Starting about 18 months ago, I had trabeculectomies for both eyes. The
surgery seems to be successful because pressure is down to about ten
torr in each eye. Nevertheless there has been some further visual
deterioration. I was prescribed Xalatan drops again. It strikes me that
that is some grasping at straws. Maybe someone here can makes some sense
for this approach.

One of my complaints has been that that I have too much light
scattering. I was told that that glare is a common complaint of glaucoma
sufferers. I notice that my vision improves somewhat if I shield my eyes
from ambient light. I am not talking about using pinholes. I have
previously been told that I do not have much internal scattering. Optic
nerve damage was the cause.

I was trying to figure out, with my limited knowledge, how that could
be. The only thing I could think of is that there is demyelination in
the optic nerve causing "crosstalk" among the nerve fibers.

So, the main question I am asking for now is: What is the mechanism by
which glare is generated in an eyw that has lost significant vision from
glaucom?

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As the years go by, dying just before having to fill out a tax return has merit.

There is a merit to to your question re glaucoma and glare, but I have
no information or answer to offer.

There is a merit to your comment about dying before filing tax
return.  I will remember it before I die.

Light can easily get through the iridectomy hole, depending where it is made
and the size. The upper eyelid may not be covering the hole.

Is there less glare if you slightly squint the lid down on the iris, yet not
cover the pupil?

This is generally best handled with sunglasses.

I am not addressing other causes that you postulated, as I have never heard
of that as a reason.

I did notice that contrast improved if I used my hands to form an
eyeshade to block out ambient light.

Since reading your post I made the following observations.

1.  I switched my computer display from white text on black background
(inverse video) to black text on white background.

2.  As expected, the changeover greatly reduced the contrast by lighting
up the black text.

3.  I used my forefinger to block off my pupil area by moving it across
the line-of-sight in various directions.

4. With my finger vertical, I moved it from my nose (my right eye is the
better one) toward the right to block out more and more of the screen.
It seemed that contrast improved as the pupil was blocked off. This
improvement extended far away from what was blocked off. The improvement
was noticeable but not truly dramatic. It was far enough away from the
blockage so I am pretty sure it is not a "pinhole" effect.

5.  I tried the same with various orientations of my finger. My guess is
that the optimum orientation was pointing to 11 o'clock. This would
place the iridectomy at about 8 o'clock from my point of view.

As a result, I will have a new hobby trying to glean as much information
as I can from simple tests. I will also see if I can see any evidence of
iridectomy in a mirror. It has not been obvious to me so far.

I am not stupid so I resent the typical mushroom treatment I get from
physicians. Although Medicare and supplementary insurance covers my
basic medical needs, I am willing to pay out of pocket for extra quality
time with competent physicians. I get the impression that that is not
legally possible with physicians who accept Medicare. I have not really
been able to broach the subject in a meaningful way.

I would guess, without real knowledge, that I should be able to get an
hour of time for somewhere between $300-500. Correct me if I am wrong.

Bill

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As the years go by, dying just before having to fill out a tax return has merit.