by Philip C Hessburg MD
Well, literally, total loss of all light perception is absolute blindness. That patient would have no perception of light, would not know whether the sun has come up. Fortunately, perhaps as few as 10 or 15% of all people who qualify as “blind” are absolutely blind The rest have levels of sight which range from the ability to perceive light up to levels which would qualify as “legally blind”.
Legal blindness, that level which would qualify the patient for social and government purposes and benefits as “blind”, is usually determined to be 20/200 or below. With that level of vision a person may not be able to read, or drive, or recognize faces very well, but can still get around the house and in society at a level which many folks would not immediately recognize as “that person is blind”. Most patients at that level of vision, that is who are legally blind, do not usually need or use a white cane or a leader dog. This includes, at least in my experience, most patients with far advanced macular degeneration.
Thus, it is important for people with macular degeneration to know that this disease does not result in absolute blindness. At its most profound state, and with modern medical management today this is increasingly rare, age related macular degeneration knocks out the central vision, (that from the macula or center of the retina), and the patient retains peripheral or “side vision”.
If one thinks of this in terms of letters on the eye chart on the wall, macular degeneration may knock vision down to 20/300 or even lower but never cause total loss of vision. (20/300 would mean that this patient would have to walk up to within 20 feet of the chart on the wall to read what the normal person could read from three hundred feet.)
So, in summary , though age related macular degeneration remains a very serious problem, it is increasingly manageable by our gifted ophthalmologists who specialize in retinal diseases. And, unless the patient is also afflicted with some other concurrent serious eye problem (such as glaucoma) the patient will not go totally blind.