Posterior subtenon versus intravitreal triamcinolone acetonide injection for the treatment of diabetic macular edema

Background
Diabetic macular edema (DME) is the most common cause of loss of vision in diabetic patients. The role of inflammation in the pathogenesis of DME has been demonstrated. An intravitreal (IVT) injection of triamcinolone acetonide (TA) is a treatment option for DME. The high incidence of side effects, however, limits the routine use of IVT TA.
Aim
The aim of this study was to compare the efficacy and safety of an IVT injection of TA with the less invasive posterior subtenon (PST) injection of TA. We test the hypothesis that both techniques have equal efficacy and safety.
Patients and methods
This is prospective randomized noninferiority trial. Totally, 34 eyes from 30 patients with diffuse center involving DME were randomized in a 1: 1 ratio to receive a TA injection by either method. Baseline evaluation included measurement of best-corrected visual acuity (BCVA) and intraocular pressure (IOP), fundus fluorescein angiography, and optical coherence tomography to measure central macular thickness (CMT) and evaluation of the crystalline lens. After the injection, patients were seen at 1 week, 1 month, 3 months, and 6 months and their BCVA, CMT, IOP, and change in these measures from baseline as well as other complications were recorded. A Mann–Whitney -test was used to compare the mean of quantitative variables and a -test was used to compare qualitative variables between the two groups.
Results
At baseline, both groups showed no statistically significant difference in age, sex, IOP, BCVA, and CMT. At 1, 3, and 6 months, both groups showed no statistically significant difference in the mean BCVA as well as change in BCVA from baseline. The average reduction of CMT was significantly higher only in the IVT group at 1 month ( = 0.03). The mean IOP and average IOP change from baseline were significantly higher in the IVT group than the PST group only at 3 months after injection ( = 0.02). Both groups showed a similar incidence of development of cataract ( = 1.0, ).
Conclusion
IVT injection of TA is more effective than PST injection in improving CMT – that is, anatomical outcome. This is not, however, translated into a superior visual outcome. The risk of IOP elevation is also higher in IVT than PST injection. PST is a valid alternative to an IVT injection, especially from the functional perspective and when the risk of IOP elevation is significant.