This document provides an overview of ophthalmic lenses and vergence calculation. It defines different types of lenses like spherical and astigmatic lenses. It discusses key lens properties such as radius of curvature, power, focal length, and image formation. The document also covers vergence, vergence calculation using the Lensmaker's equation, and examples of calculating image location and magnification using multiple lenses.

1. Ophthalmic lenses, vergence calculation and
image formation.
Dr Azmat Khan
THE UNIVERSITY OF LAHORE
(ISLAMABAD CAMPUS)
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2. Contents:
 Definition of lens,
 Spherical lens ,its types and construction ,
 Radius of curvature and power,
 Focal length, focal point and power of lens,
 Image formation through spherical lenses ,
 Astigmatic lens and its types ,
 Vergence , vergence calculation ,
 Application of lensmarker equation.
 Combination of lenses and image formation.
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3. Lens 3

4. Spherical lenses 4

5. Radius of curvature 5

6. Radius of curvature and Power 6

7. Formation of convex and concave
lens
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8. Flat and curve lenses 8

9. Spherical lenses 9

10. Types of spherical lenses 10

11. Focal point and focal length. 11

12. Focal point and focal length. 12

13. Image construction 13

14. Image construction 14

15. Image construction 15

16. Image construction 16

17. Power of lens 17

18. Power of thin lens 18

19. Vergence 19

20. Vergence 20

21. Dioptric power of lenses 21

22. Vergence of rays 22

23. Refractive power of spherical surface
 P= n2—n1/r
 n1 and n2 refractive indices
 r radius of refracting surface ( in m ) .
 Example.. Consider two spherical refractive surfaces both construted from
glass (n=1.5) , one surface has radius of 10cm while second surface has
20cm. Calculate power of each surface .
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24. Magnification 24

25. Astigmatic lens 25

26. Cylindrical lenses 26

27. Focal line formed by astigmatic lens 27

28. Toric surface 28

29. Toric lenses 29

30. Circle of least confusion 30

31. Spherical Equivalent 31

32. Vergence calculation 32

33. Lensmaker’s equation. (LME)
 n/o +p = n’/i or U+P=V
 Most imp equation in ophthalmology .
 LME says 2 thing:
 Location of image depend on the location of object.
 Establishes a relationship between shape of refracting surface and its
optical function. ( spherical surface power formula )
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34. Examples…… 34

35. Examples…
 Two lenses .. First power of +5D, second +8D, separation 45cm. Object 1
m in front of first lens .
 Where is the final image ?
 What is the transverse magnification?
Transverse magnification = reduce object vergence / reduce image vergence
Total magnification is the product of individual magnification.
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