Inner Limiting Membrane Research Articles

The effect of inner limiting membrane peeling on visual fields: Unravelling a source of bias in glaucoma management

Abstract: Pars plana vitrectomy (PPV) with inner limiting membrane (ILM) peeling aims to improve visual function. Previous studies have focused on visual acuity, often neglecting visual field (VF) changes. This systematic review examines VF changes after PPV with ILM peeling in patients with epiretinal membrane (ERM) or macular hole (MH), including those with glaucoma, who have preexisting VF damage, to identify potential biases in glaucoma management. The inclusion criteria were as follows: (A) Patients undergoing ILM peeling for ERM or MH and (B) VF outcomes assessed through standard automated perimetry (SAP) or Goldmann kinetic perimetry. Exclusions were non-English studies and those with fewer than 30 subjects. Data included retinal disease, demographics, VF outcomes (mean deviation [MD], pattern standard deviation, and central VF sensitivity [CVFS]), study design, and use of stains. Out of 612 studies, 23 met our criteria. Of these, four included glaucoma patients and seven involved concomitant phacoemulsification. In glaucoma patients, two studies showed MD improvement in the central 24°, while one showed deterioration in the central 10°, linked to worse preoperative MD and older age. Among studies without glaucoma patients, three of eight using SAP reported increased VF defects (VFDs); two showed lower outer nasal CVFS postoperatively. Indocyanine green staining was linked to higher VFD incidence while triamcinolone acetonide or tryptane blue staining led to no significant VFDs. The nasal half of the central VF was more affected, possibly due to retinal ganglion cell distribution. Further prospective studies, including randomized controlled trials, are needed to better understand ILM-peeling effects.

Efficacy and safety evaluation of Monoblue Dual View and Monoblue ILM View vital stains during vitrectomy surgery.

To compare the staining properties of Monoblue inner limiting membrane (ILM) View and Monoblue DUAL View (study products) vital stains during vitrectomy surgery to those of ILM Blue or Membrane Blue Dual (control products). In this study, 105 patients were included in the Ophthalmic Clinic of the University Hospitals Leuven from September 2021 to April 2022. For prospective data collection in this study, patients were randomized between a control group (ILM Blue or Membrane Blue Dual, manufactured and commercialized by DORC®) and a study group (Monoblue ILM View or Monoblue DUAL View, manufactured and commercialized by Arcadophta®-BVI®). For retrospective data collection, patients were divided into similar surgery groups. Efficacy was analyzed using a binary subjective evaluation of the visualization of stained membranes during vitrectomy. The rate and severity of potential adverse events related to the study products were tracked, allowing both treatment groups to be compared with the corresponding control groups (ILM Blue and Membrane Blue Dual). Based on the results and findings, none of the comparisons (primary outcomes) were statistically significant, showing similar efficacy of the dyes used. The study products were found to be safe in this study since no serious adverse events were reported. The present findings indicate that the Monoblue ILM View and Monoblue DUAL View dyes can safely be used during vitrectomy to stain the ILM and/or epiretinal membrane (ERM) when removal is needed.

Inner limiting Membrane Peel Extends In vivo Calcium Imaging of Retinal Ganglion Cell Activity Beyond the Fovea in Non-Human Primate.

High resolution retinal imaging paired with intravitreal injection of a viral vector coding for the calcium indicator GCaMP has enabled visualization of activity dependent calcium changes in retinal ganglion cells (RGCs) at single cell resolution in the living eye. The inner limiting membrane (ILM) is a barrier for viral vectors, restricting transduction to a ring of RGCs serving the fovea in both humans and non-human primates (NHP). We evaluate peeling the ILM prior to intravitreal injection as a strategy to expand calcium imaging beyond the fovea in the NHP eye in vivo. Five Macaca fascicularis eyes (age 3-10y; n=3 individuals; 2M, 1F) underwent vitrectomy and 5 to 6-disc diameter ILM peel centered on the fovea prior to intravitreal delivery of 7m8:SNCG:GCaMP8s. Calcium responses from RGCs were recorded using a fluorescence adaptive optics scanning laser ophthalmoscope. In all eyes GCaMP was expressed throughout the peeled area, representing a mean 8-fold enlargement in area of expression relative to a control eye. Calcium recordings were obtained up to 11 degrees from the foveal center. RGC responses were comparable to the fellow control eye and showed no significant decrease over the 6 months post ILM peel, suggesting that RGC function was not compromised by the surgical procedure. In addition, we demonstrate that activity can be recorded directly from the retinal nerve fiber layer. This approach will be valuable for a range of applications in visual neuroscience including pre-clinical evaluation of retinal function, detecting vision loss, and assessing the impact of therapeutic interventions.

Macular hole: Differential diagnosis, treatment options and new guideline recommendations

Full-thickness macular holes (FTMH) usually result in apronounced reduction of visual acuity and represent one of the most frequent indications for retinal surgery. If diagnosed and treatment is initiated at an early stage, surgery has ahigh success rate with respect to both hole closure and improvement of visual acuity. Optical coherence tomography (OCT)-based staging and sizing enables an estimation of the surgical outcome. The differential diagnostic distinction from clinically similar disorders, such as lamellar macular holes, macular pseudoholes, and foveoschisis is clinically relevant as the pathogenesis, prognosis and treatment are significantly different. While vitrectomy with peeling of the inner limiting membrane (ILM) and gas tamponade is established as the standard treatment for FTMH, some aspects of treatment are handled differently between surgeons, such as the timing of surgery, the choice of endotamponade and the type and duration of postoperative positioning. For FTMH associated with vitreomacular traction, alternative treatment options in addition to vitrectomy include intravitreal ocriplasmin injection and pneumatic vitreolysis. The current clinical guidelines of the German ophthalmological societies summarize the evidence-based recommendations for diagnosis and treatment of FTMH.

Predicting perimetric defects from en face maps of retinal nerve fibre layer reflectance.

To develop criteria to predict visual hemifields with deep perimetric defects based on retinal nerve fibre layer (RNFL) reflectance, in a transparent process whose components can be assessed by independent laboratories analysing data from their own small groups. The analysis was carried out in four stages, using three independent groups of patients-30, 33 and 62 participants-with glaucoma and age-similar controls. The first stage used Group 1 to develop a criterion for RNFL reflectance images at 24, 36 or 48 μm below the inner limiting membrane (ILM). The second stage evaluated the criterion using Group 2. The third stage developed a second criterion to improve performance for Groups 1 and 2 combined. The fourth stage evaluated the second criterion with Group 3. Confidence intervals for sensitivity and specificity were then computed by combining results from all three groups. The first criterion identified all hemifields with deep defects and no hemifields from controls, using a within-eye reference for healthy RNFL. For Group 2, specificity remained high but sensitivity was reduced. The second criterion improved sensitivity by using location-specific reference values. For Group 3, sensitivity remained high but reduced specificity was found. Confidence intervals showed substantial overlap for the two criteria. We developed two criteria to identify patients with deep perimetric defects with high specificity and sensitivity. Several improvements are warranted: automated identification of the fovea-disc angle and optic disc locations, evaluation of normal variation in patterns of RNFL thickness, improved segmentation of ILM and major vasculature, reduction of within-eye variability in RNFL reflectance of healthy eyes, assessment of effects of image quality, assessment of effects of comorbidity and effectiveness of other devices.

Effect of epiretinal electrical stimulation on the glial cells in a rabbit retinal eyecup model.

We examined how pulse train electrical stimulation of the inner surface of the rabbit retina effected the resident glial cells. We used a rabbit retinal eyecup preparation model, transparent stimulus electrodes, and optical coherence tomography (OCT). The endfeet of Müller glia processes line the inner limiting membrane (ILM). To examine how epiretinal electrode stimulation affected the Müller glia, we labeled them post stimulation using antibodies against soluble glutamine synthetase (GS). After 5 min 50 Hz pulse train stimulation 30 μm from the surface, the retina was fixed, immunostained for Müller glia, and examined using confocal microscopic reconstruction. Stimulus pulse charge densities between 133-749 μC/cm2/ph were examined. High charge density stimulation (442-749 μC/cm2/ph) caused significant losses in the GS immunofluorescence of the Müller glia endfeet under the electrode. This loss of immunofluorescence was correlated with stimuli causing ILM detachment when measured using OCT. Müller cells show potassium conductances at rest that are blocked by barium ions. Using 30 msec 20 μA stimulus current pulses across the eyecup, the change in transretinal resistance was examined by adding barium to the Ringer. Barium caused little change in the transretinal resistance, suggesting under low charge density stimulus pulse conditions, the Müller cell radial conductance pathway for these stimulus currents was small. To examine how epiretinal electrode stimulation affected the microglia, we used lectin staining 0-4 h post stimulation. After stimulation at high charge densities 749 μC/cm2/ph, the microglia under the electrode appeared rounded, while the local microglia outside the electrode responded to the stimulated retina by process orientation inwards in a ring by 30 min post stimulation. Our study of glial cells in a rabbit eyecup model using transparent electrode imaging suggests that epiretinal electrical stimulation at high pulse charge densities, can injure the Müller and microglia cells lining the inner retinal surface in addition to ganglion cells.

Mechanical Disruption of the Inner Limiting Membrane In Vivo Enhances Targeting to the Inner Retina.

To evaluate the effects of mechanical disruption of the inner limiting membrane (ILM) on the ability to target interventions to the inner neurosensory retina in a rodent model. Our study used an animal model to gain insight into the normal physiology of the ILM and advances our understanding of the effects of mechanical ILM removal on the viral transduction of retinal ganglion cells and retinal ganglion cell transplantation. The ILM in the in vivo rat eye was disrupted using mechanical forces applied to the vitreoretinal interface. Immunohistology and electron microscopy were used to verify the removal of the ILM in retina flatmounts and sections. To assess the degree to which ILM disruption enhanced transvitreal access to the retina, in vivo studies involving intravitreal injections of adeno-associated virus (AAV) to transduce retinal ganglion cells (RGCs) and ex vivo studies involving co-culture of human stem cell-derived RGCs (hRGCs) on retinal explants were performed. RGC transduction efficiency and transplanted hRGC integration with retinal explants were evaluated by immunohistology of the retinas. Mechanical disruption of the ILM in the rodent eye was sufficient to remove the ILM from targeted retinal areas while preserving the underlying retinal nerve fiber layer and RGCs. Removal of the ILM enhanced the transduction efficiency of intravitreally delivered AAV threefold (1380.0 ± 290.1 vs. 442.0 ± 249.3 cells/mm2; N = 6; P = 0.034). Removal of the ILM was also sufficient to promote integration of transplanted RGCs within the inner retina. The ILM is a barrier to transvitreally delivered agents including viral vectors and cells. Mechanical removal of the ILM is sufficient to enhance access to the inner retina, improve viral transduction efficiencies of RGCs, and enhance cellular integration of transplanted RGCs with the retina.

Autologous anterior lens capsule flap and serum transplant in managing idiopathic and refractory full-thickness macular holes.

To report the results of pars plana vitrectomy (PPV) with inner limiting membrane (ILM) peeling alongside phacoemulsification and intraocular lens (IOL) implantation with autologous anterior lens capsule flap (ALCF) and autologous serum transplantation (AST) into full-thickness macular holes (FTMH) and 14% perfluoropropane (C3F8) tamponade for idiopathic and refractory FTMHs. Retrospective study involving eleven patients with idiopathic FMTHs and seven with refractory FMTHs after standard surgery with PPV, ILM peeling, and gas tamponade. All eyes underwent a 'combination procedure' of PPV with ILM peeling alongside phacoemulsification and IOL implantation with autologous ALCF and AST into the FTMH and 14% C3F8 tamponade. A face-down position for one week was recommended. The mean preoperative FMTH size was 558.95 ± 186.30 µm. Seven patients aged 64 ± 5 years had a refractory FMTH and eleven patients with a mean age of 63.72 ± 4.97 years had an idiopathic FMTH. The main BCVA improvement six months postoperatively was 0.3 ± 0.29 logMAR. Seventeen macular holes fully closed six months postoperatively, with one FTMH closure failure because of a retinal detachment. ALCF transplantation alongside AST may help to improve the closure rate and visual outcomes in both idiopathic and refractory FMTHs.

Pores of the internal limiting membrane: A common finding in vitreo-maculopathies.

To describe presence and distribution of pores of the inner limiting membrane (ILM) in eyes with vitreo-maculopathies. ILM specimens were harvested from 117 eyes of 117 patients during vitrectomy with membrane peeling from eyes with vitreomacular traction syndrome, idiopathic and secondary epiretinal gliosis, and idiopathic full-thickness macular hole (FTMH). All specimens were processed as flat-mounts for immunocytochemistry and examined by phase-contrast, interference and fluorescence microscopy. Demographic and clinical data were correlated. ILM pores were found in all vitreo-maculopathies. They were identified in 47 (40.2%) of 117 eyes being most evident with anti-laminin. In eyes with FTMH >400μm, pores were seen in more than half of all eyes. They occur as numerous and uniformly distributed defects of the flat mounted ILM with a mean diameter of 9.5 ± 2.4 µm. Edges of ILM pores are round with an irregular contour and no specific cellular pattern. Pores were distinguished from retinal vessel thinning and iatrogenic artefacts. Contrary to previous reports, ILM pores are a common finding in vitreo-maculopathies easily visible with anti-laminin staining. Further studies are needed to clarify whether their presence correlates with differences in disease progression or imaging before and after vitrectomy with ILM peeling.

English

U-Net is adequate for various biomedical image segmentation tasks. Using this in the Age-related Macular Degeneration (AMD) images would be better for segmenting only the affected region. The variant of U-Net uses residual connections. A residual link is a type of connection that allows the network to learn the residual mapping between the input and output rather than the complete mapping. This technique can help the network learn more efficiently and avoid the vanishing gradients problem. This research aims to develop a method for segmenting the retinal pigment epithelium, the Bruch’s membrane, and the Inner Limiting Membranes (ILM) in OCT scans of individuals in good health and with intermediate AMD.

Accurate C/D ratio estimation with elliptical fitting for OCT image based on joint segmentation and detection network

Proper estimation of the cup-to-disc ratio (C/D ratio) plays a significant role in ophthalmic examinations, and it is urgent to improve the efficiency of C/D ratio automatic measurement. Therefore, we propose a new method for measuring the C/D ratio of OCTs in normal subjects. Firstly, the end-to-end deep convolution network is used to segment and detect the inner limiting membrane (ILM) and the two Bruch's membrane opening (BMO) terminations. Then, we introduce an ellipse fitting technique to post-process the edge of the optic disc. Finally, the proposed method is evaluated on 41 normal subjects using the optic-disc-area scanning mode of three machines: BV1000, Topcon 3D OCT-1, and Nidek ARK-1. In addition, pairwise correlation analyses are carried out to compare the C/D ratio measurement method of BV1000 to existing commercial OCT machines as well as other state-of-the-art methods. The correlation coefficient between the C/D ratio calculated by BV1000 and the C/D ratio calculated by manual annotation is 0.84, which indicates that the proposed method has a strong correlation with the results of manual annotation by ophthalmologists. Moreover, in comparison between BV1000, Topcon and Nidek in practical screening among normal subjects, the proportion of the C/D ratio less than 0.6 calculated by BV1000 accounts for 96.34%, which is the closest to the clinical statistics among the three OCT machines. The above experimental results and analysis show that the proposed method performs well in cup and disc detection and C/D ratio measurement, and compared with the existing commercial OCT equipment, the C/D ratio measurement results are relatively close to reality, which has certain clinical application value.

Optical coherence tomography in patients with Wilson's disease.

Morphological changes of retina in patients with Wilson's disease (WD) can be found by optical coherence tomography (OCT), and such changes had significant differences between neurological forms (NWD) and hepatic forms (HWD) of WD. The aim of this study was to evaluate the relationship between morphological parameters of retina and brain magnetic resonance imaging (MRI) lesions, course of disease, type of disease, and sexuality in WD. A total of 46 WD patients and 40 health controls (HC) were recruited in this study. A total of 42 WD patients were divided into different groups according to clinical manifestations, course of disease, sexuality, and brain MRI lesions. We employed the Global Assessment Scale to assess neurological severity of WD patients. All WD patients and HC underwent retinal OCT to assess the thickness of inner limiting membrane (ILM) layer to retinal pigment epithelium layer and inner retina layer (ILM to inner plexiform layer, ILM-IPL). Compared to HWD, NWD had thinner superior parafovea zone (108.07±6.89 vs. 114.40±5.54μm, p<.01), temporal parafovea zone (97.17±6.65 vs. 103.60±4.53μm, p<.01), inferior parafovea zone (108.114±7.65 vs. 114.93±5.84μm, p<.01), and nasal parafovea zone (105.53±8.01 vs. 112.10±5.44 μm, p<.01) in inner retina layer. Course of disease influenced the retina thickness. Male patients had thinner inner retina layer compared to female patients. Our results demonstrated that WD had thinner inner retina layer compared to HC, and NWD had thinner inner retina layer compared to HWD. We speculated the thickness of inner retina layer may be a potential useful biomarker for NWD.

Postoperative complications after successful primary rhegmatogenous retinal detachment repair

BackgroundTo evaluate the incidence and risk factors for cystoid macular edema (CME) and epiretinal membrane (ERM) development after surgery for primary rhegmatogenous retinal detachment (RRD).MethodsRetrospective observational cohort study involving 62 consecutive patients with primary RRD who underwent RRD repair with either scleral buckling (SB) or pars plana vitrectomy (PPV). SB was used in young phakic patients without posterior vitreous detachment (PVD), high myopic patients, and RRD associated with either anterior or inferior retinal tears. PPV was preferred over SB in pseudophakic patients or those with media opacity and posterior breaks that precluded the SB approach. After surgery, the macular changes, including CME and ERM development, were evaluated 3 and 6 months postoperatively. Phacoemulsification and intraocular lens (IOL) implantation were performed in phakic patients where media opacity or lens bulging did not allow the surgeon to perform surgical maneuvers. The inner limiting membrane (ILM) peeling was randomly performed in the macula-off and the macula-on RRD “pending foveal detachment” subgroup.ResultsSixty-two eyes affected by RRD who underwent SB or PPV were enrolled. CME occurred in 33.3% of the PPV group regardless of the ERM formation. No CME cases were found in the SB group. Macula-off RRD increased the risk of CME by odds ratio (OR) = 4.3 times compared to macula-on RRD regardless of the surgical procedure (p = 0.04). Macula-off status increased the risk of CME of OR = 1.73 times compared to macula-on in the PPV subgroup (p = 0.4). Combined cataract surgery and PPV increased the risk of CME by OR = 3.3 times (p = 0.16) compared to PPV alone, and ILM peeling increased the risk of postoperative CME by OR = 1.8 times (p = 0.37). ERM occurred in 28% of patients who did not undergo ILM peeling, and 29.42% of those who underwent ILM peeling developed ERM (p = 0.6).ConclusionsThe risk of postoperative CME was higher in patients with macula-off than in macula-on RRD and in those with macula-off RRD who underwent PPV. The SB would be advisable in patients with RRD sparing the macula. Furthermore, despite having several advantages, the combined phacoemulsification plus IOL implantation and PPV highly increased the risk of postoperative CME.

Пилинг внутренней пограничной мембраны сетчатки в хирургическом лечении диабетического макулярного отека (2 клинических случая)

Relevance. Vitreoretinal surgery (VRS) for diabetic macular edema (DME) is the treatment of choice when combined with vitreomacular interface (VMI) anomalies. Peeling of the inner limiting membrane (ILM) of the retina in such patients is a controversial procedure. Purpose. To clinically approve new method of ILM peeling in patients with DME in combination with VMI. Material and methods. The article presents a comparative analysis of two clinical cases. The patients had similar clinical and anamnestic characteristics. In both cases, patients underwent VRS for DME with a large intraretinal cyst in the fovea in combination with epimacular fibrosis (EMF). The operation was combined with intervention for cataract (phacoemulsification with implantation of an elastic intraocular lens). Only the stages of ILM peeling were different: in the first case, the technology with the preservation of the ILM fragment in the fovea was used, in the second, a complete peeling of the ILM was performed. Results. In the course of dynamic observation for 6 months after the operation, observation, examination and, if necessary, additional treatment were carried out. Based on the results of observation and evaluation of the functional and anatomical parameters of the retina within 6 months, an improvement was noted in 1st patient and stabilization in 2nd patient. In the case of 2nd patient, a lamellar macular rupture formed at a period of 3 months, which can be regarded as a complication of the complete ILM peeling technique. Conclusion. Peeling of the ILM with preservation of the fragment in the fovea showed better functional and anatomical results compared to the complete removal of the ILM. Morphofunctional results of this method are to be investigated on the representative patient sample. Key words: diabetes mellitus, diabetic retinopathy, diabetic macular edema, vitrectomy, ILM-peeling, optical coherence tomography

Unique Optical Coherence Tomography Imaging in Spontaneous Closure of Full Thickness Macular Hole Post Laser Photocoagulation

Purpose: To study events in spontaneous full thickness macular hole (FTMH) closure following laser photocoagulation (LP). Methods: Retrospective case study of a patient of spontaneous FTMH closure documented by SD-OCT following laser. Results: A 51-year-old lady presented with FTMH and a subclinical retinal detachment (RD) in her right eye. LP for subclinical RD was done and surgery for FTMH was advised. On day of surgery, repeat SD-OCT showed spontaneous closure of FTMH with an outer retinal defect, following which surgery was abandoned. Conclusion: Spontaneous PVD induction relieves antero-posterior traction and Inner limiting membrane (ILM) micro breaks relieves tangential traction, which can result in spontaneous closure of FTMH.

Neuroprotective Effects of Human Adipose–Derived Mesenchymal Stem Cells in Oxygen-Induced Retinopathy

This study was designed to provide evidence of the neuroprotective of human adipose–derived mesenchymal stem cells (hADSCs) in oxygen-induced retinopathy (OIR). In vivo, hADSCs were intravitreally injected into OIR mice. Various assessments, including HE (histological evaluation), TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) staining, electroretinogram (ERG) analysis, and retinal flat-mount examination, were performed separately at postnatal days 15 (P15) and 17 (P17) to evaluate neurological damage and functional changes. Western blot analysis of ciliary neurotrophic factor (CNTF), glial cell line–derived neurotrophic factor (GDNF), and brain-derived neurotrophic factor (BDNF) was conducted at P17 to elucidate the neuroprotective mechanism. The P17 OIR group exhibited a significant increase in vascular endothelial cell nuclei and neovascularization that breached the ILM (inner limiting membrane) to the P17 control group. In addition, the retinal nonperfusion areas in the P17 OIR group and the number of apoptotic retinal cells in the P15 OIR group were significantly higher than in the corresponding hADSCs treatment group and control group. There was no significant thickness change in the inner nuclear layer (INL) but the outer nuclear layer (ONL) in the P17 OIR treatment group compared with the P17 OIR group. The cell density in the INL and ONL at P17 in the hADSCs treatment group was not significantly different from the OIR group. The amplitude of a-wave and b-wave in scotopic ERG analysis for the P17 OIR group was significantly lower than in the P17 hADSCs treatment group and the P17 control group. Furthermore, the latency of the a-wave and b-wave in the P17 OIR group was significantly longer than in the P17 hADSCs treatment group and the P17 control group. In addition, the expression levels of CNTF and BDNF in the P17 OIR group were statistically higher than those in the P17 control group, whereas the expression of GDNF was statistically lower in the P17 OIR group, compared with the P17 control group. The expression of CNTF and GDNF in the P17 hADSCs treatment group was statistically higher than in the P17 OIR group. However, the expression of BDNF in the P17 hADSCs treatment group was statistically lower than in the P17 OIR group. This study provides evidence for the neuroprotective effects of hADSCs in OIR.

Inner limiting membrane bridges within Bruch's membrane defects in pathological myopia.

The purpose of the study was to examine peculiarities of the inner limiting membrane (ILM) in axially elongated eyes. The histomorphometric study included human globes enucleated due to reasons such as painful secondary angle-closure glaucoma or malignant uveal melanomas. Using light microscopy, we searched for regions with ILM-specific features in association with a marked axial elongation. Out of 279 eyes (279 patients) (mean age: 61.8 ± 13.9years; axial length: 25.5 ± 3.1mm (range: 20.0-37.0mm)), two eyes (axial length: 30mm and 34mm, respectively) showed one region and two regions, respectively, characterized by ILM presence and absence of all other retinal layers, retinal pigment epithelium, Bruch´s membrane (BM) and choroid. The length of these regions, called ILM-bridges, was 1.06mm, 0.73mm, and 0.62mm, respectively. All ILM-bridges were spatially associated with a larger, underlying BM defect and with localized scleral thinning without a staphylomatous scleral configuration. The distance between the ILM-bridges and the optic disc ranged between 1.92mm and 4.21mm. In univariable analysis, ILM-bridge number increased with longer axial length (beta: 0.19; P = 0.002) and higher BM defect prevalence (beta: 0.21; P = 0.001), while in multivariable analysis, the ILM-bridges number remained to be significantly correlated only with a higher prevalence of BM defect (beta: 0.15; P = 0.048). ILM-bridges occur in eyes with pathologic myopia in spatial association with underlying, larger BM defects. They may be due to an axial elongation-associated local stretching and rupture of all other retinal layers, caused by the BM defect-related enlargement of the retinal undersurface. Future studies may explore whether these histologic observations support the notion of the ILM having a relatively high biomechanical strength against myopic stretching-associated forces.

Inner limiting membrane bridges within Bruch's membrane defects in pathological myopia

AbstractPurpose: To examine peculiarities of the inner limiting membrane (ILM) in axially elongated eyes.Methods: The histomorphometric study included human globes enucleated due to reasons such as painful secondary angle‐closure glaucoma or malignant uveal melanomas. Using light microscopy, we searched for regions with ILM‐specific features in association with a marked axial elongation.Results: Out of 279 eyes (279 patients) (mean age: 61.8 ± 13.9 years; axial length: 25.5 ± 3.1 mm (range: 20.0–37.0 mm)), two eyes (axial length: 30 mm and 34 mm, respectively) showed one region and two regions, respectively, characterized by ILM presence and absence of all other retinal layers, retinal pigment epithelium, Bruch's membrane (BM) and choroid. The length of these regions, called ILM‐bridges, was 1.06, 0.73, and 0.62 mm, respectively. All ILM‐bridges were spatially associated with a larger, underlying BM defect and with localized scleral thinning without a staphylomatous scleral configuration. The distance between the ILM‐bridges and the optic disc ranged between 1.92 and 4.21 mm. In univariable analysis, ILM‐bridge number increased with longer axial length (beta: 0.19; p = 0.002) and higher BM defect prevalence (beta: 0.21; p = 0.001), while in multivariable analysis, the ILM‐bridges number remained to be significantly correlated with a higher prevalence of BM defect (beta: 0.15; p = 0.048).Conclusions: ILM‐bridges are a hallmark of pathologic myopia and occur in spatial association with underlying, larger BM defects. ILM‐bridges may be due to a local stretching and rupture of all other retinal layers, caused by the BM defect‐related enlargement of the retinal underground, with the ILM as a basal membrane presenting the highest resistance against the stretching‐associated biomechanical force.

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

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

Vitrectomy and ILM peeling in rhesus macaque: pitfalls and tips for success.

The non-human primate (NHP) model is ideal for pre-clinical testing of novel therapies for human retinal diseases due to its similarity to the human visual system. However, intra-ocular delivery of gene therapy or cell transplantation to the retina gets hampered by the sticky vitreous body and poorly permeable inner limiting membrane (ILM) in primates. Although vitrectomy and ILM peeling are commonly performed in patients, many pitfalls exist in carrying out these procedures in the rhesus macaque, which have not been reported previously. We summarised common surgical pitfalls after performing vitrectomy and ILM peeling in four eyes of two rhesus macaques (one male and one female). We provided corresponding hands-on technical tips based on our surgical experience and literature search. Orbital CT scans were compared between adult rhesus macaques and humans. High-resolution surgical videos were recorded to demonstrate each critical surgical step. Due to size difference, poor post-operative compliance, and high-standard requirements of a controlled experiment, there were eleven common surgical pitfalls during vitrectomy and ILM peeling in rhesus macaque. Falling into these pitfalls may produce discomfort, add fatigue, cause surgical complications, or even lead to the exclusion of the NHP from an experimental group. Recognition and circumvention of these pitfalls during vitrectomy and ILM peeling in NHP are essential. By focusing on these surgical pitfalls, we can better carry out preclinical tests of novel therapies for retinal diseases in the NHP model.