The sclera and myopia

Scleral ultrastructure in young rhesus monkeys: A stereological approach

The sclera provides mechanical support to the globe and plays a key role in maintenance of ocular structural integrity. Evidence shows that scleral remodeling contributes to biomechanical weakening, increasing the risk of pathologies, such as glaucoma and posterior staphyloma in high myopia. A precise characterization of normal regional ultrastructure is needed for a better understanding of scleral remodeling. The purpose of this study was to develop and implement a stereological analysis method to characterize scleral ultrastructure in healthy young rhesus monkey eyes. Monkeys (N = 4 eyes) first underwent normal emmetropization in a primate nursery. At 150 days of age, scleral tissue was collected in 1 mm2 sections from three regions, equatorial nasal, posterior, and equatorial temporal, and processed for transmission electron microscopy (TEM). Images were captured at three depths: outer, middle, and inner, for all regions. Scleral thickness, fibroblast volume fraction, volume fraction of fibrillin microfibrils, and collagen fibril diameters were quantified using stereology and manual segmentation. The sclera was thickest in the posterior region with a mean thickness of 217.1 ± 10.1 μm. A total of 103 micrographs were analyzed to compute the volume fraction of fibroblasts and fibrillin microfibrils. Median fibroblast volume fraction was 7.4 %, and fibrillin microfibril volume fraction was 1.8 %. A total of 3564 collagen fibrils, encompassing 99 fibrils per region and depth per eye, were analyzed. Median collagen fibril diameter was 79.8 nm and ranged from 23 nm to 205 nm. This stereological approach provides a foundation for future studies investigating myopic scleral remodeling, where axial elongation and scleral thinning are known to show regional differences.

Nano-based drug delivery systems for the treatment of non-infectious uveitis

Background

Uveitis is one of the most prevalent causes of global visual impairment. The current approaches to treating non-infectious uveitis (NIU) involve the utilization of corticosteroids, immunosuppressant and biologics agents. Nevertheless, the intricate ocular anatomy barriers and adverse side effects of the drugs pose significant obstacles to effective treatment outcomes.

Main text

To improve drug bioavailability and therapeutic outcomes for NIU while minimize side effects, researchers are committed to developing novel nano-based drug delivery systems (DDS), which have the capacity to achieve targeted delivery, increase bioavailability, achieve sustained release, reduce side effects and improve therapeutic effects. Thus, DDS based on nanotechnology, including liposome, dendrimer, hydrogels, nanoparticles, nanomicelles, nanosuspensions and nanoemulsions have emerged as promising alternatives to conventional ocular delivery methods for the management of NIU.

Conclusions

In this review, we summarize the current therapeutic challenges faced by NIU and describe various nano-based intraocular DDS involved in the treatment of NIU. It is concluded that nano-based DDS is an appealing approach to addressing the unmet needs for the treatment of NIU.

Covariation of scleral remodeling and PI3K/Akt signaling pathway in experimental myopia

The present study aimed to investigate the role of the PI3K/Akt signaling pathway in scleral remodeling in the development of negative lens-induced myopia (LIM). The change of scleral morphology in experimental myopic guinea pigs was observed by transmission electron microscopy, Masson staining, and TUNEL assay, respectively. Meanwhile, the levels of the PI3K/AKT signaling pathway- and scleral remodeling-related molecules in scleral tissues were determined by real-time quantitative PCR (qPCR), enzyme-linked immunosorbent assay (ELISA), immunofluorescence, immunohistochemical staining, and western blot, respectively. We found that 2-week myopic induction can elevate PIK3R3 and AKT2 levels and activate the PI3K/Akt signaling pathway, enhance the expression of E-cadherin and matrix metallopeptidase 2 (MMP2), and decrease the level of transforming growth factor-beta 1 (TGF-β1), tissue inhibitor of matrix metalloproteinase-2 (TIMP2), and collagen (COLI) in the scleral tissue of myopic guinea pigs, thereby leading to scleral remolding. However, 4-week myopic induction could inhibit the PI3K/AKT signaling pathway and induce apoptosis, accompanied by increased MMP2, E-cadherin, and decreased TGF-β1, TIMP2, and COLI. Results reveal that the disturbed PI3K/AKT signaling plays a role in scleral remodeling in the experimental myopia through orchestrating apoptosis.

The Peripheral Defocus Designed Spectacle Lenses Might Increase Astigmatism in Myopic Children

Purpose

This study aims to explore the impact of wearing peripheral defocus spectacle lenses (PDSL) on cylindrical refractive error (CYL) in myopic children.

Methods

This study included 1057 myopic children and divided the participants into three groups: the HAL group (spectacle lens with highly aspherical lenslets), the MPV group (spectacle lens based on manipulating peripheral vision), and a control group (without myopia control interventions). The study analyzed the effect of wearing PDSL on changes in spherical equivalent refraction, CYL, and corneal astigmatism (CA). The mediating effect between changes in spherical refractive errors (SPH) and CYL was also investigated.

Results

Compared to the control group (0.05 ± 0.33 D), the annual CYL progression was faster in the HAL group (-0.15 ± 0.33 D, P < 0.001) and the MPV group (-0.09 ± 0.27 D, P = 0.019). More children in the HAL group had an annual CYL progression ≥0.50 D (HAL: 23.6%, Control: 16.2%, P = 0.012). The annual CYL and CA progression were consistent within the PDSL groups (HAL: P = 0.677, MPV: P = 0.683). The total effect of CYL progression in the HAL group was primarily due to direct induction from wearing HAL and indirect induction through the SPH control effect.

Conclusions

The application of PDSL could cause increase in astigmatism in myopic children, which could mainly be contributed to cornea astigmatism change.

Translational Relevance

PDSL may passively affect the anterior ocular biomechanics during myopia control, leading to an increase in astigmatism.

Whorl-Like Collagen Fiber Arrangement Around Emissary Canals in the Posterior Sclera

Purpose

To investigate the collagen fiber arrangement around emissary canals in the posterior sclera.

Methods

One hundred sixty-five eyes of 93 patients who underwent polarization-sensitive optical coherence tomography (PS-OCT) examinations in 2019 in the Institute of Science Tokyo were studied. Multimodal imaging, including streamline images derived from PS-OCT data, B-scan images, and indocyanine green angiography (ICGA) images, was used to investigate the collagen fiber arrangement around emissary canals and scleral pits in vivo. Additionally, the collagen fiber arrangement around the emissary canals in porcine sclera was examined using scanning electron microscopy and light microscopy.

Results

Streamline images showed whorl-like collagen fiber arrangements on all eyes, and 25 eyes were selected for the analysis. All whorls corresponded to emissary canals on B-scan images. The whorls were confirmed to correspond to the posterior ciliary artery entries in three eyes and posterior vortex vein exits in three eyes with available ICGA images. Streamline cutaway images showed that the whorls surrounded the emissary canals throughout the entire course. In 16 eyes with 20 scleral pits, whorls were seen surrounding all the pits. Microscopic study using porcine sclera confirmed the whorl-like structures around the emissary canals ex vivo and demonstrated tangentially arranged collagen fiber bundles forming the circle.

Conclusions

The collagen fibers are arranged as whorl-like structures around the vessel emissary canals in the posterior sclera, which is a knowledge gap for basic scleral histology. Additionally, this study demonstrated a strong correlation between PS-OCT findings and microscopic histology, underscoring PS-OCT's utility in detecting scleral collagen fiber arrangements.

Exploring Molecular Pathways in Refractive Errors Associated with Inherited Retinal Dystrophies

The term inherited retinal dystrophies (IRDs) refers to a diverse range of conditions characterized by retinal dysfunction, and mostly deterioration, leading to a gradual decay of the visual function and eventually to total vision loss. IRDs have a global impact on about 1 in every 3000 to 4000 individuals. However, the prevalence statistics might differ significantly depending on the exact type of dystrophy and the demographic being examined. The cellular pathophysiology and genetic foundation of IRDs have been extensively studied, however, knowledge regarding associated refractive errors remain limited. This review aims to clarify the cellular and molecular processes that underlie refractive errors in IRDs. We did a thorough search of the current literature (Pubmed, accession Feb 2024), selecting works describing phenotypic differences among genes-related to IRDs, particularly in relation to refractive errors. First, we summarize the wide range of IRDs and their genetic causes, describing the genes and biological pathways connected to the etiology of the disease. We then explore the complex relationship between refractive errors and retinal dysfunction, including how the impairment of the vision-related mechanisms in the retina can affect ocular biometry and optical characteristics. New data about the involvement of aberrant signaling pathways, photoreceptor degeneration, and dysfunctional retinal pigment epithelium (RPE) in the development of refractive errors in IRDs have been examined. We also discuss the therapeutic implications of refractive defects in individuals with IRD, including possible approaches to treating visual impairments. In addition, we address the value of using cutting-edge imaging methods and animal models to examine refractive errors linked to IRDs and suggest future lines of inquiry for identifying new targets for treatment. In summary, this study presents an integrated understanding of the cellular and molecular mechanisms underlying refractive errors in IRDs. It illuminates the intricacies of ocular phenotypes in these conditions and offers a tool for understanding mechanisms underlying isolated refractive errors, besides the IRD-related forms.

UPLC-MS/MS-based serum metabolomics analysis for comprehensive pathological myopia profiling

Pathological myopia (PM) is associated with ocular morbidities that cause blindness. PM often occurs in eyes with high myopia (HM) while they are distinctly different. Identifying the differences in metabolites and metabolic pathways between patients with PM and HM may provide information about the pathogenesis of PM, which is currently unknown. This study aimed to reveal the comprehensive metabolic alterations associated with PM. Thirty patients with PM, 27 with simple HM and 27 with low myopia (LM) were enrolled in this study. Ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) was performed, and a Venn diagram was generated to explore the overlapping differential metabolites and enriched pathways between each set of two groups. The area under the receiver operating characteristic curve (AUC) was computed to assess the discrimination capacity of each metabolite marker. A total of 134, 125 and 81 differential metabolites were identified in each comparison. Thirty-two differential metabolites were overlapped between the PM vs HM comparison and the PM vs LM comparison. Of these 32 metabolites, 16 were common to all three comparisons; among these metabolites, high levels of 4-hydroxy-l-glutamic acid and low levels of succinic semialdehyde and 2,3-dinor-8-iso prostaglandin F2α appeared to be risk factors for PM. The remaining 16 metabolites were shared only between the PM versus HM and PM versus LM comparisons, most of which are lipid molecules. Pathway analysis revealed that alanine, aspartate and glutamate metabolism was the key metabolic pathway altered in PM patients. Overall, significant differences in the metabolites and metabolic pathways were observed in patients with PM. The metabolic differences identified in this study included differential factors between PM and HM patients, addressing current gaps in PM research. These findings provide a novel perspective of the molecular mechanism of PM.

In vivo assessment of regional scleral stiffness by shear wave elastography and its association with choroid and retinal nerve fiber layer characteristics in high myopia

PURPOSE

To evaluate the posterior scleral stiffness of different regions in high myopic eyes and to explore its associations with macular choroidal and peripapillary retinal nerve fiber layer (pRNFL) thickness and vasculature.

METHODS

Thirty subjects with high myopic eyes and 30 subjects with low myopic eyes were included in this study. The elastic modulus of the macular and peripapillary sclera at the temporal, nasal, superior and inferior regions were determined via shear wave elastography (SWE). Optical coherence tomography and angiography (OCT/OCTA) centered on the fovea and optic disc was obtained by using a commercially available swept-source OCT/OCTA device. Built-in automated software was used to quantify macular subfovea choroidal vessel volume (SFCVV), macular subfovea choroidal thickness (SFCT) and pRNFL thickness.

RESULTS

The SWE results demonstrated that high myopic eyes had significantly lower macular and peripapillary scleral elastic modulus than low myopic eyes (P < 0.001). The reduction in the elastic modulus was slightly greater in the temporal peripapillary region, followed by the superior peripapillary, inferior and nasal peripapillary regions (P > 0.05). The linear regression analysis demonstrated a significant association between the posterior scleral elastic modulus and SFCT and inferior pRNFL thickness (P < 0.001).

CONCLUSION

High myopic eyes had weakened posterior scleral stiffness. The regional change in the elastic modulus was associated with the SFCT and inferior quadrant pRNFL thickness. This novel in vivo quantitative assessment of scleral stiffness via SWE may help to characterize the underlying pathologic mechanism of scleral biomechanics on choroid and pRNFL changes in high myopia.

KEY MESSAGES

WHAT IS KNOWN : Previous studies reported significant choroid thickness and peripapillary nerve fiber layer thickness decrease in high myopia The scleral stiffness is weakened in myopic eyes WHAT IS NEW : Shear wave elastography (SWE) is a novel tool to detect posterior scleral biomechanics in myopic eyes in vivo Stiffness of the posterior sclera at macular and peripapillary regions is lower in high myopic than in low myopic eyes The posterior scleral stiffness is correlated with subfovea choroidal thickness and inferior quadrant peripapillary nerve fiber layer thickness.

Effect of Hydration on Viscoelastic Tensile Properties of Sclera

The present work characterized the effects of hydration on the viscoelastic tensile properties of the sclera. Scleral strips were dissected from the posterior region near the optic nerve head of porcine eyes in the superior-inferior direction. The samples were divided into four hydration groups and their mechanical response was characterized by conducting uniaxial tensile stress-relaxation experiments. An exponential relation and logarithmic expression were used to numerically represent the experimental measurements during the ramp and relaxation periods, respectively. A nonlinear increase in the tensile stress during the ramp period was observed for all strips. Furthermore, it was found that dehydrated specimens had stiffer tensile properties. In particular, it was observed that the maximum and equilibrium stresses increased significantly with decreasing hydration. Furthermore, it was found that the viscoelastic tensile response of porcine scleral strips at different hydration levels could be collapsed onto a single normalized curve. The findings of the present work showed that hydration had significant effects on the viscoelastic tensile properties of sclera.

The effect of transient increase in intraocular pressure on subfoveal choroidal thickness

SIGNIFICANCE

Myopia prevalence has increased over the last few decades. Studies have documented that the choroid is considered an important biomarker in myopia development. As myopia and choroidal thinning are associated with increased glaucoma risk, understanding the role of the choroid in myopia and glaucoma is imperative.

PURPOSE

This study investigates the effect of transiently elevated intraocular pressure on axial length, subfoveal choroidal thickness, and central retinal thickness in emmetropes, low myopes, and high myopes.

METHODS

This study involved 29 young adults (23 ± 1 years), including 10 emmetropes (-0.50 D < SE < +0.50 D), 10 low myopes (-6.00 D < SE ≤ -0.50 D), and 9 high myopes (SE ≤ -6.00 D). Participants were fitted with modified swimming goggles for 5 minutes to transiently change intraocular pressure. Noncontact tonometry, optical biometry, and optical coherence tomography were used to measure intraocular pressure, axial length, central retinal thickness, and subfoveal choroidal thickness, respectively. Measurements were taken at before, during goggle wear, immediately after, and 3 minutes after goggles removal. Repeated-measures analysis of variance with Bonferroni adjustment was used to assess the effect of transiently changed intraocular pressure and to elucidate any differences between refractive groups in response to the intraocular pressure change.

RESULTS

Intraocular pressure increased by 1.7 ± 2.1 mmHg (p=0.002) from baseline, accompanied by axial elongation of 14 ± 21 μm (p = 0.012) and subfoveal choroidal thinning of 13 ± 15 μm (p=0.01). However, central retinal thickness did not change significantly (p>0.05). Most of the changes in the axial length were due to changes in the choroidal thickness. Observed changes returned to baseline immediately following goggles removal. There was no significant difference between refractive error groups' changes associated with the transient increase in intraocular pressure (p>0.05).

CONCLUSIONS

Transiently increased intraocular pressure caused temporary axial elongation and subfoveal choroidal thinning, with no significant differences between refractive groups. Further studies are required to assess the impact of long-term increased intraocular pressure on ocular components.

Prognostic factors for surgical treatment of radiation-induced scleral necrosis after brachytherapy for uveal melanoma

PURPOSE

Radiation-induced scleral necrosis (RISN) is a less frequent complication of brachytherapy for uveal melanoma, and may require surgical treatment in selected cases. We aimed to identify the prognostic factors for RISN treatment.

METHODS

All patients with brachytherapy for uveal melanoma treated at our institution between 01/1999 and 12/2016 who developed RISN were followed until 02/2021. Various parameters were evaluated through univariable and multivariable Cox regression analysis. The surgical intervention due to RISN was the principal outcome event of this study.

RESULTS

Of 115 patients in the final cohort, 51 individuals (44%) underwent RISN treatment (conjunctival revision [n = 2], patching [n = 46] or enucleation [n = 3]) at median 1.80 months after RISN occurrence. Significant RISN characteristics were summarized into a novel RISN severity scale - Grade I: largest diameter ≤ 5 mm and no progression; Grade II: largest diameter > 5 mm or any progression during the follow-up; Grade III: presence of uveal prolapse; and Grade IV: leakage through open eyewall perforation. In the multivariable analysis, the RISN severity scale (aHR = 2.37 per grade increase, p = 0.01) and the time between brachytherapy and RISN occurrence (<15 months, aHR = 6.33, p < 0.0001) were independently associated with the study endpoint. The RISN severity scale showed high diagnostic accuracy for prediction of RISN treatment (AUC = 0.869).

CONCLUSIONS

In our series, about the half of RISN cases underwent surgical treatment. The presented novel severity scale for RISN might become a helpful tool for clinical management of individuals with RISN. We recommend external validation of the diagnostic accuracy of the presented scale.

A novel variant in the keratin 12 gene in a four-generation Chinese family with high myopia

BACKGROUND

High myopia is a major cause of visual impairment, and genetic factors play crucial roles in the pathogenesis. We performed this study to identify candidate genes for the development of high myopia in a four-generation Chinese family with myopia.

METHODS

All family members with myopia and 100 healthy participants were included in this study. Data were obtained on demographics, disease history, and ocular examination results. We performed whole exome sequencing of the genomic DNA and Sanger sequencing to verify the variants. Functional analyses of the variant were performed using software programmes.

RESULTS

Nine of thirteen family members were found to have high myopia, amongst which two members were also diagnosed keratoconus. A missense variant in the keratin 12 gene (KRT12, p.Val410Gly) was detected in all high myopia cases but not in other family members without high myopia or the controls. The variant was predicted to be benign by online software programmes. However, modelling of the three-dimensional structure of the protein clearly revealed conformational changes caused by the mutation.

CONCLUSIONS

A missense mutation in the KRT12 gene was identified in this Chinese family, which may be associated with the pathogenesis of high myopia.

Quercetin Alleviates Scleral Remodeling Through Inhibiting the PERK-EIF2α Axis in Experiment Myopia

Purpose

This study aims to investigate the effect of quercetin (QUE) on scleral remodeling by inhibiting the PERK-EIF2α signaling pathway and to evaluate its potential role in slowing myopia.

Methods

Lens-induced myopia (LIM) guinea pigs were obtained and treated with QUE. After 4 and 6 weeks of treatments, ocular biological measurements were conducted. Hematoxylin and eosin (H&E) staining was used to observe the changes in scleral morphology and thickness, and Masson staining was used to examine scleral collagen fiber arrangement. Quantitative PCR (qPCR) and Western bolt were utilized to detect the mRNA and protein expression of PERK, EIF2α, MMP-2, TIMP-2, and collagen I in the scleral tissues. Calcium ion flow in each group was measured using noninvasive micro-test technology, and reactive oxygen species levels were detected by flow cytometry.

Results

Compared with the LIM group, the ocular measurements showed that the refractive errors and axial length of the eyes were significantly reduced in the LIM + QUE group (P < 0.01). H&E and Masson staining showed that sclera in the LIM + QUE group was thickened, collagen was dense, and the fiber gap was reduced. In the LIM + QUE group, the expression levels of PERK, EIF2α, and MMP-2 were decreased, whereas the expression levels of TIMP-2 and collagen I were increased. Calcium release and reactive oxygen species (ROS) in the LIM + QUE group were decreased.

Conclusions

Quercetin ameliorates scleral remodeling in myopic guinea pigs by inhibiting the PERK-EIF2α signaling pathway, thereby alleviating the progression of myopia. These findings provide new experimental evidence for the potential application of quercetin in myopia prevention and treatment.

Animal modeling for myopia

Background

Myopia is one of the most common eye diseases globally, and has become an increasingly serious health concern among adolescents. Understanding the factors contributing to the onset of myopia and the strategies to slow its progression is critical to reducing its prevalence.

Main text

Animal models are key to understanding of the etiology of human diseases. Various experimental animal models have been developed to mimic human myopia, including chickens, rhesus monkeys, marmosets, mice, tree shrews, guinea pigs and zebrafish. Studies using these animal models have provided evidences and perspectives on the regulation of eye growth and refractive development. This review summarizes the characteristics of these models, the induction methods, common indicators of myopia in animal models, and recent findings on the pathogenic mechanism of myopia.

Conclusions

Investigations using experimental animal models have provided valuable information and insights into the pathogenic mechanisms of human myopia and its treatment strategies.

Quantitative structural organization of the sclera in chicks after deprivation myopia measured with second harmonic generation microscopy

Visual deprivation causes enhanced eye growth and the development of myopia, which is associated with a change in the arrangement of collagen fibers within the sclera. A second harmonic generation (SHG) microscope has been used to image the collagen fibers of unstained scleral punches from the posterior part of chicken eyes. We aimed to analyze the fibrous scleral tissue and quantify the changes in collagen organization in relation to the extent of induced deprivation myopia. The scleral architecture was assessed with the Radon transform (RT) through the parameter called structural dispersion (SD) that provides an objective tool to quantify the level of organization of the collagen network. We found that final refraction and axial length changes were linearly correlated. However, no significant differences in scleral thickness were found for different amounts of induced myopia. In contrast, a significant correlation between SD and refraction was demonstrated, ranging from a non-organized (in the control sclerae) to a quasi-aligned distribution (with a dominant direction of the fibers, in the sclera of myopic chicks). These findings demonstrate a remodeling process of the scleral collagen associated with myopia progression that can be measured accurately combining SHG imaging microscopy and RT algorithms.

Dynamic BMP gene expression regulation in chick RPE during recovery from short term optical defocus and form-deprivation

PURPOSE

This study investigated the differential gene expression of BMPs in chick retinal pigment epithelium (RPE) during recovery from short term exposure to optical defocus and form-deprivation (FD) treatments.

METHODS

14-day old White-Leghorn chicks wore either monocular +10 or -10 D lenses, or diffusers for 2 or 48 h, after which eyes were allowed unobstructed vision for up to 96 h. Over this recovery period, refractive errors and choroidal thickness (ChT) were tracked using retinoscopy and high-frequency A-scan ultrasonography. Real-time PCR was used to examine the expression of BMP2, 4, and 7 genes in RPE samples collected 0, 15 min, 2, 24, 48, and 96 h after the termination of treatments. Expression levels in treated eyes and their contralateral control eyes were compared.

RESULTS

After the termination of the lens and diffuser treatments, eyes gradually recovered from induced shifts in refractive error. With all three treatments, ChT changes reached statistical significance after 48 h of treatment, be it thinning with the -10 D lens and diffuser treatments (-0.06 ± 0.03mm, p < 0.05; -0.11 ± 0.04 mm, p < 0.05, resp.), or thickening with the +10 D lens (0.31 ± 0.04 mm, p < 0.001). BMP2 gene expression was rapidly upregulated in eyes wearing the +10 D lens, being statistical significance after 2 h, as well as 48 h of treatment. With the 2 h treatment, the latter gene expression pattern persisted for 15 min into the recovery period, before decreasing to the same level as that of contralateral control eyes, with a short-lived rebound, i.e., upregulation, 24 h into the recovery period. With the longer, 48 h treatment, BMP2 gene expression decreased more gradually, from 739 ± 121% at the end of the treatment period, to 72 ± 14% after 48 h of recovery. Two and 48 h of both -10 D and FD treatments resulted in BMP2 gene expression downregulation, with the time taken for gene expression levels to fully recover varying with the duration of initial treatments. In both cases, BMP2 gene expression downregulation persisted for 15 min into the recovery period, but reversed to upregulation by 2 h. Similar gene expression patterns were also observed for BMP4, although the changes were smaller.

CONCLUSIONS

The observed changes in BMP gene expression in chick RPE imply dynamic, albeit complex regulation, with the duration of exposure and recovery being critical variables for all three types of visual manipulations. This study provides further evidence for a role of the RPE as an important signal relay linking the retina to the choroid and sclera in eye growth regulation.

Investigation roles of Adamts1 and Adamts5 in scleral fibroblasts under hypoxia and mice with form-deprived myopia

Scleral hypoxia is considered a trigger in scleral remodeling-induced myopia. Identifying differentially expressed molecules within the sclera is essential for understanding the mechanism of myopia. We developed a scleral fibroblast hypoxia model and conducted RNA sequencing and bioinformatic analysis. RNA interference technology was then applied to knock down targeted genes with upregulated expression, followed by an analysis of COLLAGEN I protein level. Microarray data analysis showed that the expression of Adamts1 and Adamts5 were upregulated in fibroblasts under hypoxia (t-test, p < 0.05). Western blot analysis confirmed increased protein levels of ADAMTS1 and ADAMTS5, and a concurrent decrease in COLLAGEN I in hypoxic fibroblasts. The knockdown of either Adamts1 or Adamts5 in scleral fibroblasts under hypoxia resulted in an upregulation of COLLAGEN I. Moreover, a form-deprivation myopia (FDM) mouse model was established for validation. The sclera tissue from FDM mice exhibited increased levels of ADAMTS1 and ADAMTS5 protein and a decrease in COLLAGEN I, compared to controls. The study suggests that Adamts1 and Adamts5 may be involved in scleral remodeling induced by hypoxia and the development of myopia.

Capturing sclera anisotropy using direct collagen fiber models. Linking microstructure to macroscopic mechanical properties

Because of the crucial role of collagen fibers on soft tissue mechanics, there is great interest in techniques to incorporate them in computational models. Recently we introduced a direct fiber modeling approach for sclera based on representing the long-interwoven fibers. Our method differs from the conventional continuum approach to modeling sclera that homogenizes the fibers and describes them as statistical distributions for each element. At large scale our method captured gross collagen fiber bundle architecture from histology and experimental intraocular pressure-induced deformations. At small scale, a direct fiber model of a sclera sample reproduced equi-biaxial experimental behavior from the literature. In this study our goal was a much more challenging task for the direct fiber modeling: to capture specimen-specific 3D fiber architecture and anisotropic mechanics of four sclera samples tested under equibiaxial and four non-equibiaxial loadings. Samples of sclera from three eyes were isolated and tested in five biaxial loadings following an approach previously reported. Using microstructural architecture from polarized light microscopy we then created specimen-specific direct fiber models. Model fiber orientations agreed well with the histological information (adjusted R2's>0.89). Through an inverse-fitting process we determined model characteristics, including specimen-specific fiber mechanical properties to match equibiaxial loading. Interestingly, the equibiaxial properties also reproduced all the non-equibiaxial behaviors. These results indicate that the direct fiber modeling method naturally accounted for tissue anisotropy within its fiber structure. Direct fiber modeling is therefore a promising approach to understand how macroscopic behavior arises from microstructure.

Revealing regional variations in scleral shear modulus in a rabbit eye model using multi-directional ultrasound optical coherence elastography

The mechanical properties of the sclera play a critical role in supporting the ocular structure and maintaining its shape. However, non-invasive measurements to quantify scleral biomechanics remain challenging. Recently introduced multi-directional optical coherence elastography (OCE) combined with an air-coupled ultrasound transducer for excitation of elastic surface waves was used to estimate phase speed and shear modulus in ex vivo rabbit globes (n = 7). The scleral phase speed (12.1 ± 3.2 m/s) was directional-dependent and higher than for corneal tissue (5.9 ± 1.4 m/s). In the tested locations, the sclera proved to be more anisotropic than the cornea by a factor of 11 in the maximum of modified planar anisotropy coefficient. The scleral shear moduli, estimated using a modified Rayleigh-Lamb wave model, showed significantly higher values in the circumferential direction (65.4 ± 31.9 kPa) than in meridional (22.5 ± 7.2 kPa); and in the anterior zone (27.3 ± 9.3 kPa) than in the posterior zone (17.8 ± 7.4 kPa). The multi-directional scanning approach allowed both quantification and radial mapping of estimated parameters within a single measurement. The results indicate that multi-directional OCE provides a valuable non-invasive assessment of scleral tissue properties that may be useful in the development of improved ocular models, the evaluation of potential myopia treatment strategies, and disease characterization and monitoring.

Palladium nanocrystals regulates scleral extracellular matrix remodeling in myopic progression by modulating the hypoxia signaling pathway Nrf-2/Ho-1

Myopia represents a widespread global public health concern influenced by a combination of environmental and genetic factors. The prevailing theory explaining myopia development revolves around scleral extracellular matrix (ECM) remodeling, characterized by diminished Type I collagen (Col-1) synthesis and increased degradation, resulting in scleral thinning and eye axis elongation. Existing studies underscore the pivotal role of scleral hypoxia in myopic scleral remodeling. This study investigates the peroxidase-like activity and catalytic performance of octahedral Palladium (Pd) nanocrystals, recognized as nanozymes with antioxidative properties. We explore their potential in reducing oxidative stress and alleviating hypoxia in human scleral fibroblasts (HSF) and examine the associated molecular mechanisms. Our results demonstrate the significant peroxidase-like activity of Pd nanocrystals. Furthermore, we observe a substantial reduction in oxidative stress in HSF under hypoxia, mitigating cellular damage. These effects are linked to alterations in Nrf-2/Ho-1 expression, a pathway associated with hypoxic stress. Importantly, our findings indicate that Pd nanocrystals contribute to attenuated scleral matrix remodeling in myopic guinea pigs, effectively slowing myopia progression. This supports the hypothesis that Pd nanocrystals regulate myopia development by controlling oxidative stress associated with hypoxia. Based on these results, we propose that Pd nanocrystals represent a novel and potential treatment avenue for myopia through the modulation of scleral matrix remodeling. This study introduces innovative ideas and directions for the treatment and prevention of myopia.

Effects of 2 Hz flickering light on refractive state, fundus imaging and visual function of C57BL/6 mice

In this study, we investigated the effects of flickering light on refractive development of mice and the changes of fundus structure and function during this process. C57BL/6 mice were randomly divided into control group and flickering light-induced myopia (FLM) group. Mice in the control group were fed under normal lighting. FLM group mice were fed under lighting with a duty cycle of 50% and flash frequency of 2 Hz. Refractive status, axial length (AL), corneal radius of curvature (CRC), and electroretinogram signals were measured in all animals before treatment and at 2 and 4 weeks after treatment. Retinal thickness (RT), choroidal thickness (ChT) and choroidal blood perfusion (ChBP) were measured by optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA). After 4 weeks of flickering light stimulation, the mice became myopia, the AL increased, but the CRC remained constant. The induction of myopia reduced the implicit time and amplitude of a-wave and b-wave in electroretinogram, which affects the function of retina. Full-layer retinal thickness, ChT and ChBP decreased at both 2 and 4 weeks after flickering light induction. The superficial and middle layers of the retina were significantly thinner, while the deep layer was only slightly thinner without statistical significance. Calculated by the concentric circle algorithm, the decrease of choroidal blood perfusion in FLM was mainly concentrated in the concentric circle area with the optic disc as the center radius of 150-450 μm. In conclusion, the present study shows that flickering light can successfully induce myopia in C57BL/6 mice, affect the electrophysiological activity of retina, and cause changes in fundus tissue structure and blood flow.

Insights into Myopia from Mouse Models

Animal models are critical for understanding the initiation and progression of myopia, a refractive condition that causes blurred distance vision. The prevalence of myopia is rapidly increasing worldwide, and myopia increases the risk of developing potentially blinding diseases. Current pharmacological, optical, and environmental interventions attenuate myopia progression in children, but it is still unclear how this occurs or how these interventions can be improved to increase their protective effects. To optimize myopia interventions, directed mechanistic studies are needed. The mouse model is well-suited to these studies because of its well-characterized visual system and the genetic experimental tools available, which can be combined with pharmacological and environmental manipulations for powerful investigations of causation. This review describes aspects of the mouse visual system that support its use as a myopia model and presents genetic, pharmacological, and environmental studies that significantly contribute to our understanding of the mechanisms that underlie myopigenesis.

Radius-Maumenee syndrome-associated glaucoma, a therapeutic challenge: A case report

INTRODUCTION

Radius-Maumenee syndrome is a rare cause of open-angle glaucoma, secondary to elevated episcleral venous pressure (EVP) without any orbital or systemic abnormalities.

CASE PRESENTATION

We present a case of a male patient in his mid-sixties, who presented with bilateral dilated episcleral vessels, bilateral glaucoma, chorioretinal folds in both maculae and choroidal effusion in his left eye. Our case highlights the differentials that should be considered and the systematic investigations that should be performed. We describe the clinical, optical coherence tomography and angiography findings of this patient and propose a potential pathophysiological mechanism leading to the propensity for perioperative complications.

CONCLUSION

Radius-Maumenee syndrome should be a diagnosis of exclusion. Secondary glaucoma can remain refractory to medical treatment and filtering surgery carries the risk intra-operative or post-operative uveal effusions.

Collagen is crucial target protein for scleral remodeling and biomechanical change in myopia progression and control

In recent decades, the prevalence of myopia has been on the rise globally, attributed to changes in living environments and lifestyles. This increase in myopia has become a significant public health concern. High myopia can result in thinning of the sclera and localized ectasia of the posterior sclera, which is the primary risk factor for various eye diseases and significantly impacts patients' quality of life. Therefore, it is essential to explore effective prevention strategies and programs for individuals with myopia. Collagen serves as the principal molecule in the extracellular matrix (ECM) of scleral tissue, consisting of irregular collagen fibrils. Collagen plays a crucial role in myopia progression and control. During the development of myopia, the sclera undergoes a thinning process which is primarily influenced by collagen expression decreased and remodeled, thus leading to a decrease in its biomechanical properties. Improving collagen expression and promoting collagen crosslinking can slow down the progression of myopia. In light of the above, improving collagen expression or enhancing the mechanical properties of collagen fibers via medication or surgery represents a promising approach to control myopia.

Association of choroidal thickness and blood flow features with asymmetric axial lengths in children with unilateral myopic anisometropia

BACKGROUND

Considering that changes in the choroidal thickness are closely related to ocular growth, we studied the choroidal thickness (CT) and the blood flow features in children with unilateral myopic anisometropia (UMA) as well as investigating the relationship between choroidal changes and myopia.

METHODS

Subjective refractive, axial length (AL), and biometric parameters were measured in 98 UMA children (age: 8-15 years). CT and choroidal blood-flow features, including the choroidal vessel volume (CVV), choroidal vascularity index (CVI), and choriocapillaris perfusion area (CCPA), were measured through swept-source optical coherence tomography angiography. The macular region was categorized into four concentric circles of diameters 0-1 mm (central fovea), 1-3 mm (parafovea), 3-6 mm (perifovea), and 6-9 mm (extended), and further categorized into superior (S), inferior (I), temporal (T), and nasal (N) quadrants.

RESULTS

The aforementioned four regions of myopic eyes displayed significantly lower CT, CVV, and CVI than those of non-myopic eyes. CCPA changes differed across different regions of both the eyes (parts of N and T quadrants). There was an inverse association between CT and the interocular AL difference (central and other regions S, T quadrant). No correlation was noted between CVV and CVI with interocular AL difference. CT and CVV were positively correlated in the 0-6-mm macular region of myopic eyes (Spearman correlation coefficient = 0.763, P < 0.001).

CONCLUSIONS

In UMA children, CCT and blood flow may be related to myopia progression. A robust correlation between CT and CVV in the 0-6-mm macular region and reduced CT and diminished blood flow indicated an association with myopia.

Recent Advances in the Use of Cubosomes as Drug Carriers with Special Emphasis on Topical Applications

Topical drug delivery employing drug nanocarriers has shown prominent results in treating topical ailments, especially those confined to the skin and eyes. Conventional topical formulations persist with drug and disease-related challenges during treatment. Various nanotechnology-driven approaches have been adopted to mitigate the issues associated with conventional formulations. Among these, cubosomes have shown potential applications owing to their liquid crystalline structure, which aids in bioadhesion, retention, sustained release, and loading hydrophilic and hydrophobic moieties. The phase transition behavior of glyceryl monooleate, the concentration of stabilizers, and critical packing parameters are crucial parameters that affect the formation of cubosomes. Microfluidics-based approaches constitute a recent advance in technologies for generating stable cubosomes. This review covers the recent topical applications of cubosomes for treating skin (psoriasis, skin cancer, cutaneous candidiasis, acne, and alopecia) and eye (fungal keratitis, glaucoma, conjunctivitis, and uveitis) diseases. The article summarizes the manufacturing and biological challenges (skin and ocular barriers) that must be considered and encountered for successful clinical outcomes. The patented products are successful examples of technological advancements within cosmeceuticals that support various topical applications with cubosomes in the pharmaceutical field.

Targeting MicroRNA in myopia: Current insights

Myopia, the most prevalent eye condition, has sparked notable interest regarding its origin and prevention. MicroRNAs (miRNAs) are short, non-coding RNA strands typically consisting of 18-24 nucleotides. They play a central role in post-transcriptional gene regulation and are closely associated with both normal and pathological processes in organisms. Recent advances in next-generation sequencing and bioinformatics have provided novel insights into miRNA expression and its regulatory role in myopia. This review discusses the distinct expression patterns, regulatory functions, and potential pathways of miRNAs involved in the onset and progression of myopia. The primary objective of this review was to provide valuable insights into molecular mechanisms underlying myopia and the contribution of miRNAs. These insights are expected to pave the way for further exploration of the molecular mechanisms, diagnosis, treatment, and clinical applications of myopia.

Observation of structural and vascular features of retina and choroid in myopia using ultra-widefield SS-OCTA

BACKGROUND

To find the relationship between the changes of retinal and choriodal structure/ vascular densities (VD) and the myopia progress.

METHODS

126 eyes of 126 age-matched young participants were divided into three groups: Emmetropia and Low Myopia (EaLM) (33 eyes), Moderate Myopia (MM) (39 eyes), and High Myopia (HM) (54 eyes). Fundus images measuring 12 × 12 mm were captured using ultra-widefield swept-source optical coherence tomography angiography (SS-OCTA). Each image was uniformly divided into nine regions: supra-temporal (ST), temporal (T), infra-temporal (IT), superior (S), central macular area (C), inferior (I), supra-nasal (SN), nasal (N), and infra-nasal (IN). Various structural parameters, including inner retina thickness (IRT), outer retina thickness (ORT), and choroid thickness (CT), were assessed, and the VD of the superficial capillary plexus (SCP), deep capillary plexus (DCP), choriocapillaries (CC), and choroid vessels (ChdV) were quantified.

RESULTS

CT in upper fundus exhibited a significant reduction from EaLM to MM. Additionally, ORT (ST, S. SN, C, N, IT, I, IN), CT (ST, S, SN, T, C, N, IT, I, IN) and VDs of SCP (ST, S, C, I, IN), DCP (ST, S, T, C, I) and ChdV (T, N, I, IN) were statistically diminished in EaLM compared to HM. Furthermore, IRT (N), ORT (N, IN), CT (S, SN, T, C, IT, I) and VDs of SCP (I, IN) and DCP (I) exhibited significant decreases as MM progressed towards HM. Intriguingly, there was a notable increase in the VD of CC (ST, S, T, C, N) as myopia progressed from MM to HM.

CONCLUSION

Significant changes in retinal and choroid structure and vascular density occur as moderate myopia advances to high myopia. Efforts to curb myopia progression to this stage are essential, as the failure to do so may lead to the development of corresponding retinopathy.

Assessment of the systemic immune-inflammation index in type 2 diabetic patients with and without dry eye disease: A case-control study

Background

The inflammation plays a role in the pathophysiology of type-2 diabetes progression, and the mechanism remains unclear. The systemic immune-inflammation index (SII) is a novel inflammatory marker for type 2 diabetes patients and integrates multiple indicators in complete blood counts and routine blood tests.

Aim

Since there is no international diagnostic standard for dry eye disease (DED), this study uses low-cost inflammatory blood biomarkers to investigate the correlation between SII and DM2-DED and determine the diagnosis indices of other biomarkers in DM2-DED.

Methodology

A case-control retrospective analysis of totel patients n = 293 randomly selected and categorized into four groups: DED, DM2, DM2-DED, and healthy subjects. Demographic and blood biomarker variables were classified as categorical and continuous variables. The platelet-to-lymphocyte ratio (PLR), lymphocytes-to-lymphocyte ratio, neutrophil-to-lymphocyte ratio (NLR), and SII were calculated platelet count multiply by NLR and analyzed for their correlation for all groups.

Results

Focusing on DM2-DED patients was more common in females, 59.6%, than in males, 40.2%. The mean ages were 60.7 ± 11.85 years, a statistically significant difference with all groups. In the study group DM2-DED, there was an increase in all blood markers compared to all remaining groups except PLR. Only neutrophil, hemoglobin A1c (HbA1c), and fasting blood sugar levels were statistically significant differences in DM2-DED patients (p > 0.001, p < 0.001, and p < 0.001, respectively) compared to all groups. There was a positive correlation between HbA1c and PLR, HbA1c and NLR, and HbA1c and SII (r = 0.037, p = 0.705; r = 0.031, p = 0.754; and r = 0.066, p < 0.501, respectively) in the DM2-DED group.

Conclusion

This study demonstrated that elevated SII values were linked to elevated HbA1c in DM2-DED patients. The potential of SII and HbA1c as early diagnostic indicators for ocular problems associated with diabetes mellitus is highlighted by their favorable connection in diagnosing DM2-DED.

Vesicular Drug Delivery Systems: Promising Approaches in Ocular Drug Delivery

Ocular drug delivery poses unique challenges due to the complex anatomical and physiological barriers of the eye. Conventional dosage forms often fail to achieve optimal therapeutic outcomes due to poor bioavailability, short retention time, and off-target effects. In recent years, vesicular drug delivery systems have emerged as promising solutions to address these challenges. Vesicular systems, such as liposome, niosome, ethosome, transfersome, and others (bilosome, transethosome, cubosome, proniosome, chitosome, terpesome, phytosome, discome, and spanlastics), offer several advantages for ocular drug delivery. These include improved drug bioavailability, prolonged retention time on the ocular surface, reduced systemic side effects, and protection of drugs from enzymatic degradation and dilution by tears. Moreover, vesicular formulations can be engineered for targeted delivery to specific ocular tissues or cells, enhancing therapeutic efficacy while minimizing off-target effects. They also enable the encapsulation of a wide range of drug molecules, including hydrophilic, hydrophobic, and macromolecular drugs, and the possibility of combination therapy by facilitating the co-delivery of multiple drugs. This review examines vesicular drug delivery systems, their advantages over conventional drug delivery systems, production techniques, and their applications in management of ocular diseases.

Augmentation of scleral glycolysis promotes myopia through histone lactylation

Myopia is characterized of maladaptive increases in scleral fibroblast-to-myofibroblast transdifferentiation (FMT). Scleral hypoxia is a significant factor contributing to myopia, but how hypoxia induces myopia is poorly understood. Here, we showed that myopia in mice and guinea pigs was associated with hypoxia-induced increases in key glycolytic enzymes expression and lactate levels in the sclera. Promotion of scleral glycolysis or lactate production induced FMT and myopia; conversely, suppression of glycolysis or lactate production eliminated or inhibited FMT and myopia. Mechanistically, increasing scleral glycolysis-lactate levels promoted FMT and myopia via H3K18la, and this promoted Notch1 expression. Genetic analyses identified a significant enrichment of two genes encoding glycolytic enzymes, ENO2 and TPI1. Moreover, increasing sugar intake in guinea pigs not only induced myopia but also enhanced the response to myopia induction via the scleral glycolysis-lactate-histone lactylation pathway. Collectively, we suggest that scleral glycolysis contributes to myopia by promoting FMT via lactate-induced histone lactylation.

Analysis and validation of potential ICD-related biomarkers in development of myopia using machine learning

PURPOSE

We aimed to identify and verify potential biomarkers in the development of myopia associated with immunogenic cell death (ICD).

METHODS

We download high myopia (HM) dataset GSE136701 from Gene Expression Omnibus. Differentially expressed genes in HM were identified to overlapped with ICD-related genes. Least absolute shrinkage and selection operator were used to select the Hub genes. Furthermore, the correlation between the hub genes and immune infiltration, immune response activities, and hub genes Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways analysis was investigated using Spearman's rank correlation. Prediction of the miRNAs upstream of the Hub genes was based on the TargetScan database. We used guinea pig lens-induced myopia model's scleral tissues performed quantitative real-time polymerase chain reaction.

RESULTS

We identified overlapped with ICD-related genes (LY96, IL1A, IL33, and AGER) and two genes (LY96 and AGER) as hub genes. Single sample gene set enrichment analysis and Spearman's rank correlation revealed that hub gene expression levels in HM were significantly correlated with the infiltration percentages of CD56dim natural killer cells, macrophages, immature B cells, and the immune response activities of APC co-stimulation and Kyoto Encyclopedia of Genes and Genomes pathways, such as terpenoid backbone biosynthesis, aminoacyl-trna biosynthesis, Huntington's disease, oxidative phosphorylation; there were a few additional signaling pathways compared to normal samples. Additionally, several miRNA were predicted as upstream regulators of LY96 and AGER. LY96 was identified as a significantly differentially expressed biomarker in myopia guinea pig's scleral tissues, as verified by qPCR.

CONCLUSION

LY96 was identified and verified as a ICD-related potential myopia biomarker. Molecular mechanisms or pathways involved in myopia development by LY96 requires further research.

Biometry-Based Technique for Determining the Anterior Scleral Thickness: Validation Using Optical Coherence Tomography Landmarks

Purpose

Considering the potential role of anterior scleral thickness (AST) in myopia and the ubiquitous use of optical biometers, we applied and validated a biometry-based technique for estimating AST using optical coherence tomography (OCT) landmarks.

Methods

The AST was determined across four meridians in 62 participants (aged 20-37 years) with a swept-source OCT and a noncontact optical biometer at a mean ± SD distance of 3.13 ± 0.88 mm from the limbus. The biometer's graticule was focused and aligned with the anterior scleral reflex, which led to the generation of four prominent A-scan peaks: P1 (anterior bulbar conjunctiva), P2 (anterior episclera), P3 (anterior margin of anterior sclera), and P4 (posterior margin of anterior sclera), which were analyzed and compared with the corresponding OCT landmarks to determine tissue thickness.

Results

The AST measurements between biometer and OCT correlated for all meridians (r ≥ 0.70, overall r = 0.82; coefficient of variation [CV], 9%-12%; P < 0.01). The mean difference ± SD between two instruments for overall AST measures was 3 ± 2.8 µm (range, -18 to +16 µm; lower limits of agreement, -89 to +83 µm; P = 0.23) across all meridians. The mean ± SE AST with both instruments was found to be thickest at the inferior (562 ± 7 µm and 578 ± 7 µm) and thinnest at the superior (451 ± 7 µm and 433 ± 6 µm) meridian. The biometer demonstrated good intrasession (CV, 8.4%-9.6%) and intersession (CV, 7.9%-13.3%) repeatability for AST measurements across all meridians.

Conclusions

The noncontact optical biometer, which is typically used to determine axial length, is capable of accurately estimating AST based on OCT landmarks.

Translational Relevance

The high-resolution optical biometers can demonstrate wider application in the field of myopia research and practice to determine AST.

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.

Up-regulation of scleral C5b-9 and its regulation of the NLRP3 inflammasome in a form-deprivation myopia mouse model

BACKGROUND

Myopia has become a major public health problem worldwide. Although the involvement of the complement system in myopia progression has been reported, the underlying mechanism has not been well established. In this study, we induced a form deprivation (FD) myopia mouse model to investigate the mechanisms.

METHODS

Both C6-knockout (KO) and wild-type (WT) mice were divided into FD and normal control (NC) groups. The FD myopia was induced in the right eyes of 24-day-old mice using a translucent balloon for 4 weeks. The left eye remained untreated and served as self-control. NC group received no treatment. Refractive error and axial length were measured at baseline, 2 weeks, and 4 weeks later under normal visual, 4 weeks after FD. Scleral transcriptome sequencing analysis was performed in in FD mice. The scleral levels of C5b-9, NLRP3, Caspase-1, IL-1β, MMP-2, and collagen I were evaluated using immunohistochemistry.

RESULTS

RNA-seq analysis showed 1058 differentially expressed genes. The GO analysis showed these genes were mainly related to the extracellular matrix, and immune response. The KEGG enrichment analysis showed that complement cascades were upregulated. Under normal visual conditions, both genotypes of mice exhibited comparable refractive error and axial length. However, after four weeks of FD, C6-KO mice showed a significantly less myopic shift (-2.28 ± 0.28 D versus -5.40 ± 1.33 D, P = 0.003), and axial shift (0.043 ± 0.032 mm versus 0.083 ± 0.026 mm, P = 0.042) in comparison to WT mice. Furthermore, the levels of C5b-9, NLRP3, caspase-1, IL-1β, and MMP-2 were found to be elevated in the deprived eyes of WT mice in comparison to their fellow eyes, whereas the extent of this increase was significantly lower in C6-KO mice.

CONCLUSIONS

Complement cascades are activated in FD myopia model. Upregulation of C5b-9 might participate in scleral remodeling during myopia progression via regulation of NLRP3 inflammasome activation.

[Biomechanical control of myopia: potential of bidirectional corneal applanation with high-speed video recording]

The introduction of bidirectional corneal applanation technologies into clinical practice made possible the in vivo assessment of biomechanical properties of the fibrous tunic in myopic eyes.

PURPOSE

This study analyzes the potential of bidirectional corneal applanation with high-speed video recording for biomechanical control of myopia, focusing on the biomechanical parameters of the sclera and cornea.

MATERIAL AND METHODS

The study included 129 patients (168 eyes) with myopia ranging from -0.75 to -13.25 D in spherical equivalent. The axial length (AL) and central corneal thickness (CCT) ranged from 22.64 to 29.05 mm and from 492 to 644 µm, respectively. AL was measured using laser biometry, CCT with a rotating Scheimpflug camera, and the biomechanical properties of the fibrous tunic were assessed using bidirectional corneal pneumatic applanation with high-speed video recording using the Corvis ST device.

RESULTS

A weak positive correlation was found between AL and CCT, while no significant correlation was observed between CCT and the stress-strain index (SSI). However, there was a significant negative correlation between SSI and AL. Additionally, a clear and statistically significant trend of decreasing SSI with increasing AL was identified.

CONCLUSION

The stress-strain index (SSI), determined using bidirectional corneal pneumatic applanation with high-speed video recording, could potentially be considered a clinical indicator characterizing the scleral component of the ocular fibrous tunic in the biomechanical control of myopia.

Lipid Metabolism Regulators Are the Possible Determinant for Characteristics of Myopic Human Scleral Stroma Fibroblasts (HSSFs)

The purpose of the current investigation was to elucidate what kinds of responsible mechanisms induce elongation of the sclera in myopic eyes. To do this, two-dimensional (2D) cultures of human scleral stromal fibroblasts (HSSFs) obtained from eyes with two different axial length (AL) groups, <26 mm (low AL group, n = 2) and >27 mm (high AL group, n = 3), were subjected to (1) measurements of Seahorse mitochondrial and glycolytic indices to evaluate biological aspects and (2) analysis by RNA sequencing. Extracellular flux analysis revealed that metabolic indices related to mitochondrial and glycolytic functions were higher in the low AL group than in the high AL group, suggesting that metabolic activities of HSSF cells are different depending the degree of AL. Based upon RNA sequencing of these low and high AL groups, the bioinformatic analyses using gene ontology (GO) enrichment analysis and ingenuity pathway analysis (IPA) of differentially expressed genes (DEGs) identified that sterol regulatory element-binding transcription factor 2 (SREBF2) is both a possible upstream regulator and a causal network regulator. Furthermore, SREBF1, insulin-induced gene 1 (INSIG1), and insulin-like growth factor 1 (IGF1) were detected as upstream regulators, and protein tyrosine phosphatase receptor type O (PTPRO) was detected as a causal network regulator. Since those possible regulators were all pivotally involved in lipid metabolisms including fatty acid (FA), triglyceride (TG) and cholesterol (Chol) biosynthesis, the findings reported here indicate that FA, TG and Chol biosynthesis regulation may be responsible mechanisms inducing AL elongation via HSSF.

Characteristics of ciliary muscle profile in high myopes measured by swept-source anterior segment optical coherence tomography

OBJECTIVE

To characterize and compare the ciliary muscle thickness (CMT) between low and high myopes using swept-source anterior segment optical coherence tomography (AS-OCT).

METHODS

Forty visually healthy young Chinese adults aged 18-25 years were divided into two groups based on refractive errors: low myopia (n = 20, spherical-equivalent refractive error (SER) between -0.50 D to -3.00 D) and high myopia (n = 20, SER ≤ -6.00 D). Cycloplegic refractions were performed before axial length (AL) and CMT were measured using a partial coherence laser interferometer and an AS-OCT respectively. CMT was measured perpendicularly to the sclera-ciliary muscle interface at 1 mm (CMT_1), 2 mm (CMT_2), and 3 mm (CMT_3) posterior to the scleral spur, and at the location with maximal thickness (CMT_MAX).

RESULTS

High myopes demonstrated thicker CMT at 2 mm (CMT_2, p = 0.035) and 3 mm (CMT_3, p = 0.003) posterior to the scleral spur, but thinner maximal CMT (CMT_MAX, p = 0.005) than low myopes. The apical CMT_1 and CMT_MAX were also thinner in high myopes than in low myopes (both p< 0.001). CMT_MAX, apical CMT_1, and apical CMT_MAX correlated directly with SER and inversely with AL; in contrast, CMT_2 and CMT_3 showed inverse correlations with SER but direct correlations with AL.

CONCLUSION

Our findings revealed significant differences in CMT between low and high myopes, with high myopes showing thicker CMT at 2 mm and 3 mm posterior to the scleral spur, but thinner maximal CMT. These results provide new evidence of the potential structural differences in ciliary muscles during myopia development and progression.

LncRNA-XR_002792574.1-mediated ceRNA network reveals potential biomarkers in myopia-induced retinal ganglion cell damage

BACKGROUND

Long noncoding RNAs (lncRNAs) play a key role in the occurrence and progression of myopia. However, the function of lncRNAs in retinal ganglion cells (RGCs) in the pathogenesis of myopia is still unknown. The aim of our study was to explore the lncRNA-mediated competing endogenous RNA (ceRNA) network in RGCs during the development of myopia.

METHODS

RNA sequencing was performed to analyze lncRNA and mRNA expression profiles in RGCs between guinea pigs with form-deprived myopia (FDM) and normal control guinea pigs, and related ceRNA networks were constructed. Then, potentially important genes in ceRNA networks were verified by qRT‒PCR, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed to explore biological functions in the RGCs of FDM guinea pigs. The important genes and related signaling pathways were further verified by qRT‒PCR, immunohistochemistry, immunofluorescence and Western blot in myopia in FDM guinea pigs, FDM mice, and highly myopic adults.

RESULTS

The distribution of RGCs was uneven, the number of RGCs was decreased, and RGC apoptosis was increased in FDM guinea pigs. In total, 873 lncRNAs and 2480 mRNAs were determined to be differentially expressed genes in RGCs from normal control and FDM guinea pigs. Via lncRNA-mediated ceRNA network construction and PCR verification, we found that lncRNA-XR_002792574.1 may be involved in the development of myopia through the miR-760-3p/Adcy1 pathway in RGCs. Further verification in FDM guinea pigs, FDM mice, and highly myopic adults demonstrated that the lncRNA-XR_002792574.1/miR-760-3p/Adcy1 axis in RGCs might be related to cGMP/PKG, the apelin signaling pathway and scleral remodeling.

CONCLUSION

We demonstrated that the lncRNA-XR_002792574.1/miR-760-3p/Adcy1 axis in RGCs might be related to myopia. On the one hand, the lncRNA-XR_002792574.1/miR-760-3p/Adcy1 axis might inhibit the cGMP/PKG and apelin signaling pathways in RGCs, thereby causing RGC damage in myopia. On the other hand, the lncRNA-XR_002792574.1/miR-760-3p/Adcy1 axis may cause myopic scleral remodeling through the ERK-MMP-2 pathway. These findings may reveal novel potential targets in myopia and provide reference value for exploration and development of gene editing therapeutics for hereditary myopia.

Quantization of Optic Disc Characteristics in Young Adults Based on Artificial Intelligence

PURPOSE

This study aimed to automatically and quantitatively analyse the characteristics of the optic disc by applying artificial intelligence (AI) to fundus images.

METHODS

A total of 1084 undergraduates were recruited in this cross-sectional study. The optic disc area, cup-to-disc ratio (C/D), optic disc tilt, and the area, width, and height of peripapillary atrophy (PPA) were automatically and quantitatively detected using AI. Based on axial length (AL), participants were divided into five groups: Group 1 (AL ≤ 23 mm); Group 2 (23 mm < AL≤ 24 mm); Group 3 (24 mm < AL≤ 25 mm); Group 4 (25 mm < AL< 26 mm) and Group 5 (AL ≥ 26 mm). Relationships between ocular parameters and optic disc characteristics were analysed.

RESULT

A total of 999 undergraduates were included in the analysis. The prevalence of optic disc tilting and PPA were 47.1% and 92.5%, respectively, and increased with the severity of myopia. The mean optic disc area, PPA area, C/D, and optic disc tilt ratio were 1.97 ± 0.46 mm2, 0.84 ± 0.59 mm2, 0.18 ± 0.07, and 0.81 ± 0.08, respectively. In Group 5, the average optic disc area (1.84 ± 0.41 mm2) and optic disc tilt ratio (0.79 ± 0.08) were significantly smaller and the PPA area (1.12 ± 0.61 mm2) was significantly larger than those in the other groups. AL was negatively correlated with optic disc area and optic disc tilt ratio (r=-0.271, -0.219; both p < 0.001) and positively correlated with PPA area, width, and height (r = 0.421, 0.426, 0.345; all p < 0.01). A greater AL (β = 0.284, p < 0.01) and a smaller optic disc tilt ratio (β=-0.516, p < 0.01) were related to a larger PPA area.

CONCLUSION

The characteristics of the optic disc can be feasibly and efficiently extracted using AI. The quantization of the optic disc might provide new indicators for clinicians to evaluate the degree of myopia.

Intraperitoneal Injection of MCC950 Inhibits the Progression of Myopia in Form-Deprivation Myopic Mice

Myopia, one of the most prevalent ocular diseases worldwide, is projected to affect nearly half of the global population by 2050. The main cause of myopia in most patients is axial myopia, which primarily occurs due to the elongation of the eyeball, driven by changes in the extracellular matrix (ECM) of scleral cells. Previous studies have shown that NLRP3, an important inflammatory mediator, plays a critical role in regulating the expression of MMP-2 in the sclera. This, in turn, leads to a decrease in the expression of Collagen-1, a major component of the scleral ECM, triggering the remodeling of the scleral ECM. This study aimed to investigate the effect of MCC950, an inhibitor of NLRP3, on the progression of myopia using a mouse form-deprivation myopia (FDM) model. The FDM mouse model was constructed by subjecting three-week-old C57BL/6J mice to form-deprivation. The mice were divided into experimental (n = 10/group; FDM2M, FDM4M, FDM2W, and FDM4W) and control groups (n = 5/group). The experimental groups were further categorized based on the duration of form deprivation (2 and 4 weeks, labeled as 2 and 4, respectively) and the type of injection received (MCC950 or saline, labeled as M and W, respectively). MCC950 was injected at a concentration of 50 mg/mL, with a dose of 10 mg per kilogram of body weight. Meanwhile, the saline group received the same volume of saline. Refraction and axial length measurements were performed for each eye. The expression levels of NLRP3, caspase-1, IL-1β, IL-18, MMP-2, and Collagen-1 in the sclera were assessed using immunohistochemistry and Western blotting. The intraperitoneal injection of MCC950 did not significantly affect refraction or axial length in normal mice (p > 0.05). However, in FDM mice, MCC950 attenuated the elongation of the axial length and resulted in a smaller shift towards myopia compared to the saline group (FDM4M vs. FDM4W, p = 0.03 and p < 0.05, respectively). MCC950 decreased MMP-2 expression (p < 0.05) but increased Collagen-1 expression (p < 0.05) in the experimental eyes when compared to the saline group. Within the MCC950 group, the expression of MMP-2 was increased in the experimental eyes at 4 weeks (p < 0.05), while that of Collagen-1 was decreased (p < 0.05), which is consistent with changes in refractive error. Immunohistochemical analysis yielded similar results (p < 0.05). MCC950 also reduced the expression levels of NLRP3 (p = 0.03), caspase-1 (p < 0.05), IL-1β (p < 0.05), and IL-18 (p < 0.05) in the experimental eyes compared to the saline group. Within the MCC950 group, the expression levels of NLRP3 and caspase-1 were comparable between the experimental and control eyes (p > 0.05), whereas IL-18 expression was higher in experimental eyes (p < 0.05). IL-1β expression was higher in the experimental eyes only at week 4 (p < 0.05). The intraperitoneal injection of MCC950 can inhibit the progression of myopia in FDM mice, possibly by regulating collagen remodeling in the sclera through the NLRP3-MMP-2 signaling pathway. Therefore, MCC950 holds promise as a potential therapeutic agent for controlling the progression of myopia.

Choroidal thickness in relation to diopter and axial length among myopic children

Purpose

The aim of this study was to analyze the relationship between diopter (D) and choroidal thickness in myopic children by describing the values of choroidal thickness, and explore choroidal thickness as an important indicator for evaluating the progression of myopia.

Methods

The study included myopic and emmetropic children aged 6-14 years (156 eyes) from the Second Hospital of Dalian Medical University. The participants were divided into four groups according to the spherical equivalent refraction (SER): low myopes, moderate myopes, high myopes, and emmetropes. Choroidal thickness was measured in nine areas using the Early Treatment Diabetic Retinopathy Study (ETDRS) grid layout, which divided the areas into concentric circles of 0 × 0 mm, 3 × 3 mm, and 5 × 5 mm from the Sub Fovea. The images were obtained manually with spectral-domain optical coherence tomography scanner.

Results

There were significant differences of choroidal thickness in the nine areas of the ETDRS grid for all myopes. The distribution of choroidal thickness in low and moderate myopes were different from that in high myopes. In the horizontal direction, choroidal thickness decreased from the temporal to nasal areas for all myopes. In the vertical direction, the choroidal thickness in the perifovea was smaller than that in the parafovea (SER ≥ -2.75D), and the choroidal thickness in the perifovea was greater than that in the parafovea (SER < -2.75D). When comparing emmetropes with myopes, the closer the choroidal thickness was to the central fovea, the more significant the differences were, while the differences were smaller to the perifovea. Among all children, choroidal thickness was positive to SER and negative to axial length (AL) in all areas. For every 1D increase in myopia, the subfoveal choroidal thickness decreased by 13 μm, and for every 1 mm increase in AL, the subfoveal choroidal thickness decreased by 23 μm. Furthermore, SER and AL showed the strongest correlation with choroidal thickness in the inferior area.

Conclusion

Optical coherence tomography results revealed choroidal thickness was thinner in myopic children. Choroidal thickness was positive to SER and negative to AL. Therefore, we consider choroidal thickness to be an important indicator for evaluating the myopia progress.

Bisphenol A exposure triggers endoplasmic reticulum stress pathway leading to ocular axial elongation in mice

Background

Ocular axial elongation is one of the features of myopia progression. Endoplasmic reticulum (ER) stress-associated scleral remodeling plays an important role in ocular axial elongation. Bisphenol A (BPA) is one of the most common environmental pollutants and is known to affect various human organs through ER stress. However, whether BPA exerts an effect on scleral remodeling remains unknown. The purpose of this study was to determine the effect of BPA on the development of myopia and scleral ER stress.

Methods

BPA was administered by intraperitoneal injection. 4-PBA was administered as an endoplasmic reticulum stress inhibitor by eye drops. Refraction and axial length were measured by refractometer and SD-OCT system. Western blot was performed to detect the expression level of ER stress-related proteins.

Results

BPA-administered mice exhibit axial elongation and myopic refractive shift with endoplasmic reticulum stress in the sclera. BPA administration activated scleral PERK and ATF6 pathways, and 4-PBA eye drops attenuated ER stress response and suppressed myopia progression.

Conclusion

BPA controlled axial elongation during myopia development in a mouse model by inducing scleral ER stress and activation of the PERK/ATF6 pathway. 4-PBA eye drops as ER stress inhibitor suppressed BPA-induced myopia development.

Photobiomodulation at 660 nm promotes collagen synthesis via downregulation of HIF-1α expression without photodamage in human scleral fibroblasts in vitro in a hypoxic environment

PURPOSE

The increasing prevalence of myopia is a global public health issue. Because of the complexity of myopia pathogenesis, current control methods for myopia have great limitations. The aim of this study was to explore the effect of photobiomodulation (PBM) on human sclera fibroblasts (HSFs) under hypoxia, in the hope of providing new ideas for myopia prevention and control.

METHODS

Hypoxic cell model was established at 0, 6, 12, and 24 h time points to simulate myopia microenvironment and explore the optimal time point. Control, hypoxia, hypoxia plus light, and normal plus light cell models were set up for the experiments, and cells were incubated for 24 or 48 h after PBM (660 nm, 5 J/cm2), followed by evaluation of hypoxia-inducible factor 1α (HIF-1α) and collagen I a1 (COL1A1) proteins using Western blotting and immunofluorescence, and photo damage was detected by CCK-8, scratch test, and flow cytometry assays. We also used transfection technology to further elucidate the regulatory mechanism.

RESULTS

The change of target proteins is most obvious when hypoxia lasts for 24 h (p < 0.01). PBM at 660 nm increased extracellular collagen content (p < 0.001) and downregulated expression of HIF-1α (p < 0.05). This treatment did not affect the migration and proliferation of cells (p > 0.05), and effectively inhibited apoptosis under hypoxia (p < 0.0001). After overexpression of HIF-1α, the effect of PBM was attenuated (p > 0.05).

CONCLUSIONS

Photobiomodulation at 660 nm promotes collagen synthesis via downregulation of HIF-1α expression without photodamage.

Myopia: Histology, clinical features, and potential implications for the etiology of axial elongation

Myopic axial elongation is associated with various non-pathological changes. These include a decrease in photoreceptor cell and retinal pigment epithelium (RPE) cell density and retinal layer thickness, mainly in the retro-equatorial to equatorial regions; choroidal and scleral thinning pronounced at the posterior pole and least marked at the ora serrata; and a shift in Bruch's membrane opening (BMO) occurring in moderately myopic eyes and typically in the temporal/inferior direction. The BMO shift leads to an overhang of Bruch's membrane (BM) into the nasal intrapapillary compartment and BM absence in the temporal region (i.e., parapapillary gamma zone), optic disc ovalization due to shortening of the ophthalmoscopically visible horizontal disc diameter, fovea-optic disc distance elongation, reduction in angle kappa, and straightening/stretching of the papillomacular retinal blood vessels and retinal nerve fibers. Highly myopic eyes additionally show an enlargement of all layers of the optic nerve canal, elongation and thinning of the lamina cribrosa, peripapillary scleral flange (i.e., parapapillary delta zone) and peripapillary choroidal border tissue, and development of circular parapapillary beta, gamma, and delta zone. Pathological features of high myopia include development of macular linear RPE defects (lacquer cracks), which widen to round RPE defects (patchy atrophies) with central BM defects, macular neovascularization, myopic macular retinoschisis, and glaucomatous/glaucoma-like and non-glaucomatous optic neuropathy. BM thickness is unrelated to axial length. Including the change in eye shape from a sphere in emmetropia to a prolate (rotational) ellipsoid in myopia, the features may be explained by a primary BM enlargement in the retro-equatorial/equatorial region leading to axial elongation.

Cytological and functional effect of complement 3a on Human Scleral Fibroblasts

PURPOSE

The complement system is considered to play an important role in the progression of myopia, whereas the influence of complement activation on the human scleral fibroblasts (HSFs) remains unknown. Hence, the effect of complement 3a (C3a) on HSFs was investigated in this study.

METHODS

HSFs were cultured with exogenous C3a at 0.1 μM for various periods following different measurement protocols, and cells without C3a treatment served as negative control (NC). Cell viability was investigated using the MTS assay after 3 days of C3a treatment. Cell proliferation was evaluated by the 5-Ethynyl-20-Deoxyuridine (EdU) assay following C3a stimulation for 24 hours. Apoptosis was assessed by Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) double staining following C3a stimulation for 48 hours and the stained cells were analysed using flow cytometry. The levels of type I collagen and matrix metalloproteinase-2 (MMP-2) were analysed using ELISA following C3a stimulation for 36 and 60 hours. The level of CD59 were analysed using western blot following C3a stimulation for 60 hours.

RESULTS

The MTS assay revealed that cell viability was attenuated by 13% and 8% after C3a for 2 and 3 days, respectively (P < 0.05). The EdU assay demonstrated a 9% decrease in proliferation rate for the C3a-treated cells after 24 hours (P < 0.05). The apoptosis analysis revealed an increased percentage of cells in early apoptosis (P = 0.02) and total apoptosis (P = 0.02) in the C3a-treated group. Compared with NC group, the level of MMP-2 was increased by 17.6% (P = 0.002), whereas the levels of type I collagen and CD59 were respectively decreased by 12.5% (P = 0.024) and 21.6% (P = 0.044) with C3a treatment for 60 hours.

CONCLUSIONS

These results indicated that C3a-induced complement activation is potentially involved in inducing myopic-associated scleral extracellular matrix remodelling via mediating the proliferation and function of HSFs.

The Genetic Determinants of Axial Length: From Microphthalmia to High Myopia in Childhood

The axial length of the eye is critical for normal visual function by enabling light to precisely focus on the retina. The mean axial length of the adult human eye is 23.5 mm, but the molecular mechanisms regulating ocular axial length remain poorly understood. Underdevelopment can lead to microphthalmia (defined as a small eye with an axial length of less than 19 mm at 1 year of age or less than 21 mm in adulthood) within the first trimester of pregnancy. However, continued overgrowth can lead to axial high myopia (an enlarged eye with an axial length of 26.5 mm or more) at any age. Both conditions show high genetic and phenotypic heterogeneity associated with significant visual morbidity worldwide. More than 90 genes can contribute to microphthalmia, and several hundred genes are associated with myopia, yet diagnostic yields are low. Crucially, the genetic pathways underpinning the specification of eye size are only now being discovered, with evidence suggesting that shared molecular pathways regulate under- or overgrowth of the eye. Improving our mechanistic understanding of axial length determination will help better inform us of genotype-phenotype correlations in both microphthalmia and myopia, dissect gene-environment interactions in myopia, and develop postnatal therapies that may influence overall eye growth.

Therapeutic non-ectasia applications of cornea cross-linking

Corneal cross-linking is a photopolymerization technique traditionally used to strengthen corneal tissue. Corneal cross-linking utilizes riboflavin (vitamin B2) as a photosensitizer and ultraviolet-A light (UVA) to create strong covalent bonds within the corneal stroma, increasing tissue stiffness. Multiple studies have demonstrated corneal cross-linking's effectiveness in treating corneal ectasia, a progressive, degenerative, and non-inflammatory thinning disorder, as quantified by key tomographic, refractive, and visual parameters. Since its introduction two decades ago, corneal cross-linking has surpassed its original application in halting corneal ectatic disease and its application has expanded into several other areas. Corneal cross-linking also possesses antibacterial, antienzymolytic and antioedematous properties, and has since become a tool in treating microbial keratitis, correcting refractive error, preventing iatrogenic ectasia, stabilising bullous keratopathy and controlling post keratoplasty ametropia. This review provides an overview of the current evidence base for the therapeutic non-ectasia applications of cornea cross-linking and looks at future developments in the field.

Posterior scleral birefringence measured by triple-input polarization-sensitive imaging as a biomarker of myopia progression

In myopic eyes, pathological remodelling of collagen in the posterior sclera has mostly been observed ex vivo. Here we report the development of triple-input polarization-sensitive optical coherence tomography (OCT) for measuring posterior scleral birefringence. In guinea pigs and humans, the technique offers superior imaging sensitivities and accuracies than dual-input polarization-sensitive OCT. In 8-week-long studies with young guinea pigs, scleral birefringence was positively correlated with spherical equivalent refractive errors and predicted the onset of myopia. In a cross-sectional study involving adult individuals, scleral birefringence was associated with myopia status and negatively correlated with refractive errors. Triple-input polarization-sensitive OCT may help establish posterior scleral birefringence as a non-invasive biomarker for assessing the progression of myopia.

Nanotechnology-based ocular drug delivery systems: recent advances and future prospects

Ocular drug delivery has constantly challenged ophthalmologists and drug delivery scientists due to various anatomical and physiological barriers. Static and dynamic ocular barriers prevent the entry of exogenous substances and impede therapeutic agents' active absorption. This review elaborates on the anatomy of the eye and the associated constraints. Followed by an illustration of some common ocular diseases, including glaucoma and their current clinical therapies, emphasizing the significance of drug therapy in treating ocular diseases. Subsequently, advances in ocular drug delivery modalities, especially nanotechnology-based ocular drug delivery systems, are recommended, and some typical research is highlighted. Based on the related research, systematic and comprehensive characterizations of the nanocarriers are summarized, hoping to assist with future research. Besides, we summarize the nanotechnology-based ophthalmic drugs currently on the market or still in clinical trials and the recent patents of nanocarriers. Finally, inspired by current trends and therapeutic concepts, we provide an insight into the challenges faced by novel ocular drug delivery systems and further put forward directions for future research. We hope this review can provide inspiration and motivation for better design and development of novel ophthalmic formulations.