This document provides information on neuro-ophthalmology and the anatomy and pathways related to vision. Some key points: - The eyes are intimately related to the brain and can provide clues to central nervous system disorders. Cranial nerves III, IV, VI control extraocular muscles, while V and VII are also involved in ocular function. - The optic nerve has three portions - orbital, intraosseous, and intracranial. It is surrounded by three meningeal sheaths and carries both visual and pupillary fibers from the retina to the brain. - The visual pathway involves the optic nerve, optic chiasm, optic tract, lateral geniculate body, optic radiation, and

1. Neuro-
Ophthalmology

2. Neuro-Ophthalmology
• Eyes
– intimately related to the brain
• Give diagnostic clues to CNS disorders
• IC Disease - visual disturbance
 CN III, IV, VI – EOM
 CN V, VII – also associated with ocular
function

3. Anatomy of the Optic
Nerve
• Trunk consisting of about 1 million axons
arising from the ganglion cells of the
retina
 Ganglion Cells axons nerve
fiber layer of the retina OPTIC
NERVE

4. • Portions:
 Orbital Portion: 25-30 mm long within the
muscle cone
 Intraosseous Portion: 4-9 mm
 Intracranial Portion: 10 mm
 Diameter: 1.5 mm (within the sclera)
3 mm (within the orbit)
 80%: visual fibers
 20%: pupillary fibers
Anatomy of the Optic Nerve

5. Optic Nerve

6. Sheaths of the Optic Nerve
• PIA
– fibrous tissue with numerous small blood
vessel
– divides the nerve into bundles
– continues to the sclera
Continous with the meninges

7. • ARACHNOID
– from the IC end of optic foramen to sclera
– diaphanous connective tissue membrane
with many septate connections with PIA
Sheaths of the Optic Nerve
Continous with the meninges

8. • DURA
– splits into 2: periorbita (lining the orbital
cavity) and outer dural covering of the optic
nerve
– continous with outer 2/3 of sclera
Sheaths of the Optic Nerve
Continous with the meninges

9. • SPACES
–Subdural
–Subarachnoid
Sheaths of the Optic Nerve
Continous with the meninges

10. Sheaths of the Optic Nerve

11. Visual Pathway
• CN II – pathway for special sense of vision
– at the chiasm, more than half of the fibers
decussate; join uncrossed temporal fibers of
the opposite side optic tract
– all impulses from RVF projected to left
cerebrum and vice versa

12. Visual Pathway
• 80% of fibers to lateral geniculate body
and 20% to pretectal area and superior
colliculi
geniculocalcarine tract
optic radiation
occipital cortex

13. Visual Pathway
• Lesions:
– anterior to chiasm – unilateral VF defect
– posterior to chiasm – contralateral
homonymous defect
– chiasmal – bitemporal defect
– more congrous homonomous defect – farther
posterior lesion with macular sparing
(maintenance of good visual acuity)

14. Visual
Pathway

15. Lesions

16. Pupillary Pathways
A. Light Reflex
– Entirely subcortical
– Affrent pupillary fibers within the optic nerve go
to pretectal area of midbrain
Edinger-Westphal nucleus
– Efferent pathway is via CN III to the ciliary
ganglion within the muscle cone
short ciliary nerves sphincter muscle
of the iris

17. Pupillary Pathways
B. Near Reflex
– 3 Reactions:
• Accommodation
• Convergence
• Constriction of the pupil
– Final common pathway – CN III
– Marcus-Gunn Pupil
• Relative Afferent Pupillary Defect (RAPD)
–Swinging flashlight test

18. Pupillary
Pathways

19. • Normal pupillary diameter: 3-4 mm
– smaller in infancy
– larger in childhood
– progressively smaller with advancing age

20. • Physiologic Anisocoria
– seen in 20-40% of normal patients
– Difference in pupil size is about 0.5mm

21. • Argyll-Robertson Pupil
– Usually bilateral
– <3mm in diameter
– No response to light but responds to neural
stimulus
– Dilate poorly with mydriatics
– Suggestive of: CNS syphillis

22. Optic Neuritis
• Inflammation, degeneration, demyelinization of
optic nerve
• Retrobulbar Neuritis

23. Clinical Features:
• visual loss is subacute
• impaired color vision and
contrast sensitivity
• pain in the region of the
eye in 90% of cases
• 50% exacerbated by eye
movement
• sluggish pupillary-light
reflex
• central scotoma
• hyperemic optic disc w/
blurring of disc margin
• distension of large veins

24. Treatment
• Steroid therapy
• Methylprednisolone by IV, 1g/day for 3
days
OR
• Oral prednisolone, 1mg/kilo/day tapered
over 10-21 days

25. Optic Disc Edema
• Papilledema/Choked Disk
– non-inflammatory congestion of optic disk
associated with increased ICP (due to
cerebral tumors, abscesses, subdural
hematoma, hydrocephalous, malignant
hypertension)
– Mechanism: obstruction of venous flow
caused by pressure on the Central Retinal
Vein where it leaves the optic nerve

26. Clinical Findings
• enlarged blind spot
• normal VA and
normal VF
• Fundus Findings:
hyperemia of the disk,
blurring of the
margins, distention of
retinal veins, absence
of pulsation of CRV,
disk swelling to 6-10
D, hemorrhages

27. Papilledema
• Takes 24-48 hrs for early papilledema to
occur, 1 wk to develop fully
• Takes 6-8 wks to resolve following
adequate treatment

28. Papilledema
• Foster Kennedy’s syndrome
– papilledema on one side w/ optic atrophy on
the other eye

29. Papilledema
• Can be mimicked by buried drusen of the
optic nerve, small hyperopic disc,
myelinated nerve fibers

30. Course and Prognosis
• May or may not affect vision permanently
• Papilledema of more than 5D, extensive
retinal hemorrhages, macular stars – poor
prognosis

31. Multiple Sclerosis
• Demyelinating disorder of the CNS of
unknown cause, chronic, relapsing, onset
young adult
• Involves the optic nerve, chiasm, brain
stem, cerebellar peduncles, and spinal
cord
• Degeneration of myelin sheaths, glial
tissue overgrowth, and complete nerve
fiber destruction

32. MS in the Retinal Nerve Fiber Layer

33. MS
• Retrobulbar/Optic Neuritis
– blurring of vision, central scotoma, dilated
pupil
– diplopia due to EOM involvement from
internuclear ophthalmoplegia
– weakness of one rectus muscle/ptosis
– nystagmus may become permanent (70%)
– VER (visual evoked response) – abnormal in
80% of definite, 43% of probable, and 22% of
suspected cases of MS

34. Anterior Ischemic Optic Neuropathy
• characterized by pallid disc swelling with
acute loss of vision
• due to infarction of the optic nerve from
occlusion or decreased perfusion of the
short posterior ciliary arteries
• occurs in 6th
or 7th
decade of age
• associated with arteriosclerosis

35. Nutritional & Toxic Optic
Neuropathies
• Clinical Features:
– Subacute progressive symmetrical visual loss
w/ central visual field defects
– Poor color vision and temporal disc pallor

36. Nutritional & Toxic Optic
Neuropathies
• Causes:
– Vitamin B Complex deficiency
– Tobacco-Alcohol Amblyopia
– Heavy metal poisoning
– Chemical-induced optic neuropathy
• methanol poisoning (used in photocopier
machines)
– Drug-induced optic neuropathy
• ethambutol, quinine

37. Optic Nerve Trauma
• Indirect Optic Nerve Trauma:
– Optic nerve damage secondary to distant
skull injury
– Occurs in 1% of all head injuries
– Due to transmission of shock waves through
the orbital apex
– Optic nerve avulsion usually results from an
abrupt rotational injury to the globe

38. Optic Nerve Trauma
• Direct Optic Nerve Trauma
– Penetrating orbital trauma
– e.g. fractures involving the optic canal

39. Optic Chiasm
• Lesions of the chiasm cause bitemporal
hemianopsia
• Pituitary gland tumor

40. Internuclear Ophthalmoplegia
• Conjugate horizontal eye movements are
disrupted due to failure of coordination
between the abducens nerve nucleus in
the pons and the oculomotor nucleus in
the midbrain
• Results in slowing of saccades in the
adducting eye producing transient diplopia
on lateral gaze

41. Internuclear Ophthalmoplegia
• Causes
– Multiple sclerosis in young adults
– Brain stem infarction in older patients
– Tumors at arteriovenous malformations
– Encephalitis

42. Syndromes Affecting CN III, IV, VI
• Superior Orbital Fissure Syndrome
– All extraocular peripheral nerves pass through
the superior orbital fissure and can be
involved by trauma or by tumor encroaching
on the fissure

43. Syndromes Affecting CN III, IV, VI
• Orbital Apex Syndrome
• Similar to the superior orbital fissure
syndrome with the addition of optic nerve
signs and greater proptosis and less pain
• Caused by orbital tumor, inflammation,
trauma that damages the optic and
extraocular nerves

44. Syndromes Affecting CN III, IV, VI
• Complete Ophthalmoplegia (Sudden)
– Can be due to brainstem vascular disease,
pituitary apoplexy, myasthenia gravis,
arteriosclerotic basilar aneurysm

45. Myasthenia Gravis
• Abnormal fatigability of striated muscles
after repetitive contraction
• Improves after rest
• Often is first manifested by weakness of
the extraocular muscles
• Diplopia is often an early symptom

46. Chronic Progressive External
Ophthalmoplegia
• Slowly progressive inability to move the
eyes
• Severe early ptosis
• Normal pupillary reactions and
accommodation
• A form of mitochondrial myopathy

47. Color VisionColor Vision

48. Electromagnetic SpectrumElectromagnetic Spectrum
• Photons are classified according to their
wavelength
• Longest wavelength: radio and television
waves
• Shortest wavelength: gamma rays
• Middle of the spectrum: visible light

49. Rods and ConesRods and Cones
• Retinal photoreceptors that contain
pigments that preferentially absorb
photons with wavelengths 400-700 nm
• Shortest wavelength: blue and green
• Longer wavelengths: yellow, orange, red

50. Visual PigmentsVisual Pigments
• Four visual pigments:
– Rhodopsin: present in rods
– 3 cone pigments
• Erythrolabe (R cones): red, 570 nm
• Cyanolabe (B cones): blue, 440 nm
• Chlorolabe (G cones): green, 540 nm

51. 3 Attributes of Color3 Attributes of Color
• Hue
– “color”
– Attribute of color perception denoted by blue,
red, purple, etc
– Depends largely on what the eye and brain
perceive to be the predominant wavelength
present in the incoming light

52. 3 Attributes of Color3 Attributes of Color
• Saturation
– “chroma”
– purity or richness of a color
– When all the light seen by the eye is the same
wavelength, the color is fully saturated
– e.g. pink is a desaturated red

53. 3 Attributes of Color3 Attributes of Color
• Brightness
– Luminance, value
– Quantity of light coming from an object (the
number of photons striking the eye)

54. Primary ColorsPrimary Colors
• Red
• Green
• Blue

55. Relative Luminosity CurvesRelative Luminosity Curves
• Illustrate the eye’s sensitivity to different
wavelengths of light
• Cones’ peak sensitivity: 555 nm
• Rods’ peak sensitivity: 505 nm (blue)

56. TrichromatsTrichromats
• 92% of the population who have “normal”
color vision
• Have all 3 different kinds of cones, normal
concentration of cone pigments, normal
retinal wiring

57. Congenital DichromatismCongenital Dichromatism
• Cones themselves are normal, but one of
the 3 contains the wrong pigment
• Deutranopes:
– Lack green pigment
• Protanopes
– Lack red pigment
• Tritanopes
– Lack blue pigment

58. Congenital DichromatismCongenital Dichromatism
• Mode of inheritance: sex-linked recessive
– Men almost exclusively manifest the disorder
– Women are carriers

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