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Make my own eye chart
#1
It wasn't until a month ago I really started to take my eyesight seriously - I'm sick of the strain everytime I close my eyes, sick of vision habits, sick of my eyesight problem (it's only in one eye but both are straining).

In reality, I would've liked to talk to a real teacher, but since I can't, I'll do things on my own.

1. I need an eye chart. I don't have the use of a decent printer unfortunately - and I can't ask anyone to print it out. Is there any way I can make my own, with usual white papers? I have a black pencil. The distance doesn't matter, if it is 10/20 feet I don't care - I just want one I can practise with. But I'm not really sure how big the letters should be.
2. It's not dangerous to look directly in the sun, is it?
3. I have a strain in especially my left eye when I close them - how can I fix this? The neck feels a bit stiff, too.
4. What is the best way to work when only one eye is effected? I think my left eye is somewhere between - 1,72 and - 2,05 - not completely sure. Myopia. My right eye is between 0,0 and 0,3 - really low numbers.
5. Is it possible to recover my old visiom, which I think was somewhere between 20/7.5 and 30/20 - more than 20/20 anyway.

Thank you!
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#2
(06-29-2015, 01:17 PM)aanddiis Wrote: It wasn't until a month ago I really started to take my eyesight seriously - I'm sick of the strain everytime I close my eyes, sick of vision habits, sick of my eyesight problem (it's only in one eye but both are straining).

In reality, I would've liked to talk to a real teacher, but since I can't, I'll do things on my own.

1. I need an eye chart. I don't have the use of a decent printer unfortunately - and I can't ask anyone to print it out. Is there any way I can make my own, with usual white papers? I have a black pencil. The distance doesn't matter, if it is 10/20 feet I don't care - I just want one I can practise with. But I'm not really sure how big the letters should be.
2. It's not dangerous to look directly in the sun, is it?
3. I have a strain in especially my left eye when I close them - how can I fix this? The neck feels a bit stiff, too.
4. What is the best way to work when only one eye is effected? I think my left eye is somewhere between - 1,72 and - 2,05 - not completely sure. Myopia. My right eye is between 0,0 and 0,3 - really low numbers.
5. Is it possible to recover my old visiom, which I think was somewhere between 20/7.5 and 30/20 - more than 20/20 anyway.

Thank you!
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1. Get creative about the eye chart. Use a calendar and don't worry about the size of numbers or distance, just put it somewhere where it's slightly blurry. Then keep moving back as it gets easier and your eyes relax. Or take a photo of an eyechart on the computer and look at it on your camera. You just want to practice looking at the details of the letters/numbers.

2. It's best to close your eyes when directly facing the sun.

3. Palming and Long Swing. Also straighten up and relax your posture.

4. Practice with the strong eye patched, then both eyes together.

5. Yes.
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#3
Hi,

I'll answer your first point. It's good that someone has asked this question about making their own eye-chart. That's a pretty nice topic.

For those who are tired of long reading - the RESUME is at point 3 and 5.

1 If you want to see only whether you're progressing you can simply draw anything you like. If you can with time increase the distance at which you see what's drawn with the same clarity - it's an obvious sign you did make a progress.
If you can see a bunch of your own icons or symbols drawn on the paper perfectly from 6 ft and after three months you can see them from 9 ft who can say you didn't make an excellent progress? Cool

2.1 But if you want to know how good your vision is in terms of standardized numbers given for vision acuity: 20/15, 20/20, 20/25...20/40....20/100 etc... in other words, to be able to say what's your vision the way the others say (eye doctors and poor fellows with spoiled vision) then you need just a little bit of mathematics. Fortunatelly, not too much. Smile

It will be easier if I use the international units.

2.2 First of all, how big is any letter on the Snellen test card for 20/20 vision seen at the distance of 6 metres (roughly 20 ft)?
The answer: it's preciselly 8.75 mm.


Now look at the Snellen test card:

https://upload.wikimedia.org/wikipedia/c..._chart.svg

What can you see?
The letters may seem a bit strange because they are inscribed in the imaginary square. The letter "O" is a circle actually and some other letters are wider than we usually write them. But they all have the SAME VISIBILITY thanks to to the fact that all of them are inscribed in the square and the lines which consitute them are of the same thickness, namely - one fifth of that square. Just look at the letters. Are all the lines (and points) one fifth of the height and width of each particular letter? Yes, they are.

Why one fifth of the height and width of the letter? Because the person who has 20/20 vision is able to distinguish two different points if each of them is not smaller than certain size. That size depends on the distance between the object and observer but the angle between the observer's eye and the lines touching margins of the point is always the same: one minute.

2.3 If you have 20/20 vision and look at anything that you can see perfectly than the smallest point clearly visible to you is the one whose margins make an angle with your eye of 1-minute value. That point obviously cannot be a letter since letters are more complex than points (obviously, hehe) but can be a point which consitute the lines which then build all the letters. The same rule applies to the spaces between the lines. If you want to see them clearly then they mustn't be smaller than one minute.

2. 4 When you analize the Snellen test chart you see that letters are well chosen (there are no "w", "m", "i" and other letters of various visibility levels) and constructed in the same way: the proportional image is a square and all the lines and points and spaces between them are of the same size in order to provide the same visibility of each letter.

2.5 Furthermore, a point whose margins make a one-minute angle with your eye at the distance of 6 m is 1.75 mm big. Since the letter is made of such points some people said: "OK, we are able to make nice readable font constisted of such points if the letters are five times bigger (strictly speaking twenty-five...)" Why five times bigger? Because, for example, the letter "E" requires so: it has three horizontal lines and two white spaces between them.
1.75x5 equals 8.75.
This is why all the letters on 20/20 lines seen at 6 metres have this width and height - 8.75 mm.

2.6 Now, if we understood this the rest is much easier.

How big are the letters on the 20/25 line seen at 6m? 25 devided with 20 equals 1.25. Next: 8.75 mm times 1.25 is 10.94 mm.
Letters on the 20/40 line seen at 6m? Double bigger than 8.75 mm which is 17.5 mm.
Letters on the 20/70 line seen at 6m? 70/20=3.5 8.75 mm x 3.5 = 30.63 mm.
Letters on the 20/16 line seen at 6m? 16/20=0.8 8.75 mm x 0.8 = 7 mm...

2.7 If you can't provide testing from 6m probably you'll like to make a chart designed for viewing at 3m. That'll make your 20/20 letters double smaller than 8.75 mm - 4.38 mm. And all other lines are then scaled to this value.

2.8 Now pay attention that the thickness of all lines and the size of points is one fifth of the height and width of the letters.
If you make a chart for viewing at the 3m-distance that means the lines and the spaces between them are only one fifth of 4.35 mm. That's only 0.87 mm. Still achievable with precise drawing but you need an eagle's eye for this. Sleepy

2.9 And instead of E, C, O, T, L, P, Z, D and F you can make your own symbols just to make it more fun.

For example, you can draw a sguare with lines one fifth of the size of the square and put a dot in the middle. And, of course - the dot is one fifth of that square. Then you can make the same square and put just one short line which goes from the middle of one side of that square till the centre of it, and i's 2/5 of the square's size in length. Then you can make four symbols of that kind just rotated for 90 degrees so that you can look at them from the distance and say how the inner line is positioned, to the left, to the right, up or down.

3.0 RESUME for folks who don't need this much details:

3.1 Your own chart designed to be viewed at the distance of 3 metre: The letters or some other symbols on the 20/20 line should be 4.35 milimetre big (width and height) and the lines and points which they are made of should be one fifth of that size (0.87 mm), as well as the minimum space between the lines and points. All other lines 20/10...20/25,20/30...20/100, 20/150...20/1000... etc are scaled regarding the 20/20 line.

3.2 The same can be said for the charts designed to be viewed at all other distances. Your orientation is the 20/20 line - 3 m - letter size 4.35 mm or 20/20 line - 6 m - letter size 8.75 mm.

3.3 You are not confined to letters, you can design your own symbols. Just follow the logic that the eye fit for 20/20 vision can distinctly see a point whose margins make an angle with the eye not smaller than one minute. After the application of some mathematics you get the size of the point seen at 6 m - 1.75 mm. All the design should have this fact in consideration.

4 I hope this helps.

5.1 This point was added a day after my initial post:

5.2 No doubt that 3 m is a nice distance for viewing but measures of the 20/20 line are pretty disagreeable for drawing: 4.35 mm for letters and 0.87 mm for their parts.

5.3 It's much easier to do this: making a chart for viewing at the distance of 3.5 m (11ft 5in). Then your 20/20 line has nice measures: 5 mm for the size of letters and 1 mm for their parts.

5.4 And then all other lines are easier for drawing:
20/10: 2.5 mm letters and 0.5 mm their parts.
20/12: 3.0 mm letters and 0.6 mm their parts.
20/16: 4.0 mm letters and 0.8 mm their parts.
20/20: 5.0 mm letters and 1.0 mm their parts
20/30: 7.5 mm letters and 1.5 mm their parts.
20/40: 10 mm letters and 2.0 mm their parts.
20/50: 12.5 mm letters and 2.5 mm their parts.
20/60: 15.0 mm letters and 3.0 mm their parts.
........
20/100: 25.0 mm letters and 5.0 mm their parts.
........
20/400: 100.0 mm letters and 20.0 mm their parts.
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