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\begin{document}

\title{Comparison of two cataract surgery methods: Phacoemulsification and
nanosecond laser-assisted cataract surgery ---consider ---\textgreater{}
Phacoemulsification with ultrasound versus nanolaser in cataract
surgery: cataract removal efficacy and corneal tissue trauma}



\author[1]{pamattei}%
\author[1]{r.thyzel}%
\author[1]{gangolf.sauder}%
\author[1]{marion.berne}%
\affil[1]{Affiliation not available}%


\vspace{-1em}



  
  \date{May 25, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
\section{ABSTRACT}

{\label{852965}}

PURPOSE: To evaluate corneal tissue trauma and effectiveness of cataract
surgery using ultrasound (US) phacoemulsification compared to nanosecond
laser technique.

SETTING: Department of Ophthalmology, Charlottenklinik, Stuttgart,
Germany.

DESIGN: Prospective, randomized, double masked, clinical interventional
study.

METHODS: Patients were randomized in two groups. Group 1 received
cataract surgery using ultrasound phacoemulsification and in group 2 the
nanoslaser-assisted cataract surgery was applied. Main outcome measures
included uncorrected visual acuity and distance corrected visual acuity,
corneal endothelial cell count, corneal thickness at the center of the
cornea and operational parameters like mean power consumption, mean
amount/volume of irrigating fluid/balanced salt solution and effective
phaco- or photofragmentation time (EPT).

RESULTS: Phacoemulsification was performed in 29 eyes and 32 eyes had
the nanosecond laser procedure. Uncorrected and corrected distance
visual acuity was not significantly different between the two groups.
Postoperatively, there were no significant between-group differences (p
\textgreater{} 0.05) in the endothelial cell count. The mean endothelial
cell density was 2360 cells/mm \selectlanguage{ngerman}± 54 (SD) preoperatively and 2182 ± 76
cells/mm at 3 months in the US group and 2486 ± 45 cells/mm and 2386 ±
45 cells/mm, respectively, in the laser group. The largest decrement of
endothelial cell count was observed in group 1 compared with
preoperative values after 7 days and after 30 days in group 2. The
central corneal thickness showed also no statistically significant
difference (p \textgreater{} 0.05) between group 1 and 2.~ Both groups
reached a maximum thickness at the 1st day and then returned to
presurgery levels after 90 days. The mean EPT was significantly lower in
the phacoemulsification group (59,7 seconds ± 57,0 {[}SD{]}) than in the
nanolaser group (138,7 ± 68,8 seconds) (p \textless{} 0,0001). There was
a significant difference in the mean energy consumption between the 2
groups (38,5 Joule ± 29,9 (SD) in phacoemulsification group; 1,2 Joule ±
0,7(SD)) in nanolaser group) (p \textless{} 0.0001). At least there also
was a significant between-group difference in the balanced salt solution
volume between group 1 and 2 (33,1 Milliliter ± 37,2 (SD) in
phacoemulsification group; 54,9 Milliliter ± 30,6 (SD)in nanolaser
group).

CONCLUSION: The nanosecond laser procedure was effective in cataract
surgery, reducing the mean energy consumption, while it showed a longer
EPT and a higher volume of balanced salt solution consumption than
cataract surgery using phacoemulsification. The Nanosecond laser also
did not have disadvantages over US phacoemulsification in terms of
corneal tissue trauma and central corneal thickness.%
\end{abstract}\selectlanguage{ngerman}%



\sloppy


\par\null\par\null

\section{INTRODUCTION}

{\label{871248}}\par\null

The eye is the most important sensory organ of the human body. Up to 83
per cent of all impressions are perceived by means of sight and the lost
of this sensory function results in significant restrictions.

Globally, cataract is the second most common reason for visual
impairment, so it is not surprising that cataract surgery is the most
frequently performed surgical procedure in many developed countries.
Still, the surgical procedure~ used to today is far from perfect and
continues to present challenges and risks. Because vision is so
important to quality of life, all medical personnel involved in this
sight-restoring procedure are highly motivated to seek continuous
improvement in surgical outcomes and patient safety. Ultrasound (US)
phacoemulsification has continuously developed and refined since its
introduction in 1967. Today it represents the method of choice for the
effective removal of cataracts.

The evolution of ophthalmological lasers has resulted in the continuous
implementation of newer systems, such as nanosecond laser, in cataract
surgery. Since the first report of "phacolysis of a human cataractous
lens`` by a neodymium:YAG (Nd:YAG) laser in 1991, this technology has
evolved immensly over the last decades. Derived from experience with the
Nd:YAG laser capsulotomy, the Dodick photolysis is based on the physical
principles of plasma formation and shock-wave generation, that are used
for fragmentation of the lens nucleus of cataract patients. Lower energy
consumption during the photolysis process, the ability to eliminate
corneal thermal damage related to phacoemulsification use and the
reduction of potential corneal endothelial loss induced by intraocular
energy release during phacoemulsification seem to be interesting
advantages oft this technique.

The aim of this study was to compare intraoperative effectiveness and
postoperative tissue trauma after using the nanosecond laser-technique
with the results after conventional manual phacoemulsification cataract
surgery.

\par\null\par\null\par\null

\section{PATIENTS AND METHODS}

{\label{459416}}\par\null

A prospective randomized double-masked interventional trial was
performed between March 2014 and March 2015. Recruitment and all
surgical procedures were performed at the Department of Ophthalmology at
the Charlottenklinik in Stuttgart, Germany. This study conformed to the
tenets of the Declaration of Helsinki and was approved by the Ethics
Committee (Bezirks\selectlanguage{ngerman}ärztekammer Nordwürttemberg, Germany). Informed
consent was obtained from all patients.

Sixty-two eyes of 35 cataract patients were enrolled and randomised in
two groups.~ Group 1 received bilateral catarct surgery using
phacoemulsification and in group 2 the nanosecond laser-assisted
cataract surgery was applied in both eyes.

Patients with bilateral visually significant cataracts and a minimum
best corrected visual acuity of 20/100 were eligible for inclusion.
Exclusion criteria included age younger than 50 years, patients with
preexisting low endothelial cell counts (ECCs) (\textless{}1800/mm) or
clinically detectable pathological alterations of the anterior segment
(such as corneal opacities, keratoconus, chronic uveitis, zonular
dialysis, pseudoexfoliation syndrome, glaucoma and diabetes), previous
intraocular inflammation or trauma, other ocular pathologies impairing
visual function and previous anterior or posterior segment surgery. All
surgical procedures were performed by the same experienced surgeon.

\subsection{Examinations}

{\label{707159}}

Preoperatively, all patients had a complete eye examination comprising
uncorrected distance visual acuity, corrected distance visual acuity,
intraocular pressure (IOP) measurement, slitlamp examination of the
anterior and posterior segment with undilated and dilated pupils,
respectively. In addition, data were collected on axial length (AL),
anterior chamber depth (ACD) and biometry measured using partial
coherence interferometry (IOLMaster 500 Carl Zeiss Meditec AG). Biometry
was performed a maximum of 6 months before surgery.

Other evaluations included the endothelial cell count (ECC), measured by
means of noncontact specular microscopy (EM-3000, Tomey Corp.) and
central corneal thickness (CT), measured with a Scheimpflug imaging
system (Pachycam, Oculus Optikgeräte GmbH). Endothelial cell density was
calculated by counting the number of cells within an area of interest of
250 x 250 \selectlanguage{greek}µ\selectlanguage{english}m. Cell densities are reported as number of cells per square
millimeter (cell/mm2).

To classify the cataracts the nuclear opacity (NO) as a measure of
nucleus hardness was chosen from the Lens Opacities Classification
System III (LOCS III).

\par\null

\subsection{Surgical Technique}

{\label{749375}}

The surgical protocol for both groups was based on the standard
small-incision clear corneal technique. The study eye was dilated, and
topical anesthesia was administered repeatedly before the start of the
operation. All surgical procedures were performed using standard
surgical equipment. The basic steps for both techniques included
capsulorrhexis, hydrodissection, hydrodelineation, cataract removal,
cortical cleanup and IOL implantation.

Three clear corneal incisions tunnel were created (2.40 mm main incision
and 2 side ports) with the main incision being on the steepest corneal
meridian.. The capsulorhexis was created using the continuous
curvilinear capsulorhexis (CCC) technique before hydrodissection and
hydrodelineation was done. In all cases, residual cortex was removed
using bimanual irrigation/aspiration. A Venturi-based vacuum systems
with maximal intraoperative aspiration set between 250 and 300 mmHg was
used. After bimanual cortical cleanup the capsular bag was inflated with
sodium hyaluronate 1.0\% (Provisc) and a hydrophobic acrylic IOL (XXXX,
Alcon Surgical, Inc.) was placed in the capsular bag using an IOL
injector. The viscoelastic substance was carefully removed from the
anterior chamber and the capsular bag. After the anterior chamber was
filled with balanced salt solution, the paracenteses were secured by
stromal hydration, no suture was used.

Postoperatively, patients were prescribed topical Moxifloxacin
hydrochloride 5,45 mg 6 times daily for 1 week as well as dexamethasone
1.0 mg 6 times daily for 4 weeks.

\par\null

\subsection{Cataract removal}

{\label{864998}}

In the control group phacoemulsification was performed using a
divide-and-conquer approach or phaco-chop technique (Pentasys 2, Ruck
Company,~ Aachen, Germany) depending on the lens hardness.

In the nanolaser group an updated laser system (Cetus, ARC Laser GmbH)
was used for the cataract extraction. This system is composed by a base
that contains a 1064 nm wavelength Q-switched Nd: YAG laser and an optic
fiber that transmits the laser impulse to a handpiece. The generated
laser pulses are routed via a flexible 340 \selectlanguage{greek}µ\selectlanguage{english}m quartz fiber through the
laser handpiece with a pulse energy of 5,5 mJ/pulse and a pulse duration
of 4 to 5 nanoseconds in a frequency up to 10 Hz. The pulsing photic
energy is focused on a 45 degree bent titanium platelet within the probe
tip and induces an optical breakdown and plasma formation. This creates
a shockwave that emanates from the tip in a cone-like fashion12~ and
leads to a fragmentation of the cataract substance. The disrupted
particles of the cataract are continuously aspirated out of the eye
through a aspiration port within the laser by a Geuder Megatron
irrigation/ aspiration unit.. Irrigation is performed with a separate
handpiece.

For effective fragmentation with this technique intimate contact of the
laser-aspiration probe with the lens material is necessary. The probe
position throughout the photolysis sequence is with the opening facing
posteriorly away from the corneal endothelium. This offers maximal
fragmentation and minimal endothelial surface exposure to released
energy.

The energy required intraoperatively for removal of the cataract is
calculated by the number of laser pulses that are needed for the
fragmentation of the lens nucleus and varies significantly according to
lens density and surgeon experience.

The Cetus nanosecond laser system already received the CE (Conformit\selectlanguage{ngerman}é
Européenne) mark for clinical use within the European Union and 510K
approval from the U.S. Food and Drug Administration for clinical use in
the United States.

\subsection{Main outcome measures}

{\label{559277}}

On the day of surgery the primary evaluted effectiveness endpoint was
the the effective phaco-/photofragmentation time (EPT), which is the
time to emulsify and extract the cataractous lens via the
phacoemulsification or phacolysis probe, respectively. Other
effectiveness endpoints included the mean phaco-/photofragmentation
energy and volume of balanced salt solution used within the eye during
the surgery process. After the completion of the cataract removal and
intraocular lens (IOL) implantation, all patients were evaluated for the
following postoperative parameters (main outcome measures) at 1 day, 7
days, 30 days and 90 days´ follow-up: uncorrected and distance corrected
visual acuity (UDVA and CDVA, respectively), corneal endothelial cell
count and central corneal thickness. However, the measurement of the
central corneal thickness was performed only three times after cataract
surgery (1 day, 30 days and 90 days postoperative).

\subsection{Statistical Analysis}

{\label{897051}}

Sample size estimates for this study were based on the primary outcome
measure of visual acuity at 6-month follow-up. For \selectlanguage{greek}α\selectlanguage{english}=0.05 and 1-\selectlanguage{greek}β\selectlanguage{english}=0.85,
a sample size of 19 patients per group is sufficient to detect mean
differences of one standard deviation or greater with a student's
t-test. A second sample size was calculated for endothelial cell loss
based on the results reported by Tanev et al. (2016) at six months a
level of \selectlanguage{greek}α\selectlanguage{english}=0.05 and \selectlanguage{greek}β\selectlanguage{english}=0.95, yielding a sample size of 30 patients per
group. Anticipating a 5\% loss to follow-up over the original six-month
duration of the study for the larger required sample size, we enrolled
32 patients per group.

Statistical analyses were performed using SPSS software (version 21,
International Business Machines Corp.). For comparison of clinical
characteristics between groups, categorical data were analyzed using the
Wilcoxon-Mann-Whitney U test and continuous data using two-sample t
tests. Differences were accepted as significant when the P value was
less than 0.05.

\par\null

\section{RESULTS}

{\label{113017}}

The study comprised 61 eyes of 35 patients. Phacoemulsification was
performed in 29 eyes and 32 eyes had the nanosecond laser procedure. All
surgeries were uneventful. There were no differences in demographic data
and clinical characteristics between both groups.

\subsection{Visual outcome}

{\label{196153}}

Postoperatively UDVA and CDVA increased significantly in both groups
during the follow-up period. There were not significantly different
between the two groups at different time points. In Group 1, the
uncorrected visual acuity (UDVA) improved from 0,2 (median) at baseline
to 0.6 on the first postoperative day and 0,7 after 3 months. In Group
2, UDVA improved from 0.25 (median) to 0.50 immediately after surgery
and 0.5 at the end of follow- up. Corrected distance visual acuity
(CDVA) improved from 0,5 (median) at baseline to 0.7 on the first
postoperative day and 1,0 after 3 months. In Group 2, CDVA improved from
0.5 (median) to 0.7 immediately after surgery and 0.9 at the end of
follow- up.

\subsection{Intraoperative surgical
parameters}

{\label{657252}}

The mean EPT was statistically significantly less in the
phacoemulsification group (59,7 seconds \selectlanguage{ngerman}± 57,0 {[}SD{]}) than in the
nanolaser group (138,7 ± 68,8 seconds) (p \textless{} 0,0001). The
operating time was less than 14 minutes in all cases, and there were no
complications in either group.

The required energy differed significantly among the 2 groups (p
\textless{} 0.0001).

The mean energy consumption while the phacoemuslification process in
group 1 was~ 41,8 Joule ± 30,9 (SD). During phacolysis the Cetus device
utilized on average 213 pulses of 5,5 mJ per pulse and used a total
energy of~ 1,2 Joule ± 0,7(SD).

At least there also was a significant between-group difference in the
balanced salt solution volume between both groups: 33,1 Milliliter ±
37,2 (SD) in the phacoemulsification group and 54,9 Milliliter ± 30,6
(SD) in the nanolaser group.

\par\null

\subsection{Outcomes in Endothelial cell count and central corneal
thickness}

{\label{749726}}

Preoperatively the two groups did not present statistically significant
differences for corneal endothelial cell count and corneal thickness at
the center of the cornea. Postoperatively, there were no significant
between-group differences (p \textgreater{} 0.05) in the endothelial
cell count. The mean endothelial cell density was 2360~cells/mm ± 54
(SD) preoperatively and 2182~±~76~cells/mm at 3 months in the US group
and 2486~±~45~cells/mm and 2386~±~45~cells/mm, respectively, in the
laser group. The largest decrement of endothelial cell count was
observed in group 1 compared with preoperative values after 7~days and
after 30 days in group 2.

The central corneal thickness showed also no statistically significant
difference (p \textgreater{} 0.05) between group 1 and 2.~ Both groups
reached a maximum thickness at the 1st~day and then returned to
presurgery levels after 90~days.

\par\null

\section{DISCUSSION}

{\label{468119}}

In the present prospective, randomized, double masked, clinical
interventional study, we evaluated the postoperative corneal tissue
trauma and effectiveness of cataract removal using the nanosecond laser
technique and compared it to cataract surgery using the established
ultrasound (US) phacoemulsification.

Over the last 50 years phacoemulsification evolved in technique and
instrumentation and has become the standard of care for patients
undergoing cataract extraction in many parts of the industrialized
world.

The Dodick photolysis system has also experienced significant evolution
in the past 30 years and offers a technically new procedure of cataract
extraction that appears to be an equivalent safe and effective
alternative to phacoemulsification.

Laser energy has attracted interest as a means for cataractous lens
fragmentation because it involves no risk of focal tissue heating, even
under low or no flow of irrigting solution. Ultrasound on the other
hand, emulsifies the crystalline lens through the direct action of the
vibrating phaco needle, the jackhammer effect, and the indirect
cavitation effects of microbubbles that produce heat and pressure and
are believed to be an important factor in phacoemulsification-induced
endothelial cell damage.

Another advantage and contributing factor to the safety of the nanolaser
technology is the reduction of intraocular energy necessary for cataract
removal. Direct and indirect effects of high energy levels during the
fragmentation impair endothelial pump function and lead to corneal
swelling. If endothelial cell damage is sufficiently severe, corneal
decompensation can occur. In this trial, the mean energy used for
cataract extraction performed by Nanolaser was 1,2 J. The energy
required for lens removal with phacoemulsification is 36 times more than
that with photolysis.

The most significant factor for endothelial cell damage an postoperative
corneal edema is phacoemulsification/photofragmentation time.
Kannellopoulos et al. reported that the nanolaser system was safe and
effective for the removal of cataracts up to grade 3. Softer'' nuclei of
NO 1 were removed by the Dodick Photolysis technology in a timeframe
comparable to that of phacoemulsification. Regarding more dense nuclei,
the operative time with this new technology was longer, so that further
improvements in technical- related and surgical-related parameters are
required

In conclusion, the nanosecond laser--assisted cataract surgery has
several potential significant advantages, including a reduced energy and
heat release within the eye in comparison to phacoemulsificatio.
Meanwhile the photofragmentation time is significantly longer and the
consumption of irrigating solution higher than during
phacoemulsification. Moreover both methods leed to a similar extent of
endothelial cell loss and central corneal thickness increase as
conventional phacoemulsification over a 3-month follow-up.

Considering the 50 years developing period of the phacoemulsification
technique, the Dodick photolysis already achieves the same or partly
even better results, despite a much shorter term of
progression.tModifications and a refinement of this methode of
cristalline lens extraction may lead to further improvements in the
cataract surgery and benefits in patient comfort.

\par\null

\selectlanguage{english}
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\end{document}

