The efficacy and safety of posterior scleral reinforcement using genipin cross-linked sclera for macular detachment and retinoschisis in highly myopic eyes

Analysis of morphological and quantitative changes in pathological myopia and perioperative changes in posterior scleral reinforcement using three-dimensional magnet resonance imaging

Objective: To compare the morphological and quantitative changes in pathological myopia (PM) and the perioperative changes in posterior scleral reinforcement (PSR) using three-dimensional magnetic resonance images (3D MRI). Methods: A total of 49 patients with high myopia (HM; 98 eyes), 15 with pathological myopia (PM; 19 eyes), and 10 without high myopia (NORM; 20 eyes) were recruited between September 2019 and July 2021. The patients underwent measurements of refractive error and axial length, as well as 3D MRI of the eyeball. Python was used to analyze the 3D MRI images, calculate the vitreous volume, establish a topography of the height of the eyeball posterior surface, and calculate the rate of change in height (H). For the PM group undergoing PSR, changes in vitreous volume and the highest point of the eyeball posterior surface in four quadrants (temporal, subtemporal, nasal, and subnasal) were compared before and after PSR. Results: The vitreous volume was smaller in the NORM group compared to the HM and PM groups (p < 0.01). The PM group had a larger volume than the HM group (p < 0.01). The H for the PM group was higher than that of the NORM and HM groups (p < 0.01). After PSR in the PM group, the total vitreous volume, as well as the volume in the subnasal and supratemporal quadrants, decreased (p < 0.05). Additionally, the highest point of the eyeball's posterior surface was generally shifted to the upper nasal side. Finally, the shape and position of the scleral band after PSR were plotted. Conclusion: 3D MRI is capable of a quantitative description of the eyeball morphology in PM and PSR. It allows for precise calculations of changes in vitreous volume and the H of the posterior surface. It also facilitates a meticulous analysis of the specific details of the scleral band following PSR.

Posterior scleral reinforcement for the treatment of myopic traction maculopathy

Background

This study aimed to investigate the clinical effectiveness of posterior scleral reinforcement(PSR) for the treatment of myopic traction maculopathy (MTM).

Methods

This was a prospective study of 32 eyes from 20 patients with MTM treated with PSR using genipin-cross-linked donor sclera. The length of the scleral strip used for the surgery was designed to be 1.5-times the axial length of the eye, whereas its width was 0.4-times the axial length of the eye. The optical coherence tomography images, spherical equivalent of refractive error, axial length, best corrected visual acuity, electroretinogram findings, and intraocular pressure of the patients were assessed postoperatively.

Results

The mean duration of follow-up was 17.80 ± 8.74 months. The differences between the spherical equivalent of refractive error, best corrected visual acuity, axial length, and electroretinogram findings recorded preoperatively and those measured postoperatively were statistically significant (p < 0.05). The final reduction in axial length was 1.64 ± 0.85 mm. At the end of the follow-up, optical coherence tomography showed essential foveal reattachment in 30 eyes (93.75%), partial reattachment in two eyes (6.25%), and closure of macular holes in seven eyes (77.78%). No retinal detachment, vitreous haemorrhage, or other serious complications occurred following the surgery.

Conclusions

Posterior scleral reinforcement with genipin-cross-linked sclera showed safe and effective outcomes for the treatment of MTM during a follow-up period of at least one year.

Trial registration

11\12\2018, ChiCTR1800020012.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02497-6.

Biomechanical Considerations of Patching Material for Posterior Scleral Reinforcement Surgery

Purpose

To characterize biomechanical properties of genipin-crosslinked human dura mater as reinforcing material for posterior scleral reinforcement (PSR) and to compare it with crosslinked human sclera.

Methods

Donor dura mater and sclera were crosslinked in the same optimized genipin solution. Resistance to enzyme degradation for both materials were investigated by exposing the materials to accelerated enzyme degrading. Elastic modulus and tensile strength were measured by biomechanics testing equipment. Crosslinked human dura mater was used as reinforcing patch in PSR on 57 adult pathologic myopic eyes. The patients were followed up for an average 3 years. The main outcome was eye globe axial length change and safety profile of the reinforcing material.

Results

Crosslinked dura mater demonstrated similar percentage weight loss to crosslinked sclera when exposed to enzymatic solution. Dura mater has higher density than sclera. The retaining elastic modulus after enzyme exposure was 72.02 MPa for crosslinked dura mater while 53.88 MPa for crosslinked sclera, 34% greater for crosslinked dura mater, P = 0.0186). At the end of 3 years follow-up, the mean globe axis of the surgery eyes was reduced by 1.29 mm (from 30.81 to 29.51 mm, P < 0.0001, paired t-test). Visual acuity (BCVA logMar) improved by 0.10 logMar unit which is an improvement of five letters (P = 0.0184, paired t-test). No material specific complication was noted.

Conclusion

Crosslinked human dura mater may be superior to crosslinked human sclera as reinforcing material for PSR to manage progression of high myopia. This material was well tolerated on human eye.

A Potential Research Target for Scleral Remodeling: Effect of MiR-29a on Scleral Fibroblasts

INTRODUCTION

The purpose of this study was to determine whether miR-29a regulates cell survival and apoptosis and the expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), MMP-2, and collagen I in scleral fibroblasts.

METHODS

We transfected scleral fibroblasts with the miR-29a mimic and inhibitor. The effects of miR-29a on cell proliferation and apoptosis were determined using the CCK-8 assay and flow cytometry, respectively. Quantitative polymerase chain reaction (qPCR) was used to determine whether miR-29a regulates the mRNA levels of PTEN, MMP-2, and collagen I. The protein expression of PTEN, MMP-2, and collagen I was also assessed by western blot analysis.

RESULTS

The results of CCK-8 showed that, at 0, 24, 48, and 72 h after transfection, the relative optical density values in the mimic group were 0.233 ± 0.005, 0.380 ± 0.008, 0.650 ± 0.040, and 0.906 ± 0.032, and in the inhibitor group were 0.272 ± 0.011, 0.393 ± 0.029, 0.597 ± 0.059, and 0.950 ± 0.101, respectively. The flow cytometry results showed that the apoptosis rates of each group were as follows: the mimic group (0.043 ± 0.007), the NC group (0.040 ± 0.006), the inhibitor group (0.032 ± 0.003), the inhibitor NC group (0.027 ± 0.010), the lipofectamine group (0.027 ± 0.005), and the blank group (0.031 ± 0.009). The qPCR results indicated that in the mimic group, PTEN (0.795 ± 0.182, p = 0.2783), MMP-2 (0.621 ± 0.105, p = 0.0033), and COL1A1 (0.271 ± 0.100, p = 0.0002) expression decreased, whereas in the inhibitor group, PTEN (1.211 ± 0.100, p = 0.2614), MMP-2 (1.161 ± 0.053, p = 0.1190), and COL1A1 (1.7040 ± 0.093, p = 0.0003) increased. Western blot analysis showed that in the mimic group, the expression of PTEN (0.392 ± 0.039, p < 0.0001), MMP-2 (0.577 ± 0.017, p < 0.0001), and COL1A1 (0.072 ± 0.006, p < 0.0001) protein decreased, whereas in the inhibitor group, PTEN (1.043 ± 0.042, p = 0.9413), MMP-2 (1.397 ± 0.075, p = 0.0002), and COL1A1 (1.935 ± 0.081, p < 0.0001) expression increased.

CONCLUSION

MiR-29a inhibits the expression of PTEN, MMP-2, and collagen I on scleral fibroblasts, which may provide a basis studies in sclera.

Scleral Cross-Linking in Form-Deprivation Myopic Guinea Pig Eyes Leads to Glaucomatous Changes

Purpose

To investigate the potential glaucomatous changes caused by scleral cross-linking (CXL) in a guinea pig form-deprivation (FD) myopia model.

Methods

Eighty 4-week-old tricolor guinea pigs were divided into four groups: FD only, genipin CXL only, FD plus CXL, and control. Refractive error, axial length (AL), intraocular pressure (IOP), and structural and vasculature optic disc changes in optical coherence tomography (OCT) and OCT angiography (OCTA) were measured at baseline and day 21. CXL efficacy was evaluated by scleral rigidity Young's modulus values. Histological and molecular changes in the anterior chamber angle, retina, and sclera were assessed.

Results

Baseline parameters were similar among groups (P > 0.05). The FD plus CXL group at day 21 had the least increase of AL (0.14 ± 0.08 mm) and highest IOP elevation (31.5 ± 3.6 mmHg) compared with the FD-only group (AL: 0.68 ± 0.17 mm; IOP: 22.2 ± 2.6 mmHg) and the control group (AL: 0.24 ± 0.09 mm; IOP: 17.4 ± 1.8 mmHg) (all P < 0.001). OCT and OCTA parameters of the optic disc in the FD plus CXL group at day 21 showed glaucomatous changes and decreased blood flow signals. Sclera rigidity increased in the CXL and FD plus CXL groups. Advanced glycation end products deposited extensively in the retina, choroid, and sclera of FD plus CXL eyes.

Conclusions

CXL causes increased IOP and subsequent optic disc, anterior segment, and scleral changes while inhibiting myopic progression and axial elongation in FD guinea pig eyes. Therefore, applying CXL to control myopia raises safety concerns.

Genipin Cross-Linked Decellularized Nucleus Pulposus Hydrogel-Like Cell Delivery System Induces Differentiation of ADSCs and Retards Intervertebral Disc Degeneration

Intervertebral disc degeneration (IDD) is the pathological basis of disc degenerative diseases (DDD). Reduction in the number of cells and degeneration of the extracellular matrix (ECM) in the nucleus pulposus (NP) are characteristics of IDD. Bio-hydrogel combined with stem cell transplantation is a promising treatment. Injectable ECM hydrogels have good biological activity and in-situ gelatinization. However, its biomechanics and stability are insufficient to provide adequate mechanical support for intervertebral discs and to maintain the long-term differential stimulus for seeded stem cells. In our study, we developed genipin cross-linked decellularized nucleus pulposus hydrogel (GDH) as delivery system. We evaluated the mechanical properties, stability, biocompatibility, and differentiation induction of GDH cross-linked with different concentrations of genipin in vitro. The GDH-loaded adipose-derived mesenchymal stem cells (ADSCs) (GDHA) were injected into the rat degenerated coccygeal intervertebral disc. The effect of intervertebral disc regeneration in vivo was evaluated. The results showed that GDH with 0.02% of genipin had similar elastic modulus to human nucleus pulposus, good biocompatibility, and inducibility of expressing NP-related genes. In vivo studies showed that GDHA improved the survival of ADSCs and improved the intervertebral height, MRI index, and histological grading score. In conclusion, GDH, as an outstanding bio-hydrogel cell delivery system, has the therapeutic potential for retarding IDD.

POSTERIOR SCLERAL CONTRACTION TO TREAT MYOPIC FOVEOSCHISIS IN HIGHLY MYOPIC EYES

PURPOSE

To evaluate the efficacy of posterior scleral contraction to treat myopic foveoschisis (MF).

METHODS

The records of MF patients treated with posterior scleral contraction were reviewed. During posterior scleral contraction, a cross-linked fusiform strip from allogeneic sclera was used and designed axial length (AL) shortening amount was around 2.0∼3.0 mm based on preoperative AL. The middle part of the strip was placed at the posterior pole of the eye. After few aqueous humors were released, the strip was tightened to contract posterior sclera and shorten AL. Clinical data were collected at pre-operation (op) and post-op follow-ups for 12 months.

RESULTS

Twenty-four eyes were collected. The AL at pre-op, post-op 1-week, 3-month, 6-month, and 12-month were 29.84 ± 1.24, 27.39 ± 1.32, 27.73 ± 1.23, 27.86 ± 1.26, and 27.91 ± 1.29 mm. There was no AL difference between post-op 6-month and 12-month (P = 0.242). The accumulated MF reattachment rate at post-op 1-week, 3-month, 6-month, and 12-month were 8.3%, 16.7%, 50.5%, and 95.8%. The best-corrected visual acuity at post-op 6-month and 12-month were 0.71 ± 0.39 (Snellen acuity 20/80) and 0.64 ± 0.37 (Snellen acuity 20/63), improving significantly compared with pre-op (P = 0.006 and <0.001).

CONCLUSION

The posterior scleral contraction was effective to treat MF. The AL stabilized after post-op 6-month and MF reattached gradually with improved visual acuity up to post-op 12-month.

Investigation of Macular Choroidal Thickness and Blood Flow Change by Optical Coherence Tomography Angiography After Posterior Scleral Reinforcement

Purpose: This work aimed to study the effect of posterior scleral reinforcement (PSR) on choroidal thickness (CT) and blood flow.

Methods: This study included 25 eyes of 24 patients with high myopia ( ≤ -6.0 dioptres or axial length ≥ 26.0 mm) who underwent PSR surgery. All patients completed the 1-month follow-up visit. Myopic macular degeneration (MMD) was graded according to the International Meta-Analysis for Pathologic Myopia (META-PM) classification based on color fundus photographs. Swept-source optical coherence tomography angiography (SSOCTA) was performed to investigate CT, choroidal perfusion area (CPA), and choriocapillaris perfusion area (CCPA) change following PSR surgery.

Results: The distribution of MMD categories was 9 (36.0%) in category 1, 10 (40.0%) in category 2, and 6 (24.0%) in category 3 or 4. MMD severity was strongly correlated with CT (all P < 0.01) and CPA (all P < 0.04). Postoperative CT at each sector increased significantly at 1 week's follow-up, compared to preoperative measures (all P < 0.05). Postoperative CPA at subfoveal, superior, inferior, and nasal sectors also increased significantly 1 week after PSR surgery (all P < 0.05). Moreover, the increased CT, CPA, and CCPA remain after PSR surgery at 1 month's follow-up, but the difference was not statistically significant.

Conclusions: We demonstrated that the CT and choroidal blood flow increased significantly in patients with high myopia who underwent PSR surgery in a short period of time. In addition, the CT and CPA were independently associated with MMD. However, whether the transient improvement of the choroidal circulation could prevent long-term progression of high myopia warrants further study in the future.

A customized posterior scleral reinforcement for myopic macular hole with retinal detachment and posterior staphyloma: A case report

The author describes a customized posterior scleral reinforcement, its manufacturing method, the rationale of its therapeutic effect, and the surgical technique of its implantation. A 54-year-old female patient with a case history of myopic macular hole with retinal detachment and posterior staphyloma, refractory to pars plana vitrectomy and peeling of internal limiting membrane, underwent posterior scleral reinforcement treatment. Retinal reattachment and macular hole closure were obtained. Best corrected visual acuity increased from light perception to 20/160 Snellen. The pars plana vitrectomy is mandatory to remove vitreoretinal tractions and epiretinal membranes; furthermore, the internal limiting membrane peeling makes retina less rigid. However, it may not be sufficient to allow retinal reattachment and it plays no preventive role in limiting posterior staphyloma progression. The rationale of posterior scleral reinforcement is to reduce retinal stretching, to contain posterior staphyloma, and to limit its progression over time.

Comparison of macular buckling and vitrectomy for the treatment of macular schisis and associated macular detachment in high myopia: a randomized clinical trial

OBJECTIVE

To compare the efficacy and safety of macular buckling and vitrectomy for myopic traction maculopathy showing macular schisis (MS) and associated macular detachment (MD) but without full-thickness macular hole (FTMH).

DESIGN

Prospective, randomized, parallel, open-label study.

METHODS

Patients were randomly assigned to either buckling or vitrectomy group. Macular buckling and intravitreal C3F8 gas injection were performed in the buckling group. Small gauge vitrectomy, internal limiting membrane peeling (ILMP) and C3F8 gas tamponade were performed in the vitrectomy group. The patients were followed for 12 months.

MAIN OUTCOME MEASURES

Best-corrected visual acuity (BCVA) at 12 months.

RESULTS

A total of 85 patients were randomized, 80 eyes were included (41 receiving buckling, 39 received vitrectomy), and 78 patients completed the study. There were less eyes determined as surgical failure and required a second surgery in the buckling group than vitrectomy the group (2.4% versus 18.4%, p = 0.021). After surgery, macular buckling achieved more improvement in BCVA (+21.7 versus +4.5 Early Treatment Diabetic Retinopathy Study (ETDRS) letters, p = 0.002). FTMH development was observed in only 1 (2.4%) eye, after removing of the implant due to recurrent conjunctival erosion, in the buckling group and 10 (26.3%) eyes (seven with-, three without MD) in the vitrectomy group (p < 0.001). More eyes developed cataracts in the vitrectomy group than did in the buckling group (28.9% versus 7.5%, p = 0.014). Macular buckling-associated strabismus (esotropia), binocular diplopia and implant exposure were observed in limited cases.

CONCLUSIONS AND RELEVANCE

Macular buckling is superior to vitrectomy with ILM peeling plus gas injection for surgical treatment of MS and associated MD in high myopia.

Genipin inhibits the scleral expression of miR-29 and MMP2 and promotes COL1A1 expression in myopic eyes of guinea pigs

PURPOSE

High myopia can lead to blindness. Genipin is a collagen cross-linking agent that may be used to treat myopia. However, the mechanism of action of genipin for the treatment of myopia is unclear. This study investigated the effect of genipin on the scleral expression of the miR-29 cluster, matrix metalloproteinase 2 (MMP2), and collagen alpha1 chain of type I (COL1A1) in a guinea pig model of myopia.

METHODS

The model of myopia was established by treating guinea pigs with a - 8D lens on both eyes for 21 days, and eyes with a refractive error of - 6D or greater were included. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) and western blot were used to examine the mRNA and protein expression, respectively. A dual-luciferase assay was used to determine the direct targeting of the miR-29 cluster on the 3'-untranslated region (UTR) of the COL1A1 gene.

RESULTS

The scleral expression of miR-29a, miR-29b, and miR-29c as well as MMP2 was significantly increased, and the scleral expression of COL1A1 was significantly decreased in the myopia group. Genipin treatment reversed these effects in myopic eyes. The dual-luciferase assay showed that the luciferase activities were significantly decreased in human embryonic kidney (HEK) cells transfected with miR-29a and miR-29b, but not miR-29c, compared with those transfected with control miRNAs.

CONCLUSIONS

Genipin inhibits the scleral expression of the miR-29 cluster and MMP2 and promotes COL1A1 expression in a guinea pig model of myopia. Thus, genipin may promote COL1A1 expression by reducing the expression of the miR-29 cluster.

Outcomes of 23G vitrectomy and internal limiting membrane peeling with brilliant blue in patients with myopic foveoschisis from a retrospective cohort study

The aim of the present study was to investigate whether internal limiting membrane (ILM) peeling in patients with myopic foveoschisis (MF) treated with 23-gauge (23G) vitrectomy improved the anatomical and visual outcomes. In this retrospective cohort study, from March 2014 to August 2017 at the Department of Ophthalmology, The Second Affiliated Hospital of Nanchang University (Nanchang, China), 60 patients (60 eyes) with MF underwent 23G vitrectomy. The patients were grouped according to whether they underwent brilliant blue-assisted ILM peeling (peeling group) or not (non-peeling group). Best-corrected visual acuity (BCVA) and central macular thickness (CMT) on optical coherence tomography were measured. There were 30 eyes in each group and the baseline characteristics were similar (all P>0.05). BCVA improved in 24 eyes (80%) in the peeling group and 25 eyes (83.3%) in the non-peeling group (P=0.922). Preoperative CMT was not significantly different between the peeling and non-peeling group (458±62.2 vs. 460±61.1 µm, respectively, P=0.229). However, postoperative CMT was significantly different between the peeling and non-peeling group (269.3±67.7 vs. 294.4±60.5 µm, respectively; P=0.015). In the peeling group, MF was completely resolved in all 30 eyes, but only in 26 eyes in the non-peeling group (P=0.038). Postoperative Amsler testing was positive in five eyes in the peeling group and 13 eyes in the non-peeling group (P=0.024). Complications were similar in both groups; postoperatively, there were one and two cases of iatrogenic peripheral retinal break, three and two cases of macular hole, and one and one case of retinal detachment in the peeling and non-peeling groups, respectively.23G vitrectomy combined with brilliant blue-assisted ILM peeling resulted in better visual and anatomical effects compared with 23G vitrectomy alone in patients with MF.

Genipin-Crosslinked Donor Sclera for Posterior Scleral Contraction/Reinforcement to Fight Progressive Myopia

Purpose

Myopia has become a global public health problem, particularly in East Asia where myopic retinopathy has become one of the leading causes of blindness and visual impairment in the elderly population. The purpose of this study was to evaluate the efficacy of posterior scleral contraction/reinforcement (PSCR) surgery on controlling the progressive elongation of axial length of highly myopic eyes in young patients.

Methods

This is a prospective self-controlled interventional case series. Forty young patients (<18-years old) with progressive high myopia received PSCR with a genipin-crosslinked donor scleral strip for one eye and the fellow eye served as concurrent control without surgery. The main outcome measurement was the change of axial length over 2 to 3 years of follow-up.

Results

Immediately after the surgery, axial length was shortened and subsequently increased by 0.32 mm over the follow-up period. In contrast, axial length of the fellow eyes increased by 0.82 mm over the same period (P < 0.001, paired t-test). PSCR delayed axial elongation in eyes with or without staphyloma. No significant change of visual acuity, cornea refractive power, or retina thickness was noted between the surgery and fellow eyes. None of the patients lost visual acuity compared with the baseline. The procedure was well tolerated with only temporary corneal refractive axis shifts that recovered by the 6-month postsurgical visit.

Conclusions

PSCR with genipin-crosslinked sclera is safe and effective to restrain eye globe elongation in young patients within a 2- to 3-year follow-up period.

Effects of posterior scleral reinforcement in pathological myopia: a 3-year follow-up study

PURPOSE

To assess the effects of posterior sclera reinforcement (PSR) in refractive outcomes, choroidal thickness (CT), and retinal thickness (RT) during a 3-year follow-up in eyes with pathological myopia.

METHODS

Thirty-eight eyes of 26 adults with pathological myopia who underwent PSR (the PSR group) and 30 eyes of 18 adults with matched age and myopia who did not receive PSR treatment (the control group) were followed up with measurements of axial length (AL), spherical equivalent (SE), best corrected visual acuity (BCVA), CT, and RT at baseline, 1 and 3 months, and 1, 2, and 3 years postoperatively. Data were analyzed by repeated measures analysis of variance and independent-samples t test.

RESULTS

In the PSR group, AL, SE, BCVA, and CT were tending to be relatively stable and no statistically significant changes were found during the follow-up (all P > 0.05). In contrast, in the control group, compared with the measurements taken at baseline, AL, SE, BCVA, and CT altered gradually from 1 month onward to 3 years postoperatively. At 2-year and 3-year follow-ups, significant differences in AL, SE, BCVA, and CT were noted between the PSR group and the control group (all P < 0.05). RTs of the center subfield and the inner ring were equal to the baseline in the control group; however, RTs of the center subfield at 1 year, 2 years, and 3 years postoperatively significantly slightly reduced compared with those at the baseline in the PSR group (all P < 0.05).

CONCLUSIONS

The effects of PSR in restraining eyeball elongation, stabilizing vision, and strengthening the structure of posterior pole are more prominent 2 years or more postoperatively compared with the natural progression of pathological myopia.

Posterior staphyloma in pathologic myopia

A posterior staphyloma is an outpouching of a circumscribed region of the posterior fundus and has been considered a hallmark of pathologic myopia. Occurring in highly myopic eyes, it is histologically characterized by a relatively abrupt scleral thinning starting at the staphyloma edge, a pronounced de-arrangement of scleral collagen fibrils and a marked choroidal thinning, which is the most marked at the staphyloma edge and which occurs in addition to the axial elongation-associated choroidal thinning. Besides in highly myopic eyes, a posterior staphyloma can be found in non-highly myopic eyes in association with retinitis pigmentosa or localized defects of Bruch's membrane in the cases of which it is not associated with a marked choroidal thinning. The diagnosis of posterior staphylomas is considered best made by wide-field optical coherence tomography, because wide-field optical coherence tomography encompasses the entire extent of the most predominant type of staphylomas (i.e., the wide macular type) and since it also has a sufficiently high resolution of images (in contrast to ultrasonography, computed tomography and three-dimensional magnetic resonance imaging). While the etiology of posterior staphylomas has remained unclear, local choroidal factors and a locally decreased biomechanical resistance of the sclera against a posteriorly expanding Bruch's membrane have been one of the assumed pathogenic parameters. For the therapy of staphylomas, scleral reinforcement strategies such as by posterior encircling bands, posterior scleral collagen cross-linking or scleral regeneration have been discussed or performed, however, with the pathogenesis being elusive, the therapy of staphylomas has remained undetermined.

Scleral Cross-Linking Using Glyceraldehyde for the Prevention of Axial Elongation in the Rabbit: Blocked Axial Elongation and Altered Scleral Microstructure

BACKGROUND

This study aims to assess the efficacy of the scleral collagen cross-linking method using glyceraldehyde solution for prevention of lens-induced axial elongation in New Zealand rabbits and investigate the biochemical and microstructural changes that occur.

METHODS

The right eyes of New Zealand rabbits aged seven weeks were randomly divided into three groups: the cross-linking group (n = 6), non-crosslinking group (n = 5), and untreated control group (n = 5). Eyes in cross-linking and non-crosslinking groups were treated with a -8.00 Diopter spherical lens over the course of two weeks. The cross-linking effects were achieved by a sub-Tenon's injection of 0.15 ml 0.5 M glyceraldehyde to eyes in the CL group. Ocular parameters were measured on the 1st, 7^th, and 14th days. Biomechanical testing, light and electronic microscopy were used.

RESULTS

Following the cross-linking treatment, eyes in the cross-linking group had a shorter axial length compared to those in the non-crosslinking group (p = 0.006). Collagen fibrils larger than 240 nm were observed in the scleral stroma of cross-linking group, which were absent in the scleral stroma of the non-crosslinking and untreated control group. The mean ultimate stress and Young's modulus was significantly greater in the cross-linking group compared to those in the non-crosslinking and untreated control group (p < 0.05). No histological damage observed in the retina or choroid.

CONCLUSIONS

This study demonstrates that lens-induced axial elongation in rabbits can be effectively blocked by cross-linking using glyceraldehyde, with anatomical and mechanical modification and no deleterious effects.

Optimizing Genipin Concentration for Corneal Collagen Cross-Linking: An ex vivo Study

PURPOSE

Studying genipin variable concentrations, treatment durations, and delivery methods as a substance to increase corneal stiffness by inducing corneal collagen cross-linking (CXL).

MATERIALS AND METHODS

100 bovine corneas treated with different genipin concentrations (0.1, 0.5, and 1%) and treatment durations (15 min, 40 min, 2 h, and 3 days) through different delivery methods compared to 10 controls treated with riboflavin/UV. Histology examination, enzymatic digestion with collagenase and thermal differential scanning calorimetry were performed on the different samples.

RESULTS

Bovine corneas soaked in 0.5% genipin morphologically showed 4.7% CXL in comparison to 5.6% in controls (p < 0.05). Corneas treated with topical 0.5% genipin, by a 140-µL drop applied hourly for 2 h, showed 7% corneal CXL. Corneas treated with topical genipin 0.5% for 30 min, 1 and 2 h showed 54 ± 6, 40 ± 7, and 39 ± 9% enzymatic degradation, respectively, in comparison to controls (74%). Corneas treated with 0.5% genipin for 1, 2, and 8 h showed higher thermal denaturation resistance (Td values of 64.9 ± 0.3, 64.7 ± 0.0 and 67.3 ± 0.9), respectively, in comparison to the control group (64.6 ± 0.5) (p < 0.05).

CONCLUSIONS

Genipin 0.5%, in a 140-µL drop applied hourly for 2 h, showed better potential to enhance corneal stiffness and stability through inducing CXL.

Posterior scleral reinforcement using genipin-cross-linked sclera for macular hole retinal detachment in highly myopic eyes

Background/aims

To investigate the surgical outcomes of posterior scleral reinforcement (PSR) using genipin-cross-linked sclera to treat macular hole retinal detachment (MHRD) in highly myopic eyes.

Methods

Nineteen patients with high myopia (19 eyes) with MHRD were treated sequentially with genipin-cross-linked PSR and were followed at least for 1 year after the surgery. The best corrected visual acuity (BCVA), axial length (AL), optical coherence tomography (OCT) outcomes and the complications were evaluated.

Results

Macular hole was closed in 73.7% of the eyes, foveal reattachment rate was 100%. The mean logMAR BCVA improved from 1.27±0.55 preoperatively to 0.88±0.55 postoperatively. The preoperative AL (29.88±1.97 mm) was decreased (27.73±1.84 mm) after the operation (p<0.001).

Conclusions

For at least a 1-year period of follow-up, PSR with genipin-cross-linked sclera should be considered as a preferred surgical approach to treat MHRD in highly myopic eyes, especially when foveal retinoschisis is also documented.

Clinical Investigation of the Posterior scleral contraction to Treat Macular Traction Maculopathy in Highly Myopic Eyes

Myopic traction maculopathy (MTM) can cause vision disabilities in highly myopic eyes. This retrospective case series investigated the clinical outcomes of posterior scleral contraction (PSC) using genipin-cross-linked sclera as the material to treat MTM in highly myopic eyes. In total, 32 eyes from 29 highly myopic patients who underwent PSC for MTM were recruited. The changes in best-corrected visual acuity (BCVA) and axial length were evaluated, macular reattachment and macular hole (MH) closure was assessed by optical coherence tomography, and complications were evaluated. At the final follow-up, the retina was completely reattached in 25 eyes (78.1%), essentially reattached in 4 eyes (12.5%), and partially reattached in 3 eyes (9.4%). The logMAR BCVA improved significantly from 1.18 ± 0.45 preoperatively to 0.87 ± 0.45 postoperatively (P < 0.001). The 32 eyes were further divided into the MH group (16 eyes) and the non-MH group (16 eyes) for comparison. The MH was closed in 9 eyes (56.3%). The retinal reattachment rate was 75.0% in the MH group and 81.25% in the non-MH group, and the logMAR BCVA improved significantly in both groups. The PSC using genipin-cross-linked sclera as the material can effectively treat MTM in highly myopic eyes, and significant visual improvement can be achieved with minimal complications.