A bit ago I accidentally shined my phone flashlight in my cats eye for a few seconds and then I got curious, how sensative is a cat's eye and will it hurt/damage them if I per say accidently shine my phone light at their eye for a few seconds
I would not shine a light on their eyes for too long because they are very light sensitive. Only briefly if needed to see if their eye is injured or something like that. It would be best to hold them and use a table lamp close by with the shade off if you need to look at their eyes.
A few seconds probably did not do any lasting damage, although the cat may have somewhat diminished vision for a few minutes. The real danger is with laser lights, which should NEVER be shone in a cat's eyes. Double care, there.