This document discusses catoptric images, also known as Purkinje-Samson images, which are images formed inside the eye by reflections at the refractive interfaces of the eye. It notes that images 1-3 are formed by reflections at the anterior cornea, posterior cornea, and anterior lens surfaces, and are virtual and erect, while image 4 from the posterior lens surface is real and inverted. Some common uses of Purkinje images are to locate axes and angles in the eye, measure corneal curvature, and measure eye movements and lens changes during accommodation. Clinical uses include testing for cataracts and measuring lens position and curvature using keratometry and the Hirschberg corneal reflex test.

1. CATOPTRIC IMAGES
S. Arya Das
1st YR,2nd SEM
BACHELOR OF OPTOMETRY
BHARTIMAIYA COLLEGE OF OPTOMETRY

2. CATOPTRIC IMAGES
Catoptric image is also
known as Purkinje- samson
image. It refers to the image
formed inside the eye as a
result of reflection occuring
from the each refracting
interface of the eye.

3. IT INCLUDES
Anterior surface of cornea
Posterior surface of
cornea
Anterior surface of lens
Posterior surface of lens

4. FEATURES OF PURKINJE-SAMSON IMAGES
Image 1,2 and 3
formed by reflection
from the anterior
corneal, posterior
corneal and anterior
lens surface. The
image formed from
the convex reflecting
surface is virtual and
erect.
Image 4 formed by
the reflection from
concave posterior
lens surface is real
and inverted.

5. COMMON USES OF PURKINJE IMAGE
Locating axes and their associated angles in the eye.
Measuring corneal curvature.(keratometry)
Measuring eye movements and eye positions.
Measuring lens changes in accomodation.
Measuring lens position and curvature.

6. CLINICAL USES OF PURKINJE-SAMSON
IMAGE
Used to test
catract
In
keratometry
Hischberg
corneal
reflect test

7. PURKINJE IMAGE TEST IN CATRACT
AND APHAKIA
In patients with mature senile
catract, instead of four only
three purkinje images are seen,
as the images 4 formed by the
posterior lens surface is absent.
In aphakia 3 as well as 4
purkinje images are absent.
Hence, only two images are
formed.

8. CONTINUE...........

9. KERATOMETRY
Keratometry which is
the measurement of
curvature of cornea
is based on the 1st
purkinje image.

10. PRINCIPLE OF KERATOMETRY
The principle of keratometer is based on the fact that, the
anterior surface of the cornea acts as a convex mirror and
the size of the image formed varies with the curvature. The
greater the curvature of the cornea, lesser is the image size.

11. KERATOMETER

12. HIRSCHBERG CORNEAL REFLEX TEST
Hirschberg corneal reflex test
is mainly used to diagnose
strabism which, also uses 1st
purkinje image.
STRABISM :- It is an eye
condition in which the visual
axes cannot be directed at the
same point of fixation under
normal condition of seeing.

13. CONTINUE..........
This test is
dependent on the
radius of the corneal
curvature and the
depth of the
anterior chamber of
the eye.

16. CHANGE IN LENS DURING
ACCOMODATION

17. REFERENCE

18. THANK YOU