Term
| What needs to happen to see in general? |
|
Definition
-clear ocular media
-light stimulatio of the retina => induces a chemical change in the photoreceptors => induces an electrical impulse => nerve impulse is transmitted ot the brain
-the brain processes the image to make it useful |
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Term
| What factors decide what vision serves a specific species best? |
|
Definition
-Survival: finding food and escaping prey
-reproduction |
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Term
| What are the different aspects fo vision that will vary with the species? |
|
Definition
-acuity
-color vision
-low light vision
-motion detection
-depth perception |
|
|
Term
|
Definition
| -the ability to see detail |
|
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Term
| Describe the composition of the retina required for ncreased visual acuity. |
|
Definition
-inc photoreceptors
-inc ganglion cells
-inc ratio of ganglion cells to photoreceptors |
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Term
| Is a fovea adaptation or visual streak better for visual acuity? |
|
Definition
|
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Term
| How do fovea adaptations increase visual acuity? Which species have this adaptation? |
|
Definition
-high density of cones and 1:1 relationship with ganglion cells
-Humans, birds, some reptiles (lizards) |
|
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Term
| How does a visual streak increase visual acuity? Which species have this adaptation? |
|
Definition
-area of highest density of photoreceptors and ganglion cells
-dogs, cats, horses, and most domestic species |
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Term
|
Definition
| -ability of the lens to focus |
|
|
Term
| What does trichromatic mean? |
|
Definition
| -3 visual pigments: red, blue, green cones |
|
|
Term
| What does dichromatic mean? |
|
Definition
| -2 visual pigments: blue, red cones |
|
|
Term
| Which species are trichromatic? |
|
Definition
|
|
Term
| Which species are dichromatic? |
|
Definition
|
|
Term
| What is the advantage of dicrhomatic vision? |
|
Definition
| -better at distinguishing b/n shades of gray which improves vision in dim light |
|
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Term
| What are some visual daptations to improve night vision? |
|
Definition
-higher number of rods in the retina
-tapetum
-slit pupil
-large cornea
-larger, shperical shaped lens |
|
|
Term
| Why is a slit pupil an adaptation for low light vision? |
|
Definition
| -ability to dilate wider at night |
|
|
Term
| How is a large cornea an adaptation for low light vision? |
|
Definition
| -allows mor light into the ey |
|
|
Term
| What are some adaptations for motion detection? |
|
Definition
-fovea
-higher number of rods in the retina
-large peripheral visual field
-owl > human > horse > cat |
|
|
Term
| Is binocular or monocular vision better at depth perception? |
|
Definition
|
|
Term
| What are the ways that monocular vision animals make up for the loss of depth perception? |
|
Definition
-relative brightness of objects
-areas of light and shadow
-changes in head movement causes an apparent change in object position |
|
|
Term
| What is unique about the avian retina? |
|
Definition
| -avascular and has a pecten |
|
|
Term
| What is the function of the avial pecten? |
|
Definition
| -nutritional for the retina |
|
|
Term
| Do birds have a visible optic disc? Why or why not? |
|
Definition
-no
-it is covered by the pecten |
|
|
Term
| What is unique about snake eylids? |
|
Definition
| -fsed into a clear structure called the spectacle |
|
|
Term
| What is a retained spectacle in a snake? What causes it? How do we treat it? |
|
Definition
-spectacle does not come off when the snake sheds
-due to low humidity
-retained spectacles should be gently soaked off or shed naturally by inc environmental humididity (DO NOT PULL OFF) |
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Term
|
Definition
|
|
Term
| What causes blepharoedema in chelonians? |
|
Definition
|
|
Term
| How does vitamin A deficiency lead to blepharoedema in chelonians? |
|
Definition
| -multifocal squamous metaplasia of epi => normal columnar, cuboidal epi is replaced by flattened cells => cullular debris accumualtes underneath the eyelids |
|
|
Term
| What is special about the nasolacrimal system in rabbits? |
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Definition
|
|
Term
| HOw does the nasolacrimal system in a rabbit have a very close association wiht dental disease? |
|
Definition
-elongated tooth roots can impinge on the nasolacrimal duct resutling in dacryocystitis
-ALWAYS PERFORM DENTAL RADS |
|
|
Term
| Why must we stay close to the globe when enucleating an eye from a rabbit? |
|
Definition
| -lare orbital venous sinus |
|
|
Term
| What happens to the rabbit eye due to Encephalitazoan cuniculi? |
|
Definition
-cataract development with lens capusle rupture => uveitis
-iris abscess |
|
|
Term
| What is pea eye in a guinea pig? |
|
Definition
| -protrusion of part of the orbital alcrimal or salivary gland appears as a pink nodule at the medial canthus |
|
|
Term
| What is fatty eye in a guinea pig? What causes it? |
|
Definition
-prominent protrusion of the lower, lateral conjunctiva due to lipid accumulation
-either inherited or due to overfeeding |
|
|
Term
| How do we treat pea eye in guinea pigs? How do we treat fatty eye in guinea pigs? |
|
Definition
|
|
Term
| What does a guinea pig have in comon iwth a horse? |
|
Definition
| -paurangiotic fundus: the only blood essels are tiny ones off the optic disc |
|
|
Term
| What cause prphyrin ocular discharge in rats, mice, and hamsters? |
|
Definition
-from inflammation of the HArderian gland: one of the lacrimal glands in the orbit
-porphyrin pigment resultsin red tear staining |
|
|
Term
| What causes pryphyrin ocular discharge in rats, mice, and hamsters? |
|
Definition
-inc due to stress or illness
-or accumulation from lack of grooming |
|
|
Term
| What is special on a fundic exam of a rat, mouse, or hamster? |
|
Definition
| -large lens makes the retinal vessels appear veyr prominent and raised |
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