KC - Can this possibly be true?

[craigthornton]

OK 20/20 is the American version of our Snellen definition. It really means "normal vision". Our equivilent in metric is 6/6. If you get 6/5 this means you are getting one line better than accepted "normal vision" which any anyone standards is very good!


Lynn

How far down the chart are you meant to be able to read uncorrected to be classed as having normal vision?

[GarethB]

Craig,

My understanding is if you get 6/6 uncorrected you have normal vision.

Get the smae with corrected vision, then your duff vision is brought back to normal standards.

[Andrew MacLean]

That is my understanding, too. The problem from the punter's point of view is that we don't know at the outset how far down the chart (what number of lines) we have to read to make this standard. I think that some Snellen Charts have more and some have fewer lines.

But the standard is supposed to be universal. It is not the numbe of lines from the top that matters, but the size of the characters on the 6/6 line

Andrew

[Sajeev]

Going away from the "normal" sight calculations. It reminds me that I was reading, on average most people in the UK see less than 20/20, (I am not sure but my educated guess is, that's with counting all age groups). I can't remember where I read it though... it could be one of those "did you know" kind of stats which seem strange at first, but it could just be due to an increase in the aging population that numbers are getting crunched?!

[piper]

Wheras it may be THEORETICALLY POSSIBLE to grind an eyeglass lens into such a shape as to be fully corrective, any rotation or movement of the eye will then cause vilsual information to be gathered from a differfent portion of the lens than it was when looking straight forward. Therefore, any lens made will be useable in only one postion of the eye and in normal life this is simply not possible.

Specialists like this may serve to set KC care and understanding back decades......

Piper

[GarethB]

Piper,

I beg to differ in that the ability of the brain to compensate need be taken into account.

My RGP can be off by 10 degrees and I can still see down to the same level of the chart. Rotate it another 120 degrees then it moves out of position and I see nothing at all!