MACULAR EDEMA AFTER CATARACT SURGERY IN EYES WITH PREOPERATIVE RETINAL VEIN OCCLUSION HAN JOO CHO, MD, HYUN JI HWANG, MD, HYOUNG SEOK KIM, MD, DONG WON LEE, MD, CHUL GU KIM, MD, BYOUNG YEOP KIM, MD, JONG WOO KIM, MD, PHD Purpose: To evaluate the incidence of pseudophakic macular edema (PME) in eyes with a history of retinal vein occlusion before cataract surgery and to identify any associated risk factors. Methods: The records of 21,332 eyes that underwent cataract surgery were retrospectively reviewed. Eyes that had retinal vein occlusion preoperatively with no evidence of macular pathology on optical coherence tomography at the time of surgery and no macular edema treatment at least 6 months before surgery were included. Eyes with diabetes or diabetic retinopathy, those with a history of previous intraocular surgery or with intraoperative complications, and those administered glaucoma and nonsteroidal antiinflammatory eye drops were excluded. Results: Pseudophakic macular edema developed in 31 (27.4%) of 113 eyes within 3 months of cataract surgery. Mean visual acuity for eyes with PME (0.48 logarithm of the minimum angle of resolution [logMAR; 20/60 Snellen equivalent]) at 3 months after surgery was significantly worse than that for eyes without PME (0.28 logMAR; 20/38, P = 0.020). However, there was no significant difference in the visual acuity between the 2 groups 6 months after the surgery. Taking into consideration various baseline factors, a history of previous treatment of macular edema was significantly associated with an increased risk of PME (odds ratio, 11.022; 95% confidence interval, 7.258–17.712; P = 0.009). A higher number of intravitreal injections used to treat macular edema also significantly increased the risk of PME (odds ratio, 1.902; 95% confidence interval, 1.032–4.227; P = 0.031). Conclusion: Pseudophakic macular edema frequently developed after phacoemulsification cataract surgery in patients with a history of retinal vein occlusion. The risk of PME further increased when the patient had undergone macular edema treatment and had a higher prevalence of intravitreal injection treatment. RETINA 38:1180–1186, 2018

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a lower incidence of PME in the order of 0.2% to 2.35%.2,5 Diabetes, hypertension, a history of retinal vein occlusion (RVO), uveitis or glaucoma, presence of a preexisting epiretinal membrane, and complicated cataract surgery are known risk factors for PME. 3,6 Use of phacoemulsification techniques in eyes with a history of RVO is not uncommon, given that RVO is the second most common cause of retinal vascular disease after diabetic retinopathy.7,8 Moreover, macular edema often develops directly from RVO itself, which could lead to significant loss of vision.9–11 However, little is known about the development of PME after cataract surgery in patients with RVO.

ataract is the most common cause of blindness globally, and cataract surgery is one of the most common surgical procedures performed worldwide.1 Pseudophakic macular edema (PME) is the most common postoperative complication and impairs vision.2,3 The reported incidence of PME ranges from 0.2% to 20%.4 However, more recent investigations of modern phacoemulsification cataract surgery have reported From the Department of Ophthalmology, Kim’s Eye Hospital, Myung-Gok Eye Research Institute, Konyang University College of Medicine, Seoul, South Korea. None of the authors has any financial/conflicting interests to disclose. Reprint requests: Han Joo Cho, MD, Kim’s Eye Hospital, 156, 4ga, Yeoungdeungpo-dong, Yeoungdeungpo-gu, Seoul 07301, South Korea; e-mail: [email protected]

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The purpose of this study was to evaluate the incidence of PME, as defined by optical coherence tomography (OCT), in eyes with a history of RVO before cataract surgery. In addition, factors associated with development of PME were investigated in patients undergoing cataract surgery.

Materials and Methods The study adhered to the tenets of the Declaration of Helsinki and was approved by the local ethics committee at Kim’s Eye Hospital, Konyang University College of Medicine (institutional review board approval number A-2016-028). We undertook a search and review of the electronic medical records for patients who underwent cataract surgery between January 2013 and January 2016. All patients whose electronic medical records included phacoemulsification were investigated. Patients diagnosed with or treated for RVO before cataract surgery were identified. All patients were examined and followed up at Kim’s Eye Hospital, Konyang University College of Medicine. The exclusion criteria were as follows: previous use of topical nonsteroidal antiinflammatory drugs (NSAIDs); a history of diabetes or presence of diabetic retinopathy; current use of glaucoma medication; intraoperative complications such as rupture of the posterior capsule; a history of vitrectomy or ocular surgery other than for cataract; the presence of macular edema at the time of surgery; and treatment of macular edema within the 6 months before surgery. Consistent with the standard of care for routine cataract surgery at our institution, all patients underwent preoperative biometry and examination, including macular OCT, by an ophthalmologist. After conventional phacoemulsification, routine postoperative topical steroid and antibiotic drops were tapered for 4 weeks. Each patient was routinely followed up at 1 day, 1 week, 1 month, and 3 months after surgery, and additional follow-up was undertaken at the physician’s discretion. If an assessment of the patient’s visual acuity after surgery failed to meet expectations, or visual acuity unexpectedly deteriorated during follow-up, various investigations were performed, including routine macular OCT. The presence of PME was defined by the confirmation of cystoid macular changes on OCT images within 3 months after surgery and recorded as a clinical finding in the electronic medical record. Only eyes confirmed by OCT to be free of maculopathy for at least 6 months before surgery were included. Fluorescein angiography (FA) was not routinely performed,

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but OCT was performed when development of PME was suspected during follow-up. Visual acuity was defined as the best uncorrected or corrected distance visual acuity score available at each follow-up assessment. A manifest refraction test was mandatory for all patients before and 1 week and 1 month after cataract surgery. If corrective lenses were necessary after cataract surgery, they were prescribed based on the manifest refraction at 1 month. Additional manifest refraction testing was performed according to the physician’s discretion. Visual acuity was measured with the Snellen chart, and the value was converted to the logarithm of the minimum angle of resolution (logMAR) for statistical analysis. Patient data collected for all eyes included the following: age, sex, history of antihypertensive medication, axial length, visual acuity scores, RVO subtype, RVO findings on FA, a history of laser treatment for RVO, duration of RVO before cataract surgery, treatment of macular edema due to RVO before cataract surgery, and previous treatment modalities used for macular edema. The incidence of PME was analyzed, and various data, including for visual

Fig. 1. Flowchart showing how the population was filtered and included for analysis. The numbers indicate eyes in each group. Finally, 113 eyes with a history of RVO and macula had no other pathology before cataract surgery and were enrolled for analysis. IOL, intraocular lens; PC, posterior capsule.

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outcome, were compared between the eyes with and without PME. Risk factors for development of PME were also identified.



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likelihood ratio statistic based on maximum partial likelihood estimates for the covariate were used for selection of variables. All tests were two sided, and a P value less than 0.05 was considered statistically significant.

Statistical Analysis SPSS version 13.0 software (SPSS Inc, Chicago, IL) was used for all statistical analyses. Frequencies were compared between groups using the chi-square test. The analysis of changes in continuous variables was performed using either the paired or the unpaired t test. Multivariate logistic regression was performed to identify risk factors for PME after surgery. Forward and backward stepwise regressions were performed using the likelihood ratio model, in which changes in the

Results Baseline Characteristics An initial dataset was collected for the 21,332 eyes that underwent cataract surgery at our institution during the study period. Filtering of electronic medical record data showed that 228 of these eyes had a history of RVO; of these, 91 were excluded for the following patient-related reasons: history of diabetes or diabetic

Table 1. Baseline Characteristics of Patients Who Underwent Phacoemulsification With Preoperative Retinal Vein Occlusion

Age, years Sex, n (%) Male Female HTN medication, n (%) Axial length, mm Preoperative baseline visual acuity (logMAR [Snellen equivalent]) Preoperative visual acuity (logMAR), n (%) ,0.40 (20/40) 0.40 (20/40) to 1.0 (20/200) .1.0 (20/200) RVO subtype, n (%) BRVO* CRVO FA findings for RVO, n (%)† Perfused Ischemic Preoperative laser treatment, n (%) Mean of RVO duration before cataract surgery, months Previous macular edema treatment history before cataract surgery, n (%) Mean Injection numbers for macular edema treatment before cataract surgery‡ Previous macular edema treatment modalities, n (%)‡ Anti-VEGF (bevacizumab) Steroid (triamcinolone or dexamethasone implant) Anti-VEGF and steroid

Total (n = 113)

Eyes Without PME (n = 82)

Eyes With PME (n = 31)

P

67.2 ± 7.7

65.7 ± 7.4

69.7 ± 8.2

0.231

55 (48.7) 58 (51.3) 80 (70.8) 23.31 ± 0.7 0.58 ± 0.41 (20/76)

39 (47.6) 43 (52.4) 59 (72.0) 23.29 ± 0.5 0.57 ± 0.43 (20/74)

16 (51.6) 15 (48.4) 21 (67.8) 23.71 ± 0.9 0.61 ± 0.48 (20/81)

0.701

24 (21.3) 64 (56.6) 25 (22.1)

17 (20.7) 46 (56.1) 19 (23.2)

7 (22.6) 18 (58.1) 6 (19.3)

94 (83.2) 19 (16.8)

71/94 (75.5) 11/19 (57.9)

23/94 (24.5) 8/19 (42.1)

51 (64.5) 28 (35.5) 41 (36.3) 26.4 ± 12.2

38 (65.5) 20 (34.5) 32 (39.0) 27.6 ± 13.2

13 (61.9) 8 (38.1) 9 (29.0) 25.8 ± 14.2

0.324 0.766

65 (57.5)

42 (51.2)

23 (74.2)

0.027

3.58 ± 2.2

2.06 ± 1.2

4.84 ± 2.3

0.002

0.661 0.432 0.284

0.905 0.116 0.767

0.980 35 (53.8) 19 (29.2)

23 (54.8) 12 (28.6)

12 (52.2) 7 (30.4)

11 (17.0)

7 (16.6)

4 (17.4)

*Hemi-CRVO was defined as BRVO. †Fluorescein angiography was available for 79 eyes (69.9%) among all included eyes. More than 5 disk areas of nonperfusion on the FA image was defined as nonperfused in BRVO cases, and 10 disk areas of nonperfusion were required to be defined as nonperfused in cases with CRVO. ‡Data of 65 eyes (57.5%) that underwent intravitreal injection treatment of macular edema associated with previous RVO. HTN, hypertension; logMAR, logarithm of the minimum angle of resolution; VEGF, vascular endothelial growth factor.

PSEUDOPHAKIC MACULAR EDEMA AND RVO  CHO ET AL

retinopathy (61 eyes), use of topical NSAIDs (9 eyes), use of glaucoma medication (11 eyes), other intraocular surgical history including vitrectomy (8 eyes), and intraoperative complications including tear of the posterior capsule (2 eyes). A further 24 eyes were excluded when macula edema was found to have been present at the time of cataract surgery or the patient had a history of treatment for macular edema in the 6 months before surgery. Finally, 113 eyes with a history of RVO but without pathologic features in the macula before cataract surgery were enrolled for analysis. The process used to filter the patients is summarized in Figure 1. All patients were South Korean, and the mean age of the study group was 67.2 ± 7.7 years. The patients’ clinical details are listed in Table 1. Development of Pseudophakic Macular Edema Pseudophakic macular edema developed in 31 (27.4%) of the 113 enrolled eyes. Ten eyes (32.2%) developed PME within the first month after surgery, 13 eyes (41.9%) between the first and second months, and 8 eyes (25.9%) between the second and third months. At baseline, there were no significant differences between the eyes without (n = 82) and with (n = 31) PME regarding age, sex, history of antihypertensive medication, axial length, preoperative visual acuity score, RVO subtype, FA finding of RVO, history of preoperative laser treatment, or duration of RVO.

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However, the eyes with PME had a more significant history of previous treatment for macular edema than the eyes without PME (P = 0.027; Table 1). In addition, the mean number of intravitreal injections for previous macular edema was significantly greater in eyes with PME than in those without PME (P = 0.002; Table 1). The distribution of treatment modalities for previous macular edema did not show any statistically significant difference between the groups (Table 1). Visual Outcomes Comparing eyes with and without PME, the mean visual acuity score in both groups improved significantly between baseline and postoperative follow-up assessments at 1, 3, and 6 months (Figure 2). Mean visual acuity was significantly worse in the eyes with PME than in those without PME at 1 week, 1 month, and 3 months after surgery (P = 0.031, P = 0.012, and P = 0.020, respectively, Figure 2). However, there was no significant difference in visual acuity between the groups at 6 months after cataract surgery; by this time, 78% of the enrolled eyes had a visual acuity score of 20/40 or better for both eyes, 81% of eyes without PME had a score of 20/40 or better, and 71% of eyes with PME had a score of 20/40 or better. There was no significant difference in the proportions of eyes with a visual acuity of better than 20/40.

Fig. 2. Changes in mean visual acuity, expressed as the logarithm of the minimal angle of resolution (logMAR), during 6 months of follow-up in patients with a history of retinal vein occlusion before cataract surgery. The mean visual acuity in eyes with pseudophakic macular edema (PME) was significantly worse until 3 months after surgery than in eyes without pseudophakic macular edema. However, there was no significant difference in visual acuity of eyes after 6 months from the date of surgery between the groups.

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Every eye that developed PME received additional treatment. The treatment modality was selected at the physician’s discretion for each case. For patients with a history of macular edema who were treated with intravitreal injections before cataract surgery (23 eyes), the same drug as the initial treatment was injected for macular edema after cataract surgery; 12 eyes were treated with anti–vascular endothelial growth factor injection, 7 eyes were treated with intravitreal triamcinolone injection, and 4 eyes were treated with a combination of anti–vascular endothelial growth factor and triamcinolone injections. Among the eight eyes with PME without a history of macular edema, four eyes were initially treated with topical NSAIDs and four eyes were treated with intravitreal triamcinolone or anti–vascular endothelial growth factor injections. Twenty-four eyes (77.4%) showed resolution of PME after one session of treatment. However, 5 eyes (16.1%) needed 2 sessions of treatment for the resolution of macular edema, and 2 eyes (6.5%) demonstrated persistent macular edema at 6 months after cataract surgery, despite undergoing more than 2 sessions of treatment. Predictors of Pseudophakic Macular Edema and Baseline Characteristics Among the various preselected baseline characteristics, multivariate logistic regression showed that a history of treatment for macular edema was significantly associated with an increased risk of developing PME (odds ratio: 11.022, 95% confidence interval: 7.258–17.712, P = 0.009). An increase in the cumulative number of previous intravitreal injections for macular edema also significantly increased the risk of PME



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(odds ratio: 1.902, 95% confidence interval: 1.032– 4.227, P = 0.031). However, no significant association was found between development of PME and other factors, including the baseline visual acuity score, RVO subtype, RVO findings on FA, preoperative laser treatment, and duration of RVO (Table 2). Discussion In this study of a patient cohort with a history of RVO, the incidence of PME was 27.4% (31 of 113 eyes), and it increased to 35.4% (23 of 65 eyes) in patients with a history of treatment for macular edema associated with RVO before cataract surgery. Recent literature reports that the incidence of PME associated with modern phacoemulsification techniques is between 0.2% and 2.35%.2,5 Although direct comparisons with other studies could not be made, our result revealed a higher incidence of PME compared with that in previous reports. Pseudophakic macular edema is thought to be caused by increased vascular permeability induced by inflammatory mediators, including prostaglandins.2 Modern phacoemulsification techniques may trigger release of arachidonic acid from cell membranes, leading to production of either leukotrienes through the lipoxygenase pathway or prostaglandins through the cyclooxygenase pathway.12 It has also been reported that inflammation may cause an increase in vascular permeability through release of inflammatory factors in patients with branch retinal vein occlusion (BRVO).13 Moreover, abnormalities in the capillary network, including disruption or dilation in both the superficial and deep capillary plexus, were reported to be common in patients with RVO.14 These findings

Table 2. Logistic Regression Analysis Using Macular Edema Development After Phacoemulsification for Patients With a History of Retinal Vein Occlusion as the Dependent Variable Univariate Analysis Variable Age Sex HTN medication Preoperative baseline visual acuity (logMAR) RVO subtype (BRVO or CRVO) FA finding (perfused or ischemic) Preoperative laser treatment (yes or no) Duration from initial diagnosis of RVO Previous macular edema treatment (yes or no) No. of previous intravitreal injections for macular edema treatment

OR (95% CI)

Multivariate Analysis P

OR (95% CI)

P

0.940 0.898 1.489 0.364

(0.881–1.016) (0.778–1.112) (0.669–3.452) (0.171–1.141)

0.128 0.333 0.427 0.486

0.834 3.224 1.471 1.003 13.112

(0.771–1.345) (0.938–6.662) (1.009–2.202) (0.982–1.066) (5.227–24.452)

0.352 0.119 0.238 0.762 0.006

11.022 (7.258–17.712)

0.009

0.021

1.902 (1.032–4.227)

0.031

2.573 (1.103–4.002)

CI, confidence interval; HTN, hypertension; logMAR, logarithm of the minimum angle of resolution; OR, odds ratio.

PSEUDOPHAKIC MACULAR EDEMA AND RVO  CHO ET AL

suggest that the blood–retinal barrier is dysfunctional in patients with RVO. Thus, patients with RVO could be more prone to development of macular edema because of inflammation after cataract surgery when compared with their counterparts without RVO. The results of this study indicate that a history of treatment for macular edema before cataract surgery is a significant risk factor for PME. We also found that the risk of developing PME after surgery increased with increasing numbers of intravitreal injections given for macular edema before surgery. In the 34 eyes that received more than three such injections, the incidence of PME reached 61.8% (21 of 34 eyes), despite stable OCT findings for the macula at least 6 months before cataract surgery. Therefore, clinicians should be mindful of a history of RVO when considering patients for cataract surgery and attempt to minimize the risk of postoperative PME. A patient with a history of treatment for macular edema warrants particular attention in this regard. Clinicians could consider the use of prophylactic agents such as NSAIDs15–17 to address the risk of PME in patients with RVO. However, the prophylactic effect of NSAIDs on PME in eyes with a history of RVO has never been evaluated. The effect of NSAIDs on eyes with a history of RVO should be evaluated in future studies. Other baseline factors for consideration includes the RVO subtype, such as BRVO or central retinal vein occlusion (CRVO), FA findings (perfused or ischemic), and duration of RVO, which did not appear to be risk factors for PME in our study. It has been reported that macular edema tends to develop more frequently and have a more refractory presentation in patients with CRVO than in those with BRVO.18 In this study, the incidence of PME was marginally higher in the patients with CRVO (42.1%) than in the patients with BRVO (27.4%). Our hypothesis that the characteristics of RVO influence the development of PME is not supported by our finding that the difference between BRVO and CRVO regarding the development of macular edema was not statistically significant. These results may be accounted for owing to the higher exclusion rate of patients with CRVO, who had compromised maculae resultant from a higher frequency of preoperative macular edema 6 months before surgery, than that of patients with BRVO. Not surprisingly, improvements in visual acuity after cataract surgery were noted in most patients in our study. Overall, 78% of the eyes that developed PME had a visual acuity score of 20/40 or better and 71% had a score of 20/40 or better. The mean visual acuity of eyes with PME was significantly worse than in eyes without PME in the 3 months after surgery, but

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there was no significant difference between these groups at 6 months after surgery, which could be due to the natural history of PME and/or treatmentinduced resolution of the condition. It has been reported that PME is self-limiting in many cases, and that visual morbidity is relatively low.3,19 Our results are consistent with previous reports regarding visual outcomes, despite our higher incidence of eyes with RVO. However, PME is a potential public health care burden because patients with a history of treatment for macular edema are more likely to require additional treatment for PME in the future. For instance, one investigation in the USA reported that the cost associated with cases involving PME was 41% higher than in cases not involving PME.20 In this study, all patients underwent additional treatment for PME, including use of NSAIDs, intravitreal anti–vascular endothelial growth factor, triamcinolone, dexamethasone implant injection, or a combination of these treatments. The efficacy of treatment for PME in association with a history of RVO was not considered in this study because the treatment modality was selected without any established criteria and according to the discretion of each attending physician. The difference in the clinical course or treatment response between such patients and those with PME without RVO could be investigated in future. To the best of our knowledge, this study represents the largest published series of patients with RVO who have undergone cataract surgery. However, the retrospective design is a major limitation of our study. Another limitation is the potentially speculative definition of PME. Although we only included patients confirmed to have no macular lesions in the 6 months before surgery, we could not definitively differentiate between pure PME and recurrent macular edema caused by RVO. This was because macular edema frequently develops as a direct result of RVO.9–11 However, it is impossible to completely differentiate pure PME from macular edema associated with RVO, particularly during the acute phase after surgery. Although FA was performed routinely for each case, “Irvine-Gass syndrome” could not be differentiated in cases with minimal cystoid macular edema or in patients with previous macular edema associated with RVO. In addition, there is a possibility that the macular edema after cataract surgery in patients with a history of RVO was a result of the combination of the mechanisms of pure PME and macular edema secondary to RVO. Therefore, the incidence of macular edema within the 90-day window period after cataract surgery can be broadly called as PME, in line with the previous literature.3,6,21,22 Second, OCT images were

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not routinely taken after surgery in all patients, and there is the possibility that asymptomatic PME was not included in the analysis. As a result, we only investigated our study patients for clinically significant macular edema. Nonetheless, our study shows a relatively higher incidence of PME in association with RVO, despite the possibility that PME was underrepresented in the sample population. In summary, we found that PME frequently developed in patients with a history of RVO. The risk of PME increased in patients with a history of treatment for macular edema. This risk increased even further with increasing frequency of preoperative treatment for macular edema. These findings should allow clinicians to counsel patients with RVO more accurately regarding the risk of PME and its consequences when undergoing cataract surgery. Key words: cataract surgery, macular edema, phacoemulsification, retinal vein occlusion. References 1. Pascolini D, Mariotti SP. Global estimates of visual impairment: 2010. Br J Ophthalmol 2012;96:614–618. 2. Yonekawa Y, Kim IK. Pseudophakic cystoid macular edema. Curr Opin Ophthalmol 2012;23:26–32. 3. Guo S, Patel S, Baumrind B, et al. Management of pseudophakic cystoid macular edema. Surv Ophthalmol 2015;60:123–137. 4. Flach AJ. The incidence, pathogenesis and treatment of cystoid macular edema following cataract surgery. Trans Am Ophthalmol Soc 1998;96:557–634. 5. Lobo C. Pseudophakic cystoid macular edema. Ophthalmologica 2012;227:61–67. 6. Chu CJ, Johnston RL, Buscombe C, et al. Risk factors and incidence of macular edema after cataract surgery: a database study of 81984 eyes. Ophthalmology 2016;123:316–323. 7. Jaulim A, Ahmed B, Khanam T, Chatziralli IP. Branch retinal vein occlusion: epidemiology, pathogenesis, risk factors, clinical features, diagnosis, and complications. An update of the literature. Retina 2013;33:901–910. 8. Rogers S, McIntosh RL, Cheung N, et al. The prevalence of retinal vein occlusion: pooled data from population studies from the United States, Europe, Asia, and Australia. Ophthalmology 2010;117:313–319. e311.



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9. Natural history and clinical management of central retinal vein occlusion. The Central Vein Occlusion Study Group. Arch Ophthalmol 1997;115:486–491. 10. Evaluation of grid pattern photocoagulation for macular edema in central vein occlusion. The Central Vein Occlusion Study Group M report. Ophthalmology 1995;102:1425–1433. 11. Ho M, Liu DT, Lam DS, Jonas JB. Retinal vein occlusions, from basics to the latest treatment. Retina 2016;36:432–448. 12. Conway MD, Canakis C, Livir-Rallatos C, Peyman GA. Intravitreal triamcinolone acetonide for refractory chronic pseudophakic cystoid macular edema. J Cataract Refract Surg 2003; 29:27–33. 13. Noma H, Mimura T, Shimada K. Role of inflammation in previously untreated macular edema with branch retinal vein occlusion. BMC Ophthalmol 2014;14:67. 14. Coscas F, Glacet-Bernard A, Miere A, et al. Optical coherence tomography angiography in retinal vein occlusion: evaluation of superficial and deep capillary Plexa. Am J Ophthalmol 2016;161:160–171. e161–e162. 15. Wolf EJ, Braunstein A, Shih C, Braunstein RE. Incidence of visually significant pseudophakic macular edema after uneventful phacoemulsification in patients treated with nepafenac. J Cataract Refract Surg 2007;33:1546–1549. 16. Tzelikis PF, Vieira M, Hida WT, et al. Comparison of ketorolac 0.4% and nepafenac 0.1% for the prevention of cystoid macular oedema after phacoemulsification: prospective placebo-controlled randomised study. Br J Ophthalmol 2015; 99:654–658. 17. Mathys KC, Cohen KL. Impact of nepafenac 0.1% on macular thickness and postoperative visual acuity after cataract surgery in patients at low risk for cystoid macular oedema. Eye (Lond) 2010;24:90–96. 18. Hayreh SS. Ocular vascular occlusive disorders: natural history of visual outcome. Prog Retin Eye Res 2014;41:1–25. 19. Bradford JD, Wilkinson CP, Bradford RH. Cystoid macular edema following extracapsular cataract extraction and posterior chamber intraocular lens implantation. Retina 1988;8: 161–164. 20. Schmier JK, Halpern MT, Covert DW, Matthews GP. Evaluation of costs for cystoid macular edema among patients after cataract surgery. Retina 2007;27:621–628. 21. Baker CW, Almukhtar T, Bressler NM, et al. Macular edema after cataract surgery in eyes without preoperative centralinvolved diabetic macular edema. JAMA Ophthalmol 2013; 131:870–879. 22. Kessel L, Tendal B, Jørgensen KJ, et al. Post-cataract prevention of inflammation and macular edema by steroid and nonsteroidal anti-inflammatory eye drops: a systematic review. Ophthalmology 2014;121:1915–1924.