Immediate sequential bilateral cataract surgery (ISBCS) remains a hotly debated topic among cataract surgeons worldwide. Many cite patient satisfaction and the associated macroeconomic savings as reasons to conduct surgery on both eyes at the same time. Recent studies, including large randomized controlled trials, have highlighted the safety and similar outcomes of ISBCS compared to delayed sequential bilateral cataract surgery (DSBCS), the more common standard. Still, concerns around the potential for devastating complications such as bilateral post-operative endophthalmitis have limited the utilization of ISBCS. Moreover, financial implications for surgeons, primarily reduced reimbursement, further disincentivize ISBCS. As health care and practice patterns evolve, ISBCS may become more common in countries such as the United States of America.
Key points
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Immediate sequential bilateral cataract surgery (ISBCS) is not the standard of practice in America, but in certain locations around the world, it is very common practice.
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The primary concerns for ISBCS surround the potential risk of bilateral postoperative endophthalmitis, which seems to have a low risk, but cases continue to be reported.
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Research supports no significant differences in refractive or surgical outcomes in patients who undergo ISBCS compared with delayed sequential bilateral cataract surgery (DSBCS).
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Beyond concerns around risk, there exist financial and economic barriers to increased utilization of ISBCS by surgeons.
Introduction
Cataract surgery is the most commonly performed surgery in the United States and is generally considered to be an elective surgery [ ]. For many patients, cataract surgery is conducted sequentially in both eyes, as the conditions leading to cataract development are often age-related and symmetric. In the US and most countries around the world, the 2 surgeries are usually completed on different days, otherwise described as delayed sequential bilateral cataract surgery (DSBCS). An alternative to this model is performing surgeries in the 2 eyes on the same day, termed immediate sequential bilateral cataract surgery (ISBCS). ISBCS was first reported in 1952 [ ], and while it accounts for a minority of cases in the US, it is used in many countries around the world at varying rates.
In the US, ISBCS accounts for a minority of cataract surgeries. In a large database study of Medicare patients receiving bilateral cataract surgery from 2011 to 2019, only a total of 4014 (0.2%) of the nearly 2 million patients included underwent ISBCS [ ]. At Kaiser Permanente Northern California, however, greater than 21% of patients undergoing bilateral cataract surgery from 2013 to 2015 received ISCBS [ ]. Outside of the US, countries including Canada, Sweden, Finland, and the Spanish Canary Islands are known for the more common use of ISBCS [ ]. In a cross-sectional study of patients from a single institution in Finland, the proportion of patients undergoing ISBCS increased from 4.2% in 2008 to 46% in 2020 [ ].
In recent decades, the concept of ISBCS has been under debate. Supporters cite improved efficiency and costs, patient satisfaction, and a noninferior safety profile [ ]. Detractors primarily cite the possibility of profound bilateral vision loss through complications such as bilateral postoperative endophthalmitis, in addition to issues with refractive surprise, reduced reimbursement, and possible legal and malpractice concerns [ ].
Perceptions
Patient perspectives
Multiple studies have examined ISBCS from the perspective of patients [ ]. In the largest of these studies, Carolan and colleagues surveyed 3636 patients who underwent either ISBCS or DSBCS. In this study, a greater percentage of patients with ISBCS stated they would choose to have their procedure again compared with DSBCS (96% vs 80%, P < .001). Similarly, a larger percentage of patients with ISBCS would recommend the procedure they had to a friend or family member (94% vs 68%, P < .001) [ ]. Other survey-based studies found similarly high levels of respondents who would choose ISBCS again or recommend it to a friend or family member [ , , ].
Carolan and colleagues also examined factors that contributed to patients choice of ISBCS versus DSBCS. Many patients (65%) cited the improved convenience of ISBCS. On the other hand, 68% of those receiving DSBCS, not ISBCS, reported surgeon recommendation as the predominant factor [ ]. Obuchowska and colleagues reported that the most commonly reported benefits were only one operation stay (82.6%), a reduced number of clinic visits (62.6%), and quicker normalization of eyesight (61%); they also noted that the most commonly reported postoperative nuisance was having to sleep in a supine position (32.8%) [ ]. In their analysis, they found differing perspectives from patients based on their age, whereby older respondents most preferred the reduced number of clinic visits and operation dates, while younger patients cited the quicker normalization of vision more frequently [ ].
Provider perspectives
Surgeon perspectives on ISBCS are perhaps the most crucial facilitating factor or impediment to increased utilization. While surgeons in the United States do not broadly practice ISBCS [ ], numerous studies have examined surgeon perspectives in specific locations whereby it is commonly practiced. At Kaiser Permanente in Northern California, whereby 86% of cataract surgeons were currently performing ISBCS, the primary reasons for performing were patient convenience (95%) and patient request (91%) [ ]. In the United Kingdom, whereby fewer surgeons were performing ISBCS (13.9%), saving patient time was most commonly cited as the reason why surgeons would consider it [ ].
On the other hand, similar themes emerged as barriers to increased adoption. In the sample of surgeons at Kaiser Permanente, the most commonly cited reason for not performing ISBCS was a concern for suboptimal refractive outcome and the inability to adjust IOL for the second eye based on the first eye’s postoperative refraction [ ]. In the subset of surgeons from the UK, 92.6% of surgeons not performing ISBCS cited fear of bilateral endophthalmitis [ ]. Other frequently cited factors included medicolegal concerns and reduced reimbursement [ , ]. Despite these concerns, some surgeons who did not generally offer ISBCS reported that they would consider it for patients with senile cataracts undergoing high-risk general anesthesia [ ].
Selection criteria
A key consideration for ISBCS is patient selection. Not all patients are good candidates for ISBCS, and certain factors may lead to a higher risk of negative outcomes. The most recent large randomized controlled trial utilized a relatively extensive set of exclusion factors for surgery [ ]. Important exclusion factors included nonroutine cataract surgery or combined cataract surgery with other intraocular surgery (ie, glaucoma surgeries), cognitive conditions that might interfere with surgery, the use of premium IOLs, a higher risk of endophthalmitis (active blepharitis, immunocompromised state, iodine allergy), corneal endothelial dysfunction, glaucoma, uveitis, diabetic macular edema, other sight-threatening comorbidity, factors that increase the likelihood of refractive surprise, and factors that increase the likelihood of complicated surgery. The included risk factors for poor refractive outcomes were abnormal axial length (<21 mm, > 27 mm, or >1.5 mm difference between eyes), abnormal keratometry readings, previous refractive surgery, and myopia with posterior staphyloma. Conditions associated with a higher risk of complicated surgery included previous ocular surgery, prior open globe injury, anatomic abnormalities such as pseudoexfoliation syndrome, lens subluxation or iridodonesis, and posterior polar cataracts [ ]. Others have used similar lists of exclusion factors, though the specifics may be slightly different; for example, Sandhu and colleagues used axial length cutoffs of greater than 26 mm and differences in axial length of more than 1 mm [ ]. Others have had less stringent restrictions [ , ], including a recent retrospective study, in which authors noted that despite including a wider range of patients with preexisting ocular comorbidities, there were no increased rates of complications when allowing for surgeon discretion [ ]. Table 1 summarizes a common set of factors used to exclude patients from ISBCS.
| Considerations | Exclusion factors |
|---|---|
| Surgical Planning |
|
| Patient Considerations |
|
| Increased risk of infection |
|
| Increased risk of intraoperative or post-operative complications |
|
| Refractive considerations |
|
Safety
Safety concerns, the most notable of which is the development of bilateral postoperative endophthalmitis, are perhaps the greatest impediment to increased utilization of ISBCS [ ]. A 2022 review by Chen and colleagues reported 9 cases of bilateral postoperative endophthalmitis more than the prior 50 years [ ]. An additional case was reported by Friling and colleagues the same year [ ], and another in 2023 [ ]. According to prior work by Arshinoff and colleagues, the 4 earlier of these cases did not adhere to current recommendations of completely segregating the 2 eyes to ensure sterility [ ]. In 2023, a retrospective case series discussed an outbreak of bilateral postoperative endophthalmitis following ISBCS in Denmark [ ]. Three cases were reported, and the same strain of cefuroxime-resistant S. epidermidis was identified in 4 of the 5 vitrectomized eyes. While the specific cause of the outbreak was not clear, the authors suggested a systemic breach of sterility.
Others have worked to identify the prevalence of bilateral postoperative endophthalmitis and compare it to DSBCS. Two recent large registry studies, Lacy and colleagues [ ] in the United States and Friling and colleagues [ ] in Sweden, reported the incidence of postoperative endophthalmitis in ISBCS and DSBCS across a number of years. Lacy and colleagues used the Intelligence Research in Sight (IRIS) registry with more than 5.5 million patients from 2013 to 2018, comparing incidence rates for 165,609 patients who underwent ISBCS to 3,965,440 patients with DSBCS [ ]. After excluding cases of endophthalmitis without supported clinical findings, similar rates of endophthalmitis occurred between surgery groups (0.059% in the ISBCS group vs 0.056% in the DSBCS or unilateral group; P =.53) and there were no cases of bilateral postoperative endophthalmitis. Of note, 4 patients in the ISBCS group were initially coded as having bilateral endophthalmitis, but none had supportive clinic findings. A similar analysis was conducted by Friling and colleagues using the Swedish National Cataract Registry (NCR) from 2002 to 2017 [ ]. In this study of 1,457,172 surgeries, including 92,238 ISBCS, there was a statistically significantly lower incidence of postoperative endophthalmitis in the ISBCS group (0.0152%) than the unilateral surgery group (0.0299%). Importantly, however, there was one noted case of bilateral endophthalmitis in the ISBCS group, or 0.002% of patients [ ].
Many others have examined ISBCS in both prospective and retrospective studies to determine levels of safety and efficacy. Herrinton and colleagues examined a total of 15,850 surgeries at Kaiser Permanente Northern California, finding no cases of bilateral endophthalmitis in more than 3000 patients [ ]. Hujanen and colleagues examined 13,445 patients with ISBCS and found zero cases of bilateral postoperative endophthalmitis [ ]. A 2023 meta-analysis also found no increased risk of bilateral endophthalmitis with ISBCS [ ]. Other smaller studies also found no cases of bilateral endophthalmitis [ , ].
While bilateral postoperative endophthalmitis is the most severe potential complication of ISBCS, other relevant potential complications include the development of bilateral toxic anterior segment syndrome (TASS), the implantation of wrong intraocular lenses (IOLs), and the simultaneous development of other postoperative complications (eg, cystoid macular edema or retinal detachment). The risk of bilateral TASS is felt to be negligible [ ] following ISBCS, and none of the above-referenced studies noted a statistically significant increase in other postoperative complications when comparing ISBCS to DSBCS.
Other complication rates are also felt to be generally similar between ISBCS and DSBCS, including postoperative cystoid macular edema and corneal edema [ ]. In the aforementioned 2023 meta-analysis, however, a slightly higher rate of posterior capsular rupture was noted in the ISBCS group (relative risk 1.34, P =.0078). Of note, when only including randomized controlled trials, no statistically significant difference occurred [ ].
Investigators have published work to protocolize ISBCS to reduce the risk of feared complications. A study from Kaiser Permanente used “Failure Modes and Effects” analysis to examine ways to reduce the risk of endophthalmitis, TASS, and the use of incorrect IOLs [ ]. They highlighted issues with instrument processing and pharmaceutical procurement, in addition to post-operative issues such as inadequate patient hand hygiene and delayed triage of postoperative patients with concerning symptoms as possible contributing factors to increased risk of bilateral endophthalmitis and TASS. Furthermore, they addressed the possibility of wrong IOL implantation, which might be elevated in the case of ISBCS, by developing a list of double checks and documentation to reduce such errors [ ]. Others have highlighted proper protocols and selection criteria to prevent adverse events [ , , ].
Overall, there is somewhat mixed evidence regarding the potential for increased adverse events associated with ISBCS. While cases of bilateral postoperative endophthalmitis have occurred after ISBCS, the incidence appears to be very low and maybe even lower than previously felt with current surgical techniques and guidelines. Still, these situations do occur, even with current practice, and surgeons should exercise caution when considering this potentially devastating risk.
Outcomes
A variety of randomized controlled trials have examined the outcomes of ISBCS, all of which have concluded ISBCS to be noninferior to DSBCS [ , ]. The largest and most recent, set in the Netherlands from 2018 to 2020, compared ISBCS to DSBCS with a time period of 2 weeks between surgeries. At 4 weeks postoperation, they reported similar rates of patients with refraction less than 1.0D (97% for ISBCS, 98% for DSBCS, P =.526) and 0.5D (79% for ISBCS, 77% for DSBCS, P =.470) from their target refractive outcome. They also found similar rates of patients with uncorrected and best-corrected visual acuity better than 0.1 logMAR [ ]. Sarikkola and colleagues, who studied patients in Finland from 2002 to 2005, found no significant differences in patients with postoperative refractions within 2D, 1D, or 0.5D from the refractive target [ ]. None of the trials found any statistically significant improvement in best corrected visual acuity (BCVA) or uncorrected visual acuity (UCVA) for the DSBCS groups [ , ]. Furthermore, prospective and retrospective studies also reported similar outcomes between ISBCS and DSBCS [ , ]. A 2023 meta-analysis also identified no statistically significant difference in refractive outcomes, both with pooling randomized controlled trials and separately when including nonrandomized studies [ ].
Supporters of ISBCS often cite improved patient visual function, particularly in the early postoperative period, as a reason to use ISBCS. In addition to generally very positive patient satisfaction alluded to earlier, patient reported outcomes in the context of ISBCS and DSBCS have been studied. The protocol for DSBCS used by Spekreijse and colleagues was perhaps the closest to modern practice, with only a 2-week delay between sequential surgeries. In their analysis, they did not report a significant difference between groups for both the NEI-VFQ-25 composite score ( P =.20) and the Catquest-9SF Rasch score ( P =.77). They did, however, report that 2% of patients in the DSBCS group experienced “disturbing anisometropia.” [ ]. Some of the earlier trials, which had longer intervals between first and second eye surgeries, highlighted improved patient reported outcomes in the ISBCS group compared with the DSBCS before the second eye surgery was completed, though these normalized after the second eye surgery [ , ]. While it is true that patients with ISBCS may have short-lived superior visual function compared with DSBCS, the transient nature of this and the ability of most health systems to allow for short intervals between surgeries limits the utility of this advantage. Instead, ISBCS and DSBCS are felt to offer similar levels of improvement in visual function.
On the other hand, the concern for a refractive surprise in the first eye, and the resulting ability to adjust IOL power for a second surgery, is a commonly cited concern for suboptimal outcomes with ISBCS. In one study using the IRIS registry, researchers found a modest improvement in uncorrected distance visual acuity (UDVA) for patients who underwent DSBCS (within 14 days) compared with ISBCS. Of the ISBCS first eyes, 21.2% had UDVA of 20/20, which was 2.2% less than DSBCS eyes (23.4%); for the second eyes, 21.0% of ISBCS eyes were 20/20 compared with 24.2% for DSBCS eyes, or 3.2% less than DSBCS. While the data was retrospective and not controlled, the authors hypothesized that this incremental 1.0% of 20/20 second eyes may be a result of the surgeon’s ability to update IOL choice based on the refraction of the first eye [ ]. Sarikkola and colleagues noted that the IOL was changed in 4.7% of patients with DSBCS, but also found no difference between the target and achieved refraction in the ISBCS group and DSBCS group ( P =.80) [ ]. In a smaller, nonrandomized prospective study from Korea, the authors reported that IOL power was adjusted based on first eye refraction in approximately 1% of DSBCS eyes [ ]. In a large retrospective US-based study from Kaiser Permanente, the authors concluded that there was no difference in BCVA or refractive error in second eyes between ISBCS and DSBCS [ ]. In fact, they found slightly lower refractive errors (−0.36 D in ISBCS vs −0.39 D in DSBCS) and slightly higher rates of patients with BCVA 20/20 or better (52% of ISBCS, 49% of DSBCS) in patients who underwent ISBCS [ ]. Similarly, Spekreijse and colleagues reported no difference in the percentage of patients with refractive surprise, with less than 1% in both ISBCS and DSBCS [ ]. Overall, evidence is mixed regarding the proportion of patients for whom outcomes could be improved with delayed second eye surgery and the ability to update IOL power, though this number is likely small and the overall outcomes are very similar.
Special cases
Pediatrics
Pediatric cataracts have been proposed as a unique case for which ISBCS may be warranted not only for convenience but also for medical benefit. Primarily, supporters cite the potential to avoid dangerous side effects of anesthesia [ ] and the possibility of deprivation amblyopia with delayed surgery [ ]. Two groups retrospectively analyzed cases of ISBCS and DSBCS in children, primarily finding no difference in safety or outcomes [ , ]. Of note, in one of the studies, no differences occurred in intraoperative surgical complications or anesthesia-related adverse events, despite the ISBCS group having a significantly higher proportion of patients with systemic or ocular comorbidities [ ]. Both of these groups further analyzed cost savings, noting a significant reduction in societal and health system costs ranging from 15% to 21% [ , ]. Overall, ISBCS may be optimal for complex pediatric cases and cases with notable anesthesia-related or systemic comorbidities.
Down syndrome and cognitive dysfunction
A single retrospective study examined the use of ISBCS for patients with Down syndrome [ ]. The proposed benefit of ISBCS in these cases was again was based on avoiding general anesthesia. On the other hand, patients with Down syndrome are more likely to have ocular comorbidities such as refractive error and keratoconus, which may challenge the accuracy of IOL choices [ ]. Still, the authors of this study concluded that ISBCS was a reasonable consideration for patients with Down syndrome [ ]. Avoidance of 2 episodes of general anesthesia may similarly be beneficial in patients with advanced dementia or cognitive decline.
COVID-19
The COVID-19 pandemic dramatically altered the practice of medicine, particularly in the early phases of the pandemic. Ahmed and colleagues argued for the importance of considering ISBCS during the onset of the pandemic as a means for reducing patient and clinician exposures [ ]. Due to the perceived benefits and low risks, one study highlighted the use of ISBCS by trainees at an academic institution in Northern California, noting no major differences in outcomes or complications [ ]. Given the similar outcomes and risk profile of ISBCS, the avoidance of excessive visits due to the COVID-19 pandemic or any future pandemics is a reasonable factor to consider.
Economics
Many have studied the financial implications of ISBCS. Nearly all who have studied ISBCS from an economic perspective note cost savings at the societal level [ , , ]. These cost savings may be even more apparent in unique cases, such as those of pediatric cataracts [ ]. At a national level, Néel and colleagues estimated potential savings in the US with a complete switch to ISBCS to be $783 million annually, approximating $522 million in savings for payers and $261 million for patients [ ]. On a per surgeon or per surgery center level, cost savings may exist through small increases in operating room efficiency [ ].
The beneficiaries of those cost savings, however, may not be as clear, and many allude to the 50% reimbursement rate cut for second surgeries in the US. [ ]. Rush and colleagues analyzed such factors for various stakeholders including patients, providers, and payers, at a private practice group in Texas [ ]. They reported no net difference in provider surgery time and no cost savings for the ambulatory surgery center, but did note that physician reimbursement ($1340 vs $1705) and ambulatory surgery center reimbursement ($1813 vs $2369) were lower for ISBCS. Consequently, while payer total costs were lower ($3123 vs $4067), the provider group did not reap economic upside. This misalignment of incentives may contribute to negative perceptions of ISBCS by providers in the US. [ , , ].
From a patient perspective, ISBCS has clear economic benefits, often owing to a reduced number of clinic and surgical appointments and shorter total recovery time. One study measured the reduction in appointments (3.3 vs 7.1) and resulting driving distance for both in-town (41.8 vs 87.0 miles) and out-of-town (522.1 vs 969.3 miles) [ ]. Similar findings have been shown in international studies, whereby direct costs such as travel to appointments are reduced, as are indirect costs such as time off work [ ].
Summary
While ISBCS accounts for a small minority of cataract surgery in the United States, many feel that it should be used more often. Large studies have demonstrated no increased risk, particularly that of endophthalmitis, but the risk of bilateral postoperative endophthalmitis remains and still concerns many surgeons around the world. Outcomes of ISBCS appear to be noninferior to those of DSBCS, despite the inability to adjust IOL based on first surgery refraction. The macroeconomic benefits of ISBCS are clear, as they can reduce societal and patient costs; however, the misalignment of incentives for surgeons is likely a strong negative facilitator of increased use. Altogether ISBCS may become a larger part of clinicians’ future practice, there are still a number of key barriers to overcome.
Clinics care points
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ISBCS overall carries low risk for endophthalmitis.
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Outcomes of ISBCS are noninferior to DSBCS.
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ISBCS may be cost saving at a patient level and societal levelPitfalls:.
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ISBCS use may be limited due to lowered reimbursement to surgeons.
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