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Jackson
Crossed-Cylinder
Indra P. Sharma
Optometrist
“....far more useful and far
more used” than any other
lenses in clinical refraction.
-Dr. Edward Jackson
JCC(Sharma IP)
Objective
To understand the optics and proper use of
Jackson Crossed-Cylinder in clinical practise.
JCC(Sharma IP)
Contents
1. Introduction to JCC
2. Historical Perspective
3. Optics – How is it made?
4. The choice of JCC
5. Detection of...
Introduction to JCC
Jackson Crossed-Cylinder is a
combination of two cylinders of
equal strength but of opposite signs
pla...
Historical Perspective
1849-The original concept of crossed cylinders was
described by Stokes.
1855-The Stokes lens was ...
Contd.....
The present technique
-designed and described by
Dr. Edward Jackson for the
determination of cylinder
power in ...
Optics- How is it made?
A typical JCC lens is a spherocylindrical lens having
a spherical power component combined with a...
Axis for + cyl
(+0.25@90)
Power: +0.25DC
+ =
+0.25DS/-0.50DCx180
Axis for – cyl
(-0.25@180)
Power: -0.25DC
Contd...
JCC(Sh...
Contd...
Crossed cylinders of +0.25 DS combined with -0.50 DC
(+-25 DC) or +0.37 DS combined with -0.75 DC (to.37
DC), et...
Marking of Principle meridian
The principal
meridians are marked
in the periphery of
JCC lens
In the UK, it is the
oppos...
Handle of JCC
A handle is attached between the two marked axes, which
enables the lens to be "twirled" before the eye by ...
Contd....
0.5 D Jackson cross-cylinder in
primary orientation. The handle
is down to the right and at 45º to
the horizonta...
JCC(Sharma IP)
In almost all modern phoropters, the rotation of the JCC lens is automated
Choice of JCC
Vision 6/9 or better: use 0.25DC x-cyl
If results unreliable, then change up to 0.50 x-cyl. and see if
mor...
BE
Today’s
topic
JCC(Sharma IP)
Procedure
JCC(Sharma IP)
Starting point for JCC
After retinoscopy.....adjust sphere.
End point of spherical adjustment is the starting point
of J...
Eg: Simple myopic astigmatism
Interval of Sturm
Circle of Least Confusion
Blur is due to combination of…
CLC in front of t...
With best spherical correction
Circle of Least Confusion
Has moved, is now on the retina
Interval of Sturm
Length unchange...
1.Discovery of Astigmatism
JCC(Sharma IP)
If astigmatism is present
But WHY
- because the correct axis can be found in the presence
of an incorrect power but the f...
2. Refinement of Axis
JCC(Sharma IP)
Procedure
JCC(Sharma IP)
Contd......
JCC(Sharma IP)
Example
You have performed retinoscopy on a patient
Retinoscopy value
-1.00DS/-1.00DCx180, 6/9
You have checked the sp...
Position 1
Resultant axis
-1.00
JCC(Sharma IP)
“ Clear now”
Resultant axis
Position 1
JCC(Sharma IP)
Refining axis
Patient response
“Lens position 1 was clearer”
So, we rotate the cylinder lens towards the position of
th...
Patient response
We rotated the axis of the trial lens AND the handle of the x-
cyl by 20 deg
“Both lenses are equally b...
“ They are same”
May be on axis, therefore move cyl axis by about 20deg and check to
see if it returns
May be within ran...
Range of uncertainty
In real life, most patients will report that both lenses are equally
blurred over a range of axes
T...
How much axis to move?
Del Priore and Guyton
gave the guidelines
suggested in Table 20-2
for the initial change in
correc...
2. Refinement of Power
JCC(Sharma IP)
Optical principle of power
refinement
When determining the power, JCC will either increase
or decrease residual cyl, eith...
Option 1 Circle of Least Confusion
Increases in size
Does not change position!
Interval of Sturm
Longer
“That looks awful”...
Option 2 Circle of Least Confusion
Decreases in size
Does not change position!
Interval of Sturm
Shorter
“That is much bet...
Procedure
JCC(Sharma IP)
3. JCC is placed with its axis parallel to the axis of the cylinder in the trial frame.
Contd...
JCC(Sharma IP)
Example
Using ± 0.50 JCC
Retioscopy : -1.00DS/-0.75 DC X 120
If the patient prefers the lens
When red marks are aligned...
Contd.....
JCC(Sharma IP)
 For each -0.50DC change, you need to add +0.25DS, to keep the circle of
least confusion on the...
Refining power
JCC(Sharma IP)
Add – 0.50
Deduct – 0.50
Sources of Error
JCC(Sharma IP)
Common errors
1.Not keeping the circle of least confusion on the retina
Starting with the wrong sphere power
Forgetting ...
Points to ponder- Summary
JCC is always a sphero-cylindrical lens such that one meridian is plus
power and the other meri...
Conclusion
The most accepted procedure used by the
overwhelming majority of examiners is the JCC
technique.
Freeman and ...
Reference
1. William J Benjamin,2006, Borish’s Clinical Refraction, Butterworth Heineman
Elsevier. 20: 816-829
2. Wunsch S...
Orthoptics as a career (ZG)
Blog: optomindra@blogspot.com
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Explaining the basics of JCC

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JCC -Jackson Cross Cylinder

  1. 1. Jackson Crossed-Cylinder Indra P. Sharma Optometrist
  2. 2. “....far more useful and far more used” than any other lenses in clinical refraction. -Dr. Edward Jackson JCC(Sharma IP)
  3. 3. Objective To understand the optics and proper use of Jackson Crossed-Cylinder in clinical practise. JCC(Sharma IP)
  4. 4. Contents 1. Introduction to JCC 2. Historical Perspective 3. Optics – How is it made? 4. The choice of JCC 5. Detection of astigmatism 6. Refinement of axis 7. Refinement of power 8. Sources of Error 9. Points to ponder-Summary 10. Conclusion 11. Reference JCC(Sharma IP)
  5. 5. Introduction to JCC Jackson Crossed-Cylinder is a combination of two cylinders of equal strength but of opposite signs placed with their axis at 90 degrees to each other and mounted in a handle. Jackson Crossed-Cylinder (JCC) technique is also called the flip- cross technique. JCC(Sharma IP)
  6. 6. Historical Perspective 1849-The original concept of crossed cylinders was described by Stokes. 1855-The Stokes lens was used in a variation of the present technique by Dennet Crisp brought it to worldwide attention, and it has become known as the JCC technique. JCC(Sharma IP)
  7. 7. Contd..... The present technique -designed and described by Dr. Edward Jackson for the determination of cylinder power in 1887 and for axis in 1907. JCC(Sharma IP)
  8. 8. Optics- How is it made? A typical JCC lens is a spherocylindrical lens having a spherical power component combined with a cylinder power component of twice the power of the sphere, and of opposite sign. Eg: +0.50 DS combined with -1.00 DC. This results in a net power of +0.50 DC in one axis and -0.50 DC in the other axis(+-50 DC). +0.50/-1.00 @90 JCC(Sharma IP)
  9. 9. Axis for + cyl (+0.25@90) Power: +0.25DC + = +0.25DS/-0.50DCx180 Axis for – cyl (-0.25@180) Power: -0.25DC Contd... JCC(Sharma IP)
  10. 10. Contd... Crossed cylinders of +0.25 DS combined with -0.50 DC (+-25 DC) or +0.37 DS combined with -0.75 DC (to.37 DC), etc.,are available. Thus, the two principal axes of a crossed-cylinder lens exhibit equal cylinder power of opposite signs. JCC(Sharma IP)
  11. 11. Marking of Principle meridian The principal meridians are marked in the periphery of JCC lens In the UK, it is the opposite. JCC(Sharma IP) White dots = axis of the plus cylinder Red dots = axis of the minus cylinder
  12. 12. Handle of JCC A handle is attached between the two marked axes, which enables the lens to be "twirled" before the eye by rotation of the handle. In this manner, the positions of the minus and plus axes are interchanged rapidly and alternately. The common term used for the rotating the handle is known as flipping. Hence, the JCC is often termed as flip-cross cylinder. JCC(Sharma IP)
  13. 13. Contd.... 0.5 D Jackson cross-cylinder in primary orientation. The handle is down to the right and at 45º to the horizontal. The label +.50 is in the usual orientation for reading; -.50 reads upward. The markings are in red (as here) and white (shown black here). JCC(Sharma IP)
  14. 14. JCC(Sharma IP) In almost all modern phoropters, the rotation of the JCC lens is automated
  15. 15. Choice of JCC Vision 6/9 or better: use 0.25DC x-cyl If results unreliable, then change up to 0.50 x-cyl. and see if more reliable Vision 6/12 or worse: use 0.50DC x-cyl If results reliable and vision improves, change down to 0.25 Use a larger target until the vision improves! Vision 6/24 or worse: try 0.75DC x-cyl If results unreliable, use alternative method of astigmatic correction (Astigmtic Fan, keratometry etc) JCC(Sharma IP)
  16. 16. BE Today’s topic JCC(Sharma IP)
  17. 17. Procedure JCC(Sharma IP)
  18. 18. Starting point for JCC After retinoscopy.....adjust sphere. End point of spherical adjustment is the starting point of JCC refinement. Circle of least confusion must be on retina (ILM), so check sphere first. Remember Strums Conoid JCC(Sharma IP)
  19. 19. Eg: Simple myopic astigmatism Interval of Sturm Circle of Least Confusion Blur is due to combination of… CLC in front of the retina Focal lines being separated “It’s very blurred”
  20. 20. With best spherical correction Circle of Least Confusion Has moved, is now on the retina Interval of Sturm Length unchanged Reason the vision is still blurred “That’s better but it still isn’t clear” JCC(Sharma IP)
  21. 21. 1.Discovery of Astigmatism JCC(Sharma IP)
  22. 22. If astigmatism is present But WHY - because the correct axis can be found in the presence of an incorrect power but the full cylindrical power will not be found in the presence of an incorrect axis. JCC(Sharma IP)
  23. 23. 2. Refinement of Axis JCC(Sharma IP)
  24. 24. Procedure JCC(Sharma IP)
  25. 25. Contd...... JCC(Sharma IP)
  26. 26. Example You have performed retinoscopy on a patient Retinoscopy value -1.00DS/-1.00DCx180, 6/9 You have checked the sphere power Now lets refine axis of the cyl. JCC(Sharma IP)
  27. 27. Position 1 Resultant axis -1.00 JCC(Sharma IP) “ Clear now”
  28. 28. Resultant axis Position 1 JCC(Sharma IP)
  29. 29. Refining axis Patient response “Lens position 1 was clearer” So, we rotate the cylinder lens towards the position of the red markings In this case, position 1 Initially, move by steps of about 15 deg, then use smaller steps as we get closer JCC(Sharma IP)
  30. 30. Patient response We rotated the axis of the trial lens AND the handle of the x- cyl by 20 deg “Both lenses are equally blurred” This means that the cyl axis of the trial frame now matches the patient’s cyl axis The true axis is 160 deg In real life, you would continue until the patient sends us in the other direction (reversal) There is usually a range where the images appear equal, and we need to find the limits Choose the axis mid-way between the two reversals JCC(Sharma IP)
  31. 31. “ They are same” May be on axis, therefore move cyl axis by about 20deg and check to see if it returns May be within range of uncertainty (next slide) 0.25DC JCC may give insufficient difference Try 0.50DC 0.50DC JCC may give too much distortion Move down to 0.25DC If none of the above help, use alternative technique. JCC(Sharma IP)
  32. 32. Range of uncertainty In real life, most patients will report that both lenses are equally blurred over a range of axes This is more common with low cyl power You need to identify the range Find where the patient tells you to rotate in the opposite direction at each end Select the axis in the middle of the range JCC(Sharma IP)
  33. 33. How much axis to move? Del Priore and Guyton gave the guidelines suggested in Table 20-2 for the initial change in correcting axis position relative to power of the correcting cylinder while checking the axis. JCC(Sharma IP) Source:William J Benjamin,2006, Borish’s Clinical Refraction, Butterworth Heineman Elsevier. 20: 818
  34. 34. 2. Refinement of Power JCC(Sharma IP)
  35. 35. Optical principle of power refinement When determining the power, JCC will either increase or decrease residual cyl, either expanding or collapsing the astigmatic interval and circle of least confusion Thereby making the target less or more clear JCC(Sharma IP)
  36. 36. Option 1 Circle of Least Confusion Increases in size Does not change position! Interval of Sturm Longer “That looks awful” JCC(Sharma IP)
  37. 37. Option 2 Circle of Least Confusion Decreases in size Does not change position! Interval of Sturm Shorter “That is much better” JCC(Sharma IP)
  38. 38. Procedure JCC(Sharma IP) 3. JCC is placed with its axis parallel to the axis of the cylinder in the trial frame.
  39. 39. Contd... JCC(Sharma IP)
  40. 40. Example Using ± 0.50 JCC Retioscopy : -1.00DS/-0.75 DC X 120 If the patient prefers the lens When red marks are aligned with trial cyl axis (120 deg), add -0.50 DC When white marks are aligned with trial cyl axis (120), reduce -0.50DC Equally clear: you have the right power JCC(Sharma IP)
  41. 41. Contd..... JCC(Sharma IP)  For each -0.50DC change, you need to add +0.25DS, to keep the circle of least confusion on the retina  Add -0.25DS for each +0.50DC change So in the example : -1.00DS/-0.75 DC X 120 If the patient prefers red marks Final power is: -0.75DS/ -1.25 DC X 120
  42. 42. Refining power JCC(Sharma IP) Add – 0.50 Deduct – 0.50
  43. 43. Sources of Error JCC(Sharma IP)
  44. 44. Common errors 1.Not keeping the circle of least confusion on the retina Starting with the wrong sphere power Forgetting to change sphere power if cyl is changed by 0.50DC or more 2.Assuming the axis is correct if the patient says “they look the same” without checking Could be no astigmatism at all Could be 90deg off 3.Incorrect presentation time – esp too quick 4.Poor alignment of JCC and trial frame axis JCC(Sharma IP)
  45. 45. Points to ponder- Summary JCC is always a sphero-cylindrical lens such that one meridian is plus power and the other meridian is of equal minus power.  The red dots identify the axis of the minus power and the white dot is of plus power. While refining axis: JCC handle is parallel to trail lens cylinder axis While refining power: JCC lens axis is parallel to trail lens cylinder axis. When patient says “ both sides are same” exclude all posibilities. JCC(Sharma IP)
  46. 46. Conclusion The most accepted procedure used by the overwhelming majority of examiners is the JCC technique. Freeman and Purdum and Goar considered the JCC to be the most delicate test for astigmatism. The use of JCC is very important in clinical parctise of refraction and an it serves as an important instrument for optometrist. JCC(Sharma IP)
  47. 47. Reference 1. William J Benjamin,2006, Borish’s Clinical Refraction, Butterworth Heineman Elsevier. 20: 816-829 2. Wunsch SE. 1971. The cross cylinder. Int Ophthalmol Clin 11:131-153. 3.Brookman KE. 1993. The Jackson cross-cylinder: Historical perspective. JAm Optom Assoc 64:329-331. 4. Crisp WHo 1943. Photographing cross cylinder tests. Am J Opht 26:758-760. 5. Duke Elder, 1998. Practise of Clinical Refraction, Butterworth Heineman Elsevier. 4: 181-183 6. Khurana AK 2013. Optics and refraction, 6: 133-134 7. Perlstein SII. 1982. Mounted cross-cylinder: A new mounted Jackson cross- cylinder. Ann Opht/Ullmol 14:992. 8..Del Priore LV, Guyton DL. 1986. The Jackson cross cylinder, a reappraisal. Ophthalmology 93: 1461-1465. 9. Sims CN, Durham DG. 1986. The Jackson cross-cylinder disproved. 'hans Am Ophthailltol Soc 84:355-386. JCC(Sharma IP)
  48. 48. Orthoptics as a career (ZG) Blog: optomindra@blogspot.com
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Explaining the basics of JCC

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