7563247
Description
Flashcards by Rachael Jones, updated more than 1 year ago
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Created by Rachael Jones
almost 8 years ago
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| Question | Answer |
| What is another name for the globe? | Bulbus oculi - "eyeball" |
| What surrounds the globe? | Housed in orbit in lots of fat |
| What does the position of the eye relate to? | Feeding methods/habit/environment |
| What is the result of the position of the eye for a predator species? | Eyes set forward Large field of binocular vision for depth perception Small monocular vision so very little detail of surroundings |
| What is the result of the position of the eye for a prey species? | - Eyes set on side of head - Large field of monocular vision for surrounding vision - Small binocular vision for depth perception |
| What do the anterior and posterior poles relate to with the eyeball orientation? | Anterior: highest point on cornea Posterior: Highest point on sclera |
| What are the 3 layers of the eyeball, that reflect that it is an embryonic growth from the brain? | 1. Outer Fibrous tunic 2. Middle Vascular tunic 3. Inner Nervous tunic (retina) |
| What is the fibrous tunic made from? | Cornea and sclera - only complete layer of the eye |
| What is the point where the cornea and sclera meet called? | Limbus or corneo-sclero junction |
| Give 5 features of the cornea. | 1. Bulges forward due to radial difference with sclera 2. Transparent due to structure and physiology 3. No blood vessels 4. Refracts light more than lens in domestic species 5. Very sensitive due to free nerve endings |
| What are 2 features that come with the cornea being avascular? | 1. Takes time to heal 2. Can be transplanted with reduced rejection |
| Why is the cornea very sensitive? | Free nerve endings of ophthalmic division of trigeminal nerve |
| What are the pectinate ligaments? | Space between fibrous and vascular tunic and allows drainage or blood and aqueous humor |
| What is another name for the posterior corneal epithelium? | Descemet's Membrane |
| What can be done to heal corneal ulcers? | Antibiotics and protein inhibitors Pedicle conjunctiva graft |
| What can sometimes be found associated with a corneal ulcer? | Bulge of tissue known as descemetocele |
| What is the sclera? | 'White of the eye' - dense collagen fibres |
| What can be found in the sclera? | 1. Pierced by vorticose veins and small ciliary arteries 2. Has cribiform area where fibres of optic nerve pass |
| What does the cribiform area create? | 1. A weak spot 2. Optic nerve has connective tissue sheath: continues dura mater to sclera |
| What is the issue associated with the cribiform area? | Infection of the eye can back track to the brain and result in meningitis |
| What do the anterior ciliary arteries supply? | Conjunctiva and sclera |
| What are the anterior ciliary arteries and long and short posterior ciliary arteries branches of? | External ophthalmic artery which is a branch off the maxillary artery |
| What happens when there is inflammation in the eye? | Blood vessels become congested and more prominent |
| In the conjunctiva, which of the small visible blood vessels move more freely? | Bulbar conjunctiva |
| Where is the vascular tunic (uveal tract) located? | Deep to the sclera |
| What does the vascular tunic do? | 1. Controls size of pupil 2. Suspends lens and regulates its curvature 3. Produces aqueous humour 4. Supplies blood |
| What does the iris divide? | Space between lens and cornea into: 1. Anterior chamber 2. Posterior chamber |
| What is found in the iris? | Watery liquid that allows refractive properties |
| What does the colour of the iris depend on? | Number of pigmented cells - lots of melonin = dark brown - no melonin = blue |
| What is a blue horse iris called? | Wall eye |
| What can be found in ungulates in their iris? | 'Iridic granules' possibly for UV protection or movement sensor |
| What happens when there is no pigment at all in the eye? | Appear as red/pink due to the blood vessels |
| What doe the muscles in the ciliary body do in primates? | Accommodates lens |
| What extends from the ciliary body? | Ciliary processes which themselves have zonular fibres that attach to lens equator |
| What is another term for zonular fibres? | Suspensory ligaments |
| How is the accommodating power of the lens measured? | Diopters |
| What do the ciliary processes produce? | Aqueous humour |
| What is the path of the aqueous humour? | 1. Circulates through anterior and posterior chambers 2. Leaves eye through spaces in pectinate ligaments 3. Drains into sclera venous sinus |
| What is important about the production and drainage of the aqueous humour? | There is a balance to prevent an increase in intraoccular pressure and with prolonged pressure it will lead to degeneration of structures |
| What affects the is angle of filtration? | Iridocorneal angle affects the drainage |
| What is the innervation of the vascular tunic? | 1. Sympathetic fibres from the CCSG - Follow VI to orbit - Innervate dilator of pupil 2. Parasympathetic fibres - Pre-synaptic fibres run to orbit in oculomotor nerve - Post-synaptic fibres (short ciliary nerves) innervate ciliary muscle and constrictor of pupil |
| What are being tested by shining a light into the animal's eye? | CNs II (sensory) and III (motor) Parasympathetic components |
| What is special about the cat cornea and the angle of filtration? | Large cornea and so large angle of filtration |
| Give 4 symptoms of Horner's syndrome. | 1. 3rd eyelid visible across eye 2. Pupil constricted 3. Drooping of lid 4. Eye retracted in |
| What does the choroid do in the vascular tunic? | Supplies blood - Has light-reflecting layer in some species (nocturnal adaptation) |
| What is the light reflecting layer in the dorsal fundus of the choroid? | Tapetum lucidum |
| What is a fundus? | Internal surface of posterior surface of the animal eye |
| How can the optic dis be distinguished? | Circular portion |
| What is found in the dog fundus with colour diluted? | 1. Complete vascular ring (branches of the retinal artery) 2. Non-tapetal choroid (area that won't reflect light) 3. Optic disc 4. Tapetum lucidum |
| What is found with a subalbinotic (colour diluted eye)? | Red fundus: No tapetum lucidum Blue Iris: no pigment |
| What is the fundus of a pig like? | No tapetum Large veins |
| What is the fundus of a small ruminant like? | Tapetum lucidum (develops post natally) Twisted vessles (arterioles and venuoles) Optic disc Myelinated fibres around periphery of optic disc |
| What is the fundus of an adult ruminant like? | - Non-tapetal choroid - Optic disc - Tapetal choroid |
| What is the fundus of a horse like? | - Poor retinal vasculature - Choroidal veins show through - Fine retinal vessels forma a 'brush border' around the optic nerve |
| What 3 structures make up the vascular tunic? | 1. Iris 2. Ciliary body 3. Choroid |
| What is the innermost of the layers? | Nervous tunic - retina |
| What are the 2 layers of the retina? | 1. Oyter pigmented layer (pars ceca retina) - non visual part 2. Inner non-pigmented layer (pars optica retina) - visual part |
| Where is the pars ceca retina? | From optic nerve to pupillary margin |
| Where is the pars optica retina? | From optic nerve to ora serrata |
| What does the pigment of the retina and choroid allow? | The posterior eye to be dark and so it can absorb reflected light and prevent blurred vision |
| Give 6 cell types that are found in the pars optica retina. | 1. Ganglion cells 2. Amacrine cells 3. Horizontal cells 4. Muller cells 5. Bipolar cells 6. Rods and cones |
| What is the optic disc? | Point at which nerve fibres converge to form the optic nerve - no photoreceptors - Blind spot |
| Where is the Vitreous chamber? | Posterior to lens |
| What does the vitreous chamber contain? | Gel-like 'vitreous body' or vitreous humour |
| What are you likely to find in young farm animals in the vitreous chamber? | Hyaloid canal which runs from the back of lens to the optic disc. It contains the hyaloid artery in embryo |
| What is the lens made up of? | 1. Outer capsule under constant tension by zonular fibres 2. Hard nucleus composed of many fibres - fibres join at Y- shaped sutures |
| What can vary with the structure of the lens between species? | The joining of the fibres at the Y-shaped sutures |
| Where is the site of cataracts? | Y shaped sutures |
| How quickly can a diabetic cataract appear? | 24 hours to 3 weeks |
| What can be done to correct a cataract? | Use a prosthetic lens to replace the original |
| What do the eyes form from embryologically? | Section of the rostral end of neuralplate during formation of brain vesicles - form the optic sulci either side of the neural groove |
| How do the eyes develop? | 1. Optic vesicles develop laterally from diencephalon 2. Neuroectoderm contacts surface ectoderm and stimulates it to thicken into a "lens placode" 3. Distal part of optic vesicle invaginates to form optic cup 4. Lens placode invaginates to form the lens vesicle: nourished by hyaloid artery 5. Mesenchyme condenses around the optic cup and will form the vascular and fibrous tunics 6. Two layers of optic cup develop into pigmented and neural parts of retina |
| Why are the eye lids of nesting animals fused at birth? | The lacrimal apparatus isn't developed fully and will result in damage if they are open |
| Give 3 clinical relevance of the eye embryology. | 1. Collie eye anomaly (CEA) 2. Coloboma 3. Persistent pupillary membranes |
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