Hemispatial Neglect or Field cut?

Field cut vs. Neglect following Stroke

Patients frequently present with a reduced awareness of their affected side following a stroke or brain injury.  This decreased awareness can be a visual field cut or a hemi-spatial neglect or both. Here are some ways to tell just why your patient cannot find half of the world.

Anatomy of field cut vs. neglect

A stroke with neurological neglect is generally associated with middle cerebral artery strokes. These are the most common strokes. The temporal/parietal lobes tend to be affected in these strokes with hemiplegia also occurring.

Generally, a true field cut is associated with a posterior cerebral artery stroke with the occipital lobe being affected. This is stroke is less common. The patient may not have any other symptoms from the stroke.

Functional differences between field cut and neglect

There are many difference functional in patients that have neglect vs field cut.

Patients with a field cuts:

  • show awareness of the field cut, they will tell you “I can see on my right side”
  • They begin compensations quickly
  • Show organized search patterns during cancellations tasks. This mean left to right, top to bottom pattern

Patients with neglect present differently

  • They may not be aware of the field loss and may not be aware of any of the stroke related deficits. This lack of insight to their condition is a big hurdle to treatment
  • They do not compensate well. This is probably related to the lack of insight.
  • Problems with attention in general. Perseveration (unable to shift attention) and distractibility are common.
  • Patient with neglect have difficulty with crossing midline. The eyes may not track across midline to affected side.  Slow saccades to affected side.
  • Poor search patterns on cancellation tests.  These patients randomly search for targets. It is important to watch how a patient completes cancellation assessments as a patient with a field cut and neglect will have similar looking cancellation tests when completed.
  • These patients tend to be oriented (posture and head position) away from the affected side.

Treatment differences of field cut vs neglect

Early resolution of neglect is vital to improving functional status following stroke.  Here are some of my favorite activities for treating neglect:

Field cuts tend to be a bit easier and are discussed here.

Neglect and filed cuts are common consequences to stroke and confusion about just what the patient is experiencing can make treatment difficult. I hope the helps!!!

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Assessing visual fields

Assessing visual field in the OD office

Heres is how visual fields are assessed in the optometry office.

humphery

This is Humphery visual field tester. The test is generally done monocularly first. The patient places their face on the chin rest and clicks a switch when they see a light in the field. The device monitors fixation during the test and lets the tester know if the patient “cheated” by moving their eyes. Binocular testing may be done separately if needed. During this, the patient is allowed to move their eyes.

The results are very precise with even small peripheral reductions in field picked up. But there are some limitations. The patient must be able to respond in a timely manner by clicking a button, so motor response time and even posture can affect the ability to perform testing on this device.

Confrontation Field Testing

Visual field testing by confrontation is a way to perform visual field testing in clinic without the computerized tester.

In the test, the therapist sits in front of the patient presenting fingers in each field with patient reporting the number of fingers up. This is done for each eye.

It is important to present stimulus in all four quadrants of the visual field. Results of this can be correlated with other visual cancellation tests.

There is also campimetry which uses a specialized disk with different fixation points.

photo (15)

With the campimetry device shown above, the patient fixates on numbers on the disk and reports if they can see the middle spot.

There is also a web-based Damato Multifixation Campimeter test for visual fields that is  free.

Types of visual field cuts

Homonymous hemianopia is the most common visual field loss following a neurological event. This is lose of half of the visual field in each eye . These can affect right or left visual field (generally contralateral to the affected side of the brain, left brain right field cut). These tend to be associated with tempro-parieital lobe or occipital lobe damage. Left side field cuts tend to have a neglect aspect associated with them. The patient may not even be aware of the left sided vision loss making treatment of the field cut more difficult. Right sided field cuts tend to be more occipital lobe related with the patient showing improved awareness of the loss and improved recovery. Here is what it would like using a Goldman 30-2 test. This test looks at each eye separately and requires fixation.  The similar patterns in each eye tells us this a visual pathway problem, not and orbit problems.

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Here is what it looks like on the Easterman Binocular Test. This test uses both eyes, allows for eye movements and is a more functional look at patient useful visual field.

visualfields-page-001

Quadrantanopia is loss of vision in a quadrant of the visual filed (upper right, lower right, upper left, lower left). It can also be homonymous (in both eyes) and may be described a superior right homonymous quadrantanopia.

quad

This is what that might look like.  They might also be bitemporal ( in the lateral fields of both eyes) or binasal (in the medial fields of both eyes)

A central scotoma is is loss of the central visual field and is associated with age-related macular degeneration.

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Visual field treatment

Their are two common strategies behind improving functional status for patients with a field cut. We tend to use a combination of both at the optometry office.

The most common technique is to improve scanning strategies by having the patient perform scanning tasks into the area of the field cut. This can be done with any number of devices such as a Dynavision or a Sanet Vision Integrator. Both of these devices, and others, present random targets in a field with the patients ability to find these targets being timed. With either of these, patient practice scanning strategies which improves their awareness of the field and improves their time locating targets in the missing field.

In optometry, we have other tools available. We can use field expansion systems such as the Peli-lens or Gottlieb Field awareness system. Both of these involve the application of small pieces of prism to the lens of the patients glasses. These small strips move visual stimuli into the patient’s existing field “reminding” them to look to the affect side.  They cue the patient to scan into the missing field, something like a warning system.

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Balance and Vision

 

Two Visual Pathways

The focal, central or Parvocelluar visual system is called the “What” vision system. It is responsible for object identification. It allows us to focus on a specific object in the visual field. This information is interpreted in the occipital lobe.

The ambient/peripheral or Magnocellular visual system is the “Where” system responsible for spatial information, balance, coordination and peripheral awareness. This information is shared with the occipital lobe, in addition to links to the cerebellum and balance areas of the brain. Functional MRI shows this information actually reaching 99% of the cortex. Using ambient vision, we can automatically change our posture and gait to walk uphill or protect ourselves from falling over as someone bumps into us.

Functionally, these two systems allow use to look at the road ahead of us (focal vision) and be aware of the car to our left(ambient). It also allows us look at the TV but be aware of where the door in the room is. It allows us to be focused on a word in reading, but still make accurate saccades to the next word.

Notice what happens to the people attempting to walk through the tunnel.

Notice how the people in the tunnel are leaning to one side. The tunnel walls have confused their ambient vision system and affected the gait and balance.

A tool for rehabilitation…

Frequently this system can become faulty following a neurological event. In a condition called Post Trauma Vision Syndrome”, patients become over-centrally focused. This is seen clinically as decreased balance, decreased reading accuracy and poor spatial awareness a midline shift or toe/heel walking.  The patients also report becoming “over-stimulated” by visual information.   A visual field done a patient with this condition might look like this

peripheral loss

This is one eye, but the other may look the same. Notice the reduced periphery that might not show up in typical in-clinic screening of visual fields.  This visual field test is called a Goldman 30-2 and is done on each eye.  It  should be a standard part of the assessment of all of the post-TBI/CVA patients.

Improving Ambient Visual Function

To improve function of the ambient system, binasal occlusion may be added to a patients glasses with or without mild base in prisms.  How does this help?

A person that is over-centrally focused has a difficult time seeing the entire word. They tend to see letters rather than the whole word which greatly reduces reading fluency and comprehension. Saccades also become less accurate due to the decreased awareness of the line of text  making the person lose their place frequently.

This can also improve posture and gait. As the brain becomes more aware of the ambient visual system, it is better able to correctly adjust gait and posture. Remember the tunnel?

Optometrists that offer this type of service are involved in neuro-optometry. The organization is called the Neuro-Optometric Rehabilitation Association. This is a multi-disciplinary organization that was started by ODs who wanted to understand brain injury better and exchange information with other providers of care in the  TBI community like OTs and PTs. There is a provider list on their website to help you find a NORA optometrist in your area.

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Assessing Eye Movements

Assessing Eye Movements

As therapists, we should assess EOM or extra ocular movements, the optometry term for eye range of motion. Looking at these movements can give information about brain and cranial nerve function as well as help identify limitations on functional tasks like reading .

Eye movements use similar names as other movements with inferior being downward, superior being upward, lateral movements described as duction with adduction  moving toward the nose (nasal)and abduction away from the nose (temporal). Optometry also has vergence, which is the movement of both eyes toward the nose (convergence) or away from the nose (divergence). Smooth convergence and divergence is important in the near focusing system.

With the patient seated and focused on a point about 40 cm away, the eyes should be still. This is called fixation.  A small rhythmic movement, called nystagmus, is a sign of a central nervous system problem. It is often associated central nervous system problems like Multiple Sclerosis.  It is a frequent early sign of the disorder. It is also closely linked to the vestibular system and the patient might report dizziness. When congenital, the brain adjusts to movements as in the video below.

Congenital Nystagmus

9 points of primary gaze are assessed having the patient follow a point to left/right/up/down/up left/low left/upright/low right. The eyes should move together through all of these points.

9points of gaze_normal_540

Assessing Cardinal Gaze

Each of these movements is control by cranial nerves and failure of an orbit to move in a direction could be a sign of cranial nerve problem or a muscle problem. This occurs frequently as a result of brain injury or trauma to the eye or orbit. This can also be congenital. This eye turn is referred to as a strabismus.  Strabismus causes diplopia or double vision. They can be improved with prism by an optometrist or possible surgery to shorten or lengthen the muscle by an ophthalmologist.

To assess convergence use the near point convergence test. In this assessment, a target held about 1 meter from the patient’s nose and slowly brought toward the nose. The patient is instructed to tell the tester when they see two of the targets. The target should get to within 6cm to be considered “normal”. The test should be done 5 times with the final result be the distance at which the child saw double on this final trial. Reduced convergence is not uncommon following brain injury and stroke and is linked to reading difficulty in children. Reduced convergence makes near vision tasks more difficult as the brain has work harder to see clear. This is called convergence insufficiency. The condition even has its own  website.  This has also become more common in adults we put demands on our near vision system with increased use of smart phones.

Near Point Convergence test

In tracking, the patient follows a target in a circular pattern, both clockwise and counter-clockwise making 2 revolutions each direction. Tester notes the number of fixation loses, the smoothness of the movements and the ability of the eyes to move together.

Eye Pursuits or Tracking

Saccades are very quick eye movements of very short duration. It is a series of fixations and saccades that allows one to read efficiently. Inaccurate saccades are frequently associated with poor reading skills. Optometry can improve saccade accuracy and improve reading .  Saccades testing has the patient fixate from one point to another with the tester noting adjustments following the fixation and if the eyes move together. We can perform the Developmental Test of Eye Movement  or the King-Devick for objective testing of eye movement.  Saccade accuracy can be an indicator for possible concussion as well.

Saccade testing

Abnormal EOM tests should be referred to optometry for complete assessment. They are often related to central nervous system problems, cranial nerve palsy’s or cerebellar problems. They are common in stroke and brain injury survivors and cause decreased reading ability, balance and depth perception.  Patients frequently suffer with eye movement problems for years following a stroke or brain injury, but with the right tools, they can be improved improving a patient’s functional ability.

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