Implications of bevacizumab on vascular endothelial growth factor and endostatin in human choroidal neovascularisation

AIM

To evaluate the implications of intravitreal bevacizumab on proangiogenic vascular endothelial growth factor (VEGF) with regard to the endogenous angiogenesis inhibitor endostatin in human choroidal neovascularisation (CNV) secondary to age-related macular degeneration.

METHODS

Retrospective review of an interventional case series of 48 patients who underwent full macular translocation surgery with removal of CNV. Twenty-five patients were treated with intravitreal bevacizumab injection 1 to 154 days prior to surgery (bevacizumab CNV). Twenty-three CNV without any kind of previous treatment were used as controls (control CNV). CNV were stained for CD34, cytokeratin18, VEGF, endostatin and E-selectin. A "predominance score of VEGF over endostatin" (PS) was defined by the difference between VEGF and endostatin staining scores.

RESULTS

Bevacizumab CNV revealed a weaker VEGF expression in endothelial cells (p = 0.0245) but significantly more intense endostatin in retina pigment epithelium (RPE) (p = 0.0001) and stroma (p<0.0001). Consequently, PS was significantly lower in RPE (p = 0.02), vessels (p = 0.03) and stroma (p = 0.0004) in bevacizumab CNV. The intensity of E-selectin expression in bevacizumab CNV was comparable with that in control CNV.

CONCLUSIONS

A shift within the angiogenic balance in terms of decreased VEGF predominance over endostatin is detected in human CNV treated with bevacizumab.

Extraocular surgery for implantation of an active subretinal visual prosthesis with external connections: feasibility and outcome in seven patients

BACKGROUND

Due to low energy levels in microphotodiode-based subretinal visual prostheses, an external power supply is mandatory. We report on the surgical feasibility and the functional outcome of the extraocular part of an approach to connect a subretinal prosthesis to an extracorporeal connector in the retro-auricular space via a trans-scleral, transchoroidal cable.

METHODS

Seven volunteers with retinitis pigmentosa received an active subretinal implant; energy was supplied by gold wires on a trans-sclerally, transchoroidally implanted polyimide foil leading to the lateral orbital rim where it was fixated and connected to a silicone cable. The cable was implanted subperiostally beneath the temporal muscle using a trocar to the retro-auricular space where it penetrated the skin for connection to a stimulator. To avoid subretinal movement of the implant, three tension relief points have been introduced.

RESULTS

All implantations were performed as planned without complications, and no serious adverse events occurred in the postoperative period. Fixation of the implants was stable throughout the entire study duration of 4 weeks; permanent skin penetration proved to be uncomplicated. Motility was minimally restricted in downgaze and ab-/adduction. Explantation was uneventful.

CONCLUSION

The above-described procedure provides a method for stable fixation of a subretinal device with a trans-scleral, transchoroidal cable connection to an extracorporeal connector.

Vitrektomie bei Uveitis im Kindes- und Jugendalter

PURPOSE

The role of vitrectomy in pediatric uveitis has as yet not been established. Addressing this question has been reinforced since the recent introduction of the new and relatively well tolerated medical treatment options using biologicals, i. e. TNFalpha blocking agents.

METHODS

A systematic review of literature has been supplemented by results of vitrectomy performed in 41 consecutive eyes of 33 children and adolescents at our institution and followed for 0.5 to 10 years.

RESULTS

No single controlled study on the role of vitrectomy for uveitis has been identified. Beyond a total of 44 case series including 1762 eyes within the last 25 years, 3 papers specifically focussed on vitrectomy for pediatric uveitis including 73 eyes. This series included 29 eyes of our series. Published and recent own data indicate 2 specific findings consistent for all series: reduction of CME presence from 36 to 6.9% with a resulting visual improvement in 79.1% of cases and a quietening down of inflammatory activity postoperatively allowing to taper down or stop steroid and immunosuppressive therapy from preoperatively 80 and 30% to approximately 30 and 10%, respectively.

CONCLUSION

In the absence of evidence-based results, the data from case series indicate that vitrectomy for pediatric uveitis at least meets the expectations from vitrectomy in adult forms of uveitis regarding the reduction of cystoid macular edema and required systemic steroid and immunosuppressive therapies.

Full macular translocation following photodynamic therapy in neovascular age-related macular degeneration

PURPOSE

To report the long-term functional and anatomical outcome of full macular translocation (FMT) in eyes with neovascular age-related macular degeneration (AMD) following photodynamic therapy (PDT).

METHODS

Twelve eyes of 12 consecutive patients with neovascular AMD who were PDT-nonresponders and underwent FMT were analysed. Best-corrected visual acuity (BCVA) measurement, fundus photography, and fluorescein angiography at baseline and at follow-up examinations in 3 months intervals were performed. Primary end point was change of BCVA from baseline to last visit.

RESULTS

Totally 12 eyes of 12 patients were analysed. Mean time interval between the last PDT and FMT was 3.7 months (range 1-10 months). Mean follow-up after FMT was 25.6 months. BCVA ranged at baseline from 20/1000 to 20/80 (mean 20/230). At the last visit, mean BCVA was by 20/185. BCVA improved in 50% (6/12) of eyes by more than 1 line. Twenty five per cent (3/12) of eyes had final BCVA within +/-1 line from baseline. In 25% (3/12) of eyes the BCVA decreased by more than 1 line. One eye had recurrent CNV. In four eyes a cystoid macular oedema developed. No retinal detachment or disturbing diplopia was noted.

CONCLUSIONS

In the present study, FMT in PDT-nonresponders stabilised or improved visual acuity in the majority of the eyes in a mean follow-up period of nearly 2 years. FMT can be considered as a therapeutical option in eyes who are nonresponders to the PDT in neovascular AMD.

[Injector implantation of a scleral-fixated intraocular lens]

BACKGROUND

In this pilot study, a new injector technique for small-incision implantation of scleral-fixated intraocular lenses (IOLs) was evaluated for IOL stability and visual rehabilitation.

PATIENTS AND METHODS

Secondary lens implantation was performed in 18 aphakic eyes using a new small incision technique with injector implantation. This allowed for haptic suturing with the lens body inside the cartridge. All patients were followed-up for best-corrected visual acuity, refraction, IOL evaluation and ultrasound biomicroscopy.

RESULTS

In all eyes the IOL was stable without tilt or torque. Best-corrected visual acuity improved 2.2 ETDRS lines after 1 week and 3.1 lines after a mean follow-up time of 7.9+/-2.8 months. Two eyes were complicated with small, peripheral transillumination defects (n=2), but no pigmentary glaucoma occurred.

CONCLUSION

By using a self-sealing tunnel incision and injector technique, significant fluid egress and consecutive transient hypotony is minimized throughout the whole procedure. The technique shows a high IOL stability without tilt and assures rapid visual rehabilitation.

[Changes of the triple flash electroretinogram after 360 degrees retinotomy and macular translocation for subfoveal choroidal neovascularisation in age-related macular degeneration]

BACKGROUND

The aim of the present study was to evaluate potential electrophysiological changes after 360 degrees retinotomy and macular translocation for subfoveal choroidal neovascularisation in patients with age-related macular degeneration.

METHODS

A consecutive series of 32 patients suffering from subfoveal choroidal neovascularisation secondary to age-related macular degeneration underwent 360 degrees retinotomy and macular translocation. The scotopic triple-flash ERG (TERG) served as the main parameter of the study and was recorded one day prior to the translocation surgery and no earlier than 4 weeks after the silicone oil removal.

RESULTS

The TERG amplitudes were significantly reduced after translocation surgery. Depending on the applied flash luminance the mean amplitude reduction of the first b-wave varied between 67 % (0.2 cds/m (2)) and 74 % (0.03 cds/m (2)). The latency of the second b-wave of the preoperative TERG proved to have predictive power with reference to the postoperative visual acuity. A statistically significant correlation between the latency of the second b-wave for a flash intensity of 0.03 and 0.1 cds/m (2) and the postoperative visual acuity was shown (p = 0,016 and p = 0,049).

CONCLUSIONS

In accordance with previous studies the present study indicates that a significant electrophysiological decrease is caused by surgical procedures associated with macular translocation. In future, due to predictive parameters of the TERG the preoperative selection of patients could be improved.

Surgical treatment of peripapillary choroidal neovascularisation

OBJECTIVE

To report the functional and morphological outcome of surgical treatment of peripapillary choroidal neovascularisation due to age-related macular degeneration.

METHODS

Consecutive interventional case series of eight patients with extensive peripapillary choroidal neovascularisation and accompanying haemorrhage who underwent subretinal surgery including extraction of the neovascular complex. Ophthalmic examination, including visual acuity testing, colour photography and fluorescein angiography, was performed at baseline and at 3, 6, 9 and 12 months, and then yearly.

RESULTS

Mean follow-up was 26 months (12-60 months). Preoperative best corrected visual acuity (BCVA) ranged from logMAR (logarithm of minimum angle of acuity) 1.0 (20/200) to logMAR 0.0 (20/20), with a mean of logMAR 0.5 (20/63). Mean postoperative BCVA was logMAR 0.3 (20/40). BCVA improved in six patients, was stable in one patient and deteriorated in one patient. Two years after surgery, one patient developed recurrence of the CNV that was removed surgically. One patient showed retinal detachment 5 years after subretinal surgery.

CONCLUSIONS

In this small case series of PPCNV, functional improvement was achieved after surgery in the majority of patients. Surgical extraction of the CNV represents an alternative treatment option in eyes with vision-threatening extensive PPCNV. Randomised controlled studies seem to be justified to evaluate further the beneficial effect and long-term functional outcome of this therapy approach.

[Effect of timolol on central corneal thickness and endothelial cell density]

BACKGROUND

The measurement of corneal thickness plays an increasing role in glaucoma screening and diagnosis. The influence of a variety of drugs on corneal thickness is well established. Especially for antiglaucomateous drugs this effect seems to be important. However, little is known about the influence of beta receptor antagonists on corneal thickness. The aim of this study was to provide evidence of the effect of timolol on central corneal thickness and endothelial cell density.

MATERIALS AND METHODS

Ten healthy volunteers (five women and five men) with a mean age of 29 years (range 25 to 56 years) were examined in a double-blind, prospective and randomised pilot study. Intraocular pressure, corneal thickness and endothelial cell density was estimated before as well as fifteen minutes, 24, 48, 72 and 96 hours after application of timolol 0.5 % eye drops twice daily. The partner eye received sodium hyaluronate eye drops twice daily and served as a control.

RESULTS

The application of timolol showed a decrease of intraocular pressure from initially 12 mmHg to 9 mmHg after four days (p = 0,0188) as well as an increase of corneal thickness from 537 microm to 557 microm after four days (p = 0,0659). There was no change of intraocular pressure (p = 0,9935) or corneal thickness (p = 0,9998) in the control eyes. There was also no effect of timolol (p = 0,2782) or sodium hyaluronate (p = 0,1940) on endothelial cell density.

CONCLUSIONS

The study provides evidence of the influence of beta receptor antagonists on corneal thickness. This effect may be caused by receptor mediated influences on corneal ion and fluid transport. Further studies are needed to show if the increase of corneal thickness after application of topical timolol has clinical importance.

[Current strategies for macular hole surgery in Germany, Austria and Switzerland]

BACKGROUND

Main aim of this study was to determine how macular hole surgery is currently being performed in Germany, Austria and Switzerland.

METHODS

A questionnaire concerning the different aspects of surgery for stage 3 macular hole was developed and sent out to the 380 members of the German Retina Society.

RESULTS

This analysis is based on 129 returned questionnaires from colleagues who perform macular hole surgery. A total of 95% (n=123) of the surgeons routinely perform vitrectomy with posterior vitreous detachment, peeling of epiretinal tissue and internal limiting membrane (ILM) peeling. Some 86% (n=106) stain the ILM, with 80% of these (n=85) using indocyanine green (ICG) in concentrations ranging from 0.005% up to 10%. Fourteen percent of ICG users perform a fluid-air exchange before applying the dye. Platelet concentrate is used by 8% of the surgeons with 97% (n=125) performing a gas tamponade using SF6 (53%), C3F8 (22%), C2F6 (16%) or just air (5%) (multiple answers: 4%). Simultaneous cataract surgery is routinely performed by 8%; by 73% only if there is significant cataract.

CONCLUSIONS

There is common consent on the basic surgical steps, but several surgical details, e.g. ILM staining, are performed in substantially different ways.

[Protein kinase C isoforms in corneal epithelium and endothelium]

BACKGROUND

Protein kinase C (PKC) plays a key role in cell metabolism. Three subgroups and 12 isoforms have been isolated so far, catalysing specific functions in cell metabolism. The demonstration of PKC subtypes in corneal tissue has been inconsistent. The aim of this study was to verify the expression of several PKC subgroups and isoforms in human and bovine corneal epithelial and endothelial cells.

MATERIALS AND METHODS

PKC subgroups and isoforms were studied using polyclonal antibodies.

RESULTS

Antibodies to PKC-alpha, -delta, -epsilon and -zeta, representing all three PKC subgroups, bound in human and bovine corneal epithelium and endothelium. No binding was found for antibodies to PKC-beta2.

CONCLUSIONS

For the first time the presence of all three PKC subgroups was demonstrated in human and bovine corneal epithelial and endothelial cells. Further studies are needed to show the role of these subgroups in cellular functions such as cell proliferation and differentiation.

Intravitreal bevacizumab (Avastin) for occult choroidal neovascularization in age-related macular degeneration

BACKGROUND

The purpose of the study is to report data on short-term safety of intravitreal bevacizumab treatment and its effect on visual function, central retinal thickness, and angiographical changes of occult choroidal neovascularization due to age-related macular degeneration.

METHODS

A consecutive interventional case series of 30 patients with active subfoveal occult choroidal neovascularization secondary to age-related macular degeneration was followed after one intravitreal injection of 1.25 mg bevacizumab at baseline and subsequent injections following standardized criteria. At baseline and follow-up visits patients had visual acuity assessment, intraocular pressure measurement, fluorescein angiography, and optical coherence tomography imaging.

RESULTS

No serious ocular or systemic adverse events were identified. A significant increase of intraocular pressure or signs of retinal toxicity or endophthalmitis were not detected in any patient. Optical coherence tomography revealed significant decrease (p < 0.001) in central retinal thickness after 1 week, 4 weeks, and 12 weeks, respectively. Fluorescein leakage decreased within 1 week and improvement was maintained at week 12 in the majority of patients. Visual acuity improved or remained stable in 29 of 30 patients; improvement of 3 or more lines was seen in 14 of 30 patients; one patients showed improvement of 6 lines. No patient had severe vision loss of 6 lines or more; moderate vision loss of 3 lines was seen in one patient. Re-injections of bevacizumab according to standard criteria were performed one to two times during the follow-up period of 12 weeks with a re-injection interval of 4 to 18 weeks (median 8 weeks).

CONCLUSIONS

Short-term results suggest that intravitreal injection of bevacizumab is well tolerated and for the majority of patients with occult choroidal neovascularization in AMD results in improvement of visual acuity, decrease in central retina thickness, and reduction of angiographic leakage of the lesion. Bevacizumab as intravitreal treatment may provide a novel therapeutic option for selected patients with exudative AMD. Randomized prospective multicenter trials seem justified to further evaluate long term effects and impact of intravitreal bevacizumab on different subtypes of AMD compared to established therapies.

[(Side) effects of VEGF inhibition]

Vascular endothelial growth factor (VEGF) plays a pivotal role for embryo- and organogenesis. By regulating haemodynamics, (lymphoid) vessel architecture, haematopoiesis and immune system, endocrinology and reparative processes in adults, inhibited VEGF can cause multiple adverse events. Although the intravitreal administration of smaller doses can drastically reduce the systemic exposure, possible local side effects on retinal perfusion and survival of neuronal tissue must be taken into consideration. Before experience has been gained with VEGF inhibitors for longer than several years, individual discussion before the use, extensive informed consent and careful follow-up are necessary. From the ethical point of view, the available drugs should not be used without hesitation despite the clear benefit. First experiences with bevacizumab (Avastin), the first available (off-label) drug in Germany, are reported. In future, direct comparison of the different available drugs has to assess possible differences in the risk-benefit profile.

Effects of bevacizumab on retinal function in isolated vertebrate retina

BACKGROUND

Bevacizumab (Avastin) is a recombinant protein that targets vascular endothelial growth factor (VEGF). In vitro, bevacizumab inhibits VEGF induced cell proliferation and tissue factor production. Abnormal angiogenesis involving VEGF is a central event during the development of choroidal neovascularisation (CNV). The present study was designed to evaluate the short term toxic effects of bevacizumab on retinal function for a therapeutic intraocular application.

METHODS

Isolated bovine retinas were perfused with an oxygen pre-incubated nutrient solution. The electroretinogram (ERG) was recorded as a transretinal potential using silver/silver chloride electrodes. Bevacizumab was added in different concentrations to the nutrient solution for 45 minutes. Thereafter the retina was reperfused for 60 minutes with normal nutrient solution. The percentage of a-wave and b-wave reduction during the application of bevacizumab was calculated and compared to control recordings.

RESULTS

During the application of three different concentrations of bevacizumab (0.08 mg/ml, 0.25 mg/ml, 0.8 mg/ml) no significant reduction of the a-wave and b-wave amplitude was observed. During the washout, the ERG amplitudes were unchanged.

CONCLUSION

The present study suggests that an intraocular application of 0.25 mg/ml bevacizumab for the treatment of CNV is reasonable. No significant short term effects of bevacizumab on retinal function were detected, but long term effects cannot be excluded.

Bevacizumab zur Therapie des sekundären Makulaödems nach venösen Gefäßverschlüssen

Application of VEGF inhibitors represents a treatment option for macular edema secondary to retinal vein occlusion that targets the disease at the causal molecular level. First reports on intravitreal injections of bevacizumab show promising morphological and functional effects and demonstrate that bevacizumab is a potent antiedematous agent in this context. A significant reduction of the central retinal thickness followed by a rapid improvement of visual acuity may be achieved within days. In a pilot study with a review period of 3 months, we found a significant improvement of one or more lines in 93% and four or more lines in 27% of eyes. This was associated with a concomitant significant reduction in central retinal thickness, which, however, was not sustained by a single injection (64% reduction after 1 month and 28% after 3 months). No relevant adverse events were noted. The duration of action after intravitreal bevacizumab administration is currently unknown. Reinjections will be necessary to maintain a lasting beneficial effect. Prospective, controlled long-term studies are mandatory to develop standardized treatment protocols that allow a safe and effective application of this off-label therapy.

Intravitreales Bevacizumab bei der neovaskulären altersabhängigen Makuladegeneration

The efficacy and safety of the therapeutic anti-VEGF concept has already been demonstrated for pegaptanib and ranibizumab. Bevacizumab acts as an antibody against all VEGF-A isoforms and has been developed for oncological indications with intravenous application. Initial reports on intravitreal administration in patients with neovascular age-related macular disease (AMD) have shown beneficial morphological and functional effects. In the meantime, bevacizumab has been used off-label in thousands of patients with AMD. However, data from prospective, controlled, randomized trials on both safety and efficacy are lacking. Herein recent experiences with bevacizumab are summarized and discussed. Furthermore, a web-based platform for online data registration and pooled analyses is presented.

Antiproliferative and cytotoxic properties of bevacizumab on different ocular cells

AIM

To evaluate the antiproliferative and cytotoxic properties of bevacizumab, a monoclonal antibody against vascular endothelial growth factor (VEGF), on human retinal pigment epithelium (ARPE19) cells, rat retinal ganglion cells (RGC5), and pig choroidal endothelial cells (CEC).

METHODS

Monolayer cultures of ARPE19, RGC5, and CEC were used. Bevacizumab (0.008-2.5 mg/ml), diluted in culture medium, was added to cells that were growing on cell culture dishes. Cellular proliferative activity was monitored by 5'-bromo-2'-deoxyuridine (BrdU) incorporation into cellular DNA and the morphology assessed microscopically. For cytotoxicity assays ARPE19, RGC5, and CEC cells were grown to confluence and then cultured in a serum depleted medium to ensure a static milieu. The MTT test was performed after 1 day. The "Live/Dead" viability/cytotoxicity assay was performed and analysed by fluorescence microscopy after 6, 12, 18, 24, 30, 36, and 48 hours of incubation. Expression of VEGF, VEGF receptors (VEGFR1 and VEGFR2) and von Willebrand factor was analysed by immunohistochemistry.

RESULTS

No cytotoxicity of bevacizumab on RGC5, CEC, and ARPE19 cells could be observed after 1 day. However, after 2 days at a bevacizumab concentration of 2.5 mg/ml a moderate decrease in ARPE19 cell numbers and cell viability was observed. Bevacizumab caused a dose dependent suppression of DNA synthesis in CEC as a result of a moderate antiproliferative activity (maximum reduction 36.8%). No relevant antiproliferative effect of bevacizumab on RGC5 and ARPE19 cells could be observed when used at a concentration of 0.8 mg/ml or lower. CEC and ARPE 19 cells stained positively for VEGF, VEGFR1, and VEGFR2. More than 95% of the CEC were positive for von Willebrand factor.

CONCLUSIONS

These experimental findings support the safety of intravitreal bevacizumab when used at the currently applied concentration of about 0.25 mg/ml. Bevacizumab exerts a moderate growth inhibition on CEC when used in concentrations of at least 0.025 mg/ml. However, at higher doses (2.5 mg/ml) bevacizumab may be harmful to the retinal pigment epithelium.