How should Minims Proxymetacaine hydrochloride 0.5% w/v eye drops be stored, including when refrigeration is unavailable?

Store Minims Proxymetacaine hydrochloride 0.5% w/v eye drops at 2–8°C in the outer carton without freezing; if necessary, they may be stored at temperatures not exceeding 25°C for up to 1 month only.