Anatomy and Review of the Eye Flashcards

1
Q

What kind of animals have a closed orbit?

A

Herbivores

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2
Q

What kind of animals have an open orbit?

A

Carnivores

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3
Q

What should a healthy eyelid look like?

A

Smooth edges with a continuous line from medial to lateral canthus. Should sit flat against the eye (small gap is normal in some breeds). Lower eyelid has no hairs

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4
Q

What are the white dots along the eyelid edge?

A

Meibomian gland openings

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5
Q

What is the function of the meibomian glands?

A

Secrete oil onto the eye forming the oil layer of the tear film to prevent the eye from drying out.

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6
Q

What is a sty?

A

An infection of the meibomian glands

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7
Q

What does the third eyelid look like?

A

Positioned at the medial canthus. Can be pigmented or not or a variation of pigmentation

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8
Q

What is the third eyelid made up of?

A

Fold of conjunctiva with a cartilaginous core to hold its shape and a tear gland buried deep in the medial edge

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9
Q

What differences are there between cat and dog eyes?

A

Cats don’t have proper eyelashes. Can often see third eyelid. Eyelids cover edges of cornea and common for proteins/dirt to sink below lower eyelid

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10
Q

What does the conjunctiva cover?

A

Lines the eyelid, folds back at conjunctival fornix, covers the globe, stops at the limbus

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11
Q

What is the limbus?

A

Junction between cornea and sclera where the conjunctiva fully attaches to the sclera

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12
Q

Why is the limbus clinically important?

A

If there is a lot of pigment a chronic irritation can cause proliferation of pigment which migrates across the cornea and obscures vision

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13
Q

What is the Perkinjee reflexes? How are they used clinically?

A

Reflection of light off the cornea. can use it to judge the surface

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14
Q

What are the outer layers of the eye?

A

Sclera, cornea and limbus

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15
Q

What makes up the uvea?

A

Iris, ciliary body, choroid

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16
Q

Which way does the equator of the eye run?

A

Runs the edge of the lens and splits the eye into anterior and posterior chamber

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17
Q

What makes up the posterior segment?

A

Vitreous cavity filled with vitreous humour

18
Q

What makes up the anterior segment?

A

Anterior chamber (between cornea and iris) and the posterior chamber (between iris and lens)

19
Q

What are the three zones of the iris?

A

Pupillary zone (closest to pupil), cilliary zone (outside of iris covering cilliary body) and iris colourette (inbetween two zones)

20
Q

What are persistent pupillary membranes (PPMs)?

A

Remnants of blood vessels of foetal vasculature that should have disappeared at 2 weeks and arise at iris colourette

21
Q

What are synechiae?

A

Adhesions to cornea/lens from iris colourette. Classed as either anterior/posterior depending on where they attach

22
Q

What is the function of the iris?

A

Opens and closes in response to light

23
Q

What are the different shapes of the iris/pupil in animals?

A

Dogs = round
Cats = slit
Horses and ruminants = letterbox

24
Q

What is the granular iridica?

A

Granular dark black epithelial material in horses eye

25
Q

What is the function of the ciliary body?

A

Produces aqueous humour and has powerful muscles which help with focusing of the lens

26
Q

What is the position of the choroid?

A

Sandwiched between the retina and sclera

27
Q

What is the function of the choroid?

A

Provides extra blood supply to the retina

28
Q

What is the tapetum?

A

Orange colour under the retinal vessels

29
Q

What can you see if the choroid has no pigment?

A

Can see red stripes (blood vessels) and white of the eye behind it

30
Q

What holds the lens in place?

A

Zonials

31
Q

What are the different parts of the lens?

A
Capsule = external part
Cortex = thin layer below the capsule
Nucleus = centre of the lens
32
Q

What is the function of the cortex?

A

Has active cells making fibres which are added to the nucleus and as more fibres are made the nucleus condenses

33
Q

What is nuclear sclerosis?

A

As the nucleus condenses less light can pass through so it appears opaque

34
Q

What is nuclear sclerosis often confused with?

A

Cataracts

35
Q

What is the retina?

A

Innermost layer of the eye made up of numerous layers and cells

36
Q

What are the two types of photosensitive cells and what are their function?

A
Rods = night vision, no good contrast, no good colour, no good definition
Cones = day vision, good contrast colour and definition
37
Q

What is the fundus?

A

Brown colour with retinal vasculature, optic disc and tapetum lucidum

38
Q

What indicates retinal changes?

A

Changes in yellow-green tapetum/brown area

39
Q

How is the equine fundus different?

A

Very large salmon optic disc with several very small blood vessels coming out about 0.5mm with not very many ventrally. Not very shiny/colourful tapetum

40
Q

How many layers of the retina are there?

A

10
9 neurological
1 epithelial

41
Q

What is the clinical significance of the retinal pigmental epithelium?

A

Can become diseased and is left behind in retinal detachment

42
Q

Where does the aqueous humour exit and what is its clinical significance?

A

Iritocorneal junction. If disease affects angle drainage is affected can change intraocular pressure = glaucoma