ORBIT II Dr. Mujahid Khan

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

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

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

Lacrimal Artery It supplies the lacrimal gland It supplies the lacrimal gland

Supratrochlear & Supra orbital Arteries Are distributed to the skin of the forehead Are distributed to the skin of the forehead

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

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

The Eye Eyeball consists of 3 coats: Eyeball consists of 3 coats: The fibrous coat The fibrous coat The vascular pigmented coat The vascular pigmented coat The nervous coat The nervous coat

Fibrous Coat Made up of posterior opaque part, the sclera & anterior tranparent part cornea Made up of posterior opaque part, the sclera & anterior tranparent part cornea

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

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

Vascular Pigmented Coat Consists from behind forward: Consists from behind forward: Choroid Choroid Ciliary body Ciliary body Iris Iris

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

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

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

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

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

Retina Optic nerve leaves the retina to medial side of macula lutea by the optic disc 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 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 insensitive to light and referred as blind spot Optic disc is seen to be pale pink with ophthalmoscope examination Optic disc is seen to be pale pink with ophthalmoscope examination

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

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

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

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

Ciliary Ganglion It is about the size of a pinhead It is about the size of a pinhead It is a parasympathetic ganglion It is a parasympathetic ganglion Situated in the posterior part of the orbit on the lateral side of the optic nerve 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 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 The postganglionic fibers leave the ganglion in the short ciliary nerves

Contents of the Eyeball Aqueous Humor Aqueous Humor Vitreous body Vitreous body lens lens

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

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

Vitreous Body Is a tranparent gel Is a tranparent gel Fills the eyeball behind the lens 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 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 Canal is filled with hyaloid artery in fetus Contribute in the magnifying power of eye Contribute in the magnifying power of eye Supports posterior surface of lens Supports posterior surface of lens

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

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