1) Foreign objects in the eye
Most small foreign objects in your eye such as sand or dirt will work themselves out of your eye naturally. If you have an irritant in your eye larger than a speck of dirt, and it doesn't work itself out on its own, call your eye doctor immediately.
2) Cuts or Scratches
A cut or scratch in the eye or on the eyeball can cause permanent harm if not treated. There is a lot of fluid and tissue surrounding the eyes that are quite sensitive and can easily be damaged long term if not properly treated. If you have a cut or scratch on your eye, contact your eye doctor.
3) Chemicals in the eye
Getting any kind of chemical in the eyes is extremely dangerous. When we talk about chemicals we mean cleaning products, lawn fertilizers, paints, aerosols air fresheners, or kitchen cleaners, etc. If any of these items (or others) got into your eye, call your eye doctor immediately.