Vitreous: the resplendent enigma

In vitrothree-dimensional volumetric printing of vitreous body models using decellularized extracellular matrix bioink

Hyalocytes, which are considered to originate from the monocyte/macrophage lineage, play active roles in vitreous collagen and hyaluronic acid synthesis. Obtaining a hyalocyte-compatible bioink during the 3D bioprinting of eye models is challenging. In this study, we investigated the suitability of a cartilage-decellularized extracellular matrix (dECM)-based bioink for printing a vitreous body model. Given that achieving a 3D structure and environment identical to those of the vitreous body necessitates good printability and biocompatibility, we examined the mechanical and biological properties of the developed dECM-based bioink. Furthermore, we proposed a 3D bioprinting strategy for volumetric vitreous body fabrication that supports cell viability, transparency, and self-sustainability. The construction of a 3D structure composed of bioink microfibers resulted in improved transparency and hyalocyte-like macrophage activity in volumetric vitreous mimetics, mimicking real vitreous bodies. The results indicate that our 3D structure could serve as a platform for drug testing in disease models and demonstrate that the proposed printing technology, utilizing a dECM-based bioink and volumetric vitreous body, has the potential to facilitate the development of advanced eye models for future studies on floater formation and visual disorders.

Desired properties of polymeric hydrogel vitreous substitute

Vitreous replacement is a commonly employed method for treating a range of ocular diseases, including posterior vitreous detachment, complex retinal detachment, diabetic retinopathy, macular hole, and ocular trauma. Various clinical substitutes for vitreous include air, expandable gas, silicone oil, heavy silicone oil, and balanced salt solution. However, these substitutes have drawbacks such as short retention time, cytotoxicity, high intraocular pressure, and the formation of cataracts, rendering them unsuitable for long-term treatment. Polymeric hydrogels possess the potential to serve as ideal vitreous substitutes due to their structure-mimicking to natural vitreous and adjustable mechanical properties. Replacement with hydrogels as the tamponade can help maintain the shape of the eyeball, apply pressure to the detached retina, and ensure the metabolic transport of substances without impairing vision. This literature review examines the required properties of artificial vitreous, including the optical properties, rheological properties, expansive force action, and physiological and biochemical functions of chemically and physically crosslinked hydrogels. The strategies for enhancing the biocompatibility and injectability of hydrogels are also summarized and discussed. From a clinical ophthalmology perspective, this paper presents the latest developments in vitreous replacement, providing clinicians with a comprehensive understanding of hydrogel clinical applications, which offers guidance for future design directions and methodologies for hydrogel development.

Choroidal Vascularity Index Fluctuations in Epiretinal Membranes in Vitreoretinal Surgery: Comparison Between Idiopathic and Diabetic Ones

Purpose

The aim of the study was to analyze choroidal vascularity index (CVI) fluctuations in patients with epiretinal membrane after vitreoretinal surgery, comparing idiopathic and secondary diabetic ones.

Methods

Thirty eyes suffering from idiopathic ERMs (I-ERMS; n = 15) and diabetic ERMs (D-ERMS; n = 15) were analyzed in this observational prospective study. Anatomical (central macular thickness) and functional (best-corrected visual acuity) parameters were analyzed preoperatively and at 1 and 3 months after vitrectomy. Perfusion findings regarding CVI and luminal area were also calculated.

Results

At 1 month after surgery, the luminal area and CVI significantly decreased in the I-ERMS group, whereas they were increased in the D-ERMS group. At the 3-month follow-up, the CVI tended to return to baseline values in I-ERMS and to reduce in D-ERMS, but without any statistical differences.

Conclusions

The significant change in the CVI after surgery seems to imply that the choroidal layer is affected by vitreomacular disease and can become a novel potential biomarker of predictiveness in vitreoretinal surgery.

Translational Relevance

The aim of the study was to focus on the early choroidal changes to better understand initial predictive elements of long-term functional postoperative outcomes.

3-D OCT imaging of hyalocytes in partial posterior vitreous detachment and vaso-occlusive retinal disease

Purpose

To describe the spatial distribution and morphologic characteristics of macrophage-like cells called hyalocytes in the posterior vitreous cortex of a patient with unilateral partial posterior vitreous detachment (PVD) using coronal plane en face optical coherence tomography (OCT).

Observations

A 54-year-old male with sickle cell disease (HbSC genotype) presented with a partial PVD in one eye. Rendered volumes of a slab extending from 600 μm to 3 μm anterior to the inner limiting membrane (ILM) revealed hyperreflective foci in the detached posterior vitreous cortex suspended anterior to the macula, likely representing hyalocytes. In the fellow eye without PVD, hyperreflective foci were located 3 μm anterior to the ILM. The morphology of the cells in the eye with PVD varied between a ramified state with multiple elongated processes and a more activated state characterized by a plump cell body with fewer retracted processes. In the same anatomical location, the hyperreflective foci were 10-fold more numerous in the patient with vaso-occlusive disease than in an unaffected, age-matched control.

Conclusions and Importance

Direct, non-invasive, and label-free techniques of imaging cells at the vitreoretinal interface and within the vitreous body is an emerging field. The findings from this case report suggest that coronal plane en face OCT can be used to provide a detailed and quantitative characterization of cells at the human vitreo-retinal interface in vivo. Importantly, this case report demonstrates that 3D-OCT renderings can enhance visualization of these cells in relation to the ILM, which may provide clues concerning the identity and contribution of these cells to the pathogenesis of vitreo-retinal diseases.

Hyalocyte origin, structure, and imaging

Introduction

Hyalocytes have been recognized as resident tissue macrophages of the vitreous body since the mid-19th century. Despite this, knowledge about their origin, turnover, and dynamics is limited.

Areas covered

Historically, initial studies on the origin of hyalocytes used light and electron microscopy. Modern investigations across species including rodents and humans will be described. Novel imaging is now available to study human hyalocytes in vivo. The shared ontogeny with retinal microglia and their eventual interdependence as well as differences will be discussed.

Expert opinion

Owing to a common origin as myeloid cells, hyalocytes and retinal microglia have similarities, but hyalocytes appear to be distinct as resident macrophages of the vitreous body.

Clinical Characteristics of Lamellar Macular Hole Subtypes: Degenerative and Tractional

Purpose

To analyze clinical parameters of two subtypes of lamellar macular hole (LMH): degenerative and tractional.

Methods

This retrospective chart review study included patients monitored for more than 6 months after the initial diagnosis of LMH from January 2011 to January 2018. LMH was classified in two subtypes: degenerative and tractional. The following parameters between both subtypes were assessed: central subfield thickness (CST), maximum inner diameter (MID), maximum outer diameter (MOD), MID/MOD ratio, inner and outer segment (IS/OS) junction disruption, residual retinal thickness (RRT), subfoveal choroidal thickness (SFCT), best-corrected visual acuity (BCVA), anatomical progression rate, and percentage of patients undergoing surgery.

Results

This study included 51 eyes with a mean follow-up period of 18.94 months: 33 eyes with tractional LMH and 18 eyes with degenerative LMH. MID was not significantly different between both subtypes but MOD was significantly greater in tractional LMH than degenerative types (tractional, 1131.6 μm; degenerative, 708.9 μm; p < 0.001). The MID were significantly increased in degenerative eyes, while the tractional eyes featured a significant increase in MOD. BCVA was not significantly different between both subtypes at baseline and the last follow-up. Epiretinal membrane presence was significantly different between the two subtypes (tractional, 96.9%; degenerative, 22.2%; p < 0.001). Ellipsoid defect and rate of receiving surgery were not significantly different between both subtypes. The anatomical progression rate in tractional eyes (81.8%) was significantly higher than that of degenerative LMH (27.7%) (p = 0.010). The SFCT was correlated to anatomical progression in the tractional LMH (correlation coefficient = 0.351, p = 0.049) but not in the degenerative LMH. During the follow-up period, 4 eyes (22.2%) of the degenerative LMH and 11 eyes (33.3%) of the tractional LMH underwent surgery.

Conclusions

We found that greater SFCT at baseline was correlated to anatomical progression of tractional LMH. Therefore, it is expected that SFCT could be used as a biomarker to predict anatomical progression in tractional LMH.

REVISED PREDICTIVE BIOMARKER FOR OCRIPLASMIN THERAPY IN VITREOMACULAR TRACTION DISORDERS

PURPOSE

To determine a statistically optimal limit of adhesion size in vitreomacular traction (VMT) syndrome for ocriplasmin treatment.

METHODS

In this retrospective, consecutive, interventional study, we included 106 patients treated with ocriplasmin injection because of VMT between July 2013 and January 2018. A univariate and multivariate risk analysis was performed with grouped factors and continuous factors. We used a receiver operating characteristic curve to measure the prognostic relevance of each continuous factor for therapy success and determined the statistically optimal cutoff value at which specificity and sensitivity are simultaneously maximized.

RESULTS

Among the grouped factors, only a phakic lens status showed a highly significant positive influence on the resolution of the VMT. For the continuous factors, only the adhesion diameter before injection was a good predictor of anatomical success. The statistically optimal threshold value for the adhesion size was calculated to be 480 µm. Eyes below this limit had a 6.84-fold better chance of VMT resolution compared with eyes with a larger adhesion diameter.

CONCLUSION

The threshold value of the VMT diameter for ocriplasmin therapy could be statistically defined as 480 µm and may thus be a new quantitative biomarker to predict treatment success.

Ocriplasmin for treatment of vitreomacular traction and macular hole: A systematic literature review and individual participant data meta-analysis of randomized, controlled, double-masked trials

Ocriplasmin is used to treat vitreomacular traction (VMT), with or without full-thickness macular hole (MH). We systematically reviewed the evidence on ocriplasmin's effect on vitreomacular adhesion resolution (VMAR), MH closure, vitrectomy, and best-corrected visual acuity (BCVA) and investigated the effect of baseline covariates on outcome. We applied individual participant data meta-analyses to the entire population and to subgroups defined by MH or epiretinal membrane (ERM) presence. Safety data were pooled and tabulated. Five randomized controlled trials (1,067 participants) were included. Six months after treatment, ocriplasmin achieved higher rates of VMAR and MH closure versus control, lowered vitrectomy odds, and increased the likelihood of a ≥10-letter BCVA increase. VMAR rates were lower when ERM, broad VMA (> 1500 µm), diabetic retinopathy, or pseudophakia were present and higher in younger participants, women, and eyes with MHs. Ocriplasmin-treated participants experienced more short-term visual impairment that was not predictive of final BCVA, as well as vitreous floaters, photopsia, photophobia, eye pain, blurred vision, and dyschromatopsia. The most common serious adverse events for ocriplasmin and control, respectively, were MH progression (22.5%, 17.3%), new MH (1.5%, 3.4%) and retinal detachment (0.8%, 1.2%). Ocriplasmin promotes VMAR and MH closure. Transient visual phenomena are not uncommon.

Effectiveness of ocriplasmin in real-world settings: A systematic literature review, meta-analysis, and comparison with randomized trials

Purpose

Effectiveness of ocriplasmin for vitreomacular traction (VMT) varies depending on the presence of common ocular conditions and patient selection criteria. We carried out a systematic literature review and meta‐analysis of ocriplasmin studies conducted in real‐world settings (RWS) and compared outcomes with those from randomized controlled trials (RCTs).

Methods

We included prospective and retrospective studies from RWS documenting effectiveness of ocriplasmin in patients with VMT with or without MH, and RCTs of ocriplasmin versus control. Key end‐points were vitreomacular adhesion resolution (VMAR), nonsurgical MH closure, need for vitrectomy and safety. We conducted meta‐regression on pooled results to evaluate effects of baseline covariates and study design on outcomes.

Results

Thirty RWS (2402 patients) and 5 RCTs (737 patients) were included epiretinal membrane (ERM) and broad VMA were more prevalent in RCTs. Primary VMAR, vitrectomy and MH closure rates were comparable between RWS and RCTs. Rates of nsVMAR were significantly higher in RWS than RCTs (odds ratio 1.66; 95% confidence interval [CI]: 1.18–2.34). nsVMAR rates were inversely associated with ERM prevalence (odds ratio 0.20; 95% CI: 0.08–0.51). Compared with the recent OASIS trial, RWS reported a higher incidence of new/worsening subretinal fluid cases and less photophobia, photopsia, vitreous floaters, electroretinogram abnormalities and MH progression.

Conclusions

Ocriplasmin was significantly more effective in achieving nsVMAR in RWS than in RCTs. Lower ERM prevalence in RWS was the single significant explanatory variable for this difference. Conclusions on ocriplasmin safety in RWS are limited due to inconsistent reporting.

Expression of Lymphatic Markers in the Berger's Space and Bursa Premacularis

We previously reported that the bursa premacularis (BPM), a peculiar vitreous structure located above the macula, contains numerous cells expressing markers of lymphatic endothelial cells, such as podoplanin and LYVE-1. Herein, we examined the expression of lymphatic markers in the Berger’s space (BS), BPM, and vitreous core (VC). BS, BPM, and VC specimens were selectively collected in macular hole and epiretinal membrane patients during vitrectomy and were then immunostained with antibodies for podoplanin, LYVE-1, and fibrillin-1 and -2. By visualization using triamcinolone acetonide, the BS was recognized as a sac-like structure with a septum located behind the lens as well as BPM. Those tissues adhered to the lens or retina in a circular manner by means of a ligament-like structure. Immunostaining showed intense expression of podoplanin and LYVE-1 in the BS. Both BS and BPM stained strongly positive for fibrillin-1 and -2. The VC was faintly stained with antibodies for those lymph-node markers. Our findings indicate that both BS and BPM possibly belong to the lymphatic system, such as lymph nodes, draining excess fluid and waste products into lymphatic vessels in the dura mater of the optic nerve and the ciliary body, respectively, via intravitreal canals.

Prognostic Factors Associated with Ocriplasmin Efficacy for the Treatment of Symptomatic Vitreomacular Adhesion and Full-thickness Macular Hole: Analysis from Four Studies

Purpose

To assess the effect of patient baseline characteristics on the efficacy of ocriplasmin treatment for symptomatic vitreomacular adhesion (VMA) with full-thickness macular hole (FTMH) from phase 3/4 studies.

Methods

Patients with symptomatic VMA and FTMH at baseline and receiving ocriplasmin treatment 125 μg were pooled from the MIVI-TRUST, OASIS, and ORBIT studies. Multivariable logistic regression analysis was used to evaluate whether patient baseline characteristics were predictors of having VMA resolution by Day 28 and FTMH closure by Month 6.

Results

Two hundred and seventy-four patients receiving ocriplasmin treatment were assessed. Overall, 22.6% (62/274) of the patients experienced both VMA resolution by Day 28 and non-surgical FTMH closure by Month 6. Patients with FTMH ≤250 µm at baseline had a significantly higher success rate compared to those with FTMH >400 µm (29.9% [41/137] vs 2.2% [1/48]; P = 0.009). In patients with VMA resolution by Day 28, both small FTMH size (P = 0.001) and FTMH width at RPE (P = 0.012) were significantly associated with a higher FTMH closure rate. Patients with VMA resolution had higher rates of FTMH closure. Previously identified baseline predictive factors, including age, lens status, or presence of epiretinal membrane (ERM) were not found to be predictive of both VMA release and FTMH closure.

Conclusion

The analysis revealed that FMTH ≤250 µm was the only factor predictive for achieving both pharmacological VMA resolution by Day 28 and nonsurgical FTMH closure by Month 6; neither lens status or presence of ERM, previously identified baseline characteristics favoring VMA resolution, showed statistically significant predictive power for both outcomes.

Is choroidal vascularity index a useful marker in different stages of idiopathic epiretinal membranes?

BACKGROUND

This study aims to evaluate the choroidal vascularity index in patients with idiopathic epiretinal membrane at different stages.

METHODS

This prospective study included 125 eyes of 125 patients with idiopathic epiretinal membrane and 62 eyes of 62 healthy control subjects. In this study, epiretinal membrane stages were defined based on the spectral-domain optical coherence tomography staging system. The choroidal vascularity index was measured as the ratio of the luminal area to the stromal area in the central 1500 μm after binarization on enhanced depth imaging optical coherence tomography images. Data on epiretinal membrane stages, choroidal vascularity index, and best-corrected visual acuity were noted.

RESULTS

Of 125 eyes with epiretinal membrane, 38 (30.4 %) had stage 1, 32 (25.6 %) had stage 2, and 55 (44 %) had stage 3 disease. Visual acuity was better in eyes with stage 1 or 2 epiretinal membrane than those with stage 3 epiretinal membrane (p < 0.001). The mean choroidal vascularity index was 2.29 ± 1.02 in the control, 2.23 ± 0.98 in the stage 1 epiretinal membrane, 2.22 ± 0.91 in the stage 2 epiretinal membrane, and 2.23 ± 1.11 in the stage 3 epiretinal membrane group. There was no significant difference between epiretinal membrane subgroups and the control group regarding the choroidal vascularity index (p = 0.81).

CONCLUSION

From the results obtained in the present study, the choroidal vascularity index was not effected by either the development or the progression of idiopathic epiretinal membrane.

Efficacy and safety of glecaprevir/pibrentasvir in patients with HCV genotype 5/6: An integrated analysis of phase 2/3 studies

BACKGROUND & AIMS

Hepatitis C virus (HCV) has high genetic diversity with six major genotypes (GT) GT1-6 and global distribution. HCV GT5 and 6 are rare with < 10 million people infected worldwide. Data on direct-acting antiviral use in these rare HCV genotypes are limited. The study aimed to evaluate the efficacy and safety of glecaprevir/pibrentasvir (G/P) in a pooled analysis of phase 2/3 trials in HCV GT5 or 6-infected patients without cirrhosis or with compensated cirrhosis.

METHODS

Patients with chronic HCV GT5 or 6 infection received oral G/P (300 mg/120 mg) once daily for 8 or 12 weeks. The primary efficacy endpoint was sustained virological response at post-treatment week 12 (SVR12) in the intention-to-treat population.

RESULTS

One hundred eighty-one patients were evaluated; 56 with HCV GT5 and 125 with HCV GT6. The majority were treatment-naïve (88%) and non-cirrhotic (85%). Overall SVR12 rate with 8- or 12-week G/P treatment was 98% (178/181). Eight-week treatment with G/P yielded SVR12 rates of 95% (21/22) in HCV GT5- and 99% (69/70) in HCV GT6-infected non-cirrhotic patients. Eight- and 12-week treatment of patients with compensated cirrhosis achieved SVR12 rates of 100% (10/10) and 94% (17/18) respectively. The G/P regimen was well-tolerated; 3% (6/181) Grade 3 or higher adverse events, and no serious adverse events were attributed to G/P or led to study drug discontinuation.

CONCLUSIONS

This integrated dataset demonstrates a high SVR12 rate following 8-week G/P treatment in patients with HCV GT5 (96%) or GT6 (99%) infection without cirrhosis or with compensated cirrhosis.

Vitreous and Vision Degrading Myodesopsia

Macromolecules comprise only 2% of vitreous, yet are responsible for its gel state, transparency, and physiologic function(s) within the eye. Myopia and aging alter collagen and hyaluronan association causing concurrent gel liquefaction and fibrous degeneration. The resulting vitreous opacities and collapse of the vitreous body during posterior vitreous detachment are the most common causes for the visual phenomenon of vitreous floaters. Previously considered innocuous, the vitreous opacities that cause floaters sometimes impact vision by profoundly degrading contrast sensitivity function and impairing quality-of-life. While many people adapt to vitreous floaters, clinically significant cases can be diagnosed with Vision Degrading Myodesopsia based upon echographic assessment of vitreous structure and by measuring contrast sensitivity function. Perhaps due to the ubiquity of floaters, the medical profession has to date largely ignored the plight of those with Vision Degrading Myodesopsia. Improved diagnostics will enable better disease staging and more accurate identification of severe cases that merit therapy. YAG laser treatments may occasionally be slightly effective, but vitrectomy is currently the definitive cure. Future developments will usher in more informative diagnostic approaches as well as safer and more effective therapeutic strategies. Improved laser treatments, new pharmacotherapies, and possibly non-invasive optical corrections are exciting new approaches to pursue. Ultimately, enhanced understanding of the underlying pathogenesis of Vision Degrading Myodesopsia should result in prevention, the ultimate goal of modern Medicine.

Vitreous Antioxidants, Degeneration, and Vitreo-Retinopathy: Exploring the Links

The transparent vitreous body, which occupies about 80% of the eye’s volume, is laden with numerous enzymatic and non-enzymatic antioxidants that could protect the eye from oxidative stress and disease. Aging is associated with degeneration of vitreous structure as well as a reduction in its antioxidant capacity. A growing body of evidence suggests these age-related changes may be the precursor of numerous oxidative stress-induced vitreo-retinopathies, including vision degrading myodesopsia, the clinically significant entoptic phenomena that can result from advanced vitreous degeneration. Adequate intravitreal antioxidant levels may be protective against vitreous degeneration, possibly preventing and even improving vision degrading myodesopsia as well as mitigating various other vitreo-retinopathies. The present article is, therefore, a review of the different antioxidant molecules within vitreous and the inter-relationships between vitreous antioxidant capacity and degeneration.

Choroidal vascularity index changes after vitreomacular surgery

PURPOSE

To study the structural changes in the choroid using swept-source (SS) optical coherence tomography (OCT), a tool for the choroidal vascularity index (CVI) following epiretinal membrane removal.

METHODS

Fifty-two eyes of 26 patients were evaluated in this prospective, single-centre, observational study. Twenty-six eyes underwent vitrectomy for epiretinal membrane removal (VT-group), and the control group consisted of 26 corresponding fellow eyes (F-group). All patients were evaluated at baseline, 30 and 90 days postsurgery. Using a modified image binarization algorithm for SS-OCT scans, the subfoveal choroidal area was segmented into the luminal and stromal areas, and the CVI was measured by calculating the proportion of the luminal area (LA) to the cross-sectional choroid area.

RESULTS

The mean CVI in the VT-group was 63.86 ± 4.04% at the baseline, 62.45 ± 4.21% at 30 days postsurgery and 61.06 ± 3.79% at 90 days (p < 0.001). The F-group had a mean CVI of 61.12 ± 2.29% at the baseline, 60.91 ± 2.25% at 30 days postsurgery and 61.05 ± 2.28% at 90 days (p = 0.29).

CONCLUSION

The CVI decreases following epiretinal membrane removal when compared to the fellow eyes, which suggests structural changes in the vascular layers of the choroid. The implication of these results may be that secondary inflammation resulting from mechanical traction induces choroidal thickness by way of increased vascularization of the choroid.

Changes in choroidal thickness after vitrectomy for epiretinal membrane combined with vitreomacular traction

PURPOSE

To compare choroidal thickness after vitrectomy between epiretinal membrane (ERM) with and without vitreomacular traction (VMT).

METHODS

In this retrospective study, 228 consecutive participants with ERM who underwent vitrectomy were categorized into two groups according to the presence of VMT on spectral domain-optical coherence tomography: VMT group (ERM with VMT, n = 21) and non-VMT group (ERM without VMT, n = 207). The primary outcome was the mean subfoveal choroidal thickness (SFCT) at baseline, and at 3 and 6 months postsurgery.

RESULTS

At baseline, the prevalence of VMT in eyes with ERM was 9.6% (21/228), and mean SFCT was greater in the VMT than in the non-VMT group (270.3 ± 93.4 vs. 223.7 ± 82.1 μm; p = 0.015). After surgery, mean SFCT decreased in the VMT group (241.7 ± 92.3 μm at 3 months and 228.8 ± 86.4 μm at 6 months; p < 0.001), but remained unchanged in the non-VMT group (223.6 ± 78.9 μm at 3 months and 223.3 ± 82.6 μm at 6 months; p = 0.696). There were no differences in mean SFCT between the groups at 3 and 6 months after surgery (p = 0.339 and p = 0.772, respectively).

CONCLUSION

Choroidal thickness was greater in ERM eyes with than without VMT possibly due to direct anteroposterior traction on the retina and choroid, increased vascular endothelial growth factor associated with stress on retinal pigment epithelial cells and inflammation. After vitrectomy, mean SFCT reduced in the eyes with VMT, but not in those without VMT.

Nd:YAG laser vitreolysis versus pars plana vitrectomy for vitreous floaters

BACKGROUND

The vitreous is the clear jelly of the eye and contains fine strands of proteins. Throughout life the composition of this vitreous changes, which causes the protein strands in it to bundle together and scatter light before it reaches the retina. Individuals perceive the shadows cast by these protein bundles as 'floaters'. Some people are so bothered by floaters that treatment is required to control their symptoms. Two major interventions for floaters include Nd:YAG laser vitreolysis and vitrectomy. Nd:YAG laser vitreolysis involves using laser energy to fragment the vitreous opacities via a non-invasive approach. Vitrectomy involves the surgical replacement of the patient's vitreous (including the symptomatic vitreous floaters) with an inert and translucent balanced salt solution, through small openings in the pars plana.

OBJECTIVES

To compare the effectiveness and safety of Nd:YAG laser vitreolysis to pars plana vitrectomy for symptomatic vitreous floaters.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Trials Register) (2016, Issue 12), MEDLINE Ovid (1946 to 17 January 2017), Embase Ovid (1947 to 17 January 2017), LILACS (Latin American and Caribbean Health Sciences Literature Database) (1982 to 17 January 2017), the ISRCTN registry (www.isrctn.com/editAdvancedSearch); searched 17 January 2017, ClinicalTrials.gov (www.clinicaltrials.gov); searched 17 January 2017 and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en); searched 17 January 2017. We did not use any date or language restrictions in the electronic searches for trials. We also searched conference proceedings to identify additional studies.

SELECTION CRITERIA

We included only randomised controlled trials (RCTs) that compared Nd:YAG laser vitreolysis to pars plana vitrectomy for treatment of symptomatic floaters.

DATA COLLECTION AND ANALYSIS

We planned to use methods recommended by Cochrane. The primary outcome we planned to measure was change in vision-related quality of life from baseline to 12 months, as determined by a vision-related quality of life questionnaire. The secondary outcomes we planned to measure were best corrected logMAR or Snellen visual acuity at 12 months for the treated eye(s) and costs. Adverse outcomes we planned to record were the occurrence of sight-threatening complications by 12 months (asymptomatic retinal tears, symptomatic retinal tears, retinal detachment, cataract formation, and endophthalmitis).

MAIN RESULTS

No studies met the inclusion criteria of this review.

AUTHORS' CONCLUSIONS

There are currently no RCTs that compare Nd:YAG laser vitreolysis with pars plana vitrectomy for the treatment of symptomatic floaters. Properly designed RCTs are needed to evaluate the treatment outcomes from the interventions described. We recommend future studies randomise participants to either a Nd:YAG laser vitreolysis group or a vitrectomy group, with participants in each group assigned to either receive treatment or a sham intervention. Future studies should follow participants at six months and 12 months after the intervention. Also they should use best corrected visual acuity (BCVA) using an Early Treatment of Diabetic Retinopathy Study (ETDRS) chart read at 4 metres, vision-related quality of life (VRQOL), and adverse outcomes as the outcome measures of the trial.

The diffusion dynamics of PEGylated liposomes in the intact vitreous of the ex vivo porcine eye: A fluorescence correlation spectroscopy and biodistribution study

The diffusion dynamics of nanocarriers in the vitreous and the influence of nanocarrier physicochemical properties on these dynamics is an important aspect of the efficacy of intravitreal administered nanomedicines for the treatment of posterior segment eye diseases. Here we use fluorescence correlation spectroscopy (FCS) to determine liposome diffusion coefficients in the intact vitreous (D_Vit) of ex vivo porcine eyes using a modified Miyake-Apple technique to minimize the disruption of the vitreous fine structure. We chose to investigate whether the zeta potential of polyethylene glycol functionalized (i.e. PEGylated) liposomes altered liposome in situ diffusion dynamics in the vitreous. Non-PEGylated cationic nanocarriers have previously shown little to no diffusion in the vitreous, whilst neutral and anionic have shown diffusion. The liposomes investigated had diameters below 150nm and zeta potentials ranging from -20 to +12mV. We observed that PEGylated cationic liposomes had significantly lower D_Vit values (1.14μm²s^-1) than PEGylated neutral and anionic liposomes (2.78 and 2.87μm²s^-1). However, PEGylated cationic liposomes had a similar biodistribution profile across the vitreous to the other systems. These results show that PEGylated cationic liposomes with limited cationic charge can diffuse across the vitreous and indicate that the vitreous as a barrier to nanocarriers (Ø<500nm) is more complicated than simply an electrostatic barrier as previously suggested.

IMAGING AND MEASUREMENT OF THE PRERETINAL SPACE IN VITREOMACULAR ADHESION AND VITREOMACULAR TRACTION BY A NEW SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY ANALYSIS

PURPOSE

To evaluate a new method for volumetric imaging of the preretinal space (also known as the subhyaloid, subcortical, or retrocortical space) and investigate differences in preretinal space volume in vitreomacular adhesion (VMA) and vitreomacular traction (VMT).

METHODS

Nine patients with VMA and 13 with VMT were prospectively evaluated. Automatic inner limiting membrane line segmentation, which exploits graph search theory implementation, and posterior cortical vitreous line segmentation were performed on 141 horizontal spectral domain optical coherence tomography B-scans per patient. Vertical distances (depths) between the posterior cortical vitreous and inner limiting membrane lines were calculated for each optical coherence tomography B-scan acquired. The derived distances were merged and visualized as a color depth map that represented the preretinal space between the posterior surface of the hyaloid and the anterior surface of the retina. The early treatment d retinopathy study macular map was overlaid onto final virtual maps, and preretinal space volumes were calculated for each early treatment diabetic retinopathy study map sector.

RESULTS

Volumetric maps representing preretinal space volumes were created for each patient in the VMA and VMT groups. Preretinal space volumes were larger in all early treatment diabetic retinopathy study map macular regions in the VMT group compared with those in the VMA group. The differences reached statistical significance in all early treatment diabetic retinopathy study sectors, except for the superior outer macula and temporal outer macula where significance values were P = 0.05 and P = 0.08, respectively. Overall, the relative differences in preretinal space volumes between the VMT and VMA groups varied from 2.7 to 4.3 in inner regions and 1.8 to 2.9 in outer regions.

CONCLUSION

Our study provides evidence of significant differences in preretinal space volume between eyes with VMA and those with VMT. This may be useful not only in the investigation of preretinal space properties in VMA and VMT, but also in other conditions, such as age-related macular degeneration, diabetic retinopathy, and central retinal vein occlusion.

Effects of Vitreomacular Adhesion on Age-Related Macular Degeneration

Herein, we review the association between vitreomacular adhesion (VMA) and neovascular age-related macular degeneration (AMD). Meta-analyses have shown that eyes with neovascular AMD are twice as likely to have VMA as normal eyes. VMA in neovascular AMD may induce inflammation, macular traction, decrease in oxygenation, sequestering of vascular endothelial growth factor (VEGF), and other cytokines or may directly stimulate VEGF production. VMA may also interfere with the treatment effects of anti-VEGF therapy, which is the standard treatment for neovascular AMD, and releasing VMA can improve the treatment response to anti-VEGF treatment in neovascular AMD. We also reviewed currently available methods of relieving VMA.

Retinal Changes Induced by Epiretinal Tangential Forces

Two kinds of forces are active in vitreoretinal traction diseases: tangential and anterior-posterior forces. However, tangential forces are less characterized and classified in literature compared to the anterior-posterior ones. Tangential epiretinal forces are mainly due to anomalous posterior vitreous detachment (PVD), vitreoschisis, vitreopapillary adhesion (VPA), and epiretinal membranes (ERMs). Anomalous PVD plays a key role in the formation of the tangential vectorial forces on the retinal surface as consequence of gel liquefaction (synchysis) without sufficient and fast vitreous dehiscence at the vitreoretinal interface. The anomalous and persistent adherence of the posterior hyaloid to the retina can lead to vitreomacular/vitreopapillary adhesion or to a formation of avascular fibrocellular tissue (ERM) resulting from the proliferation and transdifferentiation of hyalocytes resident in the cortical vitreous remnants after vitreoschisis. The right interpretation of the forces involved in the epiretinal tangential tractions helps in a better definition of diagnosis, progression, prognosis, and surgical outcomes of vitreomacular interfaces.

Evolution of vitreomacular adhesion to acute vitreofoveal separation with special emphasis on a traction-induced foveal pathology. A prospective study of spectral-domain optical coherence tomography

PURPOSE

To investigate the evolution of vitreomacular adhesion (VMA) to acute vitreofoveal separation with particular emphasis on cases involving the underlying fovea.

METHODS

In this observational case series, of 192 cases in the VMA stage, 51 progressed to acute vitreofoveal separation; this subgroup was divided into those with normal separation (Group I) and those with co-existing macular findings (Group II). All patients were examined using spectral domain-optical coherence tomography (SD-OCT) at regular three-month intervals. We recorded the best-corrected visual acuity (BCVA), the vitreomacular angle of the VMA (nasally and temporally), the horizontal diameter of the VMA, the macular thickness, the integrity of the photoreceptor layer and of the external limiting membrane. The Amsler grid test was used in the intermediate examinations in cases where patients developed symptoms.

RESULTS

Out of the 51 cases in the VMA stage, 45 (88.2%) progressed to normal spontaneous vitreofoveal separation, while six (11.8%) developed findings of the fovea, such as macular thinning (two cases), an anomalous foveal contour (two cases), a macular tissue defect (one case) and vitreous separation from only the temporal side of the VMA in one case. Foveal findings were the same during the follow-up period in all but one case in which improvement was noted. Differences in BCVA between baseline measurements, those made immediately after vitreofoveal separation, and those made during final examination were not statistically significant. For the whole sample of our study (51 cases), the mean observation time at the VMA stage was 21.8 ±10.6 months, while the mean follow-up time after vitreofoveal separation was 9.7 ±4.9 months. In cases that developed incidents from the fovea, the mean observation time from the baseline to the last examination before vitreofoveal separation was 16.5 ±11.2 months and the mean follow-up time from the diagnosis of vitreofoveal separation to the final examination was 8.5 ±4.4 months.

CONCLUSIONS

VMA, excepting its progression to vitreomacular traction or spontaneous release, in a subset of patients can also cause findings associated with the fovea, concomitantly with vitreofoveal separation. Vitreofoveal separation can induce unilateral anatomic distortion of the fovea accompanied by symptoms, such as metamorphopsia or micropsia.

Oct-based interpretation of the vitreomacular interface and indications for pharmacologic vitreolysis

PURPOSE

To review the role of optical coherence tomography (OCT) in diagnosis and management of vitreomacular disease and the impact of OCT on potential uses of ocriplasmin, a new pharmacologic vitreolysis agent recently approved by the U.S. Food and Drug Administration for the treatment of symptomatic vitreomacular adhesion.

METHODS

Analysis of current literature regarding OCT in diagnosis and management of vitreomacular interface disease.

RESULTS

Posterior vitreous detachment is typically a nonpathologic age-related event. Anomalous posterior vitreous detachment emerges when the vitreous cortex fails to cleanly detach from the macula, optic nerve, or other adherent sites. Focal vitreomacular adhesion is a nonpathologic anatomical designation associated with perifoveal posterior vitreous detachment but normal retinal morphology on OCT. Vitreomacular traction is a pathologic consequence of persistent vitreous attachment with structural disturbance of the macular retina visible on OCT. Full-thickness macular holes are foveal defects continuous through all retinal layers to the retinal pigment epithelium. Vitreomacular traction and macular hole with focal vitreomacular adhesion are indications for pharmacologic vitreolysis.

CONCLUSION

Noninvasive high-resolution OCT imaging has transformed the understanding of vitreomacular interface disease. Careful evaluation of the vitreomacular interface with OCT has increased in importance with the introduction of ocriplasmin for vitreomacular adhesion associated with symptomatic anatomical retinal changes.

The International Vitreomacular Traction Study Group classification of vitreomacular adhesion, traction, and macular hole

OBJECTIVE

The International Vitreomacular Traction Study (IVTS) Group was convened to develop an optical coherence tomography (OCT)-based anatomic classification system for diseases of the vitreomacular interface (VMI).

DESIGN

The IVTS applied their clinical experience, after reviewing the relevant literature, to support the development of a strictly anatomic OCT-based classification system.

PARTICIPANTS

A panel of vitreoretinal disease experts was the foundation of the International Classification System.

METHODS

Before the meeting, panel participants were asked to review 11 articles and to complete 3 questionnaires. The articles were preselected based on searches for comprehensive reviews covering diseases of the VMI. Responses to questionnaires and the group's opinions on definitions specified in the literature were used to guide the discussion.

MAIN OUTCOME MEASURES

Optical coherence tomography-based anatomic definitions and classification of vitreomacular adhesion, vitreomacular traction (VMT), and macular hole.

RESULTS

Vitreomacular adhesion is defined as perifoveal vitreous separation with remaining vitreomacular attachment and unperturbed foveal morphologic features. It is an OCT finding that is almost always the result of normal vitreous aging, which may lead to pathologic conditions. Vitreomacular traction is characterized by anomalous posterior vitreous detachment accompanied by anatomic distortion of the fovea, which may include pseudocysts, macular schisis, cystoid macular edema, and subretinal fluid. Vitreomacular traction can be subclassified by the diameter of vitreous attachment to the macular surface as measured by OCT, with attachment of 1500 μm or less defined as focal and attachment of more than 1500 μm as broad. When associated with other macular disease, VMT is classified as concurrent. Full-thickness macular hole (FTMH) is defined as a foveal lesion with interruption of all retinal layers from the internal limiting membrane to the retinal pigment epithelium. Full-thickness macular hole is primary if caused by vitreous traction or secondary if directly the result of pathologic characteristics other than VMT. Full-thickness macular hole is subclassified by size of the hole as determined by OCT and the presence or absence of VMT.

CONCLUSIONS

This classification system will support systematic diagnosis and management by creating a clinically applicable system that is predictive of therapeutic outcomes and is useful for the execution and analysis of clinical studies.

Evaluation of a posterior vitreous detachment: a comparison of biomicroscopy, B-scan ultrasonography and optical coherence tomography to surgical findings with chromodissection

PURPOSE

To find the most reliable and efficient noninvasive technique to clinically detect a posterior vitreous detachment.

METHODS

In a prospective study of 30 eyes in 30 patients with macular pucker or macular hole formation, the posterior vitreous cortex was examined 1 day prior to a scheduled vitrectomy. Three independent investigators classified the posterior vitreous cortex of each eye as 'attached' or 'detached' via slit-lamp biomicroscopy (BM), 10-MHz B-scan ultrasonography (I³ Innovative Imaging Inc.), and optical coherence tomography [OCT III Stratus(®) (Carl Zeiss Meditec Inc.) and RTVue-100 OCT (Optovue Corp.)]. These preoperative findings were then compared during a triamcinolone acetonide-assisted vitrectomy 1 day later.

RESULTS

Triamcinolone acetonide-assisted vitrectomy showed in 60% a posterior vitreous detachment and in 40% an attached posterior vitreous cortex. Preoperatively conducted B-scan ultrasonography and BM revealed the highest, correct evaluation of the posterior vitreous status. The prediction of the OCT was confirmed intraoperatively in 12.5%. In all other cases, the evaluation by OCT was not possible or was inadequate.

CONCLUSION

The prognostic most reliable but investigator-dependent methods to clinically detect whether the posterior vitreous cortex is detached are B-scan ultrasonography and BM. The objective technique of the high-resolution, two-dimensional time-domain OCT allows only in a few cases a clear differentiation of preretinal structures.

Residual cellular proliferation on the internal limiting membrane in macular pucker surgery

PURPOSE

To provide pathology data on the completeness of epiretinal membrane (ERM) removal with and without internal limiting membrane (ILM) peeling.

METHODS

Twenty-two patients with idiopathic ERM formation underwent vitrectomy with ERM removal and subsequent staining of the vitreomacular interface with brilliant blue. If the ILM was still present after ERM removal, it was peeled off. Both ERM and ILM specimens were harvested in different containers and prepared for flat-mount phase-contrast and interference microscopy, immunocytochemistry, and transmission electron microscopy.

RESULTS

In 14 patients (64%), the ILM was still present at the macula after ERM removal. On average, 20% (range, 2-51%) of the total cell count was left behind at the ILM if the ERM was removed only. There were mainly glial cells on the ILM, and few hyalocytes. In nine eyes, the cells were forming cell clusters. In 8 patients (36%), both ERM and ILM were removed together. Electron microscopy showed cellular proliferation directly attached to the ILM in these eyes, whereas in the sequentially peeled group, there was collagen interposed between the ERM and the ILM. Surgical ERM removal resulted in splitting of the vitreous cortex in these eyes, leaving the ILM with residual cells behind.

CONCLUSION

Simple ERM removal results in sufficient separation of fibrocellular tissue in one third of cases, only. In 2 of 3 patients with idiopathic ERM, the vitreous cortex splits when the ERM is removed, leaving an average of 20% of the total cell count behind on the ILM. As these cells are capable of proliferation and causing ERM recurrence, staining of the ILM with subsequent removal seems beneficial in macular pucker surgery.

Vitreous substitutes: a comprehensive review

Vitreoretinal disorders constitute a significant portion of treatable ocular disease. Advances in vitreoretinal surgery have included the development and characterization of suitable substitutes for the vitreous. Air, balanced salt solutions, perfluorocarbons, expansile gases, and silicone oil serve integral roles in modern vitreoretinal surgery. Vitreous substitutes vary widely in their properties, serve different clinical functions, and present different shortcomings. Permanent vitreous replacement has been attempted with collagen, hyaluronic acid, hydroxypropylmethylcellulose, and natural hydrogel polymers. None, however, have proven to be clinically viable. A long-term vitreous substitute remains to be found, and recent research suggests promise in the area of synthetic polymers. Here we review the currently available vitreous substitutes, as well those in the experimental phase. We classify these compounds based on their functionality, composition, and properties. We also discuss the clinical use, advantages, and shortcomings of the various substitutes. In addition we define the ideal vitreous substitute and highlight the need for a permanent substitute with long-term viability and compatibility. Finally, we attempt to define the future role of biomaterials research and the various functions they may serve in the area of vitreous substitutes.

Metabolic physiology in age related macular degeneration

Ischemia and hypoxia have been implicated in the pathophysiology of age related macular degeneration (AMD). This has mostly been based on studies on choroidal perfusion, which is not the only contributor to retinal hypoxia found in AMD eyes. Other features of AMD may also interfere with retinal oxygen metabolism including confluent drusen, serous or hemorrhagic retinal detachment, retinal edema and vitreoretinal adhesion. Each of these features contributes to retinal hypoxia: the drusen and retinal elevation by increasing the distance between the choriocapillaris and retina; vitreoretinal adhesion by reducing diffusion and convection of oxygen towards and vascular endothelial growth factor (VEGF) away from hypoxic retinal areas. Hypoxia-inducible-factor is known to exist in subretinal neovascularization and hypoxia is the main stimulus for the production of VEGF. Each feature may not by itself create enough hypoxia and VEGF accumulation to stimulate wet AMD, but they may combine to do so. Choroidal ischemia in AMD has been demonstrated by many researchers, using different technologies. Choroidal ischemia obviously decreases oxygen delivery to the outer retina. Confluent drusen, thickening of Bruch's membrane and any detachment of retina or retinal pigment epithelium, increases the distance between the choriocapillaris and the retina and thereby reduces the oxygen flux from the choroid to the outer retina according to Fick's law of diffusion. Retinal elevation and choroidal ischemia may combine forces to reduce choroidal oxygen delivery to the outer retina, produce retinal hypoxia. Hypoxia leads to production of VEGF leading to neovascularization and tissue edema. A vicious cycle may develop, where VEGF production increases effusion, retinal detachment and edema, further increasing hypoxia and VEGF production. Adhesion of the viscous posterior vitreous cortex to the retina maintains a barrier to diffusion and convection currents in the vitreous cavity according to the laws of Fick's, Stokes-Einstein and Hagen-Poiseuille. If the vitreous is detached from the surface of the retina, the low viscosity fluid transports oxygen and nutrients towards an ischemic area of the retina, and cytokines away from the retina, at a faster rate than through attached vitreous gel. Vitreoretinal adhesion can exacerbate retinal hypoxia and accumulation of cytokines, such as VEGF. Vitreoretinal traction can also cause hypoxia by retinal elevation. Conceivably, the basic features of AMD, drusen, choroidal ischemia, and vitreoretinal adhesion are independently determined by genetics and environment and may combine in variable proportions. If the resulting hypoxia and consequent VEGF accumulation crosses a threshold, this will trigger effusion and neovascularization.