Advanced nanomaterials for imaging of eye diseases.

Background and purpose: Vision impairment and blindness present significant global challenges, with common causes including age-related macular degeneration, diabetes, retinitis pigmentosa, and glaucoma. Advanced imaging tools, such as optical coherence tomography, fundus photography, photoacoustic microscopy, and fluorescence imaging, play a crucial role in improving therapeutic interventions and diagnostic methods. Contrast agents are often employed with these tools to enhance image clarity and signal detection. This review aims to explore the commonly used contrast agents in ocular disease imaging. Experimental approach: The first section of the review delves into advanced ophthalmic imaging techniques, outlining their importance in addressing vision-related issues. The emphasis is on the efficacy of therapeutic interventions and diagnostic methods, establishing a foundation for the subsequent exploration of contrast agents. Key results: This review focuses on the role of contrast agents, with a specific emphasis on gold nanoparticles, particularly gold nanorods. The discussion highlights how these contrast agents optimize imaging in ocular disease diagnosis and monitoring, emphasizing their unique properties that enhance signal detection and imaging precision. Conclusion: The final section, we explores both organic and inorganic contrast agents and their applications in specific conditions such as choroidal neovascularization, retinal neovascularization, and stem cell tracking. The review concludes by addressing the limitations of current contrast agent usage and discussing potential future clinical applications. This comprehensive exploration contributes to advancing our understanding of contrast agents in ocular disease imaging and sets the stage for further research and development in the field.

Real-time cavitation monitoring during optical coherence tomography guided photo-mediated ultrasound therapy of the retina.

Photo-mediated ultrasound therapy (PUT) is a novel antivascular therapeutic modality based on cavitation-induced bioeffects. During PUT, synergistic combinations of laser pulses and ultrasound bursts are used to remove the targeted microvessels selectively and precisely without harming nearby tissue. In the current study, an integrated system combining PUT and spectral domain optical coherence tomography (SD-OCT) was developed, where the SD-OCT system was used to guide PUT by detecting cavitation in real time in the retina of the eye. METHOD: We first examined the capability of SD-OCT in detecting cavitation on a vascular-mimicking phantom and compared the results with those from a passive cavitation detector. The performance of the integrated system in treatment of choroidal microvessels was then evaluated in rabbit eyes in vivo. RESULTS: During the in vivo PUT experiments, several biomarkers at the subretinal layer in the rabbit eye were identified on OCT images. The findings indicate that, by evaluating biomarkers of treatment effect, real-time SD-OCT monitoring could help to avoid micro-hemorrhage, which is a potential major side effect. CONCLUSION: Real-time OCT monitoring can thus improve the safety and efficiency of PUT in removing the retinal and choroidal microvasculature.

Treatment Strategies for Anti-VEGF Resistance in Neovascular Age-Related Macular Degeneration by Targeting Arteriolar Choroidal Neovascularization.

Despite extensive use of intravitreal anti-vascular endothelial growth factor (anti-VEGF) biologics for over a decade, neovascular age-related macular degeneration (nAMD) or choroidal neovascularization (CNV) continues to be a major cause of irreversible vision loss in developed countries. Many nAMD patients demonstrate persistent disease activity or experience declining responses over time despite anti-VEGF treatment. The underlying mechanisms of anti-VEGF resistance are poorly understood, and no effective treatment strategies are available to date. Here we review evidence from animal models and clinical studies that supports the roles of neovascular remodeling and arteriolar CNV formation in anti-VEGF resistance. Cholesterol dysregulation, inflammation, and ensuing macrophage activation are critically involved in arteriolar CNV formation and anti-VEGF resistance. Combination therapy by neutralizing VEGF and enhancing cholesterol removal from macrophages is a promising strategy to combat anti-VEGF resistance in CNV.

Molecular and cellular imaging of the eye.

The application of molecular and cellular imaging in ophthalmology has numerous benefits. It can enable the early detection and diagnosis of ocular diseases, facilitating timely intervention and improved patient outcomes. Molecular imaging techniques can help identify disease biomarkers, monitor disease progression, and evaluate treatment responses. Furthermore, these techniques allow researchers to gain insights into the pathogenesis of ocular diseases and develop novel therapeutic strategies. Molecular and cellular imaging can also allow basic research to elucidate the normal physiological processes occurring within the eye, such as cell signaling, tissue remodeling, and immune responses. By providing detailed visualization at the molecular and cellular level, these imaging techniques contribute to a comprehensive understanding of ocular biology. Current clinically available imaging often relies on confocal microscopy, multi-photon microscopy, PET (positron emission tomography) or SPECT (single-photon emission computed tomography) techniques, optical coherence tomography (OCT), and fluorescence imaging. Preclinical research focuses on the identification of novel molecular targets for various diseases. The aim is to discover specific biomarkers or molecular pathways associated with diseases, allowing for targeted imaging and precise disease characterization. In parallel, efforts are being made to develop sophisticated and multifunctional contrast agents that can selectively bind to these identified molecular targets. These contrast agents can enhance the imaging signal and improve the sensitivity and specificity of molecular imaging by carrying various imaging labels, including radionuclides for PET or SPECT, fluorescent dyes for optical imaging, or nanoparticles for multimodal imaging. Furthermore, advancements in technology and instrumentation are being pursued to enable multimodality molecular imaging. Integrating different imaging modalities, such as PET/MRI (magnetic resonance imaging) or PET/CT (computed tomography), allows for the complementary strengths of each modality to be combined, providing comprehensive molecular and anatomical information in a single examination. Recently, photoacoustic microscopy (PAM) has been explored as a novel imaging technology for visualization of different retinal diseases. PAM is a non-invasive, non-ionizing radiation, and hybrid imaging modality that combines the optical excitation of contrast agents with ultrasound detection. It offers a unique approach to imaging by providing both anatomical and functional information. Its ability to utilize molecularly targeted contrast agents holds great promise for molecular imaging applications in ophthalmology. In this review, we will summarize the application of multimodality molecular imaging for tracking chorioretinal angiogenesis along with the migration of stem cells after subretinal transplantation in vivo.

Multimodal photoacoustic microscopy, optical coherence tomography, and fluorescence imaging of USH2A knockout rabbits.

Usher syndrome type 2A (USH2A) is a genetic disorder characterized by retinal degeneration and hearing loss. To better understand the pathogenesis and progression of this syndrome, animal models such as USH2A knockout (USH2AKO) rabbits have been developed. In this study, we employed multimodal imaging techniques, including photoacoustic microscopy (PAM), optical coherence tomography (OCT), fundus autofluorescence (FAF), fluorescein angiography (FA), and indocyanine green angiography (ICGA) imaging to evaluate the retinal changes in the USH2AKO rabbit model. Twelve New Zealand White rabbits including USH2AKO and wild type (WT) were used for the experiments. Multimodal imaging was implemented at different time points over a period of 12 months to visualize the progression of retinal changes in USH2AKO rabbits. The results demonstrate that ellipsoid zone (EZ) disruption and degeneration, key features of Usher syndrome, began at the age of 4 months old and persisted up to 12 months. The EZ degeneration areas were clearly observed on the FAF and OCT images. The FAF images revealed retinal pigment epithelium (RPE) degeneration, confirming the presence of the disease phenotype in the USH2AKO rabbits. In addition, PAM images provided high-resolution and high image contrast of the optic nerve and the retinal microvasculature, including retinal vessels, choroidal vessels, and capillaries in three-dimensions. The quantification of EZ fluorescent intensity using FAF and EZ thickness using OCT provided comprehensive quantitative data on the progression of degenerative changes over time. This multimodal imaging approach allowed for a comprehensive and non-invasive assessment of retinal structure, microvasculature, and degenerative changes in the USH2AKO rabbit model. The combination of PAM, OCT, and fluorescent imaging facilitated longitudinal monitoring of disease progression and provided valuable insights into the pathophysiology of USH2A syndrome. These findings contribute to the understanding of USH2A syndrome and may have implications for the development of diagnostic and therapeutic strategies for affected individuals. The multimodal imaging techniques employed in this study offer a promising platform for preclinical evaluation of potential treatments and may pave the way for future clinical applications in patients with Usher syndrome.

Cutaneous Hypervascularization Treatment Using Photo-Mediated Ultrasound Therapy.

Photo-mediated ultrasound therapy (PUT) is a cavitation-based, highly selective antivascular technique. In this study, the effectiveness and safety of PUT on cutaneous vascular malformation was examined through in vivo experiments in a clinically relevant chicken wattle model, whose microanatomy is similar to that of port-wine stain and other hypervascular dermal diseases in humans. Assessed by optical coherence tomography angiography, the blood vessel density in the chicken wattle decreased by 73.23% after one session of PUT treatment in which 0.707 J/cm2 fluence laser pulses were applied concurrently with ultrasound bursts (n = 7, P < .01). The effectiveness of removing blood vessels in the skin at depth up to 1 mm was further assessed by H&E-stained histology at multiple time points, which included days 1, 3, 7, 14, and 21 after treatment. Additional immunohistochemical analyses with CD31, caspase-3, and Masson's trichrome stains were performed on day 3 after treatment. The results show that the PUT-induced therapeutic effect was confined and specific to blood vessels only, whereas unwanted collateral damage in other skin tissues such as collagen was avoided. The findings from this study demonstrate that PUT can efficiently and safely remove hypervascular dermal capillaries using laser fluence at a level that is orders of magnitude smaller than that used in conventional laser treatment of vascular lesions, thus offering a safer alternative technique for clinical management of cutaneous vascular malformations.

Diabetic Retinopathy Screening Using a Portable Retinal Camera in Vanuatu.

Background and Objective: Proof-of-concept study to test the feasibility of using an all-in-one portable retinal camera for the screening of diabetic retinopathy in the Pacific Island of Vanuatu, which has a high rate of diabetes and its associated complications and a dearth of ophthalmologists. Study Design/Materials and methods: From February 10, 2020, through February 28, 2020, 49 patients with diabetes mellitus from three islands in Vanuatu were recruited to participate in the study. Demographics, basic health data and retinal photography were obtained. A non-mydriatic, handheld camera was used (Volk Pictor Plus). Results: Eleven participants (24%) had referral-warranted diabetic retinopathy. There was moderately high inter-rater reliability for our dependent variables: referral status (κ = 0.62, 95% CI 0.42-0.83), retinopathy severity (κ = 0.76, 95% CI 0.55-0.96), and clinically significant macular edema (κ = 0.50, 95% CI 0.25-0.74). Conclusion: Our study confirms that portable handheld cameras can be used to obtain retinal images of sufficient quality for diabetic retinopathy screening even in resource limited environments like Vanuatu. Among this cohort, a relatively high (24%) prevalence of referral-warranted diabetic retinopathy was found in Vanuatu.

Attitudes toward ophthalmology as a prospective career among pre-clinical medical students in China.

BACKGROUND: A questionnaire was developed and administered to 450 medical students at the Xiangya Medical College, Central South University in Changsha, China to understand the attitudes among medical students in China toward different medical specialties and to find the factors that influenced their choice of career in ophthalmology. PARTICIPANTS: Fourth-year medical students in the five-year program and sixth-year medical students in the eight-year program. METHODS: All the students were asked to rate the importance of nine possible factors in choosing a specialty as their vocation and their first ranked future specialty career choice. RESULTS: When asked about the reasons for choosing to go to medical school, the top four reasons are the ability to help patients, interesting and challenging work, prestige, and job stability. When asked about the reasons for choosing a specialty, the top four reasons are the ability to find employment, financial reward, career upward mobility, and professional pressure. About the first career choice of the future specialty, for clinical medicine students, ophthalmology is the fifth ranked choice for clinical medicine students. 5.6% (five-year) and 3.4% (eight-year) of them choose ophthalmology as their top ranked specialty for their career. For anesthesia medicine and oral medicine students, most of them preferred to choose the same specialty as before. 1.5% (anesthesia) and 4.5% (oral) of them chose ophthalmology as their top ranked specialty. CONCLUSIONS: Medical students in China have numerous factors that motivate their choice in a specialty. Ophthalmology is the fifth ranked choice among clinical medicine students.

Renally Clearable Ultraminiature Chain-Like Gold Nanoparticle Clusters for Multimodal Molecular Imaging of Choroidal Neovascularization.

Currently, available gold nanoparticles (GNPs) typically accumulate in the liver and spleen, leading to concerns for their long-term biosafety. To address this long-standing problem, ultraminiature chain-like gold nanoparticle clusters (GNCs) are developed. Via self-assembly of 7-8 nm GNP monomers, GNCs provide redshifted optical absorption and scattering contrast in the near-infrared window. After disassembly, GNCs turn back to GNPs with a size smaller than the renal glomerular filtration size cutoff, allowing their excretion via urine. A one-month longitudinal study in a rabbit eye model demonstrates that GNCs facilitate multimodal molecular imaging of choroidal neovascularization (CNV) in vivo, non-invasively, with excellent sensitivity and spatial resolution. GNCs targeting αv ß3  integrins enhance photoacoustic and optical coherence tomography (OCT) signals from CNV by 25.3-fold and 150%, respectively. With excellent biosafety and biocompatibility demonstrated, GNCs render a first-of-its-kind nanoplatform for biomedical imaging.

Deep learning for automated detection of neovascular leakage on ultra-widefield fluorescein angiography in diabetic retinopathy.

Diabetic retinopathy is a leading cause of blindness in working-age adults worldwide. Neovascular leakage on fluorescein angiography indicates progression to the proliferative stage of diabetic retinopathy, which is an important distinction that requires timely ophthalmic intervention with laser or intravitreal injection treatment to reduce the risk of severe, permanent vision loss. In this study, we developed a deep learning algorithm to detect neovascular leakage on ultra-widefield fluorescein angiography images obtained from patients with diabetic retinopathy. The algorithm, an ensemble of three convolutional neural networks, was able to accurately classify neovascular leakage and distinguish this disease marker from other angiographic disease features. With additional real-world validation and testing, our algorithm could facilitate identification of neovascular leakage in the clinical setting, allowing timely intervention to reduce the burden of blinding diabetic eye disease.

Multimodal imaging of laser-induced choroidal neovascularization in pigmented rabbits.

This study aimed to demonstrate longitudinal multimodal imaging of laser photocoagulation-induced choroidal neovascularization (CNV) in pigmented rabbits. Six Dutch Belted pigmented rabbits were treated with 12 laser lesions in each eye at a power of 300 mW with an aerial diameter spot size of 500 µm and pulse duration of 100 ms. CNV progression was monitored over a period of 4 months using different imaging techniques including color fundus photography, fluorescein angiography (FA), photoacoustic microscopy (PAM), and optical coherence tomography (OCT). All treated eyes developed CNV with a success rate of 100%. The margin and morphology of CNV were detected and rendered in three dimensions using PAM and OCT. The CNV was further distinguished from the surrounding melanin and choroidal vessels using FDA-approved indocyanine green dye-enhanced PAM imaging. By obtaining PAM at 700 nm, the location and density of CNV were identified, and the induced PA signal increased up to 59 times. Immunohistochemistry with smooth muscle alpha-actin (αSMA) antibody confirmed the development of CNV. Laser photocoagulation demonstrates a great method to create CNV in pigmented rabbits. The CNV was stable for up to 4 months, and the CNV area was measured from FA images similar to PAM and OCT results. In addition, this study demonstrates that contrast agent-enhanced PAM imaging allows for precise visualization and evaluation of the formation of new blood vessels in a clinically-relevant animal model of CNV. This laser-induced CNV model can provide a unique technique for longitudinal studies of CNV pathogenesis that can be imaged with multimodal imaging.

Choroidal neovascularization removal with photo-mediated ultrasound therapy.

BACKGROUND: Age-related macular degeneration (AMD) is a major cause of irreversible central vision loss. The main reason for lost vision due to AMD is choroidal neovascularization (CNV). In the clinic, current treatments for CNV include photodynamic therapy, laser photocoagulation, and anti-vascular endothelial growth factor (VEGF) therapy. PURPOSE: This study evaluates a novel treatment technique combining synchronized nanosecond laser pulses and ultrasound bursts, namely photo-mediated ultrasound therapy (PUT) as a potential treatment method for CNV, for its efficacy and safety in the treatment of CNV via the experiments in a clinically-relevant rabbit model in vivo. METHODS: CNV was created by subretinal injection of Matrigel and vascular endothelial growth factor (M&V) in 10 New Zealand white rabbits. Six rabbits were used in the PUT group. In the control groups, two rabbits were treated by laser-only, and two rabbits were treated by ultrasound-only. The treatment efficacy was evaluated through fundus photography and fluorescein angiography (FA) longitudinally for up to 4 weeks. Rabbits were sacrificed for histopathology 3 months after treatment to examine the safety of PUT. RESULTS: The fluorescein leakage on FA was quantified to longitudinally evaluate treatment outcome. Compared with baseline, the relative intensity index was reduced by 26.57% ± 8.66% at 3 days after treatment, 27.24% ± 6.21% at 1 week after treatment, 27.79% ± 2.61% at 2 weeks after treatment, and 32.12% ± 3.23% at 4 weeks after treatment, all with a statistically significant difference of p < 0.01. The comparison between the relative intensity indexes from the two control groups (laser-only treatment and ultrasound-only treatment) did not show any statistically significant difference at all time points. Safety evaluation at 3 months with histopathology demonstrated that the PUT did not result in morphologic changes to the neurosensory retina. CONCLUSIONS: This study introduces PUT for the first time for the treatment of CNV. The results demonstrated good efficacy and safety of PUT to treat CNV in a clinically-relevant rabbit model. With a single session of treatment, PUT can safely reduce the leakage of CNV for at least 1 month after treatment.

USH2A Gene Mutations in Rabbits Lead to Progressive Retinal Degeneration and Hearing Loss.

Purpose: Mutations in USH2A gene are responsible for the greatest proportion of the Usher Syndrome (USH) population, among which more than 30% are frameshift mutations on exon 13. A clinically relevant animal model has been absent for USH2A-related vision loss. Here we sought to establish a rabbit model carrying USH2A frameshift mutation on exon 12 (human exon 13 equivalent). Methods: CRISPR/Cas9 reagents targeting the rabbit USH2A exon 12 were delivered into rabbit embryos to produce an USH2A mutant rabbit line. The USH2A knockout animals were subjected to a series of functional and morphological analyses, including acoustic auditory brainstem responses, electroretinography, optical coherence tomography, fundus photography, fundus autofluorescence, histology, and immunohistochemistry. Results: The USH2A mutant rabbits exhibit hyper-autofluorescent signals on fundus autofluorescence and hyper-reflective signals on optical coherence tomography images as early as 4 months of age, which indicate retinal pigment epithelium damage. Auditory brainstem response measurement in these rabbits showed moderate to severe hearing loss. Electroretinography signals of both rod and cone function were decreased in the USH2A mutant rabbits starting from 7 months of age and further decreased at 15 to 22 months of age, indicating progressive photoreceptor degeneration, which is confirmed by histopathological examination. Conclusions: Disruption of USH2A gene in rabbits is sufficient to induce hearing loss and progressive photoreceptor degeneration, mimicking the USH2A clinical disease. Translational Relevance: To our knowledge, this study presents the first mammalian model of USH2 showing the phenotype of retinitis pigmentosa. This study supports the use of rabbits as a clinically relevant large animal model to understand the pathogenesis and to develop novel therapeutics for Usher syndrome.

Retinal neovascularization as self-organized criticality on ultra-widefield fluorescein angiography imaging of diabetic retinopathy.

BACKGROUND/OBJECTIVES: Do the distributions of surface area of non-perfusion (NP) and neovascularization (NV) on ultra-widefield fluorescein angiography (UWF FA) in patients with diabetic retinopathy (DR) differ significantly? SUBJECTS/METHODS: Inclusion criteria were patients who had a UWF FA taken for DR at the Kellogg Eye Center from January 2009 to May 2018. Exclusion criteria included previous panretinal photocoagulation and significant media opacity (e.g., vitreous haemorrhage or significant cataract). UWF FAs were manually segmented for surface areas of NP and NV. The total areas per patient were organized in a histogram, and logarithmically binned to test against power law and exponential distributions. Then, a computational model was constructed in Python 3.7 to suggest a mechanistic explanation for the observed distributions. RESULTS: Analysis of areas of NV across 189 images demonstrated a superior fit by the least squares method to a power law distribution (p = 0.014) with an R2 fit of 0.9672. Areas of NP over 794 images demonstrated a superior fit with an exponential distribution instead (p = 0.011). When the far periphery was excluded, the R2 fit for the exponential distribution was 0.9618. A computational model following the principles of self-organized criticality (SOC), akin to earthquake and forest fire models, matched these datasets. CONCLUSIONS: These distributions inform what useful statistics may be applied to study of these imaging characteristics. Further, the difference in event distribution between NV and NP suggests that the two phenomena are mechanistically distinct. NV may follow SOC, propagating as a catastrophic event in an unpredictable manner.

A novel model of subretinal edema induced by DL-alpha aminoadipic acid.

In this study we described a new model of subretinal edema induced by single intraocular injection of DL-alpha-aminoadipic acid (DLAAA) that can be employed to study the mechanism of retinal edema and test the efficacy or potential toxicity of treatments. The progression of subretinal edema was evaluated by fundus photography, fluorescein angiography and optical coherence tomography for up to 4 weeks following DLAAA injection. The VEGF, IL-6, TNF-α, Occludin, ZO-1, AQP4, Kir4.1, GFAP and GS levels were examined in DLAAA models by immunostaining, immumohistochemical staining and Western blot. Additionally, bulk RNA-seq was used to detect the mechanism involved in DLAAA-induced retinal Müller cellular injuries. In vivo and vitro assays were further conducted to confirm the sequencing results. Subretinal edema was successfully induced by DLAAA in New Zealand White rabbits (1.29 mg/eye) and C57BL/6 mice (50 or 100 µg/eye). Our results demonstrated that the disruption of blood-retinal-barrier, including vascular hyperpermeability, inflammation, and Müller cell dysfunction of fluid clearance, was involved in subretinal edema formation in the model. Bulk RNA-seq and in vitro studies indicated the activation of p38 MAPK signaling pathway in DLAAA models. This DLAAA-induced subretinal edema model can be used for mechanistic studies or drug screening.

Multimodal In Vivo Imaging of Retinal and Choroidal Vascular Occlusion.

Photoacoustic microscopy (PAM) is an emerging retinal imaging technique that can provide high spatial resolution and high contrast of chorioretinal vessels. PAM is compatible with optical coherence tomography (OCT) and fluorescence imaging, allowing for development of a multimodal imaging system that combines these imaging modalities into one. This study presents a non-invasive, label-free in vivo imaging of retinal and choroidal vascular occlusion using multimodal imaging system, including PAM and OCT. Both retinal vein occlusion (RVO) and choroidal vascular occlusion (CVO) were clearly identified selectively using a spectroscopic PAM imaging. RVO and CVO were created in six rabbits using laser photocoagulation. The dynamic changes of retinal vasculature were observed and evaluated using color fundus photography, fluorescein angiography, OCT, and PAM. The position of RVO and CVO were imaged with different wavelengths ranging from 532 to 600 nm. The data shows that occluded vessels were clearly distinguished from the surrounding retinal vessels on the PAM images. This advanced imaging system is a promising technique for imaging retinal ischemia in preclinical disease models.

In vivo tracking of individual stem cells labeled with nanowire lasers using multimodality imaging.

Emerging cell-based regenerative medicine and stem cell therapies have drawn wide attention in medical research and clinical practice to treat tissue damage and numerous incurable diseases. In vivo observation of the distribution, migration, and development of the transplanted cells is important for both understanding the mechanism and evaluating the treatment efficacy and safety. However, tracking the 3D migration trajectories for individual therapeutic cells in clinically relevant pathological environments remains technically challenging. Using a laser photocoagulation model in living rabbit eyes, this study demonstrates a multimodality imaging technology integrating optical coherence tomography (OCT), fluorescence microscopy (FM), and lasing emission for in vivo longitudinal tracking of the 3D migration trajectories of individual human retinal pigment epithelium cells (ARPE-19) labeled with CdS nanowires. With unique lasing spectra generated from the subtle microcavity differences, the surface-modified nanowires perform as distinct spectral identifiers for labeling individual ARPE-19 cells. Meanwhile, with strong optical scattering and natural fluorescence emission, CdS nanowires also served as OCT and FM contrast agents to indicate the spatial locations of the transplanted ARPE-19 cells. A longitudinal study of tracking individual ARPE-19 cells in rabbit eyes over a duration of 28 days was accomplished. This method could potentially promote an understanding of the pharmacodynamics and pharmacokinetics of implanted cells in the development of cell-based therapies.

Intra- and post-operative risk of retinal breaks during vitrectomy for macular hole and vitreomacular traction.

BACKGROUND/OBJECTIVE: To evaluate the development of intra- and post-operative retinal breaks after pars plana vitrectomy (PPV) for macular hole (MH) and/or vitreomacular traction (VMT). SUBJECTS/METHODS: Medical records of patients who underwent PPV at Kellogg Eye Center between 1/1/2005-6/30/2018, were evaluated in three groups: group 1, MH/VMT (n = 136); group 2, epiretinal membrane (ERM) without VMT (n = 270); and group 3, diagnostic vitrectomy (DV) or vitreous opacities (n = 35). Statistical analyses were conducted using SAS. RESULTS: 20.6% of patients with MH/VMT, 8.5% of patients with ERM, and 5.7% of patients with DV or vitreous opacities had either intra-operative or post-operative breaks. Indication of MH/VMT versus ERM was a significant predictor for this outcome (p = .0112). The incidence of retinal breaks was higher in operations using 23-gauge versus 25-gauge PPV (25.0% vs. 7.4%, p < .0001). CONCLUSIONS: The presence of MH and/or VMT is a significant risk factor for retinal breaks from PPV, as is use of 23-gauge vitrectomy.

Age differential response to bevacizumab therapy in choroidal neovascularization in rabbits.

Choroidal neovascularization (CNV) in young rabbits has been shown to have a rapid, robust response after treatment with bevacizumab, an anti-vascular endothelial growth factor (VEGF) medication. This investigation evaluates an age differential response to bevacizumab in older populations of rabbits using multimodal high resolution molecular imaging. Young (4 months old) and life span (14 months old) rabbits were given subretinal injections of Matrigel and VEGF to produce CNV. All CNV rabbit models were then treated with a bevacizumab intravitreal injection. Rabbits were then monitored longitudinally using photoacoustic microscopy (PAM), optical coherence tomography (OCT), color photography, and fluorescence imaging. Chain-like gold nanoparticle clusters (CGNP) conjugated with tripeptide arginylglycylaspartic acid (RGD) was injected intravenously for molecular imaging. Robust CNV developed in both young and old rabbits. After intravitreal bevacizumab injection, fluorescence signals were markedly decreased 90.13% in the young group. In contrast, old rabbit CNV area decreased by only 10.56% post-bevacizumab treatment. OCT images confirmed a rapid decrease of CNV in the young group. CGNPs demonstrated high PAM signal in old rabbits and minimal PAM signal in young rabbits after bevacizumab, indicating CNV regression. There is a significant difference in response to intravitreal bevacizumab treatment between young and old rabbits with CNV which can be monitored with multimodal molecular imaging. Old rabbits demonstrate significant persistent disease activity. This represents the first large eye model of persistent disease activity of CNV and could serve as the foundation for future investigations into the mechanism of persistent disease activity and the development of novel therapies.