EYEThe eye is an extension of the brainVisit www.worldofteaching.comFor 100’s of free powerpointsEye brain proxomityCan you see : the optic nerve bundle?Spinal cord?Cross sectionYou must know the position of:RetinaLensCorneaScleroticOptic nerveCilary musclesSuspensory ligamentsRetina –receives the imageFull of light receptors which are sensitive to:ColourLight levelsMassive blood supply is also neededFovea is the main focal point and has greatest density of light receptorsRetina receptorsLight receptors are called rods and coneFocusing on objectsThe lens and cornea focus the light on the retinaFocusingThe lens job is to make the rays hit the same point The red rays will be out of focusBending lightLight is refracted and bent to focus it as it passes through the lensLens thickness can be changed so the amount of bending is changedNear visionto bend the light more to focus itFat lens neededDistance visionRays enter the eye closer togetherNeed less bendingThinner lens neededChanging lens thicknessThe lens is slightly elastic, its relaxed state is short and fat.Cilary muscles are attached to the lens, when contracted they pull the lens thinControlling light levelsYour eye are very sensitive and can be damaged by harsh light. Your iris controls light allowed into the eye by changing the size of the pupil