11.07.2015 Views

Verteporfin photodynamic therapy for neovascular age-related ...

Verteporfin photodynamic therapy for neovascular age-related ...

Verteporfin photodynamic therapy for neovascular age-related ...

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

20 Key changes to the protocolThese amendments did not alter the overall study design, the setting, the eligible studypopulation or the outcomes.Changes to study procedures relating to participating sitesAs the study progressed, more hospitals were designated to provide VPDT. At the start of thestudy, because of the novel and complex nature of the treatment, there was professional concernto restrict the provision of VPDT to designated centres in which specified doctors and otherpersonnel had been accredited by attending appropriate training, provided by the Royal Collegeof Ophthalmologists. As time passed, this policy became more difficult to sustain because ofthe inconvenience to patients in sparsely populated geographic areas. Some hospitals, togetherwith their commissioning PCTs which wanted the hospitals to provide VPDT, were unwilling toparticipate in the study. Un<strong>for</strong>tunately, despite the fact that policy-makers provided a lot of theimpetus to carry out the study, there was no NHS directive requiring centres to participate. It alsobecame clear at quite an early st<strong>age</strong> that participating sites were not complying with the follow-upschedule; this required the principal investigators to adapt the planned statistical analyses.Collection of additional predictors of visual functionThe data set being collected <strong>for</strong> the study was reviewed after 12 months. Because of evidenceabout the influence of other factors on BCVA, the Steering Committee accepted therecommendation of the principal investigators to ask centres to collect in<strong>for</strong>mation on additionalpotential confounding factors:■■smoking status 46–48■■use of statins 49■■family history of nAMD 50■■visual status of fellow eye. 51These factors were likely not to vary over time <strong>for</strong> a participant, and we asked centres to collectthe data at the next visit <strong>for</strong> participants who had already been recruited. At the time of thischange to the data set, there was only a small minority of existing participants who had alreadybeen discharged from treatment or lost to follow-up.Smoking status was classified as current smoker, ex-smoker or never smoked. The visual statusof the fellow eye (worse or better BCVA) was assigned based on BCVA data collected across theduration of the study. If the better-seeing eye varied across visits, that is both eyes had similarBCVA, the fellow eye status was classified as uncertain.Network of Ophthalmic Reading Centres in the UKIm<strong>age</strong>s from the VPDT cohort study were graded from 2004 to 2008 by NetwORC UK. Regulartraining and concordance exercises within the three designated reading centres ensured thereproducibility and reliability of grading outputs. During this period, improvements occurredin im<strong>age</strong> acquisition systems which led to an expansion in the knowledge of the differentphenotypes of nAMD. The expanded phenotypic spectrum was incorporated into the gradingvocabulary, and the grading protocols were also appropriately amended.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!