Layers of the eyeball
• The most pathetic person in the world is  someone who has sight, but has no vision.  – Helen Keller
General features• Image focusing system, composed of1. Cornea2. Lens3. Refractive media• Internally black- prevents ‘scatt...
• Refractive media enclosed in 3 coats1. Fibrous [sclera, cornea]2. Vascular/uveal coat [choroid, ciliary body, iris]3. Ne...
Sclera• Posterior 5/6ths• Opaque - composed of dense collagen and  elastic fibres• Thinnest at equator• Pierced by recti m...
• Thickest at back, except where pierced by fibres  of CN II [lamina cribrosa]• ‘cupping’ of optic disc= posterior bulging...
• Pierced by ciliary nerves and arteries, venae  vorticosae• Almost avascular, except ehere connected to  fascial sheath o...
Cornea• Forms anterior 1/6th of fibrous coat• Transparent fibrous tissue laminae• Avascular [no transplant rejection]
Layers1. Corneal epithelium2. Bowman’s membrane /anterior limiting   membrane; scattered collagen fibrils and   ground sub...
4. Descemet’s membrane /posterior limiting  membrane5. Corneal endothelium
Nerve supply• Short and long ciliary nerves• Mainly short ciliary• Corneal reflex pathway; short ciliary nerves→  trigemin...
• Components  choroid, ciliary body, irisCHOROID• Thin, pigmented• Outer layer separated from sclera by  suprachoroid lami...
• Rods and cones nourished by choroidal  capillaries• Venae voricosae [4-5] drain choroid- exit  through sclera
Ciliary body• Continuous with choroid behind and iris in front• Like a flat ring applied to inner scleral surface• Thick i...
• Ciliary muscle in scleral surface• Vitreous surface – bilayered epithelium [outer  pigmented, inner nonpigmented]• Layer...
• Scleral surface projected into70-80 ciliary  processes that lie in reciprocal grooves on  anterior surface of vitreous b...
Iris• Attached at periphery to anterior surface of  ciliary body and a narrow rim of sclera to form  iridocorneal angle of...
• Amount of pigment increases with age• Color is variable in different individuals
Sphincter pupillae• Circular smooth muscle• Supplied from Edinger – Westphal nucleus of  CN III
Dilator pupillae• Radial smooth muscle• Supplied by cervical sympathetics• Preganglionic neurons lie in T1 segment of  spi...
Trabecular meshwork and scleralvenous sinus
Lens• Transparent, biconvex• More convex posteriorly• Transparent ,elastic capsule• Posteriorly rests on vitreous, anterio...
• Centrally , single layer of cubical cells• Peripherally , cells elongate to produce fibres• Increase in length leads to ...
Suspensory ligament/zonule• Series of delicate fibrils attached to ciliary  processes and through the furrows between  the...
• Holds lens flattened under tension• Contraction of ciliary muscle→ forward  displacement of choroid and ciliary body• Th...
•   Delicate•   Outer surface in contact with choroid•   Inner surface in contact with vitreous•   Ora serrata- anterior l...
Retina - components1. Retinal pigment epithelium2. Neural retina
Retinal pigment epithelium• Outer layer• Simple cuboidal melanin-containing cells• Firm attachment to choroid via Bruch’s ...
Neural retina• Contains light – sensitive receptors [ rods and  cones] + complex neuronal networks• Potential space exists...
Components of neural retina• Nonvisual part; anterior to ora serrata- lines  inner aspect of ciliary body and posterior su...
Optic disc• i.5 mm dia.• Site of entry of CN II• Overlies lamina cribrosa of sclera• Deepened to a variable degree to form...
Fundus• Disc and whole of surrounding area at the back  of the eye seen with ophthalmoscopeMacula lutea –• yellowish shall...
Fovea centralis•   Shallow central pit in macula•   Thinnest area of retina•   Avascular•   No rods•   High concentration ...
Arrangement• Outer layer- pigmented cells attached to choroid• Not a firm attachment• In retinal detachment- pigmented cel...
Physiological arrangement• Similar to any sensory pathway• 1st order neuron – bipolar cell – peripheral  process connected...
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Eye layers 1

  1. 1. Layers of the eyeball
  2. 2. • The most pathetic person in the world is someone who has sight, but has no vision. – Helen Keller
  3. 3. General features• Image focusing system, composed of1. Cornea2. Lens3. Refractive media• Internally black- prevents ‘scatter effect’• In front of iris – anterior chamber• Behind the iris – posterior chamber
  4. 4. • Refractive media enclosed in 3 coats1. Fibrous [sclera, cornea]2. Vascular/uveal coat [choroid, ciliary body, iris]3. Nervous [retina]
  5. 5. Sclera• Posterior 5/6ths• Opaque - composed of dense collagen and elastic fibres• Thinnest at equator• Pierced by recti muscles
  6. 6. • Thickest at back, except where pierced by fibres of CN II [lamina cribrosa]• ‘cupping’ of optic disc= posterior bulging of disc in sustained ↑in intraocular pressure• Blends with dura mater• Site of muscle insertion
  7. 7. • Pierced by ciliary nerves and arteries, venae vorticosae• Almost avascular, except ehere connected to fascial sheath of eye and bulbar conjunctiva
  8. 8. Cornea• Forms anterior 1/6th of fibrous coat• Transparent fibrous tissue laminae• Avascular [no transplant rejection]
  9. 9. Layers1. Corneal epithelium2. Bowman’s membrane /anterior limiting membrane; scattered collagen fibrils and ground substance3. Corneal stroma/substantia propria• 200 collagen fibril lamellae• Scattered fibroblasts• Transparency because of lattice arrangement
  10. 10. 4. Descemet’s membrane /posterior limiting membrane5. Corneal endothelium
  11. 11. Nerve supply• Short and long ciliary nerves• Mainly short ciliary• Corneal reflex pathway; short ciliary nerves→ trigeminal ganglion→ main CN V sensory nucleus→ reticular formation→ both CN VII motor nuclei [both orbicularis oculi muscles act]
  12. 12. • Components choroid, ciliary body, irisCHOROID• Thin, pigmented• Outer layer separated from sclera by suprachoroid lamina [delicate connective tissue]• Inner layer firmly attached to pigmented layer of retina
  13. 13. • Rods and cones nourished by choroidal capillaries• Venae voricosae [4-5] drain choroid- exit through sclera
  14. 14. Ciliary body• Continuous with choroid behind and iris in front• Like a flat ring applied to inner scleral surface• Thick in front, thin behind• Triangular ;2 lond sides in contact with sclera and vitroeus• Attachment of iris halfway along flat anterior short base
  15. 15. • Ciliary muscle in scleral surface• Vitreous surface – bilayered epithelium [outer pigmented, inner nonpigmented]• Layers represent pigment and nervous layers of retina
  16. 16. • Scleral surface projected into70-80 ciliary processes that lie in reciprocal grooves on anterior surface of vitreous body
  17. 17. Iris• Attached at periphery to anterior surface of ciliary body and a narrow rim of sclera to form iridocorneal angle of anterior chamber• Perforated centrally by pupil• Main bulk- vascular connective tissue connective tissue• Amount of melanin granules increases from anterior to posterior
  18. 18. • Amount of pigment increases with age• Color is variable in different individuals
  19. 19. Sphincter pupillae• Circular smooth muscle• Supplied from Edinger – Westphal nucleus of CN III
  20. 20. Dilator pupillae• Radial smooth muscle• Supplied by cervical sympathetics• Preganglionic neurons lie in T1 segment of spinal cord
  21. 21. Trabecular meshwork and scleralvenous sinus
  22. 22. Lens• Transparent, biconvex• More convex posteriorly• Transparent ,elastic capsule• Posteriorly rests on vitreous, anteriorly in contact with iris• 10 mm dia., 4 mm thick
  23. 23. • Centrally , single layer of cubical cells• Peripherally , cells elongate to produce fibres• Increase in length leads to increase in lens substance
  24. 24. Suspensory ligament/zonule• Series of delicate fibrils attached to ciliary processes and through the furrows between them, further back on ciliary body• Most fibres attach themselves to the lens- mostly in front and a few behind the circumference
  25. 25. • Holds lens flattened under tension• Contraction of ciliary muscle→ forward displacement of choroid and ciliary body• This relieves some tension exerted by zonule on the lens; makes it more globular→ increased refractive power [Accomodation]
  26. 26. • Delicate• Outer surface in contact with choroid• Inner surface in contact with vitreous• Ora serrata- anterior limit of light ssensitive area• Beyond ora serrata- thin light insensitive layer continues as epithelial layers of ciliary body and iris
  27. 27. Retina - components1. Retinal pigment epithelium2. Neural retina
  28. 28. Retinal pigment epithelium• Outer layer• Simple cuboidal melanin-containing cells• Firm attachment to choroid via Bruch’s membrane [thin refractile layer –multilaminar]
  29. 29. Neural retina• Contains light – sensitive receptors [ rods and cones] + complex neuronal networks• Potential space exists between neural retina and RPE• Layers can be separated mechanically• Eye disease or trauma also leads to separation [Retinal detachment]
  30. 30. Components of neural retina• Nonvisual part; anterior to ora serrata- lines inner aspect of ciliary body and posterior surface of iris• Photosensitive /visual part; lines inner surface of eye posterior to ora serrata, except where it is pierced by CN II
  31. 31. Optic disc• i.5 mm dia.• Site of entry of CN II• Overlies lamina cribrosa of sclera• Deepened to a variable degree to form a ‘physiological’ cup• Insensitive to light – ‘blind spot’
  32. 32. Fundus• Disc and whole of surrounding area at the back of the eye seen with ophthalmoscopeMacula lutea –• yellowish shallow depression, avascular• 3mm lateral to optic disc
  33. 33. Fovea centralis• Shallow central pit in macula• Thinnest area of retina• Avascular• No rods• High concentration of cones=site of most acute vision
  34. 34. Arrangement• Outer layer- pigmented cells attached to choroid• Not a firm attachment• In retinal detachment- pigmented cells remain in position; rods and cones and other layers displaced onwards
  35. 35. Physiological arrangement• Similar to any sensory pathway• 1st order neuron – bipolar cell – peripheral process connected to rods and cones• Synapses with 2nd order neurons – ganglion cell• Passes to thalamus [lateral geniculate body] which has 3rd order neurons• Axons pass through retrolentiform part of internal capsule to visual cortex

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