For those of you wearing bifocals.
With bifocals I found it difficult to comfortably view a PC monitor. Either too near,too far, or too low. The focus point was just wasn't there. So, I finally broke down and ordered a pair of "computer" glasses". The focal distance is
from about 8 to 32 inches.
Not only did I gain focus on the monitor but I also found that they are even more useful when peering into the aquarium.