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We appreciate the interest and many comments we have received regarding our recent article.1 In reply to the comments by Dr Vedantham, we acknowledge the paucity of experimental data to prove that accurate placement of corticosteroids into the sub-Tenon’s space provides good drug penetration into the eye. However, the studies to the contrary cited by Vedantham have all used needles to make such “accurate placement,” including the study by Jennings et al,2 which utilised the technique described by Tessler.3 Use of needles represents not only a potential hazard to the eye in terms of accidental globe penetration, but also makes it much more difficult to place any sub-Tenon’s injection under the posterior Tenon’s capsule near the macula and/or around the optic nerve. It has been shown that many injections intended for the sub-Tenon’s space merely end up somewhere in the orbit outside of Tenon’s capsule.4 We believe that our method using a 23 gauge blunt, curved, long cannula (the one we used was No HS-2764 by Handaya Co, Ltd, Tokyo, Japan) assures accurate placement into the target space, thereby increasing therapeutic efficacy and obviating the need for globe invasive procedures such as intravitreal injection of corticosteroids, corticosteroid intravitreal implants, and/or therapeutic vitrectomy.
However, we are in agreement with Vedantham, in that ultimately corticosteroid placed outside of the eye may be no match for the efficacy that may be obtained by corticosteroid placed inside the eye. Yet we have found such a high efficacy rate for the trans-Tenon’s retrobulbar infusion of triamcinolone in uveitis that we can conceive of no reason why this treatment should not be tried before procedures such as intravitreal injections that carry risks of severe complications are considered. For example, as also pointed out by Vedantham, the risks of intravitreal corticosteroid injections even include development of a rare form of mycobacterial endophthalmitis.5 Therefore, the risk to the eye of intravitreal procedures, especially when involving corticosteroid administration, cannot be taken lightly. Furthermore, we believe that the reason why sub-Tenon’s injections of corticosteroids have not become popular among retina specialists who for example treat diabetic macular oedema, is more likely related to the lower efficacy rate when using needles as opposed to the technique using an infusion cannula that we advocate. Lastly, obtaining the infusion cannula seems like a small inconvenience (and an even smaller cost) to the physician compared to the risk of doing intravitreal injections of corticosteroids as a treatment of first choice as advocated by Vedantham. We strongly encourage all uveitis and retina specialists who have up until now been disappointed with the efficacy of their sub-Tenon’s corticosteroid injections, to make the effort to obtain an appropriate cannula and revise their technique before jumping to intravitreal procedures.
In reply to the first comment by Dr Mehta,6 we acknowledge the current WHO guidelines, revised for 2003, that include recommendations for extrapulmonary tuberculosis.7 However, we would also like to amend Mehta’s comment, in that the WHO admits in those guidelines that there are many regimens with reported efficacy including a 6 month regimen of rifampicin (with streptomycin also given in the initial phase only) for meningeal tuberculosis. Furthermore, the WHO recommendations are for active extrapulmonary tuberculosis that has been diagnosed by specimen examination or strong clinical evidence, and give no recommendations for latent infection. As we have previously reported in a series on intraocular tuberculosis, systemic examination failed to identify a focus of active tuberculosis in the majority of our patients,8 and we have come to suspect that the uveitis we observed may be an immune response to latent tuberculosis antigen sequestered elsewhere. Therefore, the patients we described were given a diagnosis of “presumed intraocular tuberculosis,” that is with uveitis presumed to be related to the Mycobacterium tuberculosis organism. Furthermore, we would like to clarify that in the cases of presumed ocular tuberculosis that received trans-Tenon’s retrobulbar triamcinolone infusion,1 this treatment was judged to be effective in two of three eyes. Regardless, since the focus of active or latent tuberculosis was never identified in our patients, a two drug regimen of isoniazid and rifampicin was used as a therapeutic trial for antituberculosis therapy. A similar therapeutic trial for ocular tuberculosis, albeit with isoniazid alone, has been previously advocated in Japan by Ishihara and Ohno.9
With regard to the second comment, among the 16 patients who were receiving some form of systemic immunosuppressive therapy, we did not notice any difference in outcome when compared to patients who were not on immunosuppressive therapy. In other words, the efficacy of trans-Tenon’s retrobulbar triamcinolone infusion was the same. However, we suspect that the recurrence rate after triamcinolone infusion may be different, and we are currently investigating this possibility.
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