Our study confirms the association of tamsulosin with IFIS. However, 43% of our patients receiving tamsulosin did not have any features of IFIS. The absence of IFIS has been previously noted in some patients receiving tamsulosin.
1 It is important to recognise that taking tamsulosin does not always result in IFIS. Duration of treatment, dose of tamsulosin, individual susceptibility to the drug, drug kinetics and coexisting ocular and systemic factors may all have some part to play in determining which of the patients receiving tamsulosin will develop IFIS.
The IFIS can have a range of severity of iris pathology.
6 Our results suggest the same. It is important to recognise an incomplete form of the syndrome that is also markedly associated with tamsulosin. We believe that incomplete IFIS can cause intraoperative problems similar to complete IFIS and requires similar management.
It has been suggested that discontinuing tamsulosin before cataract surgery may be helpful in preventing this syndrome.
1,7 In the absence of objective evidence, we do not recommend stopping tamsulosin before cataract surgery. The use of iris hooks should obviate any need to alter ongoing treatment. Further, intracameral phenylephrine has been shown to be effective in preventing IFIS in these patients.
8Some have suggested that IFIS may represent an effect of all α‐1 blockers, albeit differing in its severity.
3,4 IFIS caused by alfuzosin has been reported.
9 Terazosin and doxazosin have also been anecdotally implicated.
10 Our study had 48 patients who were receiving doxazosin, and only one had incomplete IFIS. Our findings support the theory that high affinity of tamsulosin for α‐1A receptors underlies the pathogenesis of IFIS.
1 Non‐selective α‐blockers are unlikely to be associated with IFIS.
In all, 14% of our patients had diabetes. Three of them had a small pupil, a feature well documented in diabetes.
11,12 We found no marked association between diabetes and IFIS. We found no evidence that it contributes to iris prolapse or a floppy iris.
Three of our patients with IFIS had high myopia. Surgical techniques used to counteract technical difficulties in cataract surgery in high myopia may contribute to the features of IFIS. A more posteriorly located corneal incision increases the chance of iris prolapse
13 but may aid phacoemulsification in high myopia. As we did not study this parameter prospectively, we cannot draw any marked conclusion regarding its significance.
One of the patients with incomplete IFIS was previously receiving pilocarpine, thus explaining the small pupil. One other patient with IFIS had a poorly constructed incision that could have led to iris prolapse.
13 However, there still remain several patients showing features of IFIS without any apparent explanation. Zuclopenthixol, an antipsychotic drug, has been associated with IFIS.
14 There are possibly other drugs and other ocular and systemic factors that may be similarly responsible.
The subjectivity of IFIS features has been highlighted previously.
15 A distinction may be made between poor preoperative pupillary dilatation and progressive pupillary constriction, both of which can occur in IFIS. In our study, we did not collect data on these two features separately. We arbitrarily chose 5 mm as the cut‐off for the surgeon to report a pupil as inadequately dilated at any time during the surgery. In real situations, a surgeon would rarely attempt to measure the pupil size. This decreases the accuracy of reporting this feature. The detection of a floppy iris also remains a subjective assessment of the surgeon. Thus, there will always remain a measure of inaccuracy in the reporting of IFIS.
Our study has limitations. A large number of surgeons reported the IFIS cases. They may have varying techniques with respect to incision and phacoemulsification parameters. The subjectivity of IFIS features further complicates the issue. The criteria we used were more liberal than the original definition of IFIS. Our attempt was to quantify the features and obtain greater uniformity between our surgeons. Despite this, our study design may have led to under‐reporting of IFIS. However, the results are highly significant in our resultant large group of patients.
Tamsulosin is the most commonly prescribed drug for LUTS. Yet, our study population had only 1.2% of patients receiving tamsulosin. This is in contrast with Chang and Campbell's figure of 2.5%. We collected this information prospectively, thereby reducing the chance of inaccurate data capture. Geographical variations in prescribing tamsulosin are documented in the USA.
16 We could not obtain similar data for the UK. The prevalence of LUTS in Scotland was found to be 18%, as opposed to 38% in the USA.
17 The prevalence of LUTS and the prescribing practice of general practitioners and urologists in a region will have a direct effect on its incidence of IFIS.
In conclusion, we believe that the floppy iris syndrome manifests as a continuum of severity. The pharmacological, ocular and systemic factors determining this need further investigation. Our study confirmed the association of tamsulosin use with IFIS, albeit in varying severity. However, doxazosin was not associated with this syndrome. In addition, we found diabetes to have no relationship with IFIS. Finally, we would like to emphasise that not all patients taking tamsulosin will necessarily have IFIS and not all patients with IFIS will necessarily be taking tamsulosin.
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Distribution of the patients taking α‐antagonists