2. 1. Retinoscopy (Objective Refraction) 2. Cycloplegia / Mydriasis 3. Refinement (Subjective Refraction) 4. Binocular Balancing 5. Prescription Of Spectacle Lenses

3. 1. Manual retinoscopy – a. Dry b. wet (cycloplegia / mydriasis) 2. Automated retinoscopy

4. o Alternative method, takes less time. Optical Principles : 1. The Scheiner Principle 2. The optometer principle.

5. o Types - Based on operational method used: 1. Analysis of image quality: Dioptron, Canon Autorefractometers, Hoya Autorefractometers. 2. Retinoscopic Scanning : Ophthalmetron, Humphrey Autorefractor, Nikon 5000 & 7000. 3. Scheiner disc refraction : 6600 Autorefractor, Nidek &Topcon Autorefractor

9. o Pts. having active accommodation. (<18 yrs). o Should be done once for every pat., preferably during an initial evaluation. o Rule out - Allergies/medications /medi.cond.

10. Effect of Cycloplegia :- o Latent Hypermetropia :- Cycloplegic Loss of tone Zonules taut Flattening of lens Less convergence Shift to Hypermetropic side

11. Cyclopentolate Hcl - (0.5-1%) - 2-3 times at 5 minutes interval - R after 30 minutes - DOA - 8 hours. - Cycloplegic factor + 0.50 D Tropicamide - (0.5-1%) - 2-3 times at 5 minutes interval. - R after 30 minutes. - DOA - 8 hours - Cycloplegic factor +0.50 D Commonly used Cycloplegics:

12. Atropine Sulphate (0.5 – 1%): - lower strength <5 yrs - <7–10yrs /ciliary spasm Conver.Strabismus - R after 2-3 d. - DOA - 2 wks. - Cycloplegic factor +1.00 D Homatropine Hydrobromide (1 – 2%) - 15 min. interval for 6-8 times. - R after 1 hr - DOA - 2 days. - Cycloplegic factor +0.50 D

13. 1. Observer Factor (working distance) - 1mt = 1D ; 2/3mt = 1.5D 2. Cycloplegic Fac tor (A = 1D ; HA / T / C =0.5D ) Total power – Correction F. = Pat.’s F(RE) e.g, (A at 1mt) RE(PF) = TP – CF(1+1)

14. To simplify the calculation step – o Keep the “Correction Factor lens" in the trial frame before starting Retinoscopy. o At Point of reversal remove this lens = Power of remaining lens is the measure of refraction There by avoiding confusion of calculation.

15. Steps : 1. Subjective verification of refraction. 2. Subjective refinement of refraction. 3. Binocular balancing.

16. Subjective verification of refraction 1. Properly place a trial frame, VA is tested for BE separately 2. Place one of the following lens prescription in the trial frame –(RE /OG /Prev manifest R in case of cat/refractive surgery)  SV of refraction can be performed by – - “ Trial & Error” technique - Fogging technique Pin-hole test– Improves - RE Not improves - Opacity

17. o Trial of different Spherical & Cylindrical lenses. 1. Sphere lenses: - Add +0.25 D and ask- - Which lens makes the letter clearer no.1(original)b. / no.2(+0.25 D)a. / Same? a.Repeat the process (add +0.25D more) - Continue adding increments of +0.25 D sphere until pat. says the two choices are equivalent. b. Subtract -0.25 D sphere and ask which is better no.1(original) or no.4(-0.25D) or they are same Continue subtracting in increment of -0.25 D

18.  2. Cylinder lenses a) Verification of axis: Rotating the cylinder in steps of 5 or 10  When the power of cylindrical lens is small, pat. may have difficulty in deciding at which axis the vision is better. (Stronger cylinder is used to verify the axis).

19. b) Verification of cylinder power  Add +0.25 D cyl in axis of error and ask the pat. which is better - no.1(original)b. / no.2(+0.25 D cyl)a. / same a. Add +0.25 D cyl ;Continue adding +0.25 D cyl until pat says the two choices equivalent. b. Subtract -0.25 D cyl, And ask which is better, no.1(original) or no.3(-0.25 D cyl) or both are same?  Continue subtracting -0.25 D cyl until pat says the two choises are equivalent.

20. 1. Obtain BCVA using spheres, only in one eye, other eye occluded. 2. Fog the eye (make artificially myopic) by putting enough plus sphere lens. - Image ant. to retina, Compound myopic astigmatism

21. 3. Ask the pat to look at Astigmatic dial & identify the “Darkest & Sharpest line”. Say, 3 to 9 ‘o’ clock line i.e, 180` axis line.

22. 4. Add minus cyl in increment of -0.25 DC at axis perpendicular to the sharpest & darkest line (90` in our case) till all lines appear equal. - Vertical Focal line is moved back to Horizontal focal line (Interval of strum’s collapsed)

23. 5. All lines appear equally black – Astig neutralized, - But still are not in perfect focus (blurred) – eye is still fogged. - Switch to distance vision chart – Reduce ‘+’ sphere - Focus is now on retina.

24. 1. Refinement of cylinder 2. Refinement of sphere Always refine first cylinder and then sphere

25. Methods: 1. Jackson’s cross cylinder 2. Astigmatic fan & Maddox V test

26. o To verify the strength and axis of cylinder. o Two cylinders at 90 to each other & of equal strength but of opposite sign. o Commonly +/-0.25 D and +/-0.50 D.

27. 1. Adjust sphere to the most plus or least minus: Fogging - decrease the fog to BCVA The goal (if astigmatism is present) is to place the circle of least diffusion of the conoid of sturm on the retina, thus creating mixed astigmatism 2. Discovering the astigmatism : If no cylindrical correction is present initially - Place cross cylinder at 90 & 180 If no preference is found check at 45 & 135

28. 3. Refinement of the axis: Cross cylinder -0.5D & +0.5D at 45`, ask pat. of any change in VA. No difference – axis is correct. Improves in one direction – Rotate towards plus (for plus cyl) or towards minus (for minus cyl). - repeated several times until neutral point 4. Refinement of Cylinder power: Add +0.25 D & - 0.25 D alternately, ask pat which is clear? No improvement – power is correct Improve in one condition – add +0.25 D (improves in +0.25 D) or add -0.25 D (improves in -0.25 D).  Again check until no improvement is seen

29. o To confirm cylindrical correction. o Astigmatic fan consist of a dial of radiating lines at 10 interval to one another (rising sun) around a central panel carrying a V & two sets of mutually perpendicular lines ( the blocks ). Maddox V test (Fan & Block technique):

30. 1. Obtain BCVA using spheres only puts - circle of least confusion on retina. 2. Add ‘+’ sphere equals to half of estimated astigmatism – simple myopic astigmatism. 3. Show Fan chart & ask which line or group of lines appear clearest & darkest. - Give approx direction of astigmatic error. - To check it – add +0.50 DS (blackest line blurs, if not, add more ‘+’ spheres until they blurs) - In some cases the clearest line will change to 90` = Simple hypermetropic astigmatism (ant focal line near retina). Add more ‘+’ sphere to blur new lines.

31. 4. Ask the pat to see the Maddox arrow, rotate it until both limbs appear equally blurred. 5. Ask the pat to see the Blocks, Add “-” cyl at appropriate axis until second become as clear as first. ( if not possible leave first group of line clearer). - Check again – add +0.50 DS (+0.25 DS if the pat is critical observer) = Both block should blur equally, if not, add more ‘+’ sphere. - If blackest line change over = Astig is over corrected.

32. o Final step in monocular refraction which can be done using – 1. Snellen’s visual acuity chart 2. Duochrome test

33. o Fogging after cylindrical correction o Unfog with increment of +0.25 DS until BCVA is attained. o Doubts may exist at the very end point because the steps from one line to next is rather larger, particularly in smaller letters. o So, verify the best end point or ultimate correction point of spherical component by Duochrome test. Finalizing sphere with Snellen’s chart

34. o Principle: Shorter wavelength are refracted more than longer wavelength. o Pt. is asked to wear red & green glasses & read letters In emmetropic : Green light ant. to retina. Red light post. to retina. - So, Equally sharp. Myopia: Red letters more clear than green. Hypermetropia: Green letters are more clear than red. Duochrome Test:

35. o Procedure: Pt. is slightly fogged- - The letters on red side should appear clearer - Minus sphere in increment of -0.25 D should be added until the letters with red & green back ground appears equally clear o Duochrome test not useful – VA is <6/9

36. o Equalizing accom. effort / Equalization of vision. o Allows both eyes to have the retinal image simultaneously in focus. - Imbalance correction - Asthenopia (b/o unstable accommodation) o Commonly used method are: - 1. Fogging mothod 2. Duochrome test with fogging 3. Prism dissociation method

37. o Place the best corrected lenses in the trial frame. o Fog both eye with +2.00 DS. o Ask pt. to read the Snellen’s chart, obtain the vision (will be approx 6/60 - 6/36). o Place -0.25 DS lens in one eye. o Ask the pat to look at the smallest line which is clear. o Now, alternately & rapidly block each eye by hand & ask by which eye the line is clearer. o Repeat the test in second eye.

38. o If pat says the eye having -0.25 DS is clearer – = eyes are balanced. o If the pat is not able to say by which eye is clearer or both are same then – = Add or subtract 0.25 DS - Until pat is able to differentiate the difference.

39. o Place the best corrected lenses in the trial frame. o Fog one eye with +1.00 DS. o Ask the pat to look at the vision chart with the unfogged eye & ask which color is clearer or brighter? o Repeat the test in other eye. o Add or Subtract 0.25 DS - Until both eyes have the same preference of color either Red or Green.

40. o Place the best corrected lenses in the trial frame. o Both eye fogged with +1.00 DS & vertical prism of 4 or 5 PD is placed before one eye. o Ask the pt. to focus on 6/12 line. o Alternately put a lens of +0.25 DS in front of each eye & ask the pt., which is better? - Image are blurred with +0.25 DS in BE= Eyes are balanced. - no difference - Add or Subtract 0.25 DS, until eyes are balanced.

41. o Once the balance is established, the prism is removed. o Unfog both eyes simultaneously until maximum vision is reached. o Reduce to highest plus or lowest minus sphere. Most sensitive method of binocular balancing.

42.  Usually in opacification of media.  Steps :- 1. Subjective estimation of refractive error. 2. Refinement of subjective refraction. 3. Binocular Balancing. o Step 1 is different. o Steps 2 & 3 are same.

43.  Visual Acuity: Unaided.  Pin – Hole Testing: Provides a useful clue about the potential visual loss.

44. Estimation of Spherical Ametropia : o “Trial & Error” method o Information about the approximate lenses - 1. Nature of visual complaint : o A child of 11 yrs difficulty in seeing the blackboard - Myope. o A man in his late 40s previously good now slight impaired distant vision – Hypermetrope. o An elderly pt. poor retinoscopy reflex b/o cataract – Myopic. 2. Unaided Visual Acuity 3. Previous Glasses

45. Estimation of Astigmatism 1.Astigmatic dial technique 2.Stenopaeic slit test - 1mm Stenopaeic slit. Procedure: o Put corrected spherical glasses in trial frame. o Block one eye & put the stenopaeic slit in the other eye at 180 & ask the pt. to look at the vision chart. o Now ask pt. to say when the image is clear & start rotating the slit in 10 interval o Stop when pt. says its the best-Recheck with 5

46.  Indicated usually after 40 yrs.  Done by using near vision chart – 1. Jaeger’s chart 2. Snellen’s reading test types 3. Number points types standardized by the faculty of ophthalmologist N5 to N48.

47. Procedure 1. Put the trial frame on pt. & block one eye. 2. Ask the pt. to hold the NV chart at 35cm 3. Record acuity accordingly/Rpt. in other eye  In case the near vision is defective the further testing should proceed as follows:

48. 1. Determination of near point of accommodation(NPA) o Near point or punctum proximum o The closest point at which small objects can be seen clearly o Done-near point rule - RAF rule / Prince’s rule Procedure: To determine NPA, a sliding target with 6/9 letters, numbers or fine lines is moved from or towards the eye until the closest point is found at which it still can be seen clearly.

49. 2. Determination of near point of convergence(NPC) o Closest point at which an object can be seen single during bifoveal vision Or o Point at which the two foveal lines of sight intersects when maximum convergence is exerted. Procedure: 1. Put the pt. in primary position, take a sharpened pencil & put it approx 50cm from the pt’s eye. 2. Ask the pt. to look at the tip of the pencil & slowly move the pencil towards pt’s nose.

50. 3. when the pencil tip appears two - measure this distance with a ruler from the lat canthus. 4. Repeat the procedure to recheck (NPC) Other instruments are :- o RAF rule o Livingstone binocular gauge o Prince rule: A bar 24 inches long, ½ inch square – One side- cm; Second side – inches; Third side – Diopters; Fourth side – Age in yrs.

51. 3. Dynamic Retinoscopy:  Implies - procedures performed for near vision with active use of the accom.  Provides an objective basis for optical condition when the pt.is focused for the near vision.  In other words, it is an attempt to give an objective accuracy to measurment of accom.

52. 4. Determination of Near ADD The difference between distance correction & the strength needed for near vision is called the “ADD”  Each pt. should be tested individually (each eye separately)  The near adds should be most serviceable & comfortable (not necessarily clearest) vision for particular work for which the lenses are intended. AGE (in yrs)PRESBYOPIC ADD (in diopters) 45+1.00 - +1.25 50+1.50 - +1.75 55+2.00 - +2.25 60+2.50 - +3.00

53.  Before finally prescribing glasses - we should check for Oculomotor Balance (for distance & near vision).  Also for any :- 1. Heterotropia 2. Heterophoria - type & degree 3. Convergence insufficiency 4. Fusional reserves.

54. GOLDEN RULES

55. 1.A full cycloplegic correction In children having refractive error with asso. manifest deviation.

56. 2.An undercorrection of hypermetropic error To reduce the degree of consecutive exotropia (not at the cost of asthenopic symptom)

57. 3.Slight overcorrection of myopia Helpful in controling - intermittent exotropia.

58. 4.An overcorrection by +1 D to +3 D For amblyopic / as penalization treatment

59. 5.Bifocal Glasses Useful in controlling deviation in pts. having Non refractive accommodative esotropia.

60. 6.In exophoria Both eyes undercorrected by an equal amount of spherical plus power – Induces accom. – accommodative convergence

61. 7.In esophoria Both eyes should be overcorrected Bifocal should be used as a temporary aid to orthoptic treatment aiming to reduce the focal segment as soon as possible.

62. 8.In hyperphoria If feasible lenses of the pt’s optical correction may be decentred to achieve - prismatic effect thus relieving the stress on pt’s vertical vergence control

63. 9.In cyclophoria Best possible efforts should be made to discover & correct the associatded astigmatic refractive error

64. 10.Prism May be needed in phorias: o For exophoria : Base – in prism. o For esophoria : Base – out prism. o In practice, prism are prescribed with apex towards the phoria to correct only half or at the most two-third of total heterophoria.

65. Each frame has two main parts:  A. Front  B. Side piece A. Front: - 1.Rims: Lens support. 2.Bridge: Connection between 2 rims. -Regular / Inset / Saddle bridge 3.Joints 4. Lugs: Side piece are attached. B. Side pieces: - Fixes spectacles to ears.

66.  Ideal material should be:- 1. Non allergic 2. Resistant to corrosion 3. Non flammable 4. In expensive 5. Durable 6. Adjustable  Materials : - Natural material / plastic frames / Nylon supra frame / Metal frames / Combination frames / Rimless mounts.

67.  An ideal lens material : 1. High degree of transparency 2. Good impact resistance 3. Low weight 4. Easy to manufacture & process 5. Good scratch resistance 6. Inexpensive  Materials :- 1. Glass lenses 2. Plastic lenses : Igard / CR – 39 / Zeiss duralet / Polycarbonate / Polyurethane / copolymer / Allyl base.

68.  Flat lenses :- Used in high minus powers. They have got higher degree of aberrations.  Curved lenses -Meniscus lenses -Toric lenses

69.  Geometrical Shape :- 1. Round lenses 2. Oval lenses 3. Pantoscopic round oval (PRO)  Permetric Shape :- 1. Round contour 2. Squarer contour  Upswet shape  Rimless or angular shape  Half eye shapes

70.  Single vision lens :- Used to correct myopia, hypermetropia, astigmatism, presbyopia.  Bifocal lenses  Trifocal lenses  Varifocal lenses  Progressive lenses