The document discusses different types of reduced eye models, including Donders' reduced eye model. It provides details on Donders' model, which treats the eye as a single refracting surface located 2mm behind the cornea with a radius of curvature of 5mm. The principal point is located 2mm behind the cornea, the nodal point is 5mm behind the principal point, the anterior focal length is 15mm, and the posterior focal length is 20mm. The refractive index is given as 1.336 and the total power of the model is +60D.

1. REDUCED EYE
Submitted by Amalu chacko.
2nd year optometry.
Abhaya collage of optometry

2. The reduced eye an idealized model of the optics
of human eye . Introduce by Donders
The reduced eye replace the several refracting
bodies of the eye are replaced by an ideal air /
water interface surface that is located 20mm from
a model retina this is coverts a system with six
cardinal points into one with three cardinal points

3. Principal point p
Posterior focal point F2.
Anterior focal length F1 and posterior focal length F2.

4. Types of reduced eye
Listings reduced eye
Donders reduced eye.
Bennett and Rabbets reduced eye

5. REDUCED EYE

7. Donders Reduced Eye
Donders converted the cardinal data into
round ,so that they can be remembered
eassily .in his over as a simplified Reduced
Eye ,he treated the eye as a single surface
with the following lowing cardinal data .
( Fig 1.47c)

8. Principal point (p) lies 2 mm behind the cornea
with a radius of curvature of 5 mm.
Nodal point (N) is situated 5 mm behind the
plane.
Anterior focal length (f1) is 15 mm.
Posterior focal length (f2) is 20 mm.
Refractive index is 1.336.
Total power is + 60D.

11. ● Principal point (p) lies 1.5 mm
behind the Anterior surface of
cornea and represent the vertex
of a single refracting surface
when radius of curvature is 5.7
mm

12. ● Nodal point ( N) is situated
7.2 mm behind the Anterior
surface of cornea i.e at the
center of curvature of single
refracting surface .( 1.5 +5
.7=7.2)

13. ● Posterior focal point ( on the
retina ) is 24.13 behind the
Anterior surface of cornea
● Anterior focal point is15.7 mm in
font of Anterior surface of cornea

14. ● Anterior focal length is 17 .2 mm
and the posterior focal length is 32.
63mm● Uniform refractive index is
1.336.
● Total dioptric power is +58.20

15. Difference between Reduced eye
and schematic eye and example of
these two models
Schematic: multiple refracting surface .
Eg: gullstrand 1and 2.
Reduced : only one refracting surface
eg: Emsely ,ssrs

16. Surface: one spherical refractive surface
power: usually around +59D
Reduced Eye : surface and
power

17. Conclusion
A simple computer program for Reduced Eye
is presented .the user supplies distances
from the front of the eye and radii of
curvature of refractive surface ( Anterior and
posterior cornea and lens ) , distance to
rentina ,and refractive indices of ocular
media ( corena , aqueous, lens, vitreous,).

18. The program produce power
of optical components and of
the whole eye ,cardinal points
of eye,and estimate of
refractive state and retinal
image size

19. Reference

20. Thank you