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Quality assessment of cataract surgery in Denmark – risk of retinal detachment and postoperative endophthalmitis

The overall aim of this thesis was to assess the quality of cataract surgery in Denmark by studying the risks of two serious postoperative complications following cataract surgery: pseudophakic retinal detachment (PRD) and postoperative endophthalmitis (PE). Furthermore, the purpose of the thesis was to examine whether data from the Danish National Patient Registry (NPR) could be used to monitor these complications in order to improve the quality of cataract surgery in Denmark in the future. The thesis consists of four retrospective studies which are based on data from the Danish cataract registries in the study period 2000–2012. In paper I (Bjerrum et al. 2013), we used data from the NPR to study the risk of PRD in 202 226 patients using the fellow nonoperated eyes as reference. The risk of PRD was equal to the risk of retinal detachment (RD) in fellow non-operated eyes multiplied by a factor caused by the cataract operation. Over a 10year calendar period, cataract surgery increased the risk of PRDby a factor 4.2 irrespective of age and sex. The risk of PRD was highest in the first 6 months after cataract surgery and then gradually declined but remained statistically significantly elevated up to 10 years after cataract surgery. Young men had the highest absolute risk of PRD because they had a higher risk of RD before they underwent cataract surgery. This is clinically relevant because young men must be informed of the increased risk of PRD if they consider phacoemulsification cataract surgery. Data from the NPR were also used in paper II (Solborg et al. 2013) to compare the risk of PE following cataract surgery at eye departments in public hospitals and private hospitals/ eye clinics between 2002 and 2010. Chart review and data from the NPR were used to verify the diagnoses of PE and to register where the cataract operations were performed. The risk of PE after registered cataract surgery at eye departments in public hospitals was 0.36 per 1000 operations, and the risk of PE was homogenous among the eye departments. The risk of PE after registered cataract surgery in private hospitals/eye clinics was 0.73 per 1000 operations, but the risk of PE was heterogeneous among the private hospitals/eye clinics. Six private hospitals/ eye clinics had a statistically significantly higher risk of PE after registered cataract surgery compared with the eye departments in public hospitals. The study revealed that 98% of the cataract operations performed in public eye departments that led to PE were registered in the NPR, whereas only 38% of the cataract operations performed in private hospitals/eye clinics that led to PE were registered in the NPR. In paper III, NPR data and chart review were used to compare the risk of surgical complications to endophthalmitis after cataract surgery in 91 patients who underwent a pars plana vitrectomy (PPV) and 30 patients who underwent a vitreous tap (VT; Solborg Bjerrum et al. 2014). In all, 24.2% of the patients who underwent a PPV and 36.7% of the patients who underwent a VT developed surgical complications. This difference was not statistically significant. However, patients who underwent a VT had a statistically significantly (p = 0.047) higher risk of surgery for vitreous opacities. Compared to the landmark Endophthalmitis Vitrectomy Study from the 1990s (Results of the Endophthalmitis Vitrectomy Study 1995), we found similar risks of retinal detachment (7.4%) and surgery for vitreous opacities (3.3%) but a higher risk of additional surgery for PE (13.3%) and removal of the eye (7.4%). Ten per cent of the patients developed more than one surgical complication, and 97% of the primary surgical complications occurred within the first 5 months. This is clinically important because patients who undergo surgery for PE following cataract surgery must be informed that they are at an increased risk of surgical complications during the first 5 months after surgery. Paper IV compared the epidemiology of 411 140 cataract operations performed in public hospitals and private hospitals/eye clinics between 2004 and 2012 (Solborg Bjerrum et al. 2015). In this study, data were used from all three Danish cataract registries: the NPR, the National Health Insurance Service Registry (NHI) and the ‘Registry of Danish patients treated in hospitals in other countries and activities in private specialist practice that are not settled by the health insurance agreement’ (DUSAS). We found that patients who had cataract