The sonic lorgnette was a type of sonic device that was used by Paternoster Gang member Strax. It was mainly used to observe a person's anatomy, though it could also be used to scan the subconscious as well as a person's current age and expected lifespan. The device was held by a handle at the bottom. Multiple small round lenses were at the top of the tool, through which the examination could be conducted. Each of these components could be twisted into place around a small central piece which featured a green light. The lens that was usually used was yellow. When operational, the device made a series of whirring noises. While x-rays were being taken, the person's internal anatomy was actually illuminated with green light.
Once, in 1890s London, Strax used his sonic lorgnette to examine Clara Oswald. He first applied it to check her left eye, which he mistook as her mouth. The device repeatedly beeped when he began inspecting her subconscious, though she soon prevented him from viewing that aspect any longer. Strax then moved onto taking x-rays of her thorax and spleen. He was impressed by her spleen and confirmed she was aged twenty-seven, but Clara interrupted him from announcing her exact projected lifespan. Even though he was meanwhile using the device, Strax mistook Clara as being undressed, an error in his observations that she was quick to correct. She then plucked the device out of his hand and dumped it on a table. (TV: Deep Breath)
Behind the scenes
The sonic lorgnette was one of three props (all of which were sonic devices used by the Paternoster Gang) that resulted from a Blue Peter competition. The lorgnette was designed by an eleven-year-old boy from Hampshire named Arthur. In his design, the yellow lens was merely to be used as a "diagnostic lens" for viewing illnesses. The illustration additionally had two separate lenses – a blue lens for x-ray vision of not only people but also objects, and a red "thermal lense for detecting people." Furthermore, the light at the centre of the device was referred to as being a "sonic light". Steven Moffat, who helped judge the competition, commented, "You feel you want to pick it up and hold it, but it's also about the other side of his life because – of course – Strax is a nurse and this allows him to examine his patients and see what's wrong with them. I think it will be very funny seeing Strax's big clumsy hands holding that."  The stage directions from the script of Deep Breath referred to the device as "a hi-tech multifunction lorgnette device (Blue Peter)," excluding it being mentioned as sonic in nature.