Introduction Flashcards
Characteristics of eyes of predator species
1- Carnivore
2- Frontal globe position
3- Greater binocular vision
4- Open bony orbit: the ramus of mandible imposes on the orbital area when the mouth is opened; cellulitis in this area is quite painful when opening the mouth.
Characteristics of eyes of prey speices
1- Herbivore
2- Lateral globe position
3- Greater peripheral vision
4- Closed bony orbit: more protection for the eye
Clinically important characteristics of orbital anatomy of predator species
Open bony orbit: the ramus of mandible imposes on the orbital area when the mouth is opened; cellulitis in this area is quite painful when opening the mouth.
Lashes (cilia) of dogs and cats
dogs have 2-4 rows of upper lashes; cats have no true lashes
Lashes (cilia) of rabbits
rabbits have upper and lower lashes
Pupil shape
canine = round; domestic feline = vertical; herbivore = horizontal
What holds the third eyelid in place?
It is generally retracted and held in place by sympathetic tone.
Species that lack a tapetum
Occasionally cats and horses lack a tapetum. The tapetal color is loosely associated with coat color. The pig, camelids, red kangaroo and birds do not have a tapetum.
Location of the tapetum
Most domestic species have a reflective tapetum located in the superior fundus within the choroidal layer.
Ossicles
These bony scleral structures are found in birds, some reptiles and amphibians and give support to the outer fibrous tunic.
When do puppies and kitties open their eyes
puppies and kittens open their eyes at 10-14 days
When do ferrets and guinea pigs open their eyes?
the guinea pig at birth and the ferret at 30 days.
Adexa
refers to the tissues surrounding the eye (muscles, eyelids, 3rd eyelid, lacrimal gland, fat, nerves, vessels etc.).
Muscles of the eye
rectus, oblique, retractor, smooth muscle
rectus muscles and innervation
Dorsal, Ventral, Medial (innervated by CN III-oculomotor)
Lateral (innervated by CN VI-abducens)
Oblique muscles, actions, and innervation
Dorsal Oblique; (innervated by Crn IV-trochlear): rotates dorsal globe
medially and ventrally
Ventral Oblique; (innervated by Crn III-oculomotor), rotates the ventral
globe medially and dorsally
Innervation of the retractor muscle
(innervated by Crn VI-abducens); not found in the bird
smooth muscle of the eye is under what control?
sympathetic
3 layers of the eye
Outer fibrous tunic (cornea & sclera)
Middle vascular layer- Uvea (iris, ciliary body & choroid)
Inner nervous layer (retina)
Outer fibrous tunic
(cornea & sclera)
Middle vascular layer-
Uvea (iris, ciliary body & choroid)
Inner nervous layer
(retina)
What produces the aqueous humor?
This clear fluid, produced by the ciliary processes (located behind iris)
Flow of aqueous humor
passes through the pupil into the anterior chamber and exits the eye via the iridocorneal angle (ICA)
Function of aqueous humor
It provides nourishment for the cornea and lens and maintains intraocular pressure.
How to visualize the aqueous humor in the dog, cat and horse?
ICA can be visualized using a goniolens in the dog but can be seen by viewing obliquely across the cornea in the cat, and directly at the medial and lateral limbus in the horse.
vitreous
This is the largest area of the eye.
What is vitreous humor
Vitreous humor is a clear gel-like fluid that occupies the space between the lens and the retina. It gives both nutritional and structural.
support to the lens and the retina.
Retina
The inner nervous layer of the eye
When can the retina been seen?
can only be visualized if the cornea, aqueous, lens and vitreous are transparent.
Retina is made up of what?
It is composed of axons of the retinal ganglion cells that converge to form the optic nerve.
