Getting visuals while looking at a computer screen can definitely happen at small doses. You might not see any visuals looking at the space around you, but black text on a bright white screen will bring it out.

And mixing up the dosage is insanely easy with LSD, especially if you are using tabs since the LSD isn't evenly distributed throughout the paper. Also, you never really know how much LSD is on your sheet or in your vial, you just have to trust your source.