and allows entry of light into the
- Vascular Tunic: The dog eye is supplied
with blood vessels, which
supplies oxygen and nutrients to the all parts of the eye through the
The major part of the vascular tunic comprises a network of blood
also the choroid, which lies beneath the sclera, which helps in
adjustment of the lens and “accommodation” or muscular constriction and
relaxation which controls light. It is believed that this muscular
mechanism is influenced by the vascular supply in the eye.
Tunic: This functional part of the eye is controlled and is
the nervous system of the dog eye anatomy. Photoreceptor cells called
“retina” lies on
the whole round wall of the posterior eye. These are controlled by
retina, which collects and identifies the light, which is then
processed to the brain with help of the “optic nerve”. The “Blind spot”
Disc” is the dark spot on the retinal wall, which has no photoreceptor
cells over it and this part opens into the optic nerve duct, which
a rich nerve supply, that connects the eye with the brain.
The aforementioned layers are functional layers of dog eye anatomy.
of the eye is made possible with various anatomical features,
which includes the, eyelids, eyelashes, conjunctiva, cornea, iris,
lens, third eyelid (nictitans gland) lacrimal gland and viteous chamber
of the eye.
following is a brief functional overview of these parts of dog eye
- Eyelids and Eyelashes: These are the
outer most protective layers of the dog eye anatomy, which
are flexible and wipe the tears over the eye surface to keep it
and away from foreign particles such as dust and debris. The eye
is an involuntary action, which is controlled by
the brain nerve supply. These parts also help to control light rays
entering the eye.
- Conjunctiva: Tough outer protective
layers of the eye, the sclera is covered
by a thin membrane, called conjunctiva. This thin membrane is located
near the front of the eye. Conjunctiva runs over the cornea and covers
all of the inner parts of the eyelids.
- Cornea: The cornea is the central dome
shaped area of the eye surface, which is
supposed to be a pathway for light entering into the eye. The cornea
only functions as a protective part of the inner eye but also it
light on the retina at the back of the eye. The focusing and light
control function of
the cornea is facilitated by the iris.
- Iris: This is the circular colored area
of the eye, which controls the
amount of light entering into the eye. Due to the functionality of this
the pupil gets smaller or larger. The pupil is the central black area
eye, which dilates or constricts under the influence of the iris and
environment, to let more or less light entering into eye. The pupil
in a darker environment and constricts in a bright environment to
control and allow an
adequate amount of light to enter the eye.
- Lens: The lens lies just behind the iris
of the eye, which is meant for
focusing nearby or distant objects on the retina. The function of the
controlled by the ciliary muscles (small muscles) which contract,
the lens to become thicker and nearby objects more focused. On the
hand, if the ciliary muscles relax, the lens becomes thinner and thus
distant objects are focused on the retina.
- Retina: These are photoreceptor cells,
which are distributed over
the round back surface wall of the eye. The most dense part of the
photoreceptor tissues or retina of the dog eye are called area
In this region, thousands of photoreceptor cells are packed making the
incoming images sharper. Each retina photoreceptor cell is
attached with a nerve, which enters into the optic duct, through the
and is connected to the brain. All the minor optic nerves of the retina
bundled into a larger optic nerve. Retinal tissues convert images into
electrical impulses, which are carried to the brain with the help of
- Nictitaing Membrane:
In dogs, the eye is not only protected by the eyelids,
but also with a nictitating membrane, which is also called the third
eyelid. This is whitish to pink in color and is located on the edge of
the inner part of the eyelids, near the nose. This membrane extends to
the surface of
the eye when the protection is needed or when the eye ball becomes
scratches, irritation and in case of inflammation.
- Lacrimal Glands: These
are tear producing glands. Tears keep the
dog eyes wet and lubricated. Debris, dust etc is flushed out of the eye
the help of these tears. There are two types of Lacrimal glands, of
lacrimal glands produce watery content or tears and the mucous glands
conjunctiva produce mucous which mixes with tears to forms the
nature of tears, as antibacterial or the slippery nature of tears wipe
out of the eye. Also the mucous part of the tears helps in preventing
rapid evaporation. Tears are drained with the help of nasolacrimal
which open into the nose.
Dog Anatomy and Dog Eye Health
In addition to a sound AAFCO certified diet (check the label),
a dog may benefit
from homeopathic remedies and dog eye cleaning during grooming to support dog eye anatomy.
Homeopathic remedies can be used to promote dog eye health,
severity of symptoms during a dog eye problem and safely eliminate any
dog tear stain issues. Products used
should be from a reputable manufacturer and formulated specifically for
the Eye or surrounding areas. Two products that fit these
criteria include Eye
Heal which is the edges of the eye and
which can help clean around the eye such as dog eye stains.
In terms of a dog
eye wash, use an isotonic solution (isotonic means that the
solution matches the biology of the dog eye) when needed such as the
product offered by PNP.
Many owners, as part of the grooming schedule will wash and
check the eyes for any debris, infection or other issues.
Other times a dog eye wash is used is to remove any chlorine, debris
or salt water after swimming.
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References for Dog Eye Anatomy:
Veterinary Manual (Merck & Co.)