neurosciencestuff
neurosciencestuff:

A simple eye test for multiple sclerosis
As you step outdoors into the bright sunshine, your pupils automatically contract. Scientists from the Australian Centre of Excellence in Vision Science (ACEVS) based at The Australian National University (ANU) are making use of how this ‘pupil reflex’ is connected to the brain as a potential new way of testing the severity of multiple sclerosis (MS).
Dr Eman Ali and her ACEVS colleagues have used an instrument they are developing to accurately measure the pupil responses of MS patients and have found that the pupils of MS sufferers respond appreciably slower. The finding opens the door to a simple and quick way of tracking the severity of MS over time: the slower the response, the worse the MS.
“Our instrument uses special patterns of flashing lights that the patient looks at for four minutes,” says Professor Ted Maddess, a vision scientist at ANU who is head of the ACEVS team.
“We use infrared cameras to measure light-induced changes in the diameters of both pupils, and with computer tracking we can measure the diameter to within a micrometre 30 times a second.
“We have just published the results of our study of 85 MS patients, and we find that in MS patients the pupil response is about 25 milliseconds slower than in our control group. Although the study is preliminary, we believe the test has good potential in individual patients because it can precisely measure the speed of their response to within a millisecond.
“So instead of an expensive MRI to track the condition, the new method gives an accurate readout after just a few minutes. That quick and easy test might, in the future, allow MS patients to be assessed on the spot and have their medication adjusted accordingly,” he says.
MS is a potentially devastating neurological condition affecting the myelin sheath of nerve fibres, leading to sensory disturbances and muscle weakness. Vision, speech, and walking are most often affected, and pain can occur. Puzzlingly, MS affects different people in different ways, but the condition inexorably gets worse with age and there is currently no cure. Some patients experience acute, inflammatory attacks while others don’t.
“MS is the most common neurological disability in adults, with about 12,000 sufferers in Australia,” says Professor Maddess. “Although it seems to be some sort of immune disorder, its cause is still obscure.
“There are many puzzling aspects to MS, and there are many theories,” he says. “But our main aim in this work was just to find a way of accurately monitoring the progression of the disease, a single measure that relates to the degree of disability. MRI is good for giving insight into the inflammation associated with episodic attacks, but it’s not so good at monitoring the chronic decline that’s always going on.
“If we can use our pupil measurements to monitor the decline, we might be in a better position to adjust medications, which often have unpleasant side-effects.”
The instrument to measure the pupil responses is the same one which has also been shown to be helpful in diagnosing vision loss in glaucoma, diabetes, and age-related macular degeneration. The device was developed by Professor Maddess together with Associate Professor Andrew James and other ACEVS team members. Under the name TrueField, it is being commercially developed by an Australian company, Seeing Machines, which plans to sell it as a multipurpose medical diagnostic instrument.
TrueField has already received American FDA clearance, and Professor Maddess is hopeful it might, after some more research, also find a role in monitoring MS. He believes it has good prospects of reducing the high treatment costs associated with the disease.
The paper by Dr Ali and colleagues, “Pupillary response to sparse multifocal stimuli in multiple sclerosis patients”, is available online in the Multiple Sclerosis Journal.

neurosciencestuff:

A simple eye test for multiple sclerosis

As you step outdoors into the bright sunshine, your pupils automatically contract. Scientists from the Australian Centre of Excellence in Vision Science (ACEVS) based at The Australian National University (ANU) are making use of how this ‘pupil reflex’ is connected to the brain as a potential new way of testing the severity of multiple sclerosis (MS).

Dr Eman Ali and her ACEVS colleagues have used an instrument they are developing to accurately measure the pupil responses of MS patients and have found that the pupils of MS sufferers respond appreciably slower. The finding opens the door to a simple and quick way of tracking the severity of MS over time: the slower the response, the worse the MS.

“Our instrument uses special patterns of flashing lights that the patient looks at for four minutes,” says Professor Ted Maddess, a vision scientist at ANU who is head of the ACEVS team.

“We use infrared cameras to measure light-induced changes in the diameters of both pupils, and with computer tracking we can measure the diameter to within a micrometre 30 times a second.

“We have just published the results of our study of 85 MS patients, and we find that in MS patients the pupil response is about 25 milliseconds slower than in our control group. Although the study is preliminary, we believe the test has good potential in individual patients because it can precisely measure the speed of their response to within a millisecond.

“So instead of an expensive MRI to track the condition, the new method gives an accurate readout after just a few minutes. That quick and easy test might, in the future, allow MS patients to be assessed on the spot and have their medication adjusted accordingly,” he says.

MS is a potentially devastating neurological condition affecting the myelin sheath of nerve fibres, leading to sensory disturbances and muscle weakness. Vision, speech, and walking are most often affected, and pain can occur. Puzzlingly, MS affects different people in different ways, but the condition inexorably gets worse with age and there is currently no cure. Some patients experience acute, inflammatory attacks while others don’t.

“MS is the most common neurological disability in adults, with about 12,000 sufferers in Australia,” says Professor Maddess. “Although it seems to be some sort of immune disorder, its cause is still obscure.

“There are many puzzling aspects to MS, and there are many theories,” he says. “But our main aim in this work was just to find a way of accurately monitoring the progression of the disease, a single measure that relates to the degree of disability. MRI is good for giving insight into the inflammation associated with episodic attacks, but it’s not so good at monitoring the chronic decline that’s always going on.

“If we can use our pupil measurements to monitor the decline, we might be in a better position to adjust medications, which often have unpleasant side-effects.”

The instrument to measure the pupil responses is the same one which has also been shown to be helpful in diagnosing vision loss in glaucoma, diabetes, and age-related macular degeneration. The device was developed by Professor Maddess together with Associate Professor Andrew James and other ACEVS team members. Under the name TrueField, it is being commercially developed by an Australian company, Seeing Machines, which plans to sell it as a multipurpose medical diagnostic instrument.

TrueField has already received American FDA clearance, and Professor Maddess is hopeful it might, after some more research, also find a role in monitoring MS. He believes it has good prospects of reducing the high treatment costs associated with the disease.

The paper by Dr Ali and colleagues, “Pupillary response to sparse multifocal stimuli in multiple sclerosis patients”, is available online in the Multiple Sclerosis Journal.

dieselotherapy
dieselotherapy:

Skill: assessing pupil response.
Lets look a little closer at this particular skill.
First up, the pupil isn’t actually anything at all. A hole at the centre of the iris that controls the amount of light entering the eye. The size of this hole is controlled by 2 muscles within the iris. The pupilloconstrictor (controlled by the parasympathetic nervous system) and the pupillodilator (controlled by the sympathetic nervous system). So I guess what we are really assessing here is the iris response.
Pupil contraction (parasympathetic response):
When a light intensity increases across the rods and cones of the retina, impulses travel via the optic nerve to the pretectal nucleus of the upper midbrain.
From here impulses travel to the Edinger-Westphal nucleus, and onwards via the III cranial nerve (occulomotor) to the pupilloconstrictor muscle of the iris… causing contraction (miosis).
Pupil dilation (sympathetic response):
When light intensity decreases, impulses travel from the retina via the optic nerve to neurones on the hypothalamus where it takes a convoluted neuronal journey through the lateral brainstem to the spinal cord, down across the apex of the lung, back up alongside the internal carotid into the skull, through the inferior orbital fissure. Finally, it travels along the V cranial nerve (trigeminal) that innervates the pupillodilator muscle of iris… causing dilation (mydriasis).
How to assess pupillary reflexes.
Ideally, pupillary reflexes should be examined in a dim environment. If the patient is conscious, ask them to fix their gaze on a target some distance behind you ( If they re-focus on you or your torch, there may be pupil constriction as a result of accomodation).
Use a neurotorch or cheap penlight torch. This is for 2 reasons:
Using a superbright concentrated light will not be appreciated by a conscious patient.
Doctors do not (as a rule) carry neuro torches. They borrow the nurses. They forget to give them back.
Size and Equality.
The pupil size is documented as the diameter in millimetres. Tools to help you estimate this size include pupil gauges located on most Glasgow Coma Scale records and many neuro torches.
You may also find it useful in your written documentation to include descriptors such as: pinpoint, small, midposition, large, dilated.
Aniscoria: Up to 20% of the population have a slight difference in pupil size and is considered a normal variant. This difference should not be greater than 1mm and pupil reactivity should be normal.
Shape:
The pupil shape can be documented as round, irregular, oval or keyhole. Causes of irregular pupils include cataract surgery or the implantation of intra-occular lenses.
Oval pupils may be a result of compression of the III cranial nerve as a result of raised intracranial pressure (ICP). As ICP increases, the pupil will continue to dilate and eventually become non-reactive to light.
Keyhole pupils are seen in patients post iridectomy (a common part of cataract surgery). They may still react to light but usually the reactivity is sluggish.
Reactivity:
The pupil response to light is assessed by shining a neuro torch (or low powered penlight torch) separately into each eye. Tip: shining the torch onto the pupil from directly above may make assessment difficult due to ‘glare’ reflected off the cornea. Instead, position yourself in front of the eye and shine the beam from slightly off to one side.
Document pupil reactivity to light separately.Reactivity may be:
Brisk
Sluggish
Non-reactive.
At the same time look for the normal pupillary constriction response in the opposite eye. This is called the consensual pupillary response.
Accommodation:
This is the normal constriction of the pupil that occurs when a conscious patient is asked to shift their focus from a distant object, to a close one.
Causes of abnormal pupils:
Unequal pupils:
Mydriasis: One pupil is dilated and non-reactive whilst the other is normal. May be caused by compression of the III cranial nerve, compression of the posterior communicating artery or by direct damage to the nerve endings in the iris sphincter muscle.
Following a traumatic brain injury an increase in intracranial pressure can lead to the uncus (part of the temporal lobe) squeezing against the tentorium and pressing against the III cranial nerve resulting in a dilated pupil (mydriasis) on the affected (ipsilateral) side.If pressure continues to increase, contralateral dilation will also occur.
Horner’s Syndrome: One pupil is smaller than the other and has a decreased response to light and accommodation. There is ptosis of the eyelid on the affected side. Caused by loss of sympathetic intervention to the pupil due to a lesion in the brainstem of spinal cord, or damage to the hypothalamus. There is also decreased sweating (Anhidrosis) of some or all of the face. Causes of Horner’s syndrome include carotid artery dissection, nasopharyngeal tumours, brachial plexus injury.
Dilated pupils:
Drug induced mydriasis: bilateral dilation as a result of drugs including antihistamines, hallucinogens, amphetamines, anticholinergics, dopamine or barbiturates. May be caused by medication used for ophthalmic examination such as atropine, scopolamine, or by anoxia or brain death.
Mental or emotional stimulation: Dilation may also be caused by sexual arousal or increased mental effort.
Constricted pupils
Miosis: Bilateral pinpoint pupils (usually too small to figure out if they are responding to light or not). May be caused by disruption to the sympathetic pathway due to intraocular inflammation or direct trauma, a pontine haemorrhage, or due to the effect of drugs such as opiates, pilocarpine or acetylcholine.
Equal pupils:
Hippus: Initially react to light but then alternate between dilated and constricted. May indicate early compression of III cranial nerve. May indicate injury to the midbrain or barbiturate toxicity.
Relative Afferent Pupillary Defect (RAPD): When light is shone into the effected eye there is a sluggish reaction. There is a normal consensual reaction when light is shone into the opposite eye, but when the light is quickly shone back to the effected eye it will dilate. This is known as the swinging flashlight test (see video below) and may indicate optic neuritis, retinal detachment or infection or direct optic nerve damage.
In conclusion, a pupil assessment is a quick but important skill that can give a great deal of information. The eyes may indeed be the windows to the soul. But the pupils are the manholes to the ongoing neurological status of your patient.
(x)
 

dieselotherapy:

Skill: assessing pupil response.

Lets look a little closer at this particular skill.

First up, the pupil isn’t actually anything at all.
A hole at the centre of the iris that controls the amount of light entering the eye.
The size of this hole is controlled by 2 muscles within the iris.
The pupilloconstrictor (controlled by the parasympathetic nervous system) and the pupillodilator (controlled by the sympathetic nervous system).
So I guess what we are really assessing here is the iris response.

Pupil contraction (parasympathetic response):

When a light intensity increases across the rods and cones of the retina, impulses travel via the optic nerve to the pretectal nucleus of the upper midbrain.

From here impulses travel to the Edinger-Westphal nucleus, and onwards via the III cranial nerve (occulomotor) to the pupilloconstrictor muscle of the iris… causing contraction (miosis).

Pupil dilation (sympathetic response):

When light intensity decreases, impulses travel from the retina via the optic nerve to neurones on the hypothalamus where it takes a convoluted neuronal journey through the lateral brainstem to the spinal cord, down across the apex of the lung, back up alongside the internal carotid into the skull, through the inferior orbital fissure. Finally, it travels along the V cranial nerve (trigeminal) that innervates the pupillodilator muscle of iris… causing dilation (mydriasis).

How to assess pupillary reflexes.

Ideally, pupillary reflexes should be examined in a dim environment.
If the patient is conscious, ask them to fix their gaze on a target some distance behind you ( If they re-focus on you or your torch, there may be pupil constriction as a result of accomodation).

Use a neurotorch or cheap penlight torch. This is for 2 reasons:

Using a superbright concentrated light will not be appreciated by a conscious patient.

Doctors do not (as a rule) carry neuro torches.
They borrow the nurses.
They forget to give them back.

Size and Equality.

The pupil size is documented as the diameter in millimetres. Tools to help you estimate this size include pupil gauges located on most Glasgow Coma Scale records and many neuro torches.

You may also find it useful in your written documentation to include descriptors such as: pinpoint, small, midposition, large, dilated.

Aniscoria:
Up to 20% of the population have a slight difference in pupil size and is considered a normal variant. This difference should not be greater than 1mm and pupil reactivity should be normal.

Shape:

The pupil shape can be documented as round, irregular, oval or keyhole.
Causes of irregular pupils include cataract surgery or the implantation of intra-occular lenses.

Oval pupils may be a result of compression of the III cranial nerve as a result of raised intracranial pressure (ICP).
As ICP increases, the pupil will continue to dilate and eventually become non-reactive to light.

Keyhole pupils are seen in patients post iridectomy (a common part of cataract surgery). They may still react to light but usually the reactivity is sluggish.

Reactivity:

The pupil response to light is assessed by shining a neuro torch (or low powered penlight torch) separately into each eye.
Tip: shining the torch onto the pupil from directly above may make assessment difficult due to ‘glare’ reflected off the cornea. Instead, position yourself in front of the eye and shine the beam from slightly off to one side.

Document pupil reactivity to light separately.
Reactivity may be:

Brisk

Sluggish

Non-reactive.

At the same time look for the normal pupillary constriction response in the opposite eye. This is called the consensual pupillary response.

Accommodation:

This is the normal constriction of the pupil that occurs when a conscious patient is asked to shift their focus from a distant object, to a close one.

Causes of abnormal pupils:

Unequal pupils:

Mydriasis: One pupil is dilated and non-reactive whilst the other is normal.
May be caused by compression of the III cranial nerve, compression of the posterior communicating artery or by direct damage to the nerve endings in the iris sphincter muscle.

Following a traumatic brain injury an increase in intracranial pressure can lead to the uncus (part of the temporal lobe) squeezing against the tentorium and pressing against the III cranial nerve resulting in a dilated pupil (mydriasis) on the affected (ipsilateral) side.
If pressure continues to increase, contralateral dilation will also occur.

Horner’s Syndrome: One pupil is smaller than the other and has a decreased response to light and accommodation. There is ptosis of the eyelid on the affected side.
Caused by loss of sympathetic intervention to the pupil due to a lesion in the brainstem of spinal cord, or damage to the hypothalamus. There is also decreased sweating (Anhidrosis) of some or all of the face.
Causes of Horner’s syndrome include carotid artery dissection, nasopharyngeal tumours, brachial plexus injury.

Dilated pupils:

Drug induced mydriasis: bilateral dilation as a result of drugs including antihistamines, hallucinogens, amphetamines, anticholinergics, dopamine or barbiturates.
May be caused by medication used for ophthalmic examination such as atropine, scopolamine, or by anoxia or brain death.

Mental or emotional stimulation: Dilation may also be caused by sexual arousal or increased mental effort.

Constricted pupils

Miosis: Bilateral pinpoint pupils (usually too small to figure out if they are responding to light or not).
May be caused by disruption to the sympathetic pathway due to intraocular inflammation or direct trauma, a pontine haemorrhage, or due to the effect of drugs such as opiates, pilocarpine or acetylcholine.

Equal pupils:

Hippus: Initially react to light but then alternate between dilated and constricted.
May indicate early compression of III cranial nerve.
May indicate injury to the midbrain or barbiturate toxicity.

Relative Afferent Pupillary Defect (RAPD): When light is shone into the effected eye there is a sluggish reaction. There is a normal consensual reaction when light is shone into the opposite eye, but when the light is quickly shone back to the effected eye it will dilate.
This is known as the swinging flashlight test (see video below) and may indicate optic neuritis, retinal detachment or infection or direct optic nerve damage.

In conclusion, a pupil assessment is a quick but important skill that can give a great deal of information.
The eyes may indeed be the windows to the soul. But the pupils are the manholes to the ongoing neurological status of your patient.

(x)

 

sweatbomb

sweatbomb:

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