● Karton-N is a slightly glutinous, vermilion agent labeled as 'Karton-N.'
● Karton agents are safe on your hands or tissues during experiments.
The ingredients are gel chemicals whose composition is mainly polyvalent
alcohol that reacts with water to harden. They are, however, inflammable, so restrain from smoking during experiments and keep away from the fire devices.
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● Objectives:
Karton-N is used for the practice of PEA operations on cataract models of various consistencies.
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● Overall Steps of Procedures:
Perform a CCC on the anterior capsule of
a butchered pig's eye. ⇒ Remove the soft contents in the bag with a PEA
machine. ⇒ Slowly inject "Karton-N" as a substitute for the
viscoelastic material in the same manner as in implantation of IOL ⇒ Wait
for over 10 minutes till an artificial nucleus gels. ⇒ Then it is ready
for your practice as a model for a human cataract nucleus.
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● How to use "Karton-N"：
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| 1. |
At first, suck up approximately 0.5 ml of Karton-N into a 1.0 ml syringe
with a 25G or 27G needle. (While drawing the agent, try not to create
bubbles in the syringe. The bubbles make it difficult to judge the
accurate amount of the agent for each use and also to inject the agent
evenly.)
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| 2. |
Next, anchor an untreated pig eye to a base made of styrene foam or the like with marking pins. Then, with a stab knife, open 2 side ports around the circumference of the pig eye; one at 2 to 3 o'clock position and another at 10 to 11 o'clock position. Then, apply viscoelastic material into the anterior chamber to secure the chamber.
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| 3. |
a) For those who wish to perform a CCC with a cystotome needle, insert a 25G bent needle with a grip into the anterior chamber through
either one of the side ports and conduct a CCC with a rather small diameter.
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b) For those who wish to perform a CCC with cystotome forceps e.g. "Inamura's Forceps," make an opening at 12 o'clock position of the corneal limbus and again
apply viscoelastic material into the anterior chamber to secure the chamber.
Then, insert a cystotome forceps and conduct a CCC with a smallish diameter.
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| Note: |
Producing a CCC with a smallish diameter will be quite important for the later practices. In order for you
to acquire the skill for attaining the accurate diameter, it is essential
that you have mastered the previous "CCC training with Karton-C."
In addition, if possible, it is more desirable that you can both handle
needles and forceps for it will be useful in human cataract operations. |
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| 4. |
Next, remove the soft contents in the bag of the untreated pig eye with a PEA machine. The butchered pig eyes prepared for experiments are ordinarily the ones
taken out of 6 months old pigs, therefore, the nucleus formation can hardly
be found in them as in human eyes. |
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The suction process can be done without using ultrasonic waves, but it
will easier with a little effect of them. Unlike those of humans,
the anterior and posterior capsules of pig eyes are more elastic, so the
rupture of the capsule rarely occurs even when the tip of the ultrasonic
wave device is in contact with the capsule. With a human eye, however,
that immediately results in a capsule-rupture, so it is advisable to handle
with much care in this process.
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| 5. |
When the intralenticular space is clean and empty, apply the viscoelastic material again into the anterior chamber, but this time, inject it in a doughnut shape while avoiding a collapse of the anterior chamber. Furthermore,
considering the following procedure 6, try not to inject it into the bag.
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| 6. |
When the anterior chamber is secured, apply Karton-N through the side port from the pupil to the bag.
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First of all, slowly inject Karton-N from the edge of the anterior capsule
to the equator of the posterior capsule. Since the capsule bag is maintained
only with BSS (balanced sodium solution), in many cases it lacks of swelling,
and the position of the anterior chamber is shallow. In such cases,
slightly raise the flaps with the tip of the needle and try to avoid collapsing the posterior capsule. Ordinarily, the capsule bag is hardly bulged, and the posterior
capsule is closing in on the anterior capsule, so the injection needs to
be begun from the boundary. Thus, it is imperative that you locate
the exact position of the posterior capsule to avoid its rupture, which
is, in fact, a good practice for you to be ready for actual human cataract
operations.
As the injection of Karton-N proceeds, the capsule bag gradually swells,
and the agent slowly penetrates into the equator area. At the same
time, the posterior capsule descends towards the posterior pole, which
should make the injection easier.
If the injection is done ideally, Karton-N should spread in a doughnut shape and swell up to the center area of the pupil.
When a certain amount of the agent is injected, it will begin to overflow
into the anterior chamber. At that point, quit the injection and
withdraw the blunt needle. (The maximum amount to be injected is
approximately 0.5 ml.)
This part, the procedures 6, may seem easy, but the beginners may find it difficult. Nevertheless, after a few times of practice, you will be able to inject
an appropriate amount of Karton-N into the bag. As an old saying
goes, "Slow and steady wins the race." Take your time for its mastery.
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| 7. |
If everything goes well, the viscoelastic material will secure the anterior
chamber while the agent firmly gels without having the capsule to be collapsed.
However, in case a sign of collapse appears, immediately add some more viscoelastic material into the anterior chamber to maintain the chamber and to avoid the corneal endothelium and the agent
to be in contact with each other.
| Note: |
For keeping and saving the expensive blunt needles, remove all that is
left inside the needles by aeration.
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| Note: |
The setting time and handling with care are significant factors here in obtaining a hard Karton-nucleus. When it is left to harden
for more than 10 minutes, it will solidify quite firmly. After 30
minutes, its consistency will be rock-hard. |
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| 8. |
Now, we should have succeeded in producing a "cataract model" for your practice for human cataract operations. In addition, in
order for you to save time, you may want to produce successive models of
the same type to repeatedly practice on.
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Once you have thoroughly grasped the above-mentioned procedures including
the condition of the mixed agents, the appropriate setting time, and the
characteristics of Karton-N, you will be able to produce cataract models
of different consistencies, from soft to rock-hard.
The artificial cataract model that you have just produced enables
you to perform PEA training in several ways; the Karton-nucleus can be
drilled and divided in two parts with a spatula, or if the nucleus can
be rotated, you can turn it around with a spatula and a PEA chip and divide
it into four parts. It might be fun to try using a phacochop on it.
It is also an important practice to thoroughly suck up the fragments
that may appear when rotating the nucleus. While observing the position
of the posterior capsule in three dimensions, perform a series of such
training repeatedly.
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| 9. |
Unlike before when the human cataracts used to have 4 or 5 degrees hard-nuclei,
today's cataracts that we treat clinically are relatively softer, and we
call this particular phenomenon, "Cataracts have grown younger." Thus, it is perhaps more practical to rather train yourselves on
soft nuclei to practice a thorough suction of the fragments while confirming
the locations of the iris, the scleral flaps, and the posterior capsule.
It may not be worthwhile spending much time in attempting to produce
a rock-hard nucleus which often causes to clog the tube.
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| 10. |
Luckily, the pig's posterior capsule is tougher than that of a human's,
and a rupture of the capsule rarely occurs. After PEA, if the posterior
capsule and other lens tissues are still healthy, the above mentioned procedures
can be conducted repeatedly. Yet, on the safe side, we advise you a one-time use for each practice.
Thank you for your attention.
Jump to "Advanced Technique of Karton-N."
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