https://gfycat.com/IdioticEcstaticGrayreefshark

As you can see, looking at a fairy light causes weird visual errors depending on how you look at it. Lights looked at from an equal height or below will cause transparent blocks to turn white, while looking at them from above causes the whole screen to go white. Lights obscured by transparent blocks or entities do not cause this issue.
This may be an issue with Optifine, but it would be hard for me to test this as I can't run the game without Optifine installed. I've tried several settings but none of them seem to change this problem.

I've just had this issue, I'm running Optifine 1.12.2_HD_U_E2 and I will try removing Optifine and seeing if the issue persists.

Ah, I overlooked this report, but a couple days ago I did release a new version, 2.1.4 which resolves this issue.