Explaining the basics of JCC

1. Jackson
Crossed-Cylinder
Indra P. Sharma
Optometrist

2. “....far more useful and far
more used” than any other
lenses in clinical refraction.
-Dr. Edward Jackson
JCC(Sharma IP)

3. Objective
To understand the optics and proper use of
Jackson Crossed-Cylinder in clinical practise.
JCC(Sharma IP)

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
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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. 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.
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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.
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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
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9. Axis for + cyl
(+0.25@90)
Power: +0.25DC
+ =
+0.25DS/-0.50DCx180
Axis for – cyl
(-0.25@180)
Power: -0.25DC
Contd...
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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.
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11. Marking of Principle meridian
The principal
meridians are marked
in the periphery of
JCC lens
In the UK, it is the
opposite.
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White dots = axis of the plus
cylinder
Red dots = axis of the minus
cylinder

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. 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. JCC(Sharma IP)
In almost all modern phoropters, the rotation of the JCC lens is automated

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)
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16. BE
Today’s
topic
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17. Procedure
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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
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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. 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”
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21. 1.Discovery of Astigmatism
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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.
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23. 2. Refinement of Axis
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24. Procedure
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25. Contd......
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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.
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27. Position 1
Resultant axis
-1.00
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“ Clear now”

28. Resultant axis
Position 1
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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
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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
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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. 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
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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.
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Source:William J Benjamin,2006, Borish’s Clinical Refraction, Butterworth Heineman Elsevier. 20: 818

34. 2. Refinement of Power
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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. Option 1 Circle of Least Confusion
Increases in size
Does not change position!
Interval of Sturm
Longer
“That looks awful”
JCC(Sharma IP)

37. Option 2 Circle of Least Confusion
Decreases in size
Does not change position!
Interval of Sturm
Shorter
“That is much better”
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38. Procedure
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3. JCC is placed with its axis parallel to the axis of the cylinder in the trial frame.

39. Contd...
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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. 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. Refining power
JCC(Sharma IP)
Add – 0.50
Deduct – 0.50

43. Sources of Error
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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. 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. 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. 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.
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48. Orthoptics as a career (ZG)
Blog: optomindra@blogspot.com