Dr. Riyad Banayot

Most common field defects and their underlying conditions are:

Tunnel vision in advanced retinitis pigmentosa and advanced glaucoma

Altitudinal field defect in ischaemic optic neuropathy and branch retinal artery occlusion

Arcuate scotoma in glaucoma

MRI of the optic nerves and the visual pathway

Lesion at junction between the optic nerve and the

chiasm

Lesion around the

optic chiasm

Lesion in the optic tract

Lesion in the temporal/parietal

lobe

Lesion in the occipital lobe

Lesion resulting from inflammation of the optic disc

Remember to describe the visual field as the patient sees it.

Mention if the field defect is congruous (behind the lateral geniculate body) or incongruous (in the optic tract).

Look for other neurological signs such as hemiplegia from cerebrovascular accident.

The peripheral visual

fields are normal in both

eyes.

There is a right central

scotoma (revealed by

testing the central field with a

red pin).

Examine the patient's

fundus for any evidence

of papillitis or optic

atrophy.

Check for RAPD.

The patient has a right

central scotoma and

superior temporal field

defect in the left eye.

The findings suggest a

lesion in the junction

between the optic

nerve and the chiasm

on the side with the

central scotoma.

It is caused by compression of the knee of Wilbrand which is a loop of inferior nasal fibers.

This enters the contralateral optic nerve for a short distance before traveling in the optic tract.

Examine the fundi for optic atrophy on the side with central scotoma and possible papilloedema on the other side.

Look for causes. The most common causes are meningioma (the patient may have proptosis ) and a prefixed pituitary tumor (the patient may have signs of hypopituitarism or Acromegaly).

There is bitemporal

hemianopia which obeys the

midline

(the hemianopia may be

worse in one eye than the

other or denser superiorly or

inferiorly).

This suggests a lesion in the

optic chiasm.

- The hemianopia may be subtle and revealed only by comparing two red objects in each hemifield. The red color in the temporal field appears washed out. - If the hemianopia does not obey midline consider pseudo-bitemporal hemianopia such as bilateral sectoral retinitis pigmentosa, tilted discs or bilateral infero-temporal retinoschisis. Examine the fundi for any such changes. - Examine for features of pituitary abnormalities such as acromegaly, pan-hypopituitarism (smooth skin and absence body hair in male) - Look for any scar suggestive of pituitary operation.

There is left incongrous (the shape of the defect is

different in the two half fields)

homonymous

hemianopia

The lesion is in the right

optic tract).

Lesions associated with

optic tract are often

associated with

contralateral pyramidal

signs (due to damage to

the cerebral peduncle)

such as spasticity.

Left superior homonymous quadrinopia

Left inferior homonymous quadrinopia

The optic radiation is found

in both the temporal lobe

and the parietal lobe.

- In a patient with a left

superior homonymous

quadrinopia, the lesion is

likely to be in the temporal

lobe.

- Left inferior homonymous

quadrinopia is seen in lesion

of the parietal lobe.

Test the patient for Gertmann's syndrome ?

Gertmann's syndrome which is seen in lesion of the dominant parietal lobe which is usually the left in right handed person

Failure of patient's ability to calculate, name fingers and tell left from right

Perform the opto-kinetic drum test for evidence of parietal lobe lesion ?

There is impaired pursuit movement to the side of the lesion.

Astereognosis (failure to tell an object through touch)

Joint position sense loss

Loss of two point discrimination

Alternatively touching the patient's right then his left hand and then touching the two hand together (with patient's eyes closed).

If the patient has sensory inattention, he would notice only one side being touched when you touch both his hands simultaneously.

Normal opticokinetic nystagmus

with smooth pursuit movement.

Abnormal opticokinetic

nystagmus with small saccadic

movement replacing the

smooth pursuit movement.

Left homonymous hemianopia

left homonymous hemianopia with

macular sparing

Lesion of the optic radiation as it

approaches the occipital cortex

can lead to homonymous

hemianopia which is often

congruous.

Lesion of the occipital cortex may

produce macular-sparing

homonymous hemianopia this is

most often seen in

cerebrovascular accident

involving the posterior cerebral

artery.

Testing for macular sparing is

done by moving a red target form

the non-seeing field into the

seeing field. If the red pin is

noticed before it crosses the mid-

line, macular sparing is present.

History: Acute (vascular disorder) or

Chronic (space-occupying lesion)

History of CVD, DM and smoking

Examination: Cardiovascular examination for hypertension, atrial

fibrillation, cardiac disorders and carotid artery disease.

Neurological examination for raised ICP

Blood tests for full blood count for hyperviscosity conditions such as polycythemia, ESR (? Vasculitis)

CT scan for CVA, space occupying lesion.

Chest X-ray if there is evidence of cerebral space-occupying lesion.