We read the response by Syed et al to our study with interest and are surprised by the conclusions they have drawn from our paper.It was stated clearly in our article that between 2002 and 2005 the senior author performed dacryocystorhinostomy (DCR) with a stent. As his success rate was lower than comparable evidence, he decided to change his practice in the hope of improving his results and performed DCR without a stent between 2005 and 2006.Syed et al’s queries regarding stents (including removal time) have already been addressed in the methods section of our paper. In the stented group, the stents were removed at three months following surgery. We believe and understand that this is not premature as stent removal can vary from 4 to 24 weeks postoperatively.As for Syed et al’s comment on higher subjective success in the non-stented group, it was stated clearly in our publication that the use of stents was associated with eye irritation, displacement of the tube at the medial canthus, nasal crusting and granulation formation at the rhinostomy orifice, which can affect the outcome. This has been supported by the literature in that a stent can be the reason for surgical failure owing to causing granulation tissue formation, synechia formation and punctual erosion.Syed et al’s comparison of our study with contradictory evidence in the literature including their own study seems selective. There is clear evidence available in the literature for and against the use of stents in DCR and this was acknowledged in our introduction. Several studies (including a prospective randomised study) show a higher success rate in DCR without stents.
Our study concluded that stents are not necessary for primary DCR. This conclusion has been supported by two meta-analyses.The postsaccal blockage for our patients was tested by the ophthalmologists, who used dacryocystography where indicated. This was a very small group of patients and was deemed too insignificant a finding to be elaborated on in our article.Generally, a retrospective power calculation is not advised. It is not regarded as good practice and if the result of a retrospective study is significant, power is of no interest.
It would appear that prospective power has been confused with retrospective power. Depending on how retrospective power is calculated, it might be legitimate to use it to estimate the power and sample size for a future study but it cannot be used legitimately as describing the power of the study from which it is calculated.