Anatomy Of The Eye Flashcards
Parts of the eye
Eyeball
Adnexia
Orbit
Eyeball layers
- Outer fibrous layer_ cornea (ant 1/6th) and schlera (post 5/6th) schlero corneal junction is limbus
- Middle vascular layer (uveal tract)_ choroid, iris, ciliary body
- Inner nervous layer _ retina
Lens attaches to ciliary body via suspensory ligament
Imp of surgical limbus:
No conjunctiva is present here
Segments of eyeball
Ant and post segment divided by an imaginary line passing through ciliary body , post surface of ciliary ligament and post surface of lens
Contents of ant segment
Cornea
Aq humor
Limbus
Ciliary body
Suspensory ligament
Lens
Part of schlera overlying the ciliary body
Pupil
Contents of post segment
Schlera
Choroid
Retina
Vitreous humor
Optic nerve
Chambers of eyeball
Ant chamber(between cornea and iris)
Posterior chamber( btw lens and iris)
Vitreous humour( btw lens and retina)
Boundary of ant chamber
Anteriorly: post surface of cornea
Posteriorly: ant surf of iris and pupil occupied by lens, ciliary body
Laterally:angle of ant chamber where there is canal of schemn
Where is the angle
Meetingoint of two imaginary lines
One arm is post surf of cornea
Another arm is ant surf of iris
How is the angle formed
Abt part of ciliary body
Root of iris
Trabecular network
Canal of schlemn
Schleral spur
Swalbe’s line
Content of ant chamber
Aqueous humor
Boundary of post chamber
Anteriorly:post surface of iris
Posteriorly:lens and suspensory ligament
Middle and side: ciliary body and suspensory ligament
Base: ciliary body
Apex: meeting point of iris and lens
Content of post chamber
Aqueous humor
Layers of cornea
Abcde
Anterior epithelium
Bowman’s membrane
Corneal stroma
Descemet’s membrane
Endothelium
Nutrition of cornea
Anterior part: from atmosphere air, tear
Posterior part: from aqueous humor
Peripheral part: limbal capillaries
Corneal nerve supply
Only sensory no motor nerve supply
Long ciliary nerve. Branch of opthalmic div of trigeminal nerve
Intra and inter epithelial nerve supply
Functions of cornea
Refractive media
Contributes to refractive power of eye +43D
Protective mechanism
Forms fibrous layer
Maintains intraocular pressure
Normal power of eye is +58D.
How transparency is maintained
6.Corneal epithelium: cornea must be dehydrated for clear vision and epithelium acts as a clear barrier
5.Stroma: regular arrangement of collagen does not allow accumulation of water
4.Endothelium: na k pump drives water from cornea and makes it dehydrated
1.Absence of blood vessels
2.Normal intra ocular pressure
3. Demyelinated nerve fibers
Structure of iris
Anterior epithelium
Posterior epithelium
Iris stroma
Sphincter pupillae circular muscle causes miosis on contraction parasym ns
Dilator pupillae radial muscle causes mydriasis on contraction sympathy ns
Ciliary body
Blood vessels producing aq humour
Muscles
Ciliary epithelium… Pigmented and non pigmented
Structure of ciliary body
Pars plicata - ant part of ciliary body containing ciliary processes
Pars plana- post part of ciliary body devoid of ciliary processes
Ciliary muscle ns and action
Parasympathetic nerve supply
Action is contraction of muscle and relaxation of suspensory ligament which causes the anterior posterior thickness of lens to be increased
Which increases power of lens helping in accomodation
Func of ciliary body
Produces aq humour from ciliary processe and maintain intra ocular pressure
Helps in eye accomodation for near vision
Produces hyaluronic acid for vitreous humour
Intraocular muscles
Sphincter pupillae- parasym ns- contraction causes miosis
Dilator pupillae - symp ns- contraction causes mydriasis
Ciliary muscle - parasympathetic ns- produces aq humor
And helps opin accomodation
Retina layers
Pigmented epithelium
Photo receptors rods and cones
External limiting membrane
Outer nuclear layer
Outer plexiform layer
Inner nuclear layer
Inner plexiform layer
Ganglionic cell layer
Nerve fiber layer
Internal limiting membrane
Blood supply of retina
Outer 1/3 upto outer nuclear layer : choroid by diffusion
Inner 2/3rd upto inner nuclear layer: central retinal artery
Junction of outer 1/3rd and inner 2/3rd: both
Func of retina
Visual acuity
Visual field
Color of vision
Visual pathway
Papillary reflex
Accomodation reflex
Structure of lens
Capsule: ant( less curved for easy accomodation) and posterior( more curved)
Fiber: cortex and nucleus
Epithelium
Func of lens
Acts as refractive media and converges to focus point on retina
Gives power to eye +15 D
Helps in accomodation of near vision
Adnexal structures
They are associated structures which are not a part of eyeball proper
Eyelid and eyelashes eyebrow
Extraocular muscles
Conjunctiva
Lacrimal apparatus (gland sac and ducts)
Ciliary ganglion
Layers of eyelid
7 layers
Skin
Layer of Subcutaneous areolar tissue
Layer of striated muscle-Orbicularis oculi muscle+ levator palpebrae superioris
Sub muscular areolar tissue
Fibrous layer - lower part: tarsal plate
Upper part : orbital septum
Layer of non striated muscle-Mullers muscle
Conjunctiva
These are
Meibomian gland
These are 25-30 glands present in tarsal plate of each eye. They are situated away from lid margin but their ducts come down vertically and open in lid margin. Their secretion comes down mixed with conjunctiva and cornea and make a thin filmy layer known as tear film. Helps in blinking of eye.
Glands of eyelid
Meibomian gland
Gland of mall
Gland of zeis
Gland of kraus
Gland of wolfring
Musvles of eyelid
Orbicularis oculi- facial nerve- closes the eye
Levator palpebrae superioris- oculomotor nerve- elevates upper eyelid
Muellers muscle- sympathetic nerve- elevates eyelid
Eyelashes
Upper eyelash.. 102- 150. Forward upward and backward
Lower eyelash 50- 75
Forwards downwards and backwards
Extra ocular muscles
4 recti.. sup inf lateral medial
2 oblique sup and inf
1 levator palpebrae superioris
Origin: from annulus tendinous ring near optic foramen
Except superior oblique- from ant part of floor of orbit)
Insertion: sclera
Ns: all occulomotor(3) except LR from abducens(6) and SO from trochlear(4)
Action of extra ocular muscles
SR: elevation adduction intortion
IR:depression adduction extortion
LR: abduction
MR: adduction
SO:depression abduction intortion
IO:elevation abduction extortion
LPS: elevates upper eyelid
Conjunctiva
Translucent membrane which connects the eyeball with eyelid
It starts from limbus covers the sclera/eyeball and reflects back and attaches to posterior surface of eyelid.
Parts: bulbar conjunctiva
Palpebral conjunctiva
Fornix- upper lower medial lateral
Layers: epithelium( non keratinized strat sq ep)
Stroma( contains blood vessels, goblet cells , lymph node)
Ciliary ganglion
Parasympathetic ganglion associated with nerve supply of eyeball
Orbit
It is 4 sided pyramidal in shape. A quadrilateral bony socket which contains eyeball and other structures.
Boundaries of orbit
Base: margin of orbit
Apex: optic foramen
Roof: ant: frontal bone
Posteriorly: lesser wing of Sphenoid
Floor: medial part: maxilla
Lateral part: zygomatic bone
Post part: horizontal part of palatine bone
Medial wall: frontal process of maxilla ,ethmoid bone ,lacrimal bone ,body of sphenoid
Lateral wall: ant part: zygomatic bone
Post part: greater wing of sphenoid
Bones involved: frontal , sphenoid, maxilla, zygomatic, palatine, lacrimal bone, ethmoid
Contents of orbit
Eyeball
Extra ocular muscles
Nerves (23456)
Lacrimal gland
Ciliary ganglion
Orbital fat
Vessels like central artery of retina, opthalmic and lacrimal vessels, supra and infra trochlear vessels, supra and infra orbital vessels
