Osher: Studying the optimal intraocular pressure
for a stable anterior chamber during phacoemulsification
is another Blumenthal top prize-winning
video produced by Japanese surgeons,
Doctors Suzuki, Igarashi, and Takahashi.
Narrator: A surge that occurs
after the occlusion break
of a US tip may cause a sharp elevation
of the posterior capsule and cause it to break.
However, movements
of the posterior capsule vary depending on the patient.
Then when does the posterior capsule elevate under what sort
of a condition of the eye?
We analyzed and studied this condition. Until now,
to investigate the changes in the anterior chamber
during PEA, we proposed a slit-side view, which is a method
of experimentally evaluating the changes
by using a slit lamp
and have published a variety of new knowledge and findings.
In particular, regarding the relationship
between the anterior chamber depth
and changes in anterior chamber pressure,
we proved that the combination
of pressurized perfusion in a peristaltic pump
and a handpiece attached
with a perfusion pressure sensor had the smallest anterior
chamber depth and anterior chamber pressure.
Even with this combination,
however, there are cases
where the posterior capsule elevates. Why?
We considered 2 major causes.
One is pressure from outside the eyeball, which is caused
by the patient's nervousness and other factors,
and the presence of the vitreous body.
First is external pressure.
During surgery, we often experience the anterior chamber
depth becoming shallow due to the patient's nervousness
as well as compression by the eyelid
speculum. Then, about
how much is the actual ocular pressure value during surgery?
As part of a preoperative examination,
we investigated the changes in IOP between before and
after use of a screw-type eyelid speculum.
We used the contact device and measured IOP before and
after opening the eyelid.
As a result, IOP rose significantly just
by using an eyelid speculum,
expanding the eyelid forcibly, and setting it.
In some cases, the IOP even exceeded 30 mm Hg.
In the past, we have been reporting that the IOP
during cataract surgery should ideally be brought to
as normal conditions as possible in order to reduce the risk
of tissue invasion.
However, if the IOP during surgery had elevated due
to some external causes,
we must make the pressure against the anterior
chamber higher than it.
The reason is that if the anterior chamber pressure is
smaller than the pressure from the back, it is highly likely
that the posterior capsule would elevate.
We produced this condition with SSV
and studied it. Instead of an eyelid,
we placed a rubber band around the porcine eye
to make it look like an eyelid
and produced a model wearing an eyelid speculum.
We observed the model under a variety
of conditions using an SSV and recorded the findings.
We then measured the movements on the image from the cornea
to the posterior capsule
and quantitatively analyzed the rate of changes.
For this experiment, we used Centuria
and for the US handpiece we used active sentry,
an ultrasound handpiece attached
with a perfusion pressure sensor.
First, under normal conditions,
the posterior capsule clearly showed greater movements when
the eyelid speculum was used.
Next, we ran the perfusion pressure sensor
and saw that the posterior capsule moved less than when the
sensor was not run.
We therefore learned
that the sensor suppressed the movements
of the posterior capsule.
Even in this case,
however, a quantitative analysis showed
that the posterior capsule had moved significantly greater
when the eyelid speculum was used.
This indicated, as expected,
that external force was deeply involved with the movements
of the posterior capsule.
Next, let us consider the impact of the vitreous body.
The posterior capsule adheres to the anterior vitreous body
by the Wieger's ligament and is supported and made stable.
Therefore, the posterior capsule rarely elevates in eyes
that have not caused anterior vitreous
detachment, such as this.
But if the anterior vitreous detachment occurs,
as the vitreous body shrinks with age,
the posterior capsule is believed to become unstable,
so the condition of the vitreous body is believed
to be deeply involved with the movements
of the posterior capsule.
To conduct analysis using SSV, we created a model
of a porcine eye that had undergone vitrectomy
and eliminated the influence
of the vitreous body found immediately
behind the posterior capsule.
The interior vitreous body was dissected from the vitreous
body that had adhered
to the posterior capsule to the periphery.
First, this is the porcine eye
that had not undergone vitrectomy.
By using a perfusion pressure sensor, we learned
that the posterior capsule moved very little at the time
of an occlusion break.
Even with a porcine eye that had the vitreous body removed,
the perfusion pressure sensor showed fewer posterior capsule
movements. Image-wise, the eye
that had undergone vitrectomy appeared
to move slightly less.
Next, we evaluated the impact
of the eyelid speculum worn on a porcine eye
that had undergone vitrectomy.
We found that the eye
that used the device clearly moved more.
We therefore made a quantitative comparison
with an eyelid speculum put on between with
and without vitrectomy.
The results showed that the movements
of the posterior capsule of an eye
that had not a undergone vitrectomy were
significantly greater.
This finding suggests that the presence
of a vitreous body found immediately
behind the posterior capsule was deeply involved
with the movements of the posterior capsule.
How then should we deal with cases
where the posterior capsule actually becomes elevated?
When we investigated using SSV, we found that the movement
of the posterior capsule gradually decreased
by raising the setting of the IOP from 20 to 30 and to 40.
We assumed that to cope with destabilization
of the posterior capsule due to a variety of factors,
we should adjust the setting of the IOP according
to the patient and to the stage of surgery.
For example, in a surgery
with a patient whose preoperative ocular pressure was a high
40 mm Hg,
the anterior chamber becomes unstable.
Therefore, by referencing the ocular pressure measured
before surgery and setting the IOP at a slightly high level,
it is possible to prevent the posterior
capsule from elevating.
What is important here is
that when the nucleus remains in the lens capsule, the risk
of the posterior capsule breaking is low.
So, a tailor-made technique of controlling the IOP
as needed is ideal.
To do this, we suggest that an ideal PEA machine is a device
that automatically controls perfusion pressure
by having an eyelid speculum equipped with a sensor
that measures the IOP
and by having the measurement values sent
to the PEA machine.
The PEA machine of the future is just around the corner.
Burkhard Dick: For sports fans, the Super Bowl is an institution.
For policy ones, the electoral map this November
and CNN's John King explaining even the most obscure voting
district is an institution.
And for every ophthalmic surgeon, the Video Journal
of Cataract, Refractive,
and Glaucoma Surgery is an institution. Were I asked
to tell someone what I've learned from the journal,
I would hardly know where to begin and where to end.
One thing is for sure though,
like ophthalmologists on 5 continents, I always,
and for many years now, wait eagerly for the next issue.
Many surgical techniques I have seen here for the first time,
and quite a number
of them have been incorporated in my practice.
Very impressive--
has always been the meticulous, one can say,
loving way in which Bobby Osher is presenting the videos.
This alone, besides his many other achievements,
secures him a place in the pantheon of ophthalmology.
To the Video Journal of Cataract, Refractive,
and Glaucoma Surgery team, heartfelt
congratulations on this remarkable anniversary
And my wish for the next 40 years,
keep up the good work.
You are always a winner and would get reelected every time.
Osher: Thanks, Burkhard.