Retinoscopy

1. Presenter: Hira Nath Dahal B. Optometry MMC, IOM RETINOSCOPY

2. Presentation Layout Introduction History Theory Procedure Types of retinoscopy Static and dynamic Problems Uses

3. Introduction Objective method of finding out the error of refraction by utilizing the technique of neutralization Based on the fact that when the light is reflected from the mirror into the eye, the direction in which the light will travel across the pupil will depend upon the refractive states of the eye

4. History Sir William Bowman (1859) noticed a peculiar reflex in the pupil of astigmatic eyes that occurred during ophthalmoscopy Cuignet (1873) developed the technique to use the reflex to determine and correct for refractive errors

5. Explanation of optical concept was first attempted by Landolt in 1878 Parent in 1880 began to quantitatively assess the refractive error through the use of lenses inserted in front of the eye

6. Retinoscopy ( “vision of the retina”) : misnomer; was initiated by Parent in 1881 Retinoscopy is actually modification of a Focault knife-edge method for determining the refractive power of the lens applied to the eye

7. Focault knife edge test

8. When the knife edge is in front of the focus, the shadow direction moves the same direction at the knife edge

9. When the knife edge is behind the focus , the shadow moves in the direction opposite to the knife edge

10. When the knife edge is at focus, the light appears and disappears spontaneously

11. Retinoscope small, handheld device that emits visible light toward the pupil of eye being analyzed and allows the operator to view the red reflex of light reflected back through the pupil from the ocular fundus

12. Contd.. Has a reflecting surface, which allows light originating from below to be reflected towards the patients eye The reflecting surface is either perforated or half silvered, which allows the operator to view the patient’s eye through the central aperture

13. Optics of retinoscope The detail optics of retinoscopy can be considered into three stages: Illumination stage Reflex stage Projection stage

14. A divergent beam of light from the filament source is refracted by the plus condensing lens below the reflecting surface, before it is reflected by the perforated or half silvered mirror The reflected rays is usually divergent & is directed towards the patient’s pupil Most retinoscopes now have a control for changing the vergence of emitted light beam such that the vergence of emitted beam can be made significant divergent or convergent

15. Contd.. Divergent beam emitted by retinoscope is considered the incident beam of the optical system underlying retinoscopy The incident beam can be moved back and forth tilting the retinoscope and its reflecting surface

16. Contd.. As the reflecting surface is tilted the apparent source moves in the opposite direction across the line connecting retinoscopic aperture and the eye The divergent incident beam sweeps from one side of the pupil to the other, in the direction of the tilt of the reflecting surface & the beam that enters the pupil sweeps across the retina in that direction as well

17. Blur patch in the retina moves in the same direction as the mirror (plane mirror position)

18. Plane mirror VS concave mirror

19. Clinician S o S 1 S 2 Patient Optical principles The light in the pupil is called the “ret reflex”

20. Origin of retinoscopic reflex Still in controversy; Junction between the retina and vitreous (most acceptable) From the Bruch’s membrane – not accepted as RPE absorbs the light For subjective refraction: Layer of photoreceptors is considered Retinoscope indicates higher hyperopia or less myopia Called as plus bias in retinoscopy

21. Charcterstics of retinoscopic reflex Brightness Light focused at aperture in emmetrope or at neutrality –bright reflex. Focused sufficiently in front or behind the aperture in ammetrope – relatively dull reflex. large errors have dull reflex, small errors have a bright reflex . Dimmer reflex- smaller pupil (hyperopes and elderly) darkly pigmented RPE media opacities.

22. Speed of reflex When WD constant, relative speed of reflex depends on eye’s residual ammetropia . Speed less than half – ammetropia more than 3.00DS from neutrality. Speed 3 times – 0.50DS from neutrality. Speed 6 times – 0.25DS from neutrality. Speed infinity at neutrality, so pupil seems covered with reflex.

23. Width Streak narrow when you are far from far point Broadens as you approach far point

24. Ret reflex can tell us a lot Reflex Observation Meaning Brightness Dim Far from Rx Bright Close to Rx Streak size Narrow Far from Rx Wide Close to Rx Movement direction With Need more plus Against Need more minus Movement speed Slow Far from Rx Fast Close to Rx

25. There are mainly two kinds of retinoscopy: Static retinoscopy and Dynamic retinoscopy

26. Static retinoscopy Objective of static retinoscopy is to find the position of the far point (punctum remotum) of the eye Far point is the point that is optically conjugate to the fovea when accommodation is relaxed

27. Contd.. Far point of the emmetropic eye is located at the peephole of the retinoscope Far point of the myopic eye is located in front of, or anterior to the eye along the line of sight

28. Contd.. In case of a hyperopic eye far point is located behind or posterior to the eye Paraxial light that converges towards a focus in the plane of the far point focuses at the retina & light diverging from a hyperopic retina exits the eye as if it is diverging from a plane containing far point In case of astigmatism, retinoscopy finds two far points one for each of the two primary power meridians

29. In case of emmetropic eye all the rays from the light source from the retina will enter the clinician’s pupil and the entire pupil of the patient will appear to be illuminated . It signifies that the clinician’s pupil is conjugate to the patient’s retina

30. Reflex stage: neutral Clinician Patient No effect on reflex Reflex disappears Mirror tilts forwards Mirror tilts further forwards S 2 S 2 No S 2 S 1 Neutral position : Far point conjugate with observers nodal point. No movement of reflex , sudden change from red reflex to no reflex.

31. As in low myopia, the light rays emerging from the illuminated spot of the fundus are convergent and meet behind the observer, sitting at 50cm from the patient

32. Observer Subject Reflex disappears Reflex moves down , i.e. with direction of movement of light Mirror tilts further forwards Mirror tilts forwards S 2 S 2 Far point behind observers pupil Within pupil Outside pupil No S 2 S 1 With movement Far point behind observers pupil . With movement of reflex , gradual change from red reflex to no reflex

33. In high myopia, light emerging out of the patient’s eyes from the illuminated spot on the fundus are convergent and meet at the space between the patient and the observer

34. Observer Subject Far point in front of observers pupil Reflex disappears Reflex moves up , i.e. against direction of movement of light Mirror tilts forwards Mirror tilts further forwards S 2 S 2 Within pupil Outside pupil No S 2 S 1 Against movement Far point in front of observers pupil . Against movement of reflex , gradual change from red reflex to no reflex

35. In hypermetropia the light rays emerging out of the eye from the illuminated spot of the fundus are divergent

36. Degree of ametropia and the reflex As subject becomes more myopic, the cone of light becomes wider Greater portion of light falls outside of practitioner’s pupil, so dimmer reflex 1 2

37. "with" motion of the pupillary streak reflex-as compared with movement of the incident divergent beam indicates a far point location behind the retinoscope aperture, in the continuum between the operator and infinity (slightly myopic and emmetropic eyes) or behind the eye (hyperopic eyes). "Against" motion of the streak indicates a far point location between the retinoscope aperture and the patient's eye (moderately to highly myopic eyes).

38. If the retinoscopic reflex is at neutrality-showing neither "with" nor "against" motion-the far point is located at the aperture of the retinoscope.

39. Types of retinoscope Reflecting (mirror retinoscope): A source of light is required when using mirror retinoscope, which is kept above and behind the head of the patient May consists of a single plane mirror or the combination of plane and concave mirrors (Priestley-Smith’s mirror)

40. 2. Self illuminated retinoscope: more popular now a days two types are available: Spot retinoscope Streak retinoscope

41. Spot Vs Streak The “spot retinoscope” reflects a beam of light from a circular source, whereas the “streak retinoscope” emits a beam from a line source Of these two major forms of retinoscope, the streak retinoscope is more useful clinically because it can be more readily applied to the determination of astigmatic corrections by assessment of the axis of cylinder and refractive powers in the two primary ametropic meridians

42. Procedure

43. Observations Depending upon the movement of the red reflex (when a plane mirror retinoscope is used at the distance of 50cm), the result are interpreted as follows: No movement of red reflex indicates myopia of 2.00D The movement of red reflex along with the movement of the retinoscope indicates either emmetropia of hypermetropia or myopia less than 2.00D The movement of red reflex against the movement of the retinoscope implies myopia more than 2.00D

44. With movement

45. Against movement

46. Neutralization point

47. Neutralization To estimate the degree of refractive error, the movement of red reflex is neutralized by addition of increasingly convex (+) spherical lenses (when the red reflex was moving with the movement of plane mirror) Or concave (-) spherical lenses (when the red reflex was moving against the movement of plane mirror)

48. When simple spherical error alone is present, the movement of red reflex will be neutralized in both vertical and horizontal meridian In the presence of astigmatism, with its principal axis horizontal and vertical, one axis is neutralized with the appropriate spherical lens and the second axis (vertical or horizontal) still shows the movement of reflex in the direction of the axis of the astigmatism

49. End point: When streak retinoscopy is performed, the width of the reflex widens progressively as the neutralization is approached, and at the end point, streak disappears and the pupil appears completely illuminated or completely dark

50. Confirm / identify the axis of the astigmatism The Thickness Phenomenon The Intensity Phenomenon The Break and Skew Phenomena Straddling the Axis

51. The thickness phenomena The streak reflex appears to be narrowest when we are streaking the meridian of the correct axis.  As we move away from the correct axis,  the streak reflex becomes wider.

52. The Intensity Phenomenon The streak reflex appears brightest when you are streaking the meridian of the correct axis.  As you move away from the correct axis,  the streak reflex becomes more dim.

53. In higher amounts of astigmatism, the streak reflex will tend to stay on-axis even if the streak is rotated off-axis, this guides you back to the correct axis . Break phenomenon

54. Straddling the cylinder axis Introduced by Copeland – finding and bracketing astigmatic axis Rotate the retinoscopy streak such that it becomes align 45 degrees oblique to the axis of correcting cylinder, to either side Compare the speed of rotation and alignment of fundus reflex streak with correcting cylinder axis If not align fundus reflex streak would be misaligned in one of the 45 degree position

55. Clinician S 2 Patient Working distance neutrality negative vergence is introduced due to our working distance (WD) = 1/d (m) Where d = distance in m, measured between your ret and patient’s eye added lenses To get the right prescription we need to compensate Rx = lens power – 1/d So to get neutral, we needed: lens power = Rx + 1/d

56. Working distance compensation Calculation For example, if neutrality is achieved with a +3.00DS lens and your working distance is 50cm Rx = +3.00DS – (1/0.50) = +3.00 – 2.00 =+1.00DS Rx = lens power - 1/d

57. Potential errors Variations in WD. False neutrality When the beam is made convergent by collar sometimes the focus lies apparently at the aperture before the reversal of the streak. Full fundus glow is achieved regardless of the residual ammetropia .

58. Scissors (fish mouth) reflex Due to large pupil diameter (aberrations) Irregular astigmatism Irregular retina Tilted lens Corneal scar Neutralized by lens that provides more or less equal thickness and brightness to the opposing reflex

59. Scissors movement

60. Contd.. Obliquity of observation As observer is slightly temporal there’s residual oblique astigmatism induced Error is 0.12DC@ 90 if 5 degree 0.37DC@ 90 if 10 deg; 0.75DC@ 90 if 15 deg; & 1.37DC @ 90 if 20 deg oblique

61. Accommodative status Plus bias: hyperopia of +0.25 to +0.50 in youthful eyes is seen. Is due to effective reflecting surface being behind the outer limiting membrane. also due to spectral composition of fundus reflex. Contd..

62. 66 When retinoscopy is used to test accommodation for near objects, it is called dynamic retinoscopy The patient views a nearpoint test card at a typical nearpoint working distance, e.g., 40 cm. This establishes a known accommodative stimulus Dynamic Retinoscopy

63. 67 Lag of accommodation can be assessed clinically using various retinoscopic procedures. Lag of accommodation= Acc m response < Acc m stimulus Normal Lag: +0.50 or +0.75 diopters High Lag: +1.00 diopters or higher Lead : +0.25 diopters or less

64. 68 To investigate the accommodative state of the eye in near vision . There are two different techniques: The patient observes a separate fixation object with the retinoscope behind it. The distance between the object and retinoscope at reversal indicates the accuracy of accommodation. Types of Dynamic Retinoscopy

65. The fixation object is on the retinoscope, the level of accommodation being measured by trial lenses placed before the eyes. In both techniques the patient wears the distance correction as found by the subjective.

66. Cross-Nott’s technique Doesn’t require the use of supplementary lenses Pt wears first the distance refractive correction, and is directed to view the near target If the with movement is seen (reflecting the typical lag of accommodation), then the retinoscopist adjusts the working distance away from the patient, while the fixation target remains stationary The reciprocal of the retinoscopy WD (in metres ) at which the neutral reflex is observed indicates the magnitude of accommodative response

67. Sheard’s technique He indicated that lag of accomodation could measured by placing a target which is attached to the retinoscope mirror at the patient's usual reading distance, an performing retinoscopy at that distance Appropriate spherical lenses are added until the neutral reflex is observed Stated that the lag of accomodation is given by the lens power which provides “the first indication of neutral shadow”

68. 72 dynamic retinoscopy method using lenses, the stimulus to accommodation is altered by the presence of the trial lenses. the patient also binocularly fixates a stimulus mounted on the retinoscope. The target is a set of letters on the retinoscope or a card attached to the retinoscope MEM Retinoscopy

69. a single lens is briefly held in front of one eye and the beam passed across. The method is applied to one eye at a time. The lens giving reversal gives the value of the low neutral.

70. RADICAL RETINOSCOPY Due to small pupils/cataract/other media opacities/faint retinoscopic reflex The practitioner find easy as moving closer to the patient. Involve a WD as close as 20 cm/or even 10cm. Eg : if possible at 20 cm WD then +5.00D is subtracted from lens power in the refractor.

71. STATIC Vs DYNAMIC Accomodation fully relaxed . Working distance lens added or subtracted from the objective finding . Fixates letters at 6m . Only ametropia or emmetropia can be determined. Accomodation fully in play . No influence of working distance . Fixates at the bulb of retinoscope or letters clinged on it . Accommodative lag can be determined.

72. Uses Objective measurement of refractive error Evaluation of refractive state in nonverbal patients and also in low vision patients Regularly used in laboratory for measurement of refractive status in animals Starting point for subjective refraction

73. Used to prescribe where subjective refraction can’t be performed Screening for ocular disease Keratoconus , media opacities Also useful in determining accomodative stability and accomodative lag

74. THANK YOU!!