OPHTHALMOLOGY TOPIC ANATOMY OF THE HUMAN EYE.pptx

Anatomy of eye basics for mbbs

1. ANATOMY OF THE EYE Dr. Hardik Kalaria

2. Eye develops from neural ectoderm, surface ectoderm & mesoderm SURFACE ECTODERM Conjuctiva Corneal epithelium Eyelashes Epi of mebomian gland, gland of moll & ziss , lacrimal gland Crystalline lens

3. MESODERM Corneal stroma Corneal endothelium Desment’s membrane Sclera Choroid Iris stroma Extra occular muscle Cilliary muscle Bony orbit vitreous

4. NEURAL ECTODERM Sensory retina Retinal pigmentary epithelium Cilliary body epithelium Pigmentary epithelium of iris Sphinter pupillae Dilator pupillae Neural part of optic disc melanocytes

5. Eye consists of segments of two modified spheres one in front of others Cornea is more convex AP diameter is 24mm Vertical-23mm Horizontal -23.5mm

6. The globe has Three cocentric layers or tunica OUTER SUPPORTING LAYER Transparent cornea, Opaque sclera, Sclera, limbus MIDDLE VASCULAR LAYER Uvea - consist of choroid, cillary body & iris INNER NEURAL LAYER Retina composed of sensory portion & layer of pigment epithelium

7. b) crystalline lens transparent structure located immediately behind iris supported by zonules c) three chambers Ant chamber- located between iris & post surface of cornea communicate with post chamber through pupil Post chamber- triangular in shape bounded ant by post surface of iris & behind by lens & zonules Viterous cavity- longest & located behind the lens & zonules & adjacent to the retina throughout d) 2 segment Ant- conj, cornea, iris, lens Post- viterous & retina

8. CORNEA Elliptical structure Constitute 1/6 th of the eye ball Horizontal dia - 12mm, vertical dia-11mm Thickness 0.5mm in center & 1mm at perephery R.I 1.34 It is the main refracting surface of the eye Diopteric power +43D to +45D

9. Structurally consist of 6 layers EPITHELIUM Stratified squamous type 5-6 cells deep continuous with conj epi The basal cells are tall & oval nuclei intermediate layer (2-3 cells deep) are polyhedral wingcells Surface layer (2) very flat, non keratinized It rest on basement membrane secreted by basal cells

10. BOWMAN’S LAYER (ANT ELASTIC LAMINA) Ant condensation of substentia propria Once eroded does not regenerate so leaves behind sup corneal scar

11. SUBSTANTIA PROPRIA (STROMA) Constitutes 90% of corneal thickness Made up of collagen fibrills arranged in lamellae which lie parallel to the surface They form crystallline lattice in ground substance of gylcoprotein & mucoploysaccharide In between lamellae there are scattered corneal corpuscles & wandering cells

12. DUA’S LAYER Discovered by Harminder S Dua 15 micrometer thick Between corneal stroma & desment’s membrane Very strong & impervious to air

13. DESCEMENT’SMEMBRANE (POST ELASTIC LAMINA) Very strong homogenous & very resistant membrane Secreted by basement membrane of endothelial cells Readily regenerates after injury Old age it may bear some watery elevations called hassall henle’s bodies at perephery

14. ENDOTHELIUM Single layer of flattened polygonal endothelial cells Continuous with endothelium of antsurface of iris Does not regenerate

15. NERVE SUPPLY Corneal nerves derived from long & short cillary nerves branches of ophthalmic division of trigeminal nerve They form perepheral plexus just outside limbus & then pass into cornea by 60-70trunks They loose myelin sheath after 1-2mm inside cornea doesnot have proprioceptive sensation BLOOD SUPPLY Avascular structure Limbus supplied by ant conjuctival branches of ant cillary arteries & form perilimbal plexus of blood vessels

16. CONJUNCTIVA Mucous memb covering inner surface of eyelid & reflected to cover ant part of eye ball over sclera upto corneal margin PARTS Palpebral - consists of marginal, tarsal & orbital part & firmly adherent to deeper tissue Bulbar- lies over sclera & freely mobile Fornix- cul -de- sae at junction of palpebral & bulbar conjuctiva Limbal - it is the conjuctiva at corneal junction which is adharent

17. Structurally 3 layers Epithelial- it is 2layered thick at perepheral conj as it goes from fornices to limbus it becomes 4-6 layered & stratified sq at limbus mucous secreting goblet cells present througout Subepithelial layer- adenoid layer contain lymphocytes Fibrous layer- it is blend with deeper tissues NERVE SUPPLY- ophthalmic division of trigeminal nerves BLOOD SUPPLY- ant conj- ant cillary artery & post conj- lacrimal artery

18. SCLERA Dense tough fibrous envelop thet covers post 5/6 th of eyeball Two large opening ant corneal window & post for optic nerve It is pierced by various structures- 4 vortox veins (4mm behind equator), long & short cillary vessels & nrves Thickness surrounding optic nerve (1mm) & thickness just post to insertion of recti muscle (0.3mm)

19. Structurally 3 layers Episclera - loss fibrous tissue containing numerous capillaries Sclera proprer - dense network of collagen fibres , blo of variable diameter & irregular arrangement of collagen fibres it is opaque white in colour Lamina fusca - inner layer adjacent to choroid

20. BLOOD SUPPLY Episceleral & choroidal vessels Ant to insertion of recti , ant cilary art form dense episceleral plexus which get congested in ciliary conjection NERVE SUPPLY Anteriorly - long ciliary nerve Posteriorly - short cillary nerve

21. LIMBUS Transitional zone between cornea & sclera 1-2mm wide It contains trabecular meshwork internally through which aq humour leaves ant chamber

22. ANGLE OF ANTERIOR CHAMBER Bounded in front by cornea behind by ant surface of iris & parts of ant surface of lens which is exposed at pupil Peripheral recess is known as angle of ant chamber which is also called as cockpit of glaucoma Bounded ant- corneosclera & post- root of iris & ciliary body At this part in inner layers of sclera there is circular venous sinus called canal of schlem lined by endothelial cells & it play imp role in aqueous drainage

23. At periphery of angle between schlemm’s canal & recess of angle chamber lies loose meshwork of tissue called trabecular meshwork It is made up of circumferentially disposed flattened bands each of which is perforated by numerous oval opening through this passages communication exists between schlemm’s canal & ant chamber Angle visualized by gonioscope normally wide open 20.45 (<10 angle closure)

24. UVEA Middle coat ( uvea -grape) 3 parts Ant- iris a free circular diaphragm with central opening call pupil Intermediate- ciliary body Posterior- choroid

25. FUNCTIONS OF UVEA Iris with central opening pupil controls amount of light entering the eye Ciliary body secerets aq humour & contains smooth muscle which responsible for changing shape of lens in accomodation Choroid, vascular layer provides blood supply to RPE & outer ½ of sensory retina

26. IRIS & PUPIL Lies in front of lens & ciliary body Separates ant & post chamber Pupil situated slightly on nasal side It has many ridges and cripts

27. STRUCTURALLY- 5 layers Ant endothelium- continuous with corneal endo Stroma - contains connective tissue with blood vessels, nerves & smooth muscle Smooth muscle- Sphinter pupillae -circular bundle of smooth muscle running around pupillary margine causes constriction of pupil Dilator pupilae -arranged radialy near root of iris causes dilation Post two layered epithelium

28. NERVE SUPPLY Sensory- nasocillary nerve branch of 1 st div of trigeminal nerve Motor- sphinter pupillae-occlomotor nerve Dilator pupillae – nerve derived from cervical sympthatic chain

29. CILLARY BODY Ridge of tissue 6mm wide that extends from scleral spur to ora serrata of retina In A-P section it is roughly an isosceles triangle with base forward iris attached at middle of base Main mass of ciliary body is unstriped muscle fibres called ciliary muscle

30. Inner surface of ciliary body is divided into 2 regiong PARS PLICATA- ant part .Microscopically it has ciliary processes responsible for production of aqueous PARS PLANA- pos part. Relative safe zone & avascular zone for pars plana lensectomy / vitrectomy Covered by 2 layers of epithelium contineous with iris ant & retina post

31. NERVE SUPPLY- Sensory – nasociliary branch of 5 th nerve Ciliary muscle- oculomotor & sympthetic nerves BLOOD SUPPLY- By branch of major circle of iris which is formed by 2 long ciliary (post) artery & 7 ant ciliary arteries

32. FUNCTION OF CILIARY BODY Aq humour formation Help in accomodation for near work Ciliary muscle also help in opening schlemm’s canal thus facilitate aq drainage

33. CHOROID Vascular sheet that separates sclera from retina Attached firmly to the optic nerve & at the points of exit of vortex vein STRUCTURE It consists of 3 layer of blood vessels which are supported on either sides by membrane Outer side- supra choroid (lamina fusca ) Inner side- basal lamina ( bruch’s membrane)

34. 3 layers of vessels OUTER VESSEL LAYER- (of hallar )- Nearest to sclera , contains large vessels (veins) that leads to vortex veins MIDDLE VESSEL LAYER (of scatter) Medium size veins & arterioles INNER CHOROID CAPILLARIES Contains large fenestrated capillaries

35. BRUCH’S MEMBRAE It separates chorio capillaries from retinal pigment epithelium Histologically made up of 5 layers Basement memb of chorio capillaries Outer collagen layer Middle elastic layer Inner collagen layer BM of RPE It is important for blood retinal barrier function

36. BLOOD SUPPLY Short post ciliary arteries-branches of ophthalmic artery, divided into 10-20 branches which perforates sclera around optic nerve & communicate with choriocapillaries Two long posterior ciliary aarteries - perforates sclera on either side of optic arery , via supra choroidal space to ciliary body & divide to form “major arterial circle” of iris Anterior ciliary arteries- terminal branches of muscular arteries of each rectus muscle, supply ciliary body send branch to major arterial circle of iris & tochoriocapillaries Venous blood- from iris ciliary body & choroid collected by series of veins which form 4 vortex veins that drain into sup & inf ophthalmic veins

37. CRYSTALLINE LENS Transparent, bi-convex body of crystalline structure. Lens is held in position that is behind the iris by suspensory ligament called zonules ( of zinn ) which arises from sides of ciliary processes and valley between them. Zonules insert into anterior and posterior lens capsule near equator and extend further on anterior surface more than post surface.

38. STRUCTURE OF LENS 1. Lens Capsule – That envelopes entire lens 2 .Anterior Lens epithelium 3 . Lens substance– Contains cortex( newly formed lens fibres) and nucleus ( dense central area of old lens fibres)

39. LENS CAPSULE--- Smooth,homogenous , acellular highly elastic envelope. Ant capsule is the basement membrane of anterior lens epithelium and thickest basement membrane of the body. Thickest on anterior and posterior surface just central to insertion of zonular fibres . Thinnest on posterior pole. B. LENS EPITHELIUM--- Anterior single layer of cuboidal cells just below capsule. No posterior epithelium. At equator cuboidal cells become columnar and elongated and get involved into lens fibres .

40. C. LENS SUBSTANCE--- Consists of elongated lens cells. Mature lens fibres are cells which have lost their nuclei and form greatest portion of the lens substance. In infantile lens, each fibres start and finish on the anterior and posterior Y sutures. In slit lamp various beams of zone are seen as embryonic( first 3 months of foetal life) Foetal ( 3-8 months of life) Infantile ( upto puberty) Adult( Rest of life)

41. CHAMBERS OF EYE- -- Anterior Chamber Anterior cornea Posterior front surface of iris,lens . Periphery- angle of AC Depth- 2.5 to 3 mm Volume- 0.25ml Posterior Chamber Anterior- iris Posterior- anterior vitreous face Lateral- ciliary processes Medial- lens equator Volume- 0.06ml

42. C. Vitreous Cavity Transparent-gel like structure called vitreous humour . Network of collagen fibres suspended in a viscus liquid containing hyaluronic acid. Anteriorly it has saucer shaped depression for lens called patellar fossa. Here vitreous humour condensed to form anterior vitreous face. It is firmly attached to ciliary epithelium in region of or serrata , peripheral retina, margin of optic disc, posterior to lens capsule. Running down the centre of vitreous from optic disc to posterior pole of lens there is canal called hyaloid canal of cloquet . Embryologically , it is divided into a.primary – mesenchymal, cloquets canal b. secondary– most of adult vitreous c. Tertiary– lens zonules Volume--- 4.5 ml

43. RETINA Transaprent membranous light sensitive coat of the eyeball. Retina developed from inner and outer layers of loosely adherent across a potential space so that they are readily separated by injury or on diseased condition. Outer pigmented epithelium layer remains one cell deep but the inner layer called sensory retina becomes several layered. 10 layered structure— Retinal pigmented epithelium Layer of rod and cones External limiting membrane Outer nuclear layer Outer plexiform layer Inner nuclear layer Inner plexiform layer Ganglion cell layer Nerve fibre layer Internal limiting membrane

44. REGIONS OF RETINA 1. Ora serrata Anterior termination of retina located about 8mm from thr limbus. Only two layers of optic vesicle fuses and continue forward as ciliary epithelium. 2. Central Retina 4-5mm in diameter. Extends from fovea centralis to optic disc nasally and same distance temporally above and below. In the region ganglion cell layer is more than one layered. Central part of this region is called ,macula lutea which contains yellow pigment Xanthopsia . Fovea centralis is a depressed area in the central retina about 3mm temporal to optic disc and 0.8mm below the horizontal meridian. A central depression is called foveola about 0.5mm. Photoreceptors in the fovea are exclusively cones all other layers are displaced peripherally so light falls directly on cones.Foveola is nourished solely by choriocapillary of choroid and does not contain any vessels and hence called FA2

45. 3. Peripheral retina Photoreceptors are mainly rods. Functionally it is divided into temporal retina and nasal retina by a line drawn vertically through the centre of fovea. Ophthalmoscopically we usually use optic nerve as a hub to divide the retina into superior and inferior temporal portions, superior and inferior nasal portions and central retina. Blood supply– Outer portion- Chorioapillaries Inner portion- Mainly by central retinal artery branch of ophthalmic artery which enters optic nerve 10-12 mm posterior to globe.

46. 4 . Extaocular Muscles 6 in number. 4 recti and 2 oblique. Recti are superior, inferior, medial and lateral Obliques are superior and Inferior Origin– Common origin from annular tendon of zinn around optic foramen at the apex of orbit. Insertion– Inserted on sclera as spiral line after piercing the tenon’s capsule. Superior Oblique– At the apex of orbit from annular tendon of zinn runs to the trochlea at upper and inner angle of orbit become tendinous and get inserted in sclera at the superolateral part of posterior pole of globe Inferior Oblique– Arises from lower and inner orbital was near lacrimal fossa and inserted at inferolateral part of posterior pole of globe.

47. All muscles are supplied by Occulomotor nerve except- Lateral rectus– 6 th nerve Superior Oblique– 4 th nerve Action MR– Adduction LR– Abduction SR– Elevation on adduction and intortion IO– Depression on adduction and extortion SO– Depression on abduction and intortion IO– Elevation on Abduction and extortion

48. EYELIDS Thin curtains of skin, muscles, fibrous tissue and mucous membrane. Upper lid limited above by eyebrow and lower lid by cheeks. Each eyelid divided into orbital and tarsal part by a horizontal furrow upper furrow is formed by skin insertion of LPS muscle. Palpebral Aperture – When eye is open eyelids form an elliptical opening called palpebral aperture. Two eyelids meet medially to form medial canthus and lateral form lateral canthus. At inner canthus, there is small locus lacrimal to formed by emminences which bear lacrimal puncta 6mm lateral to angle itself. Small separated knob of skin ‘caruncle’ bearing few hairs or glands. Just lateral to caruncle there is cresentric fold of conjunctiva, plica semilunaris which is similar to nictitating membrane in vertebrates.

49. Lid margin– On free margin of each eyelid are the openings of lacrimal canaliculi eyelasehes and openings of glands. It has 3 layers— Cutaneous layer– Thin,smooth,delicate,elastichaving creases. Subcutaneous layer– Loose areolar tissue without fat. Muscular layer– Orbicularis oculi, LPS, Muller’s muscle Fibrous layer– Orbital septum-upper part, Tarsal plate-lower part Palpebral conjunctiva– Innermost layer of eyelid.

50. Muscles of lid Orbicularis oculi– Closure of lids, blinking, winking,help in drainage of tears. Zsupplied by 7 th nerve. LPS– Present only in upper lid. Elevation of upperlid including upper fornix and helps in formation of upper lid fold. Supplied by 3 rd nerve. Muller’s Muscle– Present in upper and lower lid. Causes elevation of the lids. Supplied by cervical sympathetic chain.

51. Glands of eyelid Meibomian glands– Modified sebaceous glands. Secretes oily secretion of tear film. Glands of Zeis – Sebaceous glands. Glands of Moll– Modified sweat gland. Glands of Krause and Wolfring – Accessory lacrimal gland.

52. Functions of eyelids— Protection of eyeball proper from external injuries.eg-dust Maintains pre corneal tear film Interrupt and limit the amount of light entering the eye. Drainage of tears by lacrimal pump system.

53. LACRIMAL APPARATUS Secretory Portion– Lacrimal gland and accessory ‘Glands of Kausse and Wolfring ’ Drainage portion– Through which the tears are drained into inferior meatus of nose. Lacrimal glands are located on thr anterolateral portion of the roof of the orbit in the lacrimal fossa. Many ducts of the glands open into superotemporal conjunctival fornix. Accessory lacrimal glands– situated deep in conjunctival fornix mostly on temporal side.

54. Drainage Lacrimal puncta– Two small openings situated near the posterior border of free margins of lids about 6mm from inner canthus. It is situated on slight elevation called lacrimal papillae. Two canaliculi– Punctum to lacrimal sac. First directed vertically 1-2mm and then horizontally 6-7mm. These two canaliculi usually open separately in outer wall of sac or they join to form common canaliculi which open into the sac. Lacrimal sac– Lies in lacrimal fossa formed by lacrimal bone. When distended it si 15mm long and 5-6mm wide. Upper portion called fundus of the sac which lies slightly above the level of MPL. Sac is covered by fibrous tissue and fibres of orbicularis oculi muscle.

55. d. NLD– Sac continues below as NLD. 12-14mm long and 3-6mm diameter. Duct passes outwards and downwards and backwards to open into anterior part of outer part of inferior meatus of nose. Upper part of duct is narrowest part. Mucous membrane forms an important valve at the opening in nose called Valve of Hasner .

56. ORBIT Orbits are pear shaped cavities. Medial walls are parallel but lateral walls diverge at an angle of 45. It is roughly 40mm in height width and depth and volume is around 30ml. Contents of orbit– Eyeball and intra-orbital part of optic nerve Retrobulbar fat extra ocular muscles Ophthalmic arteries and veins 3 rd ,4 th ,6 th nerves and first 2 divisions of 5 th nerve Ciliary ganglion Sympathetic plexus Lympathic vessels Tenons capsule and orbital fascia Lacrimal gland and sac

57. Blood supply– Majority is by Ophthalmic Artery Eyelids and conjunctiva have anastomotic blood supply from branches of both external carotid and ophthalmic artery Ophthalmic artery– arises from Internal carotid artery. Enters orbit through optic foramen below and lateral to optic nerve. Its branches are Central retinal artery, 10-20 short posterior ciliary arteries, two long posterior ciliary artery, recurrent meningeal artery, lacrimal artery, many recurrent artery, muscular branches. Anterior ciliary arteries are forward continuation of muscular arteries. External carotid artery– Mainly supply eyelids and conjunctiva. C. Venous Drainage– Superior and inferior orbital veins which drain into cavernous sinus.

58. Nerve Supply— Motor supply 3 rd nerve/ Occulomotor nerve Superior division- SR and LPS Inferior division- MR,IR,IO Short root to ciliary ganglion- Ciliary muscles and sphincter pupillae 2. Trochlear nerve- SO 3. Abducent nerve- LR B. Mixed motor and sensory nerves- Facial nerve- motor to face mainly orbicularis o culi secretory to lacrimal gland C. Sensory nerve Trigeminal nerve- via ophthalmic and maxillary division D. Parasymapthetic supply– 3 rd nerve and facial nerve E. Sympathetic supply– Post gangalionic fibres cervical ganglion

59. LYMPHATIC DRAINAGE Submandibular lymph nodes Pre auricular LN and sometimes post auricular LN

60. VISUAL PATHWAY