Evelien Vandewalle

Use of colour Doppler imaging in ocular blood flow research.

The main objective of this report is to encourage consistent quality of testing and reporting within and between centres that use colour Doppler imaging (CDI) for assessment of retrobulbar blood flow. The intention of this review is to standardize methods in CDI assessment that are used widely, but not to exclude other approaches or additional tests that individual laboratories may choose or continue to use.

Oximetry in glaucoma: correlation of metabolic change with structural and functional damage

Purpose:  To determine whether retinal vessel oxygen saturation in patients with glaucoma is associated with structural optic disc and retinal nerve fibre layer (RNFL) changes and visual field (VF) defects.

The role of different VEGF isoforms in scar formation after glaucoma filtration surgery.

Vascular endothelial growth factor (VEGF) plays an important role in both physiological and pathological angiogenesis. Our previous studies showed a differential role of VEGF isoforms in retinal physiological angiogenesis. We also demonstrated that non-selective inhibition of VEGF by bevacizumab had a beneficial effect on surgical outcome after glaucoma filtration surgery by reducing angiogenesis as well as fibrosis. However, the function of the VEGF isoforms in pathological angiogenesis and wound healing in the eye still remains unidentified. This study was designed to elucidate the differential roles of VEGF isoforms in scar formation after trabeculectomy. Furthermore, we also investigated whether pegaptanib (Macugen™, Pfizer), an aptamer which specifically blocks VEGF(165), could improve surgical outcome by reducing postoperative scarring. VEGF-R2 and neuropilin-1 (NRP-1) expression was analyzed in vitro by RT-PCR, and were found to be expressed at higher levels in human umbilical vein endothelial cells (HUVEC) as compared to Tenon fibroblasts (TF). The effect of the different VEGF isoforms (VEGF(121), VEGF(165) and VEGF(189)) and pegaptanib on cell proliferation was determined via WST-1 assay. Endothelial cell proliferation was stimulated after addition of VEGF(121) and VEGF(165), whereas VEGF(121) and VEGF(189) increased fibroblast growth. These effects on proliferation were associated with an activation of the ERK pathway, as revealed using the TransAM c-Myc assay. Inhibition of the ERK pathway, by PD98059 administration, significantly reduced VEGF isoform induced cell growth. A dose-dependent reduction of endothelial cell proliferation was observed after pegaptanib administration, while only the highest dose was able to inhibit fibroblast growth. Next, the in vivo effect of pegaptanib was investigated in a rabbit model of trabeculectomy. The surgical outcome was evaluated by performing clinical investigations (IOP, bleb area, height and survival), as well as histomorphometric analyses of angiogenesis (CD31), inflammation (CD45) and fibrosis (Sirius Red). A single postoperative application of pegaptanib had a beneficial impact on surgical outcome, mainly by reducing angiogenesis, but not inflammation or collagen deposition. Repeated injections slightly improved surgical outcome, but again solely by reducing angiogenesis. In summary, our results revealed that the VEGF isoforms play a differential role in ocular wound healing: VEGF(165) and VEGF(121) predominantly affect blood vessel growth, whereas VEGF(189) is rather involved in fibrosis, an important process in wound healing.

Retinal oxygen metabolism in healthy subjects and glaucoma patients

Background To test whether retinal oxygen metabolism is different in glaucoma patients compared with healthy subjects. Methods This was a two-centre study where retinal vessel oxygen saturation was measured in glaucoma patients and healthy individuals with a non-invasive spectrophotometric retinal oximeter. Visual fields were obtained in the glaucoma patients. Results No statistical difference was found in retinal oxygen saturation in arterioles (p=0.16), venules (p=0.16) and arteriovenous difference (p=0.24) when all glaucoma patients (n=74) were compared with healthy individuals (n=89). When patients with advanced glaucoma (visual field mean defect (MD ≥ 10 dB, n=21)) were compared with healthy individuals, the oxygen saturation in venules was higher in glaucoma patients (58.2%±5.4% vs 53.8%±6.4%; p=0.0054, mean±SD) and the arteriovenous difference was lower in glaucoma patients (36.4%±4.7% vs 39.5%±5.7%; p=0.021). In glaucoma patients with mild glaucoma (visual field MD ≤ 5 dB, n=33), no statistical differences were found in retinal oxygen saturation compared with healthy individuals. Conclusions Glaucoma patients with advanced glaucoma have higher oxygen saturation in venules and lower arteriovenous difference in oxygen saturation compared with healthy individuals. The decreased arteriovenous difference in severe glaucoma may be related to lower oxygen consumption secondary to neuropathy.

AMA0076, a Novel, Locally Acting Rho Kinase Inhibitor, Potently Lowers Intraocular Pressure in New Zealand White Rabbits with Minimal Hyperemia

PURPOSE To determine whether ROCK inhibition for the treatment of glaucoma can be improved by using novel, locally acting Rho kinase (ROCK) inhibitors, such as AMA0076, that lower IOP without inducing hyperemia. METHODS On-target potency of AMA0076 was compared with other ROCK inhibitors (Y-27632 and Y-39983) and conversion of AMA0076 into its functionally inactive metabolite was evaluated in rabbit eye tissues. Human trabecular meshwork (HTM) cell morphology, actin filaments, and focal adhesion were studied in vitro after exposure to AMA0076. The effect of AMA0076 on IOP was investigated in normotensive rabbits and a new, acute hypertensive rabbit model. Intraocular pressure lowering efficacy of AMA0076 was compared with pharmacologic treatments. Hyperemia after single topical dosing of AMA0076 and Y-39983 was scored. RESULTS AMA0076 and Y-39983 showed similar on-target potency. AMA0076 was most stable in aqueous humor and converted into its metabolite in other eye tissues. Exposure of HTM cells to AMA0076 led to significant and reversible changes in cell shape and a decrease in actin stress fibers and focal adhesions. Both AMA0076 and Y-39983 provided an equivalent IOP control. Compared with latanoprost and bimatoprost, AMA0076 was more potent in preventing the IOP elevation in the acute hypertensive rabbit model. The degree of hyperemia was significantly lower in rabbits treated with AMA0076 then with Y-39983. CONCLUSIONS AMA0076 is a locally acting ROCK inhibitor that is able to induce altered cellular behavior of HTM cells. Administration of AMA0076 effectively reduces IOP in ocular normotensive and acute hypertensive rabbits without causing distinct hyperemia.

Intracameral bevacizumab as an adjunct to trabeculectomy: a 1-year prospective, randomised study

Aims To investigate the efficacy and safety of a single intracameral bevacizumab injection to improve the outcome of trabeculectomy. Methods A 12-month, prospective, randomised, double-masked, placebo-controlled trial. Patients with medically uncontrolled open-angle glaucoma scheduled for a primary trabeculectomy were recruited and randomised to receive 50 µL of either bevacizumab (1.25 mg) or placebo (balanced salt solution) peroperatively. Absolute success was defined as intraocular pressure (IOP) ≤18 mm Hg and >5 mm Hg with at least 30% reduction from baseline and no loss of light perception. Success through the use of additional medical and/or surgical IOP-lowering treatments was defined as qualified success. Results 138 patients completed a 12-month follow-up, 69 of whom were in the bevacizumab treated group. IOP at 1 year postoperatively was significantly lower than baseline (placebo: 25.6±9.9 mm Hg vs 11.5±3.9 mm Hg, p<0.01; bevacizumab: 24.8±8.1 mm Hg vs 11.9±3.8 mm Hg, p<0.01), with no difference between treatment groups (p=0.69). However, absolute success was higher in the bevacizumab group (71% vs 51%, p=0.02), with the need for IOP-lowering interventions (needlings) being lower in this group (12% vs 33%, p=0.003). Complication rates were low and comparable between groups. Conclusions Peroperative administration of intracameral bevacizumab significantly reduces the need for additional interventions during the follow-up of patients undergoing trabeculectomy.

Ocular blood flow in glaucoma – the Leuven Eye Study

Elevated intra‐ocular pressure (IOP) has been identified as a major risk factor for glaucoma. Additionally, extensive literature depicts a vascular dysfunction to exist in these patients. However, a large ocular blood flow‐oriented trial to integrate these findings in the clinical setting is lacking. This study would likely help to identify which of these vascular data can be used as a clinical tool for screening and disease stratification.

Lack of spontaneous venous pulsation: possible risk indicator in normal tension glaucoma?

Purpose:  Recently, the absence of spontaneous venous pulsation (SVP) has been suggested as a vascular risk factor for primary open‐angle glaucoma (POAG). As the mechanism behind this phenomenon is still unknown, the authors have studied this vascular component using colour Doppler imaging (CDI).

The Role of LOX and LOXL2 in Scar Formation After Glaucoma Surgery

PURPOSE The aim of this study was to elucidate the role of lysyl oxidase (LOX) and lysyl oxidase like (LOXL) 2 in pathologic wound healing after glaucoma surgery. We therefore investigated the expression of LOX and LOXL2 and evaluated the therapeutic potential of anti-LOX (GS-639556, formerly M64) and anti-LOXL2 (GS-607601, formerly AB0023) antibodies in a rabbit model of glaucoma trabeculectomy. METHODS Ocular expression of LOX and LOXL2 was investigated by immunohistologic staining at different time points after trabeculectomy. Treatment with GS-639556 or GS-607601 was initiated in rabbits immediately after trabeculectomy by giving both intracameral and subconjunctival injections. Thereafter, the antibodies were given twice a week subconjunctivally until day 30 after surgery (day of euthanization). Treatment outcome was studied by clinical investigation of the bleb and by immunohistochemical analysis of angiogenesis, inflammation, and collagen deposition. RESULTS LOX and LOXL2 were both upregulated in Tenons capsule and the conjunctiva after glaucoma surgery. Repeated administration of LOX- or LOXL2-targeting monoclonal antibodies increased bleb area and bleb survival. Analyses of immunohistologic stainings showed that both antibodies significantly decreased fibrosis, whereas the anti-LOXL2 antibody also significantly reduced blood vessel density and inflammation. CONCLUSIONS Targeting LOXL2 with an inhibitory monoclonal antibody (GS-607601) reduced pathologic angiogenesis, inflammation, and fibrosis. These results suggest that LOXL2 could be an appealing target for treatment of scar formation after glaucoma surgery, and point to the potential therapeutic benefits of simtuzumab, a humanized monoclonal antibody derived from GS-607601.

Phenylephrine 5% added to Tropicamide 0.5% eye drops does not influence retinal oxygen saturation values or retinal vessel diameter in glaucoma patients

Purpose:  To test whether adding topical phenylephrine 5% to tropicamide 0.5% eye drops in the protocol for pupil dilation affects the retinal vessel oximeter measurements in patients with glaucoma. To test whether phenylephrine 5% has an influence as a vasoconstrictor on the retinal vessel width and can improve the proportion of high‐quality retinal images in patients with glaucoma.