Download MBBS Ophthalmology PPT 37 Ocular Anatomy Lecture Notes

Download MBBS (Bachelor of Medicine, Bachelor of Surgery) Ophthalmology PPT 37 Ocular Anatomy Lecture Notes

Ocular Anatomy

Department of Ophthalmology


? Photographs included in the presentation are courtesy of
Dr.Jonathan.J.Dutton and Dr.Thomas.G.Waldrop
(Atlas of Clinical and Surgical Orbital Anatomy)

Learning Objectives

At the end of this class students shall be able to
? Identify various structures of the eye
? Have a basic understanding of the structure and functions of various

parts of the eye

? Orbit
Lodges the eyeball
? Eye lids ?
? Cover and protect
? Lacrimal system-
Secretes and drain tears
? Extraocular muscles-
for ocular movements
? Layers of eyeball-
perform various functions

Bony Orbit

? Made by 7


? Frontal
? Zygomatic
? Maxillary
? Ethmoidal
? Sphenoid
? Lacrimal
? Palatine

Frontal view of bony orbit

Outer eye: Eyelids

The eyelids fulfill two main


? protection of the eyeball

? secretion, distribution and

drainage of tears

The eyelid muscles
Lid structure and movement

The levator muscle extends from

an attachment at the orbital apex

to attachments at the tarsal

plate and skin.

The lids are securely attached at

either end to the bony orbital

margin by medial and lateral

palpebral ligaments.


- Sensory innervation is from the trigeminal (fifth) cranial nerve, via
the ophthalmic division (upper lid) and maxillary division (lower lid).

- The orbicularis oculi is innervated by the facial (seventh) nerve.

- The levator muscle in the upper lid is supplied by the oculomotor
(third) nerve.
Blood supply

Network of blood vessels which form an anastomosis
between branches derived from the external carotid artery
via the face and from the internal carotid artery via the orbit.


? Lymphatic fluid drains into the preauricular and submandibular nodes.

? Preauricular lymphadenopathy is a useful sign of infective eyelid

swelling (especially viral).

Lacrimal system

? Lacrimal gland

? Lacrimal passage
? Lacrimal puncta
? Lacrimal canaliculi
? Lacrimal sac
? Naso-lacrimal duct

Tear production

? The lacrimal gland secretes

most of the aqueous

component of the tear film

? Location: superotemporal

part of the anterior orbit

? Innervation :

parasympathetic fibres

carried by the facial nerve.

Lacrimal Apparatus/Drainage system

Extraocular muscles

? 4 Recti
? 2 Obliques
Medial rectus (MR)
Inferior Rectus (IR)
Superior rectus (SR)
Inferior oblique (IO)
Superior Oblique(SO)
Lateral Rectus (LR)

Extra-ocular muscles

? Action results in eye movements

? Medial Rectus --- Adduction

? Inferior Rectus ---


? Superior Rectus ---

Elevation , Intorsion, Adduction

? Inferior Oblique---

Extorsion, Elevation, Abduction

? Superior Oblique---

Intorsion, Depression,Abduction

? Lateral Rectus --- Abduction

Nerve supply of Extra Ocular Muscles

? Three Cranial Nerves supply the Extra Ocular Muscles

? CN 3rd-Oculomotor-MR, IR, SR, IO
? CN 4th-Trochlear--SO
? CN 6th- Abducens--- LR

Overview of ocular anatomy


? The conjunctiva is a mucous

membrane lining the eyelids.

Covers the anterior eyeball

up to the edge of the cornea.

? At the upper and lower

reflections between eyeball

and eyelid, conjunctiva forms

two sacs, the superior and

inferior fornices .

Cornea and sclera

The cornea and sclera form a

spherical shell which makes up

outer wall of eyeball.
Cornea and sclera
? The sclera is :
- principally collagenous,
- avascular (apart from some vessels on its surface)
- relatively acellular.
It is perforated posteriorly by the optic nerve, and by sensory and
motor nerves and blood vessels to the eyeball.

The cornea and sclera merge at the corneal edge (the limbus).


? Juncture between the cornea and the sclera

? Nourishes peripheral cornea

? Assists in corneal wound healing

? Pathway for aqueous outflow (contains trabecular meshwork and
canal of schlemm)
Corneoscleral limbus
? Transition zone:

? anteriorbowman`s terminal-Descemet's terminal
? posteriorscleral spuriris root
? 1.52.0mm width

? Appearance

? Semitransparant zone
? White sclera

? Angle of AC

The chief functions of the cornea

? Protection against invasion of microorganisms into the eye

? Transmission and focusing (refraction) of light.

? Made up of 5 layers

? Specialized Transparent Tissue

? No blood vessels

? Primarily responsible for refracting light (43-44 diopters)

? More nerve endings than anywhere else in the body

? Protection to the eye

? The only part of the eye that is transplanted from one person to



? Epithelium
? Bowman membrane
? Stroma
? Descemet


(posterior limiting

layer of cornea)

? Endothelium
Cornea- 5 layered


? Oval

? transverse11.512mm
? vertical10.511mm

? curvatureanterior 7.8mm


? thicknesscentre0.50.55mm


? Refractive index1.377


2.Bowman's membrane :

? 50m

? 12

? 5


6 layers

? Squamous cell

? No cell

? Basal cell

? Collagen matrix

? Renewing cycle7 days

? Scar



4. Descemet's membrane

? 500 m

? 1012 m

? 23 corneal cells

? No structure

? 1matrixGAGs)

? elasticity

? Fibrous lamina

? 200

? Secreted by endothelial cells

250 layers

? Parallel to surface

? Basal membrane of

endothelial cell

? Parallel collagen fibers
? Ordered arrangement

? Regeneration

? Scar


? 5 m
? Monolayer hexagon

? 500 000 cells
? Tight junctions
? Pump


? The uvea comprises the
? iris and ciliary body anteriorly
? choroid posteriorly


? Consists of connective tissue

containing muscle fibres, blood

vessels and pigment cells.

Its posterior surface is lined by a

layer of pigment cells.

At its centre is an aperture, the pupil.

The main function of pupil:

Control light entry to the retina and

to reduce intraocular light scatter.

Ciliary body

? The ciliary body is a specialised structure uniting the iris with the


? Secretes aqueous humour
? Anchors the lens via the zonules, through which it modulates lens
? The posterior part of the ciliary body merges into the retina at the ora



? The choroid, consisting of blood vessels, connective tissue and

pigment cells, is sandwiched between the retina and the sclera.

? It provides oxygen and nutrition to the outer retinal layers.


? The discus-like lens comprises

a mass of long cells known as

fibres. Has a hard nucleus

surrounded by less dense

fibres, the cortex.

? Relatively dehydrated

? Transparent.

Aqueous humour

? Fills the anterior and posterior chambers.

? The anterior chamber is the space between the cornea and the iris.

? Behind the iris and in front of the lens is the posterior chamber.

They are connected by the pupil.


? The ciliary body forms

aqueous humour

? By ultrafiltration and

active secretion.


Aqueous circulates from the

posterior to the anterior chamber

through the pupil.

Passes through the trabecular

meshwork (a specialised tissue in

the anterior chamber angle

between the iris and the cornea).

From here aqueous drains into
Schlemm's canal.


? A thick, transparent gel like substance that fills the center of

eyeball, giving it form and shape

? The vitreous body is 99% water but, vitally, also contains collagen

fibrils and hyaluronan, which impart cohesion and a gel-like


? The vitreous is adherent to the retina at certain points,

particularly at the optic disc and at the ora serrata.


Volume - 4.5ml


RI:1.3360aqueous humor


? Innermost layer of the eye.

? Converts light energyelectrical energy --->brain via the optic nerve

? Composed of 10 layers.

? Contains Photoreceptors

? Cones-near Center (seeing detail and color)

? Rods- in Periphery (seeing in low light and movement)



Transparent ,thin


Anterior rimora serrata


3 parts:-


Peripheral Retina




Optic disc


? Optic disc

? Only optic nerve fibers
? Physiological blind spot

? Macula

? Thinnest
? Point of sharpest vision is

in the fovea located in

the center of the macula

Histology of retina


2 Layers of Rods & Cones

3 External Limiting Membrane

4 Outer Nuclear layer

5 Outer Plexiform layer

6 Inner Nuclear layer

7 Inner Plexiform Layer

8 Ganglion Cell layer

9 Nerve Fibre layer

10 Internal limiting membrane

? The blood supply of the retina is derived from the central retinal
artery and vein, and from the choroid.

? The retinal vessels enter and leave the eye through the optic nerve
and run in the nerve fibre layer.
A major arterial and venous branch, forming an 'arcade', supplies
each of the retinal quadrants .

Optic nerve

? The ganglion cell axons in the retinal nerve fibre layer make a right-
angled turn into the optic nerve at the optic disc, which has no
photoreceptors and corresponds to the physiological blind spot.
? Behind the eyeball these axons become myelinated.
? Here the optic nerve is surrounded by cerebrospinal fluid in an
anterior extension of the subarachnoid space and is protected by the
same membranous layers as the brain.

Optic Nerve Pathways/Visual Cortex

? Message is carried down the optic

nerve through pathways to

occipital cortex; here vision

becomes sight

? At the optic chiasm, the nasal

nerve fibers cross; temporal nerve

fibers go straight back to cortex;

this arrangement impacts on

visual fields

? Results in visual field losses can be

predicted based on where

damage is located on the optic


? The human eye is lodged inside bony orbit and protected by


? It has an outer protective scleral coat modified anteriorly to

form cornea

? The middle layer or uvea consists of the ciliary body and iris

anteriorly and choroid posteriorly

? The innermost layer is retina containing photoreceptors

which lines the posterior two-thirds of choroid.

? The optic nerve carries visual information to the visual cortex.

This post was last modified on 07 April 2022