Aim-To estimate risk of infectious endophthalmitis after cataract extraction inConclusion-Despite considerable diVerences in the healthcare systems, no statistically significant diVerence in outcome of surgery as measured by risk of endophthalmitis was shown between Denmark and the USA. (Br J Ophthalmol 1997;81:102-106)

During the sixth year following cataract surgery, the incidence of RD in the cataract group was still 7.5 (95% CI 1.6-22.0) times higher than that observed in the reference group. (Br_r Ophthalmol 1996;80:689-693) Retinal detachment (RD) following cataract extraction is a rare complication but when it occurs it is likely to threaten the visual outcome. Consequently, knowledge about the risk factors for RD and reliable estimates of the risk of RD are important to the cataract surgeon. However, most studies of RD after cataract surgery are based on patients treated by individual surgeons or at academic centres. ' Such series do not necessarily reflect complication rates in the overall health care system and may not be generalised.We calculated the risk of RD after cataract surgery in the Danish public health care system based on data from an administrative database. Such nationwide administrative databases can provide large sample sizes but they also have the advantage of showing the outcomes of treatment for a cross section of the population. As a cross national comparison can be a powerful method when assessing wider applicability of national clinical results, the Danish study was designed and carried out in close collaboration with the US National Study of Cataract Outcomes.7 We kept the definition of events and the method of data analysis in the present Danish study as close as possible to those used in the US study to maximise the comparability of the results. It is therefore possible for us subsequently to compare the Danish results to those previously reported from the US National Study.7 The results from the Danish cataract group were also compared with a reference group of people who did not undergo intraocular surgery. This was done to investigate whether an elevated risk of RD in the cataract group existed throughout the observation period or only during the first few years after the cataract surgery.

A previously identified variation in treatment modalities among the 4 sites did not have a significant effect on the odds of achieving an optimal functional outcome. In addition to visual acuity measurements, the VF-14 index provides information on functional outcomes that is useful, especially in studies assessing the benefits of cataract surgery in a public health care setting.