1. 1 Lecture: 4 The Sense of Vision Dr. Eyad M. Hussein Ph.D of Neurology Consultant in Neurology Department, Nasser Hospital, Assistant Professor, Faculty of Medicine, Islamic University Faculty of Dentistry, University of Palestine

2. الرجاء تحويل الجوال إلى وضع الصامت مع الشكر 2

3. 3 I.Accessory structures (the adnexa of the eye): includes eyebrows, eyelids, eyelashes, lacrimal apparatus, conjunctiva, extrinsic eye muscles. Help protect the eyes from direct sunlight and damaging particles. II.Eyes: is the organ of vision. III.Optic nerve, tract, and pathway. Components of the Visual System

4. 4 I. Accessory structures of the Eyes 1.Eyebrows: protects eyes - to prevent sweat, water, and other damaging particles from falling down into the eye. 2.Eyelid (Superior and Inferior Palpebra): for blinking “average blinking = 25B/min”. Function: Protects the eye from foreign objects, sun, bright light and from sweat. Help spread tears over surface of eye (moist & comfort). They keep the eyes from drying during sleep.

5. 5 3. Eyelash: Protects the eye from foreign objects. Lubricates lids and restrains tears from flowing over the margin of the eyelids. 4. Medial and lateral commissure: angels where the eyelids join at the medial and lateral margins of the eye. 6. Conjunctiva: thin, clear layer of skin covering of the front of eye (covers the sclera and the inside of the eyelids). Function: Helps lubricate the eye by producing mucous. Immunological function: helps to prevent the entrance of microorganism into the eye.

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8. 8  Lacrimal Gland: located lateral to eye and secretes tears.  Superior and inferior lacrimal canals (Canaliculi): collect tears.  Lacrimal sac: collects tears from lacrimal canals.  Lacrimal punctum: opening of each lacrimal canal.  Nasolacrimal duct: collects tears from lacrimal sac and empties tears into nasal cavity. Lacrimal Apparatus

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11. 1.Lateral rectus muscle: abducts (laterally) the eyeball. 2.Medial rectus muscle: adducts (medially) the eyeball. 3.Superior rectus muscle: elevates, adducts and rotates medially. 4.Inferior rectus muscle: depresses, adducts and rotates medially. 5.Superior oblique muscle: depresses, abducts and rotates laterally. 6.Inferior oblique muscle: elevates, abducts and rotates laterally. 7.Orbicularis oculi: close the eyes. 8.Levator palperbrae superiosis muscle: open the eyes. 9.Muller’s muscle (Superior tarsal muscle): is a smooth muscle, that helps to raise the upper eyelid with the levator palpebrae superioris muscle. 11 Extrinsic Eye Muscles

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16. 16 II. The Eyeball The eyeball consists of three tunics (layers):  External (fibrous) tunic: consists of the cornea (anterior) and the sclera (posterior).  Middle tunic-Uvea (vascular and smooth muscle layer): consists of the ciliary body, iris (anterior) and the choroid coat (posterior).  Internal tunic (nervous layer): consists of the retina.

17. 17 Layers of the Eyeball

18. 18 1. Cornea: Clear transparent layer. Anterior portion. Located in front of the iris. Only organ that has no blood vessels. One of the first organs transplanted.  Function: Light transmission. Light refraction (focus light as it enters eyes). External (Fibrous) Tunic

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20. 20 2. Sclera: “White of the eye”. Posterior portion. Surrounds the eye and gives the eye its shape. The sclera is attached to the extraocular muscles.  Functions: Protection. Muscle attachment. Shape of the eye.

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22. 22 1. Iris: Ring shaped tissue. Anterior portion. Pigmented part of eye. Contains blood vessels, pupillary muscles. The iris divided the space between the lens and cornea into anterior and posterior chambers.  Function: controls the amount of light that enters the eye (light intensity function). Pupil: central opening of iris. Two smooth (intrinsic) muscles: 1.Circular muscles: Constrictor (sphincter) pupillae muscle. 2.Radial muscles: Dilator pupillae muscle. Middle (Vascular) Tunic

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24. 24 Intrinsic Eye Muscles Anisocoria Double of iris and pupils

25. 25 2. The ciliary body : “Ciliary muscle and process”. Anterior portion. Pigmented ring of smooth muscle around the lens.  Function: regulates the shape of the lens for accommodation. 3. Choroid Coat: Posterior portion. Vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera.  Function: Provides blood supply to the outer layers of the retina.

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28. 28  Lens: Clear, flexible structure. Behind the iris & pupil. Surrounded by a ring of muscular tissue – ciliary body.  Function: Light transmission. Light refraction. the lens & ciliary body help control fine focusing of light and images on retina.

29. 29 1. Anterior Chamber: Fluid-filled “Aqueous humor” space. Behind the cornea & infront of the iris. Aqueous humor helps nourish the cornea & the lens. 2. Posterior Chamber (PC): Fluid-filled “Aqueous humor” space. Behind the iris & infront of the lens. 3. Vitreous Chamber: located behind the lens & infront of the retina. Filled with a gel-like fluid called the vitreous humor. The vitreous help maintain the shape of the eye. Chambers of the Eye

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32. 32 Retina: ◦ Consists of a specialized layer of cells (nervous tissue). ◦ Contains light sensitive photoreceptors (cones and rods of the retina). ◦ Converts light signals into nerve signal then send these signals to the optic nerve “Acts like the film in a camera to create an image”. ◦ Continuous with optic nerve. Inner (Nervous) Tunic

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35. 35 Histology of the Retina of the Eye

36. هذا سلايد غريب يحتاج إلى إنسان رايق جدا وفصل كامل لفهمه 36

37. 37 The Nerve Supply of the Eye The Optic Nerve II: enters the orbit through the optic foramen and passes to the light receptor cells in the retina. The Oculomoter Nerve III: control the movement of the eyeball. it enters the orbit through the superior orbital fissure. The Abducent Nerve VI: enters through the superior orbital foramen. The Trochlear Nerve IV: enters through the superior orbital foramen. The Trigeminal Nerve V: send branches to the eye. Opthalmic and maxillary divisions (zygomatic nerve). The Facial Nerve VII: temporal and zygomatic branches innervates the orbicularis oculi.

38.  Optic Nerve: (Latin for "to see"). A bundle of 1 million nerve fibers. Responsible for transmitting nerve signals from the retina to the brain. The optic disc is the front surface of the optic nerve.  Function: Special sensory nerve (Sense of vision). III. Visual Pathway The Optic Nerve 38

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41. Receptors of light are rods and cones of retina → optic nerve → optic canal of the sphenoid bone → optic chiasma (the nasal or medial fibers decussate to the opposite optic tract, while the temporal or lateral fibers continue in the same optic tract → optic tract (gives fibers to Edinger-Westphale nucleus in midbrain) → relay in the lateral geniculate body → thalamus → posterior limb of internal capsule → optic radiation → end in areas 17, 18, 19 of occipital lobes. Pathway of the Vision 41

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44. 44 The Visual Pathway

45. 45 The Visual Pathway

46. Acuity of vision: with a Snellen chart. The normal acuity is 6/6 to 6/9 in each eye. Visual Acuity 46

47. Checked by confrontation, if abnormal recorded with Goldman screen Visual Field Defects Confrontation Test Perimeter 47

48. Fundus Examination (Ophthalmoscopy) PapilledemaNormal optic nerve disc 48

49. Color Blindness Test 49

50. 50 Visual Pathway and Visual Field Defect Lesions: A. Blindness in one eye (Left). B. Bitemporal hemianopsia. C. Contralateral homonymous hemianopsia (Right) D. Quadrantanopsia E. Contralateral homonymous hemianopsia (Right). RightLeft

51. Direct Light Reflex: Light in one eye leads to constriction (miosis) of the same eye Indirect Light Reflex : Light in one eye leads to constriction (miosis) of the opposite eye Pathway of Light Reflex Fibers from rods and cones of retina → optic nerve → optic chiasma → optic tract → before reaching the lateral geiculate body → they pass to the third cranial (oculomotor) nerve nucleus (Edinger-Westphal nucleus) in midbrain of both side → through oculomotor nerve → ciliary ganglion → supply the constrictor pupillae muscle Light Reflex 51

52. Patient is asked to follow your finger from a far point to a near one:  Ciliary muscles contraction leads to change the shape of lens (becomes thicker and rounder due to its elasticity).  Miosis (contraction of constrictor pupillae muscle).  Convergence (contraction of both medial recti muscle). Accommodation and Convergence Reflex for Near Vision 52

53. Accommodation of the Lens for Far Vision Ciliary muscles relaxes and lens becomes thinner (flatter) due to its elasticity. Mydriasis (contraction of dilator pupillae muscle).

54. 54 a.Accommodation of the lens to far vision. b.Accommodation of the lens to near vision.

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