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AREA 2: Fitting single-vision lenses

AREA 2: Fitting single-vision lenses. Topic 4: Alignment, decentration, and minimum diameter Topic 5: Calculating thickness in spherical lenses Topic 6: Calculating thickness in astigmatic lenses Topic 7: How lenses affect vision Topic 8: Prismatic effects Topic 9: Base rules

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AREA 2: Fitting single-vision lenses

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  1. AREA 2:Fitting single-vision lenses Topic 4:Alignment, decentration, and minimum diameter Topic 5:Calculating thickness in spherical lenses Topic 6:Calculating thickness in astigmatic lenses Topic 7:How lenses affect vision Topic 8:Prismatic effects Topic 9:Base rules Topic 10:How alignment affects binocular vision

  2. Topic 7:How lenses affect vision • Changes in visual field • Changes in retinal image size • Effect of vertex distance

  3. Changes in visual field Peripheral visual field Central visual field

  4. Changes in visual field S S 60º 60º 95º 60º T N N T 95º 60º 75º 75º I I OD OS

  5. Changes in visual field Reduction of visual field by frame Apparent visual field

  6. Changes in visual field Reduction of visual field by lens vergence Plus lens Minus lens Real visual field

  7. Changes in visual field Calculation of real visual field (2)

  8. Changes in visual field Scotoma in plus lenses

  9. Changes in retinal image size Spectacle magnification

  10. Changes in retinal image size Spectacle magnification:

  11. Changes in retinal image size Thin lens Reverse afocal Galilean viewfinder

  12. Changes in retinal image size Afocal Galilean viewfinder

  13. Changes in retinal image size Thin lens

  14. Spectacle magnification: Changes in retinal image size Ms Mp

  15. Changes in retinal image size

  16. Changes in retinal image size Spectacle magnification

  17. Changes in retinal image size Anisometropia and aniseikonia

  18. Changes in retinal image size Anisometropia and aniseikonia

  19. Changes in retinal image size • <3% No symptoms • 3-5% Asthenopia • >5% Problems with binocular vision Aniseikonia

  20. Aniseikonia caused by anisometropia Changes in retinal image size

  21. Changes in retinal image size • Myopia, anisometropia > 3.00 D • Hyperopia, anisometropia > 2.00 D Aniseikonia greater than 5%

  22. Changes in retinal image size Distortion in astigmatic lenses:

  23. Changes in retinal image size

  24. Changes in retinal image size Angular distortion 120º-2.00+6.00 D

  25. Changes in retinal image size Effect of angular distortion Cylinder axis expressed as plus cylinder Image Object

  26. Changes in retinal image size Object 50º +2.00 +4.00 D lens

  27. Effect of vertex distance

  28. Effect of vertex distance Example:New frame Myope:Glasses prescription with vd of 12 mm, -9.00 D Glasses prescription with vd of 15 mm, -9.25 D

  29. Effect of vertex distance Example:Fitting a contact lens (above 5.00 D)

  30. Effect of vertex distance Example:Signs

  31. Effect of vertex distance Example: Signs

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