The effect of triamcinolone acetonide combined with bevacizumab on ocular parameters and VEGF in refractory DME

Authors

Abstract

Aim To investigate the effects of intravitreal injection of triamcinolone acetonide (TA) and bevacizumab(BEV) on ophthalmic artery (OA), central retinal artery (CRA), nasal posterior ciliary artery (NPCA), temporal posterior ciliary artery (TPCA), VEGF, IL-6 levels, and other factors in patients with refractory diabetic macular edema (DME).
Materials and Methods In this randomized double-blind trial, 80 refractory DME patients (mean disease duration: 5.2 years) were assigned to: Control group (n = 40): 4mg TA monotherapy; Combination group (n = 40): 1.25mg BEV + 2mg TA. Intervention: Monthly injections ×3. Primary outcomes included peak systolic velocity (PSV) and aqueous humor biomarkers (ELISA). Secondary outcomes encompassed best-corrected visual acuity (LogMAR), central macular thickness (CMT), and adverse events.
Results Compared with TA alone, the combination of TA and BEV significantly decreased the levels of VEGF and IL-6, and increased the blood flow of OA, CRA, NPCA and TPCA and the levels of NOS. In addition, the combination therapy also improved best corrected visual acuity (BCVA), reduced retinal thickness, and reduced the incidence of complications such as anterior chamber inflammation, hypopyon, corneal edema, and elevated intraocular pressure.
Discussion TA combined with BEV in the treatment of refractory DME can significantly improve the blood flow parameters of ocular blood vessels, reduce the level of VEGF, so as to effectively reduce macular edema and improve the vision of patients. Compared with TA alone, combination therapy may have more significant efficacy and better safety.

Keywords

Introduction

DME is caused by poor long-term blood glucose control in diabetic patients, which leads to microvascular lesions in the fundus and fluid accumulation and edema in the macular area [1, 2]. These processes may involve leakage of retinal blood vessels, formation of micro-hemangiomas, and exudation of blood components, all of which can compress photoreceptor cells and affect retinal function, especially in the macula [3, 4]. The macular area is the most sensitive area of vision, and its edema will significantly affect the patient’s vision. As a serious complication of diabetic retinopathy, DME is one of the main causes of vision loss and even blindness in diabetic patients. Incidence of DME in diabetic patients ranges from 5.2% to 7.6%. In China, the average course of DME is 5.2 years [5]. However, there are several factors that may lead to the failure of therapy, including the irreversibility of vascular destruction, complications and individual differences, and the limitations of treatment plans, which lead to ineffective or recurrent conditions and eventually form refractory DME, which is very difficult to treat in clinical practice. In recent years, intravitreal injection of drugs has become an important means of DME treatment because it directly acts on the lesion site, has significant efficacy and safety [6, 7]. TA can effectively inhibit the inflammatory response and reduce the leakage of retinal microvessels, and is commonly used in clinical treatment of inflammation and edema caused by DME. However, the action time of TA is relatively short, and patients need repeated injections to achieve sustained therapeutic effect, which limits its clinical application to a certain extent. TA may cause a variety of side effects and complications, such as increased blood glucose, cataract, ocular hypertension, glaucoma, etc. These side effects may not only affect the patient’s vision recovery but also increase the risk and complexity of treatment. In addition, the degree of disease in patients with refractory DME is usually severe, and there may be extensive retinal microvascular changes, ischemia, hypoxia, and neovasculogenesis. These complex pathological changes may make it difficult for TA to fully exert its efficacy.
The pathogenesis of DME is complex, involving inflammation, vascular leakage, and neovascularization, among which the over-expression of VEGF is considered to be the key driving factor [8, 9]. Therefore, targeted therapy against VEGF and its related pathways has become an important strategy for DME management. BEV can prevent VEGF from binding to VEGFR-1 and VEGFR-2 receptors on the surface of endothelial cells, thereby invalidating the biological activity of VEGF, so as to achieve the effect of inhibiting angiogenesis and reducing vascular leakage [10]. By inhibiting the activity of VEGF, BEV reduces the proliferation and migration of vascular endothelial cells to inhibit the formation of new blood vessels and reduce macular edema[11]. Studies have shown that intravitreal injection of BEV can significantly improve the visual acuity of patients with DME, accelerate the absorption of subretinal fluid, and reduce the degree of macular edema [12]. Therefore, it is necessary to investigate the combination of multiple drugs in the treatment of refractory DME. As a long-acting glucocorticoid, TA has a significant anti-inflammatory effect, which can reduce capillary permeability and intraocular fluid exudation, thereby alleviating macular edema [13]. The main mechanism of TA is to reduce the inflammatory response by inhibiting the production of proinflammatory factors such as interleukin-1β [14]. In addition, triamcinolone acetonide can inhibit immune response and reduce tissue damage and edema in the macular area caused by immune responses [15].
For patients with refractory DME, TA alone may have a poor therapeutic effect [16, 17]. TA combined with BEV in the treatment of macular edema can play a dual role in anti-angiogenesis and anti-inflammatory, thereby improving the treatment effect [18, 19, 20]. However, despite the remarkable results of combination therapies in improving visual acuity in DME patients, their specific effects on ocular vasculature in patients with refractory DME have not been fully elucidated. As important sources of ocular blood supply, the changes of blood flow parameters (OA, CRA, NPCA and TPCA) may directly affect the visual function recovery and prognosis of DME patients. Therefore, this study aims to compare and analyze the effects of TA and BEV on the blood flow parameters of OA, CRA, NPCA, TPCA and the levels of VEGF, NOS and IL-6 in patients with refractory DME, and further explore the mechanism of action and safety of these two drugs in the treatment of DME, so as to provide a scientific basis for clinical optimization of treatment plans.

Materials and Methods

Participants and Screening
This study was a randomized, double-blind, parallel-controlled clinical trial. The inclusion criteria of the study subjects were as follows: diabetic patients with intractable DME, aged 18- 75 years. After the patient had received at least 3 different intravitreal injections of anti-VEGF drugs at different time points in the past, the central retinal thickness decreased by less than 10% and the absolute value was greater than 300 μm compared to the baseline, or the best corrected visual acuity (BCVA) ≤ 20/40 Snellen equivalent (≈54 ETDRS letters) compared to the baseline. Exclusion criteria: eye infection, history of intraocular surgery within 6 months prior to enrollment (except for uncomplicated cataract surgery >3 months earlier), allergy to test drugs, severe heart, liver, and kidney dysfunction, etc. According to the preliminary experimental data and statistical requirements, the required sample size was calculated. The patients were divided into a combination group (TA + BEV) and a control group (TA) by the random number table method, with 40 cases in each group. Sample size was calculated based on an expected 7-letter BCVA difference (SD=10) from a pilot study. Using α=0.05 and 80% power (β=0.2), 33 eyes per group were required. Accounting for a 20% dropout, 40 eyes per group were enrolled.
Intervention
In the control group, 0.1ml TA injection (4mg/0.1 ml) was injected into the intraocular vitreous cavity. The patients in the combination group received intravitreal injection treatment. They received 1.25mg BEV (0.05ml) followed by 2mg TA (0.05ml) at a different quadrant after 5-minute intraocular pressure monitoring. All patients received levofloxacin spot surgery 24 hours before surgery, 5 times/day. One day before the operation, the eye was prepared according to the routine of eye surgery, the conjunctival sac was rinsed, and the eye surface anesthesia was given. The eyelid was opened with a lid opening device, and the drug was injected through a puncture 4 mm behind the lower temporal corneum. All patients received a loading dose injection once a month for a total of three consecutive times.
Main Observation Measures
Parameters such as blood flow velocity of OA, CRA, NPCA, and TPCA were measured by color Doppler ultrasound before treatment and at 1 week, 1 month, and 3 months after treatment. The aqueous humor samples of patients were collected before and after treatment, and the concentrations of VEGF, IL-6, and NOS were detected by ELISA.
Secondary Observation Measures
BCVA assessed by the ETDRS chart (converted to LogMAR) was used to detect the BCVA before and after treatment. The retinal thickness of the two groups before and after treatment was measured by optical coherence tomography. Any ocular and systemic adverse reactions during treatment were recorded.
Statistical Analysis
SPSS 18.0 software was used for statistical analysis. Measurement data were expressed as mean ± standard deviation, and comparison between groups was performed by t-test or analysis of variance. Count data were expressed as frequency or percentage. A p-value less than 0.05 was considered statistically significant.
Ethical Approval
This study was approved by the Ethics Committee of Shijiazhuang Aier Eye Hospital (Date: 2024-09-09, No: 2400089443).

Results

Baseline Characteristics
No significant intergroup differences were observed in gender distribution, age, or disease duration (p > 0.05 for all comparisons), indicating balanced baseline parameters between the control and combination groups.
Ocular Blood Flow Parameters
There was no significant difference in the baseline PSV of the ophthalmic artery (OA) between the two groups (p = 0.963).
After 3 months of treatment, the PSV in both groups increased significantly (p < 0.001), with a greater increase in the combined group (TA + BEV) (3 months: 34.66 ± 1.26 cm/s, an increase of 29.37% from the baseline; the control group only increased by 7.81%). The effect size (η2= 0.96) in the combined group was higher than that in the control group (η2=0.88). In terms of the central retinal artery (CRA), the combined group had a greater increase in PSV at 3 months (+59.59% vs +40.99%), and the difference between the groups expanded over time (d = 1.87). The combination of the two drugs could synergistically reduce the resistance index of CRA and increase PSV (combined group +1.56 cm/s vs control group +0.73 cm/s), and the difference in growth rate (0.46 cm/s/month, p < 0.001) reflected the remodeling of microcirculation structure. The PSV increase in the NPCA (nasal choroidal quadrant artery) combined treatment group reached 76.08% at 3 months, significantly higher than that in the control group (31.98%). The maximum difference between the two groups occurred at 3 months (13.84 cm/s vs 9.91 cm/s, d = 6.65), and the growth rate was also significantly superior (2.00 cm/s/month vs 0.82 cm/s/month). The PSV increase in the TPCA (major choroidal artery) combined group (+8.86 cm/s) was significantly higher than that in the control group (+4.01 cm/s), with an intergroup difference of 4.96 cm/s at 3 months (d = 8.44). VEGF, NOS and IL-6.
The levels of VEGF in both groups decreased significantly over time (p < 0.001), and the decline was more pronounced in the combined group (at 3 months: -57.83% vs -38.63%). The difference between the groups expanded over time (d = 4.09). At 3 months, the VEGF level in the combined group was 93.01 pg/mL, significantly lower than that of the control group; its decline rate was also greater (42.71 vs 27.58 pg/mL/month). The levels of NOS in both groups increased significantly over time (p < 0.001), and the increase was greater in the combined group (at 3 months: +198.53% vs +70.70%). The difference between the groups continued to expand (d = 5.90), with the maximum difference occurring at 3 months (109.28 vs 62.48 U/ mL). The growth rate of the combined group was higher (24.01 vs 8.59 U/mL/month). The combined treatment blocked the positive feedback of VEGF-IL-6 with BEV and directly inhibited IL-6 transcription with triamcinolone acetonide, achieving synergistic anti-inflammatory effects. The difference between the groups reached 12.98 pg/mL at 3 months (p < 0.001, d = 3.94), and the inhibitory effect increased over time (slope difference = 4.0 pg/mL/month).
BCVA and Retinal Thickness
The vision of the combined group improved by 0.159 LogMAR (approximately 8.0 ETDRS letters) in 3 months, significantly higher than the 0.102 LogMAR (approximately 5.1 letters) of the control group. The net benefit between the two groups reached 2.9 letters (p < 0.001). The improvement rate of the combined group was 0.053 LogMAR per month, also significantly better than that of the control group (0.034 LogMAR per month). The combined group reached a clinically significant vision improvement threshold (a decrease of 0.094 LogMAR, approximately 1.5 lines) within 1 month. In terms of anatomical structure, the CMT of the combined group decreased by 171.2 μm (a reduction of 35.55%) within 3 months, much higher than that of the control group (43.5 μm, a reduction of 7.67%), with a rate of 56.9 μm per month, significantly faster than that of the control group (14.5 μm per month).
Adverse Reactions
As shown in Table 3, there was no statistically significant difference in all adverse reactions among the groups (p > 0.05).
In the control group, 2 patients simultaneously experienced corneal edema and elevated intraocular pressure. In the combined group, there were no combined adverse events, and the difference between the groups was p = 0.494, which was not statistically significant. The VEGF inhibitor may activate the complement pathway, causing the disruption of the blood-aqueous barrier and the formation of anterior chamber inflammation. The anti-inflammatory effect of TA counteracted the potential inflammatory effect of BEV. The combined treatment maintained the therapeutic advantage while not significantly increasing the overall risk of adverse reactions (27.5% vs 17.5%, p = 0.304). The trend of a 67% reduction in the rate of elevated intraocular pressure (7.5%→2.5%) reflects the pharmacokinetic synergistic effect - BEV shortens the half-life of TA and reduces the cumulative exposure to glucocorticoids. The incidence of corneal edema decreased (12.5% → 5.0%) and was directly related to the reduction in TA dose (4mg → 2mg), confirming the dose-dependent toxicity mechanism.

Discussion

The combined treatment promotes microvascular reconstruction through VEGF inhibition and anti-inflammatory effects, enhances NPCA perfusion, and exhibits a time cumulative effect (slope difference = 1.18 cm/s/month), indicating continuous microvascular repair. BEV dilates the choroidal small arteries, while triamcinolone acetonide reduces inflammatory infiltration and maintains capillary integrity. Together, they promote the coupling of TPCA and CRA, improving retinal-corneal circulation. Additionally, BEV improves oxidative stress and restores eNOS function, while triamcinolone acetonide inhibits inflammation and downregulates iNOS. The dual regulation significantly enhances protective NOS levels, with a group difference of 46.80 U/mL (p < 0.001) confirming its substantial improvement in vascular endothelial function. In terms of vision, the combined treatment synergistically promotes visual function improvement through three mechanisms: blood flow improvement, VEGF inhibition, and anti-inflammatory repair. The group difference reaches its peak at 3 months (0.053 LogMAR), and visual improvement is significantly correlated with blood flow, VEGF, and IL-6, supporting the necessity of multi-target intervention.

Limitations

This study also has some limitations: The 3-month follow- up period may not be sufficient to assess long-term efficacy (such as TA-related high intraocular pressure); the TA dose in the combined group (2mg) is lower than that in the single- drug group (4mg), BEV would be able to produce synergistic effects with TA by blocking VEGF and inhibiting inflammation, respectively, allowing a reduction in TA dose. In the future, a large sample size is needed to verify the optimal TA dose, and the follow-up period should be extended to more than 12 months to verify the persistence of the positive trends observed in this study and to monitor for any potential long-term adverse events. Researchers should strive to expand the sample size to more comprehensively evaluate the long-term effects of TA combined with BEV on ocular hemodynamics and VEGF levels in patients with refractory DME.

Conclusion

This randomized controlled trial demonstrates that intravitreal co-administration of triamcinolone acetonide (TA, 2mg) and BEV (1.25mg) confers significant therapeutic advantages over TA monotherapy (4mg) in refractory DME, addressing multiple pathological pathways through synergistic mechanisms. VEGF blockade rapidly normalized vascular tone, while TA attenuated pericyte loss and endothelial inflammation, reducing microcirculatory resistance. BEV directly neutralized VEGF, while TA inhibited NF-κB-mediated cytokine transcription, breaking the “VEGF-inflammation-ischemia” vicious cycle. The combined treatment not only significantly improved the blood flow parameters of the ophthalmic artery, reduced the levels of VEGF and IL-6, but also brought obvious benefits in terms of anatomical structure and function, including a decrease in the thickness of the central retina and an improvement in the best corrected visual acuity. Therefore, the combined application of TA and BEV provides a mechanismally complementary and therapeutically synergistic treatment strategy for refractory DME, with significant clinical application prospects.

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