There has always been a continuous eager to develop instruments that allow in vivo visualization of the eye, both the gross structure and the microstructure. This study focuses on the massive evolution that took place in the microstructural examination of the anterior segment of the eye, which started in the early 19th century with the development of the condensing lens and ophthalmic loupe, then with development of the slit-lamp by Gullstrand in the early 20th century (and later the photo slit-lamp) and finally all the modern examination techniques that appeared in the late 20th and early 21st century.