Myopia reversal in adults?

The last time I went to the optometrist, I complained of intermittent blurry vision. I was expecting to need stronger lenses, but it turned out that the prescription I had been wearing my whole adult life was now too strong. My left eye went from -5.5 to -5 and my right from -4.5 to -4.25. I've never thought that such a thing was possible, as my experience in childhood had always been with progressively stronger glasses. Myopia is caused by an elongated eyeball, which places the focal plane in front of the retina like this:

I did find a study in which old eyes were found to be shorter than young eyes. Here is the relevant graph (the age range on the x-axis is 5 to 55):

This is really interesting and leads to the question of what that half millimeter means in terms of glasses prescription.  If this shortening of the adult eyeball could be encouraged to continue far enough, you could theoretically cure myopia in an adult.

I found a study that measured the relationship between eye length and diopter, albeit for fewer eyes than I would like. But it's better than nothing.  If you graph out their data, here is what you get:

So that's 0.45 mm (or 450 microns) of extra eye length for each diopter. Note that obviously eye length is not the only factor controlling one's prescription. There is a cornea and lens in there that can vary in how much they bend light, for example.  But it appears that the shortening of the eye with age equals about one diopter of correction.  This study found 0.38 mm per diopter, so that's in the same ballpark. 

It's worth mentioning that not all diopters are the same in terms of their effect on your vision.  Diopters are inverse meters of your far point, the farthest point in which your vision is clear without lenses.  So if you can see 1 meter out but no farther, that's -1D.  If you can see 0.5 meters out, that's -2D.  Here it is graphed out:

So going from -1D to -2D would have a much more dramatic effect on how far you could see without lenses than would going from -5D to -6D. But I digress.

At this point it seems reasonable that my vision improvement could be due to actual shortening of my eye.  I'm 43 and therefore on the part of the graph where the eye has shortened. 

The reason for adult eye shortening proposed by the authors of the study is that the lens and cornea actually get thicker over time and therefore increase the power of the eye itself by more than a diopter.  This is essentially like wearing reading glasses and effectively reduces the strength of your negative diopter glasses, requiring your eye to shorten to maintain the same prescription throughout adulthood.  The x-axis here is again age 5 to 55. 

The weird thing here is that if this explanation is true, the mechanism to maintain proper eye length that is broken in young myopic eyes starts working properly in adulthood. However, a major weakness of the study is that it is not longitudinal.  They are looking at groups of people of different ages at a given point in time, not the same people over decades.  

I did find one longitudinal study showing that both myopic and normal adult eyes can shorten in response to positive lenses.  Unfortunately the time frame was only over 60 minutes, but it's still a very interesting study.  15 myopes and 15 emmetropes (with normal eyes, not near or far-sighted) were given +3D lenses over one eye.  That means if you have -3D, you go without a corrective lens.  If you have -4D you get -1D, and so on.  That eye will therefore be really blurry. They watched TV at 6 meters distance for 60 min.  After that time their eye length was compared to their initial length and to the other eye that didn't get the +3D.  The average shortening was 13 microns, or 0.013 mm. 

Thirteen microns is not much (roughly 1/30 of a diopter) but an hour is also not very long. And there was no difference in the shortening of the eyes of myopes vs those without myopia. The shortening was due to a thickening of the vascular choroid layer behind the retina, and so it's easy to imagine a mechanism for the shortening.  The blood vessels dilate and the retina is pushed forward toward the focal plane.  This might also explain the correlation between myopia and retinal detachment.  If the way the retina is lengthening is by thinning the vascular layer, that's not great for retinal health.  Retina is basically neural tissue and neurons need lots of blood.  As you can see from the graph above, they also tried -3D lenses (which would over-correct myopia) and found that the eyes elongated and the choroid layers thinned, although the effect was not as great as for the shortening/thickening.

Now, upon reading these results, I did what you might suspect a scientist would do. I went to Walmart, bought some reading glasses, and experimented on myself.  A +3 lens over my contact lenses was so strong that I could not comfortably read, so I went with +2.5 for reading and +1.25 for distance.  I printed an eye chart with the big E, put it up in the hallway with the tape on the floor for the proper distance, and determined that I could see 20/25 with my contact lenses alone. After a few hours reading with the +2.5 lenses over my contacts, I could see in the distance much more clearly (with contacts alone, of course).  It's probably better than 20/20, but that's as far as the chart goes. 

After a week of +2.5 for close work and +1.25 distance over contacts, my right eye could see 20/20 with the +1.25 lenses, so basically going from -4.25 to -3 diopters.  That seems like a big jump, but it's been two years since I went to the optometrist and my eyes might have continued to shorten over that time.  My left eye (prescribed -5D) has made less progress.  It can't see clearly with the +1.25 over the contacts, but it can see 20/20 with the -4.25 D contacts that I normally use in my right eye.  

So at this point, that's about 1.25 diopters improvement on the right eye and 0.75 in the left.  

I ordered glasses that are the optical equivalent of wearing the reading glasses over contacts, and they just came in this week, so the experiment continues.  It's not practical to wear lenses 2.5 D weaker than my regular prescription all the time, but they are fine for looking at books and screens.  The other pair for distance vision is only 0.75 off my regular prescription because I ordered them before I knew my right eye was going to change so quickly.  So I've also ordered one that is 1.5 D weaker, but it has not come in yet. If anyone out there wants cheap glasses without a prescription, Zenni optical and Eye Buy Direct have options under $10. 

There are anecdotal reports online of people who claim to have reduced or eliminated their myopia, but some of them are also clearly selling something, so there's a conflict of interest.  And they tend not to take a very scientific approach.  I'm still skeptical that myopia can be completely reversed.  But it's at least plausible given the science, and a pretty interesting experiment to run on myself.  Stay tuned for updates.