A Prospective Study of Biometric Stability After Scleral Buckling Surgery

CHEE WAI WONG, MARCUS ANG, ANDREW TSAI, VAL PHUA, AND SHU YEN LEE

PURPOSE: To assess time to stabilization and factors HE USE OF SCLERAL IMPLANTS IN THE TREATMENT OF associated with changes in biometric parameters after rhegmatogenous retinal detachment (RRD) dates scleral buckling (SB). back to 1937, when Jess reported the use of a gauze T 1 DESIGN: Prospective case series. pad as the scleral implant. Schepens and associates intro- METHODS: Seventeen eyes with primary rhegmatoge- duced the modern scleral buckling (SB) technique in 1957, nous retinal detachment (RRD) that underwent SB at using a permanent implant such as polyethylene and, later, the Singapore National Eye Centre were enrolled. SB soft silicone rubber.1 This well-tolerated technique surgery was performed using an encircling element and increased the anatomic success rate of SB surgery from segmental buckle. Axial length (AL); anterior chamber 40% to 90%. However, the use of a scleral buckle inher- depth (ACD), defined as the distance from the corneal ently changes the anatomy of the eye. Depending on the epithelium to the anterior lens surface; anterior/posterior type of buckling material used, location, and tension of corneal curvature (K); and refraction were measured scleral sutures with the circumferential tightening of the preoperatively and at week 1 and months 1, 3, 6, 9, and buckle, the resultant geometric changes to the globe can 12 postoperatively. Stability of each parameter was cause visually significant changes. These changes include defined as the earliest time point at which there is no alteration of the axial length (AL),2–11 anterior chamber significant difference compared to its value at month 12. depth (ACD, defined as the distance from the corneal 7,9 RESULTS: AL increased (26.09 ± 1.46 to 26.51 ± 1.96, epithelium to the anterior lens surface), and induced P [ .01), ACD decreased (3.84 ± 0.47 to 3.32 ± 0.57, P spherical or astigmatic refractive errors.3,6,8,10,11 < .001), and a myopic shift of 1.04 diopters (95% CI These biometric changes are important, as cataract 0.03–2.05, P [ .04) occurred at month 12. Anterior/ development and/or progression happen commonly after posterior K were not significantly changed from baseline. vitreoretinal procedures. In the Scleral Buckling versus Pri- AL stabilized at month 3 while ACD and spherical equiv- mary Vitrectomy in RRD trial, almost half of all eyes that alent (SE) stabilized at week 1. Cryotherapy was associ- underwent SB developed or had progression of cataract ated with greater increase in AL (P [ .001) and after a mean follow-up duration of 387.6 6 180.6 days.12 myopic shift (P [ .02). More extensive segmental buck- In another recent study by Feng and Adelman,13 38% of ling was associated with greater increase in AL eyes developed cataracts after SB, of which 5.7% required (P [ .009) and myopic shift (P [ .03). extraction at a mean of 11 months after surgery. Nuclear CONCLUSIONS: Our study suggests that patients sclerosis and posterior subcapsular opacities were the requiring cataract surgery after SB should have biometry most common cataracts after SB.13 In a meta-analysis performed no earlier than 3 months post SB surgery, and done by Lv and associates, cataract formation post scleral intraocular lens power calculation with a fourth- buckle surgery was seen in 23.6% compared with 53.1% generation formula. A greater increase in AL and myopic in eyes that have undergone trans–pars plana vitrectomy shift was associated with cryotherapy and more extensive (TPPV) for primary RRD.14 segmental buckling. (Am J Ophthalmol 2016;165: However, there remains considerable uncertainty 47–53. Ó 2016 Elsevier Inc. All rights reserved.) regarding the optimal timing of biometric assessment and, thereafter, cataract surgery post RRD repair by SB. Some studies have shown changes in axial length and ante- rior chamber depth that continue beyond 12 months, while 2–9 Supplemental Material available at AJO.com. others have shown stabilization within 3 months. Accepted for publication Feb 19, 2016. Moreover, various parameters may be altered From Singapore National Eye Centre (C.W.W., M.A., A.T., V.P., differentially, which makes it difficult to predict how and S.Y.L.), Singapore Eye Research Institute (C.W.W., M.A., A.T., S.Y.L.), Duke-NUS, Department of Ophthalmology and Visual Sciences in which direction the overall refractive power of a post- (M.A., S.Y.L.), Singapore; and Moorfields Eye Hospital, NHS Trust, SB eye will change. Moreover, the effect of SB on posterior London, United Kingdom (M.A.). corneal astigmatism, increasingly recognized as an impor- Inquiries to Adjunct Assoc Prof Shu Yen Lee, Singapore National Eye 15 Centre, 11 Third Hospital Ave, Singapore 168751; e-mail: lee.shu.yen@ tant contributor to the total astigmatism of the eye, is snec.com.sg currently unknown. It is also unknown how other surgical

0002-9394/$36.00 Ó 2016 ELSEVIER INC.ALL RIGHTS RESERVED. 47 http://dx.doi.org/10.1016/j.ajo.2016.02.023 factors, such as the use of cryotherapy, gas tamponade, and 12, adjusting for multiple comparisons with Bonferroni extent of buckling, may influence changes in ocular correction. Stability of each parameter was defined as the biometry. earliest time point at which there was no significant differ- As patients with RRD repaired by SB tend to be younger, ence with its value at month 12. economically active patients,16 accurate biometry is impor- A linear mixed-effects model multivariate analysis was tant to achieve good outcomes should they require cataract conducted to account for repeated measurements and loss surgery subsequently. Thus, we conducted a prospective of some follow-up data. Variance-covariance/correlation longitudinal study to assess the biometric changes after structures such as compound symmetry and independent SB surgery and the influence of surgical factors on biomet- and autoregressive structures were used to estimate the ric changes. model fit based on Hurvich and Tsai’s criterion (AICc) and using the smaller-the-better information criterion. This model was used to analyze the multivariate relation- ship of biometric parameters with clock hours of scleral METHODS buckling, cryotherapy, and endotamponade, adjusting for age and sex. Significance was defined as P < .05. IN THIS PROSPECTIVE STUDY, WE INCLUDED CONSECUTIVE cases with primary RRD requiring SB surgery without vitrectomy, at the Singapore National Eye Centre, be- tween May 2012 and March 2013. The study was performed RESULTS with prospective approval from the Singhealth Institu- tional Review Board and in accordance with the Declara- TABLE 1 SHOWS THE BASELINE DEMOGRAPHICS AND CLIN- tion of Helsinki. Written informed consent was obtained ical characteristics of our study cohort. The mean age was from all participants. All scleral buckling procedures were 47.0 6 13.9 years and 62.5% of subjects were male. Most performed by 4 senior vitreoretinal surgeons using the eyes were phakic with no lens opacity (64.7%) preopera- same surgical technique, briefly: encirclage with silicone tively, while none of the study eyes had proliferative bands (reference number 240; MIRA Inc, Uxbridge, Mas- vitreoretinopathy. The most commonly used segmental sachusetts, USA) and segmental silicone tires. The encir- buckle was the 277 (13 eyes, 76.5%), followed by the cling band was fixed 10–12 mm posterior to the limbus 276 (3 eyes, 17.6%). The vast majority of eyes underwent with a 5.0 nylon suture. External drainage of subretinal drainage of subretinal fluid (94.1%). Gas tamponade was fluid was performed where possible. Retinopexy with performed with either air (41.2%) or sulfur hexafluoride cryotherapy intraoperatively and endotamponade with (47.1%). Intraoperative cryotherapy was the preferred injection of air or an expansile gas were additional proce- method of sealing retinal breaks (70.6%). Primary dures performed at the surgeon’s discretion. Postopera- anatomic success was achieved in 100% of patients. tively, all patients routinely used Tobradex eye drops 4 Three eyes with pre-existing cataract had significant times daily and atropine sulfate 1% 3 times daily for progression of the cataract (17.6%), but none of these 2–4 weeks. The following SB surgery–related variables eyes underwent cataract surgery within the duration of were collected: type and extent of segmental silicone tire, the study. whether subretinal fluid drainage was performed, whether The mean values of biometric parameters at each time cryotherapy or postoperative laser retinopexy was point are shown in Table 2. SB surgery resulted in performed, and the use of endotamponade. significantly longer AL (26.09 6 1.46 mm vs We performed a full clinical evaluation and all measure- 26.51 6 1.96 mm, P ¼ .01) and vitreous length (VL) ments were made pre- and postoperatively at 1 week and at (22.25 6 1.66 mm vs 23.26 6 0.28 mm, P ¼ .001), as 3, 6, 9, and 12 months, specifically: axial length measure- well as shallower ACD (3.84 6 0.47 mm vs ments by IOLMaster (Carl Zeiss Meditec, Jena, Germany; 3.32 6 0.57 mm, P < .001) at 12 months after surgery, software version 5.4), ACD in the horizontal meridian compared to preoperative values. Overall manifest using anterior segment optical coherence tomography astigmatism increased initially at week 1 (ASOCT; Visante; Carl Zeiss Meditec, Jena, Germany; (cylinder: 1.56 6 1.05 diopters [D]) but decreased back software version 3.0),17 automated refraction, automated to preoperative levels at month 12 (0.81 6 0.28 D). keratometry (Topcon KR 8800 Auto-kerato- Both anterior and posterior cornea astigmatism increased refractometer; Topcon Corporation, Tokyo, Japan), and post SB to a maximum of 2.01 6 1.13 D (baseline corneal topography with the Pentacam (Oculus GmbH, 1.26 6 0.67 D) and 0.40 6 0.26 D (baseline 0.24 6 0.20 Wetzlar, Germany; software version 1.17). Statistical anal- D), respectively, at month 3 followed by a decrease and sta- ysis was performed using SPSS software 21.0 (SPSS Inc, bilization thereafter, but remain elevated compared to pre- Chicago, Illinois, USA). To assess stability, paired samples operative values. No statistically significant differences in t test was performed comparing biometric parameters at anterior or posterior corneal keratometry were found be- each time point and their corresponding values at month tween preoperative values and month 12 values.

48 AMERICAN JOURNAL OF OPHTHALMOLOGY MAY 2016 The multivariate associations of cryotherapy, gas tampo- TABLE 1. Baseline Demographic and Clinical Characteristics nade, and extent of SB with AL, ACD, and SE are shown in of a Prospective Series of Patients That Underwent Scleral Table 4. The use of cryotherapy was associated with signif- Buckle Surgery icantly longer AL (mean difference 2.53, 95% CI 1.14–3.92, P ¼ .001) and greater myopic shift (mean Age (y) 47.0 6 13.9 difference 3.66, 95% CI 6.79 to 0.53, P ¼ .02). Simi- Sex (male, %) 10 (62.5) Lens status larly, more than 4 clock hours of segmental buckling was Clear lens 11 (64.7) associated with longer AL (mean difference 0.61, 95% CI Cataract 3 (17.6) 0.50–2.94, P ¼ .009) and greater myopic shift (mean Pseudophakic 3 (17.6) difference 3.09, 95% CI 5.83 to 0.34, P ¼ .03). The Macular detachment (%) 8 (47.1) use of endotamponade was not associated with significant Number of detached retinal quadrants (%) differences in ACD, AL, or SE. 1 7 (41.2) 2 7 (41.2) 3 3 (17.6) Number of retinal breaks (%) 1 14 (82.4) DISCUSSION 2 2 (11.8) 3 1 (5.9) IN THIS PROSPECTIVE STUDY, WE FOUND SIGNIFICANT IN- ¼ Location of retinal breaks (%) crease in AL (P .01) and shallowing of the ACD Superior 9 (52.9) (P < .001) after SB surgery, as well as a trend toward signif- Inferior 8 (47.1) icant myopic shift (P ¼ .05). At month 12, neither poste- Type of buckle (%) rior nor anterior corneal parameters were altered 276 3 (17.6) significantly by SB surgery. While changes in ACD and 277 13 (76.5) SE occurred immediately postoperatively and remained 279 1 (5.9) stable after 1 week, AL continued to increase until postop- Clock hours of buckle (%) erative month 3 before stabilizing. In our study, the mean 3 4 (23.5) increase in AL was 0.58 mm, with a mean myopic shift of 4 4 (23.5) 1.04 D at month 12. As the AL was the last parameter to 5 1 (5.9) 6 8 (47.1) stabilize at 3 months post SB surgery, this suggests that SRF drainage performed (%) 16 (94.1) cataract surgery should be delayed until at least 3 months Endotamponade (%) after SB surgery to improve the predictability of refractive None 2 (11.8) outcomes. In addition, we observed an association between Air 7 (41.2) a greater increase in axial length and greater myopic shift SF6 8 (47.1) with the use of cryotherapy and more extensive segmental Postoperative laser retinopexy 5 (29.4) buckling during SB surgery. Cryotherapy (%) 12 (70.6) Of all the biometric parameters, overall AL is most affected by the placement of a scleral buckle, and is the SF6 ¼ sulfur hexafluoride; SRF ¼ subretinal fluid. main cause of refractive change in patients after SB surgery.2 In most circumstances, the presence of a buckle will cause a change in the shape of the globe from a spher- Table 3 shows the mean difference between values of ical to a prolate configuration, increasing the AL and AL, ACD, and spherical equivalent (SE) at each time inducing a myopic shift.3,5 On the other hand, AL may point and their corresponding values at month 12. decrease if the scleral indent is high because the scleral Comparing preoperative values with the corresponding mattress sutures bring together the sclera anterior and values at month 12, there was a mean increase in AL of posterior to the buckle, causing scleral invagination and 0.58 mm (95% confidence interval [CI] 0.32–0.83, thus shortening the scleral surface.8,11 In general, for low P < .001), a mean decrease in ACD of 0.48 mm (95% to moderate buckle indents, elongation from CI 0.23–0.74, P < .001), and a mean myopic shift of circumferential shortening predominates over shortening 1.04 D (95% CI 0.03–2.05, P ¼ .04). AL continued to in- from scleral invagination. However, it is important to crease until month 3 (P ¼ .49) before stabilization. ACD note that the post-SB AL can continue to increase or decreased initially during the first week (P ¼ .07) and decrease to near baseline levels at various intervals after thereafter stabilized. The myopic shift in SE was observed surgery, depending on the location and tension of scleral to stabilize after the first week (P ¼ 1.00). Anterior and sutures, as well as the tightness of an encircling element. posterior astigmatism/keratometry values did not differ Malukiewicz-Wisniewska and associates reported a median significantly from month 12 values at any time point increase of 0.77 mm in AL after SB surgery, which (all P ¼ 1.00). decreased by 0.20 mm 1 year after treatment.4 Conversely,

VOL. 165 BIOMETRY AFTER SCLERAL BUCKLING SURGERY 49 TABLE 2. Biometric Parameters of a Prospective Series of Patients at Baseline, Week 1, and Months 1, 3, 6, 9, and 12 Post Scleral Buckle Surgery

Baseline Week 1 Month 1 Month 3 Month 6 Month 9 Month 12 Pa

AL (mm) 26.09 6 1.46 25.84 6 1.70 26.29 6 1.82 26.19 6 1.93 26.34 6 1.77 26.58 6 1.85 26.51 6 1.96 .01 ACD (mm) 3.84 6 0.47 3.46 6 0.69 3.39 6 0.50 3.25 6 0.57 3.50 6 0.70 3.26 6 0.49 3.32 6 0.57 <.001 VL (mm) 22.25 6 1.66 22.52 6 1.73 22.97 6 1.82 22.90 6 1.74 22.83 6 1.71 23.32 6 1.63 23.26 6 0.28 .001 Sphere (D) 3.49 6 2.16 3.68 6 4.14 4.39 6 3.54 5.00 6 3.73 5.00 6 3.61 5.20 6 3.35 4.85 6 3.25 .05 Cylinder (D) 0.81 6 0.51 1.56 6 1.05 1.32 6 0.85 1.12 6 0.78 1.05 6 0.47 0.98 6 0.52 0.81 6 0.28 .85 SE (D) 3.89 6 2.34 4.54 6 4.02 5.06 6 3.36 5.56 6 3.69 5.51 6 3.67 5.68 6 3.43 5.25 6 3.32 .05 Anterior cornea 1.26 6 0.67 1.92 6 1.02 2.00 6 1.10 2.01 6 1.13 1.64 6 1.46 1.68 6 1.19 1.66 6 1.19 .50 astigmatism (D) Posterior cornea 0.24 6 0.20 0.40 6 0.26 0.40 6 0.26 0.40 6 0.26 0.36 6 0.25 0.35 6 0.21 0.33 6 0.26 .25 astigmatism (D) Anterior K (D) 42.82 6 1.20 42.74 6 1.52 43.25 6 1.37 43.09 6 1.14 43.09 6 1.31 43.10 6 1.29 43.04 6 1.30 .94 Posterior K (D) 6.19 6 0.38 6.09 6 0.32 6.16 6 0.23 6.19 6 0.28 6.18 6 0.32 6.18 6 0.30 6.21 6 0.35 .79

ACD ¼ anterior chamber depth (distance from the corneal epithelium to the anterior lens surface); AL ¼ axial length; D ¼ diopter; K ¼ kera- tometry; SE ¼ spherical equivalent; VL ¼ vitreous length. aPaired t test comparing value at baseline with value at month 12.

TABLE 3. Change in Mean Value of Biometric Parameters at Each Time Point as Compared to its Mean Value at Month 12 After Scleral Buckle Surgery

Axial Length Anterior Chamber Depth Spherical Equivalent

Mean Differencea 95% CI of Difference Pb Mean Differencea 95% CI of Difference Pb Mean Differencea 95% CI of Difference Pb

Preop 0.58 0.32 to 0.83 <.001 0.48 0.74 to 0.23 <.001 1.04 2.05 to 0.03 .04 Week 1 0.48 0.22 to 0.73 <.001 0.26 0.52 to 0.01 .07 0.41 1.33 to 0.52 1.00 Month 1 0.30 0.06 to 0.55 .008 0.08 0.33 to 0.16 1.00 0.06 0.86 to 0.73 1.00 Month 3 0.17 0.09 to 0.44 .49 0.08 0.18 to 0.33 1.00 0.02 0.83 to 0.87 1.00 Month 6 0.09 0.16 to 0.34 1.00 0.11 0.35 to 0.13 1.00 0.03 0.49 to 1.10 1.00 Month 9 0.02 0.23 to 0.26 1.00 0.12 0.11 to 0.35 .94 0.27 0.52 to 1.06 1.00

CI ¼ confidence interval; Preop ¼ preoperative. aMean difference is given by subtracting the mean at each specified time point from the mean at month 12. bPaired t test adjusted for multiple comparisons with Bonferroni correction.

Goezinne and associates found significantly increased AL mechanism for ACD shallowing post SB surgery has been that persisted over a 12-month period.7 In both studies, attributed to ciliary effusion with anterior rotation of the the surgical technique employed involved the placement ciliary body and consequent anterior movement of the of an encircling band and a radial or segmental buckle. iris-lens diaphragm.18 In another study, Goezinne and asso- This fluctuation in AL may pose a challenge to accurate ciates found that ACD continued to decrease until intraocular lens (IOL) power calculation should a patient 9 months post surgery.7 The absolute change in ACD was develop significant cataract, or require cataract surgery from 3.33 mm to 3.08 mm at 9 months; the ACD then for a pre-existing cataract, after SB surgery. increased to 3.16 mm at 12 months. Other imaging modal- Most studies have reported shallowing of the ACD in the ities have been used to measure ACD, such as the Orbscan initial postoperative period.2,6,7,9 Karti and associates II6 and A-scan ultrasonography,2 with similar findings of found, using ASOCT, that ACD decreased immediately ACD shallowing up to 3 months and 6 weeks, respectively, post SB.9 At 6 months, ACD returned to within post SB. Using the IOLMaster for ACD measurements, we 0.08 mm of baseline, although the difference remained found that ACD decreased immediately post SB and statistically significant. There were no differences in remained shallow thereafter, which may affect the clini- ACD between eyes with air or gas tamponade. The cian’s approach in patients.19 At 1 year, the ACD remained

50 AMERICAN JOURNAL OF OPHTHALMOLOGY MAY 2016 TABLE 4. Associations of Biometric Parameters Post Scleral Buckle Surgery With Surgical Factors

Biometric Parameter Surgical Factor Mean Differencea 95% Confidence Interval of Difference Pb

Anterior chamber depth (mm) Use of endotamponade 0.17 0.99 to 0.65 .67 Cryotherapy 0.16 0.82 to 0.50 .62 >4 clock hours of buckle 0.11 0.69 to 0.47 .69 Axial length (mm) Use of endotamponade 0.18 1.56 to 1.91 .83 Cryotherapy 2.53 1.14 to 3.92 .001 >4 clock hours of buckle 0.61 0.50 to 2.94 .009 Spherical equivalent (mm) Use of endotamponade 1.42 2.47 to 5.30 .45 Cryotherapy 3.66 6.79 to 0.53 .02 >4 clock hours of buckle 3.09 5.83 to 0.34 .03

aDifference between mean of biometric parameter with and without the specified surgical factor. bMultivariable analysis with linear mixed model to account for repeated measurements, adjusted for age and sex.

significantly shallower by approximately 0.5 mm as that remained higher than baseline. Koch and associates compared to baseline, and was not influenced by the use had previously demonstrated that ignoring posterior of endotamponade, cryotherapy, or extent of segmental corneal astigmatism could cause unanticipated outcomes buckling. Thus, several problems may arise in the calcula- in eyes receiving toric IOL implants.15 Thus, it may be pru- tion of IOL power in these patients. Firstly, biometry dent to perform Scheimpflug imaging based corneal topog- performed prior to SB surgery is inaccurate owing to the raphy to assess the contribution of posterior corneal changes in AL and ACD as described above. Second, the astigmatism,24 if toric IOL implantation is considered in combined effect of both an increase in AL and decrease a patient who had previous SB surgery. in ACD will result in significant changes to the IOL power, In order to determine if surgical factors can be manip- even in these longer eyes. Third, the change in relationship ulated for minimizing unwanted changes in biometric between AL and ACD arising from SB surgery may induce parameters, we examined the effect of endotamponade, potential inaccuracy in IOL power calculation with third- cryotherapy, and the extent of segmental buckling on generation IOL calculation formulae that predict effective AL, ACD, and SE. The effect of cryotherapy on axial lens position (ELP) based on AL and keratometry.20 Olsen length and refractive changes was first described in prema- found that postoperative ACD was associated with preop- ture infants following treatment for retinopathy of prema- erative variables including AL, ACD, lens thickness, turity. In a 10-year follow-up study of a randomized cornea curvature, and refraction; of these, the strongest controlled trial, Connolly and associates observed that correlation was with the preoperative phakic ACD eyes treated with cryotherapy were significantly more (r ¼ 0.49, P < .000001).21 In such instances, newer- myopic (mean SE 7.65 D vs 4.48 D for cryotherapy- generation IOL power calculation formulae with modern treated eyes and laser-treated eyes, respectively, ELP prediction algorithms based on preoperative ACD, P ¼ .019) and had longer axial length (mean axial length such as the Haigis,22 Olsen,20 Holladay 2,23 and Hoffer of 21.7 mm vs 22.9 mm for cryotherapy-treated eyes and H-5 formulae will help to improve accuracy. laser-treated eyes, respectively, P ¼ .024) than those Corneal astigmatism has been reported to increase after treated with laser photocoagulation.25 In a recent system- SB surgery.3,4 Cetin and associates studied the effect of SB atic review, Simpson and associates found a similar trend on corneal topography in 32 eyes and found an initial for greater myopia in infants treated with cryotherapy.26 increase in anterior corneal astigmatism that is followed Lee and associates examined the effect of cryotherapy by gradual decrease over the next 3 months.6 Okada and on human scleral tissue by atomic force microscopy and associates found similar increase in corneal astigmatism found significant increase in collagen density and fibril that gradually declined and stabilized at 3 months.11 Of diameter in cryotherapy-treated sclera compared to con- note, there have been no previous studies reporting trols, but how these morphologic changes contribute to changes in posterior cornea astigmatism after SB. In our scleral enlongation remains unclear.27 Here we describe, study, anterior cornea astigmatism increased after SB for the first time, that cryotherapy in adult eyes can surgery until month 3, then decreased slightly and stabi- have the same effect on AL and refractive error as those lized from month 6 but never returned to baseline levels. observed in premature infants. Postoperative laser retino- Posterior cornea astigmatism followed a similar trend, pexy is a viable alternative to cryotherapy to minimize with initial increase until month 3 followed by slight changes in AL and refractive error after SB surgery. decline and stabilization from month 6 onwards at a level With regard to extent of segmental SB, we found more

VOL. 165 BIOMETRY AFTER SCLERAL BUCKLING SURGERY 51 extensive buckling to be associated with longer AL and respectively, as these measurements are likely to be more more myopic refractive error. This is unsurprising, as a precise than those obtained from ultrasonography, which more extensive buckle will result in greater circumferen- was used in other studies.28 Ideally, we would have exam- tial shortening and thus more anteroposterior elongation. ined refractive predictability and compared different surgi- However, it is often not possible to perform less extensive cal techniques—but this was difficult to achieve in a buckling and still achieve adequate support of retinal prospective design of patients who required cataract surgery breaks. If multiple breaks preclude placement of a small soon after SB surgery. We also recognize that our study is segmental buckle, repairing the detachment with TPPV limited by its sample size, a limitation that is compensated with or without an encircling band may minimize the in part by the collection of data over multiple time points increase in AL and myopic shift associated with an exten- and a good follow-up duration of 1 year to ensure all eyes sive segmental buckle. achieved biometric stability for us to satisfactorily reach The observations from our study could have clinical the study’s conclusions. implications for both retina surgeons themselves and cata- In summary, AL and ACD are significantly altered by SB ract surgeons who have been referred patients after SB sur- surgery, with stabilization achieved at least 3 months after gery. Retinal surgeons can minimize SB-induced changes in SB surgery. Greater increase in AL and myopic shift were ocular anatomy by performing intraoperative or postopera- associated with cryotherapy and more extensive segmental tive laser retinopexy instead of cryotherapy. If extensive buckling; replacing cryotherapy with laser retinopexy, or segmental buckling is needed, TPPV should be considered performing TPPV with or without an encircling band in instead. Post-SB patients may also present themselves to lieu of an extensive segmental buckle, are some ways to the cataract surgeon, particularly in countries where retinal minimize these biometric changes. We suggest that the surgeons do not perform cataract surgery. It is thus impor- following measures may improve refractive outcomes for tant for the cataract surgeon to be aware of the implications patients requiring cataract surgery after SB: (1) consider on IOL power calculation. The strength of our study lies in performing IOL power calculations only after 3 months the prospective design over 1 year and the standardized from SB surgery, and (2) using fourth-generation IOL surgical procedure, performed by the same surgeons. We power calculation formulae to improve the accuracy of measured AL and ACD with the IOLMaster and ASOCT, post–cataract surgery refractive outcomes.

FUNDING/SUPPORT: THIS STUDY WAS SUPPORTED BY THE SINGAPORE NATIONAL EYE CENTRE’S HEALTH RESEARCH ENDOW- ment Fund. Financial disclosures: The following authors have no financial disclosures: Chee Wai Wong, Marcus Ang, Andrew Tsai, Val Phua, and Shu Yen Lee. All authors attest that they meet the current ICMJE criteria for authorship.

REFERENCES 8. Grimm G, Aust W, Stark M. [Modification of axial length and astigmatism by scleral buckling surgery]. Klin Monbl 1. Schepens CL, Okamura ID, Brockhurst RJ. The scleral buck- Augenheilkd 1997;210(3):144–146. ling procedures. I. Surgical techniques and management. 9. Karti O, Selver OB, Ozbek Z, et al. Evaluation of corneal AMA Arch Ophthalmol 1957;58(6):797–811. thickness, anterior chamber depth, and iridocorneal angle 2. Burton TC, Herron BE, Ossoinig KC. Axial length changes following scleral buckling surgery with AS-OCT. Ophthalmic after retinal detachment surgery. Am J Ophthalmol 1977; Surg Lasers Imaging 2012;43(6 Suppl):S97–S102. 83(1):59–62. 10. Kinoshita M, Tanihara H, Negi A, et al. Vector analysis of corneal astigmatism after scleral buckling surgery. Ophthalmo- 3. Smiddy WE, Loupe DN, Michels RG, et al. Refractive logica 1994;208(5):250–253. changes after scleral buckling surgery. Arch Ophthalmol 11. Okada Y, Nakamura S, Kubo E, et al. Analysis of changes in 1989;107(10):1469–1471. corneal shape and refraction following scleral buckling sur- 4. Malukiewicz-Wisniewska G, Stafiej J. Changes in axial length gery. Jpn J Ophthalmol 2000;44(2):132–138. after retinal detachment surgery. Eur J Ophthalmol 1999;9(2): 12. Heimann H, Bartz-Schmidt KU, Bornfeld N, et al. Scleral 115–119. buckling versus primary vitrectomy in rhegmatogenous 5. Vukojevic N, Sikic J, Curkovic T, et al. Axial eye length after retinal detachment: a prospective randomized multicenter retinal detachment surgery. Coll Antropol 2005;29(Suppl 1): clinical study. Ophthalmology 2007;114(12):2142–2154. 25–27. 13. Feng H, Adelman RA. Cataract formation following vitreor- 6. Cetin E, Ozbek Z, Saatci AO, Durak I. The effect of scleral etinal procedures. Clin Ophthalmol 2014;8:1957–1965. buckling surgery on corneal astigmatism, corneal thickness, 14. Lv Z, Li Y, Wu Y, Qu Y. Surgical complications of primary and anterior chamber depth. J Refract Surg 2006;22(5): rhegmatogenous retinal detachment: a meta-analysis. PLoS 494–499. One 2015;10(3):e0116493. 7. Goezinne F, La Heij EC, Berendschot TT, et al. Anterior 15. Koch DD, Ali SF, Weikert MP, et al. Contribution of chamber depth is significantly decreased after scleral buckling posterior corneal astigmatism to total corneal astigmatism. surgery. Ophthalmology 2010;117(1):79–85. J Cataract Refract Surg 2012;38(12):2080–2087.

52 AMERICAN JOURNAL OF OPHTHALMOLOGY MAY 2016 16. Wong CW, Wong WL, Yeo IY, et al. Trends and factors 22. Haigis W. Chapter 5. The Haigis formula. In: Shammas HJ, related to outcomes for primary rhegmatogenous retinal ed. Intraocular Lens Power Calculations. Thorofare, NJ: detachment surgery in a large Asian tertiary eye center. Retina Slack; 2003:41–57. 2014;34(4):684–692. 23. Hoffer KJ. Clinical results using the Holladay 2 intraocular lens 17. Ang M, Chong W, Huang H, et al. Comparison of anterior power formula. J Cataract Refract Surg 2000;26(8):1233–1237. segment optical tomography parameters measured using a 24. Pan CW, Cheng CY, Sabanayagam C, et al. Ethnic variation semi-automatic software to standard clinical instruments. in central corneal refractive power and steep cornea in PLoS One 2013;8(6):e65559. Asians. Ophthalmic Epidemiol 2014;21(2):99–105. 18. Kawahara S, Nagai Y, Kawakami E, et al. [Ciliochoroidal 25. Connolly BP, Ng EY, McNamara JA, et al. A comparison of detachment following scleral buckling surgery for rhegmatog- laser photocoagulation with cryotherapy for threshold reti- enous retinal detachment]. Nippon Ganka Gakkai Zasshi 2000; nopathy of prematurity at 10 years: part 2. Refractive 104(5):344–348. outcome. Ophthalmology 2002;109(5):936–941. 19. Ang MH, Baskaran M, Kumar RS, et al. National survey of 26. Simpson JL, Melia M, Yang MB, et al. Current role of ophthalmologists in Singapore for the assessment and man- cryotherapy in retinopathy of prematurity: a report by the agement of asymptomatic angle closure. J Glaucoma 2008; American Academy of Ophthalmology. Ophthalmology 17(1):1–4. 2012;119(4):873–877. 20. Olsen T, Corydon L, Gimbel H. Intraocular lens power 27. Lee SJ, Choi S, Kim MS, et al. Short-term effect of cryo- calculation with an improved anterior chamber depth pre- therapy on human scleral tissue by atomic force microscopy. diction algorithm. J Cataract Refract Surg 1995;21(3): Scanning 2013;35(5):302–307. 313–319. 28. Ang M, Chong W, Tay WT, et al. Anterior segment optical 21. Olsen T. Prediction of the effective postoperative (intraoc- coherence tomography study of the cornea and anterior ular lens) anterior chamber depth. J Cataract Refract Surg segment in adult ethnic South Asian Indian eyes. Invest 2006;32(3):419–424. Ophthalmol Vis Sci 2012;53(1):120–125.

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