The tick sign – a new and simple test to diagnose keratoconus at the slit lamp

We present a simple test doable on any slit lamp by which, relying on the positions of the Purkinje reflexes to one another (Tscherning 1898; Gullstrand 1909), keratoconus can be diagnosed. The beam of a small light source is directed onto an eye at about 30 cm distance from an 40°–20° oblique horiz... View More