J CATARACT REFRACT SURG - VOL 33, JANUARY 2007

Factors influencing refractive outcomes

after combined phacoemulsification

and pars plana vitrectomy

Results of a prospective study

Jin Wook Jeoung, MD, Hum Chung, MD, PhD, Hyeong Gon Yu, MD, PhD

PURPOSE: To evaluate the factors influencing the refractive outcomes of combined phacoemulsifica-tion, foldable intraocular lens (IOL) implantation, and pars plana vitrectomy (PPV).

SETTING: Department of Ophthalmology, Seoul National University Hospital, Seoul, Korea.

METHODS: One hundred fifty-four consecutive patients who had combined phacoemulsification, IOLimplantation, and PPV between September 2001 and August 2004 were enrolled in a prospectivestudy. Refractive, keratometric, and axial length measurements were performed preoperatively and4 months postoperatively. The factors influencing the postoperative refractive outcomes wereanalyzed.

RESULTS: The mean refractive prediction error (ie, actual minus predicted spherical equivalent [SE])was �0.06 diopters (D) G 0.75 (SD). In long eyes (preoperative axial length more than 24.5 mm),the mean predicted SE and actual SE were �0.81 G 0.76 D and �1.24 G 0.79 D, respectively; thedifference was significantly different (P Z .001, paired t test). Patients with a preoperative visual acuityworse than 5/200 and those with preoperative foveal detachment had a significant postoperative my-opic shift (P Z 0.024 and P Z 0.002, respectively; paired t test). Postoperative refractive error was notinfluenced by the intraocular air or gas tamponade during surgery (P Z 0.336, paired t test).

CONCLUSIONS: The combined surgery included a small biometric error that was within the tolerablerange in most cases. However, myopic shifts developed in patients with long axial lengths, poor pre-operative visual acuity, and the preoperative presence of foveal detachment.

J Cataract Refract Surg 2007; 33:108–114 Q 2007 ASCRS and ESCRS

Cataract and vitreoretinal diseases can occur simulta-

neously. Combined phacoemulsification and pars plana vit-

rectomy (PPV) has become a common procedure as a result

of the recent progress in cataract and vitrectomy surgery.

Combined surgery offers immediate visual rehabilitation

and a single recovery period, is cost effective, and is safer

because only 1 anesthesia procedure is required.1–4 Forcombined surgery, intraocular lens (IOL) power is usually

selected by using a common IOL calculation formula for

cataract surgery, such as the SRK II, SRK/T, Holladay 2, or

Hoffer Q.5–8

There have been many reports of combined cataract

and vitrectomy surgery, and the clinical results were gener-

ally favorable.1–4,9–14 As the anatomic success of combined

surgery has improved, greater attention has been directed

Q 2007 ASCRS and ESCRS

Published by Elsevier Inc.

108

toward reducing refractive error to maximize postoperative

visual function. Many variables might have a role in deter-

mining the effect of retinal surgery on postoperative refrac-

tion; these include procedure type, surgical technique,

patient age, and use of adjunctive measures such as silicone

oil.15 However, little is known about the factors influencing

postoperative refraction after combined cataract and vitrec-tomy surgery.

This prospective study was designed to evaluate the

factors influencing refractive outcomes after combined

phacoemulsification, foldable IOL implantation, and PPV.

PATIENTS AND METHODS

This prospective study included consecutive patients whohad combined phacoemulsification, foldable IOL implantation,

0886-3350/07/$-see front matterdoi:10.1016/j.jcrs.2006.09.017

REFRACTION AFTER COMBINED PHACOEMULSIFICATION AND PARS PLANA VITRECTOMY

and PPV between September 2001 and August 2004 at SeoulNational University Hospital. If both eyes of 1 patient had thecombined operations, 1 of the eyes was randomly selected forthe study. Patients were excluded if in-the-bag fixation of theIOL was not performed, silicone oil injection was performed dur-ing the surgery, postoperative anatomical success was notachieved, or additional surgery was performed within 4 monthspostoperatively. Patients with additional encircling or scleralbuckling procedures were also excluded. Informed consent wasobtained from each patient before enrollment. This study adheredto the tenets of the Declaration of Helsinki.

Surgery was done using general anesthesia or a retrobulbarblock. In all cases, a foldable IOL (AcrySof MA60BM, AlconLaboratories, Inc.) with an optic diameter of 6.0 mm was insertedin the capsular bag using a Monarch II IOL delivery system(Alcon Laboratories, Inc.) or a manual folding technique beforethe PPV was performed. Biometric calculations of IOL powerwere performed using the SRK/T linear regression formula.6

The A-constant was set to 118.9 based on the manufacturer’srecommendation.

Before the cataract operation, a 2.75 mm clear corneal inci-sion was made at the 10:30 position. A continuous curvilinear cap-sulorhexis was created, and phacoemulsification and aspirationwere performed. The incision was enlarged to 3.25 mm, and theIOL was implanted in the capsular bag. A standard 3-port vitrec-tomy was performed using a 20-gauge vitreous cutter and an en-doilluminator. The 3-port scleral incisions were made, and aninfusion cannula was inserted inferotemporally. As much of thevitreous was removed as possible, and various vitreoretinal proce-dures, including fluid–air or fluid–gas exchange, endophotocoa-gulation, and cryotherapy, were added when necessary. Thescleral and conjunctival 3-port incisions were closed with 7-0polyglactin (Vicryl).

The spherical equivalent (SE) and keratometric values weremeasured by optometrists using an Auto-Refracto-KeratometerKR-8100 (Topcon Corp.) preoperatively and 4 months postoper-atively. Axial length was also measured preoperatively and postop-eratively with the patient in a seated, upright position usinga model 820 ultrasonic biometer (A-scan, Humphrey Division,Carl Zeiss Ophthalmic Instruments) and Sequoia 512 Acuson(B-scan, Siemens Medical Solutions). Ten axial length measure-ments were taken in each eye, and the mean value was calculated.

The predicted and postoperative manifested refractions, re-fractive prediction error (ie, actual SE minus predicted SE), preop-erative and postoperative axial length measurements, visualacuity, preoperative presence of foveal detachment, and intraocu-lar air or gas tamponade were recorded. The refractive predictionerror was calculated for each patient. The predicted spherical

Accepted for publication September 14, 2006.

From the Departments of Ophthalmology, Seoul National Univer-sity Hospital and Seoul National University College of Medicine,and the Seoul Artificial Eye Center, Seoul National University Hos-pital Clinical Research Institute, Seoul, Korea.

No author has a proprietary or financial interest in any material ormethod mentioned.

Corresponding author: Hyeong Gon Yu, MD, PhD, Department ofOphthalmology, Seoul National University Hospital, #28 Yongon-dong, Chongno-gu, Seoul 110-744, Republic of Korea. E-mail:hgonyu@snu.ac.kr.

J CATARACT REFRACT SURG

postoperative refraction was compared with the actual postopera-tive refraction. The refractive prediction errors were analyzed ac-cording to the preoperative axial lengths. The eyes were classifiedinto 4 groups based on the preoperative axial lengths: less than22.0 mm, 22.0 to 24.5 mm, 24.5 to 26.0 mm, and 26.0 mm or lon-ger. Eyes with an axial length less than 22.0 mm and greater than24.5 mm were classified as short eyes and long eyes, respectively.

In addition, the refractive outcomes in 116 eyes of 116patients (cataract surgery group) who had phacoemulsification,aspiration, and in-the-bag fixation of IOL only were analyzed4 months postoperatively and served as a control group. The re-fractive prediction errors in these eyes were also analyzed accord-ing to the preoperative axial lengths.

The Student t test, paired t test, and simple linear regressionwere used to analyze the refractive outcomes. A P value less than0.05 was considered statistically significant. All analyses were per-formed using SPSS for Windows (version 11.0.0, SPSS, Inc.).

RESULTS

Of the 165 patients who had combined cataract and

vitrectomy surgery and were enrolled in the study, 11 wereexcluded because they were lost to follow-up before

4 months. Thus, 154 eyes of 154 patients were included

in the analysis. All patients had refractive and keratometric

measurements preoperatively and 4 months postopera-

tively. Axial length was measured in all patients preopera-

tively and in 120 patients 4 months postoperatively;

therefore, 34 patients were excluded from the axial length

subanalysis.The mean age of the patients was 60.9 years G

9.4 years (SD) (range 38 to 79 years), and the male-to-fe-

male ratio was 65:89. Table 1 shows the diagnostic sub-

groups of the combined surgery patients. During the

operations, an intraocular air tamponade or gas tamponade

was performed in 5 patients and 82 patients, respectively.

In the combined surgery group, the mean predicted re-

fraction and actual postoperative refraction was �0.46 G0.40 diopters (D) and �0.52 G 0.83 D, respectively; the

difference was not significantly different (P Z.287, paired

t test). The mean refractive prediction error was �0.06 G0.75 D. In the cataract surgery group, the mean predicted

Table 1. Diagnostic subgroup in 154 patients of combined cataract and

vitrectomy surgery.

Diagnostic Subgroup Number of Patients

Diabetic retinopathy 39Macular hole 40Epiretinal membrane 15Rhegmatogenous retinal detachment 23Branch/central retinal vein occlusion 15Other 22Total 154

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REFRACTION AFTER COMBINED PHACOEMULSIFICATION AND PARS PLANA VITRECTOMY

refraction and actual postoperative refraction was�0.53 G0.50 D and �0.50 G 1.08 D, respectively, and the mean

refractive prediction error was C0.03 G 0.90 D. The re-

fractive prediction errors were not significantly different

between 2 groups (P Z .339, Student t test).

Table 2 shows the distributions of refractive predictionerrors after combined cataract and vitrectomy surgery.

When compared with the predicted refraction, the actual

postoperative refraction was within G1.00 D in 81.8% of

eyes and within G2.00 D in 98.1% of eyes.

Table 3 shows the predicted SE and actual SE, refrac-

tive prediction errors, and the statistical test results for pre-

operative axial length, initial visual acuity, preoperative

presence of foveal detachment, and intraocular air or gastamponade in combined surgery patients. In long eyes (pre-

operative axial length O24.5 mm), the mean predicted SE

and actual SE was �0.81 G 0.76 D and �1.24 G 0.79 D,

respectively; the difference was significantly different

(P Z .001, paired t test). The SRK/T formula in the com-

bined surgery group yielded a tendency toward myopia in

long eyes. By simple linear regression analysis, the refrac-

tive prediction errors had a negative correlation with thepreoperative axial length (P Z .001), with a slope of

�0.132 D/mm (Figure 1). In contrast, the refractive pre-

diction errors in the cataract surgery group showed no

significant correlation with the preoperative axial length

(P Z .748, simple correlation analysis).

In addition, patients with a preoperative visual acuity

worse than 5/200 and those with preoperative foveal

detachment had significant postoperative myopic shifts(P Z .024 and P Z .002, respectively; paired t test). How-

ever, the postoperative refractive errors were not influ-

enced by the intraocular air or gas tamponade during

surgery (P Z .336, paired t test).

In combined surgery patients, the axial length

measurements and keratometric values were also analyzed

because the postoperative refractions were mainly deter-

mined by these 2 variables. The axial length measurementin all eyes was not significantly different between pre-

operatively and postoperatively; the mean difference was

C0.03 G 0.20 mm (P Z .067, paired t test). However, in

long eyes, the postoperative axial length was significantly

longer than the preoperative axial length; the mean

J CATARACT REFRACT SURG110

preoperative and postoperative axial length measurements

were 26.39 G 1.39 mm and 26.61 G 1.43 mm, respec-

tively, which was significantly different (P!.001, paired t

test) (Table 4 and Figure 2). In contrast, the mean kerato-

metric value was not significantly different between the

preoperative and postoperative measurements; the meandifference was �0.09 G 1.81 D (P Z .520, paired t test)

(Table 5).

DISCUSSION

The main objective of this study was to evaluate theoverall refractive outcomes after combined phacoemulsifi-

cation, IOL implantation, and PPV. The factors influencing

the postoperative refractive errors were also investigated

using subgroup analysis.

Suzuki et al.16 evaluated the effect of vitrectomy on

postoperative refraction after simultaneous vitrectomy

and cataract surgery. They report that the spread between

the predicted refraction and actual refraction was �0.05G 1.18 D in the combined surgery group and C0.55 G1.32 D in the cataract surgery group. In addition, they sug-

gest that vitrectomy has an effect on postoperative refrac-

tion, with a shift toward myopia when combined with

cataract surgery. Shioya et al.17 report that 36 eyes with

a macular hole in a combined surgery group showed a shift

toward myopia by an average of 0.50 D compared with eyes

in the cataract surgery group. Nishigaki et al.18 comparedthe results between a combined surgery group with diabetic

macular edema and a cataract surgery group. They report

the postoperative refractive error was �0.48 D in the com-

bined surgery group and �0.53 D in the cataract surgery

group. In the present study, the mean refractive prediction

error in the combined surgery group was �0.06 G 0.75 D

and 81.8 % of eyes fell within G1.00 D of the predicted re-

fraction. Therefore, the combined surgery includes a smallbiometric error that is within the tolerable range in most

cases.

In this study, patients who had vitrectomy combined

with a silicone oil injection were excluded to avoid con-

founding effects because additional surgery, including sili-

cone oil removal, might influence the refractive outcome.

Table 2. Distributions of refractive prediction errors after combined phacoemulsification, IOL implantation, and vitrectomy.

Refractive Prediction Error* (D)

Parameter !�2.0 �1.0 to �2.0 �1.0 to C1.0 C1.0 to C2.0 OC2.0

Eyes (%) 1.3 7.8 81.8 8.4 0.6

*Actual minus predicted SE

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Table 3. Predicted and actual SE and refractive prediction errors after combined phacoemulsification, IOL implantation, and vitrectomy.

Mean SE (D) G SD

Parameter Number of Patients Predicted Actual Prediction Error* P Value†

Preop axial length!22.0 8 �0.32 G 0.20 �0.25 G 0.55 C0.07 G 0.67 .76722.0–24.5 115 �0.37 G 0.12 �0.35 G 0.75 C0.02 G 0.75 .73324.5–26.0 17 �0.56 G 0.33 �0.88 G 0.54 �0.32 G 0.59 .043z

O26.0 14 �1.11 G 1.01 �1.68 G 0.84 �0.57 G 0.76 .015z

Preop visual acuity%5/200 52 �0.51 G 0.44 �0.74 G 0.88 �0.23 G 0.73 .024z

O5/200 102 �0.44 G 0.37 �0.42 G 0.78 C0.02 G 0.75 .769Preop foveal detachment

Yes 84 �0.44 G 0.35 �0.69 G 0.82 �0.25 G 0.71 .002z

No 70 �0.49 G 0.45 �0.33 G 0.79 C0.16 G 0.74 .076Intraocular air or gas tamponade

Yes 87 �0.42 G 0.29 �0.50 G 0.84 �0.08 G 0.81 .336No 67 �0.52 G 0.50 �0.56 G 0.82 �0.04 G 0.67 .632

SE Z spherical equivalent

*Actual minus predicted SE†Predicted SE versus actual SE (paired t test)zP!.05

However, in a previous report of cataract surgery combined

with vitrectomy and silicone oil tamponade,19 we reported

that the mean absolute value of the difference between the

predicted refraction and postoperative refraction was

Figure 1. Refractive prediction error (ie, actual SE minus predicted SE) by

axial length in combined cataract and vitrectomy surgery patients.

J CATARACT REFRACT SURG

0.74 D and that compared with the predicted refraction,

the postoperative refraction was within G1.00 D in

67% of eyes and within G2.00 D in all eyes.

In a study of cataract surgery by Olsen,20 54% of the

biometric error was attributed to axial length errors, 38%

to errors in the estimation of the postoperative anteriorchamber depth (ACD), and 8% to corneal power errors.

Our results showed that the SRK/T formula in combined

cataract and vitrectomy surgery has a tendency toward re-

sulting in myopia in long eyes. This myopic shift can, in

part, be explained by the fact that the postoperative axial

length measurements in long eyes were longer than the pre-

operative measurements. Variable factors such as poor fix-

ation, retinal detachment, and posterior staphyloma caninduce an error in the preoperative determination of the

true axial length.

Previous studies of cataract surgery showed a tendency

toward hyperopia rather than myopia in cases of high axial

myopia, probably because of inaccurate estimates of post-

operative ACD, psychophysical factors, or corneal curva-

ture readings.21,22 However, the cataract surgery group in

our study did not show a tendency toward hyperopia ormyopia in eyes with a long axial length. In contrast, our

combined surgery patients with preoperative axial length

greater than 24.5 mm showed a myopic shift without signif-

icant changes in corneal curvature readings. Therefore, the

myopic shift in the combined surgery patients with long

axial lengths may be primarily caused by the errors in axial

length measurements.

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Table 4. Preoperative and postoperative axial length measurements after combined phacoemulsification, IOL implantation, and vitrectomy.

Mean Axial Length (mm) G SD

Parameter Number of Patients Preoperative Postoperative Difference* P value†

Preop axial length (mm)!22.0 7 21.50 G 0.29 21.46 G 0.32 �0.04 G 0.06 .53222.0–24.5 83 23.14 G 0.67 23.12 G 0.71 �0.02 G 0.14 .10124.5–26.0 16 25.33 G 0.34 25.52 G 0.40 C0.19 G 0.25 .009z

O26.0 14 27.61 G 1.09 27.86 G 1.12 C0.25 G 0.23 .002z

Preop visual acuity%5/200 49 24.01 G 1.90 24.11 G 2.00 C0.10 G 0.24 .006z

O5/200 71 23.76 G 1.66 23.75 G 1.77 �0.01 G 0.16 .617Preop foveal detachment

Yes 72 23.92 G 1.78 24.00 G 1.89 C0.08 G 0.22 .004z

No 48 23.76 G 1.73 23.73 G 1.82 �0.03 G 0.14 .142Intraocular air or gas tamponade

Yes 69 23.79 G 1.70 23.82 G 1.81 C0.03 G 0.22 .171No 51 23.96 G 1.84 23.99 G 1.95 C0.03 G 0.17 .220

*Postoperative minus preoperative axial length measurement†Preoperative versus postoperative values (paired t test)zP!.05

The discrepancy between preoperative and postopera-

tive axial length measurements in this study might reflect

a true axial length change that was caused by the combined

vitrectomy surgery. After vitrectomy, scleral thinning or

Figure 2. Preoperative and postoperative axial length measurements in

eyes with a preoperative axial length greater than 24.5 mm in combined

cataract and vitrectomy surgery patients. The diagonal line represents the

ideal correlation between the preoperative and postoperative axial length

measurements. Most results are scattered above this line, suggesting

postoperative axial length was measured longer than preoperative axial

length, particularly in long eyes.

J CATARACT REFRACT SUR112

stretching in or around the sclerotomy sites occurs and

intraocular pressure often rises intraoperatively and post-

operatively. These forces might lead to a true axial length

increment, especially in long eyes in which the axial lengthhas a natural tendency to increase with age.23,24 However,

this is purely speculative. Further studies that include his-

tological confirmation are warranted.

In our patients, the preoperative presence of foveal de-

tachment and poor preoperative visual acuity also signifi-

cantly affected postoperative refraction. The results in

Table 4 suggest that the difference in preoperative and post-

operative axial length measurements might explain the my-opic shifts in these patients. This might be caused by an

error in the preoperative determination of the axial length

resulting from poor fixation, and subsequent myopic shift

was obtained postoperatively.

It is unclear whether the IOL shifts forward in eyes

with air or gas tamponade. Shioya et al.17 report that eyes

with a gas tamponade had a myopic shift compared with

the eyes without a gas tamponade, suggesting that the gastamponade presses the IOL forward and causes the myopic

shift. However, in our study, we did not find more myopic

shift in eyes with air or gas tamponade than in those with-

out tamponade. For confirmation, anatomical studies and

the determination of the postoperative ACD may be

needed.

In summary, there was a small biometric error after

combined cataract and vitrectomy surgery, but it was withinthe tolerable range in most cases. However, myopic shifts

developed in patients with long axial lengths, poor preoper-

ative visual acuity, and the preoperative foveal detachment.

Therefore, simultaneous IOL implantation in combined

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REFRACTION AFTER COMBINED PHACOEMULSIFICATION AND PARS PLANA VITRECTOMY

Table 5. Preopeative and postoperative mean keratometric values after combined phacoemulsification, IOL implantation, and vitrectomy.

Mean Keratometric Value (D) G SD

ParameterNumber

of Patients Preoperative Postoperative Difference* P Value†

Preop axial length (mm)!22.0 8 46.05 G 0.94 46.09 G 0.87 C0.05 G 0.17 .45422.0–24.5 115 44.05 G 1.46 43.93 G 2.54 �0.13 G 2.10 .52324.5–26.0 17 43.43 G 1.14 43.39 G 1.14 �0.04 G 0.16 .255O26.0 14 43.39 G 1.42 43.41 G 1.37 C0.02 G 0.11 .486

Preop visual acuity%5/200 52 43.73 G 1.54 43.76 G 1.56 C0.03 G 0.15 .173O5/200 102 44.20 G 1.44 44.03 G 2.69 �0.17 G 2.28 .477

Preop foveal detachmentYes 84 43.76 G 1.40 43.52 G 2.72 �0.24 G 2.43 .371No 70 44.35 G 1.54 44.43 G 1.64 C0.08 G 0.36 .073

Intraocular air or gas tamponadeYes 87 43.72 G 1.14 44.73 G 1.15 C0.00 G 0.16 .891No 67 44.42 G 1.78 44.20 G 3.28 �0.22 G 2.75 .516

*Postoperative minus preoperative mean keratometric value†Preoperative versus postoperative values (paired t test)

surgery should be performed carefully in these patients be-cause of the relatively poor predictability of postoperative

refraction in these groups.

REFERENCES

1. McElvanney AM, Talbot EM. Posterior chamber lens implantation

combined with pars plana vitrectomy. J Cataract Refract Surg 1997;

23:106–110

2. Koenig SB, Han DP, Mieler WF, et al. Combined phacoemulsification

and pars plana vitrectomy. Arch Ophthalmol 1990; 108:362–364

3. Smiddy WE, Mady M, Anagnoste S. Acrylic intraocular lens placement

in conjunction with pars plana vitrectomy. Am J Ophthalmol 2001;

131:748–750

4. Scharwey K, Pavlovic S, Jacobi KW. Combined clear corneal phacoe-

mulsification, vitreoretinal surgery, and intraocular lens implantation.

J Cataract Refract Surg 1999; 25:693–698

5. Sanders DR, Retzlaff J, Kraff MC. Comparison of the SRK II� formula

and other second generation formulas. J Cataract Refract Surg 1988;

14:136–141

6. Retzlaff JA, Sanders DR, Kraff MC. Development of the SRK/T intraoc-

ular lens implant power calculation formula. J Cataract Refract Surg

1990; 16:333–340; correction, 528

7. Holladay JT, Prager TC, Chandler TY, et al. A three-part system for re-

fining intraocular lens power calculations. J Cataract Refract Surg

1988; 14:17–24

8. Hoffer KJ. The Hoffer Q formula: a comparison of theoretic and regres-

sion formulas. J Cataract Refract Surg 1993; 19:700–712; errata, 1994;

20:677

9. Chung T-Y, Chung H, Lee JH. Combined surgery and sequential sur-

gery comprising phacoemulsification, pars plana vitrectomy, and

intraocular lens implantation; comparison of clinical outcomes.

J Cataract Refract Surg 2002; 28:2001–2005

J CATARACT REFRACT SURG

10. Lam DSC, Young AL, Rao SK, et al. Combined phacoemulsification,

pars plana vitrectomy, and foldable intraocular lens implantation.

J Cataract Refract Surg 2003; 29:1064–1069

11. Heiligenhaus A, Holtkamp A, Koch J, et al. Combined phacoemulsifi-

cation and pars plana vitrectomy: clear corneal versus scleral incisions;

prospective randomized multicenter study. J Cataract Refract Surg

2003; 29:1106–1112

12. Androudi S, Ahmed M, Fiore T, et al. Combined pars plana vitrectomy

and phacoemulsification to restore visual acuity in patients with

chronic uveitis. J Cataract Refract Surg 2005; 31:472–478

13. Chang C-J, Chang Y-H, Chiang S-Y, Lin L-T. Comparison of clear cor-

neal phacoemulsification combined with 25-gauge transconjunctival

sutureless vitrectomy and standard 20-gauge vitrectomy for patients

with cataract and vitreoretinal diseases. J Cataract Refract Surg 2005;

31:1198–1207

14. Hwang J-U, Yoon YH, Kim D-S, Kim J-G. Combined phacoemulsifica-

tion foldable intraocular lens implantation, and 25-gauge transcon-

junctival sutureless vitrectomy. J Cataract Refract Surg 2006;

32:727–731

15. Randleman JB, Hewitt SM, Stulting RD. Refractive changes after poste-

rior segment surgery. Ophthalmol Clin North Am 2004; 17(4):521–526

16. Suzuki Y, Sakuraba T, Mizutani H, et al. Postoperative refractive error

after simultaneous vitrectomy and cataract surgery. Ophthalmic

Surg Lasers 2000; 31:271–275

17. Shioya M, Ogino N, Shinjo U. Change in postoperative refractive error

when vitrectomy is added to intraocular lens implantation. J Cataract

Refract Surg 1997; 23:1217–1220

18. Nishigaki S, Kida Y, Uchida H, et al. [Refractive changes after triple pro-

cedure for diabetic macular edema.] [Japanese] Jpn J Clin Ophthalmol

1998; 52:1135–1137

19. Kim SH, Chung JW, Chung H, Yu HG. Phacoemulsification and foldable

intraocular lens implantation combined with vitrectomy and silicone

oil tamponade for severe proliferative diabetic retinopathy. J Cataract

Refract Surg 2004; 30:1721–1726

20. Olsen T. Sources of error in intraocular lens power calculation. J Cata-

ract Refract Surg 1992; 18:125–129

- VOL 33, JANUARY 2007 113

REFRACTION AFTER COMBINED PHACOEMULSIFICATION AND PARS PLANA VITRECTOMY

21. Tsang CSL, Chong GSL, Yiu EPF, Ho CK. Intraocular lens power calcu-

lation formulas in Chinese eyes with high axial myopia. J Cataract

Refract Surg 2003; 29:1358–1364

22. MacLaren RE, Sagoo MS, Restori M, Allan BD. Biometry accuracy using

zero- and negative-powered intraocular lenses. J Cataract Refract

Surg 2005; 31:280–290

J CATARACT REFRACT SUR114

23. McBrien NA, Adams DW. A longitudinal investigation of adult-onset

and adult-progression of myopia in an occupational group; refractive

and biometric findings. Invest Ophthalmol Vis Sci 1997; 38:321–333

24. Kinge B, Midelfart A, Jacobsen G, Rystad J. Biometric changes in the

eyes of Norwegian university studentsda three-year longitudinal

study. Acta Ophthalmol Scand 1999; 77:648–652

G - VOL 33, JANUARY 2007