That actually works now 
The way it stands right now, and this is just a general test until we can tweak it.
Assume Average Eyesight range to be 30 tiles away from the player.
Regular Zombie
20 tile range(Slightly degraded vision)
Fresh Zombie
30 tiles(Same as Human)
Brute Zombie
20 tiles(Because it helps with balance)
Decayed Zombie
10 tile range(Extremely decayed eyeballs)
Soldier Zombie
10 tile range(Riot gear reduces vision)
Scientist Zombie
40 tiles(Sharper senses)
Wolves Dogs and cats, cougars
40 tiles(Animal Senses)
There are others I added in, but testing will tell if I should reduce it or not.
Dont forget when testing, Zombies CAN track still by sound and scent. So even if they cant see you, they will move towards you sometimes because of other factors.
Also, Light level affects this. If its completely dark, they cant see crap if they already had a 10 tile vision, except what is right in their face about 5 feet away.