Refraction and Retinoscopy

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Presentation made by Dr. Dimple Prakash from Dr. Agarwal's Eye hospital in Kalpavriksha 2012 in Chennai

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Refraction and Retinoscopy

  1. 1. Dr. Dimple PrakashHead Post Graduate Training Programme
  2. 2. SHADOW PLAY - RETINOSCOPY
  3. 3. Myopia HyperopiaAstigmatism
  4. 4. Plane Mirror Retinoscopy in case of Welsch Allen retinoscope when the lens is pushed down themirror acts like a plane mirror and the rays are divergent.
  5. 5. Concave Mirror Retinoscopy When the lens is pushed up the mirroracts like a concave mirror so the rays are convergent. Practical importance : in plane mirrorretinoscopy a with movement will need +lenses but in concave mirror retinoscopy a with movement will need – lenses.
  6. 6. Illumination Stage Reflex Stage Projection Stage
  7. 7. Illumination
  8. 8. • Rays are from S1• Image is at far point of subject• Shadow at pupil of subject• Projected to the examiner
  9. 9. Normal Eye +1.50 66 cm
  10. 10. Hyperopia (Small Eyes) +58 D
  11. 11. Myopia (Large Eyes) +62 D
  12. 12. StreakRetinoscopy
  13. 13. Break :Width : Narrowest whenallingned with true axisIntensity : Brightest whenalong with true axisSkew : When axis is notassigned reflex breakinginto two
  14. 14. Low Errors High ErrorsSpeed High LowBrilliance Bright DullWidth Wide NarrowNeutralization point : complete illumination of entirepupillary area.Swirl
  15. 15. Checking axis : Swirl WAKE UP 2.00DC @ 80 Add 45 degrees = 125 Minus 45 degrees = 35 Keep the streak at 125 and 35 Note the width : should be equal Side that is less : change axis slowly towards wider side.
  16. 16. GROSS NETPower of lens Followingthat is held in subtraction offront of the distance andexamined eye cycloplegicat which dropsneutralizationoccurs
  17. 17. Distance Subtraction Cycloplegic 1 mt = 1 D Atropine = -1.00 D 2/3 mt = 1.50 D Homatropine = -0.50 D Cyclopentolate = -0.75 DExample Distance (lm) Atropine+6.00 DS  +5.00 DS  +4.00 DS
  18. 18. Few Algebraic rules for signs of Cylinders- - = + - 6.00 - 4.00 = - 2.00- + = + - 6.00 + 4.00 = - 10.00
  19. 19. Practice Situations Net + 6.00 + 4.00Lower Value = Sphere = +4.00Difference = Cylinder = +2.00 + 4.00 - +6.00 = - Sign of cylinderAxis at lower value = 180 + 4.00 DS / -2.00 DC @ 180 Axis
  20. 20. 90 Axis Net - 6.00 DS - 4.00 DS 180 Axis* Lower value here is – 6.00 DS The rest is the same - - = +- 6.00 DS / +2.00 DC x 90 Axis
  21. 21. - 8.00 DS WAKE UP - 10.00 DS - 10.00 / +2.00 DC x 180 AxisSample Transpositions - 2.00 DS / -4.00 DC x 180 Axis1. Allegebric sum of the sphere and cylinder - 6.00 DS2. Change the sign of the cylinder - 6.00 DS / +4.00 DC3. Change the axis if above 90 = minus 90 if below 90 = add 90 - 6.00 DS / +4.00 DC @ 90 Axis
  22. 22. Refinement ofRefraction
  23. 23. Methods Easiest : fogging. Over refraction, over retinoscopy Duchrome testing Jackson cross cylinder Astigmatic dial Astigmatic fan and block
  24. 24. Jackson Cross Cylinder Components: sphere Cylinder Power: ½ that of cylinder Axis of Cylinder : 2 are perpendicular to each other Handle: 45 degrees always.
  25. 25. How it works? Axis first: handle in direction of the cylinder in the frame already. Eg) 2.00DC at 180 then keep handle at 180 Va chart 2 lines above least visible. eg)6/12 if BCVA is 6/6. Flip + 0.50 or – in front of patient. At best vision point, rotate the DC by 10 degrees towards the red mark in case of – and towards white mark in +.
  26. 26.  E.g.) DC in trial frame= +2.00DC @ 180 BCVA CLEAR when +0.50 DC is in front Rotate 10 degrees towards white mark +2.00 DC@ 170.
  27. 27. How it works? WAKE UP Power of DC. This is easy. Keeping the correct axis. Flip the JC by + or – and then add or subtract the correct power. E.g.) DC in trial frame = +2.00,Va better at +0.50 DC then final value= +2.50 DC. If equal Va at 2 flips: correct power.
  28. 28. Summary Most plus or least minus sphere: BCVA Va chart 2 lines above least visible. eg)6/12 if BCVA is 6/6. No cylinder, still flip at 90,180,45,135. Axis first : Why? Lower powers 0.25 for 20/30 Va .Flip + 0.50 or 1.00 for lower
  29. 29. Duchrome Chromatic aberration
  30. 30. Duchrome Normal : both equal Start with Red slightly better Focus on the letters
  31. 31.  Hyperope of +5.00 sees green better, increase to +5.25 D so sees red better. TE A K• Increasing the converging power so that “STRONGEST + LENSES “ are given. (asthenopia)
  32. 32.  Myope: - 5.00D sees red better leave him alone -5.00 D sees green then – 4.75 D get the rays in front. PO N F• “WEAKEST (– )LENSES”
  33. 33. Astigmatic dial technique
  34. 34. Fogging Indications : Young : Recurrent Asthenopia : H/O Squeezing / frowning : Difficulty in near work (E.g.) Needle work, MicroscopeReference Chart :If we start pt +20.00 DS upto +16 D: Decrease in lens in strengths of +2.00 DS(E.g.) +20.00 D = Next lens + 18.00 DS+16 D TO +12/10 D: Decrease in strengths of 1.00 DS (E.g.) +10.00  +9.00 DS, +8.00 etcUpto (+6.00 DS. From then upto +4.00 DS : +0.50 DS decrease+5.50, +5.00, +4.50 etc
  35. 35. Giving Glasses
  36. 36. Giving Glasses Age Hyperopia Fogging Refinement methods 1) Less than 3 years = Full retinoscopic correction Eg; +4.00 DS = Give + 4.00 DS Presence of tropia 2) 3 to 8 years Presence of phoriaEsotropia = Full gross value subjective to AC/A ratioPhoria = Full net  optimal, under correctionEg. Net Value +4.00 D in phoria = +3.50 / +3.75 which is accepted 3) Adults follow : rule of strongest +
  37. 37. Hyperopia with Age CorrectionHM 6.50 6.00 5.50 5.00 4.50 4.00 3.50 3.00 2.50 2.00 1.50 1.00 0 1 2 3 4 5 6 7 8 9 10 11 12 YRS
  38. 38. Giving Glasses : MYOPIAThumb rules  Normal patients1) From -1.00 to -6.00 DS : Full correction2) Above -6.00 DS : Under correct to meet subjectiveness  EsotropiaHigh presence of -6.00 DS and above are under correctedmeet acceptance followed by optimal to full correction  ExotropiaOver correct in intermittent EXOTROPIAS
  39. 39. Giving Glasses : Astigmatism  Normal patients WAKE UP: In a child less than 3 years = 1.25 DC, Regular: Older than 3 years = all astigmatism to be corrected• Child : follow-up 6 months• Adult yearly• Frequent change : over correct (0.25 D)
  40. 40. Giving glasses: child Ideal frame: large, sturdy, well balanced Ideal lenses: plastic, polycarbonates Ideal refraction: Less than 3 years: solely on retinoscopy All strabismus : retinoscopy Beyond 3 years: myopes do not need
  41. 41. Cycloplegic studies Rosenbaum and associates: atropine estimation of hyperopia 0.34 D more as compared to homatropine Hurol et al: no difference between 2 and 3 days of cycloplegia Stolovich: 8 instillations vs 4 instillations.
  42. 42. Bifocals
  43. 43. Bifocals Working distance 0.2 m wide or smallest test type Blurred/ not readable = near point No doubling Keep 1/3rd reserve
  44. 44. Tips on bifocals Keep 1/3rd reserve Undercorrect Full correction 23 mm of near point max (3.5D) Prisms for convergence thereafter
  45. 45. Practical Tips Do Dont Read Previous prescription Don’t make drastic glass changes from past “Suspicion” Bifocal to progressive progressive to Bifocals Adjust sphere first Do not try to change to E.g.) +1.25 DS / -0.75 DC higher astigmatism Change to +1.75 to +1.50 +1.25 DS / -1.25 DC
  46. 46. Practical Tips Do Dont 4. Try to correct the axis rather than the number Eg) -0.75 DC @ 90 Ax change to -0.75 DC @ 100 Ax rather than -1.00 DC @ 90 AxFinal Example-1.25 DS / -0.75 @ 80 Ax(a) -1.50 DS / -1.75 DS with -0.75 DC @ 80 Ax J(b) -1.25 DS / -0.75 DC @ 90 Ax J(c) -1.25 DS / -1.00 DC @ 80 Ax JL -1.50 DS / -1.50 DC @ 80 Ax
  47. 47. Make the right choice Low powers : smile and bye bye High plus: think! Chromatic aberrations prismatic aberrations High index lenses: 1.6 and 1.74 Thinner, flatter, lighter +4.00 D = high index
  48. 48.  Gets higher : plastic lenticular lenses Aspheric lenses : curves that flatten away from the center. Prismatic effects Myopes: higher powers -4.00 above 1.6 high index
  49. 49. Power refraction you are now armed Retinoscopy Interpretation of numbers Giving glasses Refinement of numbers What not to do
  50. 50. Dr. DIMPLE PRAKASH Senior Consultant Pediatric and SquintHead Post Graduate Training Programme

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