2. Mode of image formation:-
• Images are formed due to reflection and refraction
• Purkinje images are formed due reflection of light in the eye.
• 4 purkinje images are formed in the eye
3. • 1st purkinje image formed due to anterior cornea ( convex)
• Image formed due a.cornea is virtual and erect
• Image is formed nearer to anterior surface of lens and next to the 2nd
image
• 2nd purkinje image is formed by posterior cornea( convex)
• It is virtual and erect image formed nearer to anterior surface of lens and
front of first image
• 3rd purkinje image is formed by anterior surface of lens(convex)
• Image is formed next to 4th image almost in vitreous.H
• Virtual and erect
4. • 4th purkinje image is formed by posterior surface of lens(concave)
• Its tha only real and inverted purkinje image
• Present back to the 3rd image
• Nearer to posterior lens surface
5. Importance of purkinje images
• Purkinje image 1 has many important clinical applications, including
kerotometry and corneal topography
• Used in measuring angle kappa(angle of deviation)
in Hirschberg test
6. • 1st purkinje image is about 3.90 mm right to anterior cornea
• Can find using formula F=-2/r and vergence relation L’=L+F
• The first and fourth Purkinje images are used by some eye trackers,
devices to measure the position of an eye.
• Eye tracking is the process of measuring either the point of gaze
(where one is looking) or the motion of an eye relative to the head.
An
• Purkinje Image Tracking
• The first and fourth Purkinje images can be used for tracking the
direction of gaze by the Dual-Purkinje Image technique, which uses
the relative positions of these reflections to calculate the direction.
