Scleral structure and biomechanics

Evaluation of Scleral Thickness in Patients With Keratoconus

OBJECTIVES

To evaluate scleral thickness of patients with keratoconus by anterior segment optical coherence tomography (AS-OCT).

MATERIALS AND METHODS

Fifty-two eyes of 42 patients with keratoconus (group 1) and 42 right eyes of 42 healthy individuals (group 2) were included. Scleral thickness measurements were taken with AS-OCT 6, 4, and 2 mm behind the scleral spur in four gaze positions: superior, inferior, temporal, and nasal. The data including central corneal thickness (CCT) by Pentacam from patients with keratoconus was also analyzed and its relationship with scleral thickness was evaluated.

RESULTS

In group 1, mean scleral thickness from 6 mm posterior to scleral spur in superior, inferior, temporal, and nasal quadrants were 397±35.3 (320-482), 408±29.5 (341-467), 393±40.8 (297-469), and 403±35.8 (310-482) μm, respectively. In group 2, mean scleral thickness from 6 mm posterior to scleral spur in superior, inferior, temporal, and nasal quadrants were 440±42.2 (346-552), 461±33.9 (390-563), 451±46.6 (340-549) and 448±34.3 (350-521) μm, respectively. The mean scleral thickness in group 1 was significantly lower in all quadrants compared with group 2 (P<0.001). The mean CCT in group 1 was 478.22±87.55 (306-632) μm. Positive correlation was found between scleral thickness measurements taken at 4 mm (ϱ=0.312, P=0.037) and 2 mm (ϱ=0.308, P=0.039) posterior from the scleral spur in the inferior quadrant and CCT.

CONCLUSION

Scleral thickness was significantly lower in patients with keratoconus. Scleral thickness and CCT were positively correlated in inferior quadrant. Even though it is not yet known whether scleral changes are progressive or not, scleral thickness measurement may also find a place in the diagnosis and follow-up of patients with keratoconus in the future.

The Ocular Surface and the Anterior Segment of the Eye in the Pseudoexfoliation Syndrome: A Comprehensive Review

Pseudoexfoliation syndrome (PXS) is an age-related fibrillopathy where fibrillar exfoliation material accumulates and deposits in ocular and extra-ocular tissue. Within the eye, this substance accumulates on the ocular surface and in the anterior segment of the eye, impacting ocular structures such as the conjunctiva, Tenon's capsule, sclera, cornea, iris, ciliary body, trabecular meshwork, and lens. This review aims to collate the current literature on how each anatomical part of the eye is affected by PXS, with a strong focus on molecular changes. We also summarise the current understanding of the key genetic factors influencing the development of PXS.

Ciliary muscle traction during accommodation is able to induce optic nerve head deformation

OBJECTIVES

To use finite element (FE) modeling and in vivo optical coherence tomography (OCT) imaging to explore the effect of ciliary muscle traction on optic nerve head (ONH) deformation during accommodation.

METHODS

We developed a FE model to mimic the ciliary muscle traction during accommodation, and varied the stiffness of the sclera, choroid, Bruch's membrane (BM), prelaminar neural tissue and lamina cribrosa (LC) to assess their effects on accommodation-induced ONH strains. To validate the FE model, OCT images of the right eyes' ONHs from 20 subjects (25 ± 1.5 years, range: 24-28 years) were taken for an accommodative stimulus of 6-diopters (6D) and a relaxed state of 0D. Based on OCT images, the accommodation-induced ONH effective strains, choroidal thickness and BM opening (BMO) changes were measured.

RESULTS

Our FE model predicted that the ciliary muscle pulling force could be transmitted to the ONH through the choroid and BM. The LC strain caused by the ciliary muscle pulling (0.0177) is comparable to that induced by an IOP elevation of 45 mmHg (0.0173). The accommodation-induced LC strain increased with stiffer choroid and BM. Three-dimensional strain tracking showed that the LC strains under 6D and 0D accommodation were 0.057 ± 0.033 and 0.023 ± 0.014 (p < 0.05). The reduction in choroidal thickness and the enlargement in BMO were observed during accommodation.

CONCLUSIONS

Our study showed that during accommodation, ciliary muscle traction could induce large ONH deformations and that stiffer choroid and BM increased the pulling force transmitted to the ONH, thereby leading to higher LC strains.

Horizontal Gaze Tolerance and Its Effects on Visual Sensitivity in Glaucoma

Purpose

This study evaluates the effect of 6° horizontal gaze tolerance on visual field mean sensitivity (MS) in patients with glaucoma using a binocular head-mounted automated perimeter, following findings of structural changes in the posterior globe from magnetic resonance imaging and optical coherence tomography.

Methods

In this cross-sectional study, a total of 161 eyes (85 primary open-angle glaucoma [POAG] and 76 healthy) from 117 participants were included. Logistic regression and 1:1 matched analysis assessed the propensity score for glaucoma and healthy eyes, considering age, sex, and axial length as confounders. Visual field tests were performed with the imo perimeter (CREWT Medical Systems, Inc., Tokyo, Japan) at central gaze, 6° abduction, and 6° adduction positions as fixation points. A mixed-effects model was used to compare MS under all conditions.

Results

The analysis included a total of 82 eyes, with 41 POAG and 41 healthy after matching. The mean (standard deviation) age was 68.0 (11.0) years, with a mean deviation of -9.9 (6.6) dB for POAG and -1.0 (1.9) dB for healthy eyes using Humphrey field analysis 24-2. MS did not significantly differ among central gaze (27.0 [1.8] dB), abduction (27.1 [1.9] dB), and adduction (26.9 [2.2] dB) in healthy eyes (P = 0.650). However, MS was significantly lower for adduction (17.2 [5.9] dB) compared to central gaze (18.1 [5.9] dB) and abduction (17.9 [5.9] dB) in glaucoma eyes (P = 0.001 and P = 0.022, respectively).

Conclusions

Horizontal gaze, especially in adduction, significantly reduces visual sensitivity in glaucoma, suggesting a specific vulnerability associated with eye movement. This finding highlights the importance of eye positioning in glaucoma, warranting further investigation of its clinical significance.

An Evidence-Based Narrative Review of Scleral Hypoxia Theory in Myopia: From Mechanisms to Treatments

Myopia is one of the dominant causes of visual impairment in the world. Pathological myopia could even lead to other serious eye diseases. Researchers have reached a consensus that myopia could be caused by both environmental and genetic risk factors. Exploring the pathological mechanism of myopia can provide a scientific basis for developing measures to delay the progression of myopia or even treat it. Recent advances highlight that scleral hypoxia could be an important factor in promoting myopia. In this review, we summarized the role of scleral hypoxia in the pathology of myopia and also provided interventions for myopia that target scleral hypoxia directly or indirectly. We hope this review will aid in the development of novel therapeutic strategies and drugs for myopia.

Effect of axial elongation on anterior scleral thickness in myopia

OBJECTIVE

This study aimed to investigate the effect of axial elongation on anterior scleral thickness (AST) in myopia.

METHODS

The convenience sampling method was used to select 122 patients without ocular or systemic diseases affecting ametropia in Ya'an People's Hospital between March 2020 and January 2022. According to the diopter and axial length (AL), the patients were divided into an emmetropia group (32 cases), a low-to-moderate myopia group (40 cases), and a high myopia group (40 cases). Relevant data were collected and analyzed.

RESULTS

The AST of the four diameter lines was highest at the scleral process and measured. The results, in descending order, were as follows: temporal side (716.45 ± 65.55 μm), lower side (692.32 ± 74.76 μm), nasal side (671.54 ± 61.76 μm), and superior side (550.76 ± 51.34 μm). There was a correlation between the AL and the average AST of the four diameter lines. The correlations, from highest to lowest, were as follows: the mean AST of the nasal side (r = -0.455, P < 0.001), the mean AST of the upper side (r = -0.431, P < 0.001), the mean AST of the lower side (r = -0.402, P < 0.001) and the mean AST of the temporal side (r = -0.363, P < 0.001). Age was associated with the average AST of the upper, nasal, and temporal sides. The correlations, from highest to lowest, were as follows: the average AST of the upper side (r = 0.545, P < 0.001), the average AST of the temporal side (r = 0.422, P < 0.001), and the average AST of the nasal side (r = 0.411, P < 0.001). There were significant differences in AST among the three groups at 0, 1, 2, 3, 4, 5, and 6 mm from the scleral bulge (P < 0.05). AST was positively correlated with age and negatively correlated with AL (R2= 0.432, F = 231.73, P < 0.05).

CONCLUSION

The thickness of the sclera changed with the AL and measurement position. AST was negatively correlated with the AL and positively correlated with age. Compared with emmetropia and low-to-moderate myopia, the anterior sclera in cases of high myopia was thinner. Myopia affects not only the thickness of the posterior sclera but also the AST.

The Contribution of the Limbus and Collagen Fibrils to Corneal Biomechanical Properties: Estimation of the Low-Strain In Vivo Elastic Modulus and Tissue Strain

We have compared the biomechanical properties of human and porcine corneas using vibrational optical coherence tomography (VOCT). The elastic modulus of the cornea has been previously reported in the literature to vary from about several kPa to more than several GPa based on the results of different techniques. In addition, the formation of corneal cones near the central cornea in keratoconus has been observed in the clinic. Measurements of the resonant frequency and morphology of human and porcine corneas were used to evaluate the role of the limbus in corneal stabilization, the effect of Bowman's layer, and the effect of collagen content on the low-strain corneal biomechanics. The results of these studies indicate that limbus stability plays an important anatomic role in preventing folding, corneal slippage, and cone formation. Machine learning studies of both human and porcine corneas indicate that Bowman's membrane, like that of the collagen fibrils found in the anterior corneal stroma, contributes to the 110-120 Hz resonant frequency peak. Finite element and SOLIDWORKS models of normal and keratoconus corneas suggest that the deformation of the cornea is the highest at the central zone and is higher in keratoconus corneas compared to normal controls. VOCT results suggest that although collagen fibril slippage occurs first at the limbus, cone formation in keratoconus occurs centrally/paracentrally, where stress concentration and deformation due to intraocular forces are the highest. Cone formation occurs at the points of maximum curvature. Results of these studies indicate the elastic modulus of cornea fibrillar collagen dictates the corneal elastic modulus at low strains. These results suggest that tension in the cornea at the limbus results in deformation into the low modulus region of the J-shaped stress-strain curve, resulting in an in vivo strain of less than about 10%. We propose that tension in the cornea provides a baseline force that regulates corneal epithelial regeneration as well as corneal lamellae composition and matrix turnover.

Form-deprivation myopia promotes sclera M2-type macrophages polarization in mice

PURPOSE

To explore the phenotype of sclera macrophages in form-deprivation (FD) myopia mice and the effects of M2 macrophage in FD myopia development.

METHODS

C57BL/6 mice were under 2 weeks of unilateral FD treatment. and they were separated into two groups, including an intraperitoneally injected(IP) vehicle group and Panobinostat (LBH589) (10 mg/kg per body weight) treatment group. All biometric parameters were measured before and after treatments, and the type and density of sclera macrophages were identified by immunofluorescence and RT-qPCR. In vitro, we analyzed the M2 macrophage and primary human sclera fibroblast (HSF) co-culture system by using the transcriptome sequencing method. Gene ontology (GO) and KEGG enrichment analyses were used to pinpoint the biological functions and pathways associated with the identified Differentially Expressed Genes (DEGs). The hub genes were investigated using the STRING database and Cytoscape software and were confirmed using RT-qPCR.

RESULTS

We found that the M2-type sclera macrophage density and expression increased in FD-treated eyes. The results showed that LBH589 inhibited the M2 macrophage polarization, and reduced FDM development. GO and KEGG analyses revealed that the DEGs were predominantly involved in the synthesis and breakdown of the extracellular matrix (ECM), as well as in pathways related to ECM-receptor interaction and the PI3K-Akt signaling pathway. Five hub genes (FN-1, MMP-2, COL1A1, CD44, and IL6) were identified, and RT-qPCR validated the variation in expression levels among these genes.

CONCLUSION

M2 macrophage polarization occurred in the sclera in FDM mice. Panobinostat-mediated inhibition of M2 macrophage polarization may decrease FDM progression, as M2 macrophages are crucial in controlling ECM remodeling by HSFs.

Clinical application and outcome of Tenon's patch graft: A comprehensive review

Corneal perforations are potentially sight-threatening conditions if not promptly treated. Management depends on the size, location, cause, and severity of the perforation. Various methods, including tissue adhesives, amniotic membrane grafting (AMG), and keratoplasty, are available. However, the limited availability of donor tissue in emergencies poses a significant challenge. Recently, Tenon's patch grafting (TPG) has emerged as a promising treatment option due to its autologous nature, availability, and lack of immunogenicity. This review provides a comprehensive overview of various aspects of TPG, along with relevant images. A literature search using keywords such as "Tenon's patch graft," "Tenon's capsule," "corneal patch graft," "amniotic membrane," and "corneal perforations" yielded 37 articles, included in this review. TPG is suitable for cases involving corneal tissue degradation leading to perforation, impending perforation, or descemetocele, with lesion sizes ranging from 2 to 6 mm. For larger perforations, the procedure may be modified by combining it with AMG or tissue adhesives. Postoperatively, the graft undergoes characteristic changes, including epithelialization and collagen deposition, resulting in the formation of a thick scar. Complications such as delayed epithelialization, wound leaks, and graft dehiscence can occur. High success rates have been reported, ranging from 74% to 87%. However, TPG may result in suboptimal visual outcomes, particularly when the graft is centrally located, necessitating future keratoplasty for visual rehabilitation. Overall, TPG is a safe and cost-effective technique for restoring structural integrity in corneal thinning disorders and perforations, especially in emergency settings when donor tissue is unavailable.

High correlated color temperature white light-emitting diodes disrupt refractive development in guinea pigs

Ubiquitous white light-emitting diodes (LEDs) possess optical properties that differ from those of natural light. This difference can impact visual perception and biological functions, thus potentially affecting eye health. Myopia, which leads to visual impairments and potentially irreversible vision loss or blindness, is the most prevalent refractive error worldwide. Ambient light has been found to be a significant factor in refractive development. The overlap between the commonly utilized of white LEDs and the rapid increase in the prevalence of myopia raises suspicions that white LEDs may represent hidden visual cues. To clarify the potential effects of white LEDs on refractive development, we exposed guinea pigs to different forms of artificial lighting over a period of eight weeks. We found that exposure to white LEDs with a high correlated color temperature (CCT) of approximately 5000 K can induce significant myopic shifts in guinea pigs, along with a decrease in collagen accumulation in the sclera. Additionally, this exposure was found to significantly reduce choroidal tissue thickness in guinea pigs. Our study findings indicate that high CCT white LEDs disrupt refractive development in guinea pigs. These results suggest that high CCT white LEDs might similarly affect refractive development in humans, highlighting the need for further clinical investigation.

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.

Comparing IOP-Induced Scleral Deformations in the Myopic and Myopic Glaucoma Spectrums

Purpose

To compare changes in macular curvature following acute IOP elevation across a range of myopic conditions.

Methods

We studied 328 eyes from 184 subjects, comprising 32 emmetropic controls (between +2.75 and -2.75 diopters), 50 eyes with high myopia (<-5 diopters; HM), 108 highly myopic with glaucoma (HMG) and 105 pathologic myopia (PM) eyes, and 33 PM with staphyloma (PM+S) eyes. For each eye, we imaged the macula using optical coherence tomography (OCT) under the baseline condition and under acute IOP elevation (to ∼40 mm Hg) achieved through ophthalmodynamometry. We manually aligned the scans (baseline and IOP elevation) using three vascular landmarks in the macula tissue. We then automatically segmented the sclera and the choroid tissues using a deep learning algorithm and extracted the sclera-choroid interface. We calculated the macula curvatures, determined by the radius of curvature of the sclera-choroid interface in the nasal-temporal and superior-inferior direction. Differences in macula curvatures between baseline and elevated IOP scans were calculated at corresponding locations, and the mean curvature difference was reported for each eye.

Results

IOP elevation resulted in a significantly higher macula curvature change along the nasal-temporal direction in the PM+S (13.5 ± 8.2 × 10-5 µm-1), PM (9.0 ± 7.9 × 10-5 µm-1), and HMG (5.2 ± 5.1 × 10-5 µm-1) eyes as compared to HM (3.1 ± 2.7 × 10-5 µm-1) eyes (all P < 0.05). Interestingly, HM and HMG eyes had the same curvature change in the nasal-temporal direction as emmetropic control eyes (4.2 ± 4.3 × 10-5 µm-1).

Conclusions

Our findings indicate that the macula in HMG, PM, and PM+S eyes showed greater curvature changes under IOP elevation compared to HM and emmetropic eyes. These preliminary results suggest that HM eyes with conditions such as glaucoma or staphyloma are more sensitive to acute IOP elevation.

In-vivo high-frequency quantitative ultrasound-derived parameters of the anterior sclera correlated with level of myopia and presence of staphyloma

BACKGROUND

A high-frequency point-of-care (POC) ultrasound instrument was used to evaluate the microstructural and biomechanical properties of the anterior sclera in vivo using parameters computed from quantitative ultrasound (QUS) methods.

METHODS

In this cross-sectional study, both eyes of 85 enrolled patients were scanned with the POC instrument and ultrasound data were processed to obtain QUS parameters. Pearson correlation and multi-linear regression were used to identify relationships between QUS parameters and refractive error (RE) or axial length. After categorising eyes based on RE, binary support vector machine (SVM) classifiers were trained using the QUS or ophthalmic parameters (anterior chamber depth, central corneal thickness, corneal power, and intraocular pressure) to classify each eye. Classifier performance was evaluated by computing the area under the receiver-operating characteristic curve (AUC).

RESULTS

Individual QUS parameters correlated with RE and axial length (p < 0.05). Multi-linear regression revealed significant correlation between the set of QUS parameters and both RE (R = 0.49, p < 0.001) and axial length (R = 0.46, p = 0.001). Classifiers trained with QUS parameters achieved higher AUC (𝑝 = 0.06) for identifying myopic eyes (AUC = 0.71) compared to classifiers trained with ophthalmic parameters (AUC = 0.63). QUS-based classifiers attained the highest AUC when identifying highly myopic eyes (AUC = 0.77).

CONCLUSIONS

QUS parameters correlate with progressing myopia and may be indicative of myopia-induced microstructural and biomechanical changes in the anterior sclera. These methods may provide critical clinical information complementary to standard ophthalmic measurements for predicting myopia progression and risk assessment for posterior staphyloma formation.

Anterior scleral thickness in Marfan syndrome: A quantitative analysis

PURPOSE

To investigate the anterior scleral thickness (AST) in patients with Marfan syndrome (MFS).

METHODS

A prospective, cross-sectional study was conducted at the Department of Ophthalmology, Ghent University Hospital, Ghent, including patients with a genetically confirmed clinical diagnosis of MFS and age-, gender- and axial length-matched controls. Subjects with known corneal, conjunctival or scleral pathology and a history of ocular surgery, including pars plana vitrectomy, recent contact lens use or high-grade astigmatism were excluded. Subjects underwent non-cycloplegic autorefraction, Scheimpflug-based corneal tomography, axial length measurement and spectral-domain optical coherence tomography (OCT). AST was manually measured at 1 mm (AST1), 2 mm (AST2) and 3 mm (AST3) from the scleral spur, temporally and nasally.

RESULTS

A total of 56 subjects (28 subjects in the MFS group and 28 matched subjects in the control group) were included in this study. In patients with MFS, AST was significantly reduced compared to matched controls, both overall and at every analysed measuring point in the nasal and temporal areas (p < 0.001). Central corneal thickness (CCT) and mean keratometry (Kmean) values were significantly lower in patients with MFS (p < 0.05). A positive correlation was found between nasal AST and CCT in patients with MFS. No correlation was found between AST and Kmean or between AST and axial length. In patients with MFS with ectopia lentis, compared to those without, temporal AST3 was significantly lower (p < 0.05). AST was significantly lower in patients with MFS harbouring a variant predicted to cause haploinsufficiency compared to those with a variant expected to lead to a dominant negative effect for both nasal and temporal measurements.

CONCLUSION

Based on anterior segment OCT measurements, AST of patients with MFS is significantly lower compared to matched controls.

Relationship between corneal hysteresis and the site of damage to peripapillary retinal nerve fibre layer thickness in open-angle glaucoma

Corneal hysteresis (CH) is associated with glaucomatous structural changes. We retrospectively investigated the association between CH and the regional circumpapillary retinal nerve fibre layer thickness (cpRNFLT) in 419 eyes of 419 patients with normal-tension glaucoma (NTG) and primary open-angle glaucoma (POAG). CH was used as the explanatory variable, and cpRNFLT (total and quadrant) was used as the dependent variable. Standardized β coefficients were compared both overall and between the NTG and POAG groups. Multiple regression analysis with CH as the explanatory variable and cpRNFLT parameters as the dependent variables suggested that even after adjusting for age, sex, intraocular pressure (IOP), axial length, and central corneal thickness, all areas of the cpRNFLT were significantly associated with CH, except for the nasal quadrant. In the stratified analysis by glaucoma type, a positive relationship between CH and regional cpRNFLT tended to be maintained in the NTG group but not in the POAG group (P = 0.060 for interaction). Additionally, in the NTG group, the CH-inferior cpRNFLT relationship was particularly strong in the less-IOP fluctuation group. These results suggest that CH may be a potential predictor of anatomical vulnerability around the optic nerve, particularly enhancing the inferior regions of NTG.

Assessment of the Corneal Biomechanical Features of Sturge-Weber Syndrome Using Dynamic Ultrahigh-speed Scheimpflug Imaging

PURPOSE

To evaluate the corneal biomechanical characteristics of eyes with Sturge-Weber syndrome (SWS) secondary glaucoma (SSG) by analyzing corneal biomechanical parameters obtained using the Corneal Visualization Scheimpflug Technology instrument (Corvis ST).

METHODS

In patients with SWS, eyes affected by SSG were designated as the SSG group while the contralateral eyes were designated as the SWS contralateral group (SC group). Patients from the myopia clinic served as the control group. Dynamic corneal response parameters (DCRs) including the stress-strain index (SSI)-a critical material stiffness parameter that excludes interference from IOP and central corneal thickness (CCT)-were analyzed.

RESULTS

For CCT, no significant difference was observed between the SSG and SC groups. However, significant differences were found between the SSG and control groups and between the SC and control groups. Parameters such as HC Time, A1 Deformation Amp., A2 Deformation Amp., length of Whole Eye Movement (WEM), DA Ratio Max (2 mm), PachySlope, DA Ratio Max (1 mm), and ARTh showed significant differences between the SSG group and control group. In the SSG group, 4 of night eyes had an SSI of less than 0.85.

CONCLUSIONS

Some DCRs indicated a stiffer cornea in the SSG group, possibly due to a thicker cornea in this group. On analyzing SSI, it was found that corneal material properties change, becoming less stiff in some of the patients with SSG. In conclusion, our study provides a preliminary exploration of the biomechanical properties of SWS secondary glaucoma.

Revolutionizing Eye Care: Exploring the Potential of Microneedle Drug Delivery

Microneedle technology revolutionizes ocular drug delivery by addressing challenges in treating ocular diseases. This review explores its potential impact, recent advancements, and clinical uses. This minimally invasive technique offers precise control of drug delivery to the eye, with various microneedle types showing the potential to penetrate barriers in the cornea and sclera, ensuring effective drug delivery. Recent advancements have improved safety and efficacy, offering sustained and controlled drug delivery for conditions like age-related macular degeneration and glaucoma. While promising, challenges such as regulatory barriers and long-term biocompatibility persist. Overcoming these through interdisciplinary research is crucial. Ultimately, microneedle drug delivery presents a revolutionary method with the potential to significantly enhance ocular disease treatment, marking a new era in eye care.

Influence of scleral thickness on photodynamic therapy outcomes in central serous chorioretinopathy

PURPOSE

To test the prognostic role of anterior scleral substantia propria (ASSP) thickness in predicting the 3-month response after half-dose photodynamic therapy (PDT) in central serous chorioretinopathy (CSCR) and to assess its clinical relevance of ASSP in different CSCR phenotypes.

METHODS

A prospective, exploratory, multi-centre cohort study conducted at IRCCS San Martino Hospital (Genoa, Italy) and Jules-Gonin Eye Hospital (Lausanne, Switzerland). Demographic and clinical data, and optical coherence tomography (OCT) were collected at baseline and 3 months after PDT. Based on OCT images, we categorized CSCR phenotypes and collected clinically relevant imaging metrics. ASSP thickness was obtained from four different measurements using anterior segment (AS) OCT. Multivariable regression models were performed to evaluate the distribution of ASSP thicknesses among different CSCR phenotypes and to test the prognostic role of ASSP thickness in discriminating between PDT responders (complete subretinal fluid reabsorption) and partial responders.

RESULTS

The study cohort comprised 109 Caucasian patients (82 males, 75.2%) with a total of 142 eyes: 84 eyes simple (59.1%) versus 58 eyes complex (40.9%) CSCR. A linear normal model confirmed a positive association between complex CSCR and higher ASSP thickness (β = 26.1, 95% CL = 12.1/40.1, p < 0.001), with a low prevalence of ciliochoroidal effusion loculations in AS-OCT (1/142 eyes, 0.7%). ASSP thickening was positively linked to the presence of posterior cystoid retinal degeneration (PCRD; p = 0.002), indicating a potential role in the pathogenesis of severe CSCR phenotypes. In the subgroup of treated patients (61 eyes), 63.9% had a complete response after PDT. In these patients a logistic binary model highlighted a significantly higher risk of PDT non-responsiveness (OR = 9.62, 95% CL = 2.44/37.9, p = 0.001) associated with a 60-unit increase in ASSP thickness levels. By contrast, other anatomical parameters (i.e., body surface area, age, gender, axial length) showed no remarkable prognostic roles.

CONCLUSION

This research highlighted the association of ASSP thickening with complex CSCR phenotype in Caucasian patients and its role in predicting PDT efficacy. These findings enhance our comprehension of the anatomical risk factors in patients affected with CSCR and potentially guide a better understanding of non-responsive cases to PDT treatment.

Molecular mechanism of hypoxia and alpha-ketoglutaric acid on collagen expression in scleral fibroblasts

AIM

To investigate the molecular mechanisms underlying the influence of hypoxia and alpha-ketoglutaric acid (α-KG) on scleral collagen expression.

METHODS

Meta-analysis and clinical statistics were used to prove the changes in choroidal thickness (ChT) during myopia. The establishment of a hypoxic myopia model (HYP) for rabbit scleral fibroblasts through hypoxic culture and the effects of hypoxia and α-KG on collagen expression were demonstrated by Sirius red staining. Transcriptome analysis was used to verify the genes and pathways that hypoxia and α-KG affect collagen expression. Finally, real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) was used for reverse verification.

RESULTS

Meta-analysis results aligned with clinical statistics, revealing a thinning of ChT, leading to scleral hypoxia. Sirius red staining indicated lower collagen expression in the HYP group and higher collagen expression in the HYP+α-KG group, showed that hypoxia reduced collagen expression in scleral fibroblasts, while α-KG can elevated collagen expression under HYP conditions. Transcriptome analysis unveiled the related genes and signaling pathways of hypoxia and α-KG affect scleral collagen expression and the results were verified by RT-qPCR.

CONCLUSION

The potential molecular mechanisms through which hypoxia and α-KG influencing myopia is unraveled and three novel genes TLCD4, TBC1D4, and EPHX3 are identified. These findings provide a new perspective on the prevention and treatment of myopia via regulating collagen expression.

Comparing continuum and direct fiber models of soft tissues: An ocular biomechanics example reveals that continuum models may artificially disrupt the strains at both the tissue and fiber levels

Collagen fibers are the main load-bearing component of soft tissues but difficult to incorporate into models. Whilst simplified homogenization models suffice for some applications, a thorough mechanistic understanding requires accurate prediction of fiber behavior, including both detailed fiber-level strains and long-distance transmission. Our goal was to compare the performance of a continuum model of the optic nerve head (ONH) built using conventional techniques with a fiber model we recently introduced which explicitly incorporates the complex 3D organization and interaction of collagen fiber bundles [1]. To ensure a fair comparison, we constructed the continuum model with identical geometrical, structural, and boundary specifications as for the fiber model. We found that: 1) although both models accurately matched the intraocular pressure (IOP)-induced globally averaged displacement responses observed in experiments, they diverged significantly in their ability to replicate specific 3D tissue-level strain patterns. Notably, the fiber model faithfully replicated the experimentally observed depth-dependent variability of radial strain, the ring-like pattern of meridional strain, and the radial pattern of circumferential strain, whereas the continuum model failed to do so; 2) the continuum model disrupted the strain transmission along each fiber, a feature captured well by the fiber model. These results demonstrate limitations of the conventional continuum models that rely on homogenization and affine deformation assumptions, which render them incapable of capturing some complex tissue-level and fiber-level deformations. Our results show that the strengths of explicit fiber modeling help capture intricate ONH biomechanics. They potentially also help modeling other fibrous tissues. STATEMENT OF SIGNIFICANCE: Understanding the mechanics of fibrous tissues is crucial for advancing knowledge of various diseases. This study uses the ONH as a test case to compare conventional continuum models with fiber models that explicitly account for the complex fiber structure. We found that the fiber model captured better the biomechanical behaviors at both the tissue level and the fiber level. The insights gained from this study demonstrate the significant potential of fiber models to advance our understanding of not only glaucoma pathophysiology but also other conditions involving fibrous soft tissues. This can contribute to the development of therapeutic strategies across a wide range of applications.

Relationship between Choroidal Thickness and Anterior Scleral Thickness in Patients with Keratoconus

PURPOSE

To evaluate the relationship between choroidal thickness (CT) and anterior scleral thickness (AST) in patients with subclinical keratoconus (SKC) and established keratoconus (KC).

METHODS

This single-center prospective case-control study included 97 eyes of 97 patients: 44 KC eyes, 14 SKC eyes, and 39 age- and axial length (AL)-matched healthy eyes. Using swept-source optical coherence tomography, the AST was manually measured in four directions and the CT was obtained automatically from the Early Treatment Diabetic Retinopathy Study (ETDRS) grid. Principal component analysis (PCA) was used to linearly reduce the dimensionality of nine CT inputs to one significant component, CT1. A multivariate model was created to evaluate the association between CT1, AST, and several ocular parameters in SKC and KC patients. Partial correlation was then performed to adjust the confounding factors and to examine the effect of AST on CT1.

RESULTS

The PCA showed that CT1 accounts for 86.54% of the total variance in the nine original CTs of the ETDRS grid. The CT1 model was associated with age, AL, and AST in the superior meridian in SKC eyes, whereas in KC eyes, it was correlated with gender, age, AL, and AST in the inferior meridian (p < 0.001). The partial correlation between CT1 and AST in the superior zone was found to be significant, positive, and strong in SKC eyes (r = 0.79, p = 0.019), whereas a significant, positive, and moderate correlation between CT1 and AST at the inferior zone (r = 0.41, p = 0.017) was observed in KC eyes.

CONCLUSIONS

Choroidal tissue was significantly correlated with the anterior sclera across the vertical meridian. This relationship was observed over the superior sclera in SKC eyes, whereas in established KC, it was over the inferior sclera. These results reveal new insights regarding the interactions between the anterior and posterior structures of the KC eyes and confirm the enigma of the pathophysiology of KC.

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.

Biomechanical changes occur in myopic choroidal stroma and mirror those in the adjacent sclera

Retina-derived growth signals relayed from the choroid to the sclera cause remodeling of the extracellular scleral matrix, resulting in myopic ocular elongation. However, to the best of our knowledge, no studies have assessed changes in choroidal stromal biomechanical properties during myopia progression. Here we utilized 7 µm-resolution scanning acoustic microscopy (SAM) to assess biomechanical properties (bulk modulus (K) and mass density (rho)) of choroidal stroma from guinea pig eyes with form-deprivation (FD) induced myopia. The choroidal stroma had considerable intrinsic strength arising from its biomechanical properties and these were differentially affected by myopia in central and peripheral regions. Choroidal stromal biomechanical values were also highly correlated with those in adjacent scleral regions, and the choroidal stromal-scleral association was stronger in myopic eyes. Biomechanical changes observed in the choroidal stroma of myopic eyes were mirrored to those observed in the adjacent sclera. These findings suggest that choroidal stromal remodeling may accompany myopia and open the door to the source of the signals that cause scleral remodeling in myopia.

Effects of Genipin Crosslinking of Porcine Perilimbal Sclera on Mechanical Properties and Intraocular Pressure

The mechanical properties of sclera play an important role in ocular functions, protection, and disease. Modulating the sclera's properties by exogenous crosslinking offers a way to expand the tissue's range of properties for study of the possible influences on the eye's behavior and diseases such as glaucoma and myopia. The focus of this work was to evaluate the effects of genipin crosslinking targeting the porcine perilimbal sclera (PLS) since the stiffness of this tissue was previously found in a number of studies to influence the eye's intraocular pressure (IOP). The work includes experiments on tensile test specimens and whole globes. The specimen tests showed decreased strain-rate dependence and increased relaxation stress due to the cross-linker. Whole globe perfusion experiments demonstrated that eyes treated with genipin in the perilimbal region had increased IOPs compared to the control globes. Migration of the cross-linker from the target tissue to other tissues is a confounding factor in whole globe, biomechanical measurements, with crosslinking. A novel quantitative genipin assay of the trabecular meshwork (TM) was developed to exclude globes where the TM was inadvertently crosslinked. The perfusion study, therefore, suggests that elevated stiffness of the PLS can significantly increase IOP apart from effects of the TM in the porcine eye. These results demonstrate the importance of PLS biomechanics in aqueous outflow regulation and support additional investigations into the distal outflow pathways as a key source of outflow resistance.

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.

Influence of Contact Lens Parameters on Cornea: Biomechanical Analysis

This study presents a finite element analysis to model ocular biomechanics and the interactions between the human eye and contact lenses in the closed-eye condition. The closed-eye state, where the eyelids are fully shut, presents challenges for experimental measurements due to the invasive nature of accessing and analysing the contact lens and corneal interface, making simulation tools valuable for accurate characterisation. The primary objective of this study was to examine how CLs fold and twist and their impact on the cornea when the eye is closed. The secondary aim of this study was to assess how crucial contact lens parameters (Young's modulus, base curve, and diameter) influence corneal stress distribution and the overall fit of the lens on the eye. The findings show that increasing Young's modulus significantly reduces corneal stress and promotes uniform stress distribution, making it the most influential factor for wearer comfort and safety. While base curve and diameter variations primarily affect contact area, their impact on stress distribution is minimal. This research provides insights for improving contact lens design and enhancing safety for contact lens wearers.

Comparing continuum and direct fiber models of soft tissues. An ocular biomechanics example reveals that continuum models may artificially disrupt the strains at both the tissue and fiber levels

Collagen fibers are the main load-bearing component of soft tissues but difficult to incorporate into models. Whilst simplified homogenization models suffice for some applications, a thorough mechanistic understanding requires accurate prediction of fiber behavior, including both detailed fiber-level strains and long-distance transmission. Our goal was to compare the performance of a continuum model of the optic nerve head (ONH) built using conventional techniques with a fiber model we recently introduced which explicitly incorporates the complex 3D organization and interaction of collagen fiber bundles [1]. To ensure a fair comparison, we constructed the continuum model with identical geometrical, structural, and boundary specifications as for the fiber model. We found that: 1) although both models accurately matched the intraocular pressure (IOP)-induced globally averaged displacement responses observed in experiments, they diverged significantly in their ability to replicate specific 3D tissue-level strain patterns. Notably, the fiber model faithfully replicated the experimentally observed depth-dependent variability of radial strain, the ring-like pattern of meridional strain, and the radial pattern of circumferential strain, whereas the continuum model failed to do so; 2) the continuum model disrupted the strain transmission along each fiber, a feature captured well by the fiber model. These results demonstrate limitations of the conventional continuum models that rely on homogenization and affine deformation assumptions, which render them incapable of capturing some complex tissue-level and fiber-level deformations. Our results show that the strengths of explicit fiber modeling help capture intricate ONH biomechanics. They potentially also help modeling other fibrous tissues.

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.

Identification of LRRC46 as a novel candidate gene for high myopia

High myopia (HM) is the primary cause of blindness, with the microstructural organization and composition of collagenous fibers in the cornea and sclera playing a crucial role in the biomechanical behavior of these tissues. In a previously reported myopic linkage region, MYP5 (17q21-22), a potential candidate gene, LRRC46 (c.C235T, p.Q79X), was identified in a large Han Chinese pedigree. LRRC46 is expressed in various eye tissues in humans and mice, including the retina, cornea, and sclera. In subsequent cell experiments, the mutation (c.C235T) decreased the expression of LRRC46 protein in human corneal epithelial cells (HCE-T). Further investigation revealed that Lrrc46-/- mice (KO) exhibited a classical myopia phenotype. The thickness of the cornea and sclera in KO mice became thinner and more pronounced with age, the activity of limbal stem cells decreased, and microstructural changes were observed in the fibroblasts of the sclera and cornea. We performed RNA-seq on scleral and corneal tissues of KO and normal control wild-type (WT) mice, which indicated a significant downregulation of the collagen synthesis-related pathway (extracellular matrix, ECM) in KO mice. Subsequent in vitro studies further indicated that LRRC46, a member of the important LRR protein family, primarily affected the formation of collagens. This study suggested that LRRC46 is a novel candidate gene for HM, influencing collagen protein VIII (Col8a1) formation in the eye and gradually altering the biomechanical structure of the cornea and sclera, thereby promoting the occurrence and development of HM.

Contact lens fitting and changes in the tear film dynamics: mathematical and computational models review

PURPOSE

This review explores mathematical models, blinking characterization, and non-invasive techniques to enhance understanding and refine clinical interventions for ocular conditions, particularly for contact lens wear.

METHODS

The review evaluates mathematical models in tear film dynamics and their limitations, discusses contact lens wear models, and highlights computational mechanical models. It also explores computational techniques, customization of models based on individual blinking dynamics, and non-invasive diagnostic tools like high-speed cameras and advanced imaging technologies.

RESULTS

Mathematical models provide insights into tear film dynamics but face challenges due to simplifications. Contact lens wear models reveal complex ocular physiology and design aspects, aiding in lens development. Computational mechanical models explore eye biomechanics, often integrating tear film dynamics into a Multiphysics framework. While different computational techniques have their advantages and disadvantages, non-invasive tools like OCT and thermal imaging play a crucial role in customizing these Multiphysics models, particularly for contact lens wearers.

CONCLUSION

Recent advancements in mathematical modeling and non-invasive tools have revolutionized ocular health research, enabling personalized approaches. The review underscores the importance of interdisciplinary exploration in the Multiphysics approach involving tear film dynamics and biomechanics for contact lens wearers, promoting advancements in eye care and broader ocular health research.

Construction of glaucoma model and comparing eyeball enlargement with myopia in Guinea pig

This study aimed to develop and evaluate a guinea pig model for glaucoma, comparing resultant eyeball enlargement with an existing myopia model. Thirty guinea pigs underwent intracameral injection of magnetic microspheres to induce chronic ocular hypertension (COH). Intraocular pressure (IOP) was systematically monitored, revealing a successful induction of COH in 73.33% of the guinea pigs. The mean IOP increased from a baseline of 18.04 ± 1.33 mmHg, reaching a peak at week 3 (36.31 ± 6.13 mmHg) and remaining elevated for at least 7 weeks. All data are presented as mean ± standard deviation of the mean. Subsequently, detailed assessments were conducted to validate the established glaucoma model. Immunofluorescent staining demonstrated a significant decrease in the density of retinal ganglion cells (RGC) in the glaucoma group. Optic disc excavation and notable thinning of the lamina cribrosa (LC) were observed. The quantity of optic nerve ax·ons in glaucoma group gradually decreased from baseline (44553 ± 3608/mm2) to week 4 (28687 ± 2071/mm2) and week 8 (17977 ± 3697/mm2). Moreover, regarding the global enlargement of eyeballs, both the transverse and longitudinal axis in glaucomatous eyes were found to be significantly larger than that in myopic eyes, particularly in the anterior chamber depth (1.758 ± 0.113 mm vs. 1.151 ± 0.046 mm). These findings indicate distinct patterns of structural changes associated with glaucoma and myopia in the guinea pig model. This guinea pig model holds promise for future research aimed at exploring biomechanical mechanisms, therapeutic interventions, and advancing our understanding of the relationship between glaucoma and myopia.

Differential Functional Changes in Visual Performance during Acute Exposure to Microgravity Analogue and Their Potential Links with Spaceflight-Associated Neuro-Ocular Syndrome

BACKGROUND

Spaceflight-Associated Neuro-Ocular Syndrome (SANS) is a complex pathology threatening the health of astronauts, with incompletely understood causes and no current specific functional diagnostic or screening test. We investigated the use of the differential performance of the visual system (central vs. perimacular visual function) as a candidate marker of SANS-related pathology in a ground-based microgravity analogue.

METHODS

We used a simple reaction time (SRT) task to visual stimuli, presented in the central and perimacular field of view, as a measure of the overall performance of the visual function, during acute settings (first 10 min) of vertical, bed rest (BR), -6°, and -15° head-down tilt (HDT) presentations in healthy participants (n = 8). We built dose-response models linking the gravitational component to SRT distribution parameters in the central vs. perimacular areas.

RESULTS

Acute exposure to microgravity induces detectable changes between SRT distributions in the perimacular vs. central retina (increased mean, standard deviation, and tau component of the ex-Gaussian function) in HDT compared with vertical presentation.

CONCLUSIONS

Functional testing of the perimacular retina might be beneficial for the earlier detection of SANS-related ailments in addition to regular testing of the central vision. Future diagnostic tests should consider the investigation of the extra-macular areas, particularly towards the optic disc.

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.

Age-related alterations in vortex veins on indocyanine green angiography

To determine age-related alterations in vortex veins in healthy subjects. A total of 228 healthy subjects (aged 4 to 86 years) were recruited and divided into four groups (G1, <21 years; G2, 21-40 years; G3, 41-60 years; and G4, 61-86 years). The clinical characteristics of the participants were recorded, and parameters including the number of vortex vein roots (NVVR), the central vortex vein diameter (CVVD), the mean root area of the vortex vein (MRAVV), and the weighted mean of the thickest branch diameter (WMTBD) were obtained by marking the vortex veins on indocyanine green angiography (ICGA). The NVVR in the age group over 60 years old was significantly lower than that in other age groups (P < 0.05). The CVVD, MRAVV, and WMTBD of all age groups increased with increasing age (P < 0.05). The NVVR was unevenly distributed among the quadrants (P < 0.001). The proportions of type four vortex veins (complete systems including ampulla) and anastomotic branches of the vortex veins were significantly increased in elderly participants over 50 years of age (P < 0.05). Subfoveal choroidal thickness was significantly correlated with age, NVVR, CVVD and MRAVV (P < 0.05). This is the first study to reveal age-related alterations in vortex veins on ICGA in a healthy population. Aging may lead to partial vortex occlusion and residual vortex dilation. As age increases, anastomotic branches increasingly appear between the originally independent vortex veins. Translational relevance: Aging may lead to partial vortex occlusion and residual vortex dilation.

Surgical Outcomes, Ocular Safety and Tolerability of Bio-Interventional Cyclodialysis with Allograft Scleral Reinforcement: Clinical Experience of More than 240 Cases

Background: To report the surgical safety of reinforced bio-interventional cyclodialysis with scleral allograft reinforcement. Methods: This was a consecutive case series of 243 eyes with open-angle glaucoma who underwent a bio-scaffolded cyclodialysis (BSC) procedure for uveoscleral outflow enhancement using allogeneic bio-spacers to maintain patency of the internal filtration conduit. Results: 79% of the eyes underwent concomitant phacoemulsification cataract surgery prior to BSC intervention, while the remaining eyes underwent stand-alone BSC surgery. All patients had a postoperative surgical safety period of at least 30 days. There were no sight-threatening or serious ocular adverse events. There was one case of prolonged iritis beyond 30 days, which resolved with topical treatment. Two cases (0.8%) of intraoperative and five (2%) of postoperative non-sight-threatening hyphema were without clinical sequelae, which resolved with conservative management. There were 11 cases of IOP elevation and one case of numeric hypotony without maculopathy, which resolved within the study period. The rate of secondary surgical intervention for IOP control was low, and overall, IOP for the cohort improved in the postoperative period, with 78.6% of eyes achieving IOP ≤ 18 mmHg without an increase in medications. Conclusions: Allogeneic biotissue for cyclodialysis intervention demonstrates a biocompatible ocular profile as an implantable material for internal scleral reinforcement during uveoscleral outflow enhancement surgery.

Optic Nerve Head Morphology and Macula Ganglion Cell Inner Plexiform Layer Thickness in Axially Anisometropic Rhesus Monkeys

Purpose

The purpose of this study was to determine the effects of axial elongation on optic nerve head morphology and macula inner retinal thickness in young rhesus monkeys.

Methods

Both eyes of 26 anisometropic, 1-year-old rhesus monkeys were imaged using optical coherence tomography (OCT). Before imaging, the animals were sedated, their eyes were dilated, and axial length was measured using an optical biometer. OCT imaging included a 20 degrees, 24-line radial scan centered on the optic nerve head (ONH) and two 20 degrees × 20 degrees raster scans, one centered on the ONH and the other on the macula. Radial scans were analyzed using programs written in MATLAB to quantify the Bruch's membrane opening (BMO) area and position, minimum rim width (MRW), anterior lamina cribrosa surface (ALCS) position, size of any scleral crescent, circumpapillary retinal nerve fiber layer (RNFL), and choroid thickness (pCh). Macula total retinal thickness (mTRT) and ganglion cell inner plexiform layer (GCIPL) thicknesses were quantified from macula scans. Linear least square regression was determined for OCT measures and axial length of the right eye, and for inter-eye differences.

Results

Animals were 341 ± 18 days old at the time of imaging. BMO area (R2 = 0.38), ALCS position (R2 = 0.45), scleral crescent area (R2 = 0.35), pCh thickness (R2 = 0.21), mTRT (R2 = 0.24), and GCIPL thickness (R2 = 0.16) were correlated with the axial length (all P < 0.05). For each of these parameters, the right-eye regression slope did not differ from the slope of the interocular difference (P > 0.57).

Conclusions

There are posterior segment morphological differences in anisometropic rhesus monkeys related to axial length. Whether these differences increase the risk of pathology remains to be investigated.

Assessment of conjunctival, episcleral and scleral thickness in healthy individuals using anterior segment optical coherence tomography

PURPOSE

To determine the thickness of the conjunctiva, episclera and sclera in healthy individuals using anterior segment optical coherence tomography (AS-OCT).

METHODS

We prospectively included 107 healthy individuals of different age groups (18-39 years, 40-54 years, 55-69 years and ≥70 years). For each eye, AS-OCT scans of four quadrants (temporal, nasal, superior and inferior) were acquired. The thickness of the conjunctiva, episclera and sclera was measured for each scan. In addition, the axial length of both eyes was measured, and general characteristics, including smoking, allergies and contact lens use, were collected.

RESULTS

The mean conjunctival thickness was significantly different between the nasal and superior quadrants (87 ± 30 μm vs. 77 ± 16 μm; p < 0.001), as well as the superior and inferior quadrants (77 ± 16 μm vs. 86 ± 19 μm; p = 0.001). The mean episcleral thickness was larger in the superior (174 ± 54 μm) and inferior (141 ± 43 μm) quadrants, compared to the nasal (83 ± 38 μm) and temporal quadrants (90 ± 44 μm). The mean scleral thickness of the inferior quadrant was the largest (596 ± 64 μm), followed by the nasal (567 ± 76 μm), temporal (516 ± 67 μm) and superior (467 ± 52 μm) quadrants (all p < 0.001). The averaged scleral thickness increased 0.96 μm per age year (0.41-1.47 μm, p < 0.001).

CONCLUSIONS

This study provides an assessment of the thickness of scleral and adjacent superficial layers in healthy individuals determined on AS-OCT, which could enable future research into the use of AS-OCT in diseases affecting the anterior eye wall.

Innovative Nanotechnology in Drug Delivery Systems for Advanced Treatment of Posterior Segment Ocular Diseases

Funduscopic diseases, including diabetic retinopathy (DR) and age-related macular degeneration (AMD), significantly impact global visual health, leading to impaired vision and irreversible blindness. Delivering drugs to the posterior segment of the eye remains a challenge due to the presence of multiple physiological and anatomical barriers. Conventional drug delivery methods often prove ineffective and may cause side effects. Nanomaterials, characterized by their small size, large surface area, tunable properties, and biocompatibility, enhance the permeability, stability, and targeting of drugs. Ocular nanomaterials encompass a wide range, including lipid nanomaterials, polymer nanomaterials, metal nanomaterials, carbon nanomaterials, quantum dot nanomaterials, and so on. These innovative materials, often combined with hydrogels and exosomes, are engineered to address multiple mechanisms, including macrophage polarization, reactive oxygen species (ROS) scavenging, and anti-vascular endothelial growth factor (VEGF). Compared to conventional modalities, nanomedicines achieve regulated and sustained delivery, reduced administration frequency, prolonged drug action, and minimized side effects. This study delves into the obstacles encountered in drug delivery to the posterior segment and highlights the progress facilitated by nanomedicine. Prospectively, these findings pave the way for next-generation ocular drug delivery systems and deeper clinical research, aiming to refine treatments, alleviate the burden on patients, and ultimately improve visual health globally.

Phacoemulsification in Nanophthalmic Eye, a Way to Manage Glaucoma: Case Report

A rare condition called nanophthalmos causes variable degrees of vision impairment. One may present with nanophthalmos as a hereditary or sporadic condition. There have been documented cases of nanophthalmos treated with bilateral cataract extraction and intraocular lens (IOL) implantation for intractable secondary glaucoma or chronic angle-closure glaucoma. We describe a case of closed-angle glaucoma in a nanophthalmic eye with increased intraocular pressure (IOP) on full medical treatment, along with concurrent drug side effects. As a first surgical procedure, we recommend phacoemulsification of the clear lens + IOL. The challenge in treating nanophthalmic eyes lies in managing the possibility of developing glaucoma in an eye where anatomical conditions make surgery extremely risky. This must be balanced against the advantages of lessening exposure contact in the trabecular meshwork and optimizing the anterior chamber for potential future glaucoma surgery, which can improve the prognosis in these cases. Lastly, it is critical to have a thorough conversation with the patient about the aims, risks, and advantages. The patient's understanding and expectations should also be crystal apparent. The primary objective should always be to enhance the circumstances for the most effective glaucoma therapy, not to perform refractive surgery.

A Noninvasive Clinical Method to Measure in Vivo Mechanical Strains of the Lamina Cribrosa by OCT

Objective

To measure mechanical strain of the lamina cribrosa (LC) after intraocular pressure (IOP) change produced 1 week after a change in glaucoma medication.

Design

Cohort study.

Participants

Adult glaucoma patients (23 eyes, 15 patients) prescribed a change in IOP-lowering medication.

Intervention

Noninvasive OCT imaging of the eye.

Main Outcome Measures

Deformation calculated by digital volume correlation of OCT scans of the LC before and after IOP lowering by medication.

Results

Among 23 eyes, 17 eyes of 12 persons had IOP lowering ≥ 3 mmHg (reduced IOP group) with tensile anterior-posterior Ezz strain = 1.0% ± 1.1% (P = 0.003) and compressive radial strain (Err) = -0.3% ± 0.5% (P = 0.012; random effects models accounting inclusion of both eyes in some persons). Maximum in-plane principal (tensile) strain and maximum shear strain in the reduced-IOP group were as follows: Emax = 1.7% ± 1.0% and Γmax = 1.4% ± 0.7%, respectively (both P < 0.0001 vs. zero). Reduced-IOP group strains Emax and Γmax were significantly larger with greater % IOP decrease (P < 0.0001 and P < 0.0001, respectively). The compliances of the Ezz, Emax, and Γmax strain responses, defined as strain normalized by the IOP decrease, were larger with more abnormal perimetric mean deviation or visual field index values (all P ≤ 0.02). Strains were unrelated to age (all P ≥ 0.088). In reduced-IOP eyes, mean LC anterior border posterior movement was only 2.05 μm posteriorly (P = 0.052) and not related to % IOP change (P = 0.94, random effects models). Only Err was significantly related to anterior lamina depth change, becoming more negative with greater posterior LC border change (P = 0.015).

Conclusions

Lamina cribrosa mechanical strains can be effectively measured by changes in eye drop medication using OCT and are related to degree of visual function loss in glaucoma.

Financial Disclosures

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

The Evolving Surgical Paradigm of Scleral Allograft Bio-Tissue Use in Ophthalmic Surgery: Techniques and Clinical Indications for Ab-Externo and Ab-Interno Scleral Reinforcement

To review the latest surgical advances and evolving clinical use of scleral bio-tissue for reinforcement in the eye and review the published literature on novel surgical applications of scleral allograft bio-tissue. Conventional surgical procedures for scleral reinforcement using homologous scleral allograft have been traditionally ab-externo interventions comprising of anterior or posterior reinforcement of the sclera for clinical indications such as trauma, scleromalacia, glaucoma drainage device coverage, scleral perforation, buckle repair as well as posterior reinforcement for pathologic myopia and staphyloma. There have been a few novel ab-interno uses of scleral bio-tissue for reinforcement in both retina and glaucoma. Over the last decade, there has been an increase in peer-reviewed publications on scleral reinforcement, reflecting more interest in its clinical applications. With favorable biological and biomechanical properties, scleral allograft may be an ideal substrate for an array of new applications and surgical uses.

Optimization of stereolithography 3D printing of microneedle micro-molds for ocular drug delivery

Microneedles (MN) have emerged as an innovative technology for drug delivery, offering a minimally invasive approach to administer therapeutic agents. Recent applications have included ocular drug delivery, requiring the manufacture of sub-millimeter needle arrays in a reproducible and reliable manner. The development of 3D printing technologies has facilitated the fabrication of MN via mold production, although there is a paucity of information available regarding how the printing parameters may influence crucial issues such as sharpness and penetration efficacy. In this study, we have developed and optimized a 3D-printed MN micro-mold using stereolithography (SLA) 3D printing to prepare a dissolving ocular MN patch. The effects of a range of parameters including aspect ratio, layer thickness, length, mold shape and printing orientation have been examined with regard to both architecture and printing accuracy of the MN micro-mold, while the effects of printing angle on needle fidelity was also examined for a range of basic shapes (conical, pyramidal and triangular pyramidal). Mechanical strength and in vitro penetration of the polymeric (PVP/PVA) MN patch produced from reverse molds fabricated using MN with a range of shapes and height, and aspect ratios were assessed, followed by ex vivo studies of penetration into excised scleral and corneal tissues. The optimization process identified the parameters required to produce MN with the sharpest tips and highest dimensional fidelity, while the ex vivo studies indicated that these optimized systems would penetrate the ocular tissue with minimal applied pressure, thereby allowing ease of patient self-administration.

Orthokeratology effect on the corneoscleral profile: Beyond the bull's eye

PURPOSE

To assess the impact of 3 months of orthokeratology (ortho-k) contact lenses (CLs) for myopia correction on the corneoscleral profile, as changes in scleral geometry could serve as indirect evidence of alteration in the corneal biomechanical properties.

METHODS

Twenty subjects (40 eyes) were recruited to wear ortho-k lenses overnight; however, after discontinuation (two CL fractures, one under-correction and two non-serious adverse events), 16 subjects (31 eyes) finished a 3-month follow-up. Corneoscleral topographies were acquired using the Eye Surface Profiler (ESP) system before and after 3 months of lens wear. Steep (SimKs) and flat (SimKf) simulated keratometry and scleral sagittal height measurements for 13-, 14- and 15-mm chord lengths were automatically calculated by the ESP software. Additionally, sagittal height and slope were calculated in polar format from 21 radii (0-10 mm from the corneal apex) at 12 angles (0-330°). Linear mixed models were fitted to determine the differences between visits.

RESULTS

SimKs and SimKf were increased significantly (p ≤ 0.02). The sagittal height in polar format increased significantly (p = 0.046) at a radius of 2.5 mm for 150°, 180°, 210° and 240° orientations and at a radius of 3.0 mm for 210°. Additionally, the slope in polar format significantly decreased (p ≤ 0.04) at radii ranges of 0.0-0.5, 0.5-1.0 and 1.0-1.5 mm for multiple angles and at a radii range of 5.0-5.5 mm for 90°. It also increased significantly (p ≤ 0.045) at a radii range of 1.5-2.0 mm for 30° and at radii ranges of 2.0-2.5, 2.5-3.0 and 3.0-3.5 mm for multiple angles. No significant changes were found for any parameter measured from the scleral area.

CONCLUSIONS

Three months of overnight ortho-k lens wear changed the central and mid-peripheral corneal geometry as expected, maintaining the peripheral cornea and the surrounding sclera stability.

The Potential of Selenium-Based Therapies for Ocular Oxidative Stress

Oxidative stress plays a critical role in the development of chronic ocular conditions including cataracts, age-related macular degeneration, and diabetic retinopathy. There is a need to explore the potential of topical antioxidants to slow the progression of those conditions by mediating oxidative stress and maintaining ocular health. Selenium has attracted considerable attention because it is a component of selenoproteins and antioxidant enzymes. The application of selenium to a patient can increase selenoprotein expression, counteracting the effect of reactive oxygen species by increasing the presence of antioxidant enzymes, and thus slowing the progression of chronic ocular disorders. Oxidative stress effects at the biomolecular level for prevalent ocular conditions are described in this review along with some of the known defensive mechanisms, with a focus on selenoproteins. The importance of selenium in the eye is described, along with a discussion of selenium studies and uses. Selenium's antioxidant and anti-inflammatory qualities may prevent or delay eye diseases. Recent breakthroughs in drug delivery methods and nanotechnology for selenium-based ocular medication delivery are enumerated. Different types of selenium may be employed in formulations aimed at managing ocular oxidative stress conditions.

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.

Eye Diseases: When the Solution Comes from Plant Alkaloids

Plants are an incredible source of metabolites showing a wide range of biological activities. Among these, there are the alkaloids, which have been exploited for medical purposes since ancient times. Nowadays, many plant-derived alkaloids are the main components of drugs used as therapy for different human diseases. This review deals with providing an overview of the alkaloids used to treat eye diseases, describing the historical outline, the plants from which they are extracted, and the clinical and molecular data supporting their therapeutic activity. Among the different alkaloids that have found application in medicine so far, atropine and pilocarpine are the most characterized ones. Conversely, caffeine and berberine have been proposed for the treatment of different eye disorders, but further studies are still necessary to fully understand their clinical value. Lastly, the alkaloid used for managing hypertension, reserpine, has been recently identified as a potential drug for ameliorating retinal disorders. Other important aspects discussed in this review are different solutions for alkaloid production. Given that the industrial production of many of the plant-derived alkaloids still relies on extraction from plants, and the chemical synthesis can be highly expensive and poorly efficient, alternative methods need to be found. Biotechnologies offer a multitude of possibilities to overcome these issues, spanning from genetic engineering to synthetic biology for microorganisms and bioreactors for plant cell cultures. However, further efforts are needed to completely satisfy the pharmaceutical demand.

Extracellular vesicle encapsulated nicotinamide delivered via a trans-scleral route provides retinal ganglion cell neuroprotection

The progressive and irreversible degeneration of retinal ganglion cells (RGCs) and their axons is the major characteristic of glaucoma, a leading cause of irreversible blindness worldwide. Nicotinamide adenine dinucleotide (NAD) is a cofactor and metabolite of redox reaction critical for neuronal survival. Supplementation with nicotinamide (NAM), a precursor of NAD, can confer neuroprotective effects against glaucomatous damage caused by an age-related decline of NAD or mitochondrial dysfunction, reflecting the high metabolic activity of RGCs. However, oral supplementation of drug is relatively less efficient in terms of transmissibility to RGCs compared to direct delivery methods such as intraocular injection or delivery using subconjunctival depots. Neither method is ideal, given the risks of infection and subconjunctival scarring without novel techniques. By contrast, extracellular vesicles (EVs) have advantages as a drug delivery system with low immunogeneity and tissue interactions. We have evaluated the EV delivery of NAM as an RGC protective agent using a quantitative assessment of dendritic integrity using DiOlistics, which is confirmed to be a more sensitive measure of neuronal health in our mouse glaucoma model than the evaluation of somatic loss via the immunostaining method. NAM or NAM-loaded EVs showed a significant neuroprotective effect in the mouse retinal explant model. Furthermore, NAM-loaded EVs can penetrate the sclera once deployed in the subconjunctival space. These results confirm the feasibility of using subconjunctival injection of EVs to deliver NAM to intraocular targets.

Higher intraocular pressure is associated with slower axial growth in children with non-pathological high myopia

OBJECTIVES

To investigate the association between intraocular pressure (IOP) and axial elongation rate in highly myopic children from the ZOC-BHVI High Myopia Cohort Study.

METHODS

162 eyes of 81 healthy children (baseline spherical equivalent: -6.25 D to -15.50 D) aged 7-12 years with non-pathological high myopia were studied over five biennial visits. The mean (SD) follow-up duration was 5.2 (3.3) years. A linear mixed-effects model (LMM) was used to assess the association between IOP (at time point t-1) and axial elongation rate (annual rate of change in AL from t-1 to t), controlling for a pre-defined set of covariates including sex, age, central corneal thickness, anterior chamber depth and lens thickness (at t-1). LMM was also used to assess the contemporaneous association between IOP and axial length (AL) at t, controlling for the same set of covariates (at t) as before.

RESULTS

Higher IOP was associated with slower axial growth (β = -0.01, 95% CI -0.02 to -0.005, p = 0.001). There was a positive contemporaneous association between IOP and AL (β = 0.03, 95% CI 0.01-0.05, p = 0.004), but this association became progressively less positive with increasing age, as indicated by a negative interaction effect between IOP and age on AL (β = -0.01, 95% CI -0.01 to -0.003, p = 0.001).

CONCLUSIONS

Higher IOP is associated with slower rather than faster axial growth in children with non-pathological high myopia, an association plausibly confounded by the increased influence of ocular compliance on IOP.

Assessment of dynamic corneal response parameters in Chinese patients of different ages with myopia and orthokeratology lenses using the Corvis ST

OBJECTIVE

To investigate the effects of orthokeratology lenses (OK lenses) on corneal biomechanics in subjects of different ages.

METHODS

Fifty subjects with mild to moderate myopia were categorized into three groups (Group I-III) based on their age. Corvis ST was used to collect dynamic corneal response parameters (DCRs) at different follow-up time points. Repeated measures analysis of variance combined with simple effect analysis was used to analyze the changes in DCRs in different groups during the follow-up period. Multiple linear regression analysis was used to analyze the correlations between axial length growth (ALG) at 6 months (ALG-6M) or 12 months (ALG-12M) and sex, baseline spherical equivalent refraction (SER), and DCRs.

RESULTS

The DCRs changed in all three groups after wearing OK lenses. Most DCRs showed significant differences between baseline and 6 months after wearing OK lenses, while the differences between DCRs at 6 months and 12 months were not statistically significant. No significant differences in DCRs were observed among the three groups at the same follow-up time point. Additionally, at 6 months post-OK lens wear, ALG-6M was significantly correlated with velocity of the corneal apex at the first applanation (A1V-6M) (P = 0.002), Corvis biomechanical index (CBI-6M) (P = 0.004), the maximum amount of corneal movement (DAM-6M) (P = 0.010), deformation amplitude ratio of 2 mm (DAR2-6M) (P = 0.010), and stress-strain index (SSI-6M) (P = 0.038) in Group I. Furthermore, ALG-12M showed significant correlations with SSI-6M (P = 0.031), peak distance at the DAM (PD)-6M (P = 0.037), baseline Ambrósio Relational Thickness to the horizontal profile (P = 0.013) in Group I.

CONCLUSIONS

The majority of DCRs displayed significant changes within the initial 6 months of OK lens wear. Minimal variation in DCRs was observed across different age groups at the same follow-up time point. Certain DCR parameters exhibited correlations with ALG, suggesting their potential in predicting ALG in myopic children undergoing OK lenses correction.

Eye morphometry, body size, and flexibility parameters in myopic adolescents

The aim of this study was to investigate the anatomical and physiological ocular parameters in adolescents with myopia and to examine the relations between refractive error (SER), ocular biometry, body size and flexibility parameters in myopic adolescents. A cross-sectional study of 184 myopic adolescents, aged 15 to 19 years was conducted. Refractive error and corneal curvature measures of the eye were evaluated using an autorefractometer under cycloplegia. Central corneal thickness was determined by contact pachymetry. The ocular axial length, anterior and vitreous chamber depth, and lens thickness were measured using A-scan biometry ultrasonography. Height and body weight were measured according to a standardized protocol. Body mass index (BMI) was subsequently calculated. Beighton scale was used to measure joint flexibility. Body stature was positively correlated with ocular axial length (r = 0.39, p < 0.001) and vitreous chamber depth (r = 0.37, p < 0.001). There was a negative correlation between height and SER (r = - 0.46; p < 0.001). Beighton score and body weight had weak positive correlations with axial length and vitreous chamber depth, and a weak negative correlation with SER. A significantly more negative SER was observed in the increased joint mobility group (p < 0.05; U = 5065.5) as compared to normal joint mobility group: mean - 4.37 ± 1.85 D (median - 4.25; IQR - 6.25 to - 3.25 D) and mean - 3.72 ± 1.66 D (median - 3.50; IQR - 4.75 to - 2.25 D) respectively. There was a strong association between height and axial length, as well as SER. Higher degree of myopia significantly correlated with greater Beighton score (increased joint mobility).