"Conquering any difficulty always gives one a secret joy,
for it means pushing back a boundary-line and
adding to one's liberty."

- Henri Frederic Amiel


Explorative Saccade Training (EST)

 

A full visual field allows us to appreciate the world around us without moving our eyes or head. Once we detect an object of concern in the periphery, we can then make a precise shift (saccade) of our eyes to that spot. With a homonymous hemianopsia, there is a loss of one half of the visual field on the same side in both eyes. These patients no longer can pick up objects to the impaired side without moving the head and/or eyes to that side. This may result in individuals running into objects, being startled from items appearing suddenly, difficulty locating things, tripping, spilling drinks, reading difficulties and anxiety in travel especially in crowded areas.

Thus compensatory eye and head movements are important in these patients. Studies show, however, that a large portion of patients with homonymous hemianopsia generally perform saccades that are too short or hypometric. These shifts of the eyes are too small to compensate for their visual field loss. Improving the patient’s ability to accurately perform both larger and more accurate saccadic eye movements to the side of the loss can improve the patient's functioning in mobility and activities of daily living.

Saccadic training in various forms is usually the first step in helping the hemianopsia patient compensate for their visual field loss often beginning in the hospital or rehabilitation center. Multiple studies have shown the benefit of training exploratory saccadic eye movements. One of the most recent studies (Neurology 2009) concluded:

 “Explorative saccade training selectively improves saccadic behavior, natural search, and scene exploration on the blind side. The findings show substantial benefits of compensatory exploration training, including subjective improvements in mastering daily-life activities, in a randomized controlled trial.”

T. Roth, MSc, A. N. Sokolov, PhD, A. Messias, MD, P. Roth, MD, M. Weller, MD and S. Trauzettel-Klosinski, MD, Comparing explorative saccade and flicker training in hemianopia, A randomized controlled study. NEUROLOGY 2009;72:324-331

 

Hemianopsia – with or without Saccadic Eye Impairments

The loss of the visual field alone does not fully explain the problems in saccadic eye movements. The ability to make compensatory saccades differs among hemianoptic patients. Some patients adapt quickly, demonstrate adequate saccades, and function well in everyday life activities while other continue to struggle long after the event. 

Zhil (1999) looked at a group of 70 patients and found that those reporting no problems in activities of daily living demonstrated normal saccadic ability, but those still reporting difficulties with activities of daily living continued to show impaired saccades.

 

“Subjects with visual complaints showed significantly longer scanning times and a higher number of fixations and refixations. In contrast, patients without complaints performed within the range of normal control subjects."

Zihl, Josef  Oculomotor scanning performance in subjects with homonymous visual field disorders, Visual Impairment Research, 1999, Vol. 1, No. 1, Pages 23-31

 

Other tracts of the brain, which are responsible for saccadic eye movements, may also be damaged in many hemianopsia patients and this may add to their difficulty in generating saccadic searching eye movements into the impaired visual field.

 Zhil (1999) and others have suggested that subcortical connecting fibers in the occipital lobe, the posterior thalamus, or occipito-parietal visual areas in the latter group may result in the significant impairment of saccadic compensation in these patients that does not occur in the successful group.

This may also explain why we see that some patients with recent visual field loss, who do not need optical visual field expanders because saccadic movements alone compensate well while others are struggling years after the original field loss and greatly benefit from optical visual field expanders.   

Explorative Saccade Training (EST): Saccadic training to explore the area of visual field loss is and should be the first vision therapy with nearly all homonymous hemianopsia patients. It is usually initiated with an occupational therapist in the hospital or rehab center. Some will need minimal treatment, but others may need much more therapy.  The latter group we may have damage to other areas of the brain that effects saccadic eye movements. This latter group may also benefit from optical visual field expanders daily and both groups may benefit from visual field expanders in mo complex activities like driving and navigating in crowded places.

In patients with hemianopic orientation disorder, compensatory saccadic training selectively improves exploratory eye movements, ability to naturally search the impaired field area search, and scanning on the blind side, and thus subjectively improve activities of daily living.

 

Clinical Training Techniques

Exploratory Saccade Training (EST),  also called Scanning Therapy, can be performed in many different manners. A variety of different devices, software programs and strategies have been developed.  Below we will discuss some of these methods.

Initially, head movements should be reduced in favor of eye movements. The first step is to train the patient to make large exploratory eye movements (saccades) into the field of loss. This shifts the existing visual field to that side and allows the patient to then detect objects in the remaining visual field and make smaller accurate saccades to the exact object. After the large saccades are developed, smaller more precise saccades can then be trained. The third step, we recommend is to improve speed in real world situations. The fourth step is to attempt to integrate the scanning into real world activities.

The therapist will provide a number of therapies to improve your scanning. The following shows some simple steps in improving saccadic movements with the protocol of large saccade to smaller more precise saccades to increasing speeds of the search and saccade process. Many of the can be done outside the rehabilitation center.

 

Large Saccades Training Activities

  • Dynavision and Similar Training Devices
  • Head and Eye Shifts
  • Descriptive Walking
  • Walking Strategies
  • Post-it Note Hallways
  • Search Strategies
  • Large Table Cards
  • Wii Tennis

Small Precise Saccadic Training

  • Double Hart Chart Therapy
  • Puzzles
  • Pen and Paper Search
  • Newspaper Cancellation Therapies
  • Last Letter Cancellation for Right Hemianopsia
  • Computerized Trainers

Saccadic Speed Training

  • Descriptive Driving (regardless of potential driving status)
  • Wii Tennis
  • Table Tennis and similar activities
  • Dynavision

 

Please contact us if you have any questions.

The Low Vision Centers of Indiana
Richard L. Windsor, O.D., F.A.A.O., D.P.N.A.P.
Craig Allen Ford, O.D., F.A.A.O.
Laura K. Windsor, O.D., F.A.A.O.

Indianapolis    (317) 844-0919
Fort Wayne     (260) 432-0575
Hartford City   (765) 348-2020

info@eyeassociates.com