Abstract
To compare the efficacy of an intravitreal injection to a posterior subtenon injection of triamcinolone acetonide for the treatment of diffuse diabetic macular edema. Sixty patients with diabetes mellitus presenting with diffuse diabetic macular edema were recruited for the study. In each patient, one eye received a 4.0 mg (0.1 mL) intravitreal (IVT) injection of TA and the other eye was treated with a 40 mg (1.0 mL) posterior subtenon (PST) injection of triamcinolone acetonide (TA). We measured the visual acuity, the intraocular pressure (IOP) and the thickness of the macula using optical coherence tomography (OCT) before treatment and at one, three and six months after treatment. Eyes treated with PST showed 1-3 lines of improvement in Snellen's acuity from their pre-injection baseline visual status. The eyes in the IVT group showed 1-3 lines of improvement in Snellen's acuity in 80% of the treated eyes, but 20% of the treated eyes did not display any benefit at the end of six months. The difference in acuity between an IVT injection and a PST injection at six months post-treatment was statistically significant (p<0.05). The macular thickness of the eyes treated with an IVT injection was significantly reduced after one (222.7±13.4 μm; p<0.001) and three months (228.1±10.6 μm; p<0.001) of treatment. The eyes treated with a PST injection displayed a slow response and a significant improvement in macular thickness that was observed only after three months (231.3±10.9 μm; p<0.001). The difference between the eyes treated with an IVT injection (385.2±11.3 μm) and those treated with a PST injection (235.4±8.7 μm) was significantly different six months after treatment (p<0.001). The IOP of the eyes treated with an IVT injection was significantly increased after one (17.7±1.1 mm/Hg; p<0.020), three (18.2±1.2 mm/Hg; p<0.003) and six months (18.1±1.320 mm/Hg; p<0.007) when compared to the baseline value (16.1±1.4 mm/Hg). The eyes treated with a PST injection displayed no significant increase in IOP after one (16.4±1.2 mm/Hg; p<0.450), three (16.3±1.1 mm/Hg; p<0.630) and six months (16.2±1.1 mm/Hg; p<0.720) when compared to the baseline value (16.2±1.3 mm/Hg). A PST injection is equally effective and safer than an IVT injection of TA for the management of diffuse DME.
Highlights
Macular edema is the main cause of visual impairment in diabetic patients [1]
The benefit of 2-lines of acuity was observed in an equal number of eyes (20%) in both groups, and 1-line improvement was observed in 30% of the posterior subtenon (PST) group and 20% of the IVT group, which was not significant (Graph 1 and 2)
In the PST group, every eye showed some benefit resulting from the injection in terms of a visual acuity improvement compared to the IVT group, in which twelve patients (20%) failed to show an improvement in visual acuity of even 1-line (Table 1, Graph 3)
Summary
Macular edema is the main cause of visual impairment in diabetic patients [1]. Based on the observations of the Early Treatment Diabetic Retinopathy Study (ETDRS), diabetic macular edema (DME) has been classified as clinically significant if it is well-defined. Specific clinical features are associated with retinal thickening at or within 1 disc diameter of the center of the macula or with definitive hard exudates in this region. For this subgroup that experiences hard exudates in this region of patients, focal laser photocoagulation has been demonstrated to be an effective treatment [2]. The paucity of clinically significant gains in visual acuity after laser therapy as well as the recrudescence or persistence of DME after appropriate laser treatment, in eyes presenting a diffuse macular edema[2, 3], has led investigators to seek alternative treatments for the management of DME. Among the alternative treatments currently under investigation for DME, the administration of triamcinolone acetonide (TA), either by an intravitreal (IVT) injection [4,5,6,7,8,9,10,11] or by a posterior subtenon (PST) injection, [12, 13] has demonstrated promising results for the management of refractory or primary diffuse DME
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