“And when I see you, I really see you upside down” is not just a clever lyric from the Death Cab for Cutie song titled A Lack of Color, but an actual visual phenomenon. When light enters the sphere-shaped eye through the lens and the pupil, the image is turned upside down on the retina. This and many other facts about the visual system not only fascinate us, but also explain all the possible deficits in this complex system.
Processing of visual information starts as incoming light enters the front of eyes, progresses through the optic nerve at the back of the eye, crosses at the optic chiasm, travels down the optic tract through the lateral geniculate nucleus, and finally to the occipital lobes at the back of the cerebral cortex.1 A myriad of problems can occur as the information is processed through the optical, retinal, and neural pathways. When these problems occur, they can significantly impact a person’s ability to function.2
Many problems in the optical and retinal pathways are due to low vision disorders. Low vision disorders are progressive diseases that lead to chronic loss of sight and limit everyday function.3 Some of the low vision disorders that clients present with include macular degeneration, glaucoma, cataracts, and diabetic retinopathy. In addition to primary visual losses such as reduced central or peripheral vision that occur in these disorders, a person’s ability to function can be significantly impacted by a loss of contrast sensitivity and increased sensitivity to glare.
In Orli Weisser-Pike’s course titled Vision Loss and Older Adults, she describes how and when to use filters, enlargement, illumination, contrast, organization, and posture as adaptations to enhance a person’s ability to function during activities of daily living. Simple, practical solutions can greatly enhance a person’s ability to perform self-care, meal preparation, functional communication and household chores.
Most people with low vision disorders are of an age when bifocal, trifocal, or multifocal lenses are prescribed on a regular basis. Wearing these lenses, however, may change a person’s posture or the way a person holds his or her head. This change in posture can lead to balance issues and fall hazards. Therefore, it may be preferred that single focal lenses are worn during ambulation, especially when the person is navigating stairs and other uneven surfaces.
- Scheiman, M. (2002). Review of basic anatomy, physiology, and development of the visual system. In M. Scheiman (Ed.)Understanding and Managing Vision Deficits: A Guide for Occupational Therapists, 2nd edition. Thorofare, NJ: SLACK.
- Zoltan, B. (2007). Vision, Perception and Cognition: A Manual for theEvaluation and Treatment of the Adult with Acquired Brain Injury, 4th edition. Thorofare, NJ: SLACK.
- Dirette, D. (2012). Low Vision Disorders. In B. Atchison and D. Dirette (Eds.) Conditions in occupational therapy: Effect on occupational performance, 4th edition. Philadelphia: Lippincott Williams & Wilkins.