🚀 go-pugleaf

"Dick Dead-Eye" <anonymouse@rodent.mx> wrote in message 
news:4313603B.3070305@rodent.mx...
 snip

<Then, last Feb ('04), another episode started, this time to the point of
causing some mild inflammation:  The distant "wall chart" vision
remained relatively close to 20/20, but I needed a magnifying glass to
be able to read even regular newspaper size print!>

How old are you?  It is normal to start to have trouble with fine print 
sometime between the ages of 38 and 45.

snip

<The recent eyeglass history for my left eye is so:

(Sph = "Sphere", Cyl = "Cylinder", Axs = "Axis";
  Adj.Sph, Adj.Cyl = Adjusted Sph, Cyl = Sph/Cyl + Add)

Year    Sph     Cyl    Axs    Add
====   =====   =====   ===   =====
1988?  -0.25   +2.75    80    ---
1990   -3.00   +4.00    85    ---    Adj.Sph   Adj.Cyl
2002   -2.00   +3.00    80    ---    =======   =======
2004   -2.00   +3.00    85   +1.25    -0.75     +4.25
2005   -2.00   +3.00    85   +1.75    -0.25     +4.75

The vision didn't really change between 1988-90, it was just that, until
the right eye went down the tubes, I had used my eyes complementarily:
My (then) "bad" (left) eye was used for close-up vision and the (then)
"good" (right) eye was used for distance>

snip


<With all that said, here is the $50 question:  Is there such a thing as
"dual focus"?
In other words, could my distance vision be both -2.00/+3.00 *AND* about
-0.25/+2.75, with perhaps some tweaking of the Cyl and/or Axs?
It was during the time I had my order in for my first pair of bifocals
last summer, that I tried on all of my old glasses and found that my
"1988" pair seemed perfect for reading--and not half bad for distance!>

snip

<Can the Cyl and Axs have two different values for bifocals or does the
bifocal and rest of the glass have to have the same values?>

No, you can't have two distance prescriptions and yes, the bifocals cyl and 
axis is the same in the top and bottom of the glasses.  However, by twisting 
and tipping the glasses you change the effective power and axis.  If you 
have progressives, there is induced cyl at various points in the lens 
outside the normal viewing area and by twisting, tipping and reversing the 
glasses you may well find an area that corresponds somewhat to your 
prescription.

The reason you can see (sort of) in the distance  with your old near glasses 
is your large amount of astigmatism.  In one meridan your current distance 
prescription for  is -2.00 and in the other meridian it is +1.00, and the 
equivalent sphere is -0.50.   Your current near presciption is -0.25 in one 
meridan and +2.75 in the other, equivalent sphere is +1.25.  Your 1988 near 
glasses prescription is  -0.25 in one meridan and +2.50 in the other, 
equivalent sphere is +1.00, virtually the same as required for near.   You 
can also see that the -0.25 meridian is not far off from the +1.00 you need 
at distance, so by twisting an angling the glasses you could see at 
distance, although a little blurry.

Looking at the equivalent spheres (your prescription if the astigmatism was 
not in the glasses and refraction was done using only spherical lenses) 
tells the tale:  your distance ES is -0.50 and the old glasses provide 
+1.00, so you would see about well in the distance with those near glasses 
as a 1.00 to150 myope would:  somewhat blurry but tolerable.

Dr Judy