Objective


Work in this laboratory is devoted to researching facts and developing tools to help the rehabilitation of people with low vision, especially those with macular vision loss.






Self-Exploration of the Visual Field by the Patient


Project Completed


Patients with scotomas (spots of diminished or no vision) often do not realize the nature of their deficit. We developed a technique that patients can use to heighten their awareness of scotomas. In the process of learning eccentric viewing, several stages have to be passed.

1. Use hand movements to find the location of best vision in the visual field of one eye, while the other eye is closed and gaze is fixed. 
2. Use eye movements to adjust gaze so that a target in a stable location looks best. 
3. Coordinate eye and hand movements, so that a magnifier can be moved where it is needed, namely at the location in the visual world that correspond to a Preferred Retinal Locus (PRL). 

The technique described here serves the purpose of stage 1 (above). We have developed two techniques to solve this problem. For both techniques, the examiner has to guess in which quadrant of the visual field the spot of best vision can be expected. This is possible by two simple techniques:



A. While examiner and patient confront each other, the patient is asked to look at the examiner’s nose. This allows the examiner to see the deviation of the patient’s gaze. Example: If the patient looks slightly up and right, the examiner can conclude that the patient is using a spot in the lower right of the visual field.

B. Conduct a simple topographic test of the patient’s visual field like the Macular Mapping Test (see "Macular Mapping Test", this website) or a tangent screen test. The results will indicate where there is relatively intact vision is available.


After this preliminary test, the screen or card (see below) should show free space in the quadrant indicated by the visual field test.


Visual Field Exploration

A. The scientific (“high-tech”) way: This is done with the help of a computer, a monitor and a light pen. The patient looks at the angle between two straight high contrast edges using the center of the retina. This is done even if the angle itself is seen blurred or disappears altogether due to a scotoma. Gaze should be held as stable as possible. 
Simultaneously, the patient moves their preferred hand holding a small light pen over the monitor screen. The light pen automatically moves a letter where ever the hand moves. The patient explores the visual field to examine changes in how the letter is seen: Sometimes clear, sometimes blurred, or sometimes not at all. When the patient reports the location of best vision, the examiner takes a note of it. (see part A in Figure below)



B. The practical (“low tech”) way: This is done with the help of a cardboard sheet that again shows an angle between two straight high contrast edges. The preferred hand is used to move a small piece of cardboard with a letter printed on it through the visual field. Thus, the field can be explored in the same way described above for the “high tech” method. 
Our experience with patients shows that they take to this procedure with interest and often with enthusiasm. We have also tested these methods against results of an examination by Scanning Laser Ophthalmoscope (SLO), which shows the location of a PRL with great precision. (see part B in Figure below)

Illustration of Procedure A and B - Self-Exploration of the Visual Field 







copyright by Manfred MacKeben 2010



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