Electrophysiological Assessment of Optic Nerve and Retinal Functions Following Intravitreal Injection of Bevacizumab (Avastin)

Abstract

Purpose:

To evaluate the retinal and optic nerve functions of bevacizumab when injected intravitreal in human eyes using electrophysiological tests; electroretinogram (ERG) and visual evoked potentials (VEP).

Methods:

Fifty-five eyes of 55 patients with choroidal neovascular membrane (CNV) who were prepared for intravitreal injections of 1.25 mg bevacizumab underwent baseline ERG and VEP in both eyes before, and at 1 and 6 weeks after the intravitreal injections.

Results:

Mean age was 50 years ranging from 24 to 62 years, with 32 age-related macular degenerations and 23 myopic patients. Mean baseline best corrected visual acuity (BCVA) was 4/60, and mean final BCVA at 6 weeks was 6/60. There was no statistically significant reduction of the postinjection (1 and 6 weeks) ERG A and B-waves or the VEP waves' amplitudes and latency, or in the contralateral noninjected eyes. On the contrary, there were statistically significant improvement at 1 and 6 weeks in the photopic B-wave of the injected and fellow eyes (P values=0.046, and <0.001).

Conclusions:

Intravitreal bevacizumab did not appear to be toxic to the retina or the optic nerve at a concentration of 1.25 mg.

Introduction

Bevacizumab (Avastin, Genentech) is a full-length, humanized, murine monocloncal antibody directed against all the biologically active forms of vascular endothelial growth factor-A (VEGF).¹ Bevacizumab, the first anti-VEGF drug to be approved by the Food and Drug Administration, was developed as an intravenous therapy for cancer patients because VEGF is one of the major angiogenic stimuli responsible for neovascularization in tumors.^2–5 Anti-VEGF therapy has shown promising results in several forms of cancer, and the drug is currently approved for the treatment of different types of cancer.⁶

Philip Rosenfeld and colleagues publications for the efficacy of systemic⁷ then intravitreal injections⁸ of bevacizumab for patients with choroidal neovascular membranes (CNV) secondary to age-related macular degenerations (AMD), have initiated a worldwide interest in the use of this drug for many ocular pathologies.^9–13 During the past 5 years, many researchers have assessed the safety of intravitreal bevacizumab on retinal functions by histopathology and electrophysiology mainly electroretinograms (ERG).^14–18 However, only few studies have investigated the effect of bevacizumab on optic nerve functions in human eyes,¹⁸ which could be affected either by direct toxicity or indirectly by reducing blood circulation in the optic nerve head. In this study we investigated the effect of intravitreal bevacizumab on optic nerve and retinal functions by electrophysiological test; visual evoked potentials (VEP) and ERG.

Methods

Approval for the study was obtained from the hospital's ethical committee, and the tenets of the Declaration of Helsinki were followed. All patients received a thorough explanation of the study design and aims, and were provided with written informed consent.

This is a prospective nonrandomized uncontrolled interventional study, where patients who were scheduled for intravitreal injections of bevacizumab were included. Inclusion criteria: patients with CNV secondary to AMD or myopia. Exclusion criteria were eyes with (1) previous vitrectomy and/or intraocular surgeries, (2) recent intravitreal injections with anti-VEGFs and/or triamcinolone, (3) previous trauma, and (4) no other ocular pathologies.

Preoperatively all patients were evaluated before injection for best corrected visual acuity (BCVA), slit-lamp examination, intraocular pressure (IOP), dilated fundus examination, fundus fluorescein angiography, and optical coherence topography when necessary for the diagnosis and follow-ups after injections. Baseline ERG and VEP in both eyes were done before injections. Intravitreal injections of bevacizumab (1.25 mg/0.05 mL) were received. All patients were examined on the first day after injections to check for complications resulting from the intravitreal procedure. All patients were then re-examined 1 week after the injection for BCVA, slit lamp, and IOP. ERG and VEP were repeated 1 and 6 weeks after the intravitreal injections. Each of the ERG and VEP recordings done at baseline, 1 and 6 weeks following bevacizumab injections were done twice, 24 h apart, and the average of both recordings was taken.

Flash ERG recordings

The pupils were maximally dilated to ∼8 mm in diameter following topical application of a mixture of 0.5% tropicamide and 0.5% phenylephrine HCL. Ganzfield full- field electroretinogram (ffERGs) were recorded from both eyes on the Espion E² ERG instrument using Dawson-Trick-Litzkow–Plus electrodes (both by Diagnosys LLC). ERGs were done according to the International Society for Clinical Electrophysiology of Vision (ISCEV) standards in both scotopic and photopic states to assess retinal function.¹⁹ The minimum protocol incorporates the rod-specific and standard bright flash ERGs, both recorded after a minimum of 20 min dark adaptation. After 10 min of light adaptation, the photopic 30 Hz flicker cone and transient photopic cone ERGs were recorded. In brief, the parameters measured were: a 30 Hz flicker (in a light-adapted patient, cone responses are evoked by a stimulus flickering at 30 Hz); a photopic single flash; scotopic oscillatory potentials; and scotopic single flash (in the dark-adapted eye is maximal response, a bright single white flash stimulus and in a dark-adapted eye, a rod-isolated response is obtained that occurs after a dark-adapted patient receives dim white and/or a blue flash that is below the cone threshold, and doing so, the resulting waveform is almost exclusively a B-wave).

Flash VEP recordings

VEPs were done according to the ISCEV standards.¹⁹ Flash VEPs were recorded using 5 electrodes positioned 3–5 cm apart (depending on the subject's head size) across the occiput in a row 2 cm above the inion. These were referred to a mid-frontal reference electrode at Fz. Their positions were aligned according to the international 10–20 system.²⁰ Electrode impedance was <5 kohms. Low and high bandpass filter settings were 1 and 100 Hz with an analysis time of 250 ms. Patients wore their full spectacle correction throughout. Flash VEPs were recorded to a 2 Hz stimulus of intensity 17 cd/s/m² using a Grass photic stimulator positioned ∼25 cm from the subject's eyes (<25 cm if younger subjects showed limited compliance).

Data were statistically described in terms of range, mean±standard deviation (±SD), frequencies (number of cases), and percentages when appropriate. Comparison of numerical variables between the study groups was done using 1-way analysis of variance (ANOVA) test with post hoc multiple 2-group comparisons. P values less than 0.05 was considered statistically significant. All statistical calculations were done using computer programs Microsoft Excel 2007 (Microsoft Corporation) and SPSS (Statistical Package for the Social Science; SPSS, Inc.) version 19 for Microsoft Windows.

Results

Fifty-five eyes of 55 patients were included in our study with a mean age of 50 years (ranging from 24 to 62 years). Male to female ratio was 4:5. Patients' diagnoses were as follows: 33 patients with CNV due to AMD and 22 patients with myopic CNV. IOPs did not change in any of our patients during the study period. Mean baseline BCVA was 4/60, and mean final BCVA at 6 weeks was 6/60. All our patients had a relatively small to moderate size CNV (1–2 Disc Area) with no exudation.

Tables 1 –3 shows the mean with the SDs of the photopic and scotopic ERG A and B-waves (Tables 1 and 2); and VEP P100 amplitude and latency (Table 3) for the injected eyes and fellow eyes; before, 1 week, and 6 weeks after injections. There were no statistically significant reduction of the ERG A and B-waves amplitudes in the injected and fellow eyes under scotopic and photopic conditions at 1 and 6 weeks postinjection (P values >0.05). Also there were no statistically significant reduction of the VEP P100 amplitude and latency at 1 and 6 weeks when compared with baseline records (P values >0.05).

Table 1.

The Mean, Standard Deviation, Minimum and Maximum for the Photopic and Scotopic Electroretinogram A and B-Waves of the Injected Eyes at Baseline, 1 and 6 Weeks After Injections

Injected eyes ERG		Mean (μv and msec)	SD	Minimum	Maximum	P value
Photopic-Amp.-A	Baseline	10.856	1.1094	9.8	13.0	0.289
	1 week	11.628	1.6935	9.5	14.2
	6 weeks	11.500	1.7829	8.5	15.0
Photopic-Amp.-B	Baseline	18.100	5.4653	12.6	30.0	0.046^a
	1 week	22.211	5.1512	14.7	29.1
	6 weeks	21.828	5.3707	13.7	29.4
Photopic-Time-A	Baseline	19.744	1.8017	17.0	23.1	0.536
	1 week	19.939	1.5294	18.3	23.2
	6 weeks	20.361	1.7109	18.3	23.8
Photopic-Time-B	Baseline	38.094	2.7511	39.9	42.7	0.547
	1 week	40.300	2.3702	38.0	45.0
	6 weeks	40.339	2.7470	37.5	46.2
Scotopic-Amp.-A	Baseline	30.933	4.2903	26.8	40.1	0.555
	1 week	29.372	4.7638	20.0	36.0
	6 weeks	29.606	4.8246	19.2	37.1
Scotopic-Amp.-B	Baseline	52.96	12.272	36	72	0.837
	1 week	51.33	7.055	38	60
	6 weeks	51.44	7.073	37	60
Scotopic-Time-A	Baseline	21.872	1.5661	19.9	25.0	0.873
	1 week	22.094	1.5739	19.7	25.0
	6 weeks	22.128	1.6427	19.0	24.9
Scotopic-Time-A	Baseline	42.06	2.076	39	46	0.337
	1 week	41.28	1.641	39	45
	6 weeks	41.23	1.860	38	45

Included are the P values for the statistical analysis between different study points.

ERG, electroretinogram; μv, microvolt; msec, millisecond; SD, standard deviation.

Significant.

Table 2.

The Mean, Standard Deviation, Minimum and Maximum for the Photopic and Scotopic Electroretinogram A and B-Waves of the Fellow Eyes at Baseline, 1 and 6 Weeks After Injections

Fellow eyes ERG		Mean (μv and msec)	SD	Minimum	Maximum	P value
Photopic-Amp.-A	Baseline	10.79	2.369	9	16	0.969
	1 week	10.66	1.057	9	13
	6 weeks	10.76	1.395	9	14
Photopic-Amp.-B	Baseline	17.017	2.9723	13.8	22.7	0.001^a
	1 week	20.833	3.6526	16.7	25.8
	6 weeks	20.972	3.5323	16.5	27.0
Photopic-Time-A	Baseline	19.772	1.6424	17.9	22.2	0.568
	1 week	20.250	1.8202	18.3	24.2
	6 weeks	20.350	1.7270	17.7	24.0
Photopic-Time-B	Baseline	39.96	2.296	36	43	0.994
	1 week	40.04	2.413	37	45
	6 weeks	40.01	2.194	37	45
Scotopic-Amp.-A	Baseline	30.63	7.062	17	40	0.992
	1 week	30.49	4.107	23	36
	6 weeks	30.41	4.053	22	35
Scotopic-Amp.-B	Baseline	49.42	6.579	39	60	0.915
	1 week	48.87	9.257	29	57
	6 weeks	48.23	9.218	29	57
Scotopic-Time-A	Baseline	22.139	1.6400	19.0	25.9	0.574
	1 week	22.878	2.9353	18.9	29.6
	6 weeks	22.994	3.0645	18.9	29.6
Scotopic-Time-B	Baseline	41.94	2.100	38	46	0.281
	1 week	41.13	1.320	40	44
	6 weeks	41.24	1.371	39	44

Included are the P values for the statistical analysis between different study points.

Significant.

Table 3.

The Mean, Standard Deviation, Minimum and Maximum for the Visual Evoked Potential N75, P100, N145, and N75-P100 of the Injected and the Fellow Eyes at Baseline, 1 and 6 Weeks After Injections

VEP			Mean (μv and msec)	SD	Minimum	Maximum	P value
Injected Eyes	N75	Baseline	73.467	17.6389	46.6	103.0	0.237
		1 week	65.197	15.8925	43.4	92.1
		6 weeks	65.322	15.9816	43.4	93.1
	P100	Baseline	101.6428	17.05079	79.90	130.00	0.985
		1 week	100.9144	13.78020	82.50	125.10
		6 weeks	100.8683	13.64484	82.50	124.40
	N145	Baseline	134.983	20.2343	102.3	160.3	0.502
		1 week	128.467	18.2738	101.3	155.6
		6 weeks	128.594	18.1507	101.4	155.4
	N75-P100	Baseline	6.5356	2.35937	4.07	11.51	0.803
		1 week	7.2356	4.49739	2.90	15.23
		6 weeks	7.3272	4.48600	3.10	15.34
Fellow Eyes	N75	Baseline	71.3983	13.98152	54.44	92.11	0.648
		1 week	67.3189	15.31953	46.88	93.01
		6 weeks	67.3811	15.59651	46.78	94.11
	P100	Baseline	104.103	18.0575	81.2	130.3	0.558
		1 week	99.457	13.1494	81.6	118.1
		6 weeks	99.350	13.2067	81.3	118.5
	N145	Baseline	132.917	21.8953	99.8	167.3	0.999
		1 week	132.733	14.7776	119.0	157.0
		6 weeks	132.750	14.7400	119.0	157.0
	N75-P100	Baseline	8.8339	2.38320	4.98	12.40	0.226
		1 week	7.6889	4.06825	3.59	16.00
		6 weeks	7.6628	4.07662	3.54	16.00

Included are the P values for the statistical analysis between different study points.

VEP, visual evoked potential.

On the contrary, there was improvement in the following: (1) Photopic B-wave in the injected eyes showed significant improvement after the injections at 1 and 6 weeks (P value=0.046). (2) Photopic B-wave in the fellow eyes showed a highly significant improvement after the injections at 1 and 6 weeks (P value <0.001). (3) Nonsignificant improvement was also noted in the photopic A-wave amplitudes of the injected eyes at 1 and 6 weeks postinjections. (4) Although the VEP data analysis showed no significant difference between the baseline amplitude and latency, yet there were a notable improvement of all parameters in the injected eyes at 1 and 6 weeks (Table 3). Multiple group analysis was done to confirm the above result (Table 4).

Table 4.

All Electroretinogram and Visual Evoked Potential Waves' Amplitudes and Implicit Time/Latency

Multiplicity comparison		ERG sig	injected	fellow	VEP	P value
Baseline	1 week	Photopic-Amp.-A	0.143	0.807	Study-N75	0.139
	6 weeks		0.220	0.946		0.145
1 week	Baseline		0.143	0.807		0.139
	6 weeks		0.807	0.861		0.982
6 weeks	Baseline		0.220	0.946		0.145
	1 week		0.807	0.861		0.982
Baseline	1 week	Photopic-Amp.-B	0.025^a	0.001^a	Study-P100	0.884
	6 weeks		0.041^a	0.001^a		0.877
1 week	Baseline		0.025^a	0.001^a		0.884
	6 weeks		0.830	0.903		0.993
6 weeks	Baseline		0.041^a	0.001^a		0.877
	1 week		0.830	0.903		0.993
Baseline	1 week	Photopic-Time-A	0.731	0.412	Study-N145	0.306
	6 weeks		0.277	0.321		0.316
1 week	Baseline		0.731	0.412		0.306
	6 weeks		0.456	0.863		0.984
6 weeks	Baseline		0.277	0.321		0.316
	1 week		0.456	0.863		0.984
Baseline	1 week	Photopic-Time-B	0.132	0.914	Study-N75-P100	0.594
	6 weeks		0.331	0.954		0.547
1 week	Baseline		0.132	0.914		0.594
	6 weeks		0.987	0.960		0.944
6 weeks	Baseline		0.331	0.954		0.547
	1 week		0.987	0.960		0.944
Baseline	1 week	Scotopic-Amp.-A	0.317	0.940	Fellow-N75	0.418
	6 weeks		0.394	0.902		0.425
1 week	Baseline		0.317	0.940		0.418
	6 weeks		0.880	0.962		0.990
6 weeks	Baseline		0.394	0.902		0.425
	1 week		0.880	0.962		0.990
Baseline	1 week	Scotopic-Amp.-B	0.595	0.847	Fellow-P100	0.357
	6 weeks		0.621	0.676		0.346
1 week	Baseline		0.595	0.847		0.357
	6 weeks		0.971	0.821		0.983
6 weeks	Baseline		0.621	0.676		0.346
	1 week		0.971	0.821		0.983
Baseline	1 week	Scotopic-Time-A	0.678	0.403	Fellow-N145	0.975
	6 weeks		0.633	0.333		0.977
1 week	Baseline		0.678	0.403		0.975
	6 weeks		0.950	0.895		0.998
6 weeks	Baseline		0.633	0.333		0.977
	1 week		0.950	0.895		0.998
Baseline	1 week	Scotopic-Time-B	0.217	0.143	Fellow-N75-P100	0.080
	6 weeks		0.189	0.205		0.076
1 week	Baseline		0.217	0.143		0.080
	6 weeks		0.936	0.839		0.983
6 weeks	Baseline		0.189	0.205		0.076
	1 week		0.936	0.839		0.983

Multiple group analysis at the different study points; baseline, 1 and 6 weeks.

Significant.

Electroretinograms

Figures 1 and 2 show the mean of the photopic and scotopic A and B-wave amplitudes at baseline, 1 and 6 weeks after injections in the injected and fellow eyes, respectively.

FIG. 1.

The injected eyes' mean±standard deviation (SD) electroretinogram (ERG) waves' amplitudes: Photopic: A-wave: 10.85±10.1, 11.62±1.69, 11.5±1.78, B-wave: 18.1±5.46, 22.21±5.15, 21.82±5.37; Scotopic: A-wave: 30.93±4.29, 29.37±4.76, 29.6±4.82, B-wave: 52.96±12.27, 51.33±7.05, 51.44±7.07, at baseline, 1 and 6 weeks postinjections, respectively.

FIG. 2.

The fellow eyes' mean±SD ERG waves' amplitudes: Photopic: A-wave: 10.79±2.36, 10.66±1.05, 10.76±1.39, B-wave: 17.01±2.97, 20.83±3.65, 20.97±3.53; Scotopic: A-wave: 30.63±7.06, 30.49±4.1, 30.41±4.05, B-wave: 49.42±6.57, 48.87±9.25, 48.23±9.21, at baseline, 1 and 6 weeks postinjections, respectively.

Photopic conditions

The injected and fellow eyes showed slight improved amplitudes which were significant for the B-wave at 1 and 6 weeks postinjection in both eyes.

Scotopic conditions

No significant changes were observed in both eyes at 1 and 6 weeks after the injections, but there was a slight nonsignificant depression of A and B-waves.

Visual evoked potentials

There were no observed deterioration in the P100 amplitudes and latency in the injected and fellow eyes at 1 and 6 weeks after injections as seen in Figs. 3 and 4. However, improved P100 amplitudes (Fig. 3) and latency (Fig. 4) in the injected eyes is noted at 1 and 6 weeks after injections.

FIG. 3.

The mean±SD of the visual evoked potential (VEP) P100 amplitudes (N75-P100) for the injected (6.53±2.35, 7.23±4.49, 7.32±4.48) and fellow eyes (8.83±2.38, 7.68±4.06, 7.66±4.07), at baseline, 1 and 6 weeks postinjections, respectively.

FIG. 4.

The mean±SD of the VEP P100 latency for the injected (101.64±17.05, 100.91±13.78, 100.86±13.64) and fellow eyes (104.103±18.05, 99.45±13.14, 99.35±13.2) at baseline, 1 and 6 weeks postinjections, respectively.

Discussion

Although the retinal toxicity of intravitreal bevacizumab has been tested in numerous humans and animals study and appeared to be safe,^14–18 its effect on optic nerve head functions was not properly investigated. Bevacizumab has been found to occasionally produce retinal ischemia due to the reduction of VEGFs which appeared to play an important role in normal retinal vascularity and circulation.

To provide additional insight into the safety of intravitreal bevacizumab, we performed electrophysiological tests to study optic nerve and retinal toxicity. We report a series of patients who received a single intravitreal injection of bevacizumab 1.25 mg in 0.05 mL for CNV (AMD and myopia) that had a baseline VEP and ERG (photopic and scotopic), at 1 and 6 weeks postinjections.

Previous animal studies using flash VEP¹⁶ showed that responses of the experimental eyes were of normal pattern and amplitude and did not differ from those recorded by stimulation of the control eye alone. In human eyes, Pai et al.¹⁸ used pattern VEP in addition to multifocal electroretinogram (mfERG) and ffERG. Testing for retinal and optic nerve functions by ffERG, mfERG, and pattern VEP studies showed no short-term safety concerns of intravitreal bevacizumab.

Our present study confirms the previous reports on the safety of intravitreal injection of bevacizumab. Our nonrandomized, uncontrolled, prospective, interventional study did not find any statistically significant reduction of ERG waves' amplitudes and implicit times or in VEP P100 amplitudes or latency times at 1 and 6 weeks after intravitreal injections of bevacizumab; compared to baseline in both eyes. On the contrary, we found significant improvements in some ERG in both the injected and the fellow eyes and non significant VEP waves improvements in the injected eyes as mentioned earlier. However, we do not have any scientific explanation for these changes at the moment.

In conclusion, intravitreal bevacizumab appeared to be safe and tolerable with no detectable significant reduction in optic nerve or retinal functions in the injected or the fellow eyes. However, this study is limited by its short duration; a study with a longer follow-up duration, perhaps 6 months, is needed. In addition, further research with a larger sample size for each disease entity is warranted to confirm the results in this study.

Footnotes

Author Disclosure Statement

The authors report no declarations of interest. The authors have no disclosure(s) to declare. The authors have no financial or proprietary interest in any product mentioned in this article. There is no funding/support for this study.

References

Presta

L.G.

, Chen

, O'Connor

S.J.

et al. Humanization of an anti-vascular endothelial growth factor monoclonal antibody for the therapy of solid tumors and other disorders. Cancer Res., 57:4593–4599. 1997.

Hurwitz

, Fehrenbacher

, Novotny

et al. Bevacizumab plus irinotecan, fluorouracil, and leucovorin for metastatic colorectal cancer. N. Engl. J. Med., 350:2335–2342. 2004.

Hurwitz

H.I.

, Fehrenbacher

, Hainsworth

J.D.

et al. Bevacizumab in combination with fluorouracil and leucovorin: an active regimen for first-line metastatic colorectal cancer. J. Clin. Oncol., 23:3502–3508. 2005.

Kabbinavar

F.F.

, Hambleton

, Mass

R.D.

, Hurwitz

H.I.

, Bergsland

, Sarkar

Combined analysis of efficacy: the addition of bevacizumab to fluorouracil/leucovorin improves survival in patients with metastatic colorectal cancer. J. Clin. Oncol., 23:3706–3712. 2005.

Kabbinavar

F.F.

, Schulz

, McCleod

et al. Addition of bevacizumab to bolus fluorouracil and leucovorin in first-line metastatic colorectal cancer: results of a randomized phase II trial. J. Clin. Oncol., 23:3697–3705. 2005.

Midgley

, Kerr

Bevacizumab: current status and future directions. Ann. Oncol., 16:999–1004. 2005.

Michels

, Rosenfeld

P.J.

, Puliafito

C.A.

, Marcus

E.N.

, Venkatraman

A.S.

Systemic bevacizumab (Avastin) therapy for neovascular age-related macular degeneration 12-week results of an uncontrolled open-label clinical study. Ophthalmology, 112:1035–1047. 2005.

Rosenfeld

P.J.

, Moshfeghi

A.A.

, Puliafito

C.A.

Optical coherence tomography findings after an intravitreal injection of bevacizumab (avastin) for neovascular age-related macular degeneration. Ophthalmic Surg. Lasers Imaging, 36:331–335. 2005.

Avery

R.L.

, Pearlman

, Pieramici

D.J.

et al. Intravitreal bevacizumab (Avastin) in the treatment of proliferative diabetic retinopathy. Ophthalmology, 113:1695. 2006.

10.

Y.J.

Intravitreal bevacizumab vs triamcinolone acetonide for macular oedema due to central retinal vein occlusion. Eye (Lond)., 24:1414. 2010.

11.

Ruiz-Moreno

J.M.

, Montero

J.A.

Intravitreal bevacizumab to treat myopic choroidal neovascularization: 2-year outcome. Graefes Arch. Clin. Exp. Ophthalmol., 248:937–941. 2010.

12.

Ehrlich

, Ciulla

T.A.

, Maturi

et al. Intravitreal bevacizumab for choroidal neovascularization secondary to presumed ocular histoplasmosis syndrome. Retina, 29:1418–1423. 2009.

13.

Altinsoy

H.I.

, Mutlu

F.M.

, Güngör

, Sarici

S.U.

Combination of laser photocoagulation and intravitreal bevacizumab in aggressive posterior retinopathy of prematurity. Ophthalmic Surg. Lasers Imaging, 9:1–5. 2010.

14.

Feiner

, Barr

E.E.

, Shui

Y.B.

, Holekamp

N.M.

, Brantley

MA.

Jr.

Safety of intravitreal injection of bevacizumab in rabbit eyes. Retina, 26:882–888. 2006.

15.

Bakri

S.J.

, Cameron

J.D.

, McCannel

C.A.

, Pulido

J.S.

, Marler

R.J.

Absence of histologic retinal toxicity of intravitreal bevacizumab in a rabbit model. Am. J. Ophthalmol., 142:162–164. 2006.

16.

Shahar

, Avery

R.L.

, Heilweil

et al.

Electrophysiologic and retinal penetration studies following intravitreal injection of bevacizumab (Avastin)

Retina, 26:262–269. 2006.

17.

Manzano

R.P.

, Peyman

G.A.

, Khan

, Kivilcim

Testing intravitreal toxicity of bevacizumab (Avastin)

Retina, 26:257–261. 2006.

18.

Pai

S.A.

, Shetty

, Vijayan

et al. Clinical, anatomic, and electrophysiologic evaluation following intravitreal bevacizumab for macular edema in retinal vein occlusion. Am. J. Ophthalmol., 143:601–606. 2007.

19.

Marmor

M.F.

, Holder

G.E.

, Seeliger

M.W.

, Yamamoto

International society for clinical electrophysiology of vision. Standard for clinical electroretinography (2004 update)

Doc. Ophthalmol., 108:107–114. 2004.

20.

Jasper

H.H.

The ten-twenty electrode system of the international federation of electroencephalography. Electronceph. Clin. Neurophysiol., 10:371–375. 1958.