Purkinje images are
reflectionReflection is the change in direction of a wavefront at an interface between two differentmedia so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves...
s of objects from structure of the
eyeEyes are organs that detect light, and send electrical impulses along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system...
. They are also known as Purkinje reflexes and as Purkinje-Sanson images. There are at least four Purkinje images that are visible on looking at an eye. The first Purkinje image (P1) is the reflection from the outer surface of the
corneaThe cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is approximately 43...
. The second Purkinje image (P2) is the reflection from the inner surface of the cornea. The third Purkinje image (P3) is the reflection from the outer (anterior) surface of the
lensThe lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a sharp real...
.
Discussion
Ask a question about 'Purkinje images' Start a new discussion about 'Purkinje images' Answer questions from other users |
Purkinje images are
reflectionReflection is the change in direction of a wavefront at an interface between two differentmedia so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves...
s of objects from structure of the
eyeEyes are organs that detect light, and send electrical impulses along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system...
. They are also known as Purkinje reflexes and as Purkinje-Sanson images. There are at least four Purkinje images that are visible on looking at an eye. The first Purkinje image (P1) is the reflection from the outer surface of the
corneaThe cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is approximately 43...
. The second Purkinje image (P2) is the reflection from the inner surface of the cornea. The third Purkinje image (P3) is the reflection from the outer (anterior) surface of the
lensThe lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a sharp real...
. The fourth Purkinje image (P4) is the reflection from the inner (posterior) surface of the lens. Unlike the others, P4 is an inverted image.
Purkinje-Sanson images are named after
CzechCzechs are a western Slavic people of Central Europe, living predominantly in the Czech Republic. Small populations of Czechs also live in Slovakia, Austria, U.S., Brazil, Argentina, Canada, Germany, Russia and other countries...
anatomist
Jan Evangelista PurkyněJan Evangelista Purkyně was a Czech anatomist and physiologist.-Biography:...
(1787-1869) and after
FrenchFrench people can refer to:* The legal residents and citizens of France, regardless of ancestry. For a legal discussion, see French nationality law.* People whose ancestors lived in France or the area that later became France....
physicianA physician — also known as medical practitioner, doctor of medicine, medical doctor, or simply doctor — practices the ancient profession of medicine, which is concerned with maintaining or restoring human health through the study, diagnosis, and treatment of disease or injury...
Louis Joseph Sanson (1790-1841).
The third and fourth Purkinje images 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. These images are, therefore,
entoptic phenomenaThis is a medical definition of entoptic phenomena. For an alternative use within archaeology please see Entoptic phenomena Entoptic phenomena are visual effects whose source is within the eye itself...
.
The first and fourth Purkinje images are used by some eye trackers, devices to measure the position of an eye.
Brightness of Purkinje Images
The brightness of the Purkinje images can be determined using Fresnel's equation where the
Purkinje image I is the brightest of the four then PII, PIII and PIV (III and IV have about the same brightness).
The Purkinje images can be used to assess the curvatures and separations of the surfaces in the eye.
External links