I have recently been prescribed autologous serum tears by Dr Akpek at Wilmer in Baltimore. I instill them 5 times a day. My initial challenge was how to keep them with me AND cold all day as well as where to store them at work. After doing a lot of looking and purchasing several pretty useless items, I came upon a gem. I purchased a 12 oz water bottle called the Water Vault. I put ice in the bottom, then place my drops in a ziplock bag on top. The ice stays frozen for several days. I was out in the 90 deg heat for 12 hours on Saturday and at the end of the day the ice was barely melted. Hope this is helpful for someone out there.