What happens when or if eye wash freezes?

According to eyewash SDS, excessive exposure to extreme heat or cold should be avoided.

If eyewash freezes and there is no evidence of leakage then the product should be OK. Freezing will not harm the eyewash.

The only issue is sterility: Water expands when it freezes so if the seal is broken, the bottle or cap is cracked or there is any other evidence that leakage occurred then throw it out.