Adult vitreous structure and postnatal changes

In vivo evaluation of a Nano-enabled therapeutic vitreous substitute for the precise delivery of triamcinolone to the posterior segment of the eye

This study focused on the design of a thermoresponsive, nano-enabled vitreous substitute for the treatment of retinal diseases. Synthesis of a hydrogel composed of hyaluronic acid and a poloxamer blend was undertaken. Poly(D,L-lactide-co-glycolide) acid nanoparticles encapsulating triamcinolone acetonide (TA) were synthesised with a spherical morphology and mean diameter of ~ 153 nm. Hydrogel fabrication and nanoparticle loading within the hydrogel was confirmed via physicochemical analysis. Gelation studies indicated that hydrogels formed in nine minutes and 10 min for the unloaded and nanoparticle-loaded hydrogels, respectively. The hydrogels displayed in situ gel formation properties, and rheometric viscoelastic studies indicated the unloaded and loaded hydrogels to have modulus values similar to those of the natural vitreous at 37 °C. Administration of the hydrogels was possible via 26G needles allowing for clinical application and drug release of triamcinolone acetonide from the nanoparticle-loaded hydrogel, which provided sustained in vitro drug release over nine weeks. The hydrogels displayed minimal swelling, reaching equilibrium swelling within 12 h for the unloaded hydrogel, and eight hours for the nanoparticle-loaded hydrogel. Biodegradation in simulated vitreous humour with lysozyme showed < 20% degradation within nine weeks. Biocompatibility of both unloaded and loaded hydrogels was shown with mouse fibroblast and human retinal pigment epithelium cell lines. Lastly, a pilot in vivo study in a New Zealand White rabbit model displayed minimal toxicity with precise, localised drug release behaviour, and ocular TA levels maintained within the therapeutic window for the 28-day investigation period, which supports the potential applicability of the unloaded and nanoparticle-loaded hydrogels as vitreous substitutes that function as drug delivery systems following vitrectomy surgery.

Biomimetic Hyaluronan Binding Biomaterials to Capture the Complex Regulation of Hyaluronan in Tissue Development and Function

Within native ECM, Hyaluronan (HA) undergoes remarkable structural remodeling through its binding receptors and proteins called hyaladherins. Hyaladherins contain a group of tandem repeat sequences, such as LINK domains, BxB7 homologous sequences, or 20-50 amino acid long short peptide sequences that have high affinity towards side chains of HA. The HA binding sequences are critical players in HA distribution and regulation within tissues and potentially attractive therapeutic targets to regulate HA synthesis and organization. While HA is a versatile and successful biopolymer, most HA-based therapeutics have major differences from a native HA molecule, such as molecular weight discrepancies, crosslinking state, and remodeling with other HA binding proteins. Recent studies showed the promise of HA binding domains being used as therapeutic biomaterials for osteoarthritic, ocular, or cardiovascular therapeutic products. However, we propose that there is a significant potential for HA binding materials to reveal the physiological functions of HA in a more realistic setting. This review is focused on giving a comprehensive overview of the connections between HA's role in the body and the potential of HA binding material applications in therapeutics and regenerative medicine. We begin with an introduction to HA then discuss HA binding molecules and the process of HA binding. Finally, we discuss HA binding materials anf the future prospects of potential HA binding biomaterials systems in the field of biomaterials and tissue engineering.

BCLA CLEAR presbyopia: Mechanism and optics

With over a billion adults worldwide currently affected, presbyopia remains a ubiquitous, global problem. Despite over a century of study, the precise mechanism of ocular accommodation and presbyopia progression remains a topic of debate. Accordingly, this narrative review outlines the lenticular and extralenticular components of accommodation together with the impact of age on the accommodative apparatus, neural control of accommodation, models of accommodation, the impact of presbyopia on retinal image quality, and both historic and contemporary theories of presbyopia.

Clinical Characteristics and Surgical Outcomes of Patients Undergoing Pars Plana Vitrectomy for Proliferative Diabetic Retinopathy

OBJECTIVE

To evaluate clinical characteristics impacting surgical outcomes of patients undergoing pars plana vitrectomy (PPV) for complications of proliferative diabetic retinopathy (PDR).

DESIGN

Retrospective consecutive observational case series of patients at a large county hospital in Dallas, Texas, from 2014 to 2019.

SUBJECTS

Seven hundred thirty-two patients (933 eyes) undergoing PPV for PDR complications.

METHODS

Collected data included demographics, surgical indication, adjuvant therapies, intraoperative course, complications, and best corrected visual acuity (BCVA). Patients with < 6 months of follow-up were excluded. Best corrected visual acuity was converted to logarithm of the minimum angle of resolution for analysis. Statistics performed included t test, analysis of variance, and multivariate analyses.

MAIN OUTCOME MEASURES

Postoperative BCVA, primary anatomic success rate, and postoperative complications.

RESULTS

Three hundred ninety-three patients were male (509 eyes; 54.5%) with an average age of 52 years. Postoperative BCVA at 6 months was significantly different among surgical indications: 0.79 versus 0.77 versus 1.20 (P < 0.0001) for vitreous hemorrhage (VH), vitreomacular interface abnormalities, and tractional retinal detachment (TRD), respectively. Adjuvant preoperative therapy with panretinal photocoagulation (PRP) versus no PRP (0.95 vs. 1.25; P < 0.001) and insulin versus no insulin (0.99 vs. 1.17; P < 0.01) were associated with improved vision. Iatrogenic breaks were associated with decreased postoperative vision (1.40 vs. 0.88; P < 0.001). The primary anatomic success rate for TRD was 85% (495 eyes). Combined TRD/RRD (tractional and rhegmatogenous retinal detachment) was associated with a lower success rate compared with macula-on/macula-off TRD, with odds ratios of 0.36, 0.46, and 0.53, respectively. Patients experiencing recurrent detachment postsurgery had worse preoperative visual acuity (VA) (1.93 vs. 1.63; P < 0.01) and were younger (47.6 vs. 50.0; P = 0.02). Postoperative complications occurred in 699 eyes (75%), with VH (498 eyes, 53%), cataract (465, 50%), and elevated intraocular pressure (149, 16%) being the most common. Two hundred thirty-six eyes (25%) required a second PPV operation. Endophthalmitis (1 eye; <1%) and choroidal detachment (5 eyes; <1%) were rare.

CONCLUSIONS

In this retrospective series analyzing surgical outcomes among patients with complications from PDR, vitrectomy led to improved vision on average, with a meaningful proportion of patients receiving additional surgical intervention. Surgical indication, presenting VA, age, and adjuvant therapies appeared to impact outcomes.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

A COMPARATIVE ANALYSIS OF TRAUMATIC RETINAL DETACHMENT AFTER OPEN AND CLOSED GLOBE INJURIES IN CHILDREN

PURPOSE

Pediatric traumatic retinal detachment (RD) resulting from open globe injuries (OGIs) or closed globe injuries (CGIs) presents unique challenges due to complexity often resulting in lifelong sequelae. This study compares pediatric traumatic RD outcomes and prognostic factors following OGI and CGI.

METHODS

A retrospective analysis reviewed 47 cases of pediatric traumatic RD in children (age <18 years), who underwent RD surgery between 2002 and 2021. Among them, 25 cases were caused by CGI and 22 cases by OGI. Demographics, RD characteristics, surgical procedures, and anatomical and functional results were assessed. Predictive factors for visual outcomes were investigated.

RESULTS

In the CGI group, mean (±SD) age was 11 years ± 4 years, and 10 years ± 5 years in the OGI group. Closed globe injury traumatic RD had significantly better preoperative (CGI: logarithm of the minimum angle of resolution 1.39 ± 0.19 (mean ± standard error); OGI: logarithm of the minimum angle of resolution 2.12 ± 0.20) and follow-up (CGI: logarithm of the minimum angle of resolution 0.94 ± 0.19; OGI: logarithm of the minimum angle of resolution 1.85 ± 0.20) best-corrected visual acuity (BCVA) ( P < 0.05). Initial BCVA improvement was observed in CGI only. In multivariable analysis, prognostic factors for favorable BCVA outcomes included higher preoperative BCVA, older age, and absence of proliferative vitreoretinopathy ( P < 0.05).

CONCLUSION

Visual prognosis for pediatric traumatic RD remains limited, favoring CGI cases compared with OGI. Baseline BCVA emerged as a major determinant of final visual acuity. Tailored management approaches can optimize treatment results.

Cationic-motif-modified exosomes for mRNA delivery to retinal photoreceptors

Topical treatment of vitreoretinal diseases remains a challenge due to slow corneal uptake and systemic clearance. Exosomes are emerging nanocarriers for drug delivery due to biocompatibility and cellular targeting properties. To apply them for retinal targeting via the topical route, exosomes must traverse various ocular barriers including the cornea, lens, vitreous humor (VH), and the retina itself. Here we engineered high-purity milk-derived exosomes by anchoring arginine-rich cationic motifs via PEG2000 lipid insertion on their surface. Modification enabled exosomes to use weak-reversible electrostatic interactions with anionic glycosaminoglycan (GAG) and water content of the tissue to enhance their transport rate and retention. Addition of cationic motifs neutralized the anionic surface charge of exosomes (-24 to -2 mV) without impacting size or morphology. Cationic-motif-modified exosomes exhibited two-fold faster steady state diffusivity through bovine corneas compared to unmodified exosomes. Fluorescence recovery after photobleaching confirmed that cationic-motif-modified exosomes can diffuse through VH without steric hindrance. In healthy VH, cationic-motif-modified exosomes demonstrated stronger binding resulting in three-fold lower average diffusivity that enhanced by six-fold in 50% GAG-depleted VH recapitulating advanced liquefaction. Cationic-motif-modified exosomes penetrated through the full-thickness of porcine retinal explants resulting in ten-fold higher uptake in photoreceptors and three-fold greater transfection with encapsulated eGFP mRNA compared to unmodified exosomes. Cationic-motif-modified exosomes are safe to use as they did not adversely affect the mechanical swelling properties of the cornea or lens nor impact retinal cell viability. Cationic-motif-modified exosomes, therefore, offer themselves as a cell-free nanocarrier platform for gene delivery to retinal photoreceptors potentially via the topical route.

A journey through the world of vitreous

Vitreous, one of the largest components of the human eye, mostly contains water. Despite decades of studying the vitreous structure, numerous unanswered questions still remain, fueling ongoing active research. We attempt to provide a comprehensive overview of the current understanding of the development, morphology, biochemical composition, and function of the vitreous. We emphasize the impact of the vitreous structure and composition on the distribution of drugs. Fast-developing imaging technologies, such as modern optical coherence tomography, unlocked multiple new approaches, offering the potential for in vivo study of the vitreous structure. They allowed to analyze in vivo a range of vitreous structures, such as posterior precortical vitreous pockets, Cloquet canal, channels that interconnect them, perivascular vitreous fissures, and cisterns. We provide an overview of such imaging techniques and their principles and of some challenges in visualizing vitreous structures. Finally, we explores the potential of combining the latest technologies and machine learning to enhance our understanding of vitreous structures.

The Importance of Posterior Hyaloid Removal in a Case of Vitrectomy for Floaters in High Myopia

A 61-year-old Malaysian Chinese man who has high myopia complained of both eye floaters. Spectral-domain optical coherence tomography (SD-OCT) of the macula showed bilateral posterior staphyloma with right eye (RE) foveoschisis without macula detachment, which had been stable for a seven-year follow-up. When bilateral YAG laser vitreolysis could not alleviate his symptoms, he underwent pars plana vitrectomy with the inducement of posterior vitreous detachment, first in the left eye, followed by the RE one month later. The best-corrected visual acuity for both eyes was 6/6, N5 two months postoperatively, and he was asymptomatic for floaters. However, six months postoperatively, he complained of metamorphopsia and worsening RE vision. Repeat OCT showed worsening of the foveoschisis bilaterally with left foveal detachment. The patient had to undergo a repeat vitrectomy with peeling of the internal limiting membrane (ILM) in bilateral eyes, which successfully restored his foveal architecture and alleviated his symptoms. This article highlights theimportance of preoperative OCT assessment of the fovea in patients undergoing vitrectomy for floaters, as staining and complete removal of posterior hyaloid with ILM peeling during vitrectomy may mitigate the progression of foveoschisis after core vitrectomy for floaters in myopic patients.

Functional OCT reveals anisotropic changes of retinal flicker-evoked vasodilation

The purpose of this study is to verify the effect of anisotropic property of retinal biomechanics on vasodilation measurement. A custom-built optical coherence tomography (OCT) was used for time-lapse imaging of flicker stimulation-evoked vessel lumen changes in mouse retinas. A comparative analysis revealed significantly larger (18.21%) lumen dilation in the axial direction compared to the lateral (10.77%) direction. The axial lumen dilation predominantly resulted from the top vessel wall movement toward the vitreous direction, whereas the bottom vessel wall remained stable. This observation indicates that the traditional vasodilation measurement in the lateral direction may result in an underestimated value.

The effect of axial length on pseudophakic retinal detachment

PURPOSE

The purpose of the study was to analyse the surgical management and outcome regarding axial length in the population affected by pseudophakic retinal detachment (PRD) 2015-2020.

METHOD

The patients included were from an observational cohort study of patients undergoing cataract surgery in the region of Skåne during 2015-2017. Data were retrieved from the Swedish National Cataract Register and cross-referenced with cases of PRD in the same region from 2015 to 2020. The surgical method used and findings at follow-up were recorded. The patients were stratified according to axial length (AL) to <25 mm, 25 ≤ n < 26.5 mm and ≥26.5 mm. The main outcome was primary success with one surgery apart from silicone oil removal. The secondary outcome was postoperative visual acuity.

RESULTS

In the whole study group of 58 624 cases, complete follow-up data were available for 288 eyes. The median follow-up time was 324 days, and primary operation was successful in 82.9% of these cases. The median visual acuity was 0.31 (LogMAR). In the stratification those with AL < 25 mm had a primary success of 75.8%, AL 25 ≤ n < 26.5 mm of 87.9% and ≥26.5 mm of 95.8%.

CONCLUSIONS

The primary anatomical success was 82.9% in the whole group of PRD but with stratification they had an increasing number of primary success with longer AL.

Ultra-Widefield-Guided Swept-Source OCT Findings of Peripheral Vitreoretinal Abnormality in Young Myopes

PURPOSE

To evaluate the ultra-widefield fundus photography (UWF-FP)-guided swept-source OCT (SS-OCT) images of peripheral vitreoretinal abnormality (PVRA) in young asymptomatic myopes.

DESIGN

Cross-sectional, single-center study.

PARTICIPANTS

A total of 1966 eyes of 983 consecutive patients aged 18 to 42 years with refractive error in the spherical equivalent of < 0 diopters (D) who visited KEYE Eye Center, Seoul, Republic of Korea, for refractive surgery.

METHODS

The prevalence of PVRA and their characteristics, including shape, location, presence of pigmentation, membrane, retinal breaks, and detachment, were evaluated. A logistic regression analysis was done to evaluate the risk factors of PVRA and the risk of retinal breaks or detachment among eyes with PVRA.

RESULTS

Among 1966 eyes, 317 (16.1%) had PVRA, and 182 (57.4%) and 135 (42.6%) had focal and linear lesions, respectively. The risk of PVRA was increased with axial length of the eyes (odds ratio [OR], 1.238, 95% confidence interval [CI], 1.112-1.379, P < 0.001), corneal astigmatism (OR, 1.320, 95% CI, 1.148-1.519, P < 0.001), presence of discrete margins of different retinal reflectivity (DMDRR; indicating outer retinal disruption from abnormal vitreoretinal traction) (OR, 1.751, 95% CI, 1.334-2.300, P < 0.001), and posterior vitreous detachment (PVD) at the posterior pole of the retina (OR, 1.833, 95% CI, 1.352-2.485, P < 0.001). Among eyes with PVRA, patient age (OR, 1.063, 95% CI, 1.008-1.121, P = 0.025), linear lesions (OR, 15.234, 95% CI, 7.891-29.407, P < 0.001), and multiple lesions (OR, 3.432, 95% CI, 1.780-6.620, P < 0.001) were independently associated with the presence of retinal breaks or detachment.

CONCLUSIONS

The follow-up for PVRA among young myopes should be personalized on the basis of their ocular characteristics, including asymmetric ocular expansion (axial length and astigmatism) and vitreoretinal interface status. The treatment plan for PVRA eyes should emphasize the greater risk of retinal breaks and detachment with increasing age and the presence of linear and multiple lesions.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Forward Light Scattering of the Vitreous Gel After Enzymatic Aging: An In Vitro Model to Study Vitreous Opacification

Purpose

Symptomatic vitreous opacifications, so-called floaters, are difficult to objectively assess majorly limiting the possibility of in vitro studies. Forward light scattering was found previously to be increased in eyes with symptomatic floaters. Using an objective setup to measure forward light scattering, we studied the effects of enzymatically digesting the components of the vitreous body on straylight to develop an in vitro model of vitreous opacifications.

Methods

Fifty-seven porcine vitreous bodies were digested using hyaluronidase, collagenase, trypsin, and bromelain, as well as using a combination of hyaluronidase + collagenase and hyaluronidase + bromelain. A modified C-Quant setup was used to objectively assess forward light scattering.

Results

Depletion of hyaluronic acid majorly increased vitreous straylight (mean increase 34.4 deg2/sr; P = 0.01), whereas primarily digesting the vitreous gel with collagenase or trypsin did not significantly affect straylight. When collagenase or bromelain is applied in hyaluronic acid depleted vitreous gels, the increase in forward light scattering is reversed partially.

Conclusions

The age-related loss of hyaluronic acid primarily drives the increase in vitreous gel straylight induced by conglomerates of collagen. This process can be reversed partially by digesting collagen. This in vitro model allows the objective quantification and statistical comparison of straylight burden caused by vitreous opacities and, thus, can serve as a first testing ground for pharmacological therapies, as demonstrated with bromelain.

Desired properties of polymeric hydrogel vitreous substitute

Vitreous replacement is a commonly employed method for treating a range of ocular diseases, including posterior vitreous detachment, complex retinal detachment, diabetic retinopathy, macular hole, and ocular trauma. Various clinical substitutes for vitreous include air, expandable gas, silicone oil, heavy silicone oil, and balanced salt solution. However, these substitutes have drawbacks such as short retention time, cytotoxicity, high intraocular pressure, and the formation of cataracts, rendering them unsuitable for long-term treatment. Polymeric hydrogels possess the potential to serve as ideal vitreous substitutes due to their structure-mimicking to natural vitreous and adjustable mechanical properties. Replacement with hydrogels as the tamponade can help maintain the shape of the eyeball, apply pressure to the detached retina, and ensure the metabolic transport of substances without impairing vision. This literature review examines the required properties of artificial vitreous, including the optical properties, rheological properties, expansive force action, and physiological and biochemical functions of chemically and physically crosslinked hydrogels. The strategies for enhancing the biocompatibility and injectability of hydrogels are also summarized and discussed. From a clinical ophthalmology perspective, this paper presents the latest developments in vitreous replacement, providing clinicians with a comprehensive understanding of hydrogel clinical applications, which offers guidance for future design directions and methodologies for hydrogel development.

Stability of ranibizumab during continuous delivery from the Port Delivery Platform

The Port Delivery System with ranibizumab (PDS) is an innovative intraocular drug delivery system that has the potential to reduce treatment burden in patients with retinovascular diseases. The Port Delivery Platform (PD-P) implant is a permanent, indwelling device that can be refilled in situ through a self-sealing septum and is designed to continuously deliver ranibizumab by passive diffusion through a porous titanium release control element. We present results for the studies carried out to characterize the stability of ranibizumab for use with the PD-P. Simulated administration, in vitro release studies, and modeling studies were performed to evaluate the compatibility of ranibizumab with the PD-P administration components, and degradation and photostability in the implant. Simulated administration studies demonstrated that ranibizumab was highly compatible with the PD-P administration components (initial fill and refill needles) and commercially available administration components (syringe, transfer needle, syringe closure). Subsequent simulated in vitro release studies examining continuous delivery for up to 12 months in phosphate buffered saline, a surrogate for human vitreous, showed that the primary degradation products of ranibizumab were acidic variants. The presence of these variants increased over time and potency remained high. The stability attributes of ranibizumab were consistent across multiple implant refill-exchanges. Despite some degradation within the implant, the absolute mass of variants released daily from the implant was low due to the continuous release mechanism of the implant. Simulated light exposure within the implant resulted in small increases in the relative amount of ranibizumab degradants compared with those seen over 6 months.

Age-related changes on physicochemical properties of the artificial vitreous humor: A practical tool for enhancing ex vivo studies

The vitreous humor (VH) is a hydrophilic, jelly-like ocular fluid, which is located in the posterior chamber of the eye. The rheological, structural, and chemical properties of VH change significantly during aging, which further causes eye-associated diseases and could be a potential indicator for various diseases. In this study, artificial VH (A-VH) samples were created by taking into account different age groups to observe age-related changes in the physicochemical properties of these samples. This study aimed to measure the physicochemical properties of age-dependently prepared A-VH samples to determine the changes with aging in the physicochemical properties of A-VH samples. Phosphate-buffered saline (PBS)-based A-VH samples were prepared in three types representing adult, middle-aged, and elder individuals. Age-related changes in physicochemical properties (surface tension, osmolality, pH, relative viscosity, density, and refractive index) were analyzed by related equipment. The A-VH samples, prepared using PBS, showed strong similarity to authentic VH in terms of physicochemical properties. While the age-related changes studies have revealed some discrepancies between age-dependently prepared A-VH samples in terms of surface tension, osmolality, relative viscosity, and pH with high correlation coefficients (r2 > 0,94), density and refractive index values did not show any significant differences and correlation between types of A-VH representing 3 age groups. In conclusion, age-dependent A-VH samples were created successfully to use ex vivo method development studies, and the influence of aging on the physicochemical properties of VH was demonstrated as well.

Pathogenesis of Common Ocular Diseases: Emerging Trends in Extracellular Matrix Remodeling

The prevalence of visual impairments in human societies is worrying due to retinopathy complications of several chronic diseases such as diabetes, cardiovascular diseases, and many more that are on the rise worldwide. Since the proper function of this organ plays a pivotal role in people's quality of life, identifying factors affecting the development/exacerbation of ocular diseases is of particular interest among ophthalmology researchers. The extracellular matrix (ECM) is a reticular, three-dimensional (3D) structure that determines the shape and dimensions of tissues in the body. The ECM remodeling/hemostasis is a critical process in both physiological and pathological conditions. It consists of ECM deposition, degradation, and decrease/increase in the ECM components. However, disregulation of this process and an imbalance between the synthesis and degradation of ECM components are associated with many pathological situations, including ocular disorders. Despite the impact of ECM alterations on the development of ocular diseases, there is not much research conducted in this regard. Therefore, a better understanding in this regard, can pave the way toward discovering plausible strategies to either prevent or treat eye disorders. In this review, we will discuss the importance of ECM changes as a sentimental factor in various ocular diseases based on the research done up to now.

The genetics and disease mechanisms of rhegmatogenous retinal detachment

Rhegmatogenous retinal detachment (RRD) is a sight threatening condition that warrants immediate surgical intervention. To date, 29 genes have been associated with monogenic disorders involving RRD. In addition, RRD can occur as a multifactorial disease through a combined effect of multiple genetic variants and non-genetic risk factors. In this review, we provide a comprehensive overview of the spectrum of hereditary disorders involving RRD. We discuss genotype-phenotype correlations of these monogenic disorders, and describe genetic variants associated with RRD through multifactorial inheritance. Furthermore, we evaluate our current understanding of the molecular disease mechanisms of RRD-associated genetic variants on collagen proteins, proteoglycan versican, and the TGF-β pathway. Finally, we review the role of genetics in patient management and prevention of RRD. We provide recommendations for genetic testing and prophylaxis of at-risk patients, and hypothesize on novel therapeutic approaches beyond surgical intervention.

Epigenetic mechanisms of non-retinal components of the aging eye and novel therapeutic strategies

The eye is a complex organ composed of various cell types, each serving a unique purpose. However, aging brings about structural and functional changes in these cells, leading to discomfort and potential pathology. Alterations in gene expression, influenced by aging and environmental factors, significantly affect cell structure and function. Epigenetics, a field focused on understanding the correlation between changes in gene expression, cell function, and environmental factors, plays a crucial role in unraveling the molecular events responsible for age-related eye changes. This prompts the possibility of developing epigenetic strategies to intervene in these changes or reinstate proper molecular activities. Indeed, research has demonstrated that epigenetic modifications, including DNA methylation, histone modification, and non-coding RNAs, are closely associated with age-related alterations in gene expression and cell function. This review aims to compile and synthesize the most recent body of evidence supporting the role of epigenetics in age-related alterations observed in various components of the eye. Specifically, it focuses on the impact of epigenetic changes in the ocular surface, tear film, aqueous humor, vitreous humor, and lens. Furthermore, it highlights the significant advancements that have been made in the field of epigenetic-based experimental therapies, specifically focusing on their potential for treating pathological conditions in the aging eye.

Challenges and strategies for ocular posterior diseases therapy via non-invasive advanced drug delivery

Posterior segment diseases, such as age-related macular degeneration (AMD) and diabetic retinopathy (DR) are vital factor that seriously threatens human vision health and quality of life, the treatment of which poses a great challenge to ophthalmologists and ophthalmic scientists. In particular, ocular posterior drug delivery in a non-invasive manner is highly desired but still faces many difficulties such as rapid drug clearance, limited permeability and low drug accumulation at the target site. At present, many novel non-invasive topical ocular drug delivery systems are under development aiming to improve drug delivery efficiency and biocompatibility for better therapy of posterior segment oculopathy. The purpose of this review is to present the challenges in the noninvasive treatment of posterior segment diseases, and to propose strategies to tackle these bottlenecks. First of all, barriers to ocular administration were introduced based on ocular physiological structure and behavior, including analysis and discussion on the influence of ocular structures on noninvasive posterior segment delivery. Thereafter, various routes of posterior drug delivery, both invasive and noninvasive, were illustrated, along with the respective anatomical obstacles that need to be overcome. The widespread and risky application of invasive drug delivery, and the need to develop non-invasive local drug delivery with alternative to injectable therapy were described. Absorption routes through topical administration and strategies to enhance ocular posterior drug delivery were then discussed. As a follow-up, an up-to-date research advances in non-invasive delivery systems for the therapy of ocular fundus lesions were presented, including different nanocarriers, contact lenses, and several other carriers. In conclusion, it seems feasible and promising to treat posterior oculopathy via non-invasive local preparations or in combination with appropriate devices.

The Impact of Serum Protein Adsorption on PEGylated NT3-BDNF Nanoparticles-Distribution, Protein Release, and Cytotoxicity in a Human Retinal Pigmented Epithelial Cell Model

The adsorption of biomolecules on nanoparticles' surface ultimately depends on the intermolecular forces, which dictate the mutual interaction transforming their physical, chemical, and biological characteristics. Therefore, a better understanding of the adsorption of serum proteins and their impact on nanoparticle physicochemical properties is of utmost importance for developing nanoparticle-based therapies. We investigated the interactions between potentially therapeutic proteins, neurotrophin 3 (NT3), brain-derived neurotrophic factor (BDNF), and polyethylene glycol (PEG), in a cell-free system and a retinal pigmented epithelium cell line (ARPE-19). The variance in the physicochemical properties of PEGylated NT3-BDNF nanoparticles (NPs) in serum-abundant and serum-free systems was studied using transmission electron microscopy, atomic force microscopy, multi-angle dynamic, and electrophoretic light scattering. Next, we compared the cellular response of ARPE-19 cells after exposure to PEGylated NT3-BDNF NPs in either a serum-free or complex serum environment by investigating protein release and cell cytotoxicity using ultracentrifuge, fluorescence spectroscopy, and confocal microscopy. After serum exposure, the decrease in the aggregation of PEGylated NT3-BDNF NPs was accompanied by increased cell viability and BDNF/NT3 in vitro release. In contrast, in a serum-free environment, the appearance of positively charged NPs with hydrodynamic diameters up to 900 nm correlated with higher cytotoxicity and limited BDNF/NT3 release into the cell culture media. This work provides new insights into the role of protein corona when considering the PEGylated nano-bio interface with implications for cytotoxicity, NPs' distribution, and BDNF and NT3 release profiles in the in vitro setting.

Therapeutic potential of Bacillus phage lysin PlyB in ocular infections

Bacteriophage lytic enzymes (i.e., phage lysins) are a trending alternative for general antibiotics to combat growing antimicrobial resistance. Gram-positive Bacillus cereus causes one of the most severe forms of intraocular infection, often resulting in complete vision loss. It is an inherently β-lactamase-resistant organism that is highly inflammogenic in the eye, and antibiotics are not often beneficial as the sole therapeutic option for these blinding infections. The use of phage lysins as a treatment for B. cereus ocular infection has never been tested or reported. In this study, the phage lysin PlyB was tested in vitro, demonstrating rapid killing of vegetative B. cereus but not its spores. PlyB was also highly group specific and effectively killed the bacteria in various bacterial growth conditions, including ex vivo rabbit vitreous (Vit). Furthermore, PlyB demonstrated no cytotoxic or hemolytic activity toward human retinal cells or erythrocytes and did not trigger innate activation. In in vivo therapeutic experiments, PlyB was effective in killing B. cereus when administered intravitreally in an experimental endophthalmitis model and topically in an experimental keratitis model. In both models of ocular infection, the effective bactericidal property of PlyB prevented pathological damage to ocular tissues. Thus, PlyB was found to be safe and effective in killing B. cereus in the eye, greatly improving an otherwise devastating outcome. Overall, this study demonstrates that PlyB is a promising therapeutic option for B. cereus eye infections.IMPORTANCEEye infections from antibiotic-resistant Bacillus cereus are devastating and can result in blindness with few available treatment options. Bacteriophage lysins are an alternative to conventional antibiotics with the potential to control antibiotic-resistant bacteria. This study demonstrates that a lysin called PlyB can effectively kill B. cereus in two models of B. cereus eye infections, thus treating and preventing the blinding effects of these infections.

Extracellular-Matrix Mechanics Regulate the Ocular Physiological and Pathological Activities

The extracellular matrix (ECM) is a noncellular structure that plays an indispensable role in a series of cell life activities. Accumulating studies have demonstrated that ECM stiffness, a type of mechanical forces, exerts a pivotal influence on regulating organogenesis, tissue homeostasis, and the occurrence and development of miscellaneous diseases. Nevertheless, the role of ECM stiffness in ophthalmology is rarely discussed. In this review, we focus on describing the important role of ECM stiffness and its composition in multiple ocular structures (including cornea, retina, optic nerve, trabecular reticulum, and vitreous) from a new perspective. The abnormal changes in ECM can trigger physiological and pathological activities of the eye, suggesting that compared with different biochemical factors, the transmission and transduction of force signals triggered by mechanical cues such as ECM stiffness are also universal in different ocular cells. We expect that targeting ECM as a therapeutic approach or designing advanced ECM-based technologies will have a broader application prospect in ophthalmology.

Multimodal imaging of a micro-anatomical structure in the vitreous base

BACKGROUND

To describe an ultrastructure in the vitreous base (VB) and its micro-anatomical characteristics by multimodal imaging.

METHODS

Light and transmission electron microscopy of the VB were performed on specimens from post-trauma eyes and one healthy donor eye. Intra-operative fundus images associated with VB abnormalities were captured from 4 cases, including 2 retinal detachment (RD) with PVR eyes and 2 post-trauma eyes. Images during micro-anatomical observation of the three specimens were analyzed along with the fundus images obtained during vitrectomy.

RESULTS

Densely packed collagen fibers were observed by light microscopy between the pigment epithelium layer and uveal tissue within the ora serrata region in specimen 1 and the post-mortem healthy eye, respectively. A similar structure was also observed by transmission electron microscopy interior to the pigment epithelium layer and exposed to the vitreous cavity in specimen 2. The collagen fibers, which were termed ciliary body-choroid-retina (CB-C-R) connector, connects to the vitreous fibers interiorly, ciliary epithelium anteriorly, peripheral retina posteriorly, and uveal tissue exteriorly. The three different RD boundaries related to the posterior edge of the VB, ora serrata, and ciliary epithelium are demonstrated with the micro-anatomical characteristics of the CB-C-R connector.

CONCLUSION

The CB-C-R connector exists deep in the VB.

Quantification of Retinal Vein and Artery Trajectories Using Second-Order Polynomial Equation in Eyes with Vitreomacular Traction

BACKGROUNDS

To measure the degree of curvature of the retinal artery trajectory (RAT) and retinal vein trajectory (RVT) in the eyes of patients with vitreomacular traction (VMT) and compare them with their healthy fellow eyes.

METHODS

This was a retrospective, cross-sectional, case-control study of 58 eyes of 29 patients with unilateral VMT. The participants were divided into two groups. Group 1 VMT was defined as having only morphological changes, while group 2 VMT was defined as morphological changes accompanied by the presence of a cyst or hole to quantify the severity of the disease. The RATs and RVTs were assessed from the color fundus photographs using the ImageJ program. The fundus photographs were rotated 90 degrees. The course of the retinal arteries and veins were marked on a color fundus photograph and fitted to a second-degree polynomial curve (ax[x]/100+bx+c). The coefficient ''a'' was the width and steepness of the trajectories. The comparison between the RAT and RVT of vitreomacular traction and healthy fellow eyes was investigated and the association between the RAT and RVT and the severity of disease were determined using the Image J program.

RESULTS

Eleven subjects were male, and 18 subjects were female. The mean ± SD age was 70.6 ± 7.6 years. Eighteen of the eyes had VMT in the right and 11 of the eyes had VMT in the left eye. Eleven eyes were in group 1 and 18 eyes were in group 2. Axial length (AL) was similar between the two groups (22.63 ± 1.20 mm vs 22.45 ± 1.45 mm p=0.83). (Table 1) The mean RAT was 0.60±0.18 in eyes with VMT and 0.51±0.17in healthy eyes (p=0.063). The mean RVT was 0.74±0.24 in eyes with VMT and 0.62±0.25 in healthy eyes for the whole group (p=0.02). In group 1, the mean RVT of the eyes with VMT was statistically significantly higher than the healthy eyes (p=0.014). There was not any statistically significant difference for the other parameters evaluated between eyes with VMT and healthy eyes according to the groups and the whole group. (Table 2-3-4) CONCLUSION: Unlike other vitreoretinal interface diseases such as epiretinal membrane and macular hole, VMT may be characterized by a narrower RVT, which is characterized by a larger "a" value.

Development of Novel Small-Molecule Activators of Pyruvate Kinase Muscle Isozyme 2, PKM2, to Reduce Photoreceptor Apoptosis

Treatment options are lacking to prevent photoreceptor death and subsequent vision loss. Previously, we demonstrated that reprogramming metabolism via the pharmacologic activation of PKM2 is a novel photoreceptor neuroprotective strategy. However, the features of the tool compound used in those studies, ML-265, preclude its advancement as an intraocular, clinical candidate. This study sought to develop the next generation of small-molecule PKM2 activators, aimed specifically for delivery into the eye. Compounds were developed that replaced the thienopyrrolopyridazinone core of ML-265 and modified the aniline and methyl sulfoxide functional groups. Compound 2 demonstrated that structural changes to the ML-265 scaffold are tolerated from a potency and efficacy standpoint, allow for a similar binding mode to the target, and circumvent apoptosis in models of outer retinal stress. To overcome the low solubility and problematic functional groups of ML-265, compound 2's efficacious and versatile core structure for the incorporation of diverse functional groups was then utilized to develop novel PKM2 activators with improved solubility, lack of structural alerts, and retained potency. No other molecules are in the pharmaceutical pipeline for the metabolic reprogramming of photoreceptors. Thus, this study is the first to cultivate the next generation of novel, structurally diverse, small-molecule PKM2 activators for delivery into the eye.

How can machine learning and multiscale modeling benefit ocular drug development?

The eyes possess sophisticated physiological structures, diverse disease targets, limited drug delivery space, distinctive barriers, and complicated biomechanical processes, requiring a more in-depth understanding of the interactions between drug delivery systems and biological systems for ocular formulation development. However, the tiny size of the eyes makes sampling difficult and invasive studies costly and ethically constrained. Developing ocular formulations following conventional trial-and-error formulation and manufacturing process screening procedures is inefficient. Along with the popularity of computational pharmaceutics, non-invasive in silico modeling & simulation offer new opportunities for the paradigm shift of ocular formulation development. The current work first systematically reviews the theoretical underpinnings, advanced applications, and unique advantages of data-driven machine learning and multiscale simulation approaches represented by molecular simulation, mathematical modeling, and pharmacokinetic (PK)/pharmacodynamic (PD) modeling for ocular drug development. Following this, a new computer-driven framework for rational pharmaceutical formulation design is proposed, inspired by the potential of in silico explorations in understanding drug delivery details and facilitating drug formulation design. Lastly, to promote the paradigm shift, integrated in silico methodologies were highlighted, and discussions on data challenges, model practicality, personalized modeling, regulatory science, interdisciplinary collaboration, and talent training were conducted in detail with a view to achieving more efficient objective-oriented pharmaceutical formulation design.

Exploring High-Precision Non-Assembly Mechanisms: Design of a Vitrectome Mechanism for Eye Surgery

A vitrectome is a commonly used instrument in eye surgery, which is used to cut and aspirate the vitreous body out of the eye. The mechanism of the vitrectome consists of miniature components that need to be assembled by hand due to their size. Non-assembly 3D printing, in which fully functional mechanisms can be produced in a single production step, can help create a more streamlined production process. We propose a vitrectome design based on a dual-diaphragm mechanism, which can be produced with minimal assembly steps using PolyJet printing. Two different diaphragm designs were tested to fulfill the requirements of the mechanism: a homogenous design based on 'digital' materials and a design using an ortho-planar spring. Both designs were able to fulfill the required displacement for the mechanism of 0.8 mm, as well as cutting forces of at least 8 N. The requirements for the cutting speed of the mechanism of 8000 RPM were not fulfilled by both designs, since the viscoelastic nature of the PolyJet materials resulted in a slow response time. The proposed mechanism does show promise to be used in vitrectomy; however, we suggest that more research into different design directions is required.

Ocular Pharmacokinetic Properties of Intravitreally Injected Aflibercept in Rabbits After Using Brinzolamide/Timolol Eye Drops

Purpose: To investigate the ocular pharmacokinetic properties of intravitreally injected aflibercept in rabbits after using brinzolamide 1%/timolol maleate 0.5% fixed-combination eye drops. Methods: The right eye of 5 rabbits was topically administered 30 μL of brinzolamide and timolol maleate eye drops twice a day (q12h). The 2 eyes of each rabbit were injected with 1.0 mg (0.025 cc) of aflibercept on the 2nd day after instilling the eye drops. The intraocular pressure of the rabbits was measured before injection and sampling. The aqueous humor was drawn at 1, 3, 7, 14, 21, and 28 days. Aflibercept concentrations in aqueous humor and vitreous humor (28 days) were measured by enzyme-linked immunosorbent assay. Results: The aflibercept aqueous concentrations in the right eye at days 7, 14, 21, and 28 after injection were all significantly higher than those in the left eye (P > 0.05, n = 5). The peak aqueous concentrations of aflibercept in right eyes (49.5 μg/mL) and left eyes (50.9 μg/mL) were both observed at 1 day after injection. The elimination half-life of aflibercept in the aqueous humor of the right eye (4.70 days) was 1 day longer than that of the left eye (3.65 days). The average percentage of residual aflibercept in the vitreous humor of the right eye (3.35%) was also significantly higher than that of the left eye (0.63%). Conclusions: Brinzolamide 1%/timolol maleate 0.5% fixed-combination eye drops can significantly extend the ocular residence time of intravitreally injected aflibercept.

Vitreous Substitutes from Bench to the Operating Room in a Translational Approach: Review and Future Endeavors in Vitreoretinal Surgery

Vitreous substitutes are indispensable tools in vitreoretinal surgery. The two crucial functions of these substitutes are their ability to displace intravitreal fluid from the retinal surface and to allow the retina to adhere to the retinal pigment epithelium. Today, vitreoretinal surgeons can choose among a plethora of vitreous tamponades, and the tamponade of choice might be difficult to determine in the ever-expanding range of possibilities for a favorable outcome. The currently available vitreous substitutes have disadvantages that need to be addressed to improve the surgical outcome achievable today. Herein, the fundamental physical and chemical proprieties of all vitreous substitutes are reported, and their use and clinical applications are described alongside some surgical techniques of intra-operative manipulation. The major upcoming developments in vitreous substitutes are extensively discussed, keeping a translational perspective throughout. Conclusions on future perspectives are derived through an in-depth analysis of what is lacking today in terms of desired outcomes and biomaterials technology.

Vitreous Humor: Composition, Characteristics and Implication on Intravitreal Drug Delivery

Purpose: Intravitreal administration of drug molecules is one of the most common routes for treating posterior segment eye diseases. However, the properties of vitreous humour changes with the time. A number of ocular complications such as liquefaction of the vitreous humour, solidification of the vitreous humour in the central vitreous cavity and detachment of the limiting membrane due to the shrinking of vitreous humour are some of the factors that can drastically affect the efficacy of therapeutics delivered via intravitreal route. Although significant research has been conducted for studying the properties of vitreous humour and its changes during the ageing process, there have been limited work to understand the effect of these changes on therapeutic efficacy of intravitreal drug delivery systems. Therefore, in this review we discussed both the coomposition and characteristics of the vitreous humour, and their subsequent influence on intravitreal drug delivery.Methods: Articles were searched on Scopus, PubMed and Web of Science up to March 2022.Results: In this review, we discussed the biological composition and biomechanical properties of vitreous humour, methods to study the properties of vitreous humour and the changes in these properties and their relevance in ocular drug delivery field, with the aim to provide a useful insight into these aspects which can aid the process of development of novel intravitreal drug delivery systems.Conclusions: The composition and characteristics of the vitreous humour, and how these change during natural aging processes, directly influence intravitreal drug delivery. This review therefore highlights the importance of understanding the properties of the vitreous and identifies the need to achieve greater understanding of how changing properties of the vitreous affect the therapeutic efficacy of drugs administered for the treatment of posterior eye diseases.

Ocular barriers as a double-edged sword: preventing and facilitating drug delivery to the retina

In recent decades, the growing of the aging population in the world brings increasingly heavy burden of vision-threatening retinal diseases. One of the biggest challenges in the treatment of retinal diseases is the effective drug delivery to the diseased area. Due to the existence of multiple anatomical and physiological barriers of the eye, commonly used oral drugs or topical eye drops cannot effectively reach the retinal lesions. Innovations in new drug formulations and delivery routes have been continuously applied to improve current drug delivery to the back of the eye. Unique ocular anatomical structures or physiological activities on these ocular barriers, in turn, can facilitate drug delivery to the retina if compatible formulations or delivery routes are properly designed or selected. This paper focuses on key barrier structures of the eye and summarizes advances of corresponding drug delivery means to the retina, including various local drug delivery routes by invasive approaches, as well as systemic eye drug delivery by non-invasive approaches.

The Roles of Vitreous Biomechanics in Ocular Disease, Biomolecule Transport, and Pharmacokinetics

PURPOSE

The biomechanical properties of the vitreous humor and replication of these properties to develop substitutes for the vitreous humor have rapidly become topics of interest over the last two decades. In particular, the behavior of the vitreous humor as a viscoelastic tissue has been investigated to identify its role in a variety of processes related to biotransport, aging, and age-related pathologies of the vitreoretinal interface.

METHODS

A thorough search and review of peer-reviewed publications discussing the biomechanical properties of the vitreous humor in both human and animal specimens was conducted. Findings on the effects of biomechanics on vitreoretinal pathologies and vitreous biotransport were analyzed and discussed.

RESULTS

The pig and rabbit vitreous have been found to be most mechanically similar to the human vitreous. Age-related liquefaction of the vitreous creates two mechanically unique phases, with an overall effect of softening the vitreous. However, the techniques used to acquire this mechanical data are limited by the in vitro testing methods used, and the vitreous humor has been hypothesized to behave differently in vivo due in part to its swelling properties. The impact of liquefaction and subsequent detachment of the vitreous humor from the posterior retinal surface is implicated in a variety of tractional pathologies of the retina and macula. Liquefaction also causes significant changes in the biotransport properties of the eye, allowing for significantly faster movement of molecules compared to the healthy vitreous. Recent developments in computational and ex vivo models of the vitreous humor have helped with understanding its behavior and developing materials capable of replacing it.

CONCLUSIONS

A better understanding of the biomechanical properties of the vitreous humor and how these relate to its structure will potentially aid in improving clinical metrics for vitreous liquefaction, design of biomimetic vitreous substitutes, and predicting pharmacokinetics for intravitreal drug delivery.

Extracellular Vesicles as Biomarkers and Therapeutics for Inflammatory Eye Diseases

Extracellular vesicles (EVs) are a group of cell-derived membrane vesicles of varying sizes that can be secreted by most cells. Depending on the type of cell they are derived from, EVs may contain a variety of cargo including proteins, lipids, miRNA, and DNA. Functionally, EVs play important roles in physiological and pathological processes through intercellular communication. While there has already been significant literature on the involvement of EVs in neurological and cardiovascular disease as well as cancer, recent evidence suggests that EVs may also play a role in mediating inflammatory eye diseases. This paper summarizes current advancements in ocular EV research as well as new ways by which EVs may be utilized as novel biomarkers of or therapeutics for inflammatory eye diseases.

Vitreous humor proteome: unraveling the molecular mechanisms underlying proliferative and neovascular vitreoretinal diseases

Proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and neovascular age-related macular degeneration (nAMD) are among the leading causes of blindness. Due to the multifactorial nature of these vitreoretinal diseases, omics approaches are essential for a deeper understanding of the pathophysiologic processes underlying the evolution to a proliferative or neovascular etiology, in which patients suffer from an abrupt loss of vision. For many years, it was thought that the function of the vitreous was merely structural, supporting and protecting the surrounding ocular tissues. Proteomics studies proved that vitreous is more complex and biologically active than initially thought, and its changes reflect the physiological and pathological state of the eye. The vitreous is the scenario of a complex interplay between inflammation, fibrosis, oxidative stress, neurodegeneration, and extracellular matrix remodeling. Vitreous proteome not only reflects the pathological events that occur in the retina, but the changes in the vitreous itself play a central role in the onset and progression of vitreoretinal diseases. Therefore, this review offers an overview of the studies on the vitreous proteome that could help to elucidate some of the pathological mechanisms underlying proliferative and/or neovascular vitreoretinal diseases and to find new potential pharmaceutical targets.

Formulation and Evaluation of Polymer-Based Nanoparticles for Intravitreal Gene-Delivery Applications

The advent of the first-ever retinal gene therapy product, involving subretinal administration of a virus-based gene delivery platform, has garnered hope that this state-of-the-art therapeutic modality may benefit a broad spectrum of patients with diverse retinal disorders. On the other hand, clinical studies have revealed limitations of the applied delivery strategy that may restrict its universal use. To this end, intravitreal administration of synthetic gene-delivery platforms, such as polymer-based nanoparticles (PNPs), has emerged as an attractive alternative to the current mainstay. To achieve success, however, it is imperative that synthetic platforms overcome key biological barriers in human eyes encountered following intravitreal administration, including the vitreous gel and inner limiting membrane (ILM). Here, we introduce a series of experiments, from the fabrication of PNPs to a comprehensive evaluation in relevant experimental models, to determine whether PNPs overcome these barriers and efficiently deliver therapeutic gene payloads to retinal cells. We conclude the article by discussing a few important considerations for successful implementation of the strategy. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Preparation and characterization of PNPs Basic Protocol 2: Evaluation of in vitro transfection efficacy Basic Protocol 3: Evaluation of PNP diffusion in vitreous gel Basic Protocol 4: Ex vivo assessment of PNP penetration within vitreoretinal explant culture Basic Protocol 5: Assessment of in vivo transgene expression mediated by intravitreally administered PNPs.

A Novel Transcriptome Approach to the Investigation of the Molecular Pathology of Vitreous and Retinal Detachment

Retinal detachment (RD) is one of the most common, sight-threatening ocular conditions requiring emergency intervention. Posterior vitreous detachment (PVD) occurs in the majority of an aging population whereby the vitreous body separates from the retina. It is well established that PVD is the common precursor to the most common forms of RD; however, it remains unknown why in most individuals PVD will cause no/few complications (physiological PVD) but in a small percentage will cause retinal tears and detachment (pathological PVD). Despite over 100 years of scientific research, the anatomical definitions of PVD and its pathogenesis remain controversial. Recent research has identified a novel cell population (laminocyte), present at significantly higher numbers in pathological PVD when compared to physiological PVD. We review and summarise the seven distinct clinical sub-groups of retinal breaks and focus on the role of the laminocyte in those secondary to PVD and the transcriptomic profile of this unique cell. Provisional whole transcriptome analysis using bulk RNA-Seq shows marked differentially expressed genes when comparing physiological PVD with PVD associated with RD. The limitations of bulk RNA-Seq are considered and the potential to address these using spatial transcriptomics are discussed. Understanding the pathogenesis of PVD-related retinal tears will provide a baseline for the development of novel therapeutic targets and prophylactic treatments.

Protocol to quantify enzymatic effects on vitreous liquefaction in porcine eyes using a transwell-plate system

This protocol describes an ex vivo model to quantify enzymatic effects on vitreous liquefaction using porcine eyes in a transwell-plate system via induced syneresis. It provides a standardized dissection process and performs critical steps for gel-liquid separation with high precision, minimal tissue loss, and scalability. The protocol can be applied to other studies investigating vitreous liquefaction or gelatinous tissue analysis and can also serve to study vitreous liquefaction in vivo as it may occur during aging or disease progression.

Structure and mechanics of the vitreoretinal interface

Vitreoretinal mechanics plays an important role in retinal trauma and many sight-threatening diseases. In age-related pathologies, such as posterior vitreous detachment and vitreomacular traction, lingering vitreoretinal adhesions can lead to macular holes, epiretinal membranes, retinal tears and detachment. In age-related macular degeneration, vitreoretinal traction has been implicated in the acceleration of the disease due to the stimulation of vascular growth factors. Despite this strong mechanobiological influence on trauma and disease in the eye, fundamental understanding of the mechanics at the vitreoretinal interface is limited. Clarification of adhesion mechanisms and the role of vitreoretinal mechanics in healthy eyes and disease is necessary to develop innovative treatments for these pathologies. In this review, we evaluate the existing literature on the structure and function of the vitreoretinal interface to gain insight into age- and region-dependent mechanisms of vitreoretinal adhesion. We explore the role of vitreoretinal adhesion in ocular pathologies to identify knowledge gaps and future research areas. Finally, we recommend future mechanics-based studies to address the critical needs in the field, increase fundamental understanding of vitreoretinal mechanisms and disease, and inform disease treatments.

Efficacy Evaluation of the VFQ-25 Scale in Patients with Different Degrees of Vitreous Opacity After Nd : YAG Laser Ablation

Objective

To evaluate the effect of the VFQ-25 scale on the efficacy of Nd : YAG laser ablation in patients with different severity of vitreous opacities.

Methods

From January 2020 to March 2021, data of patients who presented to our department and were diagnosed with vitreous opacity were collected, and the severity of vitreous opacity was divided into four grades: I, II, III, and IV. Preoperative visual acuity, intraocular pressure, dilated fundus, B ultrasound, and other examinations were performed, and the patients were scored using the VFQ-25 scale. All patients underwent Nd : YAG laser ablation and were followed for 6 months. The VFQ-25 scale was again used postoperatively to score the patient's efficacy. The general information and clinical characteristics of the patients we collected. The Spearman's test was used to evaluate the correlation between VFQ-25 score and Nd : YAG laser efficacy in patients.

Results

A total of 80 patients (95 eyes) were included in this study. Vitreous opacities were grade I in 56 eyes (58.9%), grade II in 22 eyes (23.2%), grade III in 10 eyes (10.5%), and grade IV in 7 eyes (7.4%). Compared with preoperative scores, patients with vitreous opacity had significantly higher postoperative scores in terms of overall health (36.54 ± 17.06 vs 33.52 ± 16.74), overall visual acuity (60.39 ± 14.24 vs 57.56 ± 13.13), color vision (88.94 ± 12.56 vs 86.38 ± 12.37), and peripheral visual acuity (74.06 ± 18.38 vs 72.20 ± 18.79) items (all P < 0.001). The overall response rates of vitreous opacities I, II, III, and IV were 100%, 90.9%, 80.0%, and 71.4%, respectively. There was a significant correlation between the postoperative VFQ-25 total score, and the therapeutic effect of laser ablation for grade I vitreous opacities, with a correlation coefficient r of 0.417 (P=0.001). The correlation coefficient r between the total score of postoperative VFQ-25 and the treatment effect of grade II vitreous opacity was 0.622 (P=0.002). However, the correlation between the postoperative efficacy of grade III and IV patients and the VFQ-25 score was not significant.

Conclusion

In patients with different degrees of vitreous opacity undergoing Nd : YAG laser vitreous ablation, the overall health, overall visual acuity, color vision, and peripheral visual acuity were improved after surgery, and the VFQ-25 score was significantly correlated with the postoperative efficacy, which is worthy of clinical use.

Proteomics and phosphoproteomics analysis of vitreous in idiopathic epiretinal membrane patients

PURPOSE

The purpose of the present study was to characterize the idiopathic epiretinal membrane (iERM) through proteomics and phosphoproteomics analysis to facilitate the diagnosis and treatment of iERM.

EXPERIMENTAL DESIGN

The vitreous of 25 patients with an iERM and 15 patients with an idiopathic macular hole were analyzed by proteomic and phosphoproteomic analysis based on tandem mass tag. PRM was used to verify the differential proteins.

RESULTS

Proteomic analysis identified a total of 878 proteins, including 50 differential proteins. Tenascin-C, galectin-3-binding protein, glucose-6-phosphate isomerase, neuroserpin, collagen alpha-1(XI) chain, and collagen alpha-1(II) chain were verified to be upregulated in iERM by PRM. Phosphoproteomic analysis identified a total of 401 phosphorylation sites on 213 proteins, including 27 differential phosphorylation sites on 24 proteins. Mitogen-activated protein kinase-activated protein kinase (MAPKAPK)3 and MAPKAPK5 were predicted as the major kinases in the vitreous of iERM. Twenty-six of the differential proteins and phosphorylated proteins may be closely related to fibrosis in iERM.

CONCLUSION AND CLINICAL RELEVANCE

Our results indicated the potential biomarkers or therapeutic targets for iERM, provided key kinases that may be involved in iERM. Fibrosis plays an essential role in iERM, and further exploration of related differential proteins has important clinical significance.

Non-Invasive Iontophoretic Delivery of Cytochrome c to the Posterior Segment and Determination of Its Ocular Biodistribution

The intact porcine eye globe model was used to demonstrate that transscleral iontophoresis could deliver a small protein, cytochrome c (Cyt c), to the posterior segment and to investigate post-iontophoretic biodistribution in the different ocular compartments. The effects of Cyt c concentration (1, 5, and 10 mg/mL), current density (3.5 and 5.5 mA/cm²), and duration of the current application (10 min and 1, 2, and 4 h) were evaluated. The data confirmed that transscleral iontophoresis enhanced the intraocular delivery of Cyt c under all conditions as compared to passive controls (same setup but without the current application). Increasing the Cyt c concentration resulted in a proportional enhancement in the Cyt c delivery. Increasing the current density from 3.5 to 5.5 mA/cm² increased iontophoretic delivery at a Cyt c concentration of 10 mg/mL but did not appear to do so at 5 mg/mL; this was attributed in part to the effect of melanin binding. Short duration iontophoresis (10 min, 3.5 mA/cm²) of a 10 mg/mL Cyt c solution created a depot in the sclera. When this was followed by a 4 h incubation period, post-iontophoretic Cyt c diffusion from the sclera resulted in a different biodistribution, and Cyt c could be quantified in the posterior segment.

Cell atlas of the human ocular anterior segment: Tissue-specific and shared cell types

The anterior segment of the eye consists of the cornea, iris, ciliary body, crystalline lens, and aqueous humor outflow pathways. Together, these tissues are essential for the proper functioning of the eye. Disorders of vision have been ascribed to defects in all of them; some disorders, including glaucoma and cataract, are among the most prevalent causes of blindness in the world. To characterize the cell types that compose these tissues, we generated an anterior segment cell atlas of the human eye using high-throughput single-nucleus RNA sequencing (snRNAseq). We profiled 195,248 nuclei from nondiseased anterior segment tissues of six human donors, identifying >60 cell types. Many of these cell types were discrete, whereas others, especially in the lens and cornea, formed continua corresponding to known developmental transitions that persist in adulthood. Having profiled each tissue separately, we performed an integrated analysis of the entire anterior segment, revealing that some cell types are unique to a single structure, whereas others are shared across tissues. The integrated cell atlas was then used to investigate cell type-specific expression patterns of more than 900 human ocular disease genes identified through either Mendelian inheritance patterns or genome-wide association studies.

Hyaluronic Acid-PEG-Based Diels-Alder In Situ Forming Hydrogels for Sustained Intraocular Delivery of Bevacizumab

Retinal diseases are the leading cause of visual impairment worldwide. The effectiveness of antibodies for the treatment of retinal diseases has been demonstrated. Despite the clinical success, achieving sufficiently high concentrations of these protein therapeutics at the target tissue for an extended period is challenging. Patients suffering from macular degeneration often receive injections once per month. Therefore, there is a growing need for suitable systems that can help reduce the number of injections and adverse effects while improving patient complacency. This study systematically characterized degradable "in situ" forming hydrogels that can be easily injected into the vitreous cavity using a small needle (29G). After intravitreal injection, the formulation is designed to undergo a sol-gel phase transition at the administration site to obtain an intraocular depot system for long-term sustained release of bioactives. A Diels-Alder reaction was exploited to crosslink hyaluronic acid-bearing furan groups (HAFU) with 4 arm-PEG10K-maleimide (4APM), yielding stable hydrogels. Here, a systematic investigation of the effects of polymer composition and the ratio between functional groups on the physicochemical properties of hydrogels was performed to select the most suitable formulation for protein delivery. Rheological analysis showed rapid hydrogel formation, with the fastest gel formation within 5 min after mixing the hydrogel precursors. In this study, the mechanical properties of an ex vivo intravitreally formed hydrogel were investigated and compared to the in vitro fabricated samples. Swelling and degradation studies showed that the hydrogels are biodegradable by the retro-Diels-Alder reaction under physiological conditions. The 4APM-HAFU (ratio 1:5) hydrogel formulation showed sustained release of bevacizumab > 400 days by a combination of diffusion, swelling, and degradation. A bioassay showed that the released bevacizumab remained bioactive. The hydrogel platform described in this study offers high potential for the sustained release of therapeutic antibodies to treat ocular diseases.

Detection of Anterior Hyaloid Membrane Detachment Using Deep-Range Anterior Segment Optical Coherence Tomography

The visibility of anterior hyaloid membrane (AHM) and Berger’s space in phakic eyes was investigated. In 624 eyes of 624 patients, the retrolental space was scanned with the deep-range anterior segment optical coherence tomography (AS-OCT, CASIA2, Tomey). Subgroup analysis was conducted in 223 eyes undergoing cataract surgery. The logistic regression analysis using the backward-elimination method was performed to evaluate the influence of various factors on the visibility of AHM (dependent variable). Explanatory variables included age, gender, axial length, corneal power, corneal cylinder, and the Co III gradings. Intrarater repeatability for AHM visibility was excellent with the prevalence-adjusted bias-adjusted kappa (κ coefficient) of 0.90. AHM was observed in 43 eyes (6.9%). The patients with visible AHM (68.1 ± 8.8 years) were significantly older than those without visible AHM (52.6 ± 25.6 years) (p < 0.001). The logistic regression analysis in the cataract surgery subgroup revealed that axial length (p = 0.030) and corneal power (p = 0.043) were significantly associated with AHM visibility. The mean absolute refractive error from target was significantly larger in eyes with visible AHM (0.670 ± 0.384 D) than with invisible AHM (0.494 ± 0.412 D) (p = 0.037). The postoperative refractive prediction was less accurate in eyes with visible AHM, but no significant tendency existed in terms of myopic or hyperopic shifts.

Potential Prognostic Indicators for Patients With Retinal Vein Occlusion

The second most prevalent cause of retinal vascular disease is retinal vein occlusion (RVO). RVO raises intravascular pressure in the capillary and veins, triggering vessel barrier collapse and subsequent leaking of blood or plasma components into the tissue (edema). Macular edema (ME) is a major complication of RVO that results in significant visual impairment. Laser therapy, intravitreal steroid injections, and vascular endothelial growth factor (VEGF) inhibitors are the major therapeutic techniques. Different therapies reduce ME of RVO and improve visual activity. However, some people have no impact on the resolution of ME, while others have a poor visual prognosis despite full ME cure. There are many investigators who studied the relationship between indicators of various instruments with visual activity. However, a summary of those findings is currently lacking. Therefore, we will focus on the predictive factors of different studies associated with positive visual activity outcomes, which would be very useful and important to help address both treatment expectations and methods for patients with RVO.

Relationship of choroidal thickness and axial length with posterior vitreous detachment in patients with high myopia

Although accumulating evidence suggests a higher prevalence of posterior vitreous detachment (PVD) in highly myopic eyes, the relation between ocular biometric features and PVD stages in such eyes remains unclear. Therefore, we enrolled 170 patients with high myopia (axial length ≥ 26.0 mm) to investigate the status of PVD regarding subfoveal choroidal thickness and axial length. Utilising swept-source optical coherence tomography, we classified the PVD status into five stages. The distribution of PVD grades increased as the choroidal thickness decreased and axial length increased (P < 0.01). On adjusting for age and sex, decreased choroidal thickness and increased axial length were associated with more advanced PVD stages: odds ratios with the highest vs. lowest groups were 0.31 (95% confidence interval [CI] 0.09-1.01; P_trend = 0.009) for choroidal thickness and 5.16 (95% CI 1.34-19.80; P_trend = 0.002) for axial length. The inverse association between choroidal thickness and PVD status seemed stronger in women than in men (P_interaction = 0.05). In conclusion, we firstly observed a significant trend of decreased choroidal thickness, along with increased axial length, with increased grade of PVD, particularly among women with highly myopic eyes, suggesting that advanced morphological myopic changes contribute to PVD in middle-aged adults.

Human Vitreous Collagen Fragments Dimension As a Function of Vitrectomy Cut Rate

Purpose

To study the dimensions and distribution of human vitreous collagen type II fragments collected after vitrectomy performed at varying cut rates and to evaluate if increasing the cut rate produces smaller collagen fragments, thus reducing retinal traction and/or viscosity.

Methods

Fluid was collected during core vitrectomies performed for macular surgery at cut rates from 1000 to 16,000 cuts per minute (CPM) and immediately refrigerated. Protein fractions were separated by molecular weight (MW; >100 kDa, 50–100 kDa, 50–30 kDa, 30–10 kDa, and <10 kDa) through centrifugal filters. The Human Collagen II ELISA Kit colorimetric assay was then used to measure the COL2A1 in unfiltered and filtered samples.

Results

Vitreous samples collected after vitrectomy performed at 16,000 CPM contained a higher concentration of protein with MW over 100 kDa than at any other cutting frequency (P < 0.01). No significant differences were found in fractions collected with a MW between 50 and 100 kDa. Collagen type II fragments over 100 kDa were significantly more represented than smaller fragments at each cut rate. The proportion of smaller (50–100 kDa) collagen fragments compared with those over 100 kDa was higher at 2000 CPM than at higher cut rates.

Conclusions

Vitreous samples collected at different cut rates do not contain a significantly different proportion of collagen type II fragments of the tested MW. The extreme variability of vitreous flow through the cutter port may explain the uncertain predictability of collagen fragment MWs.

Translational Relevance

Increasing the cut rate does not produce vitreous fragments of proportionally smaller dimension. It is necessary to achieve an invariant instantaneous flow through the cutter port in order to decrease retinal traction during vitrectomy.

Elucidating the clinical spectrum and molecular basis of HYAL2 deficiency

PURPOSE

We previously defined biallelic HYAL2 variants causing a novel disorder in 2 families, involving orofacial clefting, facial dysmorphism, congenital heart disease, and ocular abnormalities, with Hyal2 knockout mice displaying similar phenotypes. In this study, we better define the phenotype and pathologic disease mechanism.

METHODS

Clinical and genomic investigations were undertaken alongside molecular studies, including immunoblotting and immunofluorescence analyses of variant/wild-type human HYAL2 expressed in mouse fibroblasts, and in silico modeling of putative pathogenic variants.

RESULTS

Ten newly identified individuals with this condition were investigated, and they were associated with 9 novel pathogenic variants. Clinical studies defined genotype-phenotype correlations and confirmed a recognizable craniofacial phenotype in addition to myopia, cleft lip/palate, and congenital cardiac anomalies as the most consistent manifestations of the condition. In silico modeling of missense variants identified likely deleterious effects on protein folding. Consistent with this, functional studies indicated that these variants cause protein instability and a concomitant cell surface absence of HYAL2 protein.

CONCLUSION

These studies confirm an association between HYAL2 alterations and syndromic cleft lip/palate, provide experimental evidence for the pathogenicity of missense alleles, enable further insights into the pathomolecular basis of the disease, and delineate the core and variable clinical outcomes of the condition.

Biodistribution of Cy5-labeled Thiolated and Methylated Chitosan-Carboxymethyl Dextran Nanoparticles in an Animal Model of Retinoblastoma

Purpose

The use of more potent medicine for local chemotherapy of retinoblastoma in order to minimize local and systemic adverse effects is essential. The main goal of this investigation was to assess the biodistribution of thiolated and methylated chitosan-carboxymethyl dextran nanoparticles (CMD-TCs-NPs and CMD-TMC-NPs) following intravitreal (IVT) injection into rat eyes with retinoblastoma.

Methods

An ionic gelation method was used to fabricate Cy5-labelled CMD-TCs-NPs and CMD-TMC-NPs. The NPs were characterized. Cellular internalization of Cy5-labelled NPs was investigated using confocal microscopy and the absorption of labeled NPs was quantified by flow cytometry in human retinoblastoma (Y79) cells. In addition, the Cy5-labeled distribution of nanoparticles in the posterior segment of the eye was histologically imaged by confocal microscopy after IVT injection of NPs into the eyes of rats with retinoblastoma.

Results

CMD-TCs-NPs and CMD-TMC-NPs showed a mean diameter of 34 ± 3.78 nm and 42 ± 4.23 nm and zeta potential of +11 ± 2.27 mV and +29 ± 4.31mV, respectively. The in vivo study of intraocular biodistribution of Cy5-labeled CMD-TCs-NPs and CMD-TMC-NPs revealed that there is more affinity of CMD-TCs-NPs to the retina and retinoblastoma tumor after IVT administration while methylated chitosan nanoparticles are immobilized in the vitreous and are not able to reach the retina even after 24 hr.

Conclusion

The ionic gelation technique was efficient in synthesizing a biocompatible polymeric nanosystem for drug delivery into the posterior segment of the eye. The current study demonstrated increased ocular bioavailability of CMD-TCs-NPs relative to CMD-TMC-NPs in retinoblastoma induced rat eyes.