I would like the learned men here to explain these things I am going to
report.

Now the client who is recovering from -20 D prescription by the use of
the Original Systemof Self-Treatment by Rest Methods, recorded an
experience as follows:

At 2 meters distance from the 200 feet Snellen Chart (the one with the
big 200 feet C at the top), she says that looking to the right of the C
2 meters away, so to create an angle of 45 degrees, the big C seems
MORE BLACK.

I would like the learned men to explain to me why this happens, if it
is a fact of physiological optics or just that the retina is damaged
around the macula and becomes less damaged at the periphery.

If we think that a -20 D eye is elongated at least by 6 or 7
millimeters, ad has a bulge at the back, we could say that by looking
at 45 degrees to the left or to the right, the rays of the big C fall
an the side of the retina which is LESS DISTANT from the lens, than it
is when she looks at the big C in the fovea.

So this may be a good optical explanation: the C in the eccentric field
falls on a side of the retina which is less myopic than the fovea.

Now the strange fact is that when she regards the letter B, which is
half the size of the C, and is read by the normal eye at 100 feet, she
has no need to push away her gaze at 2 meters lateral, to see it
blacker, but sensibly less distance.

How this can be explained with the laws of optics?

Furthermore,

The girl says that when she reads microscopic print at 5, 7 or 9 cm,
she has no "eccentric fixation", that is, she is able to see a little
bit better where she is looking, the tiny letter she is reading (this
letters are 1/3 of a millimiter tall).

I would kindly appreciate any comments from the learned men who are
here.

Thanks.