Blurred vision clears if I only use half of the eye.

[JohnDJasper]

Hopefully I can explain this satisfactorily! I'm farsighted and only wear glasses for reading and other close work. Viewing the Snellen chart from 20ft away, the biggest letters are fuzzy around the edges. I've just today discovered that if I block the vision from half of either eye or both eyes at once by using a bit of card, even extremely small writing suddenly comes into focus. Even then it's not perfect but this is improved by using only 1/4 of the eye's vision (not easy to do!)

Although I suspect that the cure for this problem will be the same as for all other refractive errors, I would like to be able to identify it just in case there are special instructions I need to consider.

Regards,
John

[Pikachu]

I suspect that this has something to do with the so-called "pinhole effect". I forget the exact mechanics of it, but it's a sort of artificial effect and probably doesn't have too much to do with the eyes themselves. Not entirely sure though.