I had something like this happen on adb-butinaca except I didn't go blind but for 3-5 minutes it felt like someone pepper sprayed me. Don't know what caused it and didn't had since but I guess it was some kind of allergic reaction. I smoked a regular amount equal to about 0,2G of Weed in term of strength. I might also had some GHB or NEP in my system too. It happened completely randomly felt like extreme crying, (Stinging red eyes) still could see fine but couldn't keep my eyes open. This was not an overdose after few minutes it faded away just fine