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Eye
 

Eye

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    Eye Eye Presentation Transcript

    • The Eye and its Appendages 1
    • The Eyeball 2
    • - the peripheral organ of vision, is situated in a skeletal cavity, the orbit- 1 inch in diameter, 8g. in weight- The eyeball is embedded in orbital fat, separated from it by a thin fascial sheath (capsule of Tenon) 3
    • Cavities of the Eyeball 4
    • 1. Anterior Cavity- further divided intoanterior chamber andposterior chamber due tothe position of the iris.- contains the acqueoushumor produced by the ciliary process. 5
    • 2. Posterior Cavity- located behind the lens- contains the vitreoushumor enclosed inhyaloid membrane 6
    • Layers of the Eyeball 7
    • The Layers of the Eyeball1. Fibrous coat - sclera and cornea2. Vascular coat - choroid, ciliary body and the iris3. Neural coat - retina 8
    • Sclera1. The Fibrous Coat Cornea 9
    • A. The Sclera- relatively hard consistency, is a dense layer which, whendistended by intraocular pressure, maintains the shape ofthe eyeball- external surface is white and smooth and is in contactwith the inner surface of the fascial sheath of the eyeball- provides passage for nerves of the cornea and vascularautonomic nerves and attachment for extrinsic eye muscles 10
    • B. The Cornea- is the anterior, projecting transparent part of theexternal tunic, and- its tear film cover is the major site of refraction oflight entering the eye. 11
    • ChoroidThe Vascular Coat Ciliary Body Iris 12
    • a. The Choroid- The choroid is a thin, highlyvascular, dark brown tissuewhich lines almost theposterior five-sixths of the eye;- it is pierced behind by theoptic nerve and is firmlyadherent to the sclera;- it is thicker posteriorly;- internally it is firmly attachedto the retinal pigmented layer. 13
    • b. The Ciliary Body- The ciliary body is directlycontinuous with the choroidbehind and with the iris in front- Internally it shows a scallopedperiphery where it is continuouswith the choroid and retina,termed the ora serrata.- The ciliary body is concernedwith the suspension of the lensand with accommodation- It is also a major source ofaqueous fluid for the anteriorsegment of the eye 14
    • c. The Iris- is an adjustablediaphragm around acentral aperture- the pupil, whichcontrols the amount oflight entering the eye- The concentration ofmelanocytes is the mainfactor determining thehue of the iris. 15
    • Muscles of the Iris1. Sphincter Pupillae - This is a flat annulus of smooth muscle about 0.75 mm wide and 0.15 mm thick. - Its densely packed fusiform myocytes are often arranged in small bundles, as in the ciliary muscle, and pass circumferentially around the pupil. 16
    • Muscles of the Iris2. Dilator Pupillae - A thin stratum lying immediately anterior to the epithelium of the posterior iridial surface, - its fibers are in fact the muscular processes of the anterior layer of this epithelium, - their apical processes form the epithelium itself. 17
    • RetinaThe Neural Coat 18
    • The Retina- is the neural, sensory stratum of the eyeball- It is thin, being thickest near the optic disc- contains a variety of cell types. They include thephotoreceptors (rod and cone cells),- Near the centre of the retina is an oval, yellowish area, themacula lutea which has a central depression, the foveacentralis, where visual resolution is highest. 19
    • Optic Disc- This region, where retinaltissues meet the neuralelements of the optic nerve- Besides being the exitpoint for the optic nervefibres, it also provides apoint of entry and exit forthe retinal circulation.- superomedial to theposterior pole of the eye 20
    • Rods and ConesCone cells - chiefly responsible for high spatial resolution and colour vision in good lighting conditions (photopic vision), - highly concentrated at the fovea centralis, but they populate the whole retina, intermingled with rods Three types according to their maximum spectral sensitivities: red, green and blue 21
    • Rods and ConesRods - provide high monochromatic sensitivity to a much wider range of illumination down to much lower intensities (scotopic vision) although with relatively low spatial discrimination because of their different neural connections. - Rods are excluded from the fovea. 22
    • The Refractive of the eye which The components Media transmit and refract light 23
    • Composed of:1. Cornea,2. Acqueous humor,3. Lens,4. Vitreous humor. 24
    • Aqueous Humour- The total quantity of aqueous humour is small, filling the anterior and posterior chambers.- The ciliary processes are responsible for its production- is an avenue for nutrients, and metabolic exchange for the avascular tissues of the cornea and lens. 25
    • Vitreous Body- fills the vitreous chamber, occupying about four-fifths of the eyeball.- It is colourless, consisting of approximately 99% water, and although apparently structureless, a sparse but organized cellular and fibrous content is present. 26
    • Lens- is a transparent, encapsulated, biconvex body, placed between the iris and the vitreous body.- encircled by the ciliary processes, to which it is attached by the zonular fibres collectively forming the zonule holding the lens in place and transmitting the forces stretching the lens except in visual accommodation. 27
    • CONDITIONS OF THE EYE 28
    • Emmetropia• Ideal state of the eye in which no refractive error is present 29
    • Myopia• Also known as nearsightedness, is a condition in which a person can see near objects more clearly than distant objects.• Light focusses in front of the retina 30
    • Hyperopia• Also known as farsightedness, is a condition in which a person can see distant objects more clearly than near objects.• light focusses behind the retina 31
    • Presbyopia• Normal part of aging.• It develops as the lens of the eye becomes less flexible and loses its ability to focus on near objects. 32
    • Lens become thicker when viewing near objects 33
    • The lens in the presbyopic eye cannot change shape to focus on near objects 34
    • Astigmatism• A condition in which objects, both near and far, appear blurred.• Often occurs in combination with myopia nad hyperopia. 35
    • Cataract• Is a cloudiness or opacificationin the normally clear and transparent lens of the eye. 36
    • THE ACCESSORY STRUCTURESOF THE EYE 37
    • • 1. The Eyelids• 2. The Lacrimal Apparatus• 3. The Eye Muscles 38
    • Functions: 1. provide protection, 2. lubrication, and 3. support 39
    • The Eyelids 40
    • - 2 movable folds, with the upper being more larger and movable, due to the presence of the levator palpebra superioris.- covered by skin, externally, and mucous membrane (palpebral conjunctiva) in the deep aspect.Functions : 1. provide protection when firmly closed 2. keep the surface of the eyeball lubricated with its continual blinking. 41
    • Layers of the Eyelid 42
    • Layers of the Eyelid1. Skin2. Loose subcutaneous tissue3. Muscular layer4. Submuscular layer5. Tarsal plates6. Conjunctiva 43
    • 1. Skin- eyelashes- sebaceous glands (glands of Zeis) Sty - infection of the glands of Zeis- sweat glands (glands of Moll) 44
    • 2. Loose subcutaneous tissue - extremely loose and easily distended by blood and fluid3. Muscular layer - orbicularis oculi muscle4. Submuscular layer - contains sensory nerves 45
    • 5. Tarsal plates - 2 thin plates of dense connective tissue - forms and supports the eyelid - presence of lateral and medial tarsal ligaments - receives the levator palpebra superioris6. Conjunctiva - mucous membrane that attaches the eyeball to the eyelid ( palpebral and bulbar) 46
    • STRUCTURES PRESENT IN THE EYELIDS 47
    • 1. Palpebral fissure 2. Palpebral commissures (canthi) a. lateral - more acute, placed directly against the globe b. medial - lacrimal lake, lacrimal caruncle, lacrimal papilla, lacrimal punctum 48
    • The Lacrimal Apparatus 49
    • Composed of the following structures: 1. lacrimal gland, which secretes a complex fluid (tears) and whose excretory ducts convey fluid to the surface of the eye, 2. the paired lacrimal canaliculi, 3. the lacrimal sac and 4. the nasolacrimal duct, by which the fluid is collected and conveyed into the nasal cavity. 50
    • 1. Lacrimal Gland- located superolaterally along the orbit- secretion empties in the pocket between the eyeball and the eyelid- secretes tears which are alkalinic, watery, and contain lysozyme 51
    • 2. Lacrimal Canaliculi- superior and inferior- conducts the tears to the lacrimal sac 52
    • 3. Lacrimal Sac- located in the lacrimal fossa- presents a fundus 53
    • 4. Nasolacrimal Duct- 3/4 of an inch in length- drains into the inferior nasal meatus 54
    • The Orbit 55
    • The Orbit- contains the eyeball in its anterior part and the posterior part is filled with fat, fascia, muscles, blood vessels and nerves- Capsule of Tenon separates the anterior and posterior- Periorbita lines the orbit and is continuous with the dura mater of the brain 56
    • The Eye Muscles 57
    • The Eye Muscles- Composed of the 7 muscles of the eye- Lateral rectus is supplied by the Abducent N.- Superior oblique is supplied by the Trochlear N.- The rest is supplied by the Oculomotor N. 58