<prompt> Gonioscope is used for visualization ofAnteior chamber anglePosterior chamber angleAnterior surface of lensPosterior chamber  <response>: Gonioscopy: Owing to lack of transparency of corneoscleral junction and total internal reflection of light emitted from angle structures at the anterior surface of cornea it is not possible to visualize the angle of anterior chamber directly. Therefore, a device goniolens is used to dive the beam of light and this technique of biomicroscopic examination of the angle of the anterior chamber is called gonioscopy. Types of goniolens: i Indirect goniolens provides a mirror image of the opposite angle, e.g., Goldmann and the Zeiss goniolens ii Direct goniolens provides a direct view of the angle. Koeppe goniolens is the most popular type. The angle structures seen from behind forwards are: 1. The root of the iris 2. The anteromedial surface of the ciliary body ciliary band, 3. Scleral spur 4. Trabecular meshwork and Schlemms canal and 5. Schwalbes line Applications of gonioscopy: 1. Classification of glaucoma into open angle and closed angle based on the configuration of the angle. 2. Localization of foreign bodies, abnormal blood vessels or tumors in the angle. 3. Demonstration of the extent of peripheral anterior synechiae and hence planning of glaucoma surgery. Ref: Khurana comprehensive ophthalmology; 4th edition Pg: 546 