Any EDTA will likely contain some formaldehyde (around 20 ppm?). If carnosine is in the same eye drop, that would be converted to methylamine, but methylamine is also toxic to the eye.
How about an alternative?
Maybe we could replace the EDTA by N-acetyl cysteine (NAC).
Like EDTA, it also has metal chelating activity so that the glutathione in the eye lens retains its photobleaching power. And to top that, NAC also generates more reduced glutathione right there in the lens - so more photobleaching power. Let's assume for a moment that NAC would do the same job as EDTA if it were "equimolar" with the missing EDTA.
The amount of EDTA in the original eye drop was around 2.5%.
EDTA has a molecular weight of around 336.
The molecular weight of NAC is around 163, i.e., about one-half that of EDTA. To be "equimolar" with the EDTA, then maybe we need to use 2.5%/2 of NAC = 1.25% of NAC (not so much, because it has a smaller molecular weight than EDTA).
So, we would have an eye drop containing:
MSM - around 5%
NAC - 1.25% (I guess 2% would cover it).
L-Carnosine - 1%
We should however keep a little EDTA just because it is a safe eye drop preservative. 0.1% of EDTA would be enough as a preservative, and at only 0.1%, any impurities in the EDTA will no longer be a concern. So, finally, we add 0.1% of pharmaceutical grade EDTA.
All of this should be made up in sterilized, distilled water.
And that is our cataract reversal eye drop. Safe, and very probably, effective.
UPDATE: Due to the risk that MSM will form more disulfide bonds with lens proteins, which we know nothing about, I decided that it may be best to use the above formula leaving the MSM out. The NAC, in addition to generating glutathione, also forms disulfide bonds with lens crystallins, but they are known to stabilize the reduced, correctly folded form of those proteins, and that is what we want. As such, the formula now resembles the commercial cataract eyedrop, "Oclumed", but without the ascorbate found in that product, and with the substitution of L-cysteine by N-acetylcysteine (NAC).
FURTHER UPDATE: I decided to replace the L-carnosine by N-acetylcarnosine (also known by the abbreviation NAC), as the acetylated form enters the eye more easily, and unlike L-carnosine, does not generate histamine.
So the final formula is now: 2% N-acetylcysteine, 1% N-acetylcarnosine and 0.1% EDTA as preservative, all in distilled water.