Background/aims As part of the UK and Ireland study of primary IOL implantation in children under 2, active surveillance has been undertaken to identify children aged <2 years undergoing surgery for cataract. Ascertainment through active surveillance has been compared to the routine NHS capture of episodes of surgery, in order to identify any weaknesses in routine data collection.

Methods NHS information centre data on the number of children undergoing lens extraction in the first two years of life were compared to the number of cases reported through active surveillance.

Results In 2009 and 2010 in the United Kingdom, 483 episodes of lens extraction in children aged <2 years with lens-related disease were reported to NHS databases, compared to 490 cases of lens extraction for congenital / infantile cataract ascertained by the BCCIG through active surveillance. There was also disparity in the coding of procedures.

Conclusions There is evidence of incomplete and inaccurate reporting to NHS information centres of cataract surgery in children aged <2 years. If the accuracy of the coding could be improved then the Hospital Activity Statistics offer a reasonable approach to monitoring trends in the NHS. Nevertheless, active surveillance clinical networks remain a more robust method of case ascertainment for research.