A reading aid was a type of technology that helped blind or visually impaired people to see and read.
After he went blind after being exposed to space without protection, the Twelfth Doctor made use of a reading aid in his sonic sunglasses. (TV: Extremis, The Pyramid at the End of the World) He stopped using it after regaining his sight. (TV: The Lie of the Land)
The Twelfth Doctor of the Shadow World used a reading aid with Circular Gallifreyan on it. The device temporarily restored his eyesight by borrowing it from his future. (TV: Extremis)