Jun 18 2011
Hemianopia is a significant loss of vision after a stroke to the visual aspect of the brain. Most commonly, it takes out one section of vision in both eyes. With homonymous hemianopia the vision loss usually starts right in the middle of the eye and is missing on the same side of both eyes. In this case, it is a “Left Homonymous Hemianopia.
When the patient experiences this, there first reaction is that of devastation. No longer can they see a full page of text, or look forward and see who is on the their side. Walking becomes awkward and sometimes dangerous as cues that most people rely on are missing.
Can anything be done for this condition? Is it permanent? There are various thoughts on the matter. But in the end, if there is not a significant recovery within a few months, there is likely not going to be any improvement. There are no surgeries or magical things that can be done. Often, the person experiencing this may be dealing with other aspects of stroke. That is not always the case. Once the neurologist has released the patient to therapy, there are some options. I cannot speak to the day-to-day rehabilitation protocol for an occupational therapist. I can speak to the options that are available to the patient through a unique optical device that was developed by Eli Peli, O.D. also known as the “Peli Lens.”
This is what a room looks like to a normally sighted person, either with the right eye or the left. When looking in the room they see the center and everything to the left, right, up and down. For the person with a right hemianopia, everything to the right is missing in either the right or the left eye or both together. This is not a problem with the eye. This is after a blood clot hit the brain and destroyed the connection between the eye and the visual processing center of the brain.
The next image is a schematic drawing of the visual field of the normally sighted person.
This shows that there is vision in the superior, inferior, left and right line of sight. The next image will contrast that showing how the hemianopia patient has lost that ability to see to the side. With the use of specially fitted prism glasses, the hemianopia patient does not gain back what they lost, but they become aware of what is to the side by an additional 20 degrees. There is a newer design that allows the patient to see up to 30 degrees to the side of neglect. It is illustrated in the following photo.
The prisms are attached to the spectacles on the same side of neglect. There are specific instructions for how this is done. Prism lenses are designed to move an image to the right, left, up or down. The glasses are fit so that the eye is looking through the spectacle prescription. But above and below the line of sight are the lenses moving the image from the missing vision into the top and lower view. The patient may feel awkward for a few moments, but when they realize that they have gained back peripheral vision awareness, the adaptation period is rather short.
These lenses will never bring back the missing vision. They are designed for walking, talking, and general use. They will not bring a full page back into focus when the hemianopia patient is trying to read. They are a clever and unique design allowing increased awareness.
I will describe some of my fitting experiences in the near future. This lens and its use has been published in numerous peer reviewed publications. More can be learned about it and hemianopia by going to “>www.hemianopia.org.