What is an endoscope used for?

1. Endoscopes are used to explore the body through various orifices or minor incisions. 2. Light travels down one fibre bundle to illuminate internal parts, and reflected light returns through another to be observed. 3. Because a bundle of fibres with fixed neighbours can transmit an image, no lens is needed to carry the picture out. 4. Measuring the curvature of the cornea is the job of a keratometer, which uses the eye as a convex mirror instead. _Source: OpenStax College Physics (CC BY 4.0), Ch 25 "Geometric Optics", section 25.4 Total Internal Reflection_