Amani A. Fawzi

Photoacoustic ophthalmoscopy for in vivo retinal imaging

We have developed a non-invasive photoacoustic ophthalmoscopy (PAOM) for in vivo retinal imaging. PAOM detects the photoacoustic signal induced by pulsed laser light shined onto the retina. By using a stationary ultrasonic transducer in contact with the eyelids and scanning only the laser light across the retina, PAOM provides volumetric imaging of the retinal micro-vasculature and retinal pigment epithelium at a high speed. For B-scan frames containing 256 A-lines, the current PAOM has a frame rate of 93 Hz, which is comparable with state-of-the-art commercial spectral-domain optical coherence tomography (SD-OCT). By integrating PAOM with SD-OCT, we further achieved OCT-guided PAOM, which can provide multi-modal retinal imaging simultaneously. The capabilities of this novel technology were demonstrated by imaging both the microanatomy and microvasculature of the rat retina in vivo.

Pilot study of optical coherence tomography measurement of retinal blood flow in retinal and optic nerve diseases

PURPOSE To investigate blood flow changes in retinal and optic nerve diseases with Doppler Fourier domain optical coherence tomography (OCT). METHODS Sixty-two participants were divided into five groups: normal, glaucoma, nonarteritic ischemic optic neuropathy (NAION), treated proliferative diabetic retinopathy (PDR), and branch retinal vein occlusion (BRVO). Doppler OCT was used to scan concentric circles of 3.4- and 3.75-mm diameters around the optic nerve head. Flow in retinal veins was calculated from the OCT velocity profiles. Arterial and venous diameters were measured from OCT Doppler and reflectance images. RESULTS Total retinal blood flow in normal subjects averaged 47.6 μL/min. The coefficient of variation of repeated measurements was 11% in normal eyes and 14% in diseased eyes. Eyes with glaucoma, NAION, treated PDR, and BRVO had significantly decreased retinal blood flow compared with normal eyes (P < 0.001). In glaucoma patients, the decrease in blood flow was highly correlated with the severity of visual field loss (P = 0.003). In NAION and BRVO patients, the hemisphere with more severe disease also had lower blood flow. CONCLUSIONS Doppler OCT retinal blood flow measurements showed good repeatability and excellent correlation with visual field and clinical presentations. This approach could enhance our understanding of retinal and optic nerve diseases and facilitate the development of new therapies.

Bevacizumab and ranibizumab tachyphylaxis in the treatment of choroidal neovascularisation

Aims To evaluate the effect of switching to bevacizumab or ranibizumab after developing tachyphylaxis during anti-vascular endothelial growth factor (VEGF) therapy for choroidal neovascularisation (CNV). Methods The authors reviewed the records of all patients who received both ranibizumab and bevacizumab for treatment of CNV to identify those who developed tachyphylaxis, defined as optical coherence tomography evidence of initial decreased exudation followed by lack of further reduction or an increase in exudation. Signs of exudation included subreitnal fluid (SRF), pigment epithelial detachment (PED) and/or cystoid macular oedema (CMO). Results 26 eyes were included. 10 were initially treated with bevacizumab and then changed to ranibizumab for persistent SRF, PED and/or CMO. Of these, seven had occult CNV and three had predominantly classic CNV. One eye in the occult CNV group did not respond after being switched to ranibizumab. Six eyes had a positive therapeutic response, after one injection in four eyes, and after two or three injections in one eye each. In the classic group, two responded to ranibizumab and one did not. Sixteen eyes were initially treated with ranibizumab before changing to bevacizumab. Of these, 15 had occult CNV and 1 was predominantly classic. Three of the 16 eyes failed to respond to bevacizumab; 6 improved after one injection and 5 after two injections. Conclusions Patients with CNV who develop tachyphylaxis to ranibizumab or bevacizumab may respond to another anti-VEGF drug. The majority of cases (81%) in this series demonstrated at least some response after switching therapies.

Long-Term Results from an Epiretinal Prosthesis to Restore Sight to the Blind

PURPOSE Retinitis pigmentosa (RP) is a group of inherited retinal degenerations leading to blindness due to photoreceptor loss. Retinitis pigmentosa is a rare disease, affecting only approximately 100 000 people in the United States. There is no cure and no approved medical therapy to slow or reverse RP. The purpose of this clinical trial was to evaluate the safety, reliability, and benefit of the Argus II Retinal Prosthesis System (Second Sight Medical Products, Inc, Sylmar, CA) in restoring some visual function to subjects completely blind from RP. We report clinical trial results at 1 and 3 years after implantation. DESIGN The study is a multicenter, single-arm, prospective clinical trial. PARTICIPANTS There were 30 subjects in 10 centers in the United States and Europe. Subjects served as their own controls, that is, implanted eye versus fellow eye, and system on versus system off (native residual vision). METHODS The Argus II System was implanted on and in a single eye (typically the worse-seeing eye) of blind subjects. Subjects wore glasses mounted with a small camera and a video processor that converted images into stimulation patterns sent to the electrode array on the retina. MAIN OUTCOME MEASURES The primary outcome measures were safety (the number, seriousness, and relatedness of adverse events) and visual function, as measured by 3 computer-based, objective tests. RESULTS A total of 29 of 30 subjects had functioning Argus II Systems implants 3 years after implantation. Eleven subjects experienced a total of 23 serious device- or surgery-related adverse events. All were treated with standard ophthalmic care. As a group, subjects performed significantly better with the system on than off on all visual function tests and functional vision assessments. CONCLUSIONS The 3-year results of the Argus II trial support the long-term safety profile and benefit of the Argus II System for patients blind from RP. Earlier results from this trial were used to gain approval of the Argus II by the Food and Drug Administration and a CE mark in Europe. The Argus II System is the first and only retinal implant to have both approvals.

Image registration and multimodal imaging of reticular pseudodrusen

PURPOSE To characterize reticular pseudodrusen (RPD) by using a point-to-point comparison of the reticular pattern on infrared reflectance (IR), autofluorescence (AF), and red-free (RF) images registered with en face sections of the choroid from spectral domain optical coherence tomography (SD-OCT) scans. METHODS A cross-sectional, retrospective study of all patients with the diagnosis of AMD who presented to the Doheny Retina Institute between December 2007 and November 2009 was conducted to identify patients with RPD. IR, AF, and RF images were obtained using confocal scanning laser ophthalmoscopy and were manually registered to OCT choroidal sections to study the location of RPD. The main outcome measured was point-to-point localization of RPD across multiple imaging modalities. RESULTS Of the 153 patients with AMD, 51 had RPD. In all 51 patients (97 eyes), RPD appeared as areas of hypoautofluorescence and hyporeflectance on AF and IR imaging, respectively, and as hyporeflective interlacing networks on RF. Reticular lesions on AF, IR, and RF images consistently colocalized with stromal regions between large choroidal vessels on registered en face choroidal sections. In contrast, outer retinal changes and subretinal deposits tended to localize immediately adjacent to the RPD. CONCLUSIONS Point-to-point correlation of registered IR, AF, and RF images consistently localizes the reticular pattern to the intervascular choroidal stroma on en face OCT sections. In contrast, subretinal deposits and disturbances of the inner outer segment on OCT did not colocalize with the RPD, and may represent secondary mechanical or biologic disturbances in the overlying RPE and outer retina.

A Pilot Study of Morphometric Analysis of Choroidal Vasculature In Vivo, Using En Face Optical Coherence Tomography

Purpose To study the ability of volumetric spectral domain optical coherence tomography (SD-OCT) to perform quantitative measurement of the choroidal vasculature in vivo. Methods Choroidal vascular density and vessel size were quantified using en face choroidal scans from various depths below the retinal pigment epithelium (RPE) in 58 eyes of 58 patients with either epiretinal membranes (ERM), early age-related macular degeneration (AMD), or reticular pseudo-drusen (RPD). For each patient, we used the macular volume scan (6×6 mm cube) for vessel quantification, while high-definition (HD) cross-section raster scans were used to qualitatively assess vascularity of the choroidal sub-layers, and measure choroidal thickness. Results Of the 58 patients, more were female (66% versus 34% male), of whom 14 (24%) had ERM, 11 (19%) early AMD, and 33 (57%) RPD. Compared to intact choriocapillaris in all ERM (100%), none of the RPD and only 5/11 (45%) early AMD eyes had visible choriocapillaris on either cross section or C-scans (p-value<0.001). When comparing select regions from the most superficial C-scans, early AMD group had lowest vascular density and RPD had highest (p-value 0.04). Qualitative evaluation of C-scans from all three groups revealed a more granular appearance of the choriocapillaris in ERM versus increased stroma and larger vessels in the RPD eyes. Conclusions SD-OCT can be used to qualitatively and quantitatively assess choroidal vascularity in vivo. Our findings correlate to previously reported histopathologic studies. Lack of choriocapillaris on HD cross-sections or C-scans in all RPD and about half of early AMD eyes suggests earlier choroidal involvement in AMD and specifically, RPD.

Retinal blood flow detection in diabetic patients by Doppler Fourier domain optical coherence tomography

We present human retinal blood flow investigation for diabetic patients using Doppler Fourier domain optical coherence tomography (FDOCT). The scanning pattern consisted of two concentric circles around the optic nerve head. The blood flow in one patient with diabetes and no retinpathy and another patient with treated proliferative diabetic retinopathy were measured. The patient without retinopathy showed a total blood flow value at the lower level of the normal range. The flow distribution between superior and inferior retina was balanced. The patient with diabetic retinopathy had a flow value lower than the normal people. Our study shows that Doppler FD-OCT can be used to evaluate the total retinal blood flow in patients with retinal diseases.

Acute macular neuroretinopathy: long-term insights revealed by multimodal imaging.

Purpose: To report the structural and functional changes in acute macular neuroretinopathy (AMN) and their long-term evolution. Multimodal retinal imaging was acquired, including Fourier domain optical coherence tomography (OCT), infrared (IR) reflectance, and near IR autofluorescence (NIA). Methods: In this retrospective observational case series, detailed clinical history and multimodal imaging are reported in eight patients with AMN. Manual segmentation of the Fourier domain OCT volume scans was done in one patient with the largest AMN lesion to yield retinal sublayer topographic maps. Results: Two patients were seen within the first 1 to 2 days of symptoms, and both showed outer nuclear and outer plexiform layer hyperreflectivity. Both patients developed enlargement of the lesion over the first week on IR reflectance imaging with a corresponding lateral extension of the outer retinal disruption on Fourier domain OCT. Thinning of the outer nuclear layer persisted in all patients with lesions >100 &mgr;m width, and in one patient this thinning worsened over the course of follow-up, as noted on the sublayer maps. This structural abnormality correlated with long-term functional deficits, persisting up to 14 months after the initial episode. Infrared reflectance highlights the lesion best, and abnormalities on near IR autofluorescence may be present. Conclusion: Acute macular neuroretinopathy acutely affects the outer nuclear and plexiform layers manifesting as OCT hyperreflectivity. The hallmark long-term changes are outer nuclear thinning on Fourier domain OCT and a fading dark lesion on IR reflectance imaging. These changes correspond to focal disruption of the outer segment/retinal pigment epithelium junction on OCT, and not the inner segment/outer segment junction, as previously reported. Optical coherence tomography and near IR autofluorescence abnormalities suggest previously unrecognized melanin and retinal pigment epithelium derangements in this condition.

A Pilot Study of Fourier-Domain Optical Coherence Tomography of Retinal Dystrophy Patients

PURPOSE To characterize the macular anatomy of retinal dystrophy eyes using high-speed, high-resolution, Fourier-domain optical coherence tomography (FD-OCT). DESIGN Case-control study. METHODS Retinal dystrophy patients and normal age- and gender-matched controls underwent FD-OCT imaging using the RTVue (Optovue Inc., Fremont, California, USA). Vertical and horizontal 8-mm scans of 1024 lines/cross-section were obtained. Based on boundaries manually drawn on computer displays of OCT cross-sections, the thicknesses of the retina, inner retinal layer (IRL), and outer retinal layer (ORL) were averaged over both 5-mm (macular) and 1.5-mm (foveal) regions centered at the fovea. The IRL was the sum of nerve fiber layer (NFL), ganglion cell layer (GCL), and inner plexiform layer (IPL) thicknesses. Total retinal thickness (RT) was measured between the internal limiting membrane (ILM) and the retinal pigment epithelium. ORL thickness was calculated by subtracting IRL thickness from RT. RESULTS Fourteen patients (three retinitis pigmentosa, two cone-rod degeneration, two Stargardt disease, and seven normal controls) underwent FD-OCT imaging. Mean foveal RT was 271.3 +/- 23.3 microm for controls and 158.4 +/- 47.1 microm for retinal dystrophy patients (P < .001). Mean macular RT was 292.8 +/- 8.1 microm for controls and 199.1 +/- 32.6 microm for retinal dystrophy patients (P < .001). Mean macular ORL was 182.9 +/- 4.7 microm for controls and 101.3 +/- 18.7 microm for retinal dystrophy patients (P < .001); mean macular IRL was 109.9 +/- 6.4 microm for controls and 97.9 +/- 20.7 microm for retinal dystrophy patients (P = .06). CONCLUSION Eyes with retinal dystrophy had a small (11%) decrease in macular IRL and severe (45%) decrease in macular ORL compared to normal controls.

A lymphatic defect causes ocular hypertension and glaucoma in mice

Glaucoma is a leading cause of blindness, afflicting more than 60 million people worldwide. Increased intraocular pressure (IOP) due to impaired aqueous humor drainage is a major risk factor for the development of glaucoma. Here, we demonstrated that genetic disruption of the angiopoietin/TIE2 (ANGPT/TIE2) signaling pathway results in high IOP, buphthalmos, and classic features of glaucoma, including retinal ganglion degeneration and vision loss. Eyes from mice with induced deletion of Angpt1 and Angpt2 (A1A2Flox(WB) mice) lacked drainage pathways in the corneal limbus, including Schlemms canal and lymphatic capillaries, which share expression of the PROX1, VEGFR3, and FOXC family of transcription factors. VEGFR3 and FOXCs have been linked to lymphatic disorders in patients, and FOXC1 has been linked to glaucoma. In contrast to blood endothelium, in which ANGPT2 is an antagonist of ANGPT1, we have shown that both ligands cooperate to regulate TIE2 in the lymphatic network of the eye. While A1A2Flox(WB) mice developed high IOP and glaucoma, expression of ANGPT1 or ANGPT2 alone was sufficient for ocular drainage. Furthermore, we demonstrated that loss of FOXC2 from lymphatics results in TIE2 downregulation, suggesting a mechanism for ocular defects in patients with FOXC mutations. These data reveal a pathogenetic and molecular basis for glaucoma and demonstrate the importance of angiopoietin ligand cooperation in the lymphatic endothelium.