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 fieldChanges in visual field Changes in retinal image sizeChanges in retinal image size Effect of vertex distanceEffect of vertex distance

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

4. 60º 75º 95º TN S I 60º 95º 75º T S I ODOS Changes in visual field 60º N

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

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

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

8. Scotoma in plus lenses

9. Spectacle magnification Changes in retinal image size

10. Spectacle magnification: Changes in retinal image size

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

12. Afocal Galilean viewfinder Changes in retinal image size

13. Thin lens Changes in retinal image size

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

15. BVP (D)Tc (mm)P 1 (D)MsMpSM% SM -20.000.700.001.0000.758 -24.2% -15.000.700.001.0000.806 -19.4% -10.000.80+3.001.0020.8620.864-13.6% -5.000.80+4.491.0020.9260.928-7.0% 01.80+5.961.0071.0001.0070.7% +5.004.50+10.191.0311.0871.12112.1% +10.007.00+12.271.0601.1901.21626.1% +15.008.50+13.841.0841.3161.42642.6% Changes in retinal image size

16. Spectacle magnification

17. Anisometropia and aniseikonia Changes in retinal image size

18. Anisometropia and aniseikonia Changes in retinal image size

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

20. TcP1P1P2P2BVP  SM n = 1.523 vd = 15 mm Ø = 65 mm OD2.04+5.21-4.25+1.00 7.1% OS5.28+7.78-4.00+4.00 n = 1.8 vd = 12 mm Ø = 65 mm OD1.66+5.22-4.25+1.00 5% OS3.68+7.87-4.00+4.00 n = 1.8 vd = 12 mm Ø = 55 mm OD1.9+5.22-4.25+1.00 3.8% OS1.9+5.22-1.25+4.00 Aniseikonia caused by anisometropia Changes in retinal image size

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

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

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

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

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

27. Effect of vertex distance

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

29. Example: Fitting a contact lens (above 5.00 D)

30. Movement of glasses to see better HyperopiaMyopia Closer to the eyesOvercorrectedUndercorrected Away from the eyesUndercorrectedOvercorrected Effect of vertex distance Example: Signs

31. Example: Signs Effect of vertex distance