Effects of repeated injection of intravitreal triamcinolone on macular oedema in central retinal vein occlusion

[From scientific evidence to clinical practice: treatment regimens for macular edema secondary to retinal vein occlusion]

Retinal vein occlusion (RVO) is the second most common cause of retinal vascular disease after diabetic retinopathy. Despite the existence of several possible treatment options, none was entirely satisfactory and many patients suffered irreversible visual loss. As a result of the BRAVO, CRUISE and GENEVA trials, ranibizumab and the intravitreal biodegradable implants of dexamethasone has recently been approved by the US Food and Drug Administration and the European Medicines Agency for the treatment of RVO secondary edema. In this paper we begin by describing the current treatment options for RVO associated macular edema and continue with the description of the treatment regimen with ranibizumab.

Combination therapy in diabetic macular oedema and retinal vein occlusion--past and present

This paper summarizes the recent evidence for combined therapies in the intravitreal medical treatment of diabetic macular oedema or macular oedema, secondary to retinal vein occlusion. Since the introduction of anti-inflammatory or anti-VEGF drugs combined with or used alternatively to laser, visual acuity can be stabilized or improved in a significant number of patients. However, there is an ongoing debate regarding the safety, efficiency and economic concerns related to these intravitreal monotherapies because they warrant frequent repetition to maintain the clinical effect. In the literature, the combination of photolasercoagulation, intravitreal steroids or VEGF-inhibitors, or both, shows early compelling evidence that some patients may benefit from less retreatment compared to monotherapy. To provide a conceptual and perspective approach for a first-line combined therapy, this paper also summarizes own results of pilot interventional case series of a 1.5 cc core pars plana vitrectomy and intravitreal substitution with balanced salt solution (BSS), 1.25 mg bevacizumab and 8 mg triamcinolone.

Effects of intravitreal triamcinolone acetonide on retinal gene expression in a rat model of central retinal vein occlusion

PURPOSE

The aim of this study was to investigate the effects of intravitreal triamcinolone acetonide on the alterations in retinal gene expression in a rat model of central retinal vein occlusion (CRVO).

METHODS

In one eye of adult Brown Norway rats (n = 77) CRVO was induced with laser photocoagulation of all retinal veins near to the optic disk after intraperitoneal injection of 0.2 ml of 10% sodium fluorescein. The gene expression was investigated using RT-PCR separately in the neural retina and retinal pigment epithelium (RPE) 1, 3, 7, and 14 days after CRVO induction. We analyzed the expression of factors that influence the development of vascular edema (VEGF-A, VEGF-B, PEDF), of channels implicated in retinal osmohomeostasis (Kir4.1, AQP4, AQP1), and of the pro-inflammatory factors IL-1ß and IL-6.

RESULTS

CRVO induced a rapid transient upregulation of Vegfa, a downregulation of Vegfb, and a delayed upregulation of Pedf in the neuroretina. In the neuroretina and retinal pigment epithelium, CRVO induced strong, transient downregulation of Kir4.1, Aqp4, and Aqp1, and striking rapid upregulation of Il1ß and Il6. Intravitreal triamcinolone reversed the downregulation of Kir4.1 and accelerated the normalization of the upregulated expression of Il1ß and Il6. The CRVO-induced transient upregulation of Vegfa was not influenced by the triamcinolone application.

CONCLUSIONS

Triamcinolone exerts anti-inflammatory effects in the ischemic retina by inhibitory effects on the gene expression of IL-1ß and IL-6, and may have neuroprotective effects via improvement of retinal potassium homeostasis.

Does lens status affect the course of early intraocular pressure and anterior chamber changes after intravitreal injection?

PURPOSE

This study aimed to observe changes in anterior chamber parameters and the course of intraocular pressure (IOP) after injection of 0.1 ml intravitreal triamcinolone acetonide (TA) and to determine differences between phakic and pseudophakic eyes without vitreous reflux.

METHODS

A prospective observational clinical trial was conducted with 89 patients who received an intravitreal injection of TA and did not display vitreous reflux. Intraocular pressure measurements were made before injection and at 3, 10, 20, 30 and 40 mins after injection. Pentacam measurements were made before injection and at 5, 15, 30 and 45 mins after injection.

RESULTS

Anterior chamber depth (ACD) and anterior chamber volume (ACV) were significantly greater in pseudophakic eyes than in phakic eyes at all measurement time-points (p < 0.001). There was a decrease in both ACD and ACV at 5 mins after injection, and a gradual increase to normal values was observed at 15, 30 and 45 mins after injection in all study eyes. Compared with pre-injection measurements, changes in ACD and ACV were statistically significant at each time-point in both phakic and pseudophakic eyes (p < 0.001). A significant increase in IOP within 3 mins of injection was observed in both groups and a more rapid decrease 10 mins after injection was observed in pseudophakic eyes. The differences in IOP between phakic and pseudophakic eyes at all measurement time-points, except baseline and 3 mins after injection, were statistically significant (p < 0.001). Intraocular pressure < 30 mmHg and < 24 mmHg was recorded in all pseudophakic eyes at 10 and 20 mins after intravitreal injection, respectively.

CONCLUSIONS

Following intravitreal injection of 0.1 ml TA, without vitreous reflux, IOP decreased to safe levels more quickly in pseudophakic eyes than in phakic eyes. Although there were more pronounced changes in anterior chamber parameters in pseudophakic eyes, these changes were reversible without any residual clinical significance.

Visual improvement in central retinal vein occlusion (CRVO) following intravitreal injections of bevacizumab (Avastin(®) )

PURPOSE

To perform a prospective study on central retinal vein occlusion (CRVO) to evaluate whether visual acuity can be improved and macular oedema reduced in response to intravitreal injections of bevacizumab.

METHODS

The case material comprised 13 patients (aged 34-79 years), duration of CRVO was 2 weeks to 6 months, baseline ETDRS visual acuity 0.06-0.4 (mean Snellen 0.13, derived from logMAR value) and intraocular pressure (IOP) 12-20 (mean 15.2) mmHg. Clinical examination, including optical coherence tomography (OCT), was carried out at baseline and every 6 weeks, digital fluorescein angiography at baseline, at 3 months and 6 months. Intravitreal injections of bevacizumab (1.25 mg) were given under microscopic control at baseline and every 6 weeks during the 6-month follow-up.

RESULTS

Following one intravitreal injection of bevacizumab, average visual acuity improved by 13 ETDRS letters at 1 month (p < 0.05) and in response to 4 injections by 24 letters (logMAR 0.48) at 6 months (p < 0.05). Foveal thickness as measured by OCT decreased from 596 μm at baseline to 288 μm at 6 months (p < 0.05) concomitant with resorption of intra- and subretinal fluid. IOP ranged from 10 to 24 (17.3) mmHg at 6-month follow-up. No adverse events occurred.

CONCLUSIONS

  In response to four intravitreal injections of bevacizumab during 6 months, a substantial improvement in visual acuity and reduction in central retinal thickness were achieved. A randomized clinical trial is warranted to further evaluate the efficacy and safety of this treatment modality.

[SERV clinical practice guidelines: management of retinal vein occlusion. Sociedad Española de Retina y Vitreo]

PURPOSE

A guidelines for the management of retinal vein occlusion is presented. This is necessary because at this moment several therapeutic alternatives have been developed although their role is not yet sufficiently defined.

METHODS

Review of the literature for evidence published up to date. Relevant literature was identified and the level of evidence graded. Evidence was then assessed for consistency, applicability and clinical impact. The information was contrasted with those guides published in other countries.

RESULTS

Taking into account the different options of treatment that are currently used, several modes of action are suggested. The role of the various complementary examinations are discussed and it is recommended that criteria for the treatment are based on clinical, angiographic, and tomographic findings.

CONCLUSIONS

Although there is no overall consensus, these guidelines promote a good standard of clinical practise and provide an update of the management of retinal vein occlusion.

Increase of vascular endothelial growth factor and interleukin-6 in the aqueous humour of patients with macular oedema and central retinal vein occlusion

PURPOSE

This study aimed to investigate whether vascular endothelial growth factor (VEGF) or interleukin-6 (IL-6) influence macular oedema in patients with central retinal vein occlusion (CRVO).

METHODS

Sixteen consecutive patients with unilateral CRVO and macular oedema were studied, along with eight age- and sex-matched patients without ischaemic ocular disease. Retinal ischaemia was evaluated from capillary non-perfusion on fluorescein angiography. Macular oedema was examined by optical coherence tomography. Aqueous humour (AH) samples were obtained during combined pars plana vitrectomy and cataract surgery, and were examined by enzyme-linked immunosorbent assay.

RESULTS

Aqueous levels of VEGF and IL-6 were significantly elevated in patients compared with controls (p=0.0142 and p<0.0001, respectively). Aqueous levels of both molecules were significantly higher in patients with ischaemia than in those without ischaemia (p=0.0026 and p=0.0487, respectively). Furthermore, AH levels of VEGF and IL-6 were correlated with the severity of macular oedema (ρ=0.7265, p=0.0049, ρ=0.5324, and p=0.0392, respectively).

CONCLUSIONS

  Both VEGF and IL-6 were elevated in the AH of patients with macular oedema and ischaemic CRVO, suggesting that these molecules may be related to the increase in vascular permeability in such patients.

Diabetic macular edema

A variety of treatment options are available for the treatment of diabetic macular edema. They include laser photocoagulation, anti-VEGF drugs, intravitreal steroids, and vitrectomy with or without release of vitreoretinal traction. A full understanding of the physiological mechanisms of these treatment modalities allows sensible combination of treatment options. Retinal photocoagulation has repeatedly been shown to improve retinal oxygenation, as does vitrectomy. Oxygen naturally reduces VEGF production and thereby decreases leakage of plasma proteins from capillaries into the tissue. In addition, vitrectomy allows faster clearance of cytokines, such as VEGF, from the retina into the vitreous cavity. The VEGF-lowering effect of photocoagulation and vitrectomy can be augmented with anti-VEGF drugs and corticosteroids reduce the effect of VEGF on capillary permeability. Starling's law explains vasogenic edema, which is controlled by osmotic and hydrostatic gradients between vessel and tissue. It explains how VEGF-induced vascular permeability causes plasma protein to leak into the tissue interstitial space, thus decreasing the osmotic pressure gradient between vessel and tissue, resulting in water accumulation, i.e. edema. This is reversed by reducing VEGF production, which is achieved with laser treatment; or by removing VEGF with antibodies or vitrectomy; or by reducing the permeability effect with steroids. At the same time, Starling's law takes into account hemodynamic changes that affect the hydrostatic gradient. High arterial blood pressure and hypoxic vasodilatation increase the hydrostatic pressure in the microcirculation, which increases water flux from vessel to tissue and induce edema. Treatment of arterial hypertension or reversal of retinal hypoxia with laser reverses this pathophysiology and reduces edema. Newton's third law explains, that vitreoretinal traction decreases hydrostatic tissue pressure in the retina, increases the pressure gradient between vessel and tissue, and stimulates water fluxes from vessel into tissue, leading to edema. Release of vitreoretinal traction reverses this mechanism and reduces edema.

Physiology of vitreous surgery

Vitreous surgery has various physiological and clinical consequences, both beneficial and harmful. Vitrectomy reduces the risk of retinal neovascularization, while increasing the risk of iris neovascularization, reduces macular edema and stimulates cataract formation. These clinical consequences may be understood with the help of classical laws of physics and physiology. The laws of Fick, Stokes-Einstein and Hagen-Poiseuille state that molecular transport by diffusion or convection is inversely related to the viscosity of the medium. When the vitreous gel is replaced with less viscous saline, the transport of all molecules, including oxygen and cytokines, is facilitated. Oxygen transport to ischemic retinal areas is improved, as is clearance of VEGF and other cytokines from these areas, thus reducing edema and neovascularization. At the same time, oxygen is transported faster down a concentration gradient from the anterior to the posterior segment, while VEGF moves in the opposite direction, making the anterior segment less oxygenated and with more VEGF, stimulating iris neovascularization. Silicone oil is the exception that proves the rule: it is more viscous than vitreous humour, re-establishes the transport barrier to oxygen and VEGF, and reduces the risk for iris neovascularization in the vitrectomized-lentectomized eye. Modern vitreous surgery involves a variety of treatment options in addition to vitrectomy itself, such as photocoagulation, anti-VEGF drugs, intravitreal steroids and release of vitreoretinal traction. A full understanding of these treatment modalities allows sensible combination of treatment options. Retinal photocoagulation has repeatedly been shown to improve retinal oxygenation, as does vitrectomy. Oxygen naturally reduces VEGF production and improves retinal hemodynamics. The VEGF-lowering effect of photocoagulation and vitrectomy can be augmented with anti-VEGF drugs and the permeability effect of VEGF reduced with corticosteroids. Starling's law explains vasogenic edema, which is controlled by osmotic and hydrostatic gradients between vessel and tissue. It explains the effect of VEGF-induced vascular permeability changes on plasma protein leakage and the osmotic gradient between vessel and tissue. At the same time, it takes into account hemodynamic changes that affect the hydrostatic gradient. This includes the influence of arterial blood pressure, and the effect oxygen (laser treatment) has in constricting retinal arterioles, increasing their resistance, and thus reducing the hydrostatic pressure in the microcirculation. Reduced capillary hydrostatic pressure and increased osmotic gradient reduce water fluxes from vessel to tissue and reduce edema. Finally, Newton's third law explains that vitreoretinal traction decreases hydrostatic tissue pressure in the retina, increases the pressure gradient between vessel and tissue, and stimulates water fluxes from vessel into tissue, leading to edema.