QUESTION: 'Normal' minimum focal length

Hey, all.

I am nearsighted, to the tune of 3.5, corrected by contacts. I was just
having a close look at a polished stone I bought, and observed that I
lose the ability to focus at about the 15cm mark; anything closer and I
can't focus on it. I just wondered if that was a 'normal' distance for
such a threshold? Is this distance something that one would expect to
increase with age?

Just semi-idle curiosity...

BD

 

If you are young then its good. If you are over 25 then its great! I am
23 and theres NO way I can focus to 15cm with full power contacts.
Maybe 25cm if that. My sister is only 18 so her accomodation is good,
she can focus down to 15cm. Without correction, I can focus as close as
10cm with my -4 pescription. Thats with both eyes open and crossing
them and straining. Using both eyes increases the depth of focus and
you can cross them for fusion of accomodation. However accomodative
amplitude is measured with one eye open at a time. Uncorrected I see
fine down to 15cm one eye at a time Thats 6.5 diopters of accomodation
minus the 4 diopters of myopia I have. With full power contacts id be
looking at 40cm minimum! I can not see fine print with contacts and
newspaper print is somewhat blurry unless I hold it arms length. A
slight undercorrection makes a huge difference.

 

If you are over 25 then its great!

I'm 37. Guess that's alright, then. I never made a point of seeing how
close I could get when I was younger, but I'd be surprised if I was
ever able to get much closer than that.

If only I could get rid of the damned floaters.

 

If you can still accomodate down to about 8 inches clearly, thats
better than average accomodation for a 37 year old. Maybe your contacts
slightly undercorrect? I find that as little as half diopter
undercorrection makes a significent difference in how well I see from
near. How well do you see uncorrected? corrected?

 

How well do you see uncorrected? corrected?

Corrected is _pretty_ good for me. Better with glasses. I have slight
astigmatism in my left eye, and it was decided that it was mild enough
not to sweat it in terms of the contacts. So there's a very subtle
difference between right and left with my contacts. Almost
unnoticeable. Certainly a 'hit' I'm willing to take to get off the
glasses.

I figure that if the contacts undercorrected I would experience eye
strain, which I don't.

Uncorrected is just silly. I'm useless. And I thought _my_ prescription
was strong. I have a good friend who's 9.5. Yuck.

 

9.5 is insane, much more so if contacts due to vertex distance. Your
glasses pescription should be -4.5 give or take a half diopter.
Different people appear to behaive differently in how much contact
power they need vs. glasses. I know someone that sees 20/20 with -3.5
contacts but needs -5 glasses to see perfect. I know another that needs
-4 contacts but only -4.5 in glasses. The average is 1.25 meaning you
multiply your contacts to arrive at glasses. My -3.25 contacts
multiplied by 1.25 come at about -4 in glasses(I rounded) I see MUCH
better with -3.25 contacts than -3.25 glasses and in fact theres next
to no difference between -3.25 contacts and -4.25 glasses. I know some
optometrists disagre but like I said, it depends on the person and
their eyes. You can compare glasses vs. glasses but you cant compare
contacts vs. anything as its variable on the person and their eyes.

Undercorrection isnt silly, you will understand in a few years once you
get presbyopia. Imagine not seeing clearly as much as 2 meters in
advanced presbyopia. Youll need reading glasses for everything 2 meters
and closer. Talk to someone across the table? His face will be blurry!
Try to use the computer? You wont be able to read a thing on the
screen! Newspaper? Forget it your arms arent long enough! I dont like
contacts for several reasons, one is they arent comfortable, they can
be felt. Two is I cant see clearly less than about a foot with contacts
and my eyes feel strained and ache if I do any near work with them. I
do not wish to incude more myopia that way. Three is I can just take my
glasses off and see great from near. I am happier with glasses than
contacts. Ill only wear contacts for seeing in the distance such as to
play sports.