ophthalmology residency program

1. VISUAL PATHWAY
Dr.mohammed muneer

2. CONTENT
SUMMARY
Overview of organization
of V.P.
Areas of C.C.
Visual reflexes
Orbital blood supply

3.  Vision begins with the formation of a focused image on the retina, The light patterns are absorbed by the
photoreceptor cells, which activate complex connections between the horizontal cells, the amacrine cells, and
the bipolar cells. The information converges on the final common pathway; the ganglion cells and their axons
that leave the eye.
 The retina converts patterns of light energy into electrical nerve signals that are conducted via the visual
pathway to the cerebral cortex for analysis.
 In the optic pathway,
The first -order neuron is the bipolar connected neuron in the retina,
the second-order neuron is the ganglion cell of the retina,
The third-order neuron is in the lateral geniculate body.
These neurons project to the calcarine visual cortex.
 Because the optic nerve, optic chiasma, and optic radiation are identical to white matter, they have no powers
of regeneration
SUMMARY

4. Over view of the Retinotopic Organization of
the Visual Pathway
1) Retina
2) Optic Nerve
3) Optic Chiasm
4) Optic Tract
5) Lateral Geniculate Body
6) Optic Radiation
7) Visual Cortex

5.  The visual fields are represented on the
retina in a direct point-to-point relationship
.
 Because of the physics of the optical
system of the eye,
the temporal field is projected on the
nasal retina
the nasal field is projected on the
temporal retina.
the superior field is projected on the
inferior retina
the inferior field is projected on the
superior retina
 The nerve fibers from the ganglion cells
converge toward the optic disc from all
parts of the retina.
the nasal half of the retina, the fibers are
arranged in a simple radial pattern.
the temporal half, the small fibers from
the macula forming the papillomacular
bundle pass directly to the disc, causing the
remaining temporal fibers to pass above and
below the macula on their way to the disc.
RETINA

8.  DISTAL optic nerve
 The small macular fibers have now moved
medially and have come to occupy the
center of the optic nerve
nasal retinal fibers remain medial
temporal fibers take up their lateral
position
Fibers that originate in the inferioir and
superior retina remain, respectively, inferior and
superior in the nerve.
 PROXIMAL optic nerve
 The fibers are arranged exactly as in the retina.
The most medial fibers are the nasal retinal
fibers,
lateral to them are the temporal fibers. The
macular fibers, which form about one-third of
the optic nerve fibers, are laterally placed in the
nerve.
OPTIC NERVE

10.  At the optic chiasma
the nasal retinal fibers, including those from the nasal half
of the macula, cross the midline and enter the contralateral
optic tract.
The temporal retinal fibers enter the ipsilateral tract
 the macular fibers and those from the perimacular region
occupy the greater part of the central region of the
chiasma.
OPTIC CHIASMA

11.  As the optic tract proceeds posteriorly, it undergoes a 90-degree
inward twist,
so that the fibers from the upper retinal quadrants pass to its medial
side
those from the lower retinal quadrants pass to its lateral side
It is in the optic tracts that nerve fibers from corresponding functional
parts of each retina become associated.
The nerve fibers from the superior nasal retina on one side become
associated with uncrossed superior temporal retinal fibers of the other
side,
the inferior nasal retinal fibers become related to uncrossed inferior
temporal retinal fibers.
OPTIC TRACT

13.  In the lateral geniculate body
the peripheral retinal fibers end in the anterior part,
the upper retinal quadrants ending medially,
the lower ones laterally.
The macular fibers end in the center and posterior part of the nucleus.
The temporal uncrossed retinal fibers synapse in layers 2, 3, and 5,
while the nasal crossed retinal fibers synapse in layers 1, 4, and 6.
It is thus seen that the uncrossed and crossed retinal fibers do not end by synapsing with neurons in the
same laminae. However, fibers from corresponding functional parts of the two retinal parts end in
neurons situated in neighboring parts of adjacent laminae.
LATERAL GENICULATE BODY

16.  Each retinal ganglion cell fiber, on entering its lamina in the lateral geniculate body, divides into five or six
terminal branches.
 Each branch then synapses with a single geniculate neuron in that lamina.
 One geniculate neuron may, however, synapse with more than one incoming retinal fiber.
 Multiple connector neurons have been shown to unite multiple genicular cells in a single lamina, and
others have been shown to unite cells in different laminae.
 A SINGLE GENICULATE NEURON DOES NOT RECEIVE AFFERENT RETINAL FIBERS FROM BOTH EYES.
However, the connector neurons might bring about connections between bilateral retinal afferents.
 The lateral geniculate body should not be regarded as a simple relay center. . The presence of the many
connector neurons suggests that the lateral geniculate body may have an INTEGRATIVE FUNCTION.

17.  The optic radiation is made up of nerve fibers that arise from nerve cells in the lateral and
medial portions ofthe lateral geniculate body .
The lateral fibers are the projection of the homonymous inferior retinal quadrants and
terminate on the inferior wall of the calcarine sulcus and the adjacent surface cortex of the
primary visual area.
The medial fibers are the projection of the homonymous superior retinal quadrants and
terminate on the superior wall of the calcarine sulcus and the adjacent surface cortex of the
primary visual area.
Optic Radiation and the Visual Cortex

19.  PRIMARY VISUAL AREA ( area 17 )
 occupies the walls of the deep calcarine sulcus on the medial surface of the hemisphere and extends
onto the cortex above and below the sulcus.
 It extends posteriorly as far as the occipital pole, and a small portion of the variable size extends onto the
posterolateral aspect of the pole.
 Anteriorly, the area extends forward above the calcarine sulcus as far as the parieto-occipital sulcus
 It can be recognized by
1- its thinness (1.5 mm)
2- the characteristic presence of a white line or stria (of Gennari) in the gray matter (hence the term striate
cortex )
The white line is formed in the fourth layer of the cortex by the presence of myelinated fibers from the optic
radiation and association fibers
Visual Cortex areas

20.  the primary visual cortex have six layers .
 The primary visual cortex receives afferent fibers from the lateral geniculate body via the optic radiation .
The cortex receives fibers from the temporal half of the ipsilateral retina and the nasal half of the
contralateral retina.
The right half of the field of vision, therefore, is represented in the visual cortex of the left cerebral
hemisphere, and vice versa.
 It is important to note that
1- the superior retinal quadrants (inferior field of vision) pass to the superior wall of the calcarine sulcus, 2-
2- while the inferior retinal quadrants (superior field of vision) pass to the inferior wall of the calcarine
sulcus.
3- The macula lutea, which is the central area of the retina and the area for most perfect vision, is
represented on the cortex in the posterior part of area 17 and accounts for one-third of the visual cortex.
4- The peripheral parts of the retina are represented more anteriorly.

24.  SECONDARY VISUAL AREA ( AREA 18 , 19 )
 surround the primary visual area on the medial and lateral surfaces of the hemisphere.
 These areas are nonstriate
 histologically show the usual six layers.
 The secondary association areas receive afferent fibers from the primary visual area (area 17) and other
cortical areas, as well as from the thalamus.
 THE FUNCTION
1- is to relate the visual information received by the primary visual area to past visual experiences, thus
enabling the individual to recognize and appreciate what he or she is seeing.
2- Area 18 also integrates the two halves of the visual fields by means of commissural fibers that cross
the midline in the splenium of the corpus callosum.
3- It is possible that area 18 is involved in sensory-motor eye coordination and is linked to the frontal eye
field.
4- Area 18 may also be linked by descending pathways to the cranial nerve nuclei controlling the
extraocular muscles and be involved with smooth pursuit of visual targets.

25. 1- OCCIPITAL EYE FIELD
 The occipital eye field is thought to exist in the secondary visual area in humans .
 Stimulation produces conjugate deviation of the eyes, especially to the opposite side.
 The function of the eye field is believed to be reflex and associated with smooth
of the eye when it is following an object (pursuit movement).
 The occipital eye fields of both hemispheres are connected through the corpus callosum by
nervous pathways, and are also thought to be connected to the superior colliculus .
Other Areas Of The Cerebral Cortex Associated With Sight

27. 2- FRONTAL EYE FIELD
 Extends forward from the facial area of the precentral gyrus into the middle frontal gyrus (parts
Brodmann's areas 6, 8, and 9).
 Stimulation of this region causes conjugate movements of the eyes, usually toward the opposite
side.
 The exact pathway taken by nerve fibers from this area is not known, but they are thought to
to the superior colliculus of the midbrain .
 The superior colliculus is connected to the nuclei of the extraocular muscles by the tectobulbar
tract and the reticular formation.
 the frontal eye field is considered to control voluntary saccades and is independent of visual
stimuli.

29.  This speech area is localized in the left dominant hemisphere , mainly in the superior temporal
gyrus, with extensions around the posterior end of the lateral sulcus into the parietal region .
 Wernicke's area is connected to Broca's area by a bundle of nerve fibers called the arcuate
fasciculus.
 It receives fibers from the visual cortex in the occipital lobe and the auditory cortex in the
superior temporal gyrus.
 Wernicke's area permits the understanding of written and spoken language and enables a
person to read a sentence, understand it, and say it out loud .
Sensory Speech Area of Wernicke

32.  Direct and consensual light reflex
 Consist of simultaneous constriction of both pupils in
response to light of one or the other eye
 The afferentr fibers coincide with that of the visual
pathway including a decussation of nasal fibers in the
chiasm,, at the post part of the optic tract ,, pupillary
fibers leave the visual fibers and pass to reach the
pretectal n. At the level of the sup colliculus
 Efferent fibers pass to the ( edinger westphal n ) ,,
decussating partially
 Preganglionic PSF leave each N. And run in the
oculumotor n as it leaves the brain stem ,, fibers lie
inferiorly and then in the inferior division of CN III as it
enters the orbit
 Fibers synapse in the ciliary ganglion and give rise to
postganglionic myelinated short ciiary nerves ,, 3-
of those are pupillomotor ,, the rest are designatec for
ciliary m and near reflex

33.  Accomaodation reflex
 Is synkinesis that occur when attension come from distance to near .
 Includes accomodation , pupil constriction and convergence
 Initiated in the occipital cortex ,, cortical fibers descend via the internal capsule
to the oculomotor nuclei in the midbrain.
The oculomotor nerve travels to the medial rectus muscles.
 Some of the descending cortical fibers synapse with the parasympathetic nuclei
(Edinger-Westphal nuclei) of the oculomotor nerve on both sides.
 Here the fibers synapse, and the parasympathetic preganglionic fibers travel
through the oculomotor nerve to the ciliary ganglion in the orbit. Finally,
postganglionic parasympathetic fibers pass through the short ciliary nerves to
the ciliary muscle and the constrictor pupillae muscle of the iris.

34.  Visual body reflex
 The following are types of visual body reflex:
1- automatic scanning movements of the eyes and head when reading
2- automatic movement of the eyes, head and neck toward the source of a visual stimulus
3- protective closing of eyes after a visual stimulus
4- protective raising of the arm after a visual stimulus
 All are mediated via the following pathways:
 afferent: retina - optic nerve - chiasm - optic tract - superior colliculus
 efferent:
 superior colliculus - tectospinal tract - anterior grey column of spinal cord - alpha-motor neurones
 superior colliculus - tectobulbar tract - cranial motor nuclei

36. OPHTHALMIC ARTERY
 is a branch of the internal carotid artery after it emerges from the cavernous sinus medial to the
anterior clinoid process .
 It passes forward through the optic canal below and lateral to the optic nerve.
 At its origin the ophthalmic artery lies within the subarachnoid space.
 within the optic canal it lies within the dural-arachnoid sheath ofthe optic nerve.
 On emerging from the canal the artery pierces the meningeal sheath and comes to lie
outside it.

37.  In the orbital cavity
1- the artery runs forward for a short distance
lateral to the optic nerve
medial to the lateral rectus muscle, the abducent and oculomotor nerves, and the ciliary ganglion.
2- The artery then turns medially and crosses above the optic nerve, accompanied by the nasociliary
nerve. Here it lies inferior to the superior rectus muscle.
3- On reaching the medial wall of the orbit, it runs forward with the nasociliary nerve above the medial
rectus muscle and below the superior oblique.
4- At the medial end of the upper eyelid the ophthalmic artery divides into the supratrochlear and
dorsal nasal arteries
 In 15 percent of people the artery crosses below the optic nerve rather than above it.

39. Branches of the opthalmic artery
1. Central retinal artery
2. Lacrimal artery
3. Muscular branches
4. Ciliary arteries
5. Supraorbital artery
6. Posterior ethmoidal artery
7. Anterior ethmoidal artery
8. Meningeal artery
9. Medial palpebral arteries
10. Supratrochlear arteries
11. Dorsal nasal artery

40. 1. Central retinal artery
 arises from the ophthalmic artery as it lies
inferolateral to the optic nerve close to the
optic canal.
 12 mm behind the eyeball it turns upward to
pierce the dura and arachnoid sheaths of the
optic nerve .
 It enters the back of the eyeball by piercing
the lamina cribrosa . The central artery now
divides into two equal superior and inferior
branches. After a few millimeters these
branches divide into superior, inferior, nasal,
and temporal branches. The four arteries now
supply a quadrant of the retina and are
distributed to its superficial layers.

41. Branches Of The Central Retinal Artery
1. Small meningeal branches supply the pial sheath of
the optic nerve as the central artery pierces the pia
mater.
Very small anastomoses occur between the pial
vessels and the small vessels in the sclera about the
nerve head (circle of Zinn).
It should be emphasized that these anastomoses
are extremely small, and for practical purposes the
central retinal artery should be considered an end artery.
2. Central collateral branches arising from the central
retinal artery as the artery enters the optic nerve. A
central collateral artery may pass with the central
retinal artery toward the lamina cribrosa.
A branch of a central collateral artery may pass
posteriorly within the optic nerve toward the optic canal
and supply the macular nerve fibers.

42. 2. Lacrimal Artery
 Arises from the ophthalmic artery close to its
emergence from the optic canal
 The lacrimal artery runs forward on the upper
border of the lateral rectus muscle accompanied
by the lacrimal nerve. It passes through the
lacrimal gland, which it supplies, and sends
terminal branches to the eyelids and conjunctiva.
 Branches of the lacrimal artery
1- lateral palpebral arteries
which pass medially into the upper and lower
eyelids and anastomose with the medial palpebral
arteries
2- the zygomatic branches,
which pass through the zygomatico- facial
and zygomaticotemporal foramina to anastomose
with arteries on the face and in the temporal fossa
3- muscular branch
to the lateral rectus muscle.
4- Recurrent meningeal branch
runs posteriorly through the lateral part of the
superior orbital fissure to anastomose with a
branch of the middle meningeal artery.

44. 4-Ciliary Arteries
 Three groups of ciliary arteries:
1- the long posterior c.a.
2- the short posterior c.a.
3- the anterior c.a.
 The long posterior ciliary arteries
 usually two in number
 arise from the ophthalmic artery as it crosses the optic nerve.
 They run forward with the optic nerve and pierce the sclera of
the eyeball medial and lateral to the nerve outside the circle
formed by the short posterior ciliary arteries.
 The long posterior ciliary arteries then run forward between
the sclera and the choroid to the ciliary body.
At the attached margin of the iris they divide into upper and
lower branches which encircle the iris and anastomose with
corresponding branches of the artery on the other side.
In addition, they anastomose with the anterior ciliary arteries
to form the major arterial circle of the iris.
Recurrent branches of the long posterior ciliary arteries and
branches from the major arterial circle and the anterior ciliary
arteries supply the choroid posteriorly as far as the equator of the
eyeball and anastomose with the short posterior ciliary arteries.

47. The Short Posterior Ciliary Arteries
 are about seven in number.
 They arise from the ophthalmic artery as it crosses
the optic nerve.
 After dividing into 10 to 20 branches, they run
forward around the optic nerve, mixed with the
short ciliary nerves.
 The arteries pierce the sclera around the entrance
of the optic nerve and supply the choroid as far
forward as the equator of the eyeball.
Here they anastomose with
1- The recurrent branches of the long posterior
ciliary arteries,
2- branches of the major arterial circle of the iris
3- branches of the anterior ciliary arteries.
 A number of small branches of the short posterior
ciliary arteries form an anastomotic ring (ring of
Zinn) around the optic disc.
Small branches from the ring anastomose with
blood vessels in the pia covering the optic nerve.
 In approximately 15 to 20 percent of people a
cilioretinal artery arises from the ciliary circulation.
It enters the retina at the lateral border of the optic
nerve and supplies an area of the retina between
the optic disc and the macula.
Its presence is of particular importance in cases of
central retinal artery occlusion

49. The Anterior Ciliary Arteries
 originate from the muscular branches of the ophthalmic artery to
the four rectus muscles .
 There are two anterior ciliary arteries associated with each rectus
muscle
with the exception of the lateral rectus muscle, which is provided
only one anterior ciliary artery.
 These arteries supply the sclera and the conjunctiva, and send
branches through the sclera at the insertion of the recti tendons.
These latter twigs join the long posterior ciliary arteries to form the
major arterial circle of the iris.

50. 5-Supraorbital Artery
 The supraorbital artery arises from the ophthalmic artery
as it crosses the optic nerve.
 It passes superiorly around the medial borders of the
superior rectus and levator palpebrae superioris muscles.
The artery then runs forward with the supraorbital
nerve between the LPS and the roof of the orbit.
It leaves the orbit by passing through the supraorbital
notch or foramen and ascends to the scalp deep to the
frontalis muscle.
Its terminal branches anastomose with branches of the
supratrochlear and superficial temporal arteries.
The supraorbital artery supplies
1- levator palpebrae superioris,
2- diploe of the frontal bone
3- frontal sinus,
4- the upper eyelid, and the skin of the forehead and the
scalp.

51. 6-Anterior Ethmoidal Artery
 Is larger than the posterior ethmoidal artery.
 Enters the anterior ethmoidal canal accompanied by
the anterior ethmoidal nerve.
 The artery then enters the anterior cranial fossa and
passes into the nose through the cribriform plate of the
ethmoid.
 It then descends in a groove on the deep surface ofthe
nasal bone to enter the face between the nasal bone
and the upper nasal cartilage.
 During this long course the artery supplies
1- the anterior and middle ethmoidal air cells
2- the frontal air sinus
3- the meninges
4- the mucous membrane of the anterior part of the
nasal cavity
5- the skin of the nose.
7-Posterior Ethmoidal Artery
 arises from the ophthalmic artery when the
latter reaches the medial wall of the orbit.
 It passes medially between the upper border of
the medial rectus muscle and the superior
oblique muscle to enter the posterior ethmoidal
canal.
 The artery supplies
1- the posterior ethmoidal air sinuses
2- the dura of the anterior cranial fossa
3- the upper part of the nasal mucosa.

53. 10-Supratrochlear Arteries
 A terminal branch ofthe ophthalmic artery
 Leaves the orbit by piercing the orbital septum
above the pulley for the superior oblique
muscle.
 It is accompanied by the supratrochlear nerve
 supplies the skin of the forehead and scalp.
11-Dorsal Nasal Artery
 A terminal branch ofthe ophthalmic artery.
 pierces the orbital septum. It passes above the
medial palpebral ligament and then descends
to the side ofthe nose.
 It gives off branches to the lacrimal sac and
anastomoses with the facial artery.

55. Infraorbital Artery
 Arises from the maxillary artery in the pterygopalatine
fossa.
 It enters the orbital cavity through the inferior orbital
fissure accompanied by the infraorbital nerve.
 Both the artery and the nerve pass forward in the
infraorbital groove and canal to emerge on the face
through the infraorbital foramen.
 Besides supplying the skin and tissues of the face, the
maxillary air sinus, and the teeth ofthe upper jaw
(anterior superior alveolar artery), the infraorbital artery
gives off orbital branches to the
1- Inferior rectus
2- Inferior oblique muscles
3- The lacrimal sac

56. Veins Of The Orbit
 The veins of the orbit are
1- Tortuous
2- Freely anastomose with one another
3- They have no valves.
 The orbit is drained by the superior and inferior
ophthalmic veins, which in turn drain directly into the
cavernous sinus.
 The central retinal vein usually drains directly into the
cavernous sinus or into the superior ophthalmic vein

57. Superior Ophthalmic Vein
 This is the larger of the two ophthalmic veins.
 The superior ophthalmic vein arises behind the medial part of the upper eyelid by the union of a
branch of the supraorbital vein and a branch from the facial vein.
 The branch from the supraorbital vein enters the orbit through the supraorbital notch, while the
branch from the facial vein pierces the orbital septum.
 The superior ophthalmic vein passes posteriorly in the orbital fat receiving tributaries that correspond
to most of the branches of the ophthalmic artery. It communicates with the central retinal vein and
near the apex of the orbit it commonly receives the inferior ophthalmic vein.
 The superior ophthalmic vein also receives the two vorticose veins (venae vorticosae) from the upper
part of the eyeball (the vorticose veins correspond to the posterior ciliary veins).
 The superior ophthalmic vein crosses the optic nerve with the ophthalmic artery. It leaves the orbit
through the upper part of the superior orbital fissure, above the lateral rectus muscle, to join the
cavernous sinus.

59. Inferior Ophthalmic Vein
 This vein arises from a venous plexus on the anterior
part of the floor of the orbital cavity.
 It communicates with the facial vein over the inferior
orbital margin and with the pterygoid venous plexus
through the inferior orbital fissure.
 It passes posteriorly in the orbital fat on the inferior
rectus muscle and receives muscular branches and the
two inferior vorticose veins from the lower part of the
eyeball.
 The inferior ophthalmic vein drains into the cavernous
sinus, or it may pass through the lower part of the
inferior orbital fissure and empty into the pterygoid
venous plexus.

60. Central Retinal Vein
 The central retinal vein is formed by the union of tributaries that correspond
approximately to the branches ofthe central retinal artery.
 The central vein leaves the eyeball by piercing the lamina cribrosa in
company with the artery.
 The vein now passes backward within the optic nerve. About 12 mm behind
the eyeball, the central vein leaves the nerve, crosses the extension of the
subarachnoid space around the nerve, and emerges from the dura-arachnoid
sheath behind the artery.
 The vein then drains directly into the cavenous sinus or enters the superior
ophthalmic vein.

62. Infraorbital Vein
 Arises on the face by the union of several tributaries. Accompanied
by the infraorbital artery and the infraorbital nerve
 It passes posteriorly through the infraorbital foramen, infraorbital
canal, and infraorbital groove.
 It receives tributaries from structures that lie close to the floor of the
orbit and communicates with the inferior ophthalmic vein.
 It drains through the inferior orbital fissure into the pterygoid
venous plexus.

63. SPECIAL THANKS FOR
YOUR ATTENTION