Reduced eye

Reduced eye

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

2. INTRODUCTION 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. The reduced Eye Nodal point N Anterior focal length point f1 Principal point p Is the simplified version by Listing and Donders 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

6. Donders 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.

9. Listing’s Reduced Eye

10. Listings simplified the data by choosing single principal point and single nodal point lying between two principal point and two nodal point , respectively.this is called Listings Reduced Eye.

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 Theroy and practice of Optics And Refraction ( book) Google

20. Thank you