Retinoscopyadelabdelshafik.website/002-postgraduates-material...١ Retinoscopy Dr Mohamed Adel...
Transcript of Retinoscopyadelabdelshafik.website/002-postgraduates-material...١ Retinoscopy Dr Mohamed Adel...
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RetinoscopyDr Mohamed Adel Abdelshafik
Professor of ophthalmology – Ain Shams University Cairo Egypt
RetinoscopyRetinoscopy
Source of light
patientDoctormirror
Direction of mvt of mirror
Against No mvt With mvt
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- 2
- 2
0
0
+5
+5
- 4 - 2+ 3
We add – 2 on results :
• One for the distance of one meter • One for the tone of ciliary muscle if
atropine was used
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1
2
3
4
5
1
2
against
no mvt
3
4
5
with
with
with
no mvt
against
with
with
with
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no mvt
againstNo movement
with
with
with
No movement
No movement
No movement
no mvt
no mvt
no mvt
no mvt
no mvt
Far point
We add -1 D for the distance of one meter
Focal length
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Far point
+60 D
We add another -1 D for tone of CM if atropine was used during retinoscopy
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Source of light
As rays comes out from the eye parallelparallel---- with movement of RR
As rays comes out from the eye DivergentDivergent---- with movement of RR
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As rays comes out from the eye ConvergentConvergent---- with movement of RR
Observer
As rays comes out from the eye ConvergentConvergent---- with movement of RR
Observer
All the time pupil of pt looks fully illuminated : no mvt
As rays comes out from the eye ConvergentConvergent---- with movement of RR
Observer
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• In high errors the RR appears dim and moves slowly
• And in low errors the RR appears bright and moves rapidly
RR : dimmoves slowly
1
2
Image 2
Image 1
1
RR : brightmoves rapidly
1
2
Image 1
Image 2
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Verification of refraction
Verification of refraction
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Plan mirror
Concave mirror
Changing to a concave or convex mirror
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11 22 33 44
fi l
U + F = V
F
final vergenceInitial vergence
Lens power
F
F
F
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Rapidity of movement of RR :Rapidity of movement of RR :
• Rapidity of mvt of mirror
• Distance between mirror and source of light
• Distance between doctor an patient
• Error of refraction
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animation
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Approaching neutrality
Far point
Far point
Far point
Narrow
Wide
Filled
Finding the cylindrical axis
1. Break 2.Width & brightness
Off axisOff axis On axis
thickdim
thinbright
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Finding the cylindrical axis
3. Skew
Finding the cyln. Axis (straddling)
Cyl. is at 80oCyl. is at 80o
Correct axis
If proper axis …….the RR in the2 positions Should be equal. Here …. Move in the direction of the bright, narrow reflex
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Dynamic Retinoscopy
• The aim is to measure the effectiveness of the accommodation rather than the refractive error itself.
• we need to estimate the power of relative accommodation for a given distance.
Subjective method Objective method
Subjective method to determine Relative accommodation :Relative accommodation :
–– is the amount of accomm that can be exerted while conv. remained fixed (while fixing one point)
Clear image seen with both eyes33 cm
Should be as large as possible = large amount of acc. in reserve.
Should be at least as the –ve part.
So at 3 m.a. the relative acc is 5 D
Add –ve lenses till blurring (e.g. -3) …. +ve relative acc
Add +ve lenses till blurring (e.g. +2)….. –ve relative acc
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objective method to determine
Relative accommodation :Relative accommodation :
Dynamic retinoscopy
The examiner attracted the kid’s attention to the accommodative target and evaluated the retinoscopic reflex in both eyes.
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Focus binocularly
At working distance
Using distance
correction
to fixate an accommodative target at his working distance.
Expected movement of RR is No mvtbut with movement is obtained !
The lag can be explained as an inexactness of focusing.
This is known as the dynamic or objective lag , in normal individuals, usually falls between +0.25D and +1.00D..
If object moved slightly closer to pt No mvtIf + 0.5 or +0.75 are added binocularly No mvt
33 cm
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It can also be measured by moving backward ..
This distance is then measured and the two distances converted into dioptric values to work out the amount of lag present.
When this “With” mvt has been neutralized (the low neutral point)
Accomm.
Shadow is reversed ( high neutral point)
convex lenses are then added binocularly
When “With” mvt has been neutralized (the low neutral pointthe low neutral point)
Accomm.
Shadow is reversed ( high neutral pointhigh neutral point)
“neutral zone “ i.e. -ve relative accomm.i.e. Accomm that can be relaxed relative to convergence
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“neutral zone “
Accomm.
This highest (stongest) convex lens will relax his accomm to max. for that point. It is found it is too strong for the comfort of the patient. It is usually comfort to patient to exert a part of
accommodation.
Correction of presbyopia
• Glasses of distance• Then give convex lens suitable for
pt’s point of near work pt s point of near work. • We must keep 1/3 of his power of
accommodation in reserve (comfortable zone of accommodation)
• 2/3 of accommodation can be used and 1/3 should be kept in reverse to avoid fatigue.g
Comfort zone.