anatomy physiology visual system april 2013
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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
Monday, April 29, 13
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.
Monday, April 29, 13
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.
Monday, April 29, 13
Monday, April 29, 13
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.
Monday, April 29, 13
Monday, April 29, 13
Figure by Snell & LempMonday, April 29, 13
Monday, April 29, 13
Monday, April 29, 13
Lacrimal Apparatus
Tear secretion.
Layers of precorneal tear film.
Drainage of tear.
Monday, April 29, 13
Lacrimal Apparatus
Tear secretion.
Layers of precorneal tear film.
Drainage of tear.
Monday, April 29, 13
Lacrimal Apparatus
Tear secretion.
Layers of precorneal tear film.
Drainage of tear.
Monday, April 29, 13
Lacrimal Apparatus
Tear secretion.
Layers of precorneal tear film.
Drainage of tear.
Monday, April 29, 13
Quiz #1
Monday, April 29, 13
Quiz #1
Cornea
Monday, April 29, 13
Quiz #1
Cornea
Lens
Monday, April 29, 13
Quiz #1
Cornea
LensIris
Monday, April 29, 13
Quiz #1
Cornea
LensIris Sclera
Monday, April 29, 13
Quiz #1
Cornea
LensIris Sclera
Macula
Monday, April 29, 13
Quiz #1
Cornea
LensIris Sclera
Macula
Papil
Monday, April 29, 13
Quiz #1
Cornea
LensIris Sclera
Macula
Papil
Retinal Artery
Monday, April 29, 13
Quiz #1
Cornea
LensIris Sclera
Macula
Papil
Retinal Artery
Vortex Vein
Monday, April 29, 13
Pop Quiz #2a
b
c
d
e
Monday, April 29, 13
Pop Quiz #2
a: Lens
a
b
c
d
e
Monday, April 29, 13
Pop Quiz #2
a: Lens
b: Ciliary Body (Pars plicata)
a
b
c
d
e
Monday, April 29, 13
Pop Quiz #2
a: Lens
b: Ciliary Body (Pars plicata)
c: Pars Plana of ciliary body
a
b
c
d
e
Monday, April 29, 13
Pop Quiz #2
a: Lens
b: Ciliary Body (Pars plicata)
c: Pars Plana of ciliary body
d: Retina
a
b
c
d
e
Monday, April 29, 13
Pop Quiz #2
a: Lens
b: Ciliary Body (Pars plicata)
c: Pars Plana of ciliary body
d: Retina
e: Zonule or suspensory ligament
a
b
c
d
e
Monday, April 29, 13
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
Monday, April 29, 13
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
Monday, April 29, 13
Eye MovementsYaw
gaze shifts L/R
Pitch
gaze shifts up/down
Roll
eye rotates around line of gaze (torsion)
YAW
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
Monday, April 29, 13
Eye MovementsYaw
gaze shifts L/R
Pitch
gaze shifts up/down
Roll
eye rotates around line of gaze (torsion)
PITCH
YAW
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
Monday, April 29, 13
Eye MovementsYaw
gaze shifts L/R
Pitch
gaze shifts up/down
Roll
eye rotates around line of gaze (torsion)
PITCH
YAW
ROLL
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
Monday, April 29, 13
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)
Monday, April 29, 13
Intrinsic Eye Muscles and their response to light
Monday, April 29, 13
Neuronal function
Monday, April 29, 13
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
Monday, April 29, 13
Ana
tom
y of
Rod
s an
d C
ones
Cones7 million
Color sensitiveFound mostly in fovea
Rods120 million
Light sensitiveFound in peripheral
Monday, April 29, 13
Histology of the Retina
Monday, April 29, 13
Physiology of Rods and Photopigments
Monday, April 29, 13
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
Monday, April 29, 13
Photomicroscopic view of the Histology of the Eyeshowing the location of the central fovea
Monday, April 29, 13
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
Monday, April 29, 13
Binocular vision
Monday, April 29, 13
Visual Pathway
Monday, April 29, 13
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
Monday, April 29, 13
Monday, April 29, 13
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
Monday, April 29, 13
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
Monday, April 29, 13
Monday, April 29, 13
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
Monday, April 29, 13
Thank you
Monday, April 29, 13
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