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Lana Trick (148)

Notes from both jan 31 and feb 2 lectures

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PSYC 2390
Lana Trick

stSensation and PerceptionJanuary 31 Review on the nature of light when we see light some is actually from a light source but most is bounced off of objects The color that we see depends on the type of light that bounces off of the object into our eyesIf you see something that is white it reflects all of the wavelengths of light equallyso that the object is bouncing a lot of light into your eyes Something black absorbs all wavelengths equally and only bounces back a very small amount of light back to your eyesRETINA contdDisorders of the retina include detached retina which is commonly because theyve gotten hit hard in the head hockey playersboxers and the retina rips away from the back of the eyeThe back of the eye is where the retina gets nourishment and regeneration of the photopigments by the pigment epitheliumWhen the retina becomes detached the image cant focus properly and the signals cannot get to the brain It can result in blindness There are ways of sort of gluing it back together using a cold probe or a hot probe but vision is never quite the sameAnother disorder is diabetic retinopathy high blood pressure and problems in general with circulation in people with diabetes and this can have many different effects such as poor circulation in the eye The eye especially the retina uses a lot of blood Diabetes causes the capilliaries in the eye to leak blood into the fluid in the back of the eye vitrious humor jellylike and bits of blood and tissue in the back of the eye This can cause floaters which are little pieces of tissue that are seen as black dots With retinopathy there is also neovascularization Because the circulation is inadequate in the retina so it tries to grow some new blood vessels but they are abnormal and just make the problem worse The new blood vessels also leak and can lead to scarring and result in retinal detachment They deal with this problem by laser photocoagulation which is for if its not a serious problem the laser seals off the abnormal blood vessels However if the situation is more serious they may do pan retinal photocoagulation which is radical and what they do is burn out retinal cells up to 2000 spread out over a large area to try to reduce the retinas blood needs in the hope of saving whats left Macular degeneration is a disorder that affects the fovea 100 cones fine detail In the centre of the fovea is an area called the macula 5mm and what happens with macular degeneration is that the cones in the area deteriorateThis results in trouble seeing detail Age related macular degenerationTheres this stuff called drusen yellowywhite gunk little lumps of it form between the Choroid and the Pigment EpitheliumWith age related macular degeneration people get many more drusen than other peopleDevelopment of drusen may be related to cholesterol and sometimes cholesterol and antioxidant vitamins are used in therapySlow developing macular degeneration is sneaky and happens so slowly that people dont realize that they are going blind Fast developing has drusen as well as neovascularization so two problemsA test called the Amsler Grid is used to see early signs of macular degenerationRetinitis Pigmentosa starts to occur in adolescence It starts as abnormalities in the pigment epitheliumIt begins to deteriorate and the cells begin to dieIt starts on the outside and works in towards the fovea night vision goes first and they slowly lose their vision and they then have tunnel visionThere is no treatment for retinitis pigmentosa but it can sometimes be slowed down with vitamin AGlaucomahas its effect on the retinal ganglionA substance called aqueous humor circulates around in a chamber between the cornea and the lensThis aqueous humor is always being replaced and in glaucoma the fluid pressure in the eye gets to be too high with too much aqueous humor and the pressure begins to push on the back of the eyeoptic nerve where all the ganglion cells leave the eye
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