20/70: Mildly impaired. This is the point where people really begin to feel handicapped. Reading newspapers is very difficult without magnification, and most states refuse to license persons to drive with a visual acuity this low unless they are equipped with telescopic glasses. Object and travel vision are still excellent, except for those who have lost field vision as well.
20/75 to 20/200: Moderately impaired. This group can still function as sighted in most regards with the use of low-vision aids. Object vision for this group is poorer, but it is still adequate for almost all activities. These people can see the car but may have trouble identifying its make and model. Recognizing friends may be difficult, but they see the person. Travel vision is still quite good unless there is also field vision loss.
Reading is the primary problem for this group, but good equipment and training eliminate this problem. People in this group can be equipped and trained to read using numerous low-vision aids. All members of this group should be able to drive with telescopic glasses unless there is also serious peripheral-vision loss, or other limiting factors.
20/200 to 20/800: Seriously impaired, but still with travel vision and reduced but useful object vision. People in this group can read with low-vision aids of various kinds. Those below 20/500 might consider learning Braille, but even then it certainly isn't mandatory. These people will not be able to drive, even with telescopic glasses. Object vision diminishes but is still useful. Travel vision is still adequate, although those at the lower end of the scale may sometimes trip over curbs. Crossing streets can be hazardous for people at the lower end of this scale because they cannot see distant oncoming cars.
20/800 to 20/1200: Severely impaired. At this level of visual acuity a person loses travel vision. People suffering a loss of peripheral vision may find a white cane useful or even necessary before this point is reached, but at this stage, use of the white cane becomes necessary, regardless of the cause of vision loss. Some in this group are able to use very strong magnifiers to read large print. A +50 diopter lens will give almost all in this group the ability to read textbook-size print.
20/1200 to 20/6000: Very severely impaired. Many doctors reject the use of visual acuity figures this low. While it is true that letter sizes larger than 700 do not exist on test charts, there are mathematical equivalents. Doctors categorize this level as the ability to see a hand moving one foot away, without the ability to count fingers. People in the 20/1200 to 20/6000 group are dependent on the white cane or a guide dog for independent mobility. A video visual aid for reading print is the aid of choice and the only aid that provides visual access to print. Voice synthesizers are available that convert print into speech. Persons in this group are legitimate users of such equipment.
This group has little object vision, but as long as there is any light perception, that vision is useful. For example, a man walking down the street with his white cane sees two shadows ahead. He sees light between the two objects. He probably can't tell what the objects are, but he knows there is space enough between them for him to pass through.
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