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Retinoscopy and its
principles
Presenter : Dr.Rasika Thakur
Moderator: Dr.Monica Samant
Mr.Kunal Kishor
Introduction
History
Types of retinoscope
Far point
Optical principle
Types of retinoscopy
Problems in retinoscopy
Introduction
An accurate objective measurement of the refractive
state of an eye can be made using the retinoscope
The technique is called retinoscopy
Pupilloscopy, shadowscopy, skiascopy,
umbrascopy, scotoscopy
History
• 1873,F.Cuigent the father of retinoscopy- first
described a retinoscope
1878, M. Mengin
1880, H. Parent - retinoscopie
• 1927, Copeland -streak retinoscope
Types of retinoscopes
Reflecting mirror retinoscope
• A perforated mirror by which the beam is reflected in to
the patients eye and through a central hole the emergent
rays enter the observer’s eye
• Movements of the illuminated retinal area are produced
by tilting a mirror, either a plane or concave
Reflecting mirror retinoscope
Reflecting mirror retinoscope
contd…
Self illuminated retinoscope
• The light source and the mirror are
incorporated in one
• STREAK RETINOSCOPE- Light source is
a linear (uncoiled) filament
Streak Retinoscope
Projecting system
Main purpose:
To illuminates the retina
Contsists of:
• Light source
• Condensing lens
• Mirror
• Focusing sleeve
• Current source
Projecting system of Copeland
type.
Projecting system of Welch Allyn
.
....
.
Observation system
Main purpose:
To allows the observer to see the retinal reflex of the
patient.
Streak Retinoscope
Advantages of Streak Retinoscope
over Spot Retinoscope
Far point
• The far point of eye is defined as the point in space that is
conjugate with the fovea when accomodation is relaxed
Far point contd…
Optical Principle
• Retinoscope works on Focault's principle
• Retinoscopy is based on the fact that when light is
reflected from a mirror into the eye, the direction in which
the light will travel across the pupil will depend upon the
refractive state of the eye
Optical Principle
• The illumination stage
• The reflex stage
• The projection stage
Illumination Stage
Light is directed into the patient's eye to
illuminate the retina
Reflex Stage
An image of the
illuminated retina is
formed at the
patient's far-point
Exercises in Refractometry.
Thorofare, NJ: SLACK Incorporated; 1990
Projection Stage
The image at the far-point is located by
moving the illumination across the fundus
and noting the behaviour of the luminous
reflex seen by the observer in the patient's
pupil
Emmetropic eye
Hypermetropic eye
Myopia of less than 1D
Myopia of 1D
Myopia of more than 1D
Projection Stage
Working Distance
• The distance from the retinoscope to the patient’s eye
• D = 1 ÷ F
• The length of the average person’s arm is 66 cm.
The power of a lens that focuses parallel light rays
at 66 cm is +1.50 D
Should I use a “working lens” to
compensate for the working distance?
Advantages-
Instant identification of myope or hyperope.
Working lens might help relax accommodation.
No need for mental arithmetic to allow for working
distance
Disadvantages-
Too much blur does not necessarily relax
accommodation.
Working lens adds extra reflections to the view.
Formation of the Secondary Fundus
Source or "Fundus Reflex"
• Light reflected from the fundus has two components:
• A diffuse component, which is also called backscatter
• A directed component
Fundal reflex
Properties of the fundal reflex indicate the refractive status
of the eye
• Brightness
• direction of motion
• speed of motion
• Width
Brightness of the Retinoscopic
Fundus Reflex
The brightness of the
fundus reflex is greatest
when the retinoscope
aperture coincides with
the far point of the eye
In highly myopic and
highly hyperopic eye the
pupillary reflex appears
dim
Direction of Motion of the Retinoscopic
Fundus Reflex
No movement of red reflex indicates myopia
of 1D
Contd..
• Red reflex moves along with the movement of the
retinoscope, it indicate emmetropia or hypermetropia or
myopia of less than 1D.
Contd..
• A movement of red reflex against the movement
of the retinoscope, indicates myopia of more than
1D.
Speed and width of the Retinoscopic
Fundus Reflex
• Indicates that how far we are from neutrality
• A slow moving streak reflex - long way from neutrality.
Finding the cylinder axis
• In the presence of astigmatism, one axis
is neutralized with the spherical lens &
the second axis still shows the
movement of reflex in the direction of
axis of astigmatism
Finding the cylinder axis
Break
Break in the alignment
between the reflex in the
pupil and the band outside it
is observed when the streak
is not parallel to one of the
meridian
Finding the cylinder axis
Skew
if the streak is not
aligned with the true
axis oblique motion of
streak reflex will be
observed on
movement of the
steak.
Straddling
CONFIRMATION OF THE AXIS
•This is performed with approximately correct cylinder in place
Finding the cylinder power
3 Methods-
With two spheres
With a sphere and cylinder
With two cylinders
With two spheres
First neutralize one axis with appropriate sphere
Then keep on changing the sphere till the second axis
is neutralized
Astigmatism is measured by the difference between
the 2 spheres
+2.00D
+3.00D
+ 2.00Ds / + 1.00 Dc X 900
With a sphere and cylinder
First neutralize one axis with an appropriate spherical
lens.
Neutralize the other axis with a cylindrical lens at the
appropriate orientation
 The spherical cylindrical gross retinoscopy may be
read directly from the trial lens apparatus
Enhancement
This technique is to approximately estimate the amount
of refractive error with minimal use of trial lenses.
If the reflex inside pupil gets more thinner by changing
the sleeve width,it suggests a significant refractive error
Thinnest retinal reflex is called Enhanced band
Enhancement
A rough estimation of the refractive error is
possible,based on the sleeve position
End point of retinoscopy
Types of retinoscopy
• Static Retinoscopy: the patient is looking at a distant
object, with accommodation relaxed.
• Dynamic retinoscopy: the patient is looking at a
near object, with accommodation active.
• Near retinoscopy: the patient is looking at a near
object, with accomodation relaxed
Dynamic Retinoscopy Techniques
MEM Retinoscopy
Help to calculate patients lag or lead
of accomodation
Lettered targets are applied to the head of a
retinoscope
Fixation target is placed at harmon distance/50 cm
with patients corrected refractive error
the refractive power of the trial lens that brings
neutrality is the accommodative lag/lead
Nott’s method
It determines lag/lead of accomodation by moving
retinoscopic apperture towards or away from the eye
Target is the letters around the aperture of a near point card
At a distance of 40 cm
The accommodative response, in diopters, is subtracted from
the accommodative demand,to determine the accommodative
lag/lead
Bell Retinoscopy
The retinoscope remains in
a fixed position and the target is moved
The retinoscopy is performed from a fixed
distance of 50 cm
The distance between the retinoscope and the
target when the change in motion occurs is a
physical measure of the lag/lead of
accommodation
Near retinoscopy /Mohindra
retinoscopy
Also known as near monocular retinoscopy
Estimate the refractive status of the eye
The stimulus or fixation is the dimmed light source
of the retinoscope in a darkened room
The retinoscope is held at a distance of 50cm with
hand-held trial lenses
Borish's Clinical Refraction. 1998. WJ Benjamin. WB Saunders Company.
Philadelphia, London, Toronto.
Radical retinoscopy
Done in patients with small pupils, cataract, or any
other opacity
Working distance here is 20cm or even less upto 10cm
Chromoretinoscopy
Helps in a clinical measurement of the chromatic
aberration of an eye
Transmittance filters with selected dominant
wavelengths, are placed in the light path between the
light source of a retinoscope and the retinoscopist's
eye
Types of retinoscopy
• Wet retinoscopy- with cycloplegic retinoscopy is
performed
• Dry retinoscopy-without cycloplegic
Indications for wet retinoscopy
Accommodative fluctuations indicated by a
fluctuating pupil size and/or reflex during retinoscopy
Patients with esotropia or convergence excess
esophoria
A retinoscopy result significantly more positive or
minus (>1.00 DS) than the subjective result
cycloplegic drugs used in wet
retinoscopy
 Atropine sulphate 1%
Cyclopentolate 1%
Homatropin 2%
Disadvantages of cycloplegic
retinoscopy
Temporary symptoms of blurred vision and
photophobia
The degradation of vision is caused by the abolition of
the accommodation response
Increase in ocular aberrations as a result of dilated
pupils.
Adverse effects and allergic reactions to
cyclopentolate are rare
Problems in retinoscopy
• Red reflex may not be visible -small pupil, hazy
media & high degree of refractive error
• Scissoring shadow-may be seen in healthy cornea
but with unusual difference in curvature in the
centre & the corneal opacities
contd
Patient with strabismus-it is easier to change the
fixation of good eye so that retinoscopy can be
performed along the visual axis of the strabismic eye
Retinoscopy in nuclear cataract shows index myopia
in early stages
contd
• Spherical aberrations -lead to variation of refraction in the
centre & periphery of pupil. It may be seen in normal eyes
but more marked in lenticular sclerosis.
• Conflicting shadows- moving in various directions in
different parts of the pupillary area with irregular
astigmatism
• Triangular shadow- may be observed in patients with
conical cornea
Non-refractive uses of
retinoscopy
Opacities in the lens and iris -dark areas against the
red background
Extensive transillumination defects in uveitis or
pigment dispersion syndrome -bright radial streaks
on the iris
Keratoconus distorts the reflex and produces a
swirling motion
contd
Retinal detachment involving the central area will
distort the reflecting surface and a grey reflex is seen
A tight soft contact lens will have apical clearance in
the central area which will cause distortion of the
reflex
Reason for false reading
Inexperience
 Not aligning with Visual axis of the patient
Definite working distance is not maintained
Lack of subject’s accommodation
Defect in trial lenses
Lack of patient’s co-ordination
Thankyou

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Retinoscopy and its principles

  • 1. Retinoscopy and its principles Presenter : Dr.Rasika Thakur Moderator: Dr.Monica Samant Mr.Kunal Kishor
  • 2. Introduction History Types of retinoscope Far point Optical principle Types of retinoscopy Problems in retinoscopy
  • 3. Introduction An accurate objective measurement of the refractive state of an eye can be made using the retinoscope The technique is called retinoscopy Pupilloscopy, shadowscopy, skiascopy, umbrascopy, scotoscopy
  • 4. History • 1873,F.Cuigent the father of retinoscopy- first described a retinoscope 1878, M. Mengin 1880, H. Parent - retinoscopie • 1927, Copeland -streak retinoscope
  • 6. Reflecting mirror retinoscope • A perforated mirror by which the beam is reflected in to the patients eye and through a central hole the emergent rays enter the observer’s eye • Movements of the illuminated retinal area are produced by tilting a mirror, either a plane or concave
  • 9. Self illuminated retinoscope • The light source and the mirror are incorporated in one • STREAK RETINOSCOPE- Light source is a linear (uncoiled) filament
  • 11. Projecting system Main purpose: To illuminates the retina Contsists of: • Light source • Condensing lens • Mirror • Focusing sleeve • Current source
  • 12. Projecting system of Copeland type.
  • 13. Projecting system of Welch Allyn . .... .
  • 14. Observation system Main purpose: To allows the observer to see the retinal reflex of the patient.
  • 16. Advantages of Streak Retinoscope over Spot Retinoscope
  • 17. Far point • The far point of eye is defined as the point in space that is conjugate with the fovea when accomodation is relaxed
  • 19. Optical Principle • Retinoscope works on Focault's principle • Retinoscopy is based on the fact that when light is reflected from a mirror into the eye, the direction in which the light will travel across the pupil will depend upon the refractive state of the eye
  • 20. Optical Principle • The illumination stage • The reflex stage • The projection stage
  • 21. Illumination Stage Light is directed into the patient's eye to illuminate the retina
  • 22. Reflex Stage An image of the illuminated retina is formed at the patient's far-point Exercises in Refractometry. Thorofare, NJ: SLACK Incorporated; 1990
  • 23. Projection Stage The image at the far-point is located by moving the illumination across the fundus and noting the behaviour of the luminous reflex seen by the observer in the patient's pupil
  • 26. Myopia of less than 1D
  • 28. Myopia of more than 1D
  • 30. Working Distance • The distance from the retinoscope to the patient’s eye • D = 1 ÷ F • The length of the average person’s arm is 66 cm. The power of a lens that focuses parallel light rays at 66 cm is +1.50 D
  • 31. Should I use a “working lens” to compensate for the working distance? Advantages- Instant identification of myope or hyperope. Working lens might help relax accommodation. No need for mental arithmetic to allow for working distance Disadvantages- Too much blur does not necessarily relax accommodation. Working lens adds extra reflections to the view.
  • 32. Formation of the Secondary Fundus Source or "Fundus Reflex" • Light reflected from the fundus has two components: • A diffuse component, which is also called backscatter • A directed component
  • 33. Fundal reflex Properties of the fundal reflex indicate the refractive status of the eye • Brightness • direction of motion • speed of motion • Width
  • 34. Brightness of the Retinoscopic Fundus Reflex The brightness of the fundus reflex is greatest when the retinoscope aperture coincides with the far point of the eye In highly myopic and highly hyperopic eye the pupillary reflex appears dim
  • 35. Direction of Motion of the Retinoscopic Fundus Reflex No movement of red reflex indicates myopia of 1D
  • 36. Contd.. • Red reflex moves along with the movement of the retinoscope, it indicate emmetropia or hypermetropia or myopia of less than 1D.
  • 37. Contd.. • A movement of red reflex against the movement of the retinoscope, indicates myopia of more than 1D.
  • 38. Speed and width of the Retinoscopic Fundus Reflex • Indicates that how far we are from neutrality • A slow moving streak reflex - long way from neutrality.
  • 39. Finding the cylinder axis • In the presence of astigmatism, one axis is neutralized with the spherical lens & the second axis still shows the movement of reflex in the direction of axis of astigmatism
  • 40. Finding the cylinder axis Break Break in the alignment between the reflex in the pupil and the band outside it is observed when the streak is not parallel to one of the meridian
  • 41. Finding the cylinder axis Skew if the streak is not aligned with the true axis oblique motion of streak reflex will be observed on movement of the steak.
  • 42. Straddling CONFIRMATION OF THE AXIS •This is performed with approximately correct cylinder in place
  • 43. Finding the cylinder power 3 Methods- With two spheres With a sphere and cylinder With two cylinders
  • 44. With two spheres First neutralize one axis with appropriate sphere Then keep on changing the sphere till the second axis is neutralized Astigmatism is measured by the difference between the 2 spheres +2.00D +3.00D + 2.00Ds / + 1.00 Dc X 900
  • 45. With a sphere and cylinder First neutralize one axis with an appropriate spherical lens. Neutralize the other axis with a cylindrical lens at the appropriate orientation  The spherical cylindrical gross retinoscopy may be read directly from the trial lens apparatus
  • 46. Enhancement This technique is to approximately estimate the amount of refractive error with minimal use of trial lenses. If the reflex inside pupil gets more thinner by changing the sleeve width,it suggests a significant refractive error Thinnest retinal reflex is called Enhanced band
  • 47. Enhancement A rough estimation of the refractive error is possible,based on the sleeve position
  • 48. End point of retinoscopy
  • 49. Types of retinoscopy • Static Retinoscopy: the patient is looking at a distant object, with accommodation relaxed. • Dynamic retinoscopy: the patient is looking at a near object, with accommodation active. • Near retinoscopy: the patient is looking at a near object, with accomodation relaxed
  • 51. MEM Retinoscopy Help to calculate patients lag or lead of accomodation Lettered targets are applied to the head of a retinoscope Fixation target is placed at harmon distance/50 cm with patients corrected refractive error the refractive power of the trial lens that brings neutrality is the accommodative lag/lead
  • 52. Nott’s method It determines lag/lead of accomodation by moving retinoscopic apperture towards or away from the eye Target is the letters around the aperture of a near point card At a distance of 40 cm The accommodative response, in diopters, is subtracted from the accommodative demand,to determine the accommodative lag/lead
  • 53. Bell Retinoscopy The retinoscope remains in a fixed position and the target is moved The retinoscopy is performed from a fixed distance of 50 cm The distance between the retinoscope and the target when the change in motion occurs is a physical measure of the lag/lead of accommodation
  • 54. Near retinoscopy /Mohindra retinoscopy Also known as near monocular retinoscopy Estimate the refractive status of the eye The stimulus or fixation is the dimmed light source of the retinoscope in a darkened room The retinoscope is held at a distance of 50cm with hand-held trial lenses Borish's Clinical Refraction. 1998. WJ Benjamin. WB Saunders Company. Philadelphia, London, Toronto.
  • 55. Radical retinoscopy Done in patients with small pupils, cataract, or any other opacity Working distance here is 20cm or even less upto 10cm
  • 56. Chromoretinoscopy Helps in a clinical measurement of the chromatic aberration of an eye Transmittance filters with selected dominant wavelengths, are placed in the light path between the light source of a retinoscope and the retinoscopist's eye
  • 57. Types of retinoscopy • Wet retinoscopy- with cycloplegic retinoscopy is performed • Dry retinoscopy-without cycloplegic
  • 58. Indications for wet retinoscopy Accommodative fluctuations indicated by a fluctuating pupil size and/or reflex during retinoscopy Patients with esotropia or convergence excess esophoria A retinoscopy result significantly more positive or minus (>1.00 DS) than the subjective result
  • 59. cycloplegic drugs used in wet retinoscopy  Atropine sulphate 1% Cyclopentolate 1% Homatropin 2%
  • 60. Disadvantages of cycloplegic retinoscopy Temporary symptoms of blurred vision and photophobia The degradation of vision is caused by the abolition of the accommodation response Increase in ocular aberrations as a result of dilated pupils. Adverse effects and allergic reactions to cyclopentolate are rare
  • 61. Problems in retinoscopy • Red reflex may not be visible -small pupil, hazy media & high degree of refractive error • Scissoring shadow-may be seen in healthy cornea but with unusual difference in curvature in the centre & the corneal opacities
  • 62. contd Patient with strabismus-it is easier to change the fixation of good eye so that retinoscopy can be performed along the visual axis of the strabismic eye Retinoscopy in nuclear cataract shows index myopia in early stages
  • 63. contd • Spherical aberrations -lead to variation of refraction in the centre & periphery of pupil. It may be seen in normal eyes but more marked in lenticular sclerosis. • Conflicting shadows- moving in various directions in different parts of the pupillary area with irregular astigmatism • Triangular shadow- may be observed in patients with conical cornea
  • 64. Non-refractive uses of retinoscopy Opacities in the lens and iris -dark areas against the red background Extensive transillumination defects in uveitis or pigment dispersion syndrome -bright radial streaks on the iris Keratoconus distorts the reflex and produces a swirling motion
  • 65. contd Retinal detachment involving the central area will distort the reflecting surface and a grey reflex is seen A tight soft contact lens will have apical clearance in the central area which will cause distortion of the reflex
  • 66. Reason for false reading Inexperience  Not aligning with Visual axis of the patient Definite working distance is not maintained Lack of subject’s accommodation Defect in trial lenses Lack of patient’s co-ordination

Editor's Notes

  1. The term "objective refraction" is used when the refractive error of an eye is determined without input by the patient Retinoscopy is a form of objective refraction in which the judgment of a human operator is required to determine the refractive error Retinoscopy can be performed on infants, the mentally infirm, low-vision patients, and uncooperative or malingering patients.
  2. 1902 Jack C. Copeland was studying astigmatic reflexes with Wolff’s spot retinoscope, when he dropped the instrument on floor, damaging the bulb filament
  3. SPOT RETINOSCOPE- Light source is a small coiled filament
  4. The hole should be pierced and not to be formed by a defect in silvering of an in perforated mirror as the glass reflects an appreciable fraction of light,which should enter the eye. If it is pierced ,annoying reflexes may be formed at edges but these are avoided if the sides of the hole are blackened ,& are made widen out posteriorly so that it is narrowest at the mirror end.
  5. SPOT RETINOSCOPE- Light source is a small coiled filament
  6. Plano mirror effect: The light rays emanating from the retinoscope are slightly divergent and movement of the retinoscope downwards makes the image of the filament move upwards. Concave mirror effect: By using a concave mirror of focal length less than the distance between the patient and the observer and close to the patients eye, a real image of the light source is formed between the patient and the observer close to the patients eye. This image acts as a bright light source for illuminating the patients retina and there fore the illumination moves in the opposite direction to the plan mirror.
  7. Usual method of vergence control (lens is fixed). Copeland type Mechanism that controls the width of the streak also allows to switch between plane mirror and concave mirror. Copeland streak retinoscope: All the way up, plane mirror is in position with a wide streak.As it is lowered gradually , the streak decreases in width. And widens again.At the lowest adjustment the streak is again at its maximum width but with concave mirror effect.
  8. Alternative method ergence control (bulb is fixed). We.lch Allyn type American Optical and Welch Allyn: These instruments are in plane mirror mode when the mechanism is all the down rather than all the way up
  9.  Enhancement of hyperopia by raising the sleeve. Enhancement is one technique that combines changing in the illuminating system with properties of the viewing system. In hyperopic eyes, it is possible to narrow the beam on the retina sufficiently so that its borders can be seen despite the magnification (cross-hatched) of the viewing system. The amount that the sleeve is moved and the width of the facial intercept permit estimation of the amount of hyperopia. Moreover, meridional comparison is the basis for detection of hyperopic astigmatism.
  10. What the Patient Needs to Know- The retinoscope helps determine your glasses prescription Just keep both eyes open and look at the letters on the chart, even if they are blur Do not look at the light You can blink whenever you need to Let me know if I block your view of the letters
  11. PRE-REQUISITES- Semi-dark Room Trial set Lens Rack Trial Frame Phoropter or Refractor Fixating targets [distance & near charts, illuminating source etc.]
  12. A light source was located beside the patient's head, and light reflected into the patient's eye from a plane or concave mirror held by the observer. The observer viewed the patient's eye through a small hole in the mirror. The electric retinoscope has largely replaced this system. However, the principles and nomenclature have remained unchanged. When a plane mirror is used, light is moved across the patient's fundus from A to B by rotating the plane mirror from M1 to M2. Note that the illuminating rays move in the same direction as the mirror. A concave mirror of focal length less than the distance between patient and observer is occasionally used for retinoscopy. A real image of the light source is formed
  13. A ray from point A of the retina R on the principal axis of the eye, which leaves the eye along the principal axis. (2) A ray from a retinal point B, off the principal axis, which travels parallel to the principal axis as far as the principal plane, P, of the eye, where it is refracted to pass onward through the anterior principal focus, Fa, of the eye. A ray from retinal point B which passes undeviated through the nodal point, N.
  14. The observer views the image A1B1 of the illuminated retina AB from a convenient distance, usually m. Figure 14.22 depicts this and is constructed by drawing Fig. 14.21 and adding a hypothetical ray from point B1 passing through the observer's nodal point, No, to the observer's retina, Ro. This ray locates the point Bo, the image of B1 on the observer's retina, and allows completion of the diagram. The observer does not see the actual image A1B1, but rays from A1B1 are seen as an illuminated area or reflex in the patient's pupil. In hypermetropia the luminous reflex seen in the patient's pupil moves in the same direction as the illuminating light – a 'with' movement, indicated by the arrows in Fig. 14.22. Once again a 'with' movement is observed. When the patient's myopia is less than the dioptric value of the observer's working distance a 'with' movement is still obtained.
  15. This is the distance at which the eye is focused when the reflex has been neutralized (you remember that D = 1 ÷ F, right?). In other words, the eye on which you just performed retinoscopy has 1.50 D of plus-powered sphere more than it needs (unless you want to measure visual acuity at 66 cm” If the distance is between 54 and 61 cm, use 1.75 D as your working lens. Those with a working distance between 62 and 72 cm should use 1.50 D To allow the eye to focus at 20 feet (6 m), this power must be taken away from the gross retinoscopy result. This is done by dialing 1.50 D toward the minus, also known as “removing the working lens’’ “Retinoscopy lens” built into most refractors; the lens is inserted prior to performing retinoscopy and simply removed at the completion
  16. a diffuse component, which is also called backscatter, the result of light scattered because of reflection from microscopic and macroscopic particles or structures within the volume of the retina, the pigment epithelium, the choroid, or even the sclera A directed component, the result of light that has been reflected from the neighborhood of the retina/pigmented epithelium interface and is waveguided by the retinal cones
  17. The streak reflex is a diffuse reflection of light from the illuminated fundus: an elongated patch of fundus that becomes the illuminated object for refraction out of the eye.
  18. the reflected light that exits the pupil has a focal point that lies in front of the eye, as in a myopic primary meridian, or a virtual focal point that lies in back of the eye, as in a hyperopic primary meridian At neutrality, the retinoscopic refractive endpoint is reached when the focal point-or far point-has been moved to coincide with the aperture of the retinoscope The brightness of the fundus reflex is greatest when the retinoscope aperture coincides with the far point of the eye. Nearly all of the light making up the fundus image enters the pupil of the retinoscopist's eye. According to the inverse-square law, when the retinoscope aperture and the far point do not coincide, only a portion of the wavefronts will enter the retinoscope aperture to be collected by the retinoscopist's eye
  19. With movement-it indicated that the far point was behind the retinoscope aperture, in the continuum between the operator and infinity (slightly myopic and emmetropic eyes) or behind the eye (hyperopic eyes). In the case of "with" motion, lenses of progressively more plus refractive power must be inserted at the spectacle plane for neutrality to be achieved "Against" motion of the streak indicated that the far point was between the retinoscope aperture and the patient's eye (moderately to highly myopic eyes). In the case of "against" motion, lenses of progressively more minus refractive power must be inserted at the spectacle plane for neutrality to be achieved
  20. -When add plus spherical power, the streak tends to narrow & speed in its apparent motion.In high degrees of refractive error, it is narrow. -In low degree, it is wide. -At the neutralization point, the entire pupil is filled with light. Speed & prilliance- - In low degree of refractive error the shadow (red reflex) seen in the pupillary area is faint & moves rapidly with the movement of the mirror. - In high degrees of refractive error, it is very dark & moves slowly B=DxY/X where B= blur-circle diameter on the retina; D = diameter of the entrance pupil; X = distance from pupil to focus within schematic eye; and Y = distance from focus to blur circle at retina
  21. Break in the alignment between the reflex in the pupil and the band outside it is observed when the streak is not parallel to one of the meridian. The band of light in pupillary area lies in a position intermediate between the band outside the pupil and that from axis of the cylinder. The axis even in the case of low astigmatic error can thus be determined by rotating the streak until the break disappear. The correcting cylinder should placed at this axis. The oblique axis can be determined by rotating the streak until the break disappears.
  22. skew ( oblique motion of the steak reflex ) may be used to refine the axis in small cylinders. The steak and reflex will move in the same direction only when steak is aligned with one of the principal meridian. Therefore if the streak is not aligned with the true axis skewing will be observed on movement of the steak.
  23. The streak is turned 450 off axis in both directions If the axis is correct the width of the reflex should be equal in of the two positions. If the axis is not correct the widths will be unequal in the two position. In such a situation the narrower reflex serves as the guide towards which the cylinder axis should be turned
  24. Example : - if the 1800 is neutralized with + 2.00 sph. & the 900 with + 3.00D sph, the gross retinoscopy will be + 2.00Ds / + 1.00 Dc X 900 The Least positive power becomes the sphere power (+2.00DS) The amount of astigmatism is recorded as cylinder, and is the difference between the power of the two primary meridians The axis is the position of the beam in the most negative/least positive meridian
  25. Then with this spherical lens in place,
  26. the accommodative system in a young adult lags 0.50 to 0.75 behind a near target at 40 cm
  27. such that the target and retinoscopic aperture are located at the same distance from the eye MEM is unique in that lenses are primarily used to verify the observation of the doctor The amount of the “lag of accommodation” is the amount of plus lens corresponding to the movement seen the amount of lens is estimated based on the amount of movement observed
  28. Named so because small shiny bell dangling from a string that was used as a fixation target Measures the lag of accommodation as a linear measurement rather than with lenses. Typically we expect to see a change from “with” to “against” on the way in at 35 - 42 cm. (14 - 17inches) and a change from “against” to with at 37.5 - 45 cm. (15 -18 inches)
  29. In this case, The darkness of the room will facilitate the child to keep their attention on the retinoscope’s light The accommodation activity during the examination is small and the same in both eyes. It is important during the examination to keep the light of the retinoscope on the child’s pupil for only a short period of time so as not to stimulate accommodation; child-friendly and requiring less co-operation from the child The retinoscope is held at a distance of 50cm with hand-held trial lenses used to find the neutral point the result achieved by the Mohindra procedure in children between six months and four years of age is similar to wet retinoscopy (using cyclopentolate 1%), with a difference of only 0.50DS
  30. Retinoscopy may be done undercycloplegic or mydriatic drugs or without any drug Cycloplegics are the drugs which cause paralysis of accommodation & dilate the pupil These are used for retinoscopy