Cataract complications study: an analysis of adverse effects among 14,520 eyes in relation to surgical experience

Introduction

Technological advancement has made cataract surgeries faster and safer. Regardless the general decline observed in rates of adverse events several patient and ophthalmic characteristics have been associated with increased risk of perioperative complications. These characteristics comprise e.g., pseudoexfoliation (PXF) and zonular weakness, use of α1-blockers, dense cataracts and poor mydriasis (1). Moreover, the level of surgeons’ experience and annual operation volume were recognized as factors correlating with the frequency of cataract surgery adverse events. Among patients over 90 years of age, ocular comorbidity and worse preoperative visual acuity also significantly increased the risk of complications (2).

A variety of methods have been applied to assess the resident-performed cataract operations learning curve including. Evaluation of the frequency of complications [particularly posterior capsule rupture (PCR)], the frequency of attending surgeon takeovers, or the gradual decline in the operation time (1,3). Complication rates were found to decline significantly after the first 200 operations (4-6). A steadier decrease in the complication rate was noted at 3,000 phacoemulsifications (7). Remarkably, a peak in the complication rates was observed as a consequence of residents gaining experience followed by diminished supervisor intervention (8).

Poorly dilated pupils were associated with increased complication rates both for residents and senior surgeons (9), whereas iris complications were likely to take more time from resident surgeons (10). Longer cataract surgery operation time predicted lower visual outcomes (11) or poorer patient satisfaction (12). Furthermore, PXF and the use of α1-blockers were associated with reduced post-operative visual acuity (13). To reduce the rate of complications, such as PCR and vitreous loss, the installation of surgical curriculum in the residency program was suggested (14,15). Posterior capsule rupture, in turn, was associated with 42-fold risk for retinal detachement and 8-fold risk for endophthalmitis within 3 months after cataract surgery (16). Implementation of wet-labs and surgical simulators in cataract surgery training were found comparably effective in terms of improving residents’ surgical abilities, although residents with wet-lab training required less operation time (17). In a large study the use of surgery simulator was found to reduce the PCR rate by 38% (18). The use of simulators has been shown to improve surgical skills among novice and even intermediate level surgeons (19,20). In addition, simulators can be used to assess competency in ocular surgery (21). A method for a systematic step-by-step assessment of resident performed cataract operations was developed to better recognize the sites of improvement (22). An attempt has been made to pre-evaluate a surgeon’s risk for PCR with respect to surgeon experience level (23).

Here, we examined the frequency of posterior capsule rupture and/or loss of capsular bag support between years 2009–2017 with respect to surgical experience. Further, we analyzed the outcomes of eyes with complications and discuss advances in surgical operation training during the study period.

Methods

This study was carried out as a retrospective cohort study at the Unit of Ophthalmology, Kymenlaakso Central Hospital, Kotka, Finland. The study was approved by the Research Director and Chief Medical Officer of the Kymenlaakso Central Hospital and the tenets of the Declaration of Helsinki were followed. Confidentiality of the patient records was maintained when the clinical data were entered into a computer-based standardized data base for analysis.

Patients

We reviewed the registry of operations for phacoemulsification cataract surgeries and posterior capsule ruptures and/or loss of capsular bag support between 1/8/2009 and 31/7/2017. Indications for phacoemulsification cataract surgery were based on the National Current Care Guidelines for Senile Cataract Surgery. The patient age distribution over the study period is represented in Figure S1. The Guidelines remained constant regarding patient eligibility for surgery “A patient is eligible for referral when best-corrected visual acuity (BCVA) in the better eye is ≤0.5 and in the weaker eye ≤0.3 measured in E-snellen lines” [Duodecim 2010;126(21):2541-2, updated in year 2013].

Surgery

The pre- and intraoperative methods employed to decrease the rate complications are summarized in Table 1. Structured referral for cataract surgery was demanded for all patients from year 2014 onwards (Figure 1). Simultaneously, cataract surgery risk stratification was implemented for coordination of operations with respect to the required level of surgeon competency (Table S1).

Table 1 Methods employed to decrease the rate of operative complications in cataract surgery in Kymenlaakso Central Hospital, Kotka, Finland, during the years 2009–2017
Full table

Figure 1 Referral for cataract operation. AMD, age-related macular degeneration; BCVA, best-corrected visual acuity; IOP, intraocular pressure.

The patients were examined by the operating ophthalmologist preoperatively on the day of surgery. Cataract surgeries were performed by three seniors, three specialists, and 19 residents in ophthalmology. The level of surgical skill between specialists and seniors was defined according the surgical education responsibilities. Seniors are supervising doctors in ophthalmic surgery for residents, while specialists have finished their residency and work as independent full-time employees. All three specialists had performed their surgical training already during residency. For the residents, only the first 100 operations were counted to the registry to maintain the follow-up throughout the study period comparable as some of the residents performed markedly higher numbers of surgeries.

A 2.75 mm clear cornea incision was used throughout the study period. The predominant phacoemulsification technique over the study period was divide and conquer (hrrg.fi/en/videos/cataract/).

Data analysis

Data are given as mean ± SD, except for the absolute numbers and proportions for the nominal scale. IBM SPSS Statistics 25 (SPSS Inc., Somers, NY, USA) was used for data analysis. Categorical data were analyzed with the two-factor chi-square test. BCVA was analyzed with nonparametric Mann-Whitney U test and normally-distributed continuous variables with the t-test. A mixed-effects logistic regression model, incorporating repeated measurements, was fitted during the statistical analysis. P≤0.05 was considered statistically significant.

Results

Baseline variables

The number of operated eyes were 10,724 for seniors (73.9% of all operations), 2,473 for specialists (17.0%), and 1,323 for residents (9.1%) (Table 2). Of the total 144 PCR and/or loss of capsular bag support (total incidence from 14,520 surgeries; 0.99%), 75 were recorded at the phacoemulsification phase (52.1%), 34 at the irrigation/aspiration (I/A) phase (23.6%), 10 at the IOL implantation phase (6.9%), and 25 in non-specified/other phase of the surgery (17.4%) (Table 3, Table S2).

Table 2 Incidence (%) of posterior capsule rupture and/or loss of capsular bag support according to surgical experience
Full table

Table 3 Surgical phase when posterior capsule rupture and/or loss of capsular bag support was noticed
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Baseline variables of eyes with complications regarding the age and gender distribution, BCVA, incidence of small pupils and PXF are presented in Table 4. Baseline characteristics indicate poorer BCVA, and overrepresentation of small pupils and PXF eyes subjected to complication towards the start of the study period (Table 4).

Table 4 Baseline characteristics of eyes with posterior capsule rupture and/or loss of capsular bag support
Full table

Incidence and outcomes of PRC and/or loss of capsular bag support over the study period

Over the study period the incidence of PCR and/or loss of capsular bag support remained constant among senior surgeons (from 0.36% to 0.32%; range, 0.31–0.46%, Table 2). Decline in the complication rates over the study period was observed among specialists (from 4.22% to 0.67%; Table 2), and likewise among residents (from 7.03% to 1.32%, Table 2). Overall, the frequency of cataract surgery complications has been decreasing since the year 2009 (P<0.001). Regarding surgeon’s professional experience, a specialist was 46.6% (95% CI: 15.3–66.4%, P=0.008) and a senior clinician was 92.4% (95% CI: 88.1–95.1%, P<0.001) less likely to encounter complications as compared to a resident. Interestingly, over the study period a senior clinician was 85.7% (95% CI: 75.6–91.7%, P<0.001) less likely to encounter complications when compared to a specialist.

The number of post-operative visits was 3.5±1.7 at the beginning of the study period and 3.0±1.7 at the end of the study period (Table 5). BCVA at the final visit was 0.61±0.16 decimals at the beginning of the study period and 0.81±0.19 decimals at the end of the study period (Table 5).

Table 5 Outcomes of posterior capsule rupture and/or loss of capsular bag support
Full table

The number of post-operative visits and BCVA at the final post-operative visit was comparable between surgeries performed by the residents and non-residents (Table S3), and between complications according to the surgical phase (Table S4). Small pupils and PXF were overrepresented in eyes with a need for AC-IOL (incidence of small pupils 24% vs. 9%, P=0.013, and of PXF 42% vs. 9%, P<0.001, among those with and without AC-IOL, Table S5). With respect to IOL positioning, having anterior chamber (AC)-IOL the number of post-operative visits was higher (5.2±3.5 vs. 3.8±2.1, P=0.006, Table S5) and BCVA at the final post-operative visit lower (0.46±0.27 vs. 0.71±0.23, P<0.001, Table S5) when compared to complications without the need for AC-IOL.

Discussion

The safety of patients must be guaranteed in public teaching hospitals particularly when surgeries are performed by non-skilled residents. Phacoemulsification cataract surgery has a relatively steep and long learning curve (24). For example, the study by Randleman et al. showed that the risk of PCR is 6.3% in the first 80 cases and 3.5% in the next 80 surgeries, which is much higher than the complication rates reported in large studies (5,25). In another investigation, the overall PCR rate in resident-performed surgeries reached 17.3% in 183 cases (26). Various methods have been utilized to decrease the risk of complications in resident-performed surgeries including early introduction of cataract surgery training during the residency (15), one-step rather than stepwise introduction of various surgical maneuvers (26), employing an extensive surgical curriculum (14) along with surgical simulator (27) and wet-lab training. Moreover, the use of risk stratification system prior to cataract surgery is widely accepted and practiced with small variations around the world (1). For example, it has been suggested that the Buckinhamshire risk assessment better correlates with post-operative complications, while the Muhtaseb variation is more accurate in predicting intraoperative complications (28). A structured risk stratification not only allows routine assessment by referring ophthalmologists, but also helps in gathering information for systematic evaluation.

Within our study it is difficult to relate the risk reductions to any single improvement, either in the preoperative or perioperative phase. During the follow-up and assessment of the study, the national guidelines have remained the same for cataract surgery eligibility. The patients’ average age at surgery has also remained constant. Thus, the indications for surgery are comparable throughout the study period. In this single site retrospective cohort study, we found a gradually declining rate of complications among residents and improved BCVA at the final visit towards the end of the study period, whereas no significant variation was observed in the number of post-operative visits. The use of AC-IOL was associated with a higher number of post-operative visits and the lower BCVA at final postoperative visit.

Small pupils and PXF were more frequent among non-resident surgeons when compared to the residents, which reflects the allocation of risk patients with the risk stratification system. The greater rate of female patients in resident-performed surgeries compared to non-residents could be associated with patient stratification; e.g., the medical treatment for benign prostatic hyperplasia involves predominantly men and such patients were directed to more experienced non-resident surgeons. This partially could have accounted for our low complication rates; within the final period of our study the incidence of PCR among resident-performed surgeries was only 1.32%. This is one of the lowest values reported for phacoemulsification cataract surgery {Table 6 [Sources: (29-32)]}. Low et al. presented a PCR rate of 0.8%; however, in their study 18% of resident-performed cases were performed with an attending surgeon (33). Moreover, there was no difference in overall complication rates between resident and staff surgeons in their study, although it is not clear how patient selection was conducted. Low PCR rates, under 2%, were also reported by other authors (15,34,35); however, in some studies such low rates were achieved only in the final phase of training and not presented as an overall complication rate through the whole training period (35).

Table 6 Studies analyzing the posterior capsule rupture rate (PCR) in resident-performed phacoemulsification cataract surgeries (published within the last 10 years and involving a minimum number of 100 surgeries per study)
Full table

In addition to higher intraoperative complication rates, which obviously are related with insufficient surgical skills, also other hazards associated with resident training have been reported. Resident-performed cataract surgery can predispose to persistent postoperative inflammation; in the study by Patel et al. 6.6% of eyes suffered from such inflammation which was classified as idiopathic, due to a complicated cataract surgery or nonadherence to topical therapy (36). Moreover, it is estimated that resident-performed surgeries can take up to 27 minutes longer than those performed by attending surgeon; this could translate to an average additional cost of $105.40 per surgery with the cost of running an operating room in mind (37).

This study has several limitations. First, we could not specify the efficacy of any particular method employed to decrease the rate of complications during surgery. Thus, we cannot recommend one specific practice to improve surgical outcomes in resident-training. Second, we did not analyze the complication rates and the advancement in resident training in particular timeframes; this data could reveal more detailed information regarding the learning-curves. Nevertheless, we believe that our study presents real-life statistics and highlights the fact that with proper methodology it is possible to significantly decrease intraoperative complication rates among residents as well as experienced surgeons.

What was known

• Intraoperative complication rates for resident-perform cataract surgery vary greatly, however, in several studies they are higher than for experiences surgeons;
• Patients with PXF syndrome or with a small pupil are at risk of developing intraoperative complications during cataract surgery.

What this paper adds

• Several methods can be applied to decrease the complication rates in cataract surgery including patient risk stratification, employing virtual reality simulators and wet-lab training, irrigation/aspiration with a silicone tip and video recording for feedback;
• Within this study, we were able to reduce the posterior capsult rupture rate from 7.03% to 1.32% in residentperformed surgeries, and from 4.22% to 0.67% in specialist-surgeons.

Acknowledgments

We thank Ms. Reetta Österberg and Ms. Enni Särkkä for their valuable work as research assistants.

Funding: The study was supported by grants from the Finnish Eye Foundation, Finnish Ophthalmological Society, the Nissi Foundation, Orion Research Foundation, the Paulo Foundation, the Waldemar von Frenckell Foundation, Glaukooma tukisäätiö LUX, and the HUS Specific Catchment Area (ERVA) Clinical Research Grants.

Footnote

Provenance and Peer Review: This article was commissioned by the Guest Editor (Dr. Andrzej Grzybowski) for the series “Recent developments in cataract surgery” published in Annals of Translational Medicine. The article was sent for external peer review organized by the Guest Editor and the editorial office.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/atm-20-845). The series “Recent developments in cataract surgery” was commissioned by the editorial office without any funding or sponsorship. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was approved by the Research Director and Chief Medical Officer of the Kymenlaakso Central Hospital and the tenets of the Declaration of Helsinki were followed.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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