1.Nawat Watanachai Sakarin Ausayakhun 2010

2. Visual optics Understanding theremarkable inner workings of the eyes optics Problems Complicated imperfection Schematic eye 3. Schematic Eye Conceptualizing the optical properties of human eye To determine mathematic living eye models Developed by Gullstrand, professor of ophthalmologyin Sweden. Nobel Prize 1911 4. Gullstrands schematic eye 5. Reduced schematic eye Schematic eye can be simplified even further We can treat eye as it was a single refracting element Ideal spherical surface separating two media of refractive indices 1 and 1.33 Known as reduced schematic eye Nodal point = Cornea and lens 6. Reduced schematic eye P=60 D. N=1N=1.33 7. Reduced schematic eye D=n/f, D=(n2-n1)/f D= 60 D., n(air)=1, n(eye)=1.33 f=n/D Ant.focal point = 1/60 = 17mm. Post.focal point = 1.33/60 = 22.6mm. D = (n-n)/f, f = (n-n)/D =(1.33-1)/60 = 5.5 mm. Nodal point = 22.6-17.0 = 5.6mm. 8. Schematic eye can calculate image size on retina Image size = Image distance Object size Object distanceImage size = Object size Image distance Object distance 9. Example m20 cm. retinal image?6 10. 20 cm. retinal lesion?Image size = Object size Image distance Object distance Image size = 200 mm. 17 mm. 6000 mm. Image size = 200x17/6000 = 0.6 mm.6m 11. Accommodation 12. Near point (NP) correspond accommodationretinaNP w/accommodationfull 13. Far point (FP) correspond retina accommodation refractionFP w/o accommodation 14. Emmetropia FP w/o accommodationNP w/ accommodation 15. Myopia FPNP w/o accommodationw/ accommodation 16. Hyperopia FP w/o accommodationNP w/ accommodation 17. Far Point conjugate accommodationretinaEmmetropia Myopia FPFP FP Hyperopia 18. Near point of accommodation NPAVisual axis conjugate Retina accommodation NPA amplitude of acommodation Presbyopia accommodation progressively decrease with age NPA ( ) 19. Accommodation decrease with age 20. Presbyopia Acc. lossreading required40 ac.reserve 33 cm. acc.1/33/100 = +3 D 20 reserve power 10 D 45 reserve spare = 3.5-3 = 0.5 fatigue 21. Accommodative amplitude 48 yr. decrease 0.50 D./ each 4 yr. Ex. 60 yr. = 1.5 D. 22. Accommodation Accommodative range = Accommodative amplitudeA= F N A = accommodative amplitude F = vergence N = vergenceFP NPFPNP 23. Example clear vision acommodative amplitude = 8.00 D.-4.00 D. clear vision = far point near point Far point = 100/4 = 25 cm. Near point = 100/(8+4) = 8.33 cm. clear vision 8.33-24 cm. 24. Myopia FN w/o accommodationw/ accommodation 25. Example clear vision +2.00accommodative amplitude = 4.00D. Uncorrect hyperope 2.00 farpoint = 100/2 = 50 cm. accommodation +2.00 D. far point infinity accommodation 2.00 D. near point 100/(4-2) = 50 cm. clear vision 50 cm infinity 26. Hyperopia FNw/o accommodationw/ accommodation 27. Example Without correction, far point is located atfront of the eye and near point at eye.cm in cm in front of the What is refractive error of this eye? What is amplitude of accommodation of this eye? 28. FP cm 100/100 = -1 D rays)Fdistant correction = divergentN w/o accommodationw/ accommodation 29. FP vergenceaccom.cm FP- DNPcm vergenceNP - D A = F - N = (-1)-(-3) = 2 Damplitude of accommodationD 30. Reading add prescription add accommodative amplitude example 54D-2. 30 cmD,accom. Amplitude add 31. cm ( accommodation 50% add 2.50 DFD)DN w/o accommodationw/ accommodation 32. Example 54 accom. Amplitude-2.00 D. D -2.00 (FP 50 cm) AA=1 D (NP 33 cm) accommodation30 cm, 33. Correcting myopia P fF 34. Correcting myopia P1 F1, f1VD1 35. Correcting myopia f1PfVD ----> f2 > f1 correcting lens - D(P2 f2 < f1 correcting lens D(P > P1 D 39. Vertex distance refractive errorpower refractive error lens powerVD significant change lens DVDcontact 40. CL power 41. Aphakic lens +12 D (VD15 mm)prescribe VD Dioptric error10 mm. 42. +12 D, F = 100/12 = 8.3 cm. RVD 15 mm. 8.3 1.5 cm = 6.8 cm. = FP VD 10 mm. = 6.8 + 1.00 = 7.8 cm 43. P = 100/7.8 = +12.80 D = 12.8-12.0 = 0.8 D*** *** VD error+4 D 44. Example +D mmmm power 45. : f2=110 mm = 11 cm + . Dpower20 mm =/= 46. Cylinder and Astigmatism Astigmatic Expression Spherocylinder form Combined cylinder form 47. Astigmatism- Corneal astigmatism - Lenticular astigmatismToric surface 48. Spherocylinder and its imagery CorneaO 49. Total astigmatism Total astigmatism = Corneal astigmatism + Lenticular astigmatismO Against-the-rule astigmatism 50. Total astigmatism Total astigmatism = Corneal astigmatism +lenticular astigmatism4240O With-the-rule astigmatism 51. Conoid of Sturm Anterior focal line Posterior focal line Interval of SturmO Circle of least confusion Spherical equivalent = sphere + (cylinder/I 52. Spherocylinder and its imagery 53. Astigmatic dial technique focal lineretina 54. Astigmatic dial technique focal lineretina 55. Astigmatic dial technique sphere retina)+SphVA(CLC 56. Astigmatism Compound hyperopicastigmatism Compound myopic astigmatism Mixed astigmatism Simple hyperopic astigmatism Simple myopic astigmatism 57. Cylinder Plus cylinder Minus cylinder Powercylinderaxis 58. Plus CylinderI Axis PowerOOI 59. Minus CylinderOIAxis PowerI 60. Against-the-rule astigmatism- .x retina 61. Against-the-rule astigmatism focal line focal lines- .x retina 62. With-the-rule astigmatism 4240- .x 180 retina 63. With-the-rule astigmatism 42focal line focal lines40- .x 180 retina 64. Cylinder cylinder Power Axis PowercylinderREaxisLE 65. Example + . D cylinder axis 180 power +5.00 D 90 @90x 180 +5.00@90/plano@180 optical cross 66. Plus cylinder form+ .sph + .x 67. Minus cylinder form -+ .sph - .x 18 68. spherocylinder: 3 0+ . x &+ . x Combined cylinder form+3.00sph 1. x Plus cylinder form3 sph -1. x 18 Minus cylinder form+2. 0 -1 0+1. 0 +3.0 0 +3. 0 69. Transposition minus sphere spherecylinder cylinder plus cylinderaxisnew 70. Example form shp + . x combined cylinder form spherical equivalentminus cylinder 71. . + . x (+2.00+1.00) -1.00 x 180 - . x Sph. Equivalent = + .+ (+ ./ )=+ .D 72. Combined cylinder form + . + . xcombined cylinder form0 = +3.00@180 x 180 = +3.00 x 90 73. Example -4.00 -0.5 x 90 -4.50 +0.5 x 180 -4.50 x 90 : -4.00 x 180 +2.00 -1.00 x 20 +1.00 +1.00 x 110 +1.00 x 20 : +2.00 x 110 74. The end Confusing???