Eye test charts

[John Smith]

Just a quick note to let people know that I've updated the Snellen chart section of the web site. There is now a printable A4 Snellen chart, designed to be viewed from 3 metres - so you should be able to find somewhere to put it!

It obviously does not replace a visit to an optician, but it should help you to track day-to-day changes in your vision.

The online-viewable chart (which is not calibrated in any way) is still there, too!

[Rob Armstrong]

Hi John, just downloaded it to replace the one I created totally unscientifically a few years ago.

But I noticed it doesn't quite match the description on the page though, the page mentions a red and green arrow to mark certain lines and that it's labelled in 6/x format down one side and 20/x down the other - but the .pdf I downloaded is slightly different.

I can always add the arrows and larger 6/x values myself before I print it, not a problem, but thought other people might be a bit disappointed as for me the arrows and 6/x format labelling were the key interest.

Rob.

[Andrew MacLean]

Thanks John

Andrew

[John Smith]

Oh dear, Rob is partially correct!

The PDF file of the printable snellen chart looks fine on-screen, but reverts to imperial numbers when printed! The joys of PDF!

For reference then (until I can correct the problem), the lines on the chart should read:

1. 6/60
2. 6/30
3. 6/20
4. 6/15
5. 6/12 (Green arrows)
6. 6/9
7. 6/6 (Red arrows)
8. 6/4.5

[Rob Armstrong]

I just thought that the new version hadn't been linked yet or the wrong file was linked.

I haven't printed it yet, just opened it in Preview.app after downloading. I take it the file shows up OK in Acrobat Reader?

Having read your post I opened it in Photoshop where it displays correctly!

Thinking it might be something to do with visible layers versus printable layers I tried to open it with CorelDraw, which simply reports that the file is corrupted!? hmmm.

[Louise Pembroke]

I was thinking of creating a whole new eye chart with little pictures of different chocolate bars instead of letters and each one we got right we result in receiving a bar of the seen chocolate [Mars, Twix, etc]

[Rob Armstrong]

When I was being assessed once I informed the doctor performing the assessment that I had noticed on the way in that the chart was the same one as at the hospital and maybe he should change it in the interest of making it a fair assessment (because over the years I had learned the first 6 lines off by heart during lens fittings!).

Anyway, he ordered me to the far corner of the room and flipped the chart - testing my worst eye first. He seemed to get slightly annoyed as I said "B" repeatedly for the first line, I was at a loss as to what else it could be! He gave up on that and told me to switch eyes... An 8!?! Numbers!?! That was a new one on me!

Rob.

[Louise Pembroke]

I do find it interesting that when my good eye is tested through various aids I can see parts of the letter. Take for instance 'E'. I might see the 3 horizontal lines but not the vertical line, but mistake it for a 'B'. I'm guessing it's a 'B' even though I can't see the straight vertical line. Or, letters can look like it's been written in ink then smudged. It's not a straightfoward seeing or not seeing it. Can anyone explain this to me, perhaps one of the Optoms?

[John Smith]

Yes, I get that too! The only explanation I could find about it was the angle of asygmatism. Try this:


So now you have a picture of what looks like the iris of the eye. Get back far enough so you can still make out most of the lines with your glasses/contacts off.

Okay. Look at the lines near the center. What do you notice? If you are astigmatic you will notice that some of the lines are darker in some directions than others. Get used to the wheel for a little while and experiment with it. Try tilting your head or looking at it sideways. Try looking around the inner or outer circle. Try just staring blankly past the wheel. Notice what happens in each case. Try blinking or yawning. Try palming for a minute or two. Try covering each eye with a hand quickly to see what the difference is between your eyes.

If you a "typical" astigmatic, you may see the lines near the horizontal are clearer and darker than the lines vertically. You may also find the lines near the horizontal are spaced further apart and the vertical spaced closer together. You might also find the inner circle in not quite round.

Try looking at it with your glasses on. If your glasses fully correct astigmatism, then all the lines should be the same darkness and distance apart. If your glasses do not correct the astigmatism properly than you will still see some lines darker than others.

(Taken from i-see.org)

[Louise Pembroke]

I will check that out John thanks, it's quite hypnotic that yellow circle are you sure you're not trying to do a Paul Mckenna on me?!
{just make sure it's not embarassing please..]