Re: An eyes exam

[John Clement <clement@HAL-PC.ORG>]

Actually I discovered this in the early 60s by self testing my eyes with a
wall mounted eye chart.  At that time I had better than 20/20 and it
improved to around 20/10 on the chart.  I suspected, and still suspect that
in my case part of the improvement is due to canceling out some of the
effects of astigmatism.  Since each eye has a dramatically different
astigmatic correction, this is a distinct possibility.  Now with a bit of
presbyopia I find that my 2 eyes focus at slightly different distances, but
the astigmatism produces a broader range of focus.  Both eyes have
noticeably better focus than either one alone.  I believe in my case that
the improvement may have been a couple of lines or so.

Incidentally the presbyopia caused the 2 eyes to fail to work together as
well.  As a result I had to get glasses when some music I was attempting to
read popped in and out of focus.

I am surprised that the effect was discovered only in the 90s.  I suspect
that there are probably prior reported observations about the effect, but
not necessarily with the degree of precision of the more recent findings.
Probably the early writings about this effect have been overlooked because
they are not in the medical journals.  Maybe someone on this list has come
across an autobiography or the writings of an older scientist who noticed
this effect.  I would not be at all surprised if Ben Franklin had written
about it.

John M. Clement
Houston, TX

> At 04:03 PM 12/29/01, you wrote:
> > During an eyes exam I recognized all letters in the first three
> > rows with the left eye but not the letters in the fourth row. The
> > same happened with my right eye. But all letters in the fourth
> > row became clearly recognizable when both eyes were open.
> > The doctor said that this is the synergetic (sp?) effect. I am
> > trying to reproduce this at home but it is not as dramatic as in
> > his office. Perhaps this strange effect is font-dependent or
> > illumination-dependent. Any comments?
> >  Ludwik Kowalski
>
>
> This URL leads one to expect an 11% or  a half  line improvement
> on a visual chart on average for binocular versus monocular testing.
>
> <http://www.lighthouse.org/research_acuity.htm>
>
>
> Brian Whatcott
>    Altus OK                      Eureka!