I was wondering, recover from myopia is rarely a night-day task, unless you have very low myopia.
With that in mind it become clear to me that Snellen check is not a good measure, Snellen has letters with huge different sizes, that why ODs dont use then alone, they use a combination of the Snellen with several lens to see if the refraction error increased or not.
And theres always the squinting and blinking factor that makes us see more sharp temporarily.
The best way to measure at the Snellen is not what you see, but what you see sharply, and thats not enough to measure small progress as the difference between a letter above and below is too big to any small check.
Do you agree?
Obs: Obviously when we talk about a huge recover the Snellen can be useful to show, but you will not have feedback of your progress until it becomes reachable to the Snellen test to measure.
In my experience, the Snellen is actually the easiest and most accurate way to test the vision. It is not "see/don't see"; it's usually more of different shades of gray and varying degrees of sharpness that I notice. Of course, if one is too far away from the Snellen chart, then it can just be a blur, and that's no good at all. So it helps to be closer.
You do have a point that is worth mentioning though. The vision does vary from day to day and even from moment to moment, so it's worth remembering that you are really looking at just a snapshot of your current state of vision at any point in time.
EDIT: I should perhaps say that this is just what I have noted in my own experiences and this is just my opinion. Hopefully, others will add to or correct what I have said.
I pretty much agree with lfernand. I tend not to fully trust people's measurements of their own acuity, especially if other parts of their story cast doubt on said measurements. This doubt does not mean that I'm calling someone a liar, only that I think they're likely overestimating their improvement.
Well, obviously you have to be honest with yourself, but I don't know what better way there is to measure the eyes. It's happened to me before, so I can understand how one might be misled by the Snellen, but I don't think that this is a reason to discredit it entirely. I mean, if you're basing everything on one measurement, than obviously, the chance of your overestimating or underestimating your visual acuity goes up considerably, but if you're making many such measurements over a long time interval, and you're being fairly objective about it (I don't see why you wouldn't), then noting the trend in vision over time can be a useful tool.
In my experience, the Snellen is actually the easiest and most accurate way to test the vision. It is not "see/don't see"; it's usually more of different shades of gray and varying degrees of sharpness that I notice. Of course, if one is too far away from the Snellen chart, then it can just be a blur, and that's no good at all. So it helps to be closer.
Pikachu, you actually describe you overcome the problems I listed by having a great perception and memory of this perception, I believe is not the case for everyone.
The best way is to have a Snellen with dozens of characters, with minimum difference in size between two adjacent ones. And the task would be to see the letter sharply as possible (that involves some subjective perception too, but with a lower error margin), and not just being able to see at some point.
lfernand Wrote:With that in mind it become clear to me that Snellen check is not a good measure, Snellen has letters with huge different sizes, that why ODs dont use then alone, they use a combination of the Snellen with several lens to see if the refraction error increased or not.
ODs are mainly measuring for AIDED acuity. They have little concern for your unaided acuity. They're not in the business of changing that, because most don't believe it is changeable. So of course they are going to uses trial lenses to determine your aided acuity.
lfernand Wrote:he best way to measure at the Snellen is not what you see, but what you see sharply, and thats not enough to measure small progress as the difference between a letter above and below is too big to any small check.
Do you agree?
If you are really concerned about minute differences, why not simply stand/sit either closer for farther away from the chart, in smaller increments? One foot increments would give you 20 different measurements of a single given line. Six inch increments would give you 40 different measurements per line. Likewise, you could use a copier and enlarge or reduce your chart in 1% increments, making loads of charts that are incrementally larger or smaller. Otherwise, many different style charts and scoring methodologies have been developed since the dawn of the Snellen, which can help measure smaller increments of visual acuity (lookup the Waterloo chart, the Baily-Lovie design, the Log-MAR chart).
lfernand Wrote:Obs: Obviously when we talk about a huge recover the Snellen can be useful to show, but you will not have feedback of your progress until it becomes reachable to the Snellen test to measure.
Move it closer, until you get adequate feedback. Move it away as it gets too easy. Requirement: one simple chart.
If you can't tell whether you're making improvements or not, you're holding the chart way too far away. It's hard to make much progress when you're looking at a Snellen that's so far away that you can barely make anything out, because the strain is simply too great at that distance, and you'll unconsciously do things to cope with the strain that will prevent progress.
You should only practice with the Snellen at a distance that you see pretty well -- maybe just a little unclear;y. You should see it just poorly enough to be able to sense a little bit of anxiety, which you would greater chance of letting go of successfully. You should be able to tell within a few shifts (i.e., seconds, not minutes) whether or not you're doing the right thing because things should clear up. Practicing on a really unclear Snellen is like trying to do too much too soon and is counterproductive.
Remember, the point of the Snellen is to serve as a feedback mechanism to let you sense how you're straining (i.e., which muscles and in what direction) and to let you know whether what you're doing is correct in that it improves your vision. If you're spending tons of time and not seeing any noticeable improvements, you're wasting your time. You don't get rewarded for time investment in vision improvement, unless you're spending every second productively.
The initial post was speaking about the Snellen chart to verify recovery from myopia.
If a person has made progress he, or she should see a line clearly,and be able to discern every letter on that line consistently every day,under varying light conditions,and when rested,or fatigued,stressed,or relaxed.
Your vision should be just as it was before you became myopic.People with normal 20/20 or better vision can consistently read the 20/20 line.
Many people have been myopic for such a long time that they interrupt clear flashes as an improvement,but true improvement is reading a line clearly,and consistently that you could not read previously.
Bifocal Wrote:If a person has made progress he, or she should see a line clearly,and be able to discern every letter on that line consistently every day,under varying light conditions,and when rested,or fatigued,stressed,or relaxed.
Bifocal Wrote:but true improvement is reading a line clearly,and consistently that you could not read previously.
So you are saying that it is that black and white; there is no such thing as improvement that falls between say, blindness, and perfect clarity? If one could not initially perceive at all the 20/200 line on their chart, and then later can consistently recognize all the letters of a line, though not perfectly black and sharp, on the 20/40 line, then you are saying that is not true progress?
Did your own vision go from (X) to 0 directly, with no in between transitions, where you could clearly make out the letters, consistently, though not perfectly black and clear?
