Accepted Manuscript Change in the post-operative refractive outcome following combined phacoemulsification and pars plana vitrectomy for rhegmatogenous retinal detachment Kwan Hyuk Cho, In Won Park, Soon Il Kwon PII:

S0002-9394(14)00226-8

DOI:

10.1016/j.ajo.2014.04.023

Reference:

AJOPHT 8900

To appear in:

American Journal of Ophthalmology

Received Date: 14 January 2014 Revised Date:

24 April 2014

Accepted Date: 25 April 2014

Please cite this article as: Cho KH, Park IW, Kwon SI, Change in the post-operative refractive outcome following combined phacoemulsification and pars plana vitrectomy for rhegmatogenous retinal detachment, American Journal of Ophthalmology (2014), doi: 10.1016/j.ajo.2014.04.023. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Purpose: To evaluate the change in the post-operative refractive outcome following combined phacoemulsification and pars plana vitrectomy(PPV) for rhegmatogenous retinal detachment(RRD) compared with other retinal disease Design: Retrospective observational case-control study

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Methods: Total of 55 patients who had combined surgery between January 2007 to December 2012 were enrolled. The 25 patients who underwent combined surgery for RRD were included in the RRD group and 30 patients who underwent combined surgery for other vitreoretinal pathology were included in the control group. Refractive, axial length(AL), Intraocular pressure(IOP) measurements were performed and the factors influencing the postoperative refractive outcomes were analyzed.

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Results: Mean difference between the postoperative and predicted refractive outcome in the RRD group and the control group was -0.43D ± 0.67 (P=.046) and -0.08D ± 0.53(P =.767) respectively. Mean preoperative IOP of affected eye and fellow eye in the RRD group were 11.44mmHg ± 3.15 and 13.16mmHg ± 2.73 (P=.045). But no difference was found in affected eye and fellow eye of the control group. It was 14.20mmHg ± 2.95 and 14.17mmHg ± 3.50, respectively (P=.974). Mean postoperatively IOP in affected eye and fellow eye of the two groups were not significantly different. For all eye, the refractive difference correlated to IOP change in the RRD group. (r=.659, r2=.435, P27.0 mm, macula off retinal detachment (RD), serous RD, tractional RD, or a coexisting vitreoretinal disorder including glaucoma. Indications of PPV in the control group included diabetic retinopathy, branch or central retinal vein occlusion, macular hole, epiretinal membrane, or vitreous opacity due to previous uveitis. The vitreoretinal disorders that could affect the refractive error, such as macular edema > 300 µm or long axial length > 27.0 mm, were excluded. Additionally, patients being treated with medication to lower IOP were excluded from this study. Optometrists measured the spherical equivalent (SE) and keratometric values using an Auto-Refracto-Keratometer KR-8100 (Topcon Corp., Tokyo, Japan), both preoperatively, and 3 and 6 months post-operatively. In addition, the axial length was measured preoperatively by two physicians to eliminate a corneal indentation bias. The patient was assessed in a seated, upright position, using an ultrasonic biometer model 820 (A-scan, Carl Zeiss Meditech, Dublin, CA, USA) and an Aviso imaging system (Ascan, Quantel Medical, France). More than ten axial length measurements were taken in each eye, and the mean value was calculated. The IOL power was biometrically calculated using the SRK-T formulae. All IOP measurements were obtained using Goldmann applanation tonometry, across different time-points during the daylight hours of 08:30 to 11:30 am. This was performed, in most cases, by a resident physician prior to observation of the patient by the treating physician. The IOP was re-measured by the treating physician where discrepancies in the results arose, in order to improve the accuracy of the measurement. All the combined surgeries were performed by one surgeon. A foldable IOL (TECNIS® ZCB00; Abbot Medical Optics, Abbott Park, IL, USA) was inserted into the capsular bag prior to the PPV. Before the cataract operation, a 3mm clear corneal incision was made at the 10:30 position. A continuous curvilinear capsulorhexis was created, and phacoemulsification and aspiration were performed. Standard 3-port vitrectomy was performed using a 23-gauge vitreous cutter and an endo-illuminator. The vitreous was removed and additional vitreoretinal procedures, including fluid-air or fluid-gas exchange and endophotocoagulation, were performed when required. A Student's t test, paired t test, or simple linear regression, was used to analyze the refractive outcomes and IOP. A P < 0.05 was considered to indicate a statistically significant difference. All the analyses were performed using SPSS version 12.0.0 for Windows (SPSS Inc., Chicago, IL, USA). Results Fifty-five eyes of 55 patients met the inclusion criteria for enrolment in the present study. Twenty-five of the 55 patients underwent combined surgery for RRD and thus were assigned to the RRD group. The remaining 30 patients were assigned to the control group. The mean age of the patients in the RRD group was 60.28 ± 12.56 years, of which nine were men and 16 were women. The mean age of the patients in the control group was 59.43 ± 11.00 years, of which 20 were men and 10 were women. There was no significant difference in the mean ages between the two groups (P = .791). However, the RRD group contained a significantly higher proportion of female patients (P = .032). The vitreoretinal pathologies of the control group were as follows: diabetic retinopathy (17 eyes, 56.6%); branch or central retinal vein occlusion (7 eyes, 23.3%); macular hole

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(2 eyes, 6.6%); epiretinal membrane (2 eyes, 6.6%); vitreous opacity due to previous uveitis (2 eyes, 6.6%). The mean preoperative refractive outcomes in the RRD and control groups were -2.11 ± 4.94 diopter (D) and -1.35 ± 2.37 D, respectively (P = .464, Student's t test). The mean axial lengths in the RRD group and the control group were 24.76 ± 2.08 mm and 24.42 ± 1.28 mm, respectively. There was no significant difference between the two groups (P = .459, Student's t test) (Table 1). The mean keratometric value was not significantly different between the pre-operative and post-operative measurements in both groups. The mean differences were -0.04 ± 0.36 D (P = .255, paired t-test) and 0.03 ± 0.33 D (P = .486, paired t-test), respectively (Table 2). The RRD group had a significantly greater myopic refractive surprise as compared with the control group. The mean prediction difference between the predicted and postoperative 6 month refractive outcomes in the RRD and control groups were 0.43 ± 0.67 D (P = .046, paired t-test) and -0.08 ± 0.53 D (P = .767, paired t-test) (Table 3). A mean of 0.35 D to the myopic side was comparable with the control group. There was a significant difference in the mean preoperative IOP in the affected eye, as compared with the corresponding unaffected eye in the patients of the RRD group (P = .045, Student's t test), with mean values of 11.44 ± 3.15 and 13.16 ± 2.73 mmHg, respectively. However, there was no significant difference in the mean pre-operative IOP between the affected eye and the unaffected eye (14.20 ± 2.95 and 14.17 ± 3.50 mmHg, respectively; P = .974, Student's t test) in patients of the control group. The mean postoperative 3 and 6 month IOP in the affected and unaffected eyes of the two groups showed little differences (Table 4) (Figure 1). For all the eyes in the RRD group, the refractive difference was correlated to the intraocular pressure change (r = .659, r2 = .435, P < .001, linear regression analysis) (Figure 2).

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Discussion Combined surgery is currently considered the standard procedure to correct vitreoretinal disease.6,7 Perfect refractive results, however, are not always achieved, especially in cases involving more complex retinal diseases.2,4,6,15 This study evaluated the overall refractive outcomes in patients with RRD and other retinal diseases following combined surgery, and the factors affecting the refractive outcomes were investigated. Data from this study identified that the RRD group showed a significant post operative myopic shift, whereas the values for the control group were within a tolerable range. There are numerous explanations for these data, which are explained in more detail. The key parameters for determining the lens power in patients undergoing cataract or combined surgery are the keratometric value and the axial length of the eye.16 In a previous study by Muallem et al., it was shown that keratometry readings can be affected by ocular surgery such as trabeculectomy.17 This study, however, showed that the combined surgery did not affect the keratometric readings. This is supported by the data presented by Jeoung et al.11 Of the variables used to calculate the IOL power, the axial length can change following combined surgery.11 In this retrospective observational case control study design, the postoperative axial lengths were not obtained in the two groups. Thus, direct comparison of the preoperative and postoperative axial lengths was difficult. Various factors of axial length change, however, could be considered. Zhang et al.12 proposed

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that a contact-type A-scan measurement caused a bias by inducing greater indentation in eyes with low pressure. In this study, the RRD group showed significantly low preoperative IOP, and the contact type A-scan was used to measure the pre-operative axial length in all the patients. For this reason, the possibility of an indentation bias cannot be fully excluded. Another important factor associated with axial length measurement is the intraocular pressure, which can cause lengthening of the globes, particularly in preoperative hypotonous eyes. Muallem et al.17 reported the differences between the predicted refraction and the refraction outcome in cataract surgery following trabeculectomy. In their study, the refractive outcome remained predictable; however, the lower prephacoemulsification intraocular pressure was weakly correlated with the myopic shift in the final refraction. Zhang et al.12 evaluated the effects of prior trabeculectomy on the refractive outcomes of cataract surgery. It was proposed that phacoemulsification following a trabeculectomy could increase the IOP, likely through postoperative intraocular inflammation, resulting in increased fibrosis of the trabeculectomy bleb. Furthermore, the refractive difference was correlated to the IOP change, since a 2mmHg rise in IOP resulted in a 0.36D myopic shift. In the present study, the refractive difference was also correlated to the IOP change, as the mean 1.7mmHg IOP rise resulted in a mean 0.43D myopic shift in the RRD group. The IOP and refractive difference was not significantly different in patients of the control group. This suggests that IOP normalization following combined surgery on patients with RRD with a preoperative low IOP can increase the axial length, which results in a myopic shift. Francis et al.13 examined the changes in the axial length following trabeculectomy and glaucoma drainage device surgery. An equation was derived that allowed the prediction of the axial length (AL) change following filtering surgery: AL reduction (mm)  =  −0.199 + 0.006 × IOP reduction + 0.008 × final IOP. Applying the data of the present study to this formula: -0.199 + 0.006 × (-1.7 mmHg) + 0.008 × (13.16 mmHg) = -0.104 mm. Therefore, according to the SRK formula, a 0.104mm AL reduction should induce a 0.26D myopic change.16,18,19 Although this result is lower than the final predicted difference, it can be proposed that this IOP mechanism may be key to understanding the phenomenon of myopic shift in RRD patients. Numerous studies have reported that combined surgery can produce a postoperative myopic shift effect. Suzuki et al.9 evaluated the effect of vitrectomy on postoperative refraction following simultaneous vitrectomy and cataract surgery. It was reported that the spread between the predicted refraction and the actual refraction was -0.05 ± 1.18 D in the combined surgery group and +0.55 ± 1.32 D in the cataract surgery group. This study suggested that vitrectomy can affect postoperative refraction, with a shift toward myopia when combined with cataract surgery. Shioya et al.8 reported that 36 eyes with a macular hole, in patients undergoing combined surgery, showed a shift toward myopia by an average of 0.50 D, compared with the eyes of patients in the cataract surgery group. It was concluded that a myopic shift following IOL implantation with vitrectomy is caused by (1) errors in the orbital axis length measurement due to the absence of the vitreous body; (2) a difference in the depth of the anterior chamber; and (3) a smaller refractive index of the vitreous body as compared with that of the aqueous humor. It was emphasized that among these three mechanisms, the second was the most likely cause

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for producing a myopic shift. This explanation was applicable to the cases assessed in the present study. The control group showed a tolerable range of refractive differences with a trend towards myopia. This may explain, in part, the significant myopic shift in patients of the RRD group, in addition to the IOP-related mechanism. In summary, the significant post-operative myopic shift in the RRD group is explained by (1) the corneal indentation bias of the hypotonous eye when it was examined preoperatively with the contact-type A-scan, (2) the normalization of the preoperative lowered IOP after combined surgery, which induced lengthening of the axial length, (3) and vitrectomy. Among these three mechanisms, we emphasized that the second mechanism might be the key to understanding this unproven phenomenon. We recommend that to calculate the IOL power in the macula on RRD patient with relatively low preoperative IOP eyes, the retinal surgeon should be thought carefully about the IOP effect because of the postoperative myopic shift. Moreover, if there is no significant spherical equivalent discrepancy between the two eyes, the axial length of the fellow eye maybe useful in calculating the exact intra-ocular lens power. This study has numerous limitations. First, the cases presented herein are relatively few. When comparing preoperative normal IOP macula on RRD patients and preoperative low IOP macula on RRD patients, it may be valuable to ensure a myopic shift related with IOP. This study, however, showed that only in the two patients who had a preoperative normal IOP macula on RRD’s postoperative spherical equivalent, each resulted in -1.0D and -1.25D within target range. In order to produce more accurate comparisons, a larger cohort size would have to be evaluated in future studies. However, one should look at this study from the viewpoint of its strict inclusion criteria of combined surgery, using only patients with macula on RRD. Secondly, corneal indentation bias with contact type axial length measurement cannot be excluded from this study. A non contact technique may be useful for measuring the axial length and eliminating corneal indentation bias in patients with RRD with hypotony. IOL calculation, using contact and non contact techniques, should be used to compare the expected refractive error by the different methods. This would be facilitated by knowing the effect of corneal indentation on the axial length. Furthermore, comparison of the pre- and postoperative axial lengths was not performed. In conclusion, this study offers a valuable insight in the initial concepts underlying a myopic shift related to IOP change in a combined surgical approach on patients with RRD. Direct comparison of the pre- and postoperative axial lengths with non-contact technique may clarify this issue, and analysis of the relationship of the actual axial length change with the IOP is required for further investigation. Acknowledgments / Disclosure All authors have completed and submitted the ICMJE form for disclosure of potential conflicts of interest and have no financial interest in the subject under discussion. This research was supported by a grant from Hallym University Medical Center Research Fund. (01-2012-21) Contributions of authors: design and conduct of the study (K.H.C., S.I.K.); collection of data (I.W.P., K.H.C., S.I.K); management, analysis, and interpretation of data (K.H.C., S.I.K.); preparation of the manuscript (K.H.C., S.I.K); critical revision of the article (I.W.P., S.I.K.); and review and approval of the manuscript (S.I.K.).

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Figure legends FIGURE 1. Intraocular pressure(IOP) change following combined phacoemulsification and pars plana vitrectomy in patients with rhegmatogenous retinal detachment(RRD) and other retinal diseases. The mean preoperative IOP between the affected and unaffected eye in the RRD group was significantly different. (P = 0.045)

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FIGURE 2. Intraocular pressure(IOP) change and refraction difference following combined phacoemulsification and pars plana vitrectomy in patients with rhegmatogenous retinal detachment(RRD). The diagonal line represents the correlation between the refraction difference and the IOP change in the RRD group. The correlation was calculated using the following equation: Y = -0.115X + 3.363, where Y = Refraction difference (postoperative refraction - expected refraction) and X = axial length (r = .659, r2=.435; P