I wore contact lenses, hard and soft, for about 25 years until I lost my
tolerance of them. Also, the design of the contact lenses I needed (“toric”) to
correct astigmatism was complicated and required the lenses to be weighted at
the bottom to stop them rotating. That was a problem if I had to hold my head
on an angle to look at something.
There is no doubt that contact lenses are the way to go if you can manage them.
It should always be remembered, though, that putting something in the eye is a
potential health hazard but if handled properly and hygienically there is
usually no problem even if you do know when a bit of grit gets between the lens
and the eyeball.
For about the past 25 years I have worn spectacles even when birdwatching as
the better models of binoculars cater to a fair degree for spectacle wearers.
The only real problem is the possibility of reduced field of view because of
the distance the eyeball is from the rear lens element of the binos. Once
again, good binos are less of a problem there but the roof prism binoculars
favoured my many birdwatchers, including myself, have relatively narrow fields
of view so any further reduction can be a handicap.
For my eyesight I have to use multifocal (aka varifocal/progressive/graduated)
lens spectacles to cater for all distances, although, with age the distance
vision is not so bad, if it wasn’t for the astigmatism, that is. I currently
have 4 different sets of multifocal spectacles.
One set is used mainly for general purpose stuff;
One set is used for birdwatching;
One set is used for driving;
One set is used at the computer.
The general purpose (GP) set was made in the ‘normal’ style and fitted to
relatively “stylish” frames. The zones of focus are as recommended for ‘normal’
situations.
Roughly equal amounts of the lens area are assigned to each zone. This brings
up one major problem with the modern fashion of very narrow (top to bottom)
lenses in spectacles. Because the transitions from zone to zone are ‘gradual’
there needs to be enough space assigned to each zone to ensure that a fair area
of what you are looking at is in focus. As it is, multifocal lenses require the
wearer to moves his/her head up and down more than wearers of single focus
lenses. Also, the total usable area of the lens is roughly in the shape of a
figure 8 with a large segment at the top and a smaller segment at the bottom
which means that the edges of the centre part of the lens (middle distance
vision) are not ‘ground’ to correct the vision. This means that wearers of
multifocal lenses often need to turn their heads from side to side to keep
things in focus rather than simply moving the eyeballs sideways. The ideal lens
for multifocal spectacles is quite large but nobody wants to wear that style of
spectacles these days.
My birdwatching spectacles have been designed, at my request, to have larger
lenses overall with larger far and middle distance zones and a smaller near
distance zone sufficient to enable me to read a field guide but that does
require tilting my head up slightly more than is needed with the GP spectacles.
The larger lenses combined with the larger far and mid zones allow me to turn
my eyes sideways more without moving my head which, surprisingly, can be
advantageous when looking through binoculars. The only real problem with my
birdwatching spectacles is that they are susceptible to scratching if grit gets
on the bino eyecups.
The driving spectacles are similar to the birdwatching ones but with lenses
similar in size to the GP set. One difference is that the area of the near
vision zone is set lower low and is smaller basically allowing me to read the
car’s dash instruments or a map.
Those spectacles use high quality wrap-round sunglasses frames and have much
smaller lenses and, thus, smaller zones than the birdwatching set making them
somewhat usable for birdwatching with binos but nowhere near as convenient as
the birdwatching set.
The computer spectacles are a new acquisition and are designed to cater only
for a very limited focal range, about a metre, but with a large, wide zone for
the critical distance. They are a number of magnitudes better for computer work
than my GP spectacles but would be useless for birdwatching. They are good
reading glasses and when I forget to change to my GP glasses when I leave the
computer my distance vision is similar to when I am not wearing glasses at all.
I have never tried simple magnifying spectacles for birdwatching as they would
not correct my vision defects and I don’t see the point of using that sort of
spectacle with binoculars.
I would also be very wary of using glass lenses in any situation other than for
reading in a controlled environment.
Incidentally, I have never had any problems wearing multifocal spectacles while
using my cameras. It doesn’t seem to matter which zone of the glasses I put up
to viewfinder but I probably am mostly using the middle distance zone.
Bob Inglis
Sandstone Point
Qld
http://www.photos-n-guides.com/
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