Hi, this question is probably for the opticians out there. I recently
picked up my Hoya 1.71 glasses and found that one lens was a little
thicker than the other. My eyes are actually the same power and the
pd is 32/32 (even). I went back and the guy told me that the center
thickness is 1.0 on the right and 1.3 mm on the left. He said that is
within the tolerance of making lenses. Is this right? How could they
be the same power with differing center thickness? Would that mean
that the curvature of the lenses are different?
Any help is appreciated.
Bill
22
Jun
differing center thickness in Hoya 1.71
> My eyes are actually the same power and the
>pd is 32/32 (even). I went back and the guy told me that the center
>thickness is 1.0 on the right and 1.3 mm on the left.
There are no such thing as a "tolerance" per se, when dealing in high index
…one other thing is that you say the RX is the same 
materials other than the thinnest you should take it on recommendation from the
factory…
The only other tolerances we have to adhere to is the Ansi standard and
most of that under z.87 has to do with safety thickness and things like that,
other than that being to thin or thick will have a bearing on the power but as
far as a "book" of rules?.. does not exist
As far as your thickness being 1.0 and 1.3 and you noticed a difference…I
would think it is NOT the thickness but the bevel placement that you picked up
on..one lens the bevel maybe slightly more forward and more lens sticks out the
front or back of the frame… that 3/10′s of one mm is about as thick as a
business card which you should not be able to tell..if you can spot as little
as 3/10′s of ONE mm than I would think that you did not need glasses that
warrant a 1.71 index
in both eyes… do you have cylinder that is the same but the axis is
different? … you can have the same exact sphere power, same amount of
cylinder but have an axis that is 90 degrees apart from OS to OD and it will
change the shape of the lens, and it would appear as one being thicker than the
other
Look at the front of the frame if you do not have cylinder and axis
difference and see if the SAME amount of lens is sticking out of the front..or
if both is even with the frame etc., etc…I wouldn’t think that the CT is the
problem here with it being only 3/10′s of a mm ….
Jeff