Y1: Term 4: Eyes
Card Set Information
Y1: Term 4: Eyes
Sensory organ of vision
*Conjuctiva thin mucous membrane cover the sclera
*Iris function is to vary the opening of its centre
*Pupil is determined by parasympathetic and sympathic chain of autonomic nervous system and controls the amount of light entering the retina
*parasympathetic branch causes constriction of the pupil
*sympathetic branch causes dilation of the pupil
Three concentric coats
Outer fibrous sclera
- tough protective white covering
Middle vascular choroid
- dark pigmentation to prevent light from reflecting internally and heavily vascularized to deliver blood to retina
Inner nervous retina
- inner layer retina is the visual layer of the eye light waves are changed into nerve impulses.
* the outer layer of the eye which light passes
*well supply with nerve endings, made up of mostly pain fibers - tear occurs during touching & blinking.
*vulnerable to damage ( trauma/injury) but have the ability to repair itself.
*only transparented tissue in the body
*obtain nutrients from the sclera by diffusion from blood vessels.
*contribute to refraction or bending of light rays and focussing of vision
*avascular but heavily innervated by sensory neurons
*loss of central vision resulting in blurred vision.
*caused by progressive degeneration of the centre of the retina
*most common visual impairment and blindness in older adults.
* there is no cure.
* a group of
conditions causing visual loss due to optic nerve neuropathy
Accompanied by an increase in intraocular pressure
caused by obstruction of the outflow of aqueous humor.
*disorder can cause
blindness if untreated
*avascular, transparent biconvex structure
*held in place by zonules attach to surrounding ciliary bodies
contraction and relaxation
of muscle fibres
ciliary bodies allows for near and far vision
*An opacity of the lens that interferes with transmission of light into the eye onto the retina
*most common cause of age related visual loss
*surgicaly corrected by implanting an intraocular lens
Receives visual images, partially analyses them then sends this modified information to the brain
outer epithelial layer
inner neural layer-contain millions of photo receptor cells
*Begins with photoceptors cells (light dector) and cones (colour dectector) of the retina.
*Their responses are transmitted by bipolar cells to a layer of ganglion cells
*The axon of these gaglion cells generate an action potential which is then transmitted via optic nerve to the brain as vision
*Newborns- eye movement is poorly coordinated, by 3-4 months fixate on single image.
*reach adult size by 8 years old.
: pupil size decreases lens looses elasticity and becomes hard; harder for lens to change shape to accomodate for near vision (>40 years)
*Cataract formation (lens opacity), glaucoma and macular deneration.
Subjective data - Health Hx
*vision difficulty - which eye or bilateral (both)
*Strabismus, diplopia (cross eye)
*past hx of injury or surgery
*family hx of glaucoma
*glasses or contact lenses?
*Snellen eye chart is used to test visual acuity.
*Chart 6m from patient
*pt covers one eye at a time & read lowest line
*top no. represent distance from chart eg 6metre
*bottom no. respresents the number next to the smallest line successfully read by pt.
*6/6 score indicate perfect vision
*the larger the denominator the poorer the visiual acuity
What is a snellen chart?
chart used to test visual acuity
What's the distance for snellen chart?
Right eye is 6/18, left eye is 6/6 which eye is better?
What is presbyopia
farsightedness due to weakening of ciliary muscles and loss of elasticity in the lens.