Dear Editor

We thank BV Kumar and S Prasad for their interest in our report describing the successful treatment of macular oedema (MO) secondary to branch retinal vein occlusion (BRVO) with intravitreal triamcinolone injection (IVTI).[1]

Although definitively establishing a clinical diagnosis of posterior vitreous detachment (PVD) may be problematic, our patient did not have a Weiss ring and no evidence of PVD in the macular region was visible on serial optical coherence tomography (OCT) scanning before or following treatment.

We believe it is unlikely that the primary mechanism of action of IVTI in treating MO is the induction of a PVD. We have treated another patient with OCT confirmed MO associated with BRVO which initially responded rapidly to IVTI with restoration of normal foveal contour and improvement in visual acuity. This patient subsequently developed recurrence of MO and visual loss one year following the initial treatment. Retreatment with IVTI resulted in a rapid improvement in visual acuity and restoration of foveal contour confirmed with OCT.

If induction of a PVD were the primary mechanism of IVTI efficacy in reducing MO, then repeated treatments with IVTI would not be expected to be efficacious as it would not be possible to induce a PVD more than once. This is at odds with our own frequent clinical experience of successful repeated IVTI’s for the treatment of recurrent MO associated with posterior uveitis or the reported efficacy of repetitive IVTI’s for MO associated with diabetic retinopathy [2] and pseudophakic cystoid MO.[3]

It might be interesting to speculate on the effect that the presence or absence of a pre-existing PVD may have on the efficacy of IVTA and we agree that it is important that such factors are considered in future reports.

References

(1) Prasad S, BV Kumar, S Prasad. How does intravitreal triamcinolone work? [electronic response to Chen et al. Intravitreal triamcinolone acetonide for ischaemic macular oedema caused by branch retinal vein occlusion] bjophthalmol.com 2004http://bjo.bmjjournals.com/cgi/eletters/88/1/154#275

(2) Martidis A, Duker JS, Greenberg PB, et al. Intravitreal triamcinolone for refractory diabetic macular edema. Ophthalmology 2002;109:920-7

(3) Conway MD, Canakis C, Livir-Rallatos C, et al. Intravitreal triamcinolone acetonide for refractory chronic pseudophakic cystoid macular edema. J Cataract Refract Surg 2003;29:27-33

Dear Editor

SDM Chen and colleagues present a case of successful treatment of macular oedema in the setting of ischaemic branch retinal vein occlusion (BRVO).[1]

Intravitreal triamcinolone is increasingly being used as part of our therapeutic armaterium in a wide range of conditions. However it’s mode of action is still to be fully elucidated. It is known that the induction of a posterior vitreous detachment (PVD) may have an important role in the resolution of macular oedema.[2] In patients undergoing an arterio-venous sheathotomy procedure for BRVO, surgical detachment of posterior hyaloid could be as important as the sheathotomy to improve macular oedema.[3]

In the reported case, it is possible that the intravitreal injection of triamcinolone may have induced a PVD and this may have contributed to the resolution of the macular oedema. Thus, it would be useful to know the status of the posterior hyaloid before and after triamcinolone injection in this case.

We feel that it is important that all relevant factors such as this are reported and discussed in this and similar reports in the literature. This will help us to evolve treatment alogarithms to target newer interventions such as intravitreal triamcinolone, to the patients most likely to benefit.

References

1. Chen SDM, Lochhead J, Patel CK, Frith P. Intravitreal triamcinolone acetonide for ischaemic macular oedema caused by branch retinal vein occlusion. Br J Ophthalmol 2004 Jan; 88: 154-5.

2. Yamaguchi Y, Otani T, Kishi S. Resolution of diabetic cystoid macular edema associated with spontaneous vitreofoveal separation. Am J Ophthalmol 2003 Jan; 135: 116-8.

3. Charbonnel J, Glacet-Bernard A, Korobelnik JF, et al. Management of branch retinal vein occlusion with vitrectomy and arteriovenous adventitial sheathotomy, the possible role of surgical posterior vitreous detachment. Graefes Arch Clin Exp Ophthalmol 2003 Dec 18 [Epub ahead of print].