STRUCTURE OF EYE Orbital cavity Iris Eye lids Choroid Eye ball Cilliary body Conjunctiva Aqueous humor Lacrimal gland limbus Cornea vitreous humor Sclera Ratina Pupil Lens
ORBITAL CAVITY“The bony cavity in skull containing the eye ball and its associated muscles, vessels and nerves also called eye sockets, orbit ” FUNCTIONS It serves as a cushion to protect eye ball from external force.
EYELIDS "The layer of skin covers and protect the eye it has thinnest skin of whole body" Functions protect and lubricate the eye blink and keep eye moist cut of light during sleep protect eye from dust particles and perspiration wipe eye and prevent dehydration fighting bacterial infection
palpebrae protects eyeEyelashes trigger blinkingLevator palpebrae superioris raises eyelid Eyebrows Shade the eyes Prevent perspiration into eye
CONJUNCTIVA " it is thin mucous membrane which covers the exposed part of eye " After covering the anterior surface the conjunctiva is reflected to the inner part of eyelids functions keep the eye moist by sliding the opposite portion of conjunctiva balbur portion palpebral portion balbur fissura palpebral fissura
EYE BALLThe globe-shaped portion of the eye surrounded by thesocket and covered externally by the eyelids.Diameter 1 inch (2.5 cm) in diameterWeight 7.5 gm
WALLS OF EYEBALL IS COMPOSED OF THREE LAYERS1) Outer layer which include cornea and sclera2) Middle layer which include choroid cilliary body and iris3) Inner layer ,the retina
CORNEA "cornea is the transparent convvex anterior portion of outer layer ofthe eye ball which cover the iris and pupil" or cornea is front window of eye that transmit and fucuses the light intoeye size 0.5 mm thick at center and 1to 2 mm thick at periphery
diameter 12mm horizontally and 11 mm vertically cornea has a refractory index of 1.376refractory index function it focuses light into eye
SCLERA Sclera is the tough white fibrous outer layer of the eye ball that cover posterior 5/6 of the eye anteriorly it is continuous with cornea Lamina cribrosa The posterior part of the sclera where it is pierced by the optic layer is thin with perforation it is name as lamina cribrosa
MIDDLE LAYER Choroid Cilliary body IrisChoroid is the thin vascular layer of eye ball situated between sclera and retina itform posterior 5/6 of middle layer►choroid is composed of the a rich capillary plexus, numerous small arteries andveins
CILLARY BODY Cillary body is thickened anterior part of middle layer of eye situated betweenchoroid and iris It is in the form of ring Cillary body has three partsi. Orbiculus ciliariesii. Ciliary body properiii. Ciliary processes
IRIS Iris is the colored curtain like structure of eye ball it formthe anterior most part of the middle layer it is like a thincircular diaphragm place in the front of lens It is a muscular has two muscles constrictor pupillae Dilator pupillae
PUPILit is a hole located in the Centre of iris and pupil is alsocentral transparent area of the eye.functionthe pupil modifies the amount of light entering into it.
INNER LAYER THE RATINAratina is a thin delicate membrane which photoreceptor anda layer of nerve fiber which are continous with the optic nerve.location...;it is placed between the vitrous internally andchoroid externally
FUNCTIONS1)retina act as a receptor mechanism of the eye and ultimate toolof vision light and color sensitive element of the ratinacommunicate their message via neural pathway to the visual cortexof the brain.2)ratina also play a role in light reflex and accommodation reflex.3)ratina impulses also help to maintain the tone, posture andequilibrium of the body.
PHOTORECEPTORthere are two photoreceptors in ratina1)rod ....responsible for dark vision2)cone......... responsible for colour vision
LENS it is a transparent, biconcave, elastic body that lies between iris and vitrous body. structure of lense it is formed of three components 1)the capsule. 2)the anterior epithelium. 3)the lens substance. composition... in young; 69% water and 30% protein..... in old age; decreases water %age, increase protein %age lense also contain potassium, sodium, chlorin, ascorbic acid and glutathione.
FUNCTIONS 1)lens refracts light and focus it on the ratina the focal length of human lens is 44mm and its refractory power is 23D
INTRAOCULAR FLUIDThe fluid in the eyeball responsible formaintenance of shape of the eyeball…….The two type of fluids are present in theeyeball……1)aqueous humor2)vitreous humor
AQUEOUS HUMOR it is a thin clear, colorless, transparent fluid present in theanterior(chamber between cornea and iris) and posteriorchamber(chamber between the iris and lens) of the eyeball. normal intraocular pressure is 16-22mmHg composition of aqueous humor... 98.7% water (organicsubstances.....albumin,globulin,glucose,pyruvate,lactate,urea) , solids1.3%(inorganic substances......sodium, calcium, potassium, magnesium,chlorides, phosphates, bicarbonates)
FUNCTIONS1) maintain the intraocular pressure.2)supply nutrition to avascular structure like cornea and lens.3)act as refractory medium.4)act as a barrier.5)remove the metabolic end products from lens and cornea.
VITREOUS HUMORvitreous humor is a viscous fluid present behind the lens inthe space between the lens and ratina. it is a highly viscousand gelatinous substance. it is also known vitreous body the major substances in it are albumin and hyaluronic acidthese substances enter vitreous body from blood by mean ofdiffusion
FU NC TION1)it helps maintain the shape of the eyeball.
GLAUCOMA it is a group of diseases characterized by increased intraocular pressure whichcauses damage of optic nerve resulting in blindness types Congenital glaucomaInfantile glaucoma juvenile glaucoma causes of glaucoma 1)blockage in drainage system. 2)increase intraocular pressure.
glaucoma also develops secondary to other disorders which effect the eyes common causes are. 1)diabetes 2)inflammation 3)injury to eye 4)excess use of drugs e.g. corticosteroidTreatmenttreatment does not cure the diseases but can prevent further damage of opticnerve it is aimed as lowering the intraocular pressure it is achieved by usingeye drops or medicine alone or in combination with laser treatment. Ifintraocular pressure dose not controlled by these methods surgery is required
CATARACT cataract is the opacity or cloudiness in the natural lens of the eye it is major cause of blindness worldwide. When the lens become cloudy. Light rayscannot pass through it easily and vision is blurred it develops in old age after 55-60years causes 1)eye injuries. 2)previous eye surgery 3)diabetes 4)hypocalcemia 5)long term use of drugs 6)long term unprotected exposure to sunlight 7)alcoholism 8)family history 9)diet containing large quantity of salt
SYMPTOMS 1)glare 2)painless blurred vision 3)poor night vision 4)diplopia in affected eye 5)need for a bright light whilereading 6)fading of colortreatment surgery is only treatment for this
REFRENCEEssential of Medical Physiology byJaypee (5th edition) chapter no.165… pageno. 924, 25,26,28,,29,30,33,34.2)Notes of sir Tabish3)Medical dictionary(Internet)