Effect of IOP based infusion system with and without balanced phaco tip on cumulative dissipated energy and estimated fluid usage in comparison to gravity fed infusion in torsional phacoemulsification
Malik et al. Eye and Vision
Effect of IOP based infusion system with and without balanced phaco tip on cumulative dissipated energy and estimated fluid usage in comparison to gravity fed infusion in torsional phacoemulsification
Praveen K. Malik 0
Taru Dewan 0
Arun Kr Patidar 0
Ekta Sain 0
0 Dr Ram Manohar Lohia Hospital , New Delhi , India
Background: To evaluate the effect of three different combinations of tip designs and infusion systems in torsional phacoemulsification (INFINITI and CENTURION) in patients with cataract. According to the manufacturer, two unique improvements in the Centurion are: active fluid dynamic management system and use of an intrepid balanced tip. The study specifically aimed to evaluate the beneficial effects, if any, of change in tip design and infusion system individually and in combination on both per-operative parameters as well as endothelial health over 6 months. Methods: One hundred and twenty six consenting patients of grade 4.0-6.9 senile cataract were randomized into three groups for phacoemulsification: Group A (n = 42): Gravity fed infusion system and 450 Kelman miniflared ABS phaco tip; Group B (n = 42): intraocular pressure (IOP) based infusion system and 450 Kelman miniflared ABS phaco tip; Group C (n = 42): IOP based infusion system and 450 Intrepid balanced phaco tip. The cumulative dissipated energy (CDE), estimated fluid usage (EFU) and total aspiration time (TAT) were compared peroperatively. The endothelial parameters were followed up postoperatively for six months. Results: The three arms were matched for age (p = 0.525), gender (p = 0.96) and grade of cataract (p = 0.177). Group C was associated with significant reductions in CDE (p = 0.001), EFU (p < 0.0005) as well as TAT (p = 0.001) in comparison to the other groups. All three groups had comparable baseline endothelial cell density (p = 0.876) and central corneal thickness (p = 0.561). On post-operative evaluation, although all groups were comparable till 3 months, by 6 months, the percentage losses in endothelial cell density were significantly lower in group C as compared to the other groups. Conclusions: Use of an IOP based phacoemulsification system in association with use of the Intrepid balanced tip reduces the CDE, EFU and TAT in comparison to a gravity fed system with a mini flared tip or IOP based system with a mini flared tip while also providing better endothelial preservation thus favouring the use of an IOP fed system with a balanced tip.
Active fluidics; CENTURION active; Centurion; IOP based infusion; Torsional; Phacoemulsification; Intrepid balanced tip; Kelman miniflared tip; Gravity based infusion; Cumulative dissipated energy
The ultimate aim of every phacoemulsification platform
is an energy efficient, time efficient yet safest possible
surgical system. While an efficient phacosystem should
aim at smooth, fast and well controlled
phacoemulsification, minimum complication rates must accompany to
complement the same. The intensity and duration of
ultrasonic insult have a bearing on endothelial losses,
hence the aim is to deliver the lowest energy in the eye
and reduce ultrasound time simultaneously [
Phacoemulsification platforms have evolved to reduce
intracameral ultrasound energy by introducing not only
novel energy delivery techniques like micropulse, burst,
torsional ultrasound, but also improvising on tip designs
to have better hold, cutting efficiency and smooth
]. However, some surgeons rank the fluidic
control as having paramount importance in achieving
breakthrough in phacoemulsification, attaching only
secondary importance to tip designs [
When Centurion was launched by Alcon, the company
claimed dramatic reduction of cumulative dissipated
energy (CDE) in comparison to the earlier Infiniti; the
claims have been verified by some independent studies
]. The balanced tip in the Centurion has been shown
to lead to lower CDE, however, a major difference also
lies in the infusion system of the two platforms [
superior anterior chamber stability of an intraocular
pressure (IOP) fed system is hoped not only to make
surgery smoother and faster, but also to protect the
endothelium. Hence, to attribute all the benefit either to
the balanced tip or the IOP fed infusion is not possible
unless they are separately compared with identical
settings for the rest of the parameters [
]. With this in
mind, we designed this three arm comparative study in
which first Infiniti and Centurion were compared using
the same mini flared tip to find the individual effect of
fluidic systems and then the miniflare tip and balanced
tip were compared in the Centurion to find the specific
advantage offered by this tip design.
Certain intraoperative parameters such as CDE,
estimated fluid usage (EFU) and total aspiration time (TAT)
can provide a comparison between any two
phacoemulsification systems in terms of efficiency, but a study of
the endothelium is mandatory to prove the real benefit
as we treat the eye as a whole and a reduction of any
factor at the cost to the endothelium is pointless.
Therefore, we designed this study to compare both CDE as
well as endothelial status post-operatively.
This prospective randomized control trial was conducted
in the Department of Ophthalmology, Post Graduate
Institute for Medical Education and Research, Dr. Ram
Manohar Lohia Hospital, New Delhi, India. The study
was approved by the Institutional Ethics Committee and
followed the tenets of Helsinki.
A pilot study found a mean CDE to be 30%-secs with
standard deviation (SD) of ±5.5%-secs using gravity fed
infusion and 45° Kelman miniflared ABS phaco tip for
phacoemulsification. With a minimum number of 40
patients in each group, the study was expected to have
95% power to detect a difference of 15% in each group
for phacoemulsification at 95% significance level using
the student’s t-test.
Previously diagnosed patients of cataract reporting to
the eye out patient department of Dr. RML hospital
were approached to participate in the study. After a
written informed consent, detailed history pertaining to the
patient’s background, medical & ophthalmic complaints
were taken. A comprehensive pre-operative eye
examination was performed in each patient. Grading of cataract
into grades 1.0–6.9 was done according to Lens Opacities
Classification System III (LOCS III) classification. The
cases with NO/NC 4.0 to 6.9 were included in the study.
Patients with pre-operative endothelial cell density
(ECD) count less than 1500 cells/mm2, all eye
pathologies that can compromise the visual recovery, eyes
with any kind of corneal dystrophy or corneal scars
preventing visualization of cataract for reliable
grading, subluxated or dislocated lens, raised intraocular
pressure (> 21 mmHg) and cases with history of
previous intraocular surgery were excluded from the
study. A preoperative specular microscopy using
Noncontact specular microscope (EM -3000; TOMEY:
VERSION 2A/OJ) was done for all cases.
One eye of each patient that fulfilled the inclusion
criteria was allocated to the study. Participants were
randomly distributed by an independent observer using
an envelope technique into three groups: group A
undergoing phacoemulsification using gravity fed
infusion system and miniflared phaco tip; group B
undergoing phacoemulsification using IOP based infusion
system and miniflared phaco tip; and group C
undergoing phacoemulsification using IOP based infusion system
and balanced phaco tip.
The operations were performed by one surgeon (PKM)
experienced in the technique within 1 month of
recruitment. Uniform pre-regime of dilatation of the pupil was
done with tropicamide (0.8%) + phenylephrine
hydrochloride (5%) eye drops every 15 mins for 45 mins
before surgery. Plain tropicamide was used in hypertensive
patients. All surgeries were performed under topical
anaesthesia or peribulbar block with 2% lidocaine +
adrenaline +0.5% bupivacaine with hyaluronidase.
Adrenaline was omitted in hypertensive patients. All
surgeries were performed through a 2.2 mm incision.
Ultrasleeves (2.2 mm) were used with Infiniti while new
generation sleeves were used with the Centurion system.
Following capsulorhexis, hydrodissection and rotation,
the nucleus was dissembled by direct phaco chop
technique. Phacoemulsification was done at 500 mmHg
vacuum and aspiration flow rate of 40 cm3/min and
1–100% torsional phacoemulsification with IP setting
at 10 ms and 1:1 ratio in all three groups. The cases were
done at a bottle height of 110 cm in group A and at an
IOP of 55 mmHg in groups B and C followed by irrigation
and aspiration and IOL insertion.
Per-operative outcome variables
At the time of surgery, CDE, EFU and TAT were noted in
each group. Any surgical complication was also noted.
Post-operative evaluation included specular microscopy
at 1 week, 1, 3 and 6 months and visual acuity at
1 month after the surgery by a third observer who was
neither the operating surgeon nor was aware of the
surgical technique performed on the patient to avoid bias.
Noncontact specular microscope (EM – 3000; TOMEY:
VERSION 2A/OJ) was used to calculate ECD, coefficient
of variance (CV) of cell size, percentage of hexagonal
endothelial cells and corneal thickness before surgery
and at each postoperative visit. Three endothelial cell
photographs were taken at each visit and the mean cell
count of three photographs was calculated. Endothelial
cell loss was calculated as a percentage of pre-operative
cell density. Visual acuity was tested using Snellen’s
chart; it was converted into the logMAR scale for
Categorical variables were presented in numbers and
percentages (%) and continuous variables were presented
as mean ± SD and median. Normality of data was tested
using the Kolmogorov-Smirnov test. If the normality
was rejected then a non-parametric test was used.
Statistical tests were applied as follows:
1. Quantitative variables were compared using
ANOVA/Kruskal-Wallis test (when the data sets
were not normally distributed) between the three
groups and ANCOVA for comparison after
adjusting for confounding factors.
2. Qualitative variables were compared using
Chi-Square test/Fisher’s exact test. A p value
of <0.05 was considered statistically significant.
The data was entered in MS EXCEL spreadsheet and
analysis was done using Statistical Package for Social
Sciences (SPSS) version 21.0.
One hundred and twenty six eyes of 126 patients were
randomized into three arms during the study.
Group A (n = 42): Gravity fed infusion system
(INFINITY Vision System) and 45° Kelman miniflared ABS
phaco tip (Alcon Laboratories, Inc., Fort Worth, TX,
Group B (n = 42): IOP based infusion system
(CENTURION Vision System) and 45° Kelman miniflared
ABS phaco tip (Alcon Laboratories, Inc., Fort Worth,
Group C (n = 42): IOP based infusion system
(CENTURION Vision System) and 45° Intrepid balanced
phaco tip. (Alcon Laboratories, Inc., Fort Worth, TX,
The demographics are demonstrated in Table 1. The
three arms were matched for Age (p = 0.60), Gender
(p = 0.96), Nuclear Colour (p = 0.17) and Nuclear
Opalescence (p = 0.121). The nuclear grade positively correlated
with age of the patient. Coaxial phacoemulsification was
done in all cases. There was no incidence of posterior
Peroperative records of CDE, EFU and TAT were
compared. The analysis revealed that a higher grade of
nuclear cataract significantly correlated with higher
CDE, EFU and TAT (Table 2).
Kruskal Wallis test was applied to compare the
peroperative parameters between the three groups and it was
found that difference in CDE in group B when compared
to group A was not statistically significant but a
significantly low CDE was seen in group C in comparison to
groups A and B (p = 0.001).
EFU was not significantly lower in group B when
compared to group A, however, it was significantly lower
in group C in comparison to group A as well as group B
(p < 0.0005).
TAT was not significantly lower in group B when
compared to group A, but was significantly lower in group C
when compared to groups A and B (p = 0.001) (Table 3).
Thus, our results demonstrated that it is not just a
change in infusion platform but a change in tip design
that is associated with significant reductions in CDE,
EFU as well as TAT. However, one of the main purposes
of achieving such parameters is the intended safety for
endothelium. Thus, we analysed the postoperative
endothelial parameters as shown in (Table 4).
All three groups had comparable baseline ECD
(p = 0.876) and central corneal thickness (CCT) (p = 0.561)
but the CV was significantly lower in group B in
comparison to groups A and C (p = 0.022) and hexagonal
endothelial cell count was comparable between groups A and B but
significantly lower in group C (p = 0.004).
Post-operative evaluation at 1 week, 1 month, 3 months
and 6 months found that at all visits, ECD was in the
order B > A > C and Corneal Thickness was in the order
B < A < C, but none of these changes were statistically
significant. The CV was in the order B < C < A at all
visits with significantly lower CV in B versus A at
CDE= cumulative dissipated energy, TAT= total aspiration time, EFU=
estimated fluid usage
aCorrelation is significant at the 0.01 level (2-tailed)
3 months and 6 months postop, while the hexagonal
endothelial cell count was in the order A > B > C at
1 week and 1 month and A > C > B at 3 and 6 months
with significantly higher counts in A vs. B only at the
one week postop visit (Table 4).
As absolute values may not be representative especially
when baseline values of each cornea change its
susceptibility to endothelial damage, it is more relevant to study
the change in parameters over time and compare
between the three intervention groups. An analysis was
done to compare percentage changes from baseline in
endothelial parameters between the three groups at each
follow up visit. Percentage changes were calculated as
difference between final & baseline values divided by
baseline values and multiplied by 100.
Initially, significantly lower percentage losses in ECD
were seen in group A in comparison to group B as well
as group C at 1 week, and in group A versus group C at
1 month. However, there was no significant difference in
percentage losses in cell density among the three groups
at the 3 months follow up. But by 6 months, losses were
significantly lower only in group C as compared to
group B. Significantly higher increase in CCT was seen
in group B in comparison to both the other groups at
1 week and in comparison to group A at 1 month.
However, there was no significant difference in percentage
change in corneal thickness among the three groups at
3 months follow up. In all groups, CCT decreased over
time but the decrease was significantly lower in group B
as compared to group A at 6 months.
Significant increase in CV was seen in group C in
comparison to groups A and B and in group B in
comparison to group A at 1 week. The increase in CV
remained significant higher in group C versus group A
and B at all postoperative visits.
There was no significant difference in change in
hexagonal endothelial cell count between three groups
at 1 week follow up; however, the change in hexagonal
endothelial cell count was significantly lower in group C
in comparison to groups A and B at 1, 3 and 6 months
follow up (Table 5).
As age and nuclear grade can affect endothelial cell
loss, we asked if there were any endothelial salvaging
effects with respect to the phacoemulsification system
used. An ANCOVA test was performed to compare
changes in the endothelium after adjusting for these
confounders. Interestingly, even after adjusting for these
variables, the results remained significant (Table 6).
A lower CDE is one parameter that all surgeons vie to
achieve due to the obvious benefits of reduced energy
delivery, which correlates with less damage to the
endothelium and lower complication rates [
CDE= cumulative dissipated energy, EFU= estimated fluid usage, TAT= total aspiration time
phacoemulsification reduces energy delivery in the eye
in comparison to longitudinal phacoemulsification [
In addition, better fluidic management increases the
efficiency of phacoemulsification to result in lower energy
delivery and at the same time, a stable anterior chamber
correlates with lower endothelial cell loss [
While previous machines have traditionally used
gravity fed infusion systems, some drawbacks were
]. An attempt was made to use more stable
modalities like an air pump or pressurised irrigation
bottle with gas with some benefits. However, as the gas
infusion pressure does not necessarily vary in response
to the changing aspiration flow rate, the effect is the
same as raising the bottle height [
]. More recent
machines maintain IOP by using a compliant irrigation
bag, which is squeezed in response to the aspiration flow
rate and estimated incision leakage. Centurion uses an
Active Fluidics Technology as compared to a gravity fed
infusion system in the Infiniti .
Instead of a bag or bottle suspended above the machine
to use gravity as just described, there is a compartment
into which a bag of balanced salt solution (BSS) (Alcon
Laboratories, Inc.) is placed between two paddles. The bag is
made of a polymer which, under the pressures to which it
is subjected, is almost stretch-free. This means that very
small and precise movements of the electronically
controlled paddles against the bag are designed to lead to
exquisite control of the fluid entering the eye. This control is
part of the technology called ACTIVE FLUIDICS, which
allows the surgeon to choose a target IOP. To assist in the
way the paddles move, the outflow and inflow from the
CENTURION Vision System are monitored by pressure
sensors on the Fluidics Management System (FMS). To
speed the responsiveness and thus rise time, there are two
rotary valves. The pump itself now has seven rollers,
compared with four on the INFINITI Vision System (Alcon
Laboratories, Inc.). These seven rollers act on the entire 360°
of the tubing in which they are in contact, compared with
only 180° on the INFINITI Vision System. This again is
designed to lead to improved response times. The
aspiration tubing has a reduced inner diameter of 0.048 mm in
comparison to 0.057 mm of the Intrepid plus FMS being
used in the INFINITI and is also very difficult to compress.
This is designed to have two effects: firstly, to increase
resistance to flow; and second, to prevent any tubing from
collapsing, which can reduce post-occlusion surge and
thus increase anterior chamber stability. This system
therefore provides an active control of infusion
pressure to maintain a more stable target IOP level in
spite of variations in aspiration flow rates [
An experimental study with the Infiniti versus
Centurion Gravity versus Centurion Active has shown better
IOP maintenance and thus surge protection with
Centurion Active as compared to other gravity fed systems
at increasing aspiration flow rates. However, in view of
an artificial anterior chamber used in the study, it was
recommended that comparative studies are performed
using the tissue globe environment [
4, 5, 12
Previous studies have shown lowered CDE in the
Centurion as compared to the Infiniti [
According to the manufacturer, two unique
improvements in the Centurion are: active fluid
dynamic management system and use of an Intrepid
balanced tip .
Apart from the surgeon’s skill and technique, use of
torsional phaco instead of longitudinal can have further lowered
CDE and fluid usage if the cutting efficiency of the tip is
maximized. If we try to visualize the tip movement in the lens
during torsional phacoemulsification, two things gain importance.
First, an increasing bevel exposes a greater cross-sectional area
to lens matter, increasing its cutting efficiency. Secondly, the
bend in the shaft of the tip increases the area it traverses on
each stroke so the 22-degree bent 30-degree Kelman
mini-flared tip cuts longer than the 12-degree bent
30-degree mini-flared Kelman tip [
Design of phacotips for torsional
phacoemulsification has evolved over time specially to get the best
out of torsional mode of phacoemulsification. The
Kelman style angled tip was followed by mini flared
ABS Kelman tip and then the 45-degree tip, which
has significantly better cutting action and
repositioning of the lens material than the 30-degree
bevelled tip [
]. Lower CDE and less CCT
changes have been observed with the 45-degree
aperture angled tip than with the 30-degree aperture
angled tip .
ECD 1 week
attributed to the increased emulsification and cavitation
at the sides of the INTREPID balanced tip but no
significant phacotip shaft motion was seen with the balanced
]. An independent comparative study of the
designs of the 45° Kelman and 45° balanced phacotip
showed less total US time, torsional time, CDE and BSS
use as well as similar changes in the ECD with a
balanced tip .
Similar results were reported using these two tip
designs in the CENTURION in patients belonging to the
same ethnic group as us [
]. In our study, we too found
that the use of the Intrepid balanced tip in combination
with Active Fluidics was associated with significant
reduction in CDE, EFU as well as TAT in comparison to
the other groups using a 45° Kelman tip on either a
gravity fed or IOP fed fluidic system.
The reduced energy delivery and stable IOP should
also translate to healthier corneas. There exists a relation
between ultrasound power and corneal endothelium
with increased energy usage being associated with
endothelial cell loss. CDE is only one way of expressing
ultrasonic energy usage. CDE is an estimation of the
energy at the incision site experienced during the removal
of cataractous lens and is measured in %-secs. The
incision is defined as 5.6 mm back from the cutting edge
of the tip. A lower CDE indicates that less energy was
present at the incision site [
]. This should ideally
reflect higher incision burn with increased CDE [
But what we are interested in is not just the effect on
the endothelium at the incision site but the overall
health of the entire and more usefully central
endothelium. Comparing CDE with tip designs varying in length
may not exactly be representative as ideal comparisons
and we might end up comparing apples to oranges
instead of apples to apples [
]. Also, reduced CDE even
though good at incision may not always result in reduced
energy delivery in the anterior chamber if greater tip
excursion and cavitation are being achieved [
This justifies choosing technical modifications that have
equivalent or safer endothelial results if other benefits of
reduced ultrasound time, EFU and in addition, CDE are
present. A previous study comparing 2 tip designs had
revealed that balanced tip use is associated with less total
ultrasound time, torsional time, CDE and BSS use with
similar changes in ECD as with the Kelman tip.
In our study, there was a direct correlation between
CDE and the nuclear grade indicating that higher grades
of cataract required more phaco energy. Similar results
were shown in a study by Liu et al. where increase in
CDE was seen with higher grades of nuclear density
]. We also saw that higher grades of cataract
correlated significantly with increases in CDE, EFU and TAT.
Thus, the changes in endothelial status were compared
across three groups after adjusting for any possible effect
ECD= endothelial cell density, CCT= central corneal thickness, CV= coefficient
of variance, 6A= percentage of hexagonal endothelial cells
However, the Kelman tips have significant motion of
the shaft as well, which can lead to heat production and
undesired corneal changes at the incision. The Intrepid
balanced tip has enhanced sideways displacement at the
tip end and greatly reduced tip action along the shaft. It
has a stroke length of 192 μm at 100% OZIL as
compared to 130 μm at 100% OZIL with 45° Kelman
miniflare ABS. Lower CDE and no wound changes are
of age and nuclear grade and found that at 6 months,
changes in ECD were comparable among 3 groups with
group B showing greater increase in CCT. Although
group C had significantly higher increase in CV than the
other two groups, it had better preservation of hexagonal
endothelial cell counts. This suggested comparable
endothelial safety between three groups with added advantage
of lowered CDE, EFU and TAT in the Centurion with an
Intrepid balanced tip.
Even if we were to correlate CDE with incision
temperature only, we cannot ignore the lowered EFU as
well as TAT with the use of Centurion in the setting of
comparably safe endothelium even up to six months
follow up. Thus, we recommend using the Centurion
system with the Intrepid balanced tip to obtain its
maximum benefit in terms of reduction in CDE, EFU
Use of an IOP based phacoemulsification system in
association with the use of an Intrepid balanced tip
provides comparable endothelial results as well as reduces
the CDE, EFU and TAT versus a gravity fed system with
mini flare tip or IOP based system with mini flare tip.
6A: Hexagonal endothelial cells; BSS: Balanced salt solution; CCT: Central
corneal thickness; CDE: Cumulative dissipated energy; CV: Coefficient of
variance; EFU: Estimated fluid usage; IOP: Intraocular pressure; LOCS III: Lens
opacities classification system ш; NC: Nuclear colour; NO: Nuclear
opalescenceECDEndothelial cell density; OPD: Out patient department;
SD: Standard deviation; TAT: Total aspiration time
Availability of data and materials
Conception,design and drafting the article by Dr. PKM and Dr. TD. Drafting
of article by Dr. AKP. Acquisition and Analysis of data by Dr. ES. All authors
read and approved the final manuscript.
Ethics approval and consent to participate
The study was approved by the Institutional Ethics Committee and consent
of participants were also taken.
Consent for publication
The authors declare that they have no competing interests.
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