Perfluorocarbon liquid: its application in vitreoretinal surgery and related ocular inflammation

Application of high intensity focused ultrasound combined with nanomaterials in anti-tumor therapy

High intensity focused ultrasound (HIFU) has demonstrated its safety, efficacy and noninvasiveness in the ablation of solid tumor. However, its further application is limited by its inherent deficiencies, such as postoperative recurrence caused by incomplete ablation and excessive intensity affecting surrounding healthy tissues. Recent research has indicated that the integration of nanomaterials with HIFU exhibits a promising synergistic effect in tumor ablation. The concurrent utilization of nanomaterials with HIFU can help overcome the limitations of HIFU by improving targeting and ablation efficiency, expanding operation area, increasing operation accuracy, enhancing stability and bio-safety during the process. It also provides a platform for multi-therapy and multi-mode imaging guidance. The present review comprehensively expounds upon the synergistic mechanism between nanomaterials and HIFU, summarizes the research progress of nanomaterials as cavitation nuclei and drug carriers in combination with HIFU for tumor ablation. Furthermore, this review highlights the potential for further exploration in the development of novel nanomaterials that enhance the synergistic effect with HIFU on tumor ablation.

Flexible Acetylcholine Neural Probe with a Hydrophobic Laser-Induced Graphene Electrode and a Fluorous-Phase Sensing Membrane

This work develops the first laser-induced graphene (LIG)-based electrochemical sensor with a superhydrophobic fluorous membrane for a flexible acetylcholine (ACh) sensor. ACh regulates several physiological functions, including synaptic transmission and glandular secretion. The ACh sensing membrane is doped with a fluorophilic cation-exchanger that can selectively measure ACh based on the inherent selectivity of the fluorous phase for hydrophobic ions, such as ACh. The fluorous-phase sensor improves the selectivity for ACh over Na+ and K+ by 2 orders of magnitude (compared to traditional lipophilic membranes), thus lowering the detection limit in artificial cerebrospinal fluid (aCSF) from 331 to 0.38 μ M, thereby allowing measurement in physiologically relevant ranges of ACh. Engraving LIG under argon creates a hydrophobic surface with a 133.7° contact angle, which minimizes the formation of a water layer. The flexible solid-contact LIG fluorous sensor exhibited a slope of 59.3 mV/decade in aCSF and retained function after 20 bending cycles, thereby paving the way for studying ACh's role in memory and neurodegenerative diseases.

Vitreous substitutes and tamponades - A review of types, applications, and future directions

Vitreous substitutes and tamponades occupy the vitreous cavity following vitrectomy in the management of various conditions such as retinal detachment, macular hole, and diabetic retinopathy. Such replacements can be for the short term (gases such as sulfur hexafluoride (SF6) and perfluoropropane (C3F8) or long term (such as silicone oils). Certain substitutes such as perfluorocarbon liquids are used only transiently during surgery as "a third hand" or rarely till a few days post surgery. Hydrogels and hyaluronan derivatives are among the newer vitreous substitutes that are showing promise for the future, albeit still under investigation. still being investigated for use as vitreous substitutes. These materials have properties similar to the natural vitreous and may offer advantages such as improved biocompatibility and biodegradability. Although vitreous substitutes are valuable tools in treating vitreoretinal conditions, they carry risks and potential complications such as cataract formation, glaucoma, and inflammation. The current communication extensively reviews the available literature on vitreous tamponades. It details the composition and properties of various vitreous substitutes and tamponades available for the clinician, highlighting the techniques of usage, indications, and limitations.

A minimum specification dataset for liquid ocular endotamponades: recommendations by a European expert panel

PURPOSE

To propose a minimum specification dataset to characterize liquid ocular endotamponades (OEs), namely silicone oil (SO), heavy SO (HSO), perfluorodecalin (PFD), and perfluoro-octane (PFO), in terms of physicochemical properties, purity and available evidence of safety, in line with ISO16672:2020.

METHODS

An evidence-based consensus using the expert panel technique was conducted. Two facilitators led a committee of 11 European experts. Facilitators prepared a dataset for each compound including the list of specifications relevant for the safety, identified by the group members on the basis of expertise and a comprehensive literature review. Each item was ranked by each member using a 9-point scale from 1 "absolutely to not include" to 9 "absolutely to include" in two rounds followed by discussion. Only items reaching consensus (score ≥ 7 from ≥ 75% of members) were included in the final datasets.

RESULTS

For all OEs, consensus was reached to include manufacturer, density, refractive index, chemical composition, dynamic viscosity, interfacial and surface tension, endotoxins, in vitro cytotoxicity assessment, and any evidence from ex vivo and/or in vivo tests for safety assessment. Additional specifications were added for SO (molecular weight distribution, content of oligosiloxanes with MW ≤ 1000 g/mol, spectral transmittance) and PFD/PFO (% of pure PFD/PFO in the final product, vapor pressure, chemical analyses performed for safety assessment).

CONCLUSION

The proposed evidence-based minimum specification datasets for SO, HSO, PFD, and PFO have the potential to provide surgeons and health service purchasers with an easily available overview of the most relevant information for the safety assessment of OEs.

Recurrences and Macular Complications after Perfluorocarbon-Liquid-Free Vitrectomy for Primary Rhegmatogenous Retinal Detachment

INTRODUCTION

This study investigates factors associated with recurrent rhegmatogenous retinal detachment (RRD), macular complications, and visual outcomes after pars plana vitrectomy (PPV) without perfluorocarbon liquids (PFCLs) for primary RRD.

METHODS

A longitudinal cohort study included consecutive patients with RRD who underwent PFCL-free PPV. Postoperative visual acuity and spectral-domain optical coherence tomography findings [cystoid macular edema (CME), epiretinal membrane (ERM), ellipsoid zone/interdigitation zone (EZ/IZ) damage] were collected. Logistic regression and linear mixed models analyzed rates and risk factors for RRD recurrence, CME, ERM, EZ/IZ damage, and visual acuity at 12 months.

RESULTS

346 eyes with RRD were studied. Single-operation success rates were 96% and 93% for uncomplicated (n = 274 eyes) and complicated (n = 72 eyes) RRD, respectively. Factors associated with RRD recurrence were posterior retinal breaks [odds ratio (OR) = 10.7 compared to peripheral retinal breaks, p = 0.008], silicone oil tamponade (OR = 5.66 compared to gas, p = 0.01), and sectorial laser retinopexy (OR = 4.34 compared to 360° laser retinopexy, p = 0.007). The prevalence of CME, ERM, and EZ/IZ damage at 12 months was 10%, 9%, and 6%, respectively. Eyes with EZ/IZ defects had worse postoperative visual acuity in both uncomplicated and complicated RRD. Proliferative vitreoretinopathy (OR = 2.95, p = 0.03) and silicone oil tamponade (OR = 3.70 compared to gas, p = 0.05) were associated with EZ/IZ damage.

CONCLUSIONS

PFCL-free PPV demonstrated satisfactory single-operation success rates for uncomplicated and complicated RRD, with a low prevalence of macular complications. Analyzing factors associated with RRD recurrence can provide provisional recommendations for PFCL-free approaches in the absence of randomized trials.

Long-Term Use of a Temporary Keratoprosthesis and Perfluorocarbon in Traumatic Retinal Detachment Repair

Purpose

To present a technique for optimizing repair of traumatic retinal detachments (RDs).

Methods

A patient was followed in an outpatient setting with clinical examinations, optical coherence tomography, widefield fundus photography, and anterior segment imaging.

Results

The patient presented with a total RD after ruptured globe repair. The patient had combined corneal and retinal surgery with placement of a temporary keratoprosthesis (TKP) and vitrectomy with perfluorocarbon liquid (PFCL) to reattach the retina. The TKP and PFCL were left in the eye for 2 weeks before a planned silicone oil exchange and penetrating keratoplasty were performed. Four months postoperatively, the patient presented with a partially attached retina and improved vision.

Conclusions

In this case, a ruptured globe decompensated several months after primary repair. The prolonged use of the TKP allowed for optimal surgical visualization, enhanced office-based assessment, and limited endothelial cell loss of the donor corneal tissue.

Iatrogenic macular hole during liquid perfluorocarbon injection in retinal detachment surgery

To describe a macular hole development during intravitreal injection of perfluorocarbon liquid used to repair a regmatogenous retinal detachment. CLINICAL CASE: A 73-year-old man presented with superotemporal regmatogenous retinal detachment. During surgery, along the perflorocarbon liquid injection, a full thickness macular developed and perfluorocarbon was accumulated in subretinal space. Perfluorocarbon liquid was then extracted through the macular hole. Postoperatively, ocular coherence tomography confirmed the existence of a full-thickness macular hole. One month later, this macular hole was successfully treated with the use of an Inverted internal limiting membrane flap. Intravitreous liquid PFC injection is a resource to aid in subretineal fluid exit. A number of complications, both intra and postoperative, have been associated with the use of PFC. This is the first reported case of a complete macular hole secondary to PFC injection.

Semifluorinated Alkanes as New Drug Carriers-An Overview of Potential Medical and Clinical Applications

Fluorinated compounds have been used in clinical and biomedical applications for years. The newer class of semifluorinated alkanes (SFAs) has very interesting physicochemical properties including high gas solubility (e.g., for oxygen) and low surface tensions, such as the well-known perfluorocarbons (PFC). Due to their high propensity to assemble to interfaces, they can be used to formulate a variety of multiphase colloidal systems, including direct and reverse fluorocarbon emulsions, microbubbles and nanoemulsions, gels, dispersions, suspensions and aerosols. In addition, SFAs can dissolve lipophilic drugs and thus be used as new drug carriers or in new formulations. In vitreoretinal surgery and as eye drops, SFAs have become part of daily clinical practice. This review provides brief background information on the fluorinated compounds used in medicine and discusses the physicochemical properties and biocompatibility of SFAs. The clinically established use in vitreoretinal surgery and new developments in drug delivery as eye drops are described. The potential clinical applications for oxygen transport by SFAs as pure fluids into the lungs or as intravenous applications of SFA emulsions are presented. Finally, aspects of drug delivery with SFAs as topical, oral, intravenous (systemic) and pulmonary applications as well as protein delivery are covered. This manuscript provides an overview of the (potential) medical applications of semifluorinated alkanes. The databases of PubMed and Medline were searched until January 2023.

Advances in Polysaccharide- and Synthetic Polymer-Based Vitreous Substitutes

The vitreous humour is a gel-like structure that composes the majority of each eye. It functions to provide passage of light, be a viscoelastic dampener, and hold the retina in place. Vitreous liquefaction causes retinal detachment and retinal tears requiring pars plana vitrectomy for vitreous substitution. An ideal vitreous substitute should display similar mechanical, chemical, and rheological properties to the natural vitreous. Currently used vitreous substitutes such as silicone oil, perfluorocarbon liquids, and gases cannot be used long-term due to adverse effects such as poor retention time, cytotoxicity, and cataract formation. Long-term, experimental vitreous substitutes composed of natural, modified and synthetic polymers are currently being studied. This review discusses current long- and short-term vitreous substitutes and the disadvantages of these that have highlighted the need for an ideal vitreous substitute. The review subsequently focuses specifically on currently used polysaccharide- and synthetic polymer-based vitreous substitutes, which may be modified or functionalised, or employed as the derivative, and discusses experimental vitreous substitutes in these classes. The advantages and challenges associated with the use of polymeric substitutes are discussed. Innovative approaches to vitreous substitution, namely a novel foldable capsular vitreous body, are presented, as well as future perspectives related to the advancement of this field.

Vitreous Substitutes from Bench to the Operating Room in a Translational Approach: Review and Future Endeavors in Vitreoretinal Surgery

Vitreous substitutes are indispensable tools in vitreoretinal surgery. The two crucial functions of these substitutes are their ability to displace intravitreal fluid from the retinal surface and to allow the retina to adhere to the retinal pigment epithelium. Today, vitreoretinal surgeons can choose among a plethora of vitreous tamponades, and the tamponade of choice might be difficult to determine in the ever-expanding range of possibilities for a favorable outcome. The currently available vitreous substitutes have disadvantages that need to be addressed to improve the surgical outcome achievable today. Herein, the fundamental physical and chemical proprieties of all vitreous substitutes are reported, and their use and clinical applications are described alongside some surgical techniques of intra-operative manipulation. The major upcoming developments in vitreous substitutes are extensively discussed, keeping a translational perspective throughout. Conclusions on future perspectives are derived through an in-depth analysis of what is lacking today in terms of desired outcomes and biomaterials technology.

Comparison of Perfluorocarbon Liquids Cytotoxicity Tests: Direct Contact Versus the Test on Liquid Extracts

The purpose of this study is to compare the in vitro cytotoxicity tests according to the ISO 10993-5 (2009) standards using direct contact and the test on liquid extracts of compounds previously identified as possible toxic impurities in perfluorocarbon liquids (PFCLs) for use in vitreoretinal surgery. Compounds including perfluorooctanoic acid (PFOA), 1H-perfluorooctane (1H-PFO), 2H-tridecafluoro-2-methylpentane, 1H,2H-octafluorocyclopentane, and 2H,3H-decafluoropentane were analyzed by 19F NMR before and after extraction using an aqueous solution and tested by both the direct contact and liquid extract tests in L929, BALB 3T3, and ARPE-12 cells. The concentration that reduced in vitro cell viability by 30%, the cytotoxicity concentration threshold (CC30), was determined for each compound. 19F NMR spectroscopy confirmed the immiscibility of perfluoro-n-octane (PFO) and 1H-PFO and the solubility of PFOA with the extraction vehicle. The other samples reacted with the extraction vehicle, releasing fluoride ions. Using the direct contact test, the CC30 of PFOA, 1H-PFO, 2H-tridecafluoro-2-methylpentane, 1H,2H-octafluorocyclopentane, and 2H,3H-decafluoropentane corresponded to 48 124, 50, 14, 8035, and 46 ppm, respectively. The method on liquid extracts did not detect cytotoxicity in three out of five tested compounds, and CC30 could not be determined. In conclusion, the in vitro cytotoxicity test by direct contact revealed a positive correlation between cell toxicity and the concentration of the tested substance. Conversely, the test on liquid extracts hardly detected the cytotoxicity of toxic impurities in PFCLs. Thus, only the cytotoxicity test by direct contact, according to ISO 10993-5 (2009), is a sensible and reliable method to detect possible cytotoxic impurities in PFCLs to guarantee patient safety.

Biomaterials for Ophthalmic Applications

Ophthalmology is the branch of medicine that deals with diseases of the eye, the organ responsible for vision, and its attachments. Biomaterials can be made with different types of materials and can replace or improve a function or an organ, specifically the eye in the case of ophthalmic biomaterials. Biomaterials are substances that interact with biological systems for a medical purpose, either as a therapeutic (treat, augment, repair, or replace a tissue function of the body) or a diagnostic agent, and have continued to improve over the years, leading to the creation of new biomaterials. With the arrival of new generations, biomaterials have succeeded in reducing complications and toxicity and improving biocompatibilities associated with older generations. With the aging population, eye problems are becoming more prevalent, and biomaterials have helped in recent years to improve or restore vision, improving the quality of life of many patients. This review focuses on the most clinically used ophthalmic biomaterials, including contact lenses, intraocular lenses, artificial tears, inlays and vitreous replacements. Tissue engineering is presented as a new tool that is able to be treat several ophthalmologic disorders.

Translational and clinical advancements in management of proliferative vitreoretinopathy

PURPOSE OF REVIEW

Despite advancement in the surgical instrumentation and techniques, proliferative vitreoretinopathy (PVR) remains the most common cause for failure of rhegmatogenous retinal detachment (RRD) repair. This review discusses ongoing translational and clinical advancements in PVR.

RECENT FINDINGS

PVR represents an exaggerated and protracted scarring process that can occur after RRD. The primary cell types involved are retinal pigment epithelium, glial, and inflammatory cells. They interact with growth factors and cytokines derived from the breakdown of the blood-retinal barrier that trigger a cascade of cellular processes, such as epithelial-mesenchymal transition, cell migration, chemotaxis, proliferation, elaboration of basement membrane and collagen and cellular contraction, leading to overt retinal pathology. Although there are currently no medical therapies proven to be effective against PVR in humans, increased understanding of the risks factors and pathophysiology have helped guide investigations for molecular targets of PVR. The leading therapeutic candidates are drugs that mitigate growth factors, inflammation, and proliferation are the leading therapeutic candidates.

SUMMARY

Although multiple molecular targets have been investigated to prevent and treat PVR, none have yet demonstrated substantial evidence of clinical benefit in humans though some show promise. Advancements in our understanding of the pathophysiology of PVR may help develop a multipronged approach for this condition.

Biocompatibility of intraocular liquid tamponade agents: an update

Intraocular liquids tamponade agents, such as perfluorocarbon liquids (PFCLs), semifluorinated alkanes (SFAs), silicone oils (SOs) and heavy silicone oils (HSOs), are a crucial intraoperative and/or postoperative tool in vitreoretinal surgery, in particular for the management of complex vitreoretinal diseases. However, their use is not without complications, which are potentially severe. Consequently, a growing interest has been devoted to the biocompatibility of these compounds and the adequacy of current regulations that should guarantee their safety. Obviously, an updated knowledge on research findings and potential risks associated to the use of intraocular liquid compounds is essential, not only for vitreoretinal surgeons, but also for any ophthalmologist involved in the management of patients receiving intraocular liquid tamponades. In light of this, the review provides a comprehensive characterisation of intraocular liquid tamponades, in terms of physical and chemical properties, current clinical use and possible complications. Moreover, this review focuses on the safety profile of these compounds, summarising the existing regulation and the available evidence on their biocompatibility.

Recent Advances in Hydrogels: Ophthalmic Applications in Cell Delivery, Vitreous Substitutes, and Ocular Adhesives

With the prevalence of eye diseases, such as cataracts, retinal degenerative diseases, and glaucoma, different treatments including lens replacement, vitrectomy, and stem cell transplantation have been developed; however, they are not without their respective shortcomings. For example, current methods to seal corneal incisions induced by cataract surgery, such as suturing and stromal hydration, are less than ideal due to the potential for surgically induced astigmatism or wound leakage. Vitrectomy performed on patients with diabetic retinopathy requires an artificial vitreous substitute, with current offerings having many shortcomings such as retinal toxicity. The use of stem cells has also been investigated in retinal degenerative diseases; however, an optimal delivery system is required for successful transplantation. The incorporation of hydrogels into ocular therapy has been a critical focus in overcoming the limitations of current treatments. Previous reviews have extensively documented the use of hydrogels in drug delivery; thus, the goal of this review is to discuss recent advances in hydrogel technology in surgical applications, including dendrimer and gelatin-based hydrogels for ocular adhesives and a variety of different polymers for vitreous substitutes, as well as recent advances in hydrogel-based retinal pigment epithelium (RPE) and retinal progenitor cell (RPC) delivery to the retina.

Toxicity Threshold of Perfluorocarbon Liquids for Intraocular Use: Dose-Response Assessment of In Vitro Cytotoxicity of Possible Contaminants

Purpose

This study assessed the cytotoxicity of the impurities detected in the perfluorooctane (PFO) batches for vitreoretinal surgery that were associated with serious adverse incidents of ocular toxicity, namely, the perfluorooctanoic acid (PFOA), 1H,1H,7H-dodecafluoro-1-heptanol (DFH), 1H-perfluorooctane (1H-PFO), ethylbenzene, anhydrous p-xylene, and perfluoro-2-butyltetrahydrofurane, and two additional substances 1H,1H,1H,2H,2H-perfluorooctane (5H-PFO) and hexafluoro-1,2,3,4-tetrachlorobutane.

Methods

Serial dilutions were tested by in vitro direct contact cytotoxicity test, validated in accordance with the ISO 10993-5:2009 standard using BALB3T3 and ARPE-19 cell lines, after sample application for 24 hours.

Results

Six of the eight tested substances were cytotoxic according to the above-mentioned ISO standard. Anhydrous p-xylene, ethylbenzene, and PFOA were the most cytotoxic impurities as traces 1.55 ppm, 1.06 ppm, and 28.4 ppm reached the cytotoxicity limit, respectively. Hexafluoro-1,2,3,4-tetrachlorobutane, DFH, and 1H-PFO were cytotoxic at 980, 22,500, and 123,000 ppm, respectively. Both 5H-PFO and perfluoro-2-butyltetrahydrofuran were non-cytotoxic at the highest available concentrations (≥970,000 ppm). The dose-response curves allowed to calculate the cytotoxic concentration (CC₃₀) for each tested substance that would reduce 30% of cell viability and corresponding to the cytotoxicity threshold according to ISO 10993-5.

Conclusions

Our study determined the in vitro cytotoxicity of several impurities in PFO associated with serious adverse incidents in retinal surgery patients.

Translational Relevance

Severe cytotoxicity of some impurities previously found in toxic perfluorocarbon liquids was confirmed. The cytotoxicity test validated according to the ISO 10993-5:2009 standard is a sensible and fast method for reliable detection of the cytotoxicity in perfluorocarbon liquids to guarantee maximal safety for the patients.

Viscoelastic-assisted inverted cover and free ILM flap techniques

statement: Surgical technique: an innovative way of using cohesive viscoelastic to stabilize the ILM flap during the cover inverted-flap and free-flap procedures.Summary statement: Surgical technique: an innovative way of using cohesive viscoelastic to stabilize the ILM flap during the covering step in the inverted-flap and free-flap procedures.

A Supersaturated Oxygen Emulsion for the Topical Treatment of Ocular Trauma

INTRODUCTION

Roughly 13% of all battlefield injuries include some form of ocular trauma. Ocular tissue preservation is critical for wound healing for warfighters with ocular injuries. Our team hypothesized that oxygen plays a vital role in ocular tissue preservation and wound healing and has developed a supersaturated oxygen emulsion (SOE) for the topical treatment of ocular trauma.

MATERIALS AND METHODS

The partial pressure of oxygen (PO2) was measured in the SOE. Safety and efficacy studies were carried out in primary human corneal epithelial (HCE) cells, as the outermost layer is the first barrier to chemical and mechanical injury. Western blot, scratch assay, and MTT assays were conducted to determine the effect of the SOE on various molecular markers, the rate of scratch closure, and cellular viability, respectively.

RESULTS

Data indicate that the SOE releases oxygen in a time-dependent manner, reaching a partial pressure within the emulsion over four times atmospheric levels. Studies in HCE cells indicate that application of the SOE does not lead to DNA damage, promote cell death, or hinder the rate of scratch closure and enhances cellular viability. Preliminary studies were carried out with chloropicrin (CP; developed as a chemical warfare agent and now a commonly used pesticide) as a chemical agent to induce ocular injury in HCE cells. CP exposures showed that SOE treatment reverses CP-induced DNA damage, apoptotic cell death, and oxidative stress markers.

CONCLUSIONS

Maintaining adequate tissue oxygenation is critical for tissue preservation and wound repair, especially in avascular tissues like the cornea. Further studies examining the application of the SOE in corneal injury models are warranted.

Intra-operative scleral rupture during 23 gauge pars plana vitrectomy: a case report

BACKGROUND

Use of perfluorocarbon liquid (PFCL) has been increasingly growing as an adjuvant in vitreo-retina surgeries. Some commonly encountered complications with its use include subretinal migration, formation of sticky silicone oil or retained PFCL in vitreous cavity and anterior chamber. Scleral rupture during PFCL injection has a rare occurrence. We report an unexpected event of scleral rupture during PFCL injection and discuss the management challenges faced by the surgeon.

CASE PRESENTATION

A 66 year indo-aryan male was undergoing pars-plana vitrectomy (PPV) with diagnosis of subtotal rhegmatogenous retinal detachment (RD) with Proliferative Vitreo-retonipathy (PVR)-B. After near total vitrectomy PFCL was being injected and then there was sudden poor visualization of fundus with development of bullous RD and globe hypotony. The surgeon was not able to figure out the cause of hypotony and air was switched on in the infusion cannula. This further complicated the situation resulting in migration of air in the anterior chamber, posterior dislocation of intraocular lens complex, 180° inferior retinal dialysis and ballooning of the conjunctiva which gave a clue of probable scleral rupture. Conjunctival peritomy was performed superiorly and scleral defect was noted. Intraocular tissue incarceration and air leak was visible from the wound. This confirmed scleral rupture during PFCL injection. Repositioning of incarcerated retina was not possible and retinectomy was performed followed by repair of scleral rupture with lots of difficulty in a vitrectomised eye.

CONCLUSION

PFCL injection, a crucial step of vitreoretina surgery, should be performed slowly with extreme caution maintaining an optimal intraocular pressure to prevent devastating complications like scleral rupture.

Hints for Gentle Submacular Injection in Non-Human Primates Based on Intraoperative OCT Guidance

Purpose

Delivery of Advanced Therapy Medicinal Products to the submacular space is increasingly evolving into a therapeutic modality. Cell replacement for age-related macular degeneration (AMD) and gene therapy for RPE65 are recent successful examples. Herein, a nonhuman primate (NHP) model was used to investigate surgical means to detach the macula.

Methods

Sixteen eyes of 13 healthy macaques underwent a 25-gauge vitrectomy and subretinal injection of balanced salt solution monitored by microscope-integrated intraoperative optical coherence tomography (miOCT). The animals were followed with OCT and histology.

Results

The miOCT monitoring allowed a more precise definition of surgical trauma ranging from an initial full-thickness foveal tear, or induction of a cystoid macular edema (CME), until no foveal defect was discernible, as the technique improved. However, as the subretinal fluid wave detached the fovea, the aforementioned lesions formed, whereas persistent retinal adhesion reproducibly proved to remain in the distal parafoveal semi-annulus. Measures to reduce foveal trauma during submacular fluid injection included reducing intraocular pressure, injection volume, and velocity, as well as the retinal location for bleb initiation, use of a vitreous tamponade, and a dual-bore subretinal cannula.

Conclusions

A stable very low intraocular pressure and careful subretinal injection may avoid tangential macular stretching or mechanical CME formation, while vitreous tamponade may facilitate a more lamellar subretinal flow, all thereby reducing foveal trauma during submacular injection in NHP.

Translational Relevance

These results can be relevant to any submacular surgery procedure used today, as they synergistically reduce the risk of compromising foveal integrity.

In vitro generation of primary cultures of human hyalocytes

Purpose

A growing number of studies on animal models have demonstrated that some ocular diseases are the result of the interaction between hyalocytes and the ocular inflammatory setting. Endogenous and exogenous substances might alter the structure and behavior of hyalocytes that can contribute to the pathogenesis of some ocular diseases. Obtaining primary cultures of human hyalocytes could help understand the role of these cells in response to different treatments.

Methods

Hyalocytes were isolated from eyes of 54 patient volunteers subjected to vitrectomy for different clinical reasons. By testing different matrices and growth media, we reproducibly generated primary cultures of hyalocytes that we characterized morphologically and biologically, basally and upon treatment with several agents (basic fibroblast growth factor (bFGF), transforming growth factor beta 1 (TGF-β), platelet-derived growth factor subunit-BB (PDGF-BB), ascorbic acid, dexamethasone, and hydrogen peroxide).

Results

We were able to generate primary cultures from vitreous human samples, growing the cells on collagen-coated plates in Iscove's modified Dulbecco's medium supplemented with 10% fetal bovine serum; primary cells expressed the hyalocyte markers. Specific cytoskeletal modifications were observed upon treatment with bFGF, TGF-β, PDGF-BB, ascorbic acid, dexamethasone, and hydrogen peroxide. Only bFGF was able to promote cell growth and hyaluronic acid production.

Conclusions

We describe for the first time the generation and the characterization of primary cultures of human hyalocytes from living donors. Although human hyalocytes share some characteristics with animal hyalocytes, human hyalocytes have their own features typical of the species, confirming how important human experimental models are for investigating human pathologies and their treatments.

Double Retinal Tamponade for Treatment of Rhegmatogenous Retinal Detachment with Proliferative Vitreoretinopathy and Inferior Breaks

Purpose

To evaluate the efficacy and safety of the simultaneous use of short-term perfluoro-n-octane (PFO) with perfluoropropane (C3F8) gas to achieve retinal reattachment in eyes with rhegmatogenous retinal detachment (RRD) with proliferative vitreoretinopathy (PVR) grade C and multiple retinal breaks including inferior breaks.

Design

This is a prospective interventional case series study. Patients and Methods. The study was a prospective noncomparative interventional study. It included 30 eyes of 30 patients who had RRD with PVR grade C and multiple retinal breaks including inferior tears attending the vitreoretinal unit of Minia University Hospital, Egypt. The mean age was 50.2 ± 10.63 years; 18 patients were females and 12 were males. Combined phacoemulsification and 23 G pars plana vitrectomy (PPV) with double retinal tamponade by C3F8 and PFO were done, and PFO was removed in 10–14 days. The patients were followed up for one year. The primary outcome was to achieve successful retinal reattachment, and the secondary outcomes were visual improvement and occurrence of complications.

Results

Successful retinal reattachment was obtained in 28 eyes out of 30 (93.3%), and 2 eyes (6.7%) had recurrent RD. Best-corrected distance visual acuity (BCDVA) in logMAR was significantly improved from baseline 1.74 ± 0.05 to 0.93 ± 0.04, 0.82 ± 0.05, 0.80 ± 0.07, and 0.73 ± 0.055 at follow-up visits 3, 6, and 9 months and one year, respectively (P ≤ 0.001). There were no serious ocular complications recorded.

Conclusions

The results of this study indicated that primary vitrectomy with simultaneous use of both C3F8 and short-term PFO as retinal tamponades was effective and safe in the management of complex cases of RRD with PVR grade C and inferior breaks. This trial is registered with NCT04168255.

Outcomes of a postoperative perfluorocarbon liquid tamponade for complex retinal detachments: 12 years of experience in southern Thailand

BACKGROUND

The study evaluates both functional and anatomical outcomes of retinal detachment (RD) repair by vitrectomy and perfluorocarbon liquid (PFCL) tamponade.

METHODS

A retrospective chart review of patients who underwent vitrectomy using PFCL tamponade for RD repair from causes such as giant tear, chronic RD, or RD with previously failed surgery.

RESULTS

This study included 122 eyes from 121 patients. One-hundred fourteen eyes (93.5%) had baseline vision worse than 20/200. The median duration of intraocular PFCL retainment was 14 days before gas or silicone oil replacement. The retinal reattachment rate was 80.3%. At 1 year, the retention probability of retinal reattachment was 0.84 (95% confidence interval, 0.77-0.91). Although visual improvement was found in 45.9% of patients, the median of final vision was not different between baseline and the last visit.

CONCLUSION

The rate of retinal reattachment operated with a short- to medium-term PFCL tamponade achieved a high satisfaction rate. However, postoperative hypotony was a predictor for unfavorable visual and anatomical outcomes.

Medium-term tamponade with vitrectomy and perfluorodecalin for the management of complex retinal detachments

PURPOSE

To describe the clinical presentation, anatomical and visual outcome of a series of patients in our department with complex retinal detachments, managed with vitrectomy and perfluorodecalin (PFD) for medium-term tamponade.

STUDY DESIGN

Retrospective case series.

METHODS

Retrospective analysis of the medical records of all patients in the last 6 years presenting with complex retinal detachment managed with vitrectomy where PFD was used as a medium-term tamponade.

RESULTS

A total of 85 eyes in 85 patients were included in the study, with a mean follow-up period of 16.0 ± 2.67 months (range 3-59). About 26 detachments presented with associated PVR-C, and 10 had giant retinal tears. The location of the retinal detachment was inferior in 40% of cases, and total in 18.9% of cases. Anatomical success, defined as retinal reattachment at 12 months, was achieved in 98.8% of cases, and there was a mean improvement in BCVA of logMAR 0.64 ± 0.20, which was statistically significant (p < 0.001, paired t-test 6.23). Of the 41 phakic eyes included in the study, 20 underwent cataract surgery within the follow-up period.

CONCLUSION

In this case series, we have demonstrated a 98.8% anatomical success and significant improvement in BCVA, with no reports of retinal toxicity. Medium-term tamponade PFD appears to be an efficacious and safe technique for management of a variety of complex retinal detachments, including those secondary to GRT, the presence of PVR-C, inferior location, tractional, traumatic, and re-detachments.

Effects of perfluorocarbon liquids in macular hole retinal detachment treatment

OBJECTIVE

This study aims to evaluate the clinical efficacy and visual function prognosis of macular hole retinal detachment treatment for high myopia by inverting the internal limiting membrane to overlay the macular hole with the assistance of perfluorocarbon liquids.

METHODS

A total of 55 high myopia patients, who received macular hole retinal detachment treatment from 2013 to 2016, were included in this study. Among these patients, 38 patients were assigned to the first group and 17 patients (perfluorocarbon liquids) were assigned to the second group. The second group was further divided into two subgroups, according to the overlaying layer number of the internal limiting membrane valve: A group (multiple layers) and B group (single layer).

RESULTS

The success rate of the internal limiting membrane inversion and overlaying on the macular hole was 23.68% and 100% in the first and second group, respectively. The differences in macular hole closing rate and postoperative best-corrected visual acuity between these two groups were statistically significant (p < 0.05). Furthermore, the differences in macular morphology recovery between the A and B groups were also statistically significant (p = 0.004 < 0.05).

CONCLUSION

Perfluorocarbon liquids play a positive role in the operation process of the internal limiting membrane.

Macular optical coherence tomography findings after vitreoretinal surgery for rhegmatogenous retinal detachment

The primary aim of this study was to summarize and illustrate the main structural cross-sectional optical coherence tomography findings encountered after vitreoretinal surgery for rhegmatogenous retinal detachment. This was a non-systematic review of literature on structural cross-sectional optical coherence tomography findings after vitreoretinal surgery for rhegmatogenous retinal detachment. Adequate illustrations of the main findings described were found after a retrospective analysis of imaging and charts of patients operated at the department where this study was performed. The main structural cross-sectional optical coherence tomography findings after vitreoretinal surgery for rhegmatogenous retinal detachment included persistent subretinal fluid, subretinal blebs, retinal folds, subretinal perfluorocarbon liquids, macular alterations related to silicone oil, epiretinal membranes, proliferative vitreoretinopathy, cystoid macular edema, macular holes, and recurrent retinal detachment. In conclusion, optical coherence tomography was a useful tool after vitreoretinal surgery for rhegmatogenous retinal detachment. Some optical coherence tomography findings may not be evident on fundus examination, and optical coherence tomography can reveal essential details for the clinical management and the visual prognosis. Other findings, despite being visible on funduscopic examination, may be better assessed with the aid of optical coherence tomography. All these elements contribute to support the importance of tomographic assessment in the follow-up of eyes treated for vitreoretinal conditions.

Chemical compounds causing severe acute toxicity in heavy liquids used for intraocular surgery

Perfluorocarbon liquids (PFCLs) have been considered safe for intraocular manipulation of the retina, but since 2013 many cases of acute eye toxicity cousing blindness have been reported in various countries when using various commercial PFCLs. All these PFCLs were CE marked (Conformité Européenne), which meant they had been subjected to evaluation complying with the International Organization for Standardization (ISO) guidelines. These dramatic events raised questions about the safety of PFCLs and the validity of some cytotoxicity tests performed under ISO guidelines. Samples from toxic batches were analyzed by gas chromatography-mass spectrometry combined with Raman and infrared spectrometry. Perfluorooctanoic acid, dodecafluoro-1-heptanol, ethylbenzene and tributyltin bromide were identified and evaluated by a direct contact cytotoxicity test using ARPE-19 cell line, patented by our group (EP 3467118 A1). Perfluorooctanoic acid at a concentration of >0.06 mM and tributyltin bromide at a concentration of ≥0.016 mM were shown to be toxic, whereas the concentration found in the toxic samples reached 0.48 mM, and 0.111 mM, respectively. These finding emphasized the idea that determination of partially fluorinated compounds are not enough to guarantee the safety of these medical devices.

Evaluation of Cytotoxicity of Perfluorocarbons for Intraocular Use by Cytotoxicity Test In Vitro in Cell Lines and Human Donor Retina Ex Vivo

Purpose

To validate the cytotoxicity test of perfluorocarbon liquids (PFCLs) for intraocular use according to the ISO 10993-5 standard.

Methods

BALB/3T3, ARPE-19 cell lines, and 3-mm human retina ex vivo samples were cultured in 96-well plates. Contact areas of 22%, 59%, and 83% and 2.5-, 12-, and 24-hour contact times were tested in cell lines. Cell viability was quantified by 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in ARPE-19 and neutral red uptake (NRU) viability assay for BALB/3T3. Apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay in ARPE-19 cells. 1-H perfluorooctane (1H PFO) and purified perfluorooctane (PFO) were used as cytotoxic and not cytotoxic controls, respectively. Cell viability was assessed by MTT assay in retina ex vivo samples.

Results

Qualitative evaluation showed that cytotoxic control induced apoptosis, severe reactivity zones, and cytotoxicity according to ISO 10993-5 in all tested conditions. Quantitative evaluation of 1H PFO showed no cytotoxicity according to ISO 10993-5 on 22% areas, whereas cytotoxicity was detected on 59%, and 83% contact areas. The PFO was confirmed not to be cytotoxic in all tested conditions. Quantitative evaluation in retina ex vivo samples confirmed no cytotoxicity with PFO and cytotoxicity with 1H PFO.

Conclusions

The direct contact cytotoxicity test according to ISO 10993-5 is a suitable method to detect the cytotoxicity of PFCLs and was validated using quantitative and qualitative approaches in ARPE-19 and BALB/3T3 cells covering 59% of the cell surface areas for 24 hours.

Translational Relevance

Direct contact cytotoxicity test using specific conditions was validated, whereas different test conditions could not be validated.

How to Ward Off Retinal Toxicity of Perfluorooctane and Other Perfluorocarbon Liquids?

Purpose

Reactive and underfluorinated impurities are acknowledged as a source of cytotoxicity of perfluorocarbon liquids (PFCLs) used as blood substitutes. To determine whether this is also a relevant factor in retinal toxicity, we analyzed eight PFO batches associated with adverse ocular events.

Methods

(A) The amount of reactive and underflurinated impurities was analyzed by fluoride-selective potentiometry and expressed as H-value. (B) Cytotoxicity of these batches was determined by an ISO 10993-5-compliant extractive test and compared to published data generated with a direct-contact method. (C) A toxic PFO batch (061014) was purified to remove reactive and underfluorinated impurities. (A) and (B) -measurements were repeated after that. (D) The dose dependence of the H-value and cytotoxicity was determined in a dilution experiment.

Results

(A) The batches revealed H-values ranging from 1.400 ppm to 4.500 ppm. (B) All batches induced cell growth inhibition; seven must be classified as cytotoxic. Findings from ISO-conform extractive and direct-contact methods showed no difference. (C) After all reactive and underfluorinated impurities in batch 061014 were removed, the H-value dropped to <10 ppm and cytotoxicity disappeared. (D) Cytotoxicity increases gradually as the H-value rises.

Conclusions

The clinical relevance of the H-value as a safety parameter for PFO endotamponades could be proven. The H-value is a measure for reactive and underfluorinated impurities that cause toxicity of PFCLs and should be incorporated in each endotamponade specification with a limit of 10 ppm to prove the effectiveness of the ultra-purification required and ensure a safe product. Despite the fact that an (ISO)-standard literally is a "standard" only, which cannot cover all imaginable possibilities, the incorporation of the H-value determination into the relevant ISO standard has been initiated. If a thorough risk assessment results in risks that cannot be detected and/or managed by the effective standard, additional investigations have to be performed.

Advances in the treatment of rhegmatogenous retinal detachment

The pathogenesis of rhegmatogenous retinal detachment depends on three factors, namely, retinal rupture, vitreous liquefaction and traction causing the retina to separate from the pigment epithelium, among which retinal rupture is the most important. Retinopathy is caused by a gap between the neurosensory retina and the retinal pigment epithelium, which severely damages the visual function of the patient. Therefore, early clinical discovery, prevention and selection of an appropriate treatment are important. This article reviews progress in the treatment of retinal detachment.

Effect of Subretinal Fluid Drainage Using Perfluorocarbon During Retinal Detachment Repair on Postoperative Metamorphopsia

BACKGROUND AND OBJECTIVE

To determine whether subretinal fluid drainage (SRF) using perfluorocarbon (PFC) during rhegmatogenous retinal detachment (RRD) repair reduces postoperative metamorphopsia.

PATIENTS AND METHODS

Consecutive patients after RRD were evaluated for best-corrected visual acuity (BCVA), funduscopy, and metamorphopsia using M-CHARTS. Fundus autofluorescence and optical coherence tomography were performed. Clinical and operative data were collected.

RESULTS

The cohort included 30 patients, of whom 11 (36.7%) underwent intraoperative PFC injection. Rates of macula-off RRD were similar in the two groups (54.5% and 47.4%, P = .705). No association was found between PFC injection and metamorphopsia score. Preoperative macula-off RRD was associated with significantly higher vertical and horizontal metamorphopsia scores than preoperative macula-on. BCVA was significantly worse in the patients with metamorphopsia (logMAR 0.15 vs. logMAR 0.04; P = .042) CONCLUSION: Intraoperative SRF drainage with PFC appears to have no beneficial effect on postoperative metamorphopsia. Metamorphopsia is associated with macular status. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:e263-e270.].

Perfluorocarbon Liquid Vs. Subretinal Fluid Drainage during Vitrectomy for the Primary Repair of Rhegmatogenous Retinal Detachment: A Comparative Study

PURPOSE

To compare the anatomical and functional results achieved with subretinal fluid drainage (SRFD) and perfluorocarbon liquid (PFCL) use in patients with rhegmatogenous retinal detachment (RRD) treated by primary pars plana vitrectomy (PPV).

METHODS

The study included 162 eyes of 162 patients who underwent PPV for RRD, either with PFCL (n = 108) or SRFD (n = 54). The two groups were matched in 2:1 ratio for age, gender, and lens status. Groups were compared for rates of retinal reattachment, visual improvement, and the occurrence of recurrent RRD and any other postoperative complications.

RESULTS

Both groups had a single surgery success rate of 90.7%, and 100% of retinas were reattached by the end of follow-up. Both groups had similar final VA (0.30 ± 0.39 logMAR in the SRFD group and 0.35 ± 0.44 in the PFCL group; p = 0.48) and degrees of visual improvement (0.64 ± 0.75 logMAR in the SRFD group and 0.59 ± 0.89 in the PFC group; p = 0.71). Complication rates were also similar between groups. The rate of additional interventions was higher (although not statistically significant) in the PFCL group than the SRFD group, due to cases of PFCL retention (4.6% vs. 1.8%, respectively).

CONCLUSIONS

Both PFCL and SRFD achieved excellent results in terms of retinal reattachment and visual improvement, and have comparable safety profiles. A slightly higher rate of additional surgeries was found in the PFCL group. These findings indicate that PFCL are not necessary in routine PPV for RRD, as they do not improve the results achieved with SRFD and may be less cost-effective due to their higher price and potential for a higher rate of additional surgeries.

Surgical removal of submacular perfluorocarbon liquid with a 38-gauge flexible cannula combined with internal limiting membrane peeling and intravitreal air tamponade: a case series

BACKGROUND

To report a case series in which a modified technique was used to remove retained submacular perfluorocarbon liquid (PFCL) secondary to vitreoretinal surgery for rhegmatogenous retinal detachment.

CASE PRESENTATION

Four patients who had undergone pars plana vitrectomy for rhegmatogenous retinal detachment were further treated with surgical intervention because of retained submacular PFCL. With a three-port pars plana approach, after the internal limiting membrane peeling with indocyanine green staining, a 38-gauge flexible cannula was used to aspirate the submacular perfluorocarbon bubble, followed by fluid-air exchange and air injection into vitreous cavity. Submacular perfluorocarbon liquid was removed successfully and visual acuity had an improvement in all cases.

CONCLUSION

The surgical removal of retained submacular PFCL using a 38-gauge flexible cannula combined with internal limiting membrane peeling and intravitreal air tamponade may provide anatomical and visual satisfactory outcomes.

'Pseudo-calcifications': detection of perfluorocarbon residue on a computed tomography scan 15 years after liquid ventilation therapy at 3 months of age

Partial liquid ventilation using perfluorocarbons is a therapy that was once frequently used in paediatric populations for patients with severe respiratory distress. Perfluorocarbon is a non-toxic, insoluble and radiopaque vector through which improved gas exchange can occur. Two previous cases have been reported of persistent perfluorocarbon residua, identified on imaging years after receiving liquid ventilation therapy. We report a case of perfluorocarbon detection on a CT scan 15 years after liquid ventilation at 3 months of age, and propose the probable mechanism of its appearance. The importance of considering the imaging appearances of 'pseudo-calcifications' as a long-term sequela to perfluorocarbon liquid ventilation is emphasised.

Expansion of bone marrow-derived human mesenchymal stem/stromal cells (hMSCs) using a two-phase liquid/liquid system

BACKGROUND

Human mesenchymal stem/stromal cells (hMSCs) are at the forefront of regenerative medicine applications due to their relatively easy isolation and availability in adults, potential to differentiate and to secrete a range of trophic factors that could determine specialised tissue regeneration. To date, hMSCs have been successfully cultured in vitro on substrates such as polystyrene dishes (TCPS) or microcarriers. However, hMSC sub-cultivation and harvest typically employs proteolytic enzymes that act by cleaving important cell membrane proteins resulting in long-term cell damage. In a process where the cells themselves are the product, a non-enzymatic and non-damaging harvesting approach is desirable.

RESULTS

An alternative system for hMSC expansion and subsequent non-enzymatic harvest was investigated here. A liquid/liquid two-phase system was proposed, comprising a selected perfluorocarbon (FC40) and growth medium (DMEM). The cells exhibited similar cell morphologies compared with TCPS. Moreover, they retained their identity and differentiation potential post-expansion and post-harvest. Further, no significant difference was found when culturing hMSCs in the culture systems prepared with either fresh or recycled FC40 perfluorocarbon.

CONCLUSIONS

These findings make the FC40/DMEM system an attractive alternative for traditional cell culture substrates due to their ease of cell recovery and recyclability, the latter impacting on overall process costs. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Expansion of bone marrow-derived human mesenchymal stem/stromal cells (hMSCs) using a two-phase liquid/liquid system

BACKGROUND

Human mesenchymal stem/stromal cells (hMSCs) are at the forefront of regenerative medicine applications due to their relatively easy isolation and availability in adults, potential to differentiate and to secrete a range of trophic factors that could determine specialised tissue regeneration. To date, hMSCs have been successfully cultured in vitro on substrates such as polystyrene dishes (TCPS) or microcarriers. However, hMSC sub-cultivation and harvest typically employs proteolytic enzymes that act by cleaving important cell membrane proteins resulting in long-term cell damage. In a process where the cells themselves are the product, a non-enzymatic and non-damaging harvesting approach is desirable.

RESULTS

An alternative system for hMSC expansion and subsequent non-enzymatic harvest was investigated here. A liquid/liquid two-phase system was proposed, comprising a selected perfluorocarbon (FC40) and growth medium (DMEM). The cells exhibited similar cell morphologies compared with TCPS. Moreover, they retained their identity and differentiation potential post-expansion and post-harvest. Further, no significant difference was found when culturing hMSCs in the culture systems prepared with either fresh or recycled FC40 perfluorocarbon.

CONCLUSIONS

These findings make the FC40/DMEM system an attractive alternative for traditional cell culture substrates due to their ease of cell recovery and recyclability, the latter impacting on overall process costs. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Expansion of bone marrow-derived human mesenchymal stem/stromal cells (hMSCs) using a two-phase liquid/liquid system

BACKGROUND

Human mesenchymal stem/stromal cells (hMSCs) are at the forefront of regenerative medicine applications due to their relatively easy isolation and availability in adults, potential to differentiate and to secrete a range of trophic factors that could determine specialised tissue regeneration. To date, hMSCs have been successfully cultured in vitro on substrates such as polystyrene dishes (TCPS) or microcarriers. However, hMSC sub-cultivation and harvest typically employs proteolytic enzymes that act by cleaving important cell membrane proteins resulting in long-term cell damage. In a process where the cells themselves are the product, a non-enzymatic and non-damaging harvesting approach is desirable.

RESULTS

An alternative system for hMSC expansion and subsequent non-enzymatic harvest was investigated here. A liquid/liquid two-phase system was proposed, comprising a selected perfluorocarbon (FC40) and growth medium (DMEM). The cells exhibited similar cell morphologies compared with TCPS. Moreover, they retained their identity and differentiation potential post-expansion and post-harvest. Further, no significant difference was found when culturing hMSCs in the culture systems prepared with either fresh or recycled FC40 perfluorocarbon.

CONCLUSIONS

These findings make the FC40/DMEM system an attractive alternative for traditional cell culture substrates due to their ease of cell recovery and recyclability, the latter impacting on overall process costs. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Vitreous Substitutes: Old and New Materials in Vitreoretinal Surgery

Recent developments in vitreoretinal surgery have increased the need for suitable vitreous substitutes. A successful substitute should maintain all the physical and biochemical properties of the original vitreous, be easy to manipulate, and be long lasting. Substitutes can be gaseous or liquid, both of which have associated advantages and disadvantages related to their physical properties and use. Furthermore, new surgical techniques with smaller vitreoretinal instruments have driven the use of more viscous substitutes. In this review, we analyze and discuss the most frequently used vitreous substitutes and look ahead to future alternatives. We classify these compounds based on their composition and structure, discuss their clinical use with respect to their associated advantages and disadvantages, and analyze how new vitreoretinal surgical techniques have modified their use.

Optical Coherence Tomography Angiography Characteristics of Fovea in Residual Subfoveal Perfluorocarbon Liquid Eye

The authors report a case of optical coherence tomography angiography (OCTA) features of retina and choriocapillaris before and after the surgical removal of a subfoveal perfluorocarbon liquid (PFCL) bubble. Before the surgery, the fovea avascular zone (FAZ) of both superficial and deep inner retinal layers (SRL/DRL) dramatically enlarged. However, after the removal, the FAZ continually decreased in both layers, even becoming close to normal in size. The abnormal choriocapillaris dark areas were also undetectable. Before and after surgery, the angle of the maximum FAZ diameter constantly remained horizontal and within normal limit in the SRL, forming an oval-shaped FAZ. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:1062-1066.].

Ocular ultrasonography focused on the posterior eye segment: what radiologists should know

Abstract

Ocular B-mode ultrasonography (US) is an important adjuvant for the clinical assessment of a variety of ocular diseases. When ophthalmoscopy is not possible, mainly due to opacification of the transparent media (e.g., mature cataract or vitreous haemorrhage), US can guide the ophthalmologist in diagnosing disease and choosing treatment. The superficial location and cystic structure of the eye make US ideal for imaging of the eye. Moreover, dynamic study helps distinguish between various conditions that would otherwise be difficult to differentiate in some clinical setting, such as vitreous, retinal, and choroidal detachment. US is also good technique for detecting other pathologic conditions such as lens dislocation, vitreous haemorrhage, asteroid hyalosis, optic disc drusen, and tumors (e.g., choroidal melanoma, metastases, hemangioma). An understanding of the basic anatomy of the eye, the US technique, and common entities that affect the ocular globe will allow radiologists to offer this valuable imaging modality to patients and referring clinicians. This article focuses on the US anatomy and pathologic conditions that affect the posterior ocular segment.

Teaching points

• US is specially indicated when ocular fundus cannot be assessed on ophthalmoscopy.

• Multipurpose equipment with high-frequency transducers is optimal for imaging the eye.

• Ultrasound can reliably depict ocular anatomy and pathology as detachments and tumours.

• Dynamic examination is vital for distinguishing certain pathologic conditions as detachments.

Electronic supplementary material

The online version of this article (doi:10.1007/s13244-016-0471-z) contains supplementary material, which is available to authorized users.