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, night lighting,

Changes in terrain and elevation Unwanted contacts with obstacles

Head height and low-lying objects Street crossings

Judging speed and distance, determining time to cross

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

Advantage: Large field of view Disadvantage: Only goes up to 3x

Keplerian – series of lenses with high amount of maginification 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.