Transcript Chapter 3
CHAPTER 3 Low Vision for O&M What is Low Vision? Definition has changed over the years According to Foundation of Orientation and Mobility: “…persons with usable visio that is not fully correctable by standard eyeglasses, who experience difficulty performing visual tasks for the purupose of mobility.” They fall somewhere between fully sighted and total blindness History of Low Vision Legally Blind (20/200 or worse) until late 1960s Dr. Natalie Barraga challenged the concept of “sight saving” 1964 First national low vision mobility conference 1971 First course in low vision was required by Western Michigan University’s professional prep program. Within 10 years all universities followed suit Increase in low vision research 1980s and early 1990s Common Functional mobility problems for students with low vision Lighting and glare Adaptation, Changes in terrain and elevation Unwanted contacts with obstacles Head night lighting, height and low-lying objects Street crossings Judging cross speed and distance, determining time to Optical Devices for Mobility Reverse telescopes and Fresnel prisms may assist students with severely restricted fields. Driving with low vision is possible in many states. O&M teaches use of bioptics, NOT driving skills. Electronic travel aids for low vision are still being developed. Head mounted displays are at the forefront of this technology. Telescopes 2 types of Telescopes: Galilean – plus lens and minus lens with space between Keplerian – series of lenses with high amount of maginification Advantage: Large field of view Disadvantage: Only goes up to 3x Advantage – up to 10x Disadvantage – higher cost Improve magnification while reducing visual field Typically reduce light entering the eye (this can be good or bad!) Most telescopes sold today have the ability to focus at close range Advantages: small, lightweight and cosmetically appealling Field Enhancement Devices Reverse Telescopes (that peep-hole in your door!) Handheld minus lens Fresnel prisms Series of prisms compressed into a transparent, thin, plastic membrane Can be placed in lenses to see objects at approximately 80 degrees to the side Addressing Low Vision Evaluations on students with low vision must be done in a variety of settings during, different times of day, under different lighting conditions, etc. Significant difference between reduced acuity and reduced fields. Telescopes can assist students with orientation by improving distance visual acuity for spotting purposes. Non-optical devices can help control illumination Chapter 6 - Psychosocial Dimensions of O&M Tuttle & Tuttle (2004) describe the 7 stages of adjustment to visual impairment: Trauma Shock & Denial Mourning and Withdrawal Succumbing and Depression Reassessment and Reaffirmation Coping and Mobilization Self-Acceptance and Self-Esteem A student’s outcome expectations are likely to effect his/her motivation in O&M. O&M’s need to be ready to help clients deal with uninformed attitudes of general public & families.