Reading from a tablet or smart phone in the dark is okay for your eyes, as long you don't spend an excessive amount staring at the screen. These devices, however, emit blue light, a short wavelength light with high energy that may cause damage to the structures of the eye if exposed to this light for a long period of time. Moreover, studies have shown that blue light can disrupt melatonin production which is required for a healthy sleep cycle. Village Eye Centre eye care professionals recommend limiting screen use in the last hour prior to bedtime.