Please explain how glasses are graded.?!
Question: Please explain how glasses are graded!.!?
I understand from searching on the internet that they are negative if one is short sighted, and positive if one is long sighted, but what do the numbers mean!? How short sighted is someone with "-1" very or not very!? What does the 1 mean!?
Many thanks!.Www@Answer-Health@Com
Many thanks!.Www@Answer-Health@Com
Answers:
A person who is -1!.00 D can see perfectly clearly up to 1 meter only!.
Another person with -2!.50 D can see perfectly clearly up to only 1/4 of a meter!. Get it!.
So how far can a person of -!.25 D see!?
Ans!. 4 meters
For long sighted persons it is a little more complicated!.
A long sighted or hyperopic person can see perfectly both near and distant!.
Young people with + !.50 or + 1!.00 or +2!.00 can see perfectly well for all distances whereas people who wear minus cannot!.
Not many people giving answers in this section understand this!.
People who write physiology books also do not get it!.Www@Answer-Health@Com
Another person with -2!.50 D can see perfectly clearly up to only 1/4 of a meter!. Get it!.
So how far can a person of -!.25 D see!?
Ans!. 4 meters
For long sighted persons it is a little more complicated!.
A long sighted or hyperopic person can see perfectly both near and distant!.
Young people with + !.50 or + 1!.00 or +2!.00 can see perfectly well for all distances whereas people who wear minus cannot!.
Not many people giving answers in this section understand this!.
People who write physiology books also do not get it!.Www@Answer-Health@Com
The numbers are diopters!. The diopter number of a lens is the reciprocal of its focal length in meters!.Www@Answer-Health@Com
-1 is not bad
my husband is -7!.5 (virtually blind)Www@Answer-Health@Com
my husband is -7!.5 (virtually blind)Www@Answer-Health@Com