Phacoemulsification
procedure basically involves removing nucleus by dividing
it in small fragments. For grade III & IV nuclei,
chopping technique is considered as best amongst existing
techniques. Author wants to highlight a new approach
to divide such nuclei & has named this new technique
as WOODCUTTER'S TECHNIQUE.
When a woodcutter wants to divide a wooden log into
two pieces, he first nails a chisel in the log. Some
distance away from the chisel, he hammers on the log
with an axe goes on hammering, slowly approaching
chisel. As soon as he is very close to the chisel,
the wooden log automatically gets divided into two
vertical fragments .
(as shown in fig.1). Woodcutter's technique is based
on same principle.
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In
karate chop technique, we normally hold the nucleus
with phacotip & then move chopper towards the phaco
tip. As against this, in Woodcutter's, chopper is placed
at same place & not moved. Instead, the phaco tip,
which is holding the nucleus, is moved towards the chopper
(with phaco on). This automatically divides the nucleus
in two fragments, when phaco tip approaches near the
chopper. Thus chopper acts like a chisel & phaco
tip like an axe (as shown in fig.2). Remember that,
phaco sleeve should be 1.5 mm behind the outermost point
of phaco tip & you have to move phaco tip towards
chopper with phaco on. |
If you keep distance very small,
depth of phaco tip entering inside nucleus is less
& division becomes slightly difficult. For a harder
nucleus this distance should be more If the distance
is more, the irrigation may stop even if you withdraw
phaco probe slightly. No sculpting or grooving in
nucleus is required. It is easier to master woodcutter's
technique with clear corneal incision.
The
advantages of Woodcutter's technique are that ' it is
fast to perform, you are away from posterior capsule
as well as zonules, simple & easy even for phaco
beginners and a boon especially for nuclei which are
not so soft.
How to Learn ?
For Beginner -
After you have mastered sculpting & making partial
thickness groove you can directly start learning woodcutters
technique. This can be better learnt by replacing nucleus
in goat's eye by nucleus from stored eye bank eyes,
which are not useful for keratoplasty. By this you get
exact feeling of having operated on patient's eye. Make
main Phaco and side port incision on goats eye. Then
do capsulorhexis. Make a larger self sealing incision
of about 6mm on goats eye from opposite side. Then push
the nucleus taken out from the eye bank eye through
the large incision. Embed this nucleus in soft cortex
of goats eye by passing through capsulorhexis. Then
suture the large incision. Now learn woodcutter technique
on this nucleus. For that matter you can learn any technique
of dividing nucleus in this way.
For Phaco master-
Follow the steps (see above) in grade three or four
cataract. Do not get disheartened even if you are unable
to do it in first case. The technique shall not do any
harm to the patient's eye even if it fails. Gradually
you shall be master enjoying the fruits of learning
this technique.
This
technique is the best way to deal with harder nuclei
like grade II, III, and IV.
Steps of woodcutter’s technique
Phaco
sleeve should be 1.5 to 2 mm behind the outermost point
of Phaco needle. The exposed tip (portion of the Phaco
needle, which is not covered by sleeve) should be slightly
more as compared to that required for routine chop technique.
If you keep distance very small, depth/part of Phaco
tip entering inside the nucleus is less & division
becomes slightly difficult. For a harder nucleus tip
exposed should be more. If the distance is more than
required, the disadvantage is that irrigation may stop
even if you withdraw Phaco hand piece slightly. (This
is because the irrigation ports come near the incision
and get covered by incision)For this technique there
is no need of sculpting. Similarly no need to make a
groove in nucleus. This technique can be directly applied
to divide nucleus
Steps
–
- Part
of the Phaco needle, which is not covered by sleeve,
should be slightly more as discussed earlier.
- Both
the instruments i.e. Phaco needle and chopper are
introduced inside in the anterior chamber.
-
Push the nucleus slightly (by one millimeter) to
opposite clock position (opposite to the incision
site) with the help of a chopper.
-
Embed the Phaco tip into the nucleus. You should
enter keeping hand piece 70 to 80 degrees vertical.
The advantage of this is that the tip gets fully
embedded inside before you reach the center of nucleus
or center of capsulorhexis.
- When
the preset vacuum is reached, pull the nucleus towards
incision site by one mm. Embed the chopper at capsulorhexis
margin into the nucleus. This is possible only when
you are holding the nucleus firmly with Phaco tip.
- Push
the Phaco tip with Phaco on towards the chopper.
This will break the nucleus into two vertical fragments
in nearly all the cases. If not, then introduce
the chopper into the depth of the crack that you
have made and try to separate two fragments from
each other. It is necessary to go to the base of
the crack with chopper because it is easier to displace
fragments without stretch on zonules. If still you
cannot divide the nucleus, which may happen in the
beginning then rotate the nucleus by 180 degrees.
If rotation is not possible, repeat hydro dissection.
Try to rotate again. Once rotation is complete through
180 degree, again perform the same procedure as
mentioned earlier.
- For
second crack or cleavage rotate the nucleus. The
previous groove (which is created by movement of
Phaco tip towards the chopper) gives you space.
(You get more space as hard central part is taken
out). This space can be utilized for inserting Phaco
needle in the center and again dividing the nucleus
in above-mentioned manner.
- The
procedure is repeated till small fragments of nucleus
are made. In most of the cases you will be able
to achieve fragmentation of nucleus into two pieces;
except in very soft nuclei.
Advantages of woodcutter’s technique
-
While
making division of nucleus you are always away from
posterior capsule. Hence there is no danger of rupturing
it.
-
The
chopper stabilizes the nucleus. Because of this,
stretch on zonules is less. This is why I am using
Phaco power to divide nucleus rather than chopper.
Chopper only stabilizes nucleus, & gives direction
for crack to develop. As told earlier, chopper can
be compared to the chisel stapled in the log of
wood & Phaco to the axe.
-
As
you are in the nucleus & then using Phaco power,
even if power is more, it will not get dissipated
towards, corneal endothelium, which minimizes endothelial
damage
-
You
get more space in the center as hard part is taken
out when we move the Phaco tip towards the chopper
with Phaco on.
-
You
can increase vacuum to a great extent. Even if there
is a slight surge, it won’t cause much harm
as posterior capsule is far away & there is
nucleus in between Phaco tip & posterior capsule.
-
Less
power is required as Phaco is done after stabilizing
nucleus with chopper as if you are feeding the nucleus
in the Phaco tip.
-
Division
is in one stroke most of times especially in hard
nucleus.
-
Less Phaco time is required as division is in one
stroke. The procedure is fast to perform. Secondly
hard part of nucleus is taken out easily as if you
feed it to the needle while moving Phaco needle
towards chopper.
-
Cleavage
extends beyond and deep in the substance of nucleus
because of strain created by chopper. We may feel
that Phaco needle will touch the chopper. But this
will not happen because nucleus gets fragmented
into two even before you reach up to the chopper.
That’s why you will never go up to equator
i.e. peripheral soft part of nucleus. The needle
can become hot as Phaco is on with tip occluded.
-
In
small pupil or small capsulorhexis it is possible
to divide the nucleus as you do not have to go to
the periphery and still you get the division of
nucleus
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