As this is my first post in this forum, I will introduce myself. I'm 22 years old, have been wearing glasses about 15 years. I'm using computer most of the day (10-15h). My contact lenses are -6.00 diopters strong and my glasses, if I'm not mistaken, -6.50
I haven't yet decided if I'm going to use reduced prescription glasses or drop them entirely...
If I drop them entirely I think I will strain using computer or doing university related things (I'm studying IT), we don't want that. I guess I have to try first.
Anyway, even if I decide to use reduced prescription glasses, I need to know my current visual acuity. So, I need to print one of those Snellen charts. Which one would you suggest? (I found one, but I can't post it here because I don't have permissions...)
Last thing - so I put it on the wall and stand as close as I need to see at least that big "E" quite clearly?
OK, here is my visual acuity results using Snellen chart:
50cm (1.65 ft): I can tell quite convincingly what letters consists from line 20/200 to 20/70. In next two lines - 20/50 & 20/40 - also can tell which letters there are (blur increases). Anything below is just blur.
90cm (3 ft): I definitely see 20/200 line. Line 20/100 is still visible, although blur increases. From line 20/70 I see something, maybe can guess what letters there are. Anything below is pure blur.
120cm (4 ft): I see 20/200. Also 20/100, but blur is getting quite big. Anything below pure blur.
150cm (5 ft): I see 20/200 (there is blur, but I can definitely tell that there is E). Anything below is pure blur.[/list:u]
So what is my acuity for the moment without glasses?! Is it 5/200 or in other words 20/800?
Please comment, I want to be sure I understood correctly how to determine acuity of my eyesight!
Two things, first, good job deciding to improve your vision! Second, you're just getting comments now, because for some reason first posts seem to take a day or two before they can be read.
Now, onto your question. First, as long as the chart is marked for what distance it should be viewed at which is the first number before the slash, as well as unit of measurement (6/6, 20/20, 10/10 etc and metric or imperial), and the distance which is considered normal (the second number being the same as the first), then the chart is fine to use. Now, for the degree of myopia both of us have, getting a chart with large enough lettering for practical purposes is challenging.
Theoretically if you can see the 20/20 line at 10 feet (or 6/6 line at 3 meters), that would equate to 20/40 (or 6/12). However, unfortunately, that is not always so. It is usually actually worse than that would be. I don't know the specifics behind it, but that is the case nonetheless. So, for instance if I can see the 20/30 line at 3 feet, then 20/3=6.67, so 30*6.67=200.1, and it is actually more like 20/210, so it's close, but not always exact. So remember that first.
Second, if you are going to reduce the prescription, standing at the set distance away (measure precisely) use your glasses (or contacts if they are currently in your eyes) and see what you can see with them. If using the 20 foot chart, is it the 20/20 line, or the 20/15, or just barely one of them, or what? If you know what you are corrected to, then you can calculate what prescription to get. That's what I would start with.
FIAT2LUX Wrote:First, as long as the chart is marked for what distance it should be viewed..., then the chart is fine to use.
I have spend few days in forums before I registered, and if I'm not wrong, it doesn't matter for what distance chart is designed (Aren't like 95% Snellen charts made for 20 ft (6m) distance anyway?!)
I already have quite big problems seeing 20/200 (big E) @ 5 ft. What will I see at 10 ft or 20 ft? Absolutely nothing!
Nancy Wrote:I agree. Standing close enough to the snellen so I could see the top rows without straining was huge for me, and helped me realize the difference when I looked at a lower row with strain. I used to strain all the time! Recognizing this was quite humbling, but a necessary step to moving forward.
sorrisiblue Wrote:Often, people stand in front of the chart and strain to see. That is a demonstration of what not to do. ... As both Nancy and AndreaMajor point out, and I'll reiterate, myopes need to stand closer, often times closer than 5 feet in the beginning! You should be able to easily read a few lines. Use those as optimums and practice briefly on the lower ones, looking up at the 'easy' ones now and then to relax. Pretty soon the smaller letters become optimums as well, and are easier to see. Then you can take a step back!
I understand that you've already spent a few days in the forums, but there seems to be something quirky with first posts that the posts don't get seen for a while. What you quoted is what I mean by shifting. For "using" the chart, you're fine, I'm just saying for testing your vision that it will be complicated right now. But, even then, you can still track improvement. Sorry it took so many words to get my point across, and yes most charts are 20/20 or 6/6.
20/20 line is 3/4 inch high if I can remember. If you print a chart and the letters are a bit smaller, thats good; when you clear a line you will actually be seeing better than that line.
If you can see certain lines of letters clear, and can make determine other lines below even if blurry; work on the blurry lines with The Bates Mehtod; shifitng...
You might surprise yourself and clear those lines.
Vision fluxuates; eye doctors often over prescribe lenses, too strong. That maintains, increases the blur.
No contacts; the eyes cornea can change shape on its own and Natural Eyesight practice can change the eye, corneas shape back to normal. The contacts wont fit the eye and can scrape, injure the cornea.
