Retina class 7th semester


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Retina class 7th semester

  1. 1. Dr.Narang Retina
  3. 3. Gross Anatomy <ul><li>Retina extends from the optic disc to the ora serrata. </li></ul><ul><li>It is divided into two distinct regions: </li></ul><ul><li>posterior pole and </li></ul><ul><li>peripheral retina separated by the so called retinal equator. </li></ul>
  4. 4. Posterior pole <ul><li>It refers to the area of the retina posterior to the retinal equator. </li></ul><ul><li>The posterior pole of the retina includes two distinct areas: </li></ul><ul><li>optic disc and </li></ul><ul><li>macula lutea </li></ul>
  5. 5. Macula lutea . <ul><li>It is also called the yellow spot . </li></ul><ul><li>It is comparatively deeper red than the surrounding fundus and is situated at the posterior pole temporal to the optic disc. </li></ul><ul><li>Fovea centralis is the central depressed part of the macula. It is about 1.5 mm in diameter and is the most sensitive part of the retina. In its Center is a shining pit called foveola . </li></ul><ul><li>An area about 0.8 mm in diameter (including foveola and some surrounding area) does not contain any retinal capillaries and is called foveal avascular zone (FAZ). </li></ul><ul><li>Surrounding the fovea are the parafoveal and perifoveal areas. </li></ul>
  6. 6. Structure of fovea centralis <ul><li>In this area, there are no rods. </li></ul><ul><li>Cones are tightly packed and other layers of retina are very thin. </li></ul><ul><li>Its central part (foveola) largely consists of cones and their nuclei covered by a thin internal limiting membrane. </li></ul><ul><li>All other retinal layers are absent in this region. </li></ul><ul><li>In the foveal region surrounding the foveola, the cone axons are arranged obliquely (Henle’s layer or outer plexiform layer) to reach the margin of the fovea. </li></ul>
  7. 7. Fovea centralis
  8. 8. Peripheral retina <ul><li>It refers to the area bounded posteriorly by the retinal equator and anteriorly by the ora serrata. </li></ul>
  9. 9. Optic disc <ul><li>It is a pink coloured , well-defined circular area of 1.5-mm diameter. </li></ul><ul><li>At the optic disc all the retinal layers terminate except the nerve fibres, which pass through the lamina cribrosa to run into the optic nerve. </li></ul><ul><li>A depression seen in the disc is called the physiological cup . The central retinal artery and vein emerge through the centre of this cup. </li></ul>
  11. 12. Internal limiting membrane <ul><li>It is the innermost layer and separates the retina from vitreous. </li></ul><ul><li>It is formed by the union of terminal expansions of the Muller’s fibres. </li></ul><ul><li>It is essentially a basement membrane. </li></ul>
  12. 13. Nerve fibre layer (stratum opticum) <ul><li>It consists of axons of the ganglion cells, running parallel to retinal surface. </li></ul><ul><li>The layers increase in depth as it converges to optic disc. </li></ul><ul><li>The nerve fibers are fine and non-medullated </li></ul><ul><li>It pass through the lamina cribrosa to form the optic nerve </li></ul>
  13. 14. Ganglion cell layer <ul><li>It mainly contains the cell bodies of ganglion cells (the second order neurons of visual pathway). </li></ul><ul><li>There are two types of ganglion cells: </li></ul><ul><li>- The midget ganglion -cells are present in the macular region. each such cell synapses with single bipolar cell. </li></ul><ul><li>- Polysynaptic ganglion - cells lie predominantly in peripheral retina .Each such cell may synapse with upto a hundred bipolar cells </li></ul>
  14. 15. Inner plexiform layer <ul><li>It essentially consists of connections of bipolar cells with the ganglion cells and amacrine cells. </li></ul>
  15. 16. Inner nuclear layer <ul><li>It mainly consists of nuclei of bipolar cells. </li></ul><ul><li>It also contains nuclei of amacrine and Muller’s cells </li></ul><ul><li>Capillaries of central artery of retina, but outer layers are avascular. </li></ul><ul><li>The bipolar cells constitute the first order neurons. </li></ul>
  16. 17. Outer plexiform layer <ul><li>The Innermost portion of each rod and cone cell is swollen with lateral processes known as spherules and pedicles respectively. </li></ul><ul><li>This layer consists of connections of rod spherules and cone pedicles with the dendrites of bipolar cells and horizontal cells. </li></ul>
  17. 18. Outer nuclear layer <ul><li>It consists of nuclei of the rods and cones. </li></ul><ul><li>Cone nuclei are larger and more oval and carry a layer of cytoplasm </li></ul>
  18. 19. External limiting membrane <ul><li>It is a fenestrated membrane, on which rods and cones rest and their processes pierce </li></ul>
  19. 20. Photoreceptor layer <ul><li>Rods and cones are the end organs of vision and are also known as photoreceptors . </li></ul><ul><li>Rods contain a photosensitive substance visual purple (rhodopsin) and subserve the peripheral vision and vision of low illumination ( scotopic vision). </li></ul><ul><li>Cones also contain a photosensitive substance and are primarily responsible for highly discriminatory central vision ( photopic vision ) and colour vision. </li></ul>
  20. 21. Pigment epithelium. <ul><li>It is the outermost layer of retina. </li></ul><ul><li>It consists of a single layer of cells containing pigment. </li></ul><ul><li>The cells of RPE contain varying amount of melanin. </li></ul><ul><li>Cells are taller at fovea and contain more pigment. </li></ul><ul><li>Around the Optic disc they are heaped up as ‘ choroidal ring ’ </li></ul><ul><li>It is firmly adherent to the underlying basal lamina (Bruch’s membrane) of the choroid. </li></ul>
  21. 22. Blood supply <ul><li>Outer four layers of the retina- choroidal vessels </li></ul><ul><li>Inner six layers- central retinal artery, which is a branch of the ophthalmic artery. </li></ul>
  22. 23. CRAO <ul><li>C entral retinal artery emerges from centre of the physiological cup of the optic disc and divides into four branches. </li></ul><ul><li>These are end arteries i.e., they do not anastomose with each other. </li></ul>
  23. 24. Predisposing factors: <ul><li>Hypertension </li></ul><ul><li>Cardiovascular diseases </li></ul>
  24. 25. Etiology <ul><li>Thrombophilic disorders. </li></ul><ul><li>Emboli from the carotid artery and those of cardiac origin(20%) </li></ul><ul><li>Atherosclerosis-related thrombosis at the level of lamina cribrosa(75%). </li></ul><ul><li>Arteritis with obliteration. </li></ul><ul><li>Angiospasm </li></ul><ul><li>Raised intraocular pressure </li></ul>
  25. 26. Symptoms : <ul><li>Sudden,painless loss of vision. </li></ul><ul><li>Amaurosis fugax </li></ul>
  26. 27. Sign’s <ul><li>Red reflex absent. </li></ul><ul><li>Marked narrowing of large arteries, arterioles invisible. </li></ul><ul><li>Within few hours retina become milky white because of oedema. </li></ul><ul><li>Within a day or two macular area show cherry red spots because of choroid shining through thin retina. </li></ul><ul><li>When obstruction is incomplete, column of venous blood has cattle tract appearance. </li></ul><ul><li>After few weeks oedema subsides , atrophic changes occur(optic nerve atrophy/attenuated thread like arteries). </li></ul><ul><li>No PL/PR </li></ul>
  27. 28. Treatment <ul><li>Immediate lowering of IOP –massage /IV mannitol /A.C. paracentesis . </li></ul><ul><li>Vasodilator and inhalation of mixture of 5%CO2 and 95%O2. </li></ul><ul><li>Anticoagulants –IV heparin </li></ul><ul><li>IV steroids –giant cell arteritis </li></ul>
  28. 29. Prognosis: <ul><li>>6 hours –No return of central vision. </li></ul>
  29. 30. CRVO <ul><li>The retinal veins: These follow the pattern of the retinal arteries. </li></ul><ul><li>The central retinal vein drains into the cavernous sinus directly or through the superior ophthalmic vein </li></ul>
  30. 31. Predisposing Factors <ul><li>Age :6 th /7 th decade(2 nd decade in case of non ischaemic) </li></ul><ul><li>Systemic hypertension </li></ul><ul><li>Raised IOP </li></ul><ul><li>Diabetes </li></ul><ul><li>Hyperviscosity syndrome </li></ul><ul><li>Periphlebitis </li></ul>
  31. 32. Pathogenesis <ul><li>External compression on the vein </li></ul><ul><li>Venous stasis </li></ul><ul><li>Degenerative disease of venous endothelium </li></ul>
  32. 33. Types: <ul><li>Non Ischaemic/Venous stasis retinopathy/Partial CRVO=75% </li></ul><ul><li>Ishchaemic CRVO/haemorrhagic CRVO/Complete CRVO=25% </li></ul>
  33. 34. Non Ischaemic Symptom: <ul><li>Vague U/L fogginess of vision initially. </li></ul><ul><li>V/A remains good. </li></ul><ul><li>Vitreous hemorrhage never present </li></ul><ul><li>Mild pupillary defect </li></ul>
  34. 35. Signs: <ul><li>Mild tortuosity and dilatation of retinal veins. </li></ul><ul><li>Dot and blot and flame shaped haemorrhage. </li></ul><ul><li>Optic disc swelling </li></ul><ul><li>Macular oedema may or not- permanent impaired vision but normally 50% regain VA as Macular oedema resolves. </li></ul><ul><li>Circulating IgM raised in most,leading to phlebitis of central vein in optic head ,hence fundus picture resemble venous thrombosis </li></ul>
  35. 36. Ischaemic CRVO Symptoms : <ul><li>VA- marked reduced </li></ul>
  36. 37. Signs <ul><li>Marked tortuosity and engorged retinal veins. </li></ul><ul><li>Massive superficial and deep haemorrhages. </li></ul><ul><li>Cotton wool exudates. </li></ul><ul><li>Optic disc swelling and hyperaemia. </li></ul><ul><li>Macular oedema and haemorrhage. </li></ul><ul><li>Bunches of tortuous new vessels formed upon optic disc. </li></ul><ul><li>Eventual atrophy of affected retina. </li></ul><ul><li>Fundus described as BLOOD AND THUNDER FUNDUS </li></ul><ul><li>Obstruction of central vein just behind lamina cribrosa ,peripheral at bifurcation as in arterisclerotic </li></ul>
  37. 38. Prognosis: <ul><li>50% develop rubeosis and neovascular glaucoma within 3 months of initial occlusion aka 90 days glaucoma. </li></ul><ul><li>Pre-retinal or vitreous haemorrhage secondary to NVD </li></ul>
  38. 39. Management <ul><li>It is usually not required. </li></ul><ul><li>The condition resolves with almost normal vision in about 50 percent cases. </li></ul><ul><li>Visual loss in rest of the cases is due to chronic cystoid macular oedema, for which no treatment is effective. </li></ul><ul><li>However, a course of oral steroids for 8-12 weeks may be effective. </li></ul><ul><li>Patient should be followed up closely for rubeosis iridis, as prompt treatment in early cases by PRP. </li></ul>