the best thing that you can do is to watch a bright light in the dark or involve your vision in dim light.
for example. no watching TV in the dark
no playing video games in the dark
no reeding in dim light.
even if these tips refuse to improve eye power. it will definitely stop further damage.
my grand ma says that the way into your body is through your mouth .definitely fresh green leaves improves vision!!
for further details, you can read my hub on beautiful eyes.