I am recovering from a concussion and have sensitivity to light which amongst other things means I cannot use devices as they triggers headaches or worsens existing symptoms straightaway. I purchased anti blue-light filters for my phone, laptop and monitor hopping that these would help. I applied the filter to my phone and it made an immediate difference - I was able to start using the device. Most importantly it did not cause or worsen any symptoms! It was night and day! If you are in my situation you still want to limit how long you interact with devices until recovery improves. The filters are easy to apply. Ocushield provide videos online that show you how to apply the filters. Do take time to review the videos as they are useful. I reached out to customers support a number of times and the team were responsive, polite and helpful. I have found these filters to be a high quality product. I was looking for a product that was medically certified and these filters are accredited as a class 1 Medical Device by the UK and the USA. I was impressed with the results and bought filters for my daughter to prevent headaches. She is at university and uses a lot of devices. These are great products and if you suffer from headaches (including migraines) and you use devices then do take a look. Even if you do not have any headaches consider them as a necessary accessory and a preventative measure for your health.