Anatomy Physiology Visual System April 2013

Anatomy & physiologyVisual system

Maria Larasati, Ophthalmologist

Monday, April 29, 13

Learning Objectives

By the end of this presentation you will be able to:

1. Recognize major components of the eye

2. Have a basic understanding of how the eye works

3. Understand how eye disease affects the components of the eye


EMBRYOLOGY OF THE EYE

This highly specialized sensory organ is derived from neural ectoderm, mesoderm and surface ectoderm.

The eye is essentially an outgrowth from the brain (neural ectoderm).

Started as Optic vesicle connected to the forebrain by Optic stalk.


EMBRYOLOGY (cont.)Invagination of both the optic vesicle to form Optic cup and the optic stalk to form Choroidal fissure inferiorly.

Surface ectoderm invaginate to form the lens vesicle.

Mesodermal tissues invade the developing eye to share in vascular, muscular and supportive tissues of the eye.


DEVELOPMENT OF THE EYE AFTER BIRTH

At birth, the eye is relatively large in relation to the rest of the body.

The eye reaches full size by the age of 8 years.

The lens continues to enlarge throughout the life.

The iris has a bluish color due to little or no pigment on the anterior surface.

During early infant life, the cornea & sclera can be stretched by raised IOP → enlargement of the eye.


Figure by Snell & LempMonday, April 29, 13

Lacrimal Apparatus

Tear secretion.

Layers of precorneal tear film.

Drainage of tear.


Quiz #1


Quiz #1

Cornea


Quiz #1

Cornea

Lens


Quiz #1

Cornea

LensIris


Quiz #1

Cornea

LensIris Sclera


Quiz #1

Cornea

LensIris Sclera

Macula


Quiz #1

Cornea

LensIris Sclera

Macula

Papil


Quiz #1

Cornea

LensIris Sclera

Macula

Papil

Retinal Artery


Quiz #1

Cornea

LensIris Sclera

Macula

Papil

Retinal Artery

Vortex Vein


Pop Quiz #2a

b

c

d

e


Pop Quiz #2

a: Lens

a

b

c

d

e


Pop Quiz #2

a: Lens

b: Ciliary Body (Pars plicata)

a

b

c

d

e


Pop Quiz #2

a: Lens


c: Pars Plana of ciliary body

a

b

c

d

e


Pop Quiz #2

a: Lens



d: Retina

a

b

c

d

e


Pop Quiz #2

a: Lens



d: Retina

e: Zonule or suspensory ligament

a

b

c

d

e


UVEAuveal layer is shown in red

It consists of the iris, ciliary body and choroidMonday, April 29, 13

Extrinsic Eye Musculature

For moving eye within its socket

6 muscles per eyeball

Innervated by 3 cranial nerves


Eye MovementsYaw

gaze shifts L/R

Pitch

gaze shifts up/down

Roll

eye rotates around line of gaze (torsion)

In each position of gaze, one muscle of each eye is the primary mover of that eye, and is “yoked” to the primary mover of the

other eye


Eye MovementsYaw

gaze shifts L/R

Pitch

gaze shifts up/down

Roll


YAW


other eye


Eye MovementsYaw

gaze shifts L/R

Pitch

gaze shifts up/down

Roll


PITCH

YAW


other eye


Eye MovementsYaw

gaze shifts L/R

Pitch

gaze shifts up/down

Roll


PITCH

YAW

ROLL


other eye


Oculomotor Muscle Actions

Muscle Action Nerve Supply

Sup. rectus elevates & abducts eyeballupper division of oculomotor n. (III)

Sup. oblique depresses & abducts eyeball trochlear n. (IV)

Med. rectus adducts the eyeballlower division of oculomotor n. (III)

Lat. rectus abducts the eyeball abducens n. (VI)

Inf. rectus depresses & abducts eyeballlower division of oculomotor n. (III)

Inf. oblique elevates & abducts eyeballlower division of oculomotor n. III)

levator palpebrae superioris raises the eyelid

upper division of oculomotor n. (III)


Intrinsic Eye Muscles and their response to light


Neuronal function


Looking at the RetinaMacula- 3 by 5 mm area at the posterior pole of the eye

Fovea- in center of macula : free of blood vessels, contains only cone cells


Ana

tom

y of

Rod

s an

d C

ones

Cones7 million

Color sensitiveFound mostly in fovea

Rods120 million

Light sensitiveFound in peripheral


Histology of the Retina


Physiology of Rods and Photopigments


Photomicroscopic view of the Histology of the Eye

SSclera

C Choroid coat

PEPigmented epithelium

POuter segments of rods and cones

ONuclei of rods and cones

OPLOuter synaptic layer

INuclei of bipolar neurons

PLInner synaptic layer

GGanglion cell layer


Photomicroscopic view of the Histology of the Eyeshowing the location of the central fovea


Visual Pathway

1. Cones

2. Bipolar neurons

3. Ganglion cell’s axon forms the optic nerve

4. Optic nerve to the Optic Chiasm

5. Optic tract

6. Lateral geniculate nuclei of the thalamus

7. Optic Radiations

8. Primary visual areas of the occipital lobes


Binocular vision


Visual Pathway


Optics of the Eye

The eye is like a cameraLight must have a clearly pathway to be clearly focused on the

sensory receptors of the retina, i.e., clear cornea, anterior chamber, lens and vitreous cavity

The refractive power of the eye is about ± 58 dioptres


Optics of the Eye (cont.)

The cornea is the major refracting element of the eye

a power of approximately 40 dioptres

If the curvature is greater in one meridian than the other→ Astigmatism

The refractive power of the lens is about 17 dioptres at rest

Accommodation able to change the power of the lens markedly depends on age


1. Myopic nearsighted2. Hypermetropic Farsighted3. Presbyopia age-related failure of

lens to accommodate4. Astigmatism Distorted vision due to

irregular-shaped lens or cornea

Abnormalities of The Eye


1. Ciliary muscles contract

2. Ciliary body pulls forward and inward

3. Tension on suspensory ligaments of lens is decreased

4. Lens becomes thicker (rounder) due to its elasticity

5. Pupils constricts

1. Ciliary muscles relaxes

2. Ciliary body returns to its resting state, backward and outward

3. Tension on suspensory ligaments of lens is increased

4. Lens becomes thinner (flatter) due to its elasticity

5. Pupils dilate

Accommodation of the LensNear Vision Far Vision


Thank you


Anatomy Physiology Visual System April 2013

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