[robert_tweed]

A glass eye filled with tritium would probably give enough light to read with, continuously, with a half-life of 10 years.

It might get a bit annoying when you want to go to sleep though.

https://en.wikipedia.org/wiki/Tritium_radioluminescence

[eesmith]

Assuming I did the math right:

2 cd/m2 * (7mm * 7mm * pi) = 0.00030787608 candelas = 307 µ candela.

Doesn't seem like much light.