My perscription got weaker. How?

Question

I went for an appointment at the opticians today. My perscription got slightly weaker (0.25 in both eyes)- implying that my eyes are now closer to good vision than before.

I was wondering what the physical mechanisms behind this change are?

Also, what units do they use when saying "you are -1.25 +1.5", for example?

Answer 1

Don't have all the answers, but this does happen sometimes. It has mostly happened to me when I've been wearing contact lenses more than glasses.
One doctor told me that the contact lenses can actually help the eyes get better or at least not get worse.
I've only been that lucky about 3 times in my life.

Answer 2

As we age the eye shape can cahnge, the quaity of teh fluid inside the eye also changes, and these can affect the strength of the prescription we need.
The + and - mean that you are a set degree from "normal" ie 0. One represent short sight and one represents long sight but Im not sure which is which;

Answer 3

good luck!