You searched for: “diploscope
diploscope (s) (noun), diploscopes (pl)
1. An instrument that is used to evaluate binocular vision and which may be used for the treatment of anomalies of such vision: Janet noticed that she couldn’t see as well as before, but after being examined with the diploscope by the ophthalmologist, her ailment was analyzed and a remedy was arranged to cure her problem.
2. A device used for the evaluation and treatment of ocular misalignment: Diploscopes can detect, assess, and provide remedies for double vision, which occurs simultaneously when something is seen with both eyes at the same time.