- 3 layers of the eye
- Fibrous- outer layer
Uvea- middle layer
Sensory layer- inner layer - accomodation
- the ability of the eye to focus diferentially for objects of near vision (less than 5 m, or 20 ft)
- acqueous humor
- a thin, watery substance contained in the anterior segment- helps to maintain the intraocular pressure of the eye and provides nutrients for the avascular lens and cornea
- anterior segment
- anterior the lens contains acqueous humor- divided into anterior and posterior chambers
- astigmatism
- caused by irregularities in the curvatures of the lens and/or cornea lead to blurred vision- need cylindrically ground lenses- compensate for inequalities in the curvatures of refracting surfaces
- binary vision
- 2 eyed- both eyes look in approximately same direction- see slightly diff views- their visual fields overlap to a considerable extent- provides 3-D vision and accurate means of locating objects in space
- cataracts
- where the lens becomes increasingly hard and opaque
- choroid
- posteriormost part of the uvea- blood rich nutritive region contains dark pigment that prevents light scattering w/in the eye
- ciliary body
- anterior part of the uvea- chiefly composed of ciliary muscles which are imp. in controlling the lens shape, and ciliary processes (which secrete aqueous humor)
- ciliary glands
- modified sweat glands that lie between the eyelash hair follicles and help lube the eyeball
- ciliary processes
- continually forms acqueous humor
- cones
- color receptors that permit hight levels of acuity but fnction only under conditions of high light intensity; most found in fovea centralis-
- conjunctiva
- a mucous membran that lines the internal surface of the eyelids (palpebral conjunctiva) and continues over the anterior surface of the eyeball to its junction with the corneal epithelium (bulbar conjunctiva) secretes mucus to lubricate the eyeball
- conjunctivitis
- inflammation of the conjunctiva
- convergence
- medial eye movements- essential for near vision- produced by the extrinsic muscles
- Cornea
- part of the fibrous layer- anterior most portion- where light enters the eye
- emmetropic eye
- normal eye- able to accomodate properly
- extrinsic eye muscles
- 6 of them attach to the exerior surace of each eyeball to control eye movements and make it possible for the eye to follow a moving object.
- fibrous layer
- outer layer of eye- protective layer- dense avascular CT- 2 regions SCLERA and CORNEA
- fovea centralis
- center of the macula lutea- a minute pit which contains mostly cones and is the area of greatest visual acuity- focusing for discriminitive vision
- hyperopia
- where the image focuses behind the retina- farsightedness- can\'t see close up- need convex lenses to augment the convergin power of the lens for close vision
- inferior oblique
- ex. eye muscle elevates eye and turns it laterally
- inferior rectus
- ex. eye muscle- deperesses eye and turns it medially
- Inner nervous layer of the retina composed of 3 major neuronal compositions____
- photoreceptors, bipolar cells, gnglion cells
- Iris
- most anterior part of the uvea- contains the pigment- in close vision and bright light the pupil is little and vise versa
- lacrimal apparatus consists of the
- lacrimal glad, lacrimal canaliculi, lacrimal sac, and the nasolacrimal duct
- lacrimal caruncle
- fleashy elevation at the medial commisure that produces a whitish oily secretion
- lacrimal glands
- superior to the lateral aspect of each eye. continually dilute tears that flow onto the anterior surface of the eyeball through several small ducts
- lacrimal puncta
- tiny openings of the lacrimal canaliculi through which earsflush across the eyeball
- lateral geniculate body
- where the optic tract fibers synapse with neurons- part of the thalamus
- Lateral Rectus
- Extrinsic eye muscle that moves the eye lateraly
- lens
- a flexible crystalline structure- focuses light on the retina- divides eye into 2 segments: anterior segment and posterior segment
- lysozyme
- antibaterial secretion contained in the lacrimal secretion`
- macula lutea
- yellow spot- area of high cone density- lateral to each blind spot and posterior to the lens
- medial and lateral commissures
- the junctions of the upper and lower eyelids
- medial rectus
- extrinsic eye muscle that moves the eye medially
- myopia
- nearsightedness- can see close objects w.out difficulty ut distant objects are blurred or seen indistinctly- correction requires a concave lens
- nasolacrimal duct
- empties into the nasal cvity
- near point of accommodation
- tests the elasticity of lenses
- Neural layer
- transparent inner layer of the retina which extends anteriorly onluy to the ciliary body- contains rods and cones
- optic chasma
- where the fibers from the medial side of each eye cross over to the opposite side
- optic chiasma
- where the fibers from the medial side of each eye cross over to the opposite side.
- optic disc
- \"blind spot\" the place where there are no photoreceptor cells- where the optic nerve leaves the eyeball
- optic nerve
- tight bundle of finbers leaving the retina
- optic radiation
- formed by the axons of the geniculate body
- optic tracts
- the fiber tracts formed by the optic chiasma- each optic tract contains fibers romt he lateral side of the eye on the same side and from the medial side of the opposite eye
- panoramic
- eyes are more on the side of the head- see in 2 diff directions
- pigmented epithelium
- outer layer of the retina- extends anteriorly to tcover the ciliary body and posterior side of the iris
- posterior segment
- behind the lens- filled w/ vitreous humor
- presopia
- old vision- elasticity of lens decreases w/ age- difficulty near or close vision
- problems resulting from from an eye not being able to accomodate properly:
- 1) from lenses that are too strong or too lazy (overconvergin and underconverging, respectively
2) from structural problem such as an eyebll that is too long or too short to provide for proper focusing by the lens
3) from a cornea or lens with improper curvatures - pupil
- hole in the iris that lets light pass
- real image
- the image formed on the retina as a result of the refractory activity of the lens (reversed from left to reight, inverted, and smaller than the object
- refracted
- when light rays are bent. Light rays in the visual field are refracted as they encounter the cornea, lens, and viteous humor of the eye
- rods
- specialized receptors for dim light- most numberous in the periphery
- Rods and cones
- photoreceptors contained in the neural layer of the retina
- Sclera
- region of the fibrous layer- opaque white forms bulk of fibrous layer
- sensory layer (retina)
- innermost layer of the eye- 2 layers: outer pigmented epithelium and inner neural layer
- sty
- an inflammation of one of the ciliary glands or a small oil gland
- supensory ligament (ciliary zonule)
- attached to the ciliary body- holds lens in place
- superior oblique
- ex eye muscle that depresses the eye and turns it laterally
- superior rectus
- ex. eye muscle... elevates eys and turns it eye medially
- tarsal glands
- located posterior to the eyelashes, secretes and oily substance
- uvea
- the middle layer of the eye- vascular layer- 4 parts: choroid, ciliary body, iris, pupil
- visual acuity
- sharpness of vision- tested w/ Snellen eye chart
- visual cortex
- in the occipital lobe of the brain- where the axons of the lateral geniculate body/ optic radiation synapse with thte cortical cells, and visual interpretation occurs
- vitreous humor
- gel like substance that fills the posterior segment- provides the major internal reinforcement of the posterior part of the eyeball, and helps to keep the retin pressed firmly against the wall- formed only before birth
