Safety and Long-term Scleral Biomechanical Stability of Rhesus Eyes after Scleral Cross-linking by Blue Light

Analysis of factors related to the development of ocular biometric parameters in Chinese children aged 6-10 years: a cross-sectional study

OBJECTIVES

Emmetropia depends on the precise coordination of ocular biometry, including axial length (AL), corneal curvature, lens thickness and anterior chamber depth (ACD). Disruption of this coordination leads to refractive errors such as myopia. This article aimed to determine the factors affecting ocular biometry and myopia development in young children.

DESIGN

A cross-sectional study.

SETTING

This study was conducted in a primary school in the Yanqing district of Beijing, China.

PARTICIPANTS

792 students in grades 1-3 without hyperopia (>+2.00 D), strabismus, or amblyopia were selected.

EXCLUSIONS

students had conditions affecting best corrected visual acuity and whose guardians refused to provide informed consent. Ocular biometric measurements and non-cycloplegia autorefraction were performed. The questionnaire addressed factors such as perinatal factors and environmental factors.

INTERVENTIONS

None.

PRIMARY AND SECONDARY OUTCOMES

Ocular biometry and myopia.

RESULTS

According to the multivariate logistic regression analysis, electronic screen use >2 hours/day (OR=2.175, p=0.013), paternal myopia (OR=1.761, p=0.002), maternal myopia (OR=1.718, p=0.005), taller height (OR=1.071, p<0.001), maternal education (OR=0.631, p=0.012) and maternal gestational hypertension (OR=0.330, p=0.042) were associated with myopia. AL was affected by female sex (OR=0.295, p<0.001), older age (OR=1.272, p=0.002) and taller height (OR=1.045, p<0.001). Female sex (OR=0.509, p<0.001), taller height (OR=1.046, p<0.001), use of electronic screens >2 hours each day (OR=3.596, p<0.001) and time spent outdoors >2 hours each day (OR=0.431, p=0.001) influenced ACD incidence. Central corneal thickness (CCT) was associated with older age (OR=1.113, p=0.008), paternal education (OR=1.474, p=0.007), premature birth (OR=0.494, p=0.031), history of blue light therapy in infancy (OR=0.636, p=0.041) and history of incubator therapy in infancy (OR=0.263, p=0.009). Only sex influenced corneal curvature.

CONCLUSIONS

The factors associated with myopia were partly related to ACD and AL, and perinatal factors were associated with myopia and CCT.

TRIAL REGISTRATION NUMBER

ChiCTR2200065398.

A meta-analysis of randomized controlled trials evaluating the effectiveness and safety of the repeated low-level red light therapy in slowing the progression of myopia in children and adolescents

PURPOSE

The aim of this study was to evaluate the effectiveness and safety of repeated low-level red light (RLRL) therapy in controlling myopia progression in children through a meta-analysis.

METHODS

We searched several databases including PubMed, Embase, The Cochrane Library, Web of Science, CNKI, WANFANG, CBM, and VIP with languages restricted to both Chinese and English. The search was conducted from the establishment of the databases to March 23, 2023. We collected randomized controlled trials and controlled experiments to evaluate changes in axial length (AL) and spherical equivalent (SE) before and after RLRL intervention. Two researchers performed literature screening and data extraction, and RevMan software (Ver 5.3) and StataMP 17.0 were used for meta-analysis.

RESULTS

A total of 141 articles were retrieved, and finally, six randomized controlled trials met the inclusion and exclusion criteria, including 820 eyes (RLRL group: 411 eyes, control group: 409 eyes). The meta-analysis results showed that the RLRL group was significantly better than the control group in controlling AL, and the difference between the two groups was statistically significant (mean difference [MD] = -0.22, 95% confidence interval [CI] [ - 0.28, -0.16]; P < 0.001). The RLRL group was also better than the control group in terms of SE, and the difference between the two groups was statistically significant (MD = 0.46, 95% CI [0.32, 0.6]; P < 0.001). Five studies reported adverse reactions in the RLRL group, and two cases stopped treatment due to the feeling of too bright light, while the others had no significant side effects in the short term.

CONCLUSION

RLRL therapy is a safe and effective method for controlling myopia, which can inhibit the growth of AL and slow down the progression of myopia. However, further research and validation are needed to determine its treatment efficacy and course.

Changes in intraocular pressure and ocular pulse amplitude of rhesus macaques after blue light scleral cross-linking

BACKGROUND

Scleral cross-linking can enhance the biomechanical strength of the sclera and is expected to be a new operative method for the prevention of myopia. However, studies investigating the changes in intraocular pressure (IOP) and ocular pulse amplitude (OPA) after blue light-riboflavin induced scleral collagen cross-linking (SXL) in rhesus monkeys are limited. This study aimed to investigate the changes in IOP and OPA in three-year-old rhesus macaques 1 week, 1 month, and 3 months after blue light-riboflavin SXL.

METHODS

Seven three-year-old rhesus macaques (14 eyes) were randomly divided into two groups, with 4 monkeys in group A (8 eyes) and 3 monkeys in group B (6 eyes). The right eye of each rhesus macaque was used as the experimental eye, whereas the left eye was used as the control. In group A, one quadrant of each right eye was irradiated. In group B, two quadrants of each right eye and one quadrant of each left eye were irradiated. The IOP and OPA of both eyes were measured in all seven rhesus macaques before SXL and 1 week, 1 month, and 3 months postoperatively, and differences in the IOP and OPA between the experimental and control eyes were evaluated via the paired t test.

RESULTS

In groups A and B, there were no significant differences between the experimental and control eyes in the IOP or OPA before SXL or 1 week, 1 month, or 3 months postoperatively (P > 0.05).

CONCLUSIONS

The IOP and OPA are not significantly affected in 1 vs 0 or in 1 vs 2 quadrants of blue light SXL.

Shaping Eyeballs by Scleral Collagen Cross-Linking: A Hypothesis for Myopia Treatment

The global prevalence of myopia has brought to the attention of the different eye and vision specialists, who make way to control its progression. Evidence have shown that a proactive reshaping of the eyeball is the core point of myopia developing process, which particularly includes the weakening, thinning, and expanding of the sclera. Thus, the sclera is considered to be a prime target for therapeutic manipulation in halting progressive myopia. In the past decades, corneal collagen cross-linking has been applied in clinical practice for treating aberrant corneal remodeling diseases. In this article, we hypothesize that scleral collagen cross-linking (SXL) has a huge potential in stabilizing myopic process by shaping the eyeball and preventing the aberrant scleral remodeling. In contrast with the current methods of optometry correction, such as physiotherapy, pharmacotherapy, spectacles, contact lenses, refractive surgeries, etc., eyeball-shaping method using SXL is a fundamental intervention which aims at the pathogenesis of progressive visual loss of myopia. Compared with the current posterior scleral reinforcement, the most advantage of SXL is that there is no allotransplant into the myopic eye, which means less expenditure, lower risk, and easier to handle in operating.

Biomechanics of Ophthalmic Crosslinking

Crosslinking involves the formation of bonds between polymer chains, such as proteins. In biological tissues, these bonds tend to stiffen the tissue, making it more resistant to mechanical degradation and deformation. In ophthalmology, the crosslinking phenomenon is being increasingly harnessed and explored as a treatment strategy for treating corneal ectasias, keratitis, degenerative myopia, and glaucoma. This review surveys the multitude of exogenous crosslinking strategies reported in the literature, both "light" (involving light energy) and "dark" (involving non-photic chemical processes), and explores their mechanisms, cytotoxicity, and stage of translational development. The spectrum of ophthalmic applications described in the literature is then discussed, with particular attention to proposed therapeutic mechanisms in the cornea and sclera. The mechanical effects of crosslinking are then discussed in the context of their proposed site and scale of action. Biomechanical characterization of the crosslinking effect is needed to more thoroughly address knowledge gaps in this area, and a review of reported methods for biomechanical characterization is presented with an attempt to assess the sensitivity of each method to crosslinking-mediated changes using data from the experimental and clinical literature. Biomechanical measurement methods differ in spatial resolution, mechanical sensitivity, suitability for detecting crosslinking subtypes, and translational readiness and are central to the effort to understand the mechanistic link between crosslinking methods and clinical outcomes of candidate therapies. Data on differences in the biomechanical effect of different crosslinking protocols and their correspondence to clinical outcomes are reviewed, and strategies for leveraging measurement advances predicting clinical outcomes of crosslinking procedures are discussed. Advancing the understanding of ophthalmic crosslinking, its biomechanical underpinnings, and its applications supports the development of next-generation crosslinking procedures that optimize therapeutic effect while reducing complications.

Transpupillary collagen photocrosslinking for targeted modulation of ocular biomechanics

The central vision-threatening event in glaucoma is dysfunction and loss of retinal ganglion cells (RGCs), thought to be promoted by local tissue deformations. Here, we sought to reduce tissue deformation near the optic nerve head by selectively stiffening the peripapillary sclera, i.e. the scleral region immediately adjacent to the optic nerve head. Previous scleral stiffening studies to treat glaucoma or myopia have used either pan-scleral stiffening (not regionally selective) or regionally selective stiffening with limited access to the posterior globe. We present a method for selectively stiffening the peripapillary sclera using a transpupillary annular light beam to activate methylene blue administered by retrobulbar injection. Unlike prior approaches to photocrosslinking in the eye, this approach avoids the damaging effects of ultraviolet light by employing red light. This targeted photocrosslinking approach successfully stiffened the peripapillary sclera at 6 weeks post-treatment, as measured by whole globe inflation testing. Specifically, strain was reduced by 47% when comparing treated vs. untreated sclera within the same eye (n = 7, p=0.0064) and by 54% when comparing the peripapillary sclera of treated vs. untreated eyes (n = 7, p<0.0001). Post-treatment characterization of RGCs (optic nerve axon counts/density, and grading), retinal function (electroretinography), and retinal histology revealed that photocrosslinking was associated with some ocular toxicity. We conclude that a transpupillary photocrosslinking approach enables selective scleral stiffening targeted to the peripapillary region that may be useful in future treatments of glaucoma.