Title page:
Title: Is it worth to convert to microincision phacoemulsification?
Author: Yasser Helmy Mohamed
Lecturer of Ophthalmology, department of Ophthalmology, ElMinia University.
Name: Yasser H Mohamed, MD.
Address: Department of Ophthalmology, El-Minya University
Hospital, El-Minya, Egypt.
E-mail address: helmyyasser@yahoo.com
Telephone number: 012/2190349
Abstract:
Purpose : To compare clinical outcomes of biaxial microincision and coaxial smallincision clear cornea cataract surgery.
Patients and Methods: Forty eyes (20 patients) were randomly operated through clear
corneal incisions using 2 techniques: Microincision cataract surgery was performed
through 1.5, 1.5 mm clear corneal incisions (CCIs) using bimanual sleeveless
phacoemulsification (cool phaco) in 1 eye and usual coaxial phaco was performed on
the other eye through a 3.0 mm CCI. Visual outcomes, astigmatic changes, corneal
thickness, and anterior chamber flare and cells preoperatively and at 1 day, 2 weeks,
and 4 weeks were evaluated and analysed.
Results: All patients in the study underwent uneventful surgery. There were no
relevant clinical differences or intraoperative complications in either group. There
were no significant differences between the techniques regarding the postoperative
iritis, pachymetric measures, astigmatic changes, or visual outcome. There was
statistically significant difference between preoperative and postoperative visual
acuity in both groups (P value= 0.001) along the follow up period. No statistically
significant difference was found between the MICS and coaxial groups regarding the
BCVA all over the postoperative follow up period. Astigmatic change ranged between
0.25 D and 1.25 D with a mean of 0.75D in both groups.
Conclusion: Both techniques were safe and effective for cataract surgery. Bimanual
sleeveless phacoemulsification is similar to a standard phacoemulsification and
allowed excellent visual results in this series of patients.
INTRODUCTION:
Cataract surgery techniques have improved tremendously in recent decades,
starting with the introduction of phacoemulsification in the late 1960s and the
development of foldable intraocular lenses (IOLs) in the late 1980s. These and more
recent innovations have led to surgery being performed through increasingly smaller
self sealing incisions, resulting in improved prognosis for visual acuity (VA), less risk
of surgically induced astigmatism (SIA), and reduce incidence of postoperative
inflammation.(1)
One technique, biaxial microincision clear cornea phacoemulsification, was
first described by Shearing et al in 1985 and is becoming increasingly popular among
cataract surgeons. This procedure uses a separate irrigation instrument and a
sleeveless phaco tip to remove the cataractous lens. Irrigation during phaco is
provided through an irrigating chopper instead of the traditional phaco hand-piece.
As a result, one instrument provides irrigation to the anterior chamber while the other
instrument emulsifies and then aspirates the nucleus. Because irrigation is no longer
provided through the phaco sleeve, a bare needle can be used to emulsify nuclear
fragments.(2)
This technique allows a corneal incision smaller than 1.5 mm but requires
pulsed phaco energy, which prevents the development of high temperatures in the
cornea and therefore reduces the incidence of corneal burns. Because the biaxial
technique involves an incision smaller than that of coaxial technique, one might
expect improved outcomes for biaxial microincision versus coaxial
phacoemulsification.(3)
Microincision cataract surgery provides advantages of wound stability,
improved control and reduced chamber turbulence, resulting in early visual
rehabilitation and improved results. Current techniques rely predominantly on
ultrasound based phacoemulsification, which relies heavily on expensive equipment
and consumables, restricting universal application of this technique particularly in
resource-limited settings such as developing countries.(4)
Lens extraction performed through two paracentesis-type incisions offers
unique advantages that enhance surgical control and safety in cataract and refractive
lens surgery. Understanding the essential features of this lens extraction technique
allows an appreciation of its benefits. Reduction of incision size represents only one
of many potential advantages that make this a superior approach. The crucial
difference is not the size of the incision; it is the separation of inflow and outflow. In
recent years, through several publications in the Journal of Cataract & Refractive
Surgery, several specialists have attempted to document and quantify the effect of
developments in techniques and technology of phacoemulsification.(2-7)
Bimanual microincision phacoemulsification has multiple advantages that
make it a preferred technique even in the absence of microincision IOLs. The growing
trend in bimanualmicroincision phacoemulsification has prompted many surgeons to
evaluate this new surgical technique.(8)
Some believe the technique will become the standard of care in the near
future. Others do not, but they all share their advice for performing it safely and
effectively.
AIM OF THE STUDY:
To compare clinical outcomes of microincision bimanual phacoemulsification
and coaxial clear cornea phacoemulsification.
PATIENTS AND METHODS:
Forty eyes of twenty patients with senile cataracts were randomly operated
through clear corneal incisions using 2 techniques: Microincision cataract surgery
(MICS) was performed through two 1.5 mm clear corneal incisions (CCIs) using
bimanual sleeveless phacoemulsification (cool phaco) in one eye and usual coaxial
phaco was performed on the other eye through a 3.0 mm CCI.
Patients with corneal disorders, contact lens wear, previous intraocular surgery, and a
history of ocular trauma or pathology were excluded from the study. Eyes with more
than 3 diopters (D) of astigmatism were excluded from the study, as astigmatic
incisions would be necessary.
Current technique for bimanual microincision phaco may be reviewed briefly
as follow: two single1.5 mm incisions are made with a disposable knife about 90
degrees apart in the clear cornea. Aqueous is exchanged for a dispersive viscoelastic
and a continuous curvilinear capsulorhexis is constructed with an insulin needle.
Following hydrodissection and hydrodelineation, the nucleus is impaled, chopped and
mobilized using 20-gauge irrigating chopper and a 30-degree beveled straight phaco
needle (Figure1). Epinucleus management permits simultaneous extraction of cortex
in the great majority of cases (Figure2). The capsule and anterior chamber are filled
with a cohesive viscoelastic and separate limbal incisions are performed for IOL
implantation in the bag. The residual viscoelastic is irrigated
In all cases, an AcrySof IOL was inserted. In the microincision group IOL
was implanted through a separate 3.0 mm clear corneal incision at the 12-o' clock
position. No stitches were used in any of the cases in either group. All patients
received postoperative topical antibiotic and corticosteroid treatment. Patients were
examined preoperatively and one day, one week, 2weeks, and 4weeks
postoperatively.
All patients were subjected to full ophthalmological examination both
preoperatively and postoperatively at regular visits. Full ophthalmological
examination includes:
-
Best corrected visual acuity.
-
Slit lamp examination.
-
Applanation tonometry.
-
Fundus examination.
-
Refraction of patients with great care of astigmatic error before and
4weeks after operation.
-
Central corneal pachymetry both preoperatively and after 4weeks
postoperatively using Compuscan UPC1000 Storz.
Evaluation of postoperative iritis in the two groups by careful detection of anterior
chamber flare and cells was encountered during slit lamp examination. Changes in
astigmatic error of all patients in the two groups were calculated and evaluated. Both
intraoperative and postoperative complications in the two groups were encountered.
Changes in the corneal thicknesses in all patients of both groups were calculated and
evaluated.
Figure (1): Showing shopping technique in bimanual phacoemulsification.
Figure (2): Showing process of cortex aspiration in bimanual phacoemulsification.
RESULTS:
All patients (twenty patients, forty eyes) were subjected to uncomplicated
surgical procedures by the same surgeon using the same machine with insertion of a
foldable acrysof intraocular lens. All patients (13 females, 7 males) had senile cataract
with age ranged between 55-70 years old.
Postoperative examination showed no major postoperative complications. No
postoperative detection of anterior chamber flare and cells in all patients of the two
groups along the follow up period.
There was statistically significant difference between preoperative and
postoperative visual acuity in both groups (P value= 0.001) along the follow up
period. No statistically significant difference was found between the MICS and
coaxial groups regarding the BCVA all over the postoperative follow up period. In
both groups, the BCVA was ranged between 6/60 and 6/12 with a mean of 6/18
preoperatively (P value= 0.93). The mean postoperative BCVA in both groups was
6/6 one month postoperatively (P value= 0.974).
There was no statistically significant difference as regards to the postoperative
change in the astigmatic error in patients of the two groups (P value= 0.63) after one
month of follow up. Astigmatic change ranged between 0.25 D and 1.25 D with a
mean of 0.75D in both groups. Astigmatic change between 0.25 and 0.5D was present
in 10% (2 eyes) in both groups. Astigmatic change between 0.5 and 0.75 was present
in 70% (14 eyes) in the coaxial group and in 75% (15 eyes) in group of MICS.
Astigmatic change between 0.75 and 1.0 D was present in 15% (3 eyes) in the coaxial
group and 10% (2 eyes) in the group of MICS. Astigmatic change between 1.0 and
1.25D was found in 5% (one eye) in both groups (Figure 3). In both groups, none of
eyes showed astigmatic change below 0.25 D or above 1.25 D.
Coaxial group
15%
5%
Biaxial group
10%
70%
10%
5%
10%
1- Between0.25 and0.5D
1- Between0.25 and0.5D
2- Between0.50 and0.75D
2- Between0.50 and0.75D
3- Between0.75 and 1.0D
3- Between0.75 and 1.0D
4- Between1.0and1.25D
75%
4- Between1.0and1.25D
Figure (3): Pie chart showing the degree of postoperative astigmatic change in both
groups.
There was no statistically significant value between the two groups as regards
to the pachymetric measures after one month postoperatively(P value= 0.785). Central
corneal thickness ranged between 512 and 532u preoperatively with a mean of 524u
and ranged between 525 and 548u postoperatively with a mean of 538u in the coaxial
group. Central corneal thickness ranged between 519 and 535u preoperatively with a
mean of 526u and ranged between 530 and 551u postoperatively with a mean of 541u
in the MICS group (Figure 4).
Pachymetric changes in both groups
545
540
Preop-Coaxial gp
Postop-Coaxial gp
Preop-Biaxial gp
Postop-Biaxial gp
535
530
525
520
515
1
Figure (4): Column chart showing pachymetric changes in both groups.
DISCUSSION:
The main evolution that cataract surgery experienced during the last decades
has been parallel to the decrease in the incision size. When small incision
phacoemulsification with foldable IOL implantation became the standard technique
for cataract removal, most of the presumed advantages that were anticipated by
pioneers such as Charles Kelman were confirmed. A shorter recovery time, less
surgically induced astigmatism, and improved surgical outcomes were observed.
Because the concept of reducing incision size was clearly related to better surgical
outcomes, modification of the surgical technique was necessary to achieve this goal.(9)
Concurrent improvement in ultrasound technology and instrumentation,
including new IOL technology, accompanied the evolution of new surgical
techniques, resulting in less tissue trauma, less SIA, and faster recovery.(9)
All over the world surgical incisions are becoming smaller and smaller and
more so in ophthalmology. The advent of bimanual phaco has made cataract surgery
now possible through a sub 2 mm incision. With bimanual microincisional
phacoemulsification, we are able to achieve nearly watertight conditions and an
almost completely closed system. We are using smaller incisions, which are
inherently safer, and we have improved followability because the fluid enters the eye
from one side and leaves through the other. This flow avoids creating competing
currents around the phaco tip, such as in coaxial phacoemulsification. In addition, the
incoming irrigation flow can be used as a tissue manipulator, which aids in directing
tissue to the phaco tip.(7)
Alio et al (9) have used the term microincision cataract surgery to describe the
procedure of cataract surgery with IOL implantation through such 2mm
microincisions. Fluidics optimization in MICS aims for an improved control in
pressure and value changes during cataract surgery, which requires a closed and stable
anterior chamber. Using a closed compartment leads to a reduction of fluid circulation
in the anterior chamber.
Investigators are eagerly comparing ways to perform phacoemulsification to
obtain the best results for patients. Bimanual microincision phaco has been receiving
a great deal of attention and is being compared with conventional phaco. The growing
trend in bimanual microincision phacoemulsification has prompted many surgeons to
evaluate this new surgical technique. Some believe the technique will become the
standard of care in the near future. Others do not, but they all share their advice for
performing it safely and effectively.
Bimanual microincision phacoemulsification has multiple advantages that
make it a preferred technique even in the absence of microincision IOLs. The first
point concerns the fluidics. During coaxial phacoemulsification, a portion of the
irrigation fluid is captured by irrigation immediately after it flows out of the sleeve.
Having the irrigation so close to the aspiration means that, the nuclear fragments can
be pushed away. So having the irrigation in one end and the aspiration in another end
means that there is an increase in followability.(2)
The second consideration, having separate irrigation and aspiration, allows
surgeons to use the irrigating fluid like a surgical tool.(2)
There are critics who say there is no role for bimanual microincision phaco
because of the need to enlarge the incision for IOL insertion. However, it is really a
superior method that facilitates cataract surgery in general. Its benefits are not just
about incision size, but it will have added value once microincision IOLs become
available. A variety of names have been used to refer to this procedure. Based on its
defining features, SIMPLE, an acronym for Separate Infusion Microincision
Phacoemulsification Lens Extraction, seems to be a good alternative.(10)
A recent study by Kurz et al (11) compared the outcomes of bimanual
microincision phacoemulsification to coaxial microincision phacoemulsification. This
prospective randomized study of 70 eyes in 70 patients evaluated the intraoperative
parameters of mean phacoemulsification time, total phacoemulsification percentage,
effective phacoemulsification time, total balanced salt solution (BSS) utilized, total
surgical time, and final wound incision size. In addition, the postoperative parameters
of corneal thickness, endothelial cell count, anterior chamber inflammation, visual
acuity, and induced astigmatism by vector analysis were also evaluated.
Both techniques were found to be safe and effective, with the only statistically
significant differences demonstrated being less total volume of BSS utilized and a
lower total surgical time in the bimanual microincision group.
An earlier study by Alio et al (9)comparing bimanual to coaxial microincision
phacoemulsification demonstrated lower mean total phacoemulsification percentage,
lower mean effective phaco time, and less surgically induced astigmatism with the
bimanual technique. There was no difference in the total amount of BSS utilized.
These studies demonstrate the possible advantages of a bimanual technique
over a coaxial approach in regards to both intraoperative and postoperative
parameters. The lack of consistent findings between studies reveals the difficulty of
drawing consistent conclusions regarding these parameters.
Alio et at (9) concluded that, reduction of SIA is the most significant and
important achievement of MICS in their study. A great advantage of MICS surgery is
that the microincisions do not produce an increase in astigmatism, and this is
considered important because cataract surgery today is considered more and more a
refractive procedure.
Alio et at (9) used foldable IOL inserted through 1.5mm corneal incision in the
group of MICS. In this study, there was no difference in both groups as regards to
SIA. This is may be due to the use of usual foldable lenses in both groups with the
same size and site of corneal incision for implantation of IOL.
Alio et al (9) and Kurz et al (11) concluded from their studies that, there were no
statistically different values between the two groups as regards to BCVA, mean flare
value, and mean pachymetric measures. These results are consistent with results in
this study.
Kurz et al (11) and Alio et al (9)used specular microscope to evaluate the
difference between the two groups as regards to endothelial cell count loss. They
concluded that there was no statistically difference between the two groups regarding
the mean percentage of endothelial cell loss. In this study, secular microscopy was not
available to make this comparison. In this study, pachymetric measures used as an
indication of the state of the corneal endothelium and there was no statistically
different values between the two groups after one month postoperatively as regards
pachymetric measures.(12)
Wilczynski M et al (13) compared the two groups as regards BCVA and
endothelial count loss and concluded that there was no significant difference between
BCVA in the two groups postoperatively. Also, Patients in the MICS group lost an
average of 9.5% of corneal endothelial cells, whereas patients after standard
phacoemulsification lost about 7.6% of cells. This difference was statistically
insignificant.
Larger studies with more participants should be carried out to study further the
biochemical changes induced at the level of the cornea, possibility of corneal burns,
amount of leakage, and amout of astigmatism induced by the surgery.
Microincision surgery has become the Holy Grail among cataract surgeons in recent
years. In fact, it’s been the impetus behind the mounting interest in microincision
phacoemulsification. Yet, most ophthalmologists are far from having all the pieces of
the puzzle in place to perform true micro phaco and for the majority of physicians to
adopt it as their technique of choice.(5) Opponents of bimanual microincision surgery
cite the need for a new learning curve, investment in additional instrumentation, and
increased cataract surgical costs. Proponents cite improved “followability,” easier
cortex removal, and safer surgery in difficult cases where 2 similarly sized incisions
give options for approaching the lens from 2 different directions.(14)
Most physicians are sitting on the sidelines, refusing to test the new technique for a
number of reasons. Micro phaco is difficult to learn for the average cataract surgeon,
for it requires two hands instead of one. The learning curve increases the risk for
postoperative complications. There’s no U.S. Food and Drug Administrationapproved intraocular lens designed to fit through a 1.2- to 1.5-mm incision and there
may not be for several years. Presently, cataract surgeons performing micro phaco
have to enlarge these microincisions anyway to fit the current lenses inside the eye. If
you’re not performing micro phaco on your patients currently, don’t feel guilty or
pressured to do so, because true micro phaco is still not ready for prime time.
Hopefully, further comparative studies of these 2 techniques will provide useful
information to help surgeons determine if making a transition to a bimanual technique
is worthwhile.
REFERENCES:
1- Dick HB, Schwenn O, Krummenauer F, et al. Inflammation after
sclerocorneal versus clear corneal tunnel phacoemulsification.
Ophthalmology 2000;107:241-7.
2- Fine IH, Hoffmann RS, Packer M. Optimizing refractive lens exchange
with bimanual microincision phacoemulsification. J cataract Refract
Surg 2004;30:550-4.
3- Olson RJ. Clinical experience with 21-gauge manual
microphacoemulsification using Sovereign WhiteStar technology in
eyes with dense cataract. J Cataract Refract Surg 2004;30:168-72.
4- Donnenfeld ED, Olson RJ, Solomon R, Finger PT, Biser SA, Perry
HD, Doshi
S. Efficacy and wound-temperature gradient of
whitestar. J Cataract Refract Surg. 2003 Jun;29(6):1097-100.
5- Fine IH, Packer M, Hoffman RS. New Phacoemulsification
Technologies.
J Cataract Refract Surg 2002; 28: 1054-1060.
6- Hoffman RS, Fine IH, Packer M, Brown LK. "Comparison of sonic
and ultrasonic phacoemulsification utilizing the Staar Sonic Wave
phacoemulsification system." J Cataract Refract Surg 2002; 28:15811584.
7- Fine IH, Packer M, Hoffman RS. “Power Modulations in New
Technology: Improved Outcomes.” J Cataract Refract Surg 2004;
30:1014-1019.
8- Archinoff SA. Biaxial phacoemulsification [letter]. J Cataract Refract
Surg 2005;31:646.
9- Alio J, Rodriguez-Prats JL, Galal A, Ramzy M. Outcomes of
microincision cataract surgery versus coaxial phacoemulsification.
Ophthalmology 2005;112:1997–2003
10- Osher RH, Barros MG, Marques DM, Marques FF, Osher JM. Early
uncorrected visual acuity as a measurement of the visual outcomes of
contemporary cataract surgery. J Cataract Refract Surg. 2004;30:191720.
11- Kurz S, Krummenauer F, Gabriel P, Pfeiffer N, Dick HB. Biaxial
microincision versus coaxial small-incision clear cornea cataract
surgery. Ophthalmology. 2006 Oct;113(10):1818-26.
12- Lundberg B, Jonsson M, Behndig A. Postoperative corneal swelling
correlates strongly to corneal endothelial cell loss after
phacoemulsification cataract surgery. Am J Ophthalmol. 2005
Jun;139(6):1035-41.
13- Wilczynski M, Drobniewski I, Synder A, Omulecki W. Evaluation of
early corneal endothelial cell loss in bimanual microincision cataract
‫‪surgery (MICS) in comparison with standard phacoemulsification. Eur‬‬
‫‪J Ophthalmol. 2006 Nov-Dec;16(6):798-803.‬‬
‫‪14- Mamalis N. Is smaller better? J Cataract Refract Surg 2003;29:1049‬‬‫‪50.‬‬
‫عنوان البحث‪:‬هل من االجدر التحول الى الشق المجهرى الستحالب العدسه؟‬
‫الغرض من البحث ‪ :‬هو مقارنة بين النتائج االكلينيكيه الزالة المياة البيضاء‬
‫بالموجات فوق الصوتيه احادية المحور و ثنائية المحور‪.‬‬
‫طريقة البحث‪:‬تمت ازالة المياة البيضاء لعشرين مريضا (اربعين عينا) بالموجات‬
‫فوق الصوتية مستخدمين طريقتين‪.‬‬
‫الطريقة االولى هى ثنائية المحور عن طريق شق القرنية شقين كل منها‪ 1¸ 5‬مم‬
‫باستخدام مسبار الموجات فوق الصوتيه منزوع الغطاء (القميص) في احد العينين‬
‫والعين االخرى تمت ازالة المياه البيضاء بالموجات الصوتيه احادية المحور عن‬
‫طريق شق القرنية ‪ 3‬مم‪.‬‬
‫قيمت وحللت نتائج المجموعتين من ناحية النتائج البصرية والتغيرات فى درجة‬
‫االنحراف (االستجماتزم) وسمك القرنيه والتهابات القزحية‪.‬‬
‫نتائج البحث ‪ :‬نتج البحث عن عدم وجود اية اختالفات اكلينيكيه او مضاعفات اثناء‬
‫العمليات للمجموعتين‪.‬‬
‫ليست هناك فروق احصائيه بين الطريقتين من حيث االلتهاب القزحى بعد العملية‬
‫وسمك القرنية ودرجات االنحراف او النتائج البصرية ‪.‬‬
‫يترواح معدل التغير فى درجة االنحراف مابين ‪ 1¸25: 0¸25‬ديوبتر بمتوسط‬
‫يعادل‪ 0¸ 75‬درجة فى كال المجموعتين‪.‬‬
‫خالصة البحث ‪:‬تعتبر كال الطريقتين امان وذات فاعلية الزالة المياة البيضاء جراحيا‬
‫وتكون الطريقة ثنائية المحور مساوية الحادية المحور فى هذه المجموعه البحثيه من‬
‫حيث النتائج البصرية‪.‬‬
Keywords: bimanualphacoemulsification, coaxial
phacoemulsification, microincision-phaco, cold phaco,
pachymetry.