By inserting a hard or soft contact lens, an eye gains two additional refracting surfaces. The brightest light reflex on the phakic eye now comes from the contact lens surface (Pcl). If one holds a point-shaped light source such as an ophthalmoscope obliquely horizontally at a distance of 30 cm to an eye with a soft spherical contact lens, all reflexes (Pcl as well as the Purkinje reflexes P1, P2, and P4) lie on a horizontal line. With a minus contact lens, Pcl shifts away from P1 towards the corneal limbus, and with a plus lens towards the center of the pupil. However, if—with the ophthalmoscope held obliquely horizontally—Pcl on a soft contact lens shifts in a vertical direction, while P1, P2, and P4 continue to lie on an equatorial line, then the lens usually also has an astigmatic effect.