What if you replaced all cones with rods?

[whswhs]

Originally Posted by sir_pudding

20:200 is closer to -6 than -4.

Yes, it is. Mammals seem not to be quite that bad; more like -5, which would be 20:140. -4 would be more like 20:100, which is a little optimistic, but I thought it was close enough for gaming work.

At one yard, that would be about 0.05", which is about 3.5 points typographically. I think that would let you read headline type but not ordinary print. You need to be able to distinguish five adjacent lines to read an eye chart; if each line is 3.5 points then you can manage 18 point type.

There are also issues about discerning people's emotions from their facial expressions. GURPS doesn't talk about the impact of Bad Sight on social interaction, but realistically there should be some penalties.