Eye (2012) 26, 1459–1464& 2012 Macmillan Publishers Limited All rights reserved 0950-222X/12
www.nature.com/eye

T Iwase1 ; 2 , BC Oveson1 and Y Nishi3

CLINICAL STUDY

Posterior capsule
opacification
following 20- and23-gauge
phacovitrectomy(posterior capsule
opacification
following
phacovitrectomy)
Abstract
Purpose To compare the development of
posterior capsule opacification (PCO) for
idiopathic epi-retinal membrane cases
between 20- and 23-gauge phacovitrectomy.
Methods Cataract surgery ofphacoemulsification with the SA60AT
implantation and 20- or 23-gauge vitrectomy
was performed for 20 patients in bothgroups. Cataract surgery alone was
performed for 50 patients as the control. The
PCO density values were measured using
Scheimpflug video photography at 1 week,
1, 3, 6, 12, 18, and 24 months after surgery.
The number of eyes that required Nd:YAG
laser capsulotomy was also examined.
Results The mean PCO value in the
20-gauge phacovitrectomy group increased
significantly with time (Po0.001), whereas
those in the 23-gauge phacovitrectomy
group and the cataract surgery group did notshow any significant change. Furthermore,
the PCO value in the 20-gauge
phacovitrectomy group was significantly
greater than that in the 23-gauge
phacovitrectomy group at 6, 12, 18 (Po0.05),
and 24 months (Po0.01) after surgery. The
PCO value in the 23-gauge phacovitrectomy
group was significantly greater than that in
the cataract surgery group 24 months after
surgery (Po0.05). The rate of capsulotomy in
the 20-gauge phacovitrectomy group was
significantly higher than that in the cataract
surgery group (P ¼ 0.007), whereas there wasno significant difference between the

23-gauge phacovitrectomy group and thecataract surgery group.
Conclusion PCO rate in eyes with the
23-gauge phacovitrectomy was lower than inthose with the 20-gauge phacovitrectomy, and
PCO rate even in the 23-gauge
phacovitrectomy was higher than in thosewith cataract surgery.
Eye (2012) 26, 1459–1464; doi:10.1038/eye.2012.193;
published online 28 September 2012
Keywords: posterior capsule opacification;
phacovitrectomy; cataract surgery; IOL;
23-gauge vitrectomy; 20-gauge vitrectomy

Introduction
In cases of coexistent cataract and maculardiseases, small-incision phacoemulsification
with implantation of foldable intraocular lenses(IOLs) combined with pars plana vitrectomy(phacovitrectomy) has become a preferable
procedure, because 75–80% of eyes developed
clinically significant cataract within several
years after vitrectomy, requiring subsequentcataract surgery. The added benefit of these
combined procedures includes better
visualization of the posterior segment during
surgery, and offers earlier visual rehabilitation,and reduces the total cost of surgery.1
Posterior capsule opacification (PCO) is still
the most common complication of primarycataract surgery.2 The rate of PCO following
20-gauge phacovitrectomy has been observed

1

Department ofOphthalmology, Wilmer Eye
Institute, The Johns Hopkins
School of Medicine,
Baltimore, MD, USA

2

Department ofOphthalmology, Toyama
Prefectural Central Hospital,
Toyama, Japan3

Department ofOphthalmology, Tokyo
University Hospital, Tokyo,
Japan
Correspondence:
T Iwase, Department ofOphthalmology, Wilmer Eye
Institute, The Johns
Hopkins School of
Medicine, 815 Maumenee,
600N. Wolfe Street,
Baltimore, MD
21287-9277, USA.
Tel: +410 955 4103;
Fax: +410 502 5382;
E-mail: TsuyoshiIwase@
aol.com
Received: 7 March 2012
Accepted in revised form:
16 August 2012
Published online:
28 September 2012

Posterior capsule opacification
T Iwase et al1460

frequently, with reports ranging from 10.3 to 51.1%.3–5
Phacovitrectomy includes a greater number ofprocedural steps compared with cataract surgery.
Rahman et al6 evaluated several factors contributing to
PCO following phacovitrectomy, and concluded thatusing short-acting gas tamponade and avoiding
postoperative posturing may help lower PCO rates.
However, those procedures are required in some retinal
disease, such as rhegmatogenous retinal detachment or
macular hole. Accordingly, the difference between thecharacteristic of patients and the kinds of retinal disease
can affect the resulting outcome; therefore, the selection
bias should be minimized in a study of PCO
development in phacovitrectomy.
In this study, we evaluated the development of PCO
only in idiopathic epi-retinal membrane (ERM) cases
without additional procedures such as laser
photocoagulation or gas tamponade to minimize theselection bias among 20-gauge, 23-gauge
phacovitrectomy, and cataract surgery alone in
implanting a same IOL SA60AT.

Patients and methods
This single-center prospective study was conducted at
the Department of Ophthalmology, Toyama Prefectural
Central Hospital. Surgery was carried out based on theapproval of the Institutional Review Board and theethical standards established by the Declaration of
Helsinki, and informed consent was obtained from all
patients. Data were collected on vitrectomy cases
performed using a 20-gauge system between August andDecember 2005, and vitrectomy cases performed using a
23-gauge system between January and April 2006, andcases performed using phacoemulsification between July
2006 and August 2006 by a single surgeon (TI).
All patients were followed for 24 months after surgery.
Exclusion criteria were: ocular pathology other thansenile cataract and idiopathic ERM, prior history of
intraocular surgery, a pupillary diameter o6.0 mm after
full dilation, uveitis, retinitis pigmentosa,
pseudoexfoliation syndrome glaucoma, axial length
longer than 25 mm or shorter than 21 mm, andperformance of additional procedures such as laser
photocoagulation and gas tamponade during
phacovitrectomy. The continuous curvilinear
capsulorrhexis (CCC) was sized to ensure complete
overlap of the IOL optic during surgery. Cases withintraoperative complications (eg, incomplete CCC,
posterior capsular rupture), and/or with postoperativecomplications (eg, iris synechia), were excluded from thisstudy. Incomplete CCC included anterior capsular crack
formation and incomplete overlap of the IOL optic.

Eye

Degree of inflammation
The degree of anterior segment postoperative
inflammation was graded qualitatively by slit-lamp
examination adapted from Summed Ocular
Inflammation Score (SOIS). Each patient was given aclinical inflammation assessment score:
K

K

Anterior chamber cell count: 0 ¼ no cells, 0.5 ¼ 1–5
cells, 1 ¼ 6–15 cells, 2 ¼ 16–25 cells, 3 ¼ 26–50 cells,
4450 cells.
Anterior chamber flare: 0 ¼ absent, 1 ¼ very slight(barely detectable), 2 ¼ moderate (iris and lens clear),
3 ¼ marked (iris and lens hazy), 4 ¼ intense (fibrinclot).

Assignment of IOLs
Each eye received a hydrophobic acrylic 1-piece IOL(AcrySof SA60AT, Alcon Laboratories, Fort Worth, TX,
USA). The SA60AT IOL has an anterior asymmetricbiconvex optic with a diameter of 6.0 mm, an overall
length of 13.0 mm, supporting haptics of the same soft
acrylic material as the optic, and no haptic angulation(0 degrees).

Surgical technique
After administration of retrobulbar and peribulbar
anesthesia (2% lidocaine hydrochloride), a half-roundfornix-based conjunctival incision was created in the
20-gauge phacovitrectomy group. A 3-mm wide selfsealing sclerocorneal tunnel was created at 12 O’clock inall of the groups. The anterior chamber was filled with aviscoelastic material, and a 5.0–5.25 mm CCC, slightly
smaller than the IOL optic diameter, was made to attaincircumferential 360-degree capsulorhexis-IOL overlap.
Thorough hydrodissection, phacoemulsification of thenucleus, and aspiration of the residual cortex was
performed. The wound was not enlarged and the
SA60AT IOLs were inserted in the capsular bag using theMonarch II injector (Alcon Laboratories). Sutures were
not used to close the sclerocorneal tunnel incision. Aftermaking 3 scleral port (trans-conjunctiva scleral port withtrocars in the 23-gauge phacovitrectomy group),
vitrectomy and ERM peeling without staining were
performed. Each sclerotomy was then closed with a 7.0
vicryl suture in the 20-gauge phacovitrectomy group. No
leakage from sclerotomies was obtained in any case after
intracameral BSS infusion in the both groups. Finally, theconjunctival wound was sutured in the 20-gauge
phacovitrectomy group. Suturing of the scleral ports andthe conjunctiva was not needed in the 23-gauge

Posterior capsule opacification
T Iwase et al1461

phacovitrectomy group. Postoperatively, all patients
received similar routine medication, comprising topicalapplication of diclofenac sodium, 0.1% fluorometholone
and levofloxacin administered four times daily for 1
month.

Measurement of PCO density
The PCO density value was measured using Scheimpflug
video photography7(EAS-1000, NIDEK, Gamagori,
Japan) at 1 week, 1, 3, 6, 12, 18, and 24 months after
surgery. The PCO density value was determined as
below. Scheimpflug slit images of the IOL were taken at
the 01, 451, 901, and 1351 meridians after full dilation of
the pupil. The highest quality image was transferred toan image analysis computer. Axial densitometry wasused to measure the average scattering light density of
the central 3.00  0.25 mm area of the posterior capsule,and of the central 3.00  0.25 mm area of the anterior IOL
surface. The PCO density value was expressed incomputer compatible tape steps (CCT) in which
scattering light density obtained by the densitometry
dividing the range from 0 to 255 (256 steps). The PCO
density value in the cross-sectional image wasdetermined by subtracting the scattering light density of
the anterior IOL surface area from that of the posterior
capsule area. The PCO values of the four meridians werethen averaged and considered to represent the PCO
value.

The rate of Nd:YAG laser capsulotomy
The number of eyes that required Nd:YAG laser
capsulotomy was examined using Kaplan–Meiersurvival analysis. Nd:YAG laser capsulotomy was
performed when an eye lost two or more decimal lines ofacuity or when the patient complained of blurred vision.
For those patients who underwent Nd:YAG laser
capsulotomy, the EAS-1000 value and visual acuity justbefore Nd:YAG laser capsulotomy were used for further
statistical analysis.

Statistical analysis
Normality of data distribution was assessed using theKolmogorov–Smirnov test. Differences in the degree of
IOL movement that showed a normal distribution werecompared using the unpaired t test. Continuous
variables without a normal distribution were comparedusing the Mann–Whitney U test. A repeated-measures
analysis of variance was used to compare differences atthe various examinations. Differences with a P-value lessthan 0.05 were considered statistically significant.

Results
Of the 111 patients that underwent surgery, 21 patientswere excluded based on the exclusion criteria during andafter surgery. The reasons for the exclusions wereincomplete CCC (ie, anterior capsular crack formation
and/or incomplete overlap of the IOL optic) (17patients), posterior capsular rupture (2 patients), andlaser photocoagulation and gas tamponade (2 patients).
Accordingly, 20, 20, and 50 patients were enrolled in the
20-gauge phacovitrectomy group, the 23-gauge
phacovitrectomy group, and the cataract surgery group,
respectively. All procedures were uneventful in all of thegroups. There was no case of postoperative hypotony or
endophthalmitis.
The mean age of the patients was 65.1±7.9 years(range 54–78 years) in the 20-gauge phacovitrectomy
group, 67.0±6.4 years (range 60–81 years) in the
23-gauge phacovitrectomy group, and 68.3±6.5 years(range 56–79 years) in the cataract group. The mean axial
length of the patients was 23.15±1.06 mm (range
21.53–24.56 mm) in the 20-gauge phacovitrectomy
group, 23.41±1.27 mm (range 21.65–24.66 mm) in the
23-gauge phacovitrectomy group, and 23.05±0.99 mm(range 21.13–24.89 mm) in the cataract surgery group (seeTable 1). There was no difference in gender among thegroups.
Figure 1 shows the changes in mean PCO values in thegroups. The mean PCO value in the 20-gauge
phacovitrectomy group increased significantly with time
(Po0.001), whereas that in the 23-gauge phacovitrectomy
group and the cataract surgery group did not show any
significant change. Furthermore, the PCO value in the 20gauge phacovitrectomy group was significantly greaterthan that in the 23-gauge phacovitrectomy group, 6, 12,18, and 24 months after surgery, and the PCO value in the
23-gauge phacovitrectomy group was significantly
greater than that in the cataract surgery group, 24 months
after surgery (Figure 2).
Three (15%) in the 20-gauge phacovitrectomy group, 2(10%) in the 23-gauge phacovitrectomy group, and 1 (2%)

Table 1 Patients’ characteristics
20-Gauge
23-Gauge
phacovitrectomy phacovitrectomy
Number(eyes)
Age (year)
Axial length(mm)
Gender(male/female)

Phaco-only(control)P-value

20

20

50

—

65.1±7.9(54  78)23.15±1.06

67.0±6.4(60  81)23.41±1.27

68.3±6.5(56  79)
23.05±0.99

0.743
0.739

(21.53  24.56) (21.65  24.66) (21.13  24.89)
7/13
8/12
21/29
0.812

Eye

Posterior capsule opacification
T Iwase et al1462

in the cataract surgery group required Nd:YAG laser
capsulotomy within 24 months after surgery (Figure 3).
Kaplan–Meier survival analysis demonstrated that therate of capsulotomy in the 20-gauge phacovitrectomy
group was significantly higher than that in the cataract
surgery group (P ¼ 0.007, Mantel–Cox log-rank test),
whereas there was no significant difference between the
23-gauge phacovitrectomy group and the cataract
surgery group.
Figure 4 shows the ocular inflammation score in thegroups. The mean SOIS score in the 20-gauge
phacovitrectomy group was significantly greater thanthat in the 23-gauge phacovitrectomy group and in thecataract surgery group, 1 and 7 days after surgery(Po0.05).

Figure 1 Changes in mean (SD) posterior capsule opacification(PCO) value in the 20- and 23-gauge phacovitrectomy andcataract surgery groups. The PCO value in 20-gauge phacovitrectomy group increased significantly (Po0.001), whereas thechange in the PCO value was not significant in the 23-gauge
phacovitrectomy or the cataract surgery group. The mean PCO
value in the 20-gauge phacovitrectomy group was significantly
greater than that in the 23-gauge phacovitrectomy group, 6, 12,18, and 24 month after surgery. Also, the PCO value in the
23-gauge group was significantly greater than that in the cataract
surgery group, 24 months after surgery.

Conclusion
With the tremendous advances in surgical techniques
and the improvement of IOLs, the incidence of PCO has
been reduced greatly. However, PCO remains one of themost common complications after cataract surgery.
Numerous investigators have revealed three factors
predominantly contributing to the incidence and degreeof PCO: surgical technique,8–11 IOL design,12,13 and IOL
material. In the present study, the same IOL SA60AT was
implanted in all of the cases, indicating surgicalprocedure (technique) is only difference among thegroups.
Vitrectomy involves various complicated procedures
and there are many variables that can be associated withthe development of PCO compared with cataract surgery.
These include occurrence of intraoperative/
postoperative complications, usage of long acting gas
tamponade, and postoperative posturing.6 Accordingly,

Figure 3 Kaplan–Meier survival plots of the two groups foreyes not requiring Nd:YAG laser posterior capsulotomy. The
survival curve in the 20-gauge phacovitrectomy group was
significantly worse compared with the cataract surgery group(P ¼ 0.007, Mantel–Cox log-rank test), whereas there was no
significant difference between the 23-gauge phacovitrectomy
group and the cataract surgery group.

Figure 2 Representative photographs of eyes following (a) 20-, (b) 23-gauge phacovitrectomy and (c) cataract surgery showing thedevelopment of PCO.

Eye

Posterior capsule opacification
T Iwase et al1463

Figure 4 Mean SOIS at 1, 7, and 30 days following surgery. The
mean SOIS score in the 20-gauge phacovitrectomy group was
significantly greater than that in the 23-gauge phacovitrectomy
group, 1 day after surgery and that in the cataract surgery group,
1 and 7 days after surgery.

the difference between the characteristic of patients andthe kinds of retinal disease can affect the resulting
outcome; therefore, the selection bias should be
minimized in a study of PCO development inphacovitrectomy. There have been a few reports
regarding the development of PCO following
phacovitrectomy.3,4,6,14 However, those studies included
several kinds of disease and used various procedures,
including gas tamponade, indicating that those results
could be affected by selection bias. Thus, in this report,
the same three procedures were performed for each ERM
case; cataract surgery, core vitrectomy, and ERM peeling.
A trim of the peripheral vitreous was not performed inorder to avoid ocular inflammation. Also, in order toavoid unnecessary pressure on the capsular bag, gas
tamponade was not performed. For this study, cases thatwere complicated by additional procedures anddiagnoses other than ERM were excluded. This is why
the number of phacovitrectomy groups is relatively small(20 eyes in each phacovitrectomy group); because thecandidates for this study was narrow in order tominimize selection bias.
To our best knowledge, this is the first reportquantifying PCO in phacovitrectomy using nonqualitative means (EAS-1000, Scheimpflug camera). The
incidence of PCO following 23-gauge phacovitrectomy inthis study is lower than the 20-gauge phacovitrectomy.
Also, selection bias was minimized in our study.
Therefore, these results can be attributed to the smallsized vitrectomy instrument trauma (no conjunctival
peritomy, smaller instruments, and no scleral sutures),because the postoperative intraocular inflammation wasless in smaller gauge phacovitrectomy. Postoperative
inflammation is linked to PCO development andhas been extensively studied in uveitic eyes undergoingcataract surgery, with generally high rates of incidence
being reported (ranging from 10 to 96%).15,16
On the other hand, the incidence of PCO following
23-gauge phacovitrectomy in this study is higher thancataract surgery. Previous studies have reported that
PCO developed more frequently after phacovitrectomy
than after cataract surgery alone. Toda et al5 found that
the PCO rate was 4.2% in the cataract surgery group, and10.3% in the phacovitrectomy group. Mochizuki et al3reported that the PCO rate was 17.9% in phacovitrectomy
group. In the present study, because a relatively lesstraumatic vitrectomy was performed, the procedure does
not seem to cause strong inflammation and actually the
postoperative intraocular inflammation showed nosignificant differences between the 23-gauge
phacovitrectomy and the cataract surgery group.
However, the incidence of PCO in the 23-gauge
phacovitrectomy is still higher. Nishi et al17 concluded
that capsular bend formation is the key to understanding
how some IOLs reduce the incidence of PCO. Both the
sharpness of the bend and the speed of its formation areimportant factors. As there is little posterior pressure ineyes with no vitreous, and capsular bend formation may
require not only a sharp optic edge but also posteriorpressure, it is possible that the IOL edge has a minimal
effect in reducing PCO in phacovitrectomy.18 Also, more
postoperative inflammation probably leads to lensepithelial cell migration and more extensive PCO in thephacovitrectomy.5
On the other hand, Inoue et al19 reported that a
25-gauge vitrectomy group had significantly lesspostoperative ocular inflammation than a 20- or a
23-gauge vitrectomy group in rabbit eyes. Accordingly,
the 25-gauge phacovitrectomy might have lessinflammation than the 23-gauge phacovitrectomy,
resulting in no difference from cataract surgery alone interms of development of PCO.
In conclusion, the results of this study demonstratethat the PCO rate in eyes with the 23-gauge
phacovitrectomy was lower than in those with the
20-gauge phacovitrectomy, and PCO rate even in the
23-gauge phacovitrectomy was higher than that in thosewith cataract surgery. As this study included only ERM
cases, these results may only apply to ERM cases without
additional procedures, such as laser photocoagulation or
gas tamponade, and may not apply to other cases
involving additional procedures. Further studies areneeded to examine the development of PCO between
phacovitrectomy and cataract surgery alone, such as
using a 25-gauge phacovitrectomy.

EyePosterior capsule opacification
T Iwase et al1464

Summary
What was known before
There have been a few reports regarding the development of
posterior capsule opacification (PCO) following
phacovitrectomy. However, those studies included several
kinds of disease and used various procedures, including gas
tamponade, indicating that those results could be affected by
selection bias.

7

8

9
What this study adds
We evaluated the development of PCO with EAS-1000(Scheimpflug camera), only in idiopathic ERM cases without
additional procedures to minimize the selection bias among
20-gauge, 23-gauge phacovitrectomy, and cataract surgery
alone in implanting a same IOL SA60AT. The PCO rate in eyeswith the 23-gauge phacovitrectomy was lower than in thosewith the 20-gauge phacovitrectomy, and PCO rate even in the
23-gauge phacovitrectomy was higher than that in those withcataract surgery.

10

11

12

Conflict of interest

13

The authors declare no conflict of interest.
14

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4
5

6

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