The document discusses the use of Jackson's cross cylinder, a toric lens utilized in refraction to assess and correct astigmatism. It explains the principles of its operation, including the test procedures for discovering, refining the axis, and adjusting the cylinder power to achieve optimal vision correction. The primary goals include determining the presence of astigmatism and ensuring that the circle of least confusion aligns with the retina.

1. JACKSON CROSS CYLINDER
SLIDES PREPARED BY
OPTOM FASLU MUHAMMED

2.  Cross cylinder is a type of toric lens used
during refraction also known as ‘flip
cylinder’. Its use was popularized by
Edward Jackson and it is often referred
to as Jackson’s cross cylinder.
 The cross cylinder is a Combination of
two cylinder of equal strength but with
opposite sign placed with their axis at
right angle to each other and mounted in
a handle.
 Principle of JCC is collapsing of the
sturms conoid.

4.  The cross cylinder is a sphero
cylindrical lens in which the power of
the cylinder is twice the power of the
sphere and of the opposite sign
 The lens is mounted on a handle
which is placed at 45 to the axes of
the cylinders
 The commonly used cross cylinders
are of +/- 0.25D and +/-0.50D.

5. JCC TEST
 Gives BVA done by fogging.
 The goal if astigmatism is present is to
place the circle of least confusion of
the sturms conoid on the retina thus
creating mixed astigmatism.

6. 1. Discovering the astigmatism
 If no cylinder correction is present
initially, the cross cylinder placed
arbitrarily at 90 and180 degree to check
for astigmatism.
 If a preferred flip position is found , a
cylinder is added with axis parallel to the
respective plus or minus axis of the
cross cylinder until the two flip choices
are equal.
 If no preference is found with cross
cylinder axes at 90 and 180, the 45 and
135 should always be checked assuming

7. 2. Refinement of the axis
 Always done first.
 Because the correct axis can be found in
the presence of an incorrect power but
the full cylinder power will not be found in
the presence of an incorrect axis.
 To check the axis, the cross cylinder is
held before the eye with its handle is
parallel with the axis of the trial cylinder
(i.e. with its axis at 45 degree to the axis
of cylinder in trail frame.)

8.  Pt is asked to tell about any change in the
VA, pt notices no difference b/w the two
positions - axis of the correcting cylinder in
the trial frame is correct.
 If VA is improved, cylinder correction is
present
 The cross cylinders is held in the preferred
position and the axis of the trial cylinder
rotated slightly towards the axis of the same
sign on the crossed cylinder
 The process is repeated until the trial cylinder
is in the correct axis for the eye clearer.

9. 3. Refinement of cylinder
power
 Cross cylinder is placed with its axis
parallel to the axis of the cylinder in the
trial frame. First with same sign and then
opposite sign.
 VA is not change in either of the position
the power of the cylinder in the trial
frame is correct.
 If VA is improving in any position
corresponding correction should be
made and reverified till final correction is
attained.

10. NOTES PREPARED BY