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Hygiene

Questions

Hygiene

9.5 The structure of the eye


The dog's eye

The eye is one of the organs responsible for vision. It is part of what is known as the visual system.

The eye, or ocular globe, is a spherical structure, covered and protected by the eyelids.

Eyelids: dogs have three eyelids: the lower and upper eyelids (like humans) and the 3rd eyelid, also known as nicitating membrane. These eyelids contribute to the protection of the eye by acting as windshield wipers: with the help of tears, they bring dust and other dirt into the corner of the eye, from where it is eliminated.

Tear glands: Tears, despite their mundane appearance, are constitutive of a complex and efficient protection mechanism known as the tear film! Along with the eyelids and the tear evacuation ducts, they form the lacrimal apparatus. These tears are produced by different glands: the tear gland; the superficial gland of the 3rd eyelid or nicitating gland; the tarsal glands or meibomian glands, and finally the gland of the conjonctival fornix. Each of these glands is necessary for the creation of an effective tear film!

Tear ducts: Tear ducts collect the tears and prevent them from running along the hair located under the eyes. These ducts end in the nose.

Cornea: The front of the ocular globe is bordered by the cornea, which acts as a porthole. It is approximately 1mm thick.

Iris: The iris, of variable colour, contains muscles that modify dilatation, or the opening of the pupil.

Pupil: Contrary to a cat’s pupil, dogs’ pupils are always round regardless of whether they are dilated!

Crystalline lens: The crystalline lens acts as a lens and thus enables clear vision. The space between the cornea and the lens is made up of a liquid called aqueous humour. This liquid maintains a certain pressure inside the eye, thus giving it its spherical shape.

Vitreous humour: Behind the lens is a viscous gel, the vitreous humour.

Retina: Finally, the retina collects the images having crossed all of the eye’s structures and transforms them into nervous impulses. These are then transmitted to the optical nerve that in turn sends this information to the brain’s visual cortex.

Dilation of the pupil: The iris contracts or dilates principally according to luminosity. In full light, the pupil shrinks: this is called miosis. In the dark, its diameter significantly increases: this is called mydriasis.

Questions

That you ask yourself about your companion

9.1 Why clean my dog's eyes?


9.2 When and how regularly should I clean its eyes?


9.3 How and what should I use to clean its eyes?


9.4 When should I see my veterinarian?