Sir,

We read with interest the study of Causes of blind and partial sight certifications in England and Wales: April 2007—March 2008.1 It was stated that ‘The numbers of certificates are also lower than the figures reported as registered at Social Services’. This finding was interesting to us as we had noted a similar problem while performing a cross-sectional study of all Certificates of Vision Impairment (CVI) for Bristol and North Somerset between September 2005 and September 2008. We found that 54 patients were registered separately at both Bristol and North Somerset Social Services. All these 54 patients had been referred from North Somerset into Bristol for sub-specialty ophthalmology assessment and had a CVI completed in Bristol Eye Hospital. The patient was entered onto the Bristol Social Services register at that visit. The CVI was later forwarded to North Somerset Social Services and entered onto their register. The patient was not deleted from the Bristol register and therefore these patients, representing 5.3% of all patients in our study, would be counted twice when the individual Social Services figures were forwarded to The Health and Social Care Information Centre. However, due to the way the CVI forms are processed locally, only one copy of the CVI form would be forwarded to the Certifications Office in London. If this problem was duplicated around other regions in England and Wales, then it may explain a proportion of the discrepancy noted by Bunce et al.1