1. 9R.R. Krueger et al. (eds.), Textbook of Laser Refractive Cataract Surgery,
DOI 10.1007/978-1-4614-1010-2_2, © Springer Science+Business Media, LLC 2013
As modern small incision cataract surgery is one of
the most successful operations in all of medicine,
how much we can hope to further improve results?
Adopting a more expensive and time-consuming
way to perform the procedure cannot be justified
without providing significant benefits to the patient.
To contemplate the question of where a new tech-
nology might add value, this chapter assesses our
current outcomes of cataract surgery from two van-
tage points—safety and refractive outcomes.
Potential for Improving Safety
Femtosecond (FS) laser cataract technology
automates several delicate and critical steps of
the cataract procedure. These include the pri-
mary and side-port corneal incisions, astigmatic
keratotomy, the continuous circular capsulo-
tomy, and nuclear fragmentation and softening.
When compared to manual performance of
these same functions, we would expect that a
FS laser should offer greater precision and
reproducibility. As only a handful of peer-
reviewed outcome studies are available at this
time (Summer, 2011), we are left to ponder
what the laser technology’s potential impact on
safety and complications will be?
Clear Corneal Incisions
A more precise and reproducible incision would
improve wound integrity. The possible correla-
tion of an increasing postsurgical endophthalmi-
tis rate since 1992 with increasing utilization of
clear corneal incisions was highlighted by Taban
and coauthors in 2005 [1]. This observation
raised the controversial question of whether
clear corneal incisions increased the endophthal-
mitis risk relative to scleral pocket incisions,
because of a higher incidence of subclinical
wound leak. Lacking any randomized prospec-
tive comparative trials, retrospective studies
have provided the only data addressing this
question [2, 3]. One compelling study was
Wallin and coauthors’ 2005 cohort study of 27
consecutive cases of endophthalmitis occurring
at a single institution (Utah) [4]. They deter-
mined that several factors significantly increased
the statistical risk of endophthalmitis at their
institution. Failure to use any antibiotic on the
same day as surgery increased the endophthal-
mitis risk five-fold, while zonular or posterior
capsular rupture increased the endophthalmitis
risk 17-fold. However, the single most danger-
ous factor was an incision leak, which led to a
44-fold increase in endophthalmitis.
Based on the available evidence, many would
agree that clear corneal incisions are less forgiv-
ing than scleral pocket incisions with respect to
poor wound construction both during and after
surgery, and that the risk rises with increasingly
wider incisions [5]. Along with astigmatism
D.F. Chang, M.D. ()
762 Altos Oaks Drive, Suite 1,
Los Altos,
CA 94024, USA
e-mail: dceye@earthlink.net
2Current Outcomes with Cataract
Surgery: Can We Do Better?
David F. Chang
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2. 10 D.F. Chang
control, improved incision integrity is one
advantage cited by proponents of micro-inci-
sional cataract surgery. Regardless of size, pre-
cise and proper wound construction is certainly
important for optimizing wound integrity.
Newer accommodating IOL technologies will
challenge us with the requirement for larger
cataract incisions [6]. Sutures and tissue adhe-
sives will allow us to safely increase the size of
our clear corneal incisions, and the FS laser may
prove to be advantageous in this regard as well.
Continuous Curvilinear Capsulotomy
Long acknowledged by many as the single most
important step of our phaco procedure, the cap-
sulorhexis offers many benefits. By allowing us
to trap and encapsulate the optic and both hap-
tics, IOL centration is virtually assured [7, 8].
An overlapping capsulorhexis enables the cap-
sular bag to envelope the optic with a shrink
wrap effect, by which a sharp posterior optic
edge will kink the posterior capsule [9, 10]. This
mechanical lens epithelial cell barrier reduces
the incidence of secondary membrane forma-
tion. One of the most important benefits of a
capsulorhexis, however, is that of safety. Like
an elastic waistband, the capsulorhexis can
stretch without tearing during the multitude of
maneuvers to which the capsular bag is sub-
jected during cataract surgery. In contrast, a
single radial tear significantly increases the risk
of wraparound extension into the posterior
capsule [11].
Table 2.1 shows data on the incidence of ante-
rior capsule tears reported from four contempo-
rary studies [11–14]. The lowest published rate of
anterior capsular tears comes from Bob Osher’s
personal series of more than 2,600 consecutive
eyes, which was 0.8% [11]. The incidence of
tears occurring during the capsulorhexis step was
0.5%. Of note was the fact that 48% of his ante-
rior capsular tears eventually extended into the
posterior capsule and 19% of cases with a torn
capsulorhexis required an anterior vitrectomy.
This study suggests that the rate of anterior cap-
sular tear is reasonably low in the hands of an
expert surgeon, but that if it occurs, the risk of
significant complications is very high in even the
most experienced hands.
At the other end of the spectrum is the resident
experience reported by Unal and coauthors [13].
The capsulorhexis is consistently cited by resi-
dents as one of the most difficult steps to master
[15]. The rate of torn capsulorhexis in the Unal
series was 5% and of irregular capsulorhexis was
9%. The overall rate of posterior capsule rupture
and vitreous loss was 6.4% [13].
Posterior Capsule Rupture
and Vitreous Loss
Table 2.2 and Fig. 2.1 list 13 studies of vitreous
loss rates in non-resident series published dur-
ing the decade between 1999 and 2009 [16–
28]. Excluding Howard Gimbel’s exceptionally
low rate of 0.2% [20], the vitreous loss rates
Table 2.1 Incidence of anterior capsule tears [11–14]
Study Date AC tear (%) N
Muhtaseb 2004 2.8 1,000
Marques 2006 0.8 2,646
Unal 2006 5.0 296
Olali 2007 5.6 358
[AU1]Table 2.2 Published vitreous loss rates—1999–2009
(0.2–4.4%) [16–28]
Author Published % Vitreous
loss
Study size
Desai 1999 4.4 18,454
Martin 2000 1.3 3,000
Lundstrom 2001 2.2 2,731
Ionides 2001 2.9 1,420
Gimbel 2001 0.2 18,470
Tan 2002 3.6 2,538
Chan 2003 1.1 8,230
Androudi 2004 4.0 543
Hyams 2005 2.0 1,364
Ang 2006 1.1 2,727
Zaidi 2007 1.1 1,000
Mearza 2009 2.7 1,614
Agrawal 2009 1.6 6,564
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3. 112 Current Outcomes with Cataract Surgery: Can We Do Better?
20,000
15,000
10,000
5,000
2,500
7,500
12,500
17,500
0 1 2 3 4 5
Vitreous loss, %
0
Studysize
Desai
1999
Androudi
2004
Tan
2002Ionides
2001
Mearza
2009
Lundstrom
2001
Hyams
2005Zaidi
2007
Ang
2006
Martin
2000
Agrawal
2009
Chan
2003
Gimbel
2001
Fig. 2.1 Studies of vitreous loss rates in non-resident
series published during the decade between 1999 and
2009 [16–28]
2000
1500
1000
500
250
750
1250
1750
1 2 3 4 5 6 7 8
Vitreous loss, %
0
Studysize
Blomquist
2002
Carricondo
2010Lee
2009
Dooley
2006
Rutar
2009
Bhagat
2007
Pot
2008
Blomquist
2010
Fig. 2.2 Studies of vitreous loss rates among residency
programs that were published from 2002 to 2010 [15,
29–35]
consistently range from 1 to 4%. Table 2.3 and
Fig. 2.2 list eight studies of vitreous loss rates
among residency programs that were published
from 2002 to 2010 [15, 29–35]. With the excep-
tion of one study, these rates consistently
ranged from 3 to 6%. The best current pub-
lished data on vitreous loss rates come from
two recent studies of large patient populations.
Narendran and coauthors’ 2009 report on the
Cataract National Dataset audit of 55,567
operations from the United Kingdom (UK)
reported a 1.9% rate of vitreous loss [36].
Greenberg and coauthors’ 2010 published
study of cataract surgery in 45,082 US Veterans
Administration Hospital cataract surgeries had
a vitreous loss rate of 3.5% [37].
Ultrasound Power/Endothelial Cell Loss
A number of studies have shown a reduction in
ultrasound energy when employing a phaco chop
method compared to divide and conquer [38–
41]. The correlation of phaco chop with reduced
endothelial cell loss is less consistent in the lit-
erature [39, 42, 43]. Part of the variability of the
results from these studies undoubtedly relates to
the varying density of the nuclei encountered.
For example, Park and coauthors compared
phaco chop to stop-and-chop in a bilateral eye
study involving 51 patients [44]. There was no
statistical difference in mean effective phaco
time (EPT) for moderately dense nuclei; how-
ever, with dense nuclei, there was a statistically
significant reduction in mean EPT with chop-
ping (P < 0.01). The specific comparison of stop
and chop to pre-chopping may be more relevant
in assessing the FS laser’s potential benefit.
Pereira and coauthors found that pre-chopping
significantly reduced effective phaco time and
phaco power in a small prospective trial of 50
eyes [45].
Despite these reported advantages to chop-
ping, the 2010 Leaming survey of ASCRS mem-
bers reported that only 32% of respondents were
performing phaco chop, compared to 62% who
were performing divide-and-conquer. The fact
Table 2.3 Published vitreous loss rates residents—2002
–2010 (1.3–6.1%) [15, 29–35]
Author Published % Vitreous loss Study size
Blomquist 2002 4.5 1,400
Dooley 2006 4 100
Bhagat 2007 5.4 755
Pot 2008 1.3 982
Rutar 2009 3.1 320
Lee 2009 4.9 226
Carricondo 2010 6.1 261
Blomquist 2010 3.2 1,833
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4. 12 D.F. Chang
that the phaco chop technique is generally more
difficult to learn may be an important factor
underlying these statistics. Reducing ultrasound
time by pre-chopping and softening the nucleus
is an important potential benefit of FS laser cata-
ract surgery. The denser the nucleus, the greater
the ultrasound reduction should be, and the
more likely a clinically significant difference in
endothelial cell loss would be found.
Potential for Improving
Refractive Outcomes
Spherical Equivalent Accuracy
Many factors must be successfully managed to
achieve pseudophakic emmetropia. A major
advance has been in the more accurate determi-
nation of axial length with non-contact, partial
coherence interferometry [47–49]. Two variable
IOL power calculation formulae have been suc-
cessfully used for decades [50–52]. More
advanced formulae, such as those developed by
Haigis and Holladay, incorporate additional vari-
ables in an effort to better predict the effective
lens position [53]. Table 2.4 summarizes six pub-
lished studies that analyze refractive accuracy
[49, 54–58]. Some of these series employed con-
tact A-scan biometry, while others employed par-
tial coherence interferometry. Even in the study
with the best results, 25% of eyes fail to refract to
within 0.5 D of the intended spherical equivalent
target postoperatively.
The one important variable that cannot be
measured in advance is the final axial resting
position of the IOL optic—the so called, effec-
tive lens position (ELP). Calculating a surgeon’s
personalized A-constant is an effort to optimize
the ELP prediction based on variables in indi-
vidual surgical techniques. In addition to capsu-
lar bag fixation of the IOL, the primary surgical
variable that affects ELP is the diameter and
shape of the capsulorhexis [59–61]. The gener-
ally accepted surgical objective is a round capsu-
lorhexis that overlaps the optic edge for all 360°
of its circumference. This means that as the cap-
sular bag shrinks and contracts postoperatively,
the capsular forces are uniformly and symmetri-
cally balanced in all three dimensions. A larger
diameter capsulorhexis that is all or partially
“off ” the optic edge should permit the optic to
move slightly anterior to the position of one con-
strained by a completely overlapping anterior
capsular rim.
Accommodating IOL designs may impose
additional requirements for capsulorhexis diame-
ter and shape. The ELP of a hinged optic, such as
with the Crystalens, would be expected to vary
with the capsulorhexis diameter. If one assumes a
preferred diameter of 5.0 mm, a smaller diameter
capsulorhexis will contract more and may dis-
place the optic more posteriorly. In contrast, a
larger diameter capsulorhexis should allow the
optic to shift more anteriorly. Studies will be
needed to determine whether a FS laser capsulo-
tomy is able to improve refractive outcomes on
the basis of greater ELP predictability. Finally,
there is one special complication that is unique to
premium refractive IOLs—that of a patient receiv-
ing a well-positioned monofocal IOL, but not the
toric, multifocal, or accommodating IOL that
they strongly preferred. For example, with the
synchrony dual optic accommodating IOL, the
Table 2.4 Hitting emmetropia [54–59]
Author N Biometry % Within 0.50 D % Within 1.00 D
Landers (2009) 55 IOLMaster 75 93
Immersion U/S 49 85
Kim (2009) 30 Contact U/S 70 93
Lim (2009) 100 Contact U/S 45 83
Gale (2009) – IOLMaster – 80–87
Eleftheriadis (2003) 100 IOLMaster – 96
Murphy (2002) 1,676 Contact U/S 45 72
Mean 57 87
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5. 132 Current Outcomes with Cataract Surgery: Can We Do Better?
anterior optic shifts forward with accommodative
effort [6]. If the capsulorhexis does not completely
overlap the anterior optic edge, the 5.0 mm diam-
eter anterior optic may partially dislocate out of
the bag and into the ciliary sulcus. A capsulor-
hexis that is too large or eccentric in shape is
therefore a contraindication to implanting the syn-
chrony accommodating IOL. A torn capsulorhexis
is also a contraindication to using the Crystalens,
in my opinion, because of the significant potential
for subluxation. A radial capsulorhexis tear also
increases the potential for single and three-piece
IOL decentration, and may be problematic for a
multifocal or toric IOL where proper optical
alignment is more critical. Although they might
attain excellent corrected visual acuity with an
intracapsular monofocal IOL, these aforemen-
tioned patients are often emotionally distraught at
having permanently lost the opportunity to receive
the premium refractive IOL that they had selected
preoperatively.
Astigmatism Management
The number of cataract surgical patients with
preoperative corneal astigmatism has been
determined from several studies. A published
study of more than 23,000 eyes found that 8% of
patients had at least 2.0 D of corneal astigma-
tism preoperatively [62]. The percent of eyes
with at least 1.0 and 0.5 D of preoperative cor-
neal astigmatism were 36 and 74% respectively.
This correlated well with a study of more than
4,500 eyes in which 35% of eyes had at least
1.0 D, and 22% had at least 1.5 D of preopera-
tive corneal astigmatism [63].
Incisional astigmatic keratotomy (AK) is a
popular method of simultaneously reducing pre-
operative corneal astigmatism at the time of cata-
ract surgery [64]. There is a relative dearth of
published studies on the efficacy of this method
in conjunction with phaco. Carvalho and coau-
thors found a statistically significant reduction in
mean topographic astigmatism from 1.93 ± 0.58 D
preoperatively to 1.02 ± 0.60 D postoperatively
using limbal relaxing incisions in 25 eyes [65].
Mingo-Botín and coauthors compared toric IOLs
to incisional astigmatic keratotomy in 40 eyes
undergoing cataract surgery who were random-
ized to either technique of astigmatism reduction
[66]. The mean reduction in keratometric astig-
matism was 0.58 D (30% of the preoperative cor-
neal astigmatism) in the 20 eyes receiving AK,
and there was with a statistically significant
reduction in mean pre-op refractive astigmatism
(pre-op −2.17 ± 1.02; post-op −1.32 ± 0.60;
p = 0.001). However, the residual refractive astig-
matism was £1.0 D in only 8/20 eyes (40%)
receiving AK, compared to 18/20 eyes (90%)
receiving a toric IOL. Poll and coauthors achieved
a mean 0.46 D of postoperative astigmatism with
astigmatic keratotomy in 115 eyes undergoing
cataract surgery, which was comparable to toric
IOL results in their series [67].
The largest reported series of eyes undergoing
astigmatic keratotomy combined with phaco is
from Gills, and is shown in Fig. 2.3 [68]. He ana-
lyzed 358 eyes with mild to moderate preopera-
tive astigmatism, of which 74% had more than
1.0 D of astigmatism. The mean preoperative
astigmatism of 1.59 D was reduced to a mean of
0.99 D postoperatively. Sixty-five percent of
these treated eyes had <1 D of keratometric cyl-
inder postoperatively and only 23% had <0.5 D
of astigmatism postoperatively.
In the 2010 Leaming survey, 67% of respon-
dents most often use a toric IOL and 18% of
respondents most often use astigmatic kerato-
tomy to treat pre-existing astigmatism in their
70
60
50
20
0
40
10
30
90
80
100
Percent
Pre-op
Post-op
< 0.5 < 1 < 1.5 < 2
Distribution of K Cylinder
23%
26%
65%
59%
83%
75%
92%
0%
65% < 1 D
23% < 0.5 D
75% < 1 D
n = 358
Fig. 2.3 Gills LRI data. n = 358, Mean pre-op cyl 1.59 D
(mild-moderate astigmatism) [68]
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6. 14 D.F. Chang
cataract patients [46]. Astigmatic keratotomy
will always be plagued by an unavoidable vari-
able—that of the individual tissue response to the
corneal relaxing incision. Nevertheless, it stands
to reason that AK results will be more accurate if
the depth, curvature, length, diameter and axial
orientation of the incisions (upon which the
nomograms are developed and based) are made
as reproducibly consistent as possible. It will be
of great interest to see if FS laser astigmatic kera-
totomy will fulfill this potential.
Key Points
1. The most recent published cataract surgical
studies estimate the rate of vitreous loss to be
2–4%.
2. Thirty-five percent of cataract patients have at
least 1 D of corneal astigmatism.
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9. Author Queries
Chapter No.: 2 0001610159
Queries Details Required Author’s Response
AU1 Please check the caption of all tables.
AU2 Please note that “Take Home Points” has been changed to “Key Points” throughout the
book to maintain consistency.
AU3 As Refs. [49, 54] were identical the latter reference has been deleted and the subsequent
references have been renumbered sequentially. Please check.

10. http://www.springer.com/978-1-4614-1009-6