1. Neuro-ophthalmic Disorders

2. Relative Afferent Pupillary Defect
seen in optic nerve lesion and severe retinal disease 
lesion of the optic nerve on one side blocks the afferent limb of the pupillary light reflex
pupils are equal and of normal size but the pupillary response to light directed to the affected side is reduced
sign observed during the swinging-flashlight test 
seen as both pupils dilation when light is swung from normal to abnormal eye
the affected side will constrict less therefore appearing to dilate

3. Visual Pathway
The optic nerve is formed by the axons arising from the retinal ganglion cell layer.
It passes out of the eye though the lamina cribrosa of the sclera.
It is surrounded by dura, arachnoid and pia mater, continuous with that surrounding the brain. 
The optic nerves extend from the posterior pole of the eye to cross at the optic chiasm. 
The fibers travel as the optic tract - most of them go to the lateral geniculate body in the thalamus (visual)

4. Another population sends information to the tectum in midbrain (afferent fibers of the pupillary light reflex) 
They leave the lateral geniculate body forming the optic radiations to the visual cortex. 
Primary visual cortex responsible for processing visual information is located in the occipital lobe. 

6. Optic Nerve
Intraocular
Orbital
Intracanalicular
Intracranial

7. Intraocular portion of the Optic Nerve
Visible on the ophthalmoscopy as the optic disc. 
Central retinal vessels enter and leave the eye here.
There is a complete absence of photoreceptors and is known as the blind spot. 
Normally slightly vertically oval with an average area dimensions of 1.76mm horizontally and and 1.92mm vertically. 
Normal color is yellowish-orange.
Sharply defined margin and the nasal side is slightly less distinct due to the greater density of nerve fibers.  
There is a central depression called optic cup.

8. Optic cup is the pale center of the disc and is devoid of neuroretinal tissue.
It is important to document the size of the cup. 
This is specified as the horizontal and vertical cup to disc ratio.
Normal cup to disc ratio is 0.3 mm.  
Increased cup to disc ratio indicates a decrease in the quantity of healthy neuroretinal tissue and hence, glaucomatous change. 

9. Disturbances of the Visual Pathway

10. Optic Nerve

11. Swollen Optic Disc Papilloedema
Space-occupying lesions of the optic nerve head
Optic disc drusen (calcified axonal material)
Gliomas
Sarcoidosis
Leukemia
Papillitis
Accelerated (malignant hypertension)
Ischemic optic neuropathy
Central retinal vein occlusion
Pseudopapilloedema
Myelinated nerve fibers around the nerve head
Peripapillary atrophy in myopia

12. Optic disc drusen

13. Myelinated nerve fibers around the nerve head

14. Peripapillary atrophy in myopia

15. Papilloedema due to raised ICP
Optic nerve sheath is continuous with the subarachnoid space of the brain. 
As the CSF pressure increases, the pressure is transmitted to the optic nerve.
The sheath acts as a tourniquet and leads to a buildup of material at the level of lamina cribrosa. 
This results in characteristic swelling of the nerve head. 
 Papilloedema may be absent in cases of prior optic atrophy most likely secondary to a decrease in the number of physiologically active nerve fibers. 

17. Causes Idiopathic intracranial hypertension Intracranial tumors (60%)
Craniosynostosis
Cerebral edema
Encephalitis
Obstruction of the ventricular system
Decreased CSF resorption
Increased CSF production
Medications - tetracycline, nalidixic acid, steroids

18. History Associated visual loss is rare Transient visual obscurations
Blurred vision
Constriction of the visual field
Decreased color perception
Diplopia (sixth nerve palsy)
Headache, worse on waking and made worse by coughing
Nausea, retching, vomiting
Pulsatile tinnitus
History of trauma
Medications

19. Signs Swollen optic disc with blurry margins
Dilated and prominent superficial capillaries
No spontaneous venous pulsation of the CRV
Hemorrhages over and/or adjacent to the disc
Paton's lines 
Normal color vision
No RAPD
Visual field testing
large blind spot
constricted filed in chronic cases
Abnormal neurological signs

21. Investigations
CT scan and MRI of the brain with contrast to identify space occupying lesions
MR venography to detect venous sinus thrombosis
B-scan ultrasonography to rule out disc drusen
Fluorescein angiography 
Lumbar puncture 

22. Treatment Treat the underlying disorder
Papilloedema will resolve within few weeks once ICP has been normalized
Optic atrophy usually remains
Neurosurgery is required for space-occupying lesions and hydrocephalus

23. Idiopathic Intracranial Hypertension
Elevated ICP and presence of disc swelling with no evidence of intracranial abnormality and no dilation of the ventricles on the scan
Overweight women in the second and third decades
Exposure to drugs such as contraceptive pills and tetracyclines
Headache, obscurations of vision, sixth nerve palsies
No other neurological problems
Progressive contraction of the visual field if the nerve remains swollen for weeks

24. Treatment by reducing the ICP
medications (oral acetazolamide)
ventriculoperitoneal shunting
optic nerve decompression

25. Optic Neuritis Inflammation or demyelination of the optic nerve
Papillitis - optic nerve head is affected
Retrobulbar neuritis - nerve is affected more posteriorly with no disc swelling
Many are associated with multiple sclerosis 
Age , more in females and Caucasian

26. Causes Multiple sclerosis (50%) Syphilis Lyme disease Herpes zoster
Autoimmune disorders (lupus)
IBD
Drugs (chloramphenicol, ethambutol)
Vasculitis
Diabetes

27. History Usually affects one eye
Acute loss of vision that progress over a few days and then slowly improve (some are permanent)
Varies from a small area of blurring to complete blindness
Distorted vision and reduced color vision 
Pain on eye movement in retrobulbar neuritis
Preceding history of viral illness
40-70% develop other neurological symptoms to suggest MS

28. Examination Reduced visual acuity Reduced color vision
RAPD due to reduced optic nerve conduction
Central scotoma on field testing
Normal disc in RN, swollen disc in papillitis

29. Papillitis

30. MRI scan can identify additional silent plaques of demyelination
Diagnosis of MS is essentially clinical
Treatment with steroid may speed up visual recovery
Immunosuppressive therapy in case of MS
Vision slowly recovers over several weeks but not quite as good as before the attack
Repeated episodes may lead to optic atrophy and decline in vision
Vision may not recover in atypical cases

31. Ischemic Optic Neuropathy
Degenerative vaso-occlusive or vasculitic 
disease of the arterioles
Compromise posterior ciliary vessels
Ischemia of the anterior optic nerve

32. Types Arteritic ischemic optic neuropathy giant cell arteritis
advanced age
mostly involving nearly complete vision loss
 Non-arteritic ischemic optic neuropathy
results from the coincidence of cardiovascular risk factors in a patient with "crowded" optic discs
more common
younger age group
few near total loss of vision cases

33. Symptoms Sudden loss of vision or visual field, often on waking
Vision in that eye is obscured by a dark shadow, often involving just the upper or lower half of vision, usually the area towards the nose 
Pain or scalp tenderness (giant cell arteritis) 

34. Giant Cell Arteritis
Autoimmune vasculitis in patients over the age of 60
Affects arteries with an internal elastic lamina
Present with any combination of:
sudden loss of vision
scalp tenderness (e.g. on combing)
pain on chewing (jaw claudication)
shoulder pain
malaise

35. Signs Reduction in visual acuity
Field defect, absence of the lower or upper half of the visual field (altitudinal scotoma)
Swollen and hemorrhagic disc, normal retina and retinal vessels
Pale disc in arteritic ION
Small normal disc with small cup in non-arteritic ION
Tender temporal artey in GCA

37. Investigations Elevated ESR and CRP in GCA (1 in 10 normal)
Temporal artery biopsy
Color duplex ultrasound -  hypoechoic halo around the temporal artery lumen 
Full blood count to exclude anemia
Blood pressure
Blood sugar

38. Treatment IV and oral high-dose steroids if GCA is suspected
Dose is tapered over the ensuing weeks according to symptoms and the response of ESR and CRP
Steroids will not reverse the visual loss but can prevent the involvement of the other eye
No treatment for non-arteritic ION other than management of underlying conditions

39. Prognosis Second eye may rapidly become involved if untreated (GCA)
Steroid therapy may have to be continued on a prolonged basis and monitored
Significant rate of involvement of the second eye in non-arteritic form ( %) 
Unusual for the vision to get progressively worse in non-arteritic form
Vision lost does not recover in both conditions

40. Optic Chiasm

41. Causes pituitary tumor symptoms related to hormonal disturbance
Meningioma
Craniopharyngioma 

42. Presentation Bitemporal hemianopia
Missing objects in the periphery of visual field
Difficulty in fusing images, causing the patient to complain of diplopia although eye position and movement are normal
Difficulty with tasks requiring stereopsis such as pouring water into a cup or threading a needle

43. Optic Tract, Radiation & the Visual Cortex

44. Causes tract - vascular or neoplastic radiation - neoplasia
cortex - cerebrovascular accident

45. Presentation Homonymous hemianopic field defect tract - incongruous
radiation or cortex - congruous 
Visual loss is of rapid onset; a slower onset suggests a space-occupying lesion