Diagram of light and four<unk>  An eye with<unk> <unk>  are reflections of objects from the structure of the eye. They are also known as<unk>  reflexes and as<unk> –Sanson<unk> . At least four<unk>  are usually visible. The first<unk> (P1) is the reflection from the outer surface of the cornea. The second<unk> (P2) is the reflection from the inner surface of the cornea. The third<unk> (P3) is the reflection from the outer (anterior) surface of the lens. The fourth<unk> (P4) is the reflection from the inner (posterior) surface of the lens. Unlike the others, P4 is an inverted<unk> <unk> –Sanson<unk>  are named after Czech anatomist Jan Evangelista Purkyně (1787–1869) and after French physician Louis Joseph Sanson (1790–1841). The third and fourth<unk>  can be visible from within the eye itself. Light reflected away from the surfaces of the lens can in turn reflect back into the eye from the rear surface of the cornea. The first and fourth<unk>  are used by some eye trackers, devices to measure the position of an eye. The cornea reflection (P1<unk>  used in this measurement is generally known as glint.
Purkinje images
VA conduction
QRS complex
E/A ratio
J wave
High frequency QRS
Plateau potentials
QT interval