ANATOMY OF RETINA FINAL PPT.pptx.........

anatomy of retina

1. Anatomy of Retina Presenter : Dr. Laxmi Dhawal 1 st year Resident, LEIRC

2. Introduction Latin word Rete= Net Inner most tunic of the eyeball Thin, delicate and transparent layer of tissue that extends from optic disc to ora serrata. Mainly has 2 components: 1. Neurosensory layer 2. Pigmented layer Appears purplish-red

3. It has surface area of 266 mm 2. Thickness varies: -Peripapillary region (thickest) : 0.56 mm -Equator: 0.18-0.2 mm -Ora serrata: 0.1 mm

4. Fundus chart-Modified Amsler Dubois Chart +

5. Embryology of retina

6. Major Landmarks: 1. Optic disc 2. Retinal blood vessels 3. Macula lutea 4. Peripheral retina 5. Ora serrata

7. Pale pink structure 1.5 mm diameter. At the disc,all retina layers terminate except nerve fibres,which pass through Lamina cribrosa to run into optic nerve Central depression called physiological cup. Disc appears white due to lamina cribrosa and the medullated nerve fibers behind it and absence of Choroid Blind spot : The area of optic disc where no photoreceptors cell are present, so not sensitive to light. Optic Disc

8. APPLIED ANATOMY Lamina cribrosa is a relatively weak area, bulge out by a rise in pressure inside the eyeball. A rise in cerebrospinal fluid pressure in the meningeal sheath that surrounds the optic nerve cause the optic disc to bulge into the eyeball due external pressure on the optic nerve impedes the axon flow of its fibers.

9. Macula lutea Yellow spot - due to presence of carotenoid pigment Xanthophyll in the ganglion and bipolar cells Dark area - 5.5 mm in diameter in central retina Situated in posterior pole of eyeball , 4mm temporal&0.8mm inferior to centre of optic disc Corresponds to 15degree of visual field, accurate diurnal vision& colour discrimination

10. Fovea centralis Depressed area 1.5mm in diameter Corresponds to 5˚ of visual field & most sensitive part of retina. Foveola 0.35mm in diameter Central floor of Fovea where inner nuclear layer & ganglion cell layer absent Capillary free(avascular zone) of retina Umbo Small central concavity of floor of fovela Corresponding to ophthalmologically visible foveal reflex

11. Cellular layers in Fovea : RPE Photoreceptors ELM ONL Henle’s Layer ILM

12. Foveal avascular zone Also called capillary free zone. Located inside the fovea but outside foveola. Diameter varies from 250-600 microns. Can be determined by FFA CLINICAL SIGNIFICANCE: Important landmark in the treatment of subretinal neovascular membrane by laser. In Diabetic macular ischemia,diameter of avascular zone enlarges.

13. Parafoveal & Perifoveal areas Surrounds the fovea Parafoveal area=0.5 mm diameter,surrounds foveal margin Perifoveal area= 1.5 mm diameter,surrounds parafovea

14. Peripheral retina Near Periphery: area of 1.5 mm around the macula lutea(area centralis). Mid Periphery: 3mm wide zone around the near periphery. Far Periphery: extends from optic disc 9-10 mm on temporal and 16 mm on nasal side in horizontal meridian.

15. Ora serrata Serrated peripheral margin where retina ends and ciliary body starts Serrated much more nasally than temporally Distance from limbus - 6 mm nasally and 7mm temporally From Equator. - 6-8 mm From optic nerve. - 25mm Width-2.1mm temporally 0.7-0.8mm nasally

16. Clinical Significance: It’s a watershed zone between anterior and posterior vascular system so peripheral retinal degeneration is common. Also peripheral retina is attenuated at this region. Externally, ora serrata corresponds to insertion of medial and lateral rectus muscles .

17. E e

18. Microscopic structure of retina

19. Retinal Pigment Epithelium : Single layered hexagonal cells between retina & Bruchs membrane Contains melanin and lipofuscin Total no:4.2 to 6.1 million At macula cells-12-18µm in width 10-14µm in ht At ora serrata cells-60µm in width

20. Firmly adherent to the underlying Bruch’s membrane & loosely to the outer segments of rods & cones. Fine mottling due to unequal pigmentation is Responsible for granular appearance of fundus

21. EM reveals that adjacent RPE cells connected with each other by tight junctions (zonulae occludens & zonulae adherens ) RPE cells at the fovea are taller, thinner & contain larger pigment granules- gives the darker color to macula.

22. Functions of RPE Manufactures pigment which has optical function in absorbing light Transport of metabolites and nutrients through blood-retinal barrier Photoreceptor renewal and recycling of Vit A(visual pigment) Maintains integrity of subretinal space Maintenance of retinal adhesion Phagocytosis & digestion of photoreceptor Regeneration and repair after injury/surgery

23. separation of neurosensory retina from RPE is called Retinal Detachment . Fluid between two layers – Subretinal fluid Clinical correlations

24. APPLIED ANATOMY Drusen Round, yellow lesions, due to failure of the RPE to clear the waste material that gets accumulated between basal lamina of RPE & inner collagenous layer of Bruch’s membrane. Catagorized according to size as- -Small(63 um) -Intermediate(63-124 um) -Large(>125 um)

25. Drusen are further distinguished by their boundaries: Hard -discrete and well demarcated -areas of lipidization or hyalinization - RPE– Bruch membrane complex Soft -amorphous and poorly demarcated diffuse thickening -inner aspects of Bruch membrane Confluent -contiguous drusen without clear boundaries .

26. Central Serous Retinopathy

27. Hyperplasia of RPE - seen in retinitis pigmentosa,syphilis Atrophy of RPE

28. Layers of Rods and Cones End organs of vision that transforms light energy into visual impulse. Rods contains Rhodopsin Cones contain Iodopsin Rods: 120 million Cones: 6.5 million Highest density of cones at fovea average 199000 cones/mm² Falls off rapidly outside the fovea: -6000 3mm away -4000 10 mm away

29. Cone density 40-45 % more on nasal Slightly lower in superior than inferior Rods absent at the fovea in area of 0.35 mm (rod free zone) corresponds to 1.25˚ of visual field. Nasal retina has 20-25 % more rods than temporal and superior has 2 % more than inferior retina.

30. Rod Cells 40-60 microns Outer segment contains visual purple. Contains lipid protein lamellar discs Number 600-1000/rod and each disc 22.5 -24.5 nm thick cilium - Inner segment Ellipsoid (outer ) Myoid (inner ).

31. Cone Cells 40-80 micron Largest at fovea Outer segment -conical and much more shorter Lamellar discs are narrower than that of rods;

32. Inner segment & cilium similar to rods however the ellipsoid is very plump and contains more mitochondria. Unlike rods the inner segment becomes continuous with its nucleus and lies in the outer nuclear layer. Inner cone fiber ends into lateral processes called cone foot or pedicle; lies in the outer plexiform layer.

33. Rods Cones 120 millions 6 millions peripheral Central Scotopic Photopic Rhodopsin iodopsin Cannot see detail Concern with colour and can see detail

34. Interphotoreceptor Matrix & Interphotoreceptor Retinoid binding proteins (IRBP ) Inter-photoreceptor matrix (IPM) complex structure composed of: -proteins -GAGs -Glycoproteins -Proteoglycans e.g. Chondroitin sulfate IPM occupies space between photoreceptor outer segment and RPE. IPM helps in retinal attachment , facilitation of phagocytosis and photoreceptor outer segment alignment.

35. External Limiting Membrane Extends from ora serrata to edge of the optic disc EM shows that the ELM is formed by junctions between Cell membrane of photoreceptors and Muller’s Cells

36. Outer Nuclear Layer Formed by nuclei of the rods and cones Cone nuclei are larger 6-7 microns than the rods 5.5 microns. Lie in a single layer next to the external limiting membrane Rod nuclei form the bulk of the multilayered outer nuclear layer except in cone dominant area; fovea.

37. Number of rows of nuclei and thickness varies in different regions: 1.Nasal to disc: 8-9 layers nuclei; 45 microns thick 2.Temporal. : 4 rows ; 22 microns 3.Foveal. : 10 rows; 50 microns 4.Rest of retina: 1 row of cone & 4 rows of rods; 27mm thickness

38. Outer Plexiform Layer Junction of end organ of vision and first order neurons (bipolar cells). This layer contain synapse and network of branching processes of horizontal cells and bipolar cells along with inner fibers of photoreceptors Thickest in the Macula (51 microns) & consists predominantly of oblique fibers deviated from the fovea known as Henle’s layer.

39. Inner Nuclear Layer resembles outer nuclear layer except it is thinner Disappears at Fovea Rest of the retina: 1. Bipolar cells 2. Horizontal cells 3. Amacrine cells 4. Muller’s Cells 5. Capillaries of central retinal vessels

40. Four layers can be distinguished by light microscopy : The outermost layer with horizontal nuclei The outer intermediate layer with bipolar cells nuclei The inner intermediate layer with muller cell nuclei The innermost layer with amacrine and inter-plexiform cell nuclei

41. Horizontal cells

42. Amacrine cells : Forms connections with axons of the bipolar cells and dendrites and soma of the ganglion cells Muller cells : Fibers from the outer ends extend upto the external limiting membrane & the inner ends goes upto internal limiting membrane.

43. Bipolar Cells 2 nd order neurons of the visual pathway Nucleus of the bipolar cells lies in the Inner nuclear layer dendrites in Outer plexiform layer axons in Inner plexiform layer.

44. Bipolar Cell Types 1. Rod bipolar cells 2.Invaginating & Flat midget bipolar cells 3.Invaginating & Flat diffuse bipolar cells 4.On-center & Off-center blue cone bipolar cells 5.Giant bistratified & Giant diffuse invaginating bipolar cells

45. Consists of synapses between axons of Bipolar cells & dendrites of Ganglion cells and processes of Amacrine cells. Fibers from Muller’s cells course vertically through this layer & side branches form horizontal extending reticulum. Absent in Foveola. Inner Plexiform Layer

46. Cell bodies and nuclei of Ganglion cells lie in this layer Most of retina Single Layer Temporal side of Disc Two Layers Macula 6 - 8 Layers Absent in foveola and optic nv head Classified as: a. W, X, and Y Ganglion cells b. P(P1 and P2) and M(or pparasol ) Ganglion cells c. Monosynaptic & Polysynaptic Ganglion cells Ganglion Cell Iayer

47. Nerve fiber layer contains the axons of the ganglion cells (the so-called 'centripetal' or 'afferent' fibres ), glial cells, a rich capillary bed and centrifugal (or efferent) fibres . Have a bidirectional axoplasmic flow that occurs at two rates The axons remain unmyelinated until they reach the lamina cribrosa of the optic nerve.

48. Thickest at the nasal edge of the disc (20-30 µm) Thinnest portion papillomacular bundle(last to be affected in papilloedema ) The nasal aspect of the optic disc is the most susceptible to changes of papilloedema because of its greater collection of nerve bundles and blood vessels.

49. Nerve Fiber Layer Unmyelinated axons of ganglion cells Converge at Optic nerve head Passthrough Lamina Cribrosa Become ensheathed by myelin posterior to Lamina Cribrosa

50. Thickness - 0.5 – 2 micro m Contents : Centripetal Nerve Fibres (Axons of ganglion cells) Centrifugal Nerve Fibres (Thicker than centripetal) Process of Muller’s cells (interweave with Axons of ganglion cells) Neuroglial cells ( Macroglial & Microglial) Retinal Vessels : rich bed of capillary network but not project on the surface retina

51. Arrangement of Nerve fibre in Retina Nasal half of retina : Superior & inferior radiating fibers ( Srf&Irf ) Macular region. : Papillomacular bundle ( Pmb ) Temporal retina. : Superior and inferior arcuate fibers with horizontal raphe. ( Saf&Iaf )

52. Thickness of nerve fibre at Disc Most lateral quadrant. - thinnest Upper nasal & lower nasal quadrant - thickest Clinical Significance: 1. papilledema appears first in the thickest quadrant and last on the thinnest. 2. Superior and inferior arcuate fibers are most sensitive to glaucomatous damage. 3. Macular fibers lying in the lateral quadrant are resistant to glaucomatous damage and accounts for the retention of central vision till end.

53. Internal Limiting Membrane PAS positive basement membrane Forms interface between the retina & vitreous Fibrils of vitreous merge with the internal lamellae of this membrane. Consists of 4 main elements: 1. Collagen fibrils 2. Proteoglycans esp. Hyaluronic acid of vitreous 3. Basement membrane 4. Plasma membrane of Muller’s cells and other glial cells.

54. Cellular & Synaptic layers: Layer Cell Types Outer Nuclear Layer Rods & Cones Inner Nuclear Layer Horizontal, Bipolar, Amacrine , Muller’s Ganglion cell layer Ganglion nerve fiber, Amacrine Outer Plexiform layer Photoreceptors conn . to bipolar & Horizontal cells Inner plexiform layer Bipolar cells conn . to Amacrine & Ganglion cells

55. Blood supply of Retina Outer plexiform layer gets partly from central retinal artery & partly from choriocapillaries . Fovea is - choriocapillaries . Macular region - from superior & inferior temporal branches of central retinal artery.

56. Cilioretinal artery

57. Arterial circle of Zinn is formed by anastomosis between 2-4 short posterior ciliary arteries and lies in the sclera around the optic nerve .

58. Central retinal artery First branch of Ophthalmic Artery Arises near optic foramen and courses ahead as outside optic nerve in sub arachnoid space centre of optic nerve optic nerve head in Retina

59. Outside ; runs a wavy course forward,below optic nerve,adherent to dural Sheath about 10-15 mm behind eyeball,bends upwards to pierce dura and Arachnoid Subarachnoid space ; again bends upwards at right angle and invaginates Pia to reach centre of optic nerve Centre of optic nerve ; passes anteriorly and pierces lamina cribrosa to Appear inside the eye Optic nerve head ; lies superficially in nasal part of physiological cup,divides into Superior and nasal branch and subdivides into temporal and nasal branch

60. In retina : the four terminal branches they divide dichotomously as they proceed towards ora serrata

61. APPLIED ANATOMY Branched Retinal Artery Occlusion Attenuation of arteries and veins with sludging and segmentation of the blood column. Cloudy white oedematous (ground glass) retina corresponding to the area of ischaemia . One or more occluding emboli may be seen, especially at bifurcation points .

62. Cenral Retinal Artery Occlusion The orange reflex from the intact choroid stands out at the thin foveola, in contrast to the surrounding pale retina, giving rise to a ‘cherry-red spot’ appearance. Peripapillary retina may appear especially swollen and opaque.

63. CENTRAL RETINAL VEIN Formed by the union of tributaries that correspond to branches of CRA. Leaves eyeball through lamina cribrosa. Then veins drain directly into cavernous sinus or superior ophthalmic vein.

64. APPLIED ANATOMY Central Retinal Vein Occlusion T ortuosity and engorgement of all branches of the central retinal vein. Extensive deep dot blot ,flame-shaped haemorrhages involving the peripheral and posterior retina ,cotton-wool spots . Optic disc swelling and hyperaemia .

65. Branched Retinal Vein Occlusion Dilatation and tortuosity of the affected venous segment, flame-shaped and dot/blot haemorrhages,cotton -wool spots and retinal oedema . Changes limited to area drained by obstructed vein. Occlusion of upper temporal branch is more common.

66. Central retinal artery & vein occlusion: In CRAO, there is pallor of retina with cherry red macula. In CRVO, there occurs hemorrhages giving rise to fiery sun appearance.

67. Retinal capillaries Terminal fundus arteriole bends to form superficial and deep capillary network. Superficial capillary network lies at the level of nerve fiber layer deep lies between the inner nuclear and outer plexiform layer..

68. Microaneurysm : -saccular outpouchings of capillary wall -inner nuclear layer

69. Blood-Retinal Barrier

70. Cotton wool spots(soft exudate) - accumlation of neuronal debris in Nerve Fibre Layer.results from ischemic disruption of nerve axons, the swollen ends of which are known as cytoid bodies

71. Retinal Hemorrhage Retinal nerve fiber layer hemorrhage - superficial capillary network Inner nuclear and outer plexiform layer - Deep capillary network

72. Hard exudate Chronic localized oedema Composed of lipoprotein and lipid filled macrophages

73. Age Changes in Retina: Decrease in retinal neurons Decrease in Foveal cones/ Rods Decrease in Astroglial cell RPE & Bruch’s Membrane adherence RPE changes Decrease in NRR Foveal reflex

74. Retina in Children : In children macula poorly developed at birth Rapid differentiation till 4 years Notable changes are: -macular pigmentation -foveal light reflex -cone photoreceptor differentiation Improvement in visual acuity due to: -differentiation of cones -reduction in diameter of rod free zone -increase in foveal cone density.

75. Anthony J Bron, Ramesh C Tripathi, Brenda J Tripathi, Wolff’s Anatomy of the eye and orbit, 8th edition. Snell, Richard s. and Michael A. lemp , Clinical anatomy of the eye,2 nd Edition Myron yanoff 5 th edition American Academy of Ophthalmology . Retina and vitreous. Section 12. 2023-2024 Jack J kanski, 10 th edition References:

76. Thank You