There is a way, though I've never used it so you may have to get a little bit creative about it yourself.
There is a tech/upgrade. Change "Data - Effect" to "Sight Range Bonus", play with the numbers a bit (can't tell exactly how it works, though).
However do note that techs are irreversible. You can't change sight range back and forth. At most, you can only create new tech/new level of tech that decreases the range, but you will still be limited by the amount of techs/tech levels.