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Low Vision Assessment and Rehabilitation

Initial Low Vision Management

Low Vision Treatment Options

It is a common misconception that enhancing impaired vision is just a matter of increasing the power of glasses. For any distance there is an optimal lens that focuses the image on the retina. A stronger lens will blur the image at distance and is therefore unhelpful. The exception is for near vision tasks. When print is brought closer to the face, it is larger and stronger bifocals or readers can sometimes be used to bring this close object into sharp focus; this will improve only reading vision.

Optical aids work in patients with low vision by increasing the image size on the back of the eye (the retina) so that objects appear larger. There really are no "magic glasses," only low vision aids.

The optical low vision aids for near vision often differ from aids used for distance vision. However, similar factors apply to the selection of visual aids at all distances.

In Dr. Cole's case these factors under consideration included:

• Identification of required tasks
  
• Fine and gross motor skills: Although there was some decrease in tactile sensitivity, this did not impair his ability to manipulate low vision aids.
  
• Eye dominance: Use of his dominant right eye was precluded initially because this eye was substantially worse affected. Ultimately, his right eye became the better eye.
  
• Monocular vs binocular: Dr. Cole functioned better initially with low vision aids using his left eye alone, and later with his right eye alone. Binocular vision was not possible because of the severe visual loss of the opposite eye.
  
• Preferred retinal locus: When central vision is damaged by retinal disease, such as with Dr. Cole's diabetic macular edema, a new area of maximal (albeit reduced) retinal sensitivity can develop. With training and practice, the patient can learn to develop and use this new preferred retinal loci of highest sensitivity, called the PRL, to enhance visual functioning. In the initial stage of low vision management the development of a PRL was prevented by his persisting diffuse macular edema.
  
• Lighting: The level of illumination is often critical in the use of low vision aids. Some individuals require extra illumination while others do not. Augmented illumination is commonly provided by illuminated hand or stand magnifiers.