PAL & Astigmatism

by John
(Chicago)

Q: I've bought several pairs of PALs (Costco) and still having fuzzy read in left eye.

Previously used monovision contacts with left being distance, the right lower power for reading.

Right eye glass works perfect (minor astig -.25) but left (-1.50 astig) giving trouble at distance; reading is fine in both eyes.

I've read about adjustment period, been back to Dr and checked Rx, works fine in the office, but road signs & sharpness at distance still a problem in left eyeglass.

Difference is ever so slight but it's like the axis is not lined up or the difference with .25 to .5 diop off maybe, but again works fine in the Dr chair, lenses made correctly.

Is it due to plastic lens vs glass that's perhaps in Dr's fitter? Is it related to the PAL at all - I wouldn't think so as intermediate & reading are fine in both eyes.

Could it be Costco's base curve with my astig in left eye?
Is it related to the monovision contacts I was conditioned to and my eyes will need long adjustment?
If so why does it work immediate in Dr office?

Some times it works fine, particularly in morning but doesn't stay in focus constantly.

Full script is
R -2.25 -.25 050 +2.00
L -2.23 -1.50 170 +2.00

Using these in 1.67 also. Does material have an impact at all?


A: Hello John
To answer your questions I will take them one by one:

First, I think that the refraction should be the same with plastic or glass, I don't think there is any difference, or at least not one that you notice.

Second, the base curve of the lens is made to compensate the axis so the alignment of the axis will be correct if the lens is shaped correctly into the frame, there should be no image distortion.

I would blame the monovision because your brain got used to this and adapted to offer you the best vision. This is made by rewiring the brain to select only the best images and transmit than as they come from both eyes.

Changing this way of transmission will confuse the brain so there is an adaptation period needed to change the wiring back. The good news is that the brain is capable of handling this, but it needs time.

Hope this helps,
Arpi

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