Homonymous visual field defects, such as hemianopia, involve partial blindness in both eyes which occurs following damage to the parts of the brain responsible for processing visual information. They are one of the most common and disabling consequences of brain damage, with the visual loss impacting on numerous everyday activities like crossing the street, avoiding obstacles, shopping, reading and driving.
Here in the psychology department at Durham University we have been investigating homonymous visual field defects and have been developing training programs that may be used in the rehabilitation of such impairments. The aim of our training is not to try and restore the lost vision but rather to help people to learn compensatory strategies to help them overcome the difficulties which they experience due to the visual deficit.
Our most recent training program (Durham Reading and Exploration training; DREX) is computer-based and self-adjusting, allowing people to train themselves easily in their own home. It involves a series of tasks which encourage visual exploration. These gradually get more difficult thereby promoting the development of more efficient eye-movements and increased visual awareness. Half of the training is also specifically tailored towards improving reading, a common problem associated with visual field loss.
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Individuals with homonymous visual field defects (HVFDs) have lost vision in the same portion of each eye. This is not due to any injury to the eyes themselves, but is instead the result of damage to the primary visual pathway within the brain (see Figure 1 below). Damage to the right side of the brain leads to visual loss on the left side, and vice-versa. There are various different types of HVFDs, including hemianopia where half of the visual field is blind, quadrantanopia where the blindness is restricted to a quarter of the visual field, and scotomas which are blind spots occurring within the visual field (examples for each are shown below). The type of HVFD which an individual develops depends on the location and size of the brain damage.
Figure 1: Primary Visual Pathway - Damage to the retina leads to visual loss in the corresponding eye only. Damage to the parts of the visual system after the optic chiasm lead to blindness in the opposite side to the site of injury.
HVFDs are one of the most frequent and disabling consequences of brain injury, and individuals with such visual loss exhibit slow and inefficient visual exploration of their environment, are visually disoriented and experience problems such as finding objects, avoiding obstacles and reading. The problems are made worse in very demanding situations, such as when trying to find specific items in a shop, or when crossing a busy road. The impairment has a significant negative impact on functioning and quality of life. Spontaneous visual recovery is limited and full recovery is rare. Despite the frequency and debilitating consequences of this condition there are currently no standard treatments available.
Figure 2: Types of HVFDs. A) Hemianopia B) Quadrantanopia C) Paracentral scotoma
The DREX training app can be accessed on Apple iPad or Android tablet. The app is not available on mobile phones. Once the app is downloaded you will first need to register and provide some details.
After registering an account you will firstly need to complete an assessment. The assessment contains a range of different tasks including perimetry, visual search and a quality of life questionnaire. After completing this assessment, you will have a choice between Exploration training and Reading training. Once you pick one of these options you will complete a number of rounds of this training type in which you will be assessed periodically. After three assessments you will be able to switch to the training type you did not pick initially. It is important to pick the type of training you wish to improve most as once you select a training type it will be some time before you can complete the other type. The flowchart below demonstrates this.
DREX Android Installation Guide (PDF download)
DREX Apple Installation Guide (PDF download)
DREX Tablet User Guide (PDF download)
DREX User Guide PC (PDF download)
This research has helped me greatly. It has made me concentrate much more as I was getting pretty lazy, as well as making me more focussed with my reading. I find I read a lot more now because I find it easier and more comfortable. I hope you implement this in more hospitals and carry on with the research you are doing because I believe it will help a lot of people gain more confidence in their sight.