Neuro Ophthalmology Double Vision Disorders of the visual field Severe Headache Abnormal drooping the lids (Ptosis)


1.What does Neuro Ophthalmology deal with?

 Neuro ophthalmology deals with visual problems, which are due to disorders of the brain. The eye is not an isolated organ acting independently. It is an extension of the brain and it sends visual impulses into the brain and lets the brain recognize the images seen by the eye. Thus some disorders of the brain can involve the visual nerve fibers in its substance and cause visual disturbances.



2.What are the ways in which these disorders of brain can cause visual problems?

It can cause:

  • Decrease in central vision
  • Disorder of the visual field (Side vision)
  • Double vision (seeing double due to misalignment of the eye with abnormal eye movements)
  • Pupillary abnormalities
  • abnormal drooping of the eyelids.
  • It can simply manifest as a severe headache, which may or may not be associated intermittent blurring of vision and vomiting.



Double vision

Most common cause of acute binocular double vision is Micro vascular cranial nerve palsy.Most common precipitating factor is uncontrolled diabetes and/or Hypertension.

FAQS

1. What is the cause of cranial nerve palsy in diabetes?

It is due to decrease in the blood supply to the nerves supplying the eye muscles causing it not to work thereby causing misalignment along the two eyes.

2.How can I get relieved of this troublesome double vision?

The diplopia (double vision) will take some time to resolve (about 6 - 8 weeks). However, it will always resolve completely within that time provided the diabetes and hypertension are under control.During the acute phase, occluding on eye with an occluder fixed on the glasses or a patch can temporarily relieve the troublesome diplopia.

3.Can I have some other serious underlying problem? Isn't a CT scan necessary?

Most cases of isolated single nerve palsies are not due to any major abnormalities. Costly procedures like CT scan are not immediately required unless there is any other associated problem. However, if the nerve palsy does not get better beyond 3 months in spite of having diabetes and/or hypertension under control, then your doctor will consider a CT or MRI scan.

4.Why do I have a pain surrounding the eyes?

This pain is due to the decreased blood supply and the associated Ischaemia. The pain is temporary and it usually gets relieved with anti-inflammatory medications.

5.Can cranial nerve palsy cause decrease in my vision?

No, it cannot cause directly a decrease in the vision in the affected eye except for the troublesome diplopia. However, one should remember that there might be an associated retinal pathology (the nerves within the eye responsible for vision) due to the diabetes. These also should be looked for to rule out any diabetic retinopathy by the ophthalmologist.

6.Will I have a recurrence of this problem?

Some patients may have a recurrence of this problem at some time if their diabetic status is uncontrolled.

7.What if the double vision doesn't resolve at all?

In some cases, it may not resolve completely. In such cases if the diplopia is troublesome it can be relieved in the special lenses called prisms fitted onto your glasses or eye muscle surgery can be performed.
Vision of a normal person




Vision of a diplopia patient




Misalignment of eyes
Disorders of the visual field

1. What is meant by visual field?

When we look straight at an object we see not only the object focused on, but also the objects to the side of it, which is defined by limits on all directions. This is the visual field.

2.What are the various disorders of the visual field that can occur?

  • Central Scotoma
  • Homonymous Hemianopia
  • Bitemporal hemianopia
  • Altitudinal field defect

3.What are the causes of the visual field defects?

Central Scotoma :
Scotoma is a non seen area within a seeing area. It can be due to disorders of the optic nerve, the nerve which connects the eye to the Brain or Macular Problem-The Central area within the eye which is responsible for central fixation of the eye.

Homonymous field defects :
Homonymous means same side of the visual field in both eyes . This occurs in the back of the brain where part of the nerve fibers from both the eyes join. It is usually due to interruption in blood supply to the nerves (Infarction) and occasionally due to tumours.

Bitemporal field defects:
This means the temporal field (outer field) of both the eyes are affected. This usually occurs in the base of the brain where the nerves from both the eyes cross each other at the optic chiasm. (Chiasm - X - in Greek).

The most common cause is the pituitary adenoma - a beningn overgrowth from the pituitary gland - the master gland that controls all other endocrine gland within the body - When it is grown to a considerable extent.












              CENTRAL SCOTOMA




      HOMONYMOUS HEMIANOPIA

FAQs

1.Will all Pituitary adenoma produce field defects ?

 No. The Pituitary adenoma has to grow considerably (approximately 10 mm above) to press on the chiasma to produce field defects.

2.Will not then an early pituitary adenoma be undetected ?

No, It can produce endocrine problems by which it may be suspected and then subsequently detected by CT scan.

3.Will my field defects go away?

It depends on the type of field defect and the cause of the field defect. Pituitary adenoma when removed may produce complete resolution of field defects if removed early enough.

However Infarction to the brain (loss of blood supply) may produce a permanent field defect which may be difficult to resolve. Very occasionally early treatment with injections like Heparin (which lyses the clot) can cause resolution of the field defects produced by blockage of blood supply.

      BITEMPORAL HEMIANOPIA
Severe Headache

There are so many causes of headaches including refractive errors, Sinusitis, Migraine, or due to raised intracranial pressure (Increased pressure in the head) with or without a intra cranial space-occupying lesion.

Raised intracranial pressure will produce a condition called papilloedema within eyes (which means fluid collection around the optic nerve head within the eye). This is due to transmitted pressure from within the head.

If papilloedema is confirmed then the doctor will order a CT Scan or a MRI Scan . If a space occupying lesion is found in the scan then surgical removal of the lesion will relieve the papilloedema. If no space occupying lesion is found then the condition is called pseudotumor cerebri. Usually the patients with pseudotumour cerebri are slightly overweight young women. However it may also occur in children, men and patients who are not overweight. Their main complaint is headache which may be severe. Other symptoms may be transient obscurations of vision which lasts for a few seconds and occasionally nausea and vomiting also.

The treatment is a pressure reducing drug called diamox (acetazolamide) along with weight reduction.

FAQs

1.Is there really a tumour inside the head in psuedotumor cerebri ?

The term "pseudo" excludes the possibility of a tumor within the head. Since the signs and symptoms mimicked that of a tumour the condition is called pseudotumor cerebri.

2.How long will I have to continue diamox?

In some cases as long as 1-2 years also till the doctor decides that the pressure inside the head is adequately controlled.

3.Once the headache is relieved, Can I discontinue the tablets?

No. Resolution of headache can allow in reduction in the dosage of the drug but not completely withdraw it. Only when the optic disc oedema is completely resolved and there is no further damage to the visual function then the doctor will consider withdrawing the tablets.

4.If there is no tumour, then is there a risk to the life of the patient with 'pseudotumour cerebri'?

No, there is no risk to the life of the patient, but there is a real threat to the vision of the patient due to the continued pressure around the optic nerve head ( the nerve which connects the eye to the brain) by fluid.




NORMAL OPTIC NERVE HEAD







        PAPILLOEDEMA







        TRANSIENT BLURRING OF VISION

     
Abnormal drooping the lids (Ptosis)


Normally the lids just touch the upper edge of the cornea - the transparent structure in front of the eye. There are a variety of reasons when it may fall down abnormally. It could be due to ageing producing weakness, trauma, congenital etc., Neuro ophthalmic causes include 3rd cranial nerve palsy and a condition called myasthenia gravis.

Myasthenia gravis is a condition of weakness of the muscle contraction due to abnormal chemicals (autoantibiotics) directed against the muscle receptors. This has a predilection to affect the eye muscles first producing ptosis as well as ocular misalignment producing diplopia (double vision). Muscles elsewhere in the body may also be affected subsequently.

FAQs

1.why is the ptosis and diplopia variable - better in the mornings and worse in the evenings?

This is due to progressive muscle fatigue towards the end of the day and they need more chemicals to get stimulated which is in short supply in myasthenia.

2.What will be my other symptoms if other muscles are affected ?

It can affect the other proximal muscles of the limbs which can lead to difficulty in lifting objects or difficulty in getting up from squatting position. It can also cause difficulty in swallowing or breathing.

3.What is the chance that my other muscles will be affected other than the eye muscles?

Usually 60 - 80% of the patients start with ocular symptoms but half of them will eventually develop generalized symptoms within the next 2 years if left untreated. After 2 years the possibility of involvement of other muscles is low.

4.How long will I have to continue drugs?

There is no absolute cure for the disease and only the symptoms may be relieved. Immunomodulators like steroids and immuno suppressives may eventually cause remission of the disease in some patients.