ORBIT II

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ORBIT II

• Dr. Mujahid Khan

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Blood Supply

• Ophthalmic Artery
• It is a branch of Internal Carotid Artery
• Emerges from cavernous sinus
• Runs forward lateral to the optic nerve
• Reaches the medial wall of the orbit
• Gives away several branches

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Central Artery of Retina

• Is a small branch
• Pierces the meningeal sheath of optic nerve
  gain entrance to the nerve
• Enters the eyeball at the centre of optic disc
• Divides into 2 branches called end arteries

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Ciliary Arteries

• Can be divided in two groups
• Anterior group enters the eyeball near the
  corneoscleral junction
• Posterior group enters the eyeball near the optic
  nerve

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Lacrimal Artery

• It supplies the lacrimal gland

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Supratrochlear Supra orbital Arteries

• Are distributed to the skin of the forehead

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Ophthalmic Veins

• Superior ophtalmic vein communicates in front
  with the facial vein
• Inferior ophthalmic vein communicates with the
  pterygoid plexus through the inferior orbital
  fissure
• Both the veins pass backward through superior
  orbital fissure drain into cavernous sinus

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Lymph vessels

• No lymph nodes or vessels are present in the
  orbital cavity

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The Eye

• Eyeball consists of 3 coats
• The fibrous coat
• The vascular pigmented coat
• The nervous coat

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Fibrous Coat

• Made up of posterior opaque part, the sclera
  anterior tranparent part cornea

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Sclera

• Composed of dense fibrous tissue
• Pierced by optic nerve posteriorly and is fused
  with the dural sheath of the nerve
• Lamina Cribrosa is the area of sclera that is
  pierced by optic nerve fibers
• Also pierced by ciliary arteries nerves
• Is continuous in front with the cornea

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Cornea

• Is transparent
• Responsible for refraction of light entering the
  eye
• It is in contact with the aqueous humor
  posteriorly

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Vascular Pigmented Coat

• Consists from behind forward
• Choroid
• Ciliary body
• Iris

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Choroid

• Is composed of an outer pigmented layer and an
  inner highly vascular layer

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Ciliary Body

• Is continuous posteriorly with choroid
• Anteriorly lies behind the peripheral margin of
  iris
• Composed of
• Ciliary ring
• Ciliary process
• Ciliary muscle

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• Ciliary ring is the posterior part of the body,
  has shallow grooves, Ciliary striae
• Ciliary processes are radially arranged folds
  connects the suspensory ligaments of the lens
• Ciliary muscle is composed of meridianal and
  circular fibers of smooth muscles

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Iris

• Is a thin, contractile, pigmented diaphragm
• Has central aperture called pupil
• Is suspended in the aqueous humor between the
  cornea and lens
• Its periphery is attached to the anterior surface
  of the ciliary body
• Divides the space between cornea and lens into
  anterior posterior chambers

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Nervous Coat or Retina

• Consists of an outer pigmented layer inner
  nervous layer
• Its outer surface is in contact with choroid
• Inner layer in contact with the vitreous body
• Posterior three-fourths is the receptor organ
• Macula lutea is the oval yellowish area in the
  center of the posterior part
• Fovea centralis is the central depression

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Retina

• Optic nerve leaves the retina to medial side of
  macula lutea by the optic disc
• Optic disc is depressed at its center, where it
  is pierced by central artery
• Optic disc is insensitive to light and referred
  as blind spot
• Optic disc is seen to be pale pink with
  ophthalmoscope examination

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Optic Nerve

• Enters the orbit from middle cranial fossa by
  passing through the optic canal
• Accompanied by ophthalmic artery
• It is surrounded by sheaths of pia, arachnoid and
  dura maters
• It runs forward and laterally within the cone of
  the recti muscles

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Optic Nerve

• Pierces the sclera at a point medial to the
  posterior pole
• The meninges fuse with the sclera
• The subarachnoid space extends forward as far as
  the eyeball
• A rise in pressure of the CSF within the cranial
  cavity is transmitted to the back of the eyeball

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Nasociliary Nerve

• Arises from the ophthalmic division of the
  trigeminal nerve in the lateral wall of the
  cavernous sinus
• Enters the orbit through the lower part of the
  superior orbital fissure
• Crosses above the optic nerve with the ophthalmic
  artery
• Ends by dividing into the anterior ethmoidal and
  infratrochlear nerves

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Branches of Nasociliary Nerve

• Communicating branch to the ciliary ganglion
• The long ciliary nerves (2-3 in number)
• Posterior ethmoidal nerve
• Infratrochlear nerve
• Anterior ethmoidal nerve
• External nasal nerve

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Ciliary Ganglion

• It is about the size of a pinhead
• It is a parasympathetic ganglion
• Situated in the posterior part of the orbit on
  the lateral side of the optic nerve
• Receives its preganglionic parasympathetic fibers
  from the oculomotor nerve via nerve to inferior
  oblique
• The postganglionic fibers leave the ganglion in
  the short ciliary nerves

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Contents of the Eyeball

• Aqueous Humor
• Vitreous body
• lens

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Aqueous Humor

• Clear fluid fills the ant. post. Chambers
• Is a secretion from ciliary processes
• Drained away through canal of Shlemm
• Obstruction to its draining results in glaucoma
• Glaucoma causes degenerative changes in the
  retina

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Aqueous Humor

• Supports the wall of the eyeball
• Maintains its optical shape
• Nourishes the cornea and lens
• Removes the products of metabolism

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Vitreous Body

• Is a tranparent gel
• Fills the eyeball behind the lens
• Hyaloid canal is a narrow channel runs through it
  extends from optic disc to posterior surface of
  the lens
• Canal is filled with hyaloid artery in fetus
• Contribute in the magnifying power of eye
• Supports posterior surface of lens

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Lens

• Is a transparent, biconvex structure
• Enclosed in a transparent capsule
• Situated behind the iris in front of vitreous
• Encircled by ciliary process
• Assumes globular shape due to tense elastic
  capsule
• Its circumference attached to the ciliary process
  by suspensory ligament

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Lens

• Suspensory ligament keeps the elastic lens
  flattened
• Ciliary muscle contracts to accommodate the eye
  for close objects
• Lens becomes dense less elastic in advance age
  resulting in presbyopia
• Glasses are used to overcome presbyopia