Arteriovenous adventitial sheathotomy for branch retinal vein occlusion: report of a case with longterm follow-up

Branch retinal vein occlusion: treatment modalities: an update of the literature

BACKGROUND

Retinal vein occlusion is the second most common retinal vascular disorder after diabetic retinopathy and is considered to be an important cause of visual loss. In this review, our purpose is to update the literature about the treatment alternatives for branch retinal vein occlusion.

METHODS

Eligible papers were identified by a comprehensive literature search of PubMed, using the terms "branch retinal vein occlusion," "therapy," "intervention," "treatment," "vitrectomy," "sheathotomy," "laser," "anti-VEGF," "pegaptanib," "bevacizumab," "ranibizumab," "triamcinolone," "dexamethasone," "corticosteroids," "non-steroids," "diclofenac," "hemodilution," "fibrinolysis," "tPA," and "BRVO." Additional papers were also selected from reference lists of papers identified by the electronic database search.

RESULTS

Treatment modalities were analyzed.

CONCLUSIONS

There are several treatment modalities for branch retinal vein occlusion and specifically for its complications, such as macular edema, vitreous hemorrhage, retinal neovascularization, and retinal detachment, including anti-aggregative therapy and fibrinolysis, isovolemic hemodilution, vitrectomy with or without sheathotomy, peripheral scatter and macular grid retinal laser therapy, non-steroid agents, intravitreal steroids, and intravitreal anti-vascular endothelial growth factors (anti-VEGFs).

Macular microcirculation in hypertensive patients with and without branch retinal vein occlusion

PURPOSE

Our purpose was to determine whether a reduction in blood flow velocity (BFV) in the perifoveal capillaries is involved in the pathogenesis of branch retinal vein occlusion (BRVO) in patients with hypertension.

METHODS

Subjects included hypertensive patients with (n = 12) and without (n = 16) BRVO and healthy volunteers (n = 16). Perifoveal BFV was measured by the tracing method using fluorescein angiography and a scanning laser ophthalmoscope. Logistic regression analysis was performed to assess factors that influenced the presence or absence of BRVO.

RESULTS

Mean BFV showed a significant decrease across the three groups (healthy controls: 1.49 +/- 0.11 mm/second; hypertensive patients without BRVO: 1.36 +/- 0.12 mm/second; hypertensive patients with BRVO: 1.16 +/- 0.24 mm/second; p(trend) < 0.001). Multivariate logistic regression analysis showed that BFV was a significant risk factor for the presence of BRVO.

CONCLUSIONS

Perifoveal capillary BFV is reduced in hypertensive patients with and without BRVO. It is possible that a decrease in BFV may be involved in the occurrence of BRVO. Measurement of perifoveal capillary BFV may be useful for investigating the pathogenesis and progression of BRVO.

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.

Sheathotomy in complicated cases of branch retinal vein occlusion

PURPOSE

To report the clinical experience and results of using a microsurgical technique to decompress the arteriovenous connection in complicated branch retinal vein occlusion (BRVO) combined with haemorrhage, oedema and ischaemia.

METHODS

We carried out a retrospective, non-randomized, interventional case study of the surgical sheathotomy decompression procedure. We enrolled 12 patients (seven women, five men; median age 64 years) with BRVO and decreased visual acuity (VA) caused by haemorrhage, oedema and ischaemia. The mean duration of thrombosis was 7 months (2-15 months). The patients were examined for pre- and postoperative best corrected VA (BCVA), intraocular pressure (IOP) and fundus photography. Ten patients were examined with fluorescein angiography and eight with ocular coherence tomography (OCT). Postoperative progression of cataract was recorded, as were other complications. The mean follow-up time was 20 months (8-39 months).

RESULTS

Best corrected VA had improved in nine patients, was unchanged in one patient and had deteriorated in two patients at the last follow-up. Noted complications were venous haemorrhage at surgery in five patients, retinal detachment in one patient and progression of cataract in four patients.

CONCLUSIONS

Microsurgical treatment with sheathotomy of BRVO is a technically feasible procedure with few complications. Postoperative increased reperfusion could explain the resolution of macular haemorrhage, oedema and ischaemia, and may improve visual function in patients with this common vascular eye disease.