ADVERSE SIDE EFFECTS WITH PERFLUOROHEXYLOCTANE AS A LONG-TERM TAMPONADE AGENT IN COMPLICATED VITREORETINAL SURGERY

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.

Heavy silicone oil tamponade: a multicentre experience

OBJECTIVE

To report multicentred use of the heavy silicone oil Densiron 68 for anatomical reattachment following rhegmatogenous retinal detachment (RRD) repair and its associated complications.

METHODS AND ANALYSIS

Patients from seven vitreoretinal units within the UK that underwent RRD repair with Densiron 68 between January 2015 and December 2019 were identified. Primary outcome measures were primary and final reattachment rate, retained Densiron and failure rate. Secondary outcome measures were duration of tamponade, final visual acuity (VA) and complications of heavy silicone oil.

RESULTS

134 eyes of 134 patients were involved in the study. Primary surgical success was achieved in 48.5%, while a final reattachment rate of 73.4% was observed. The mean duration of Densiron 68 tamponade was 139.5 days. Mean final VA was 1.01 (range 0-2.9). 8 eyes (6.0%) required long-term topical steroids for anterior uveitis, whereas none of the eyes required long-term pressure-lowering treatment. Emulsification rate was 10.7% (6 eyes).

CONCLUSION

This is the largest real-world study on Densiron 68 in the UK. Densiron 68 facilitates tamponade of inferior retinal pathology and may be considered as an option for tamponade of inferior retinal pathologies.

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.

Current Situation and Challenges in Vitreous Substitutes

Vitreo-retinal disorders constitute a significant portion of treatable ocular diseases. These pathologies often require vitreo-retinal surgery and, as a consequence, the use of vitreous substitutes. Nowadays, the vitreous substitutes that are used in clinical practice are mainly divided into gases (air, SF₆ , C₂ F₆ , C₃ F₈ ) and liquids (perfluorocarbon liquids, silicone oils, and heavy silicone oils). There are specific advantages and drawbacks to each of these, which determine their clinical indications. However, developing the ideal biomaterial for vitreous substitution continues to be one of the most important challenges in ophthalmology, and a multidisciplinary approach is required. In this sense, recent research has focused on the development of biocompatible, biodegradable, and injectable hydrogels (natural, synthetic, and smart), which also act as medium and long-term internal tamponade agents. This comprehensive review aims to cover the main characteristics and indications for use of the extensive range of vitreous substitutes that are currently used in clinical practice, before going on to describe the hydrogels that have been developed recently and which have emerged as promising biomaterials for vitreous substitution.

Intraocular Pressure Rise Linked to Silicone Oil in Retinal Surgery: A Review

Silicone oil represents the main choice for intraocular tamponade in cases of complicated retinal detachment surgery. The intraocular pressure of an eye filled with silicone oil could increase, driven by a variety of different forces, according to several mechanisms. Two main conditions have been highlighted, depending on the onset: early hypertension or late glaucoma. The different types of silicone oils and their physico-chemical properties are varied and may play a role in the determination of intraocular pressure rise. The current body of literature allows for the illustration and categorization of the incidence and risk factors, as well as the pathogenesis and the management of the early postoperative hypertension subtended by an open- and closed-angle, along with the late onset silicone oil-induced glaucoma. Understanding the leading actors on the stage of ocular pressure elevation concurrently with silicone oil application for retinal surgery could help in guiding the timely and appropriate course of treatment.

Retinal Tamponades: Current Uses and Future Technologies

Purpose of Review

In this article, the current use and limitations of existing retinal tamponades are discussed. Potential novel developments that address those limitations are subsequently highlighted, along with areas of future improvements.

Recent Findings

While retinal tamponades have existed for decades and improved the treatment of retinal detachments, many problems still exist with their use, including inadequate tamponade of the inferior retina, toxicity from retained heavy liquids, glaucoma, and keratopathy, among others. New advancements in the components of heavy liquids and vitreous substitutes aim to mitigate those issues.

Summary

Existing retinal tamponades, including perflurocarbon heavy liquids, fluorinated gases, and silicone oil, have specific limitations that cause potentially avoidable morbidity. New developments, such as heavy silicone oil, novel vitreous gels, and future avenues of approach, such as potentially reabsorbing heavy liquids may help increase our ability to treat retinal detachments with fewer complications.

Effects and safety of perfluorohexyloctane on the eye surface and corneal endothelium

OBJECTIVE

To evaluate the effects and safety of topical drops of perfluorohexyloctane (F6H8) on the ocular surface and the corneal endothelium.

METHODS

Forty-five patients (90 eyes) diagnosed with dry eye disease were recruited and prescribed treatment with F6H8 as part of a six-month prospective multicentre study. Variables in corneal staining were documented using the National Eye Institute/Industry Workshop scale. The conjunctival variables included using the Oxford scale, as well as corneal parameters, such as central corneal thickness, cell density, coefficient of variation, hexagonality, and mean cell area, at the start of the study, and at 3months and 6months. Compliance and satisfaction with the treatment were measured.

RESULTS

F6H8 drops reduced mean corneal staining based on the NEI scale in compliant patients to a mean of -0.84 ± 1.95 at 3months (P=.001) and to -1.65 ± 2.42 at 6months (P<.001). Conjunctival staining at 6months showed a mean decrease of -0.13 (P=.319). The endothelial parameters did not show a significant difference, in contrast to the central corneal thickness that showed a statistically significant decrease (545.30 ± 32.25 at the start of the study to 538.40 ± 31.36 after 6months, P=.009). At the end of the study, 46% of patients reported feeling subjectively better, 40.5% felt the same, and 13.5% felt subjectively worse.

CONCLUSIONS

Topical treatment with F6H8 for dried eye disease did not alter the measured variables of the corneal endothelium, but showed improvement in corneal staining and satisfaction.

Surgical management of diabetic tractional retinal detachments

Tractional retinal detachment is an end-stage form of diabetic retinopathy that occurs when contractile forces in the vitreous and neovascular tissue lead to the detachment of the neurosensory retina. We review the literature related to the management of this disease. Preoperative planning includes appropriate patient selection, diagnostic and prognostic imaging, and medical optimization with reduction of systemic risk factors. Use of antivascular endothelial growth factor for preoperative treatment has had significant benefits for tractional retinal detachment repair in improving surgical efficiency and outcomes. Advances in microsurgical instrumentation are discussed, with attention to small-gauge vitrectomy with improved flow dynamics, viewing strategies, and lighting allowing bimanual surgery. Special emphasis is placed on bimanual surgical technique, choice of tamponade, and the avoidance of iatrogenic damage. Complications and special considerations are further explored. Based on our compilation of relevant literature, we propose a surgical algorithm for the management of these complex patients.

Effects of Perfluorobutylpentane (F4H5) on Corneal Endothelial Cells

Purpose: To evaluate the effects of perfluorobutylpentane (F4H5) on corneal endothelial cell density (ECD) and morphology using a porcine corneal endothelial organ culture model. Materials and methods: "Split corneal buttons" were cultivated for 15 days (d) after incubation in F4H5 (15, 30, 60, and 120 min) or BSS (controls). ECD was assessed manually on d1, d8, and d15. After histological staining (trypan blue, alizarin red S) on d15 morphological changes (reformation figures, rosette formations, and alizarin red cells) were evaluated. Results: ECD was significantly reduced after incubation in F4H5 for 120 min (median ± 25%/75%-quartile; 3281 ± 43/222 cells/mm²; p = 0.046) on d15 compared to controls (3658 ± 129/296 cells/mm²), but not after shorter incubation times (15, 30, and 60 min). Morphological assessment supports these findings as reformation figures (F4H5 120 min: 10.5 ± 9.3/13.9/mm² vs. controls: 5.2 ± 2.8/7.2/mm²; p = 0.010), rosette formations (F4H5 120 min 25.566 ± 17.044/36.219/mm² vs. controls: 8.333 ± 0.000/15.667/mm²; p = 0.002), and alizarin red cells (F4H5 120 min: 38.350 ± 29.827/51.333/mm² vs. controls: 20.833 ± 10.417/25.000/mm²; p = 0.049) were significantly more prevalent after incubation in F4H5 for 120 min compared to controls. Also, F4H5 60 min showed significantly more rosette formations (25.452 ± 16.968/36.057/mm²; p = 0.006) and alizarin red cells (46.662 ± 42.420/50.903/mm²; p = 0.007), but not reformation figures (7.0 ± 2.2/1.6 %; p = 0.953). Conclusion: Short exposure (≤30 min) of porcine corneal endothelial cells to F4H5 does not have significant effects on ECD or morphological characteristics. Longer exposure times (≥60-120 min) may cause ECD decline and/or induce morphological changes.

Acute retinal toxicity associated with a mixture of perfluorooctane and perfluorohexyloctane: failure of another indirect cytotoxicity analysis

Aims

To report new information related to acute retinal toxicity of Bio Octane Plus, a mixture of 90% perfluorooctane (PFO) and 10% perfluorohexyloctane.

Methods

This retrospective, descriptive case series reports the occurrence of acute retinal toxicity after vitreoretinal surgery in which Bio Octane Plus (batch number 1605148) was used as an endotamponade. Cytotoxicity biocompatibility tests and chemical analyses by Fourier-transformed infrared (FTIR) spectroscopy and gas chromatography-mass spectrometry (GC-MS) of the presumed toxic product were performed.

Results

Four patients presented with acute severe visual loss after uneventful ocular surgery assisted by Bio Octane Plus (batch number 1605148) as endotamponade. Patients experienced extensive retinal vascular occlusion leading to retinal and optic nerve atrophy. The viability of ARPE-19 cells directly exposed to the suspect batch for 30 min was 0%. The agarose overlay method used by the manufacturer according to European Union regulations and International Organization for Standardization (ISO) International Standards failed to detect toxicity. FTIR spectroscopy showed small differences between the non-toxic and toxic batches. GC-MS analysis showed the presence of bromotributyl stannane (whose toxicity was demonstrated in the dose–response curve) only in the toxic batch of Bio Octane Plus.

Conclusion

This is the third report of retinotoxicity due to PFO in 4 years. The clinical profiles may be missed as they resemble other postsurgical complications; therefore, more cases worldwide could have gone unreported. Protocols to determine cytotoxicity of intraocular medical devices and approved by the ISO International Standards based on indirect methods have failed and should be revised to ensure safety.

Heavy silicone oil and intraocular inflammation

In the past two decades, many advances have been made in vitrectomy instrumentation, surgical techniques, and the use of different tamponade agents. These agents serve close retinal breaks, confine eventual retinal redetachment, and prevent proliferative vitreoretinopathy (PVR). Long-acting gases and silicone oil are effective internal tamponade agents; however, because their specific gravity is lower than that of the vitreous fluid, they may provide adequate support for the superior retina but lack efficacy for the inferior retina, especially when the fill is subtotal. Thus, a specific role may exist for an internal tamponade agent with a higher specific gravity, such as heavy silicone oils (HSOs), Densiron 68, Oxane HD, HWS 45-300, HWS 46-3000, and HeavySil. Some clinical evidence seems to presume that heavy tamponades are more prone to intraocular inflammation than standard silicone if they remain in the eye for several months. In this review, we discuss the fundamental clinical and biochemical/molecular mechanisms involved in the inflammatory response after the use of heavy tamponade: toxicity due to impurities or instability of the agent, direct toxicity and immunogenicity, oil emulsification, and mechanical injury due to gravity. The physical and chemical properties of various HSOs and their efficacy and safety profiles are also described.

Tamponade or filling effect: changes of forces in myopic eyes

Myopia is the most common ocular abnormality. Its high and growing prevalence has contributed to a recent surge in surgical interest in the disorder, since retinal detachment in eyes with high myopia differs from that in emmetropic eyes or eyes with low myopia. The myopic eye, because of its specific anatomy, poses special challenges that need to be overcome to ensure the appropriate use of vitreous substitutes. However, intraocular tamponades have shown great potential for revolutionizing retinal detachment surgery and vitreomacular surgery in general in myopic eyes. We provide an updated review of the clinical use of vitreous substitutes in the myopic eye, paying particular attention to analyzing the ideal function of endotamponade agents and comparing the effects of these agents on the physical and biological properties of the eye.

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

The application of perfluorocarbon liquids has been well acclaimed in vitreoretinal surgery. Its unique physical properties make it an ideal intraoperative tool to improve the efficiency and safety of surgical procedures in complicated cases. The main functions of perfluorocarbon liquids in vitreoretinal surgery include relocating and fixing the detached retina, displacing the subretinal and subchoroidal to fluid anteriorly, revealing proliferative vitreous retinopathy (PVR) for further maneuvers, protecting the macula from exposure to chemicals with potential toxicity, and assisting the removal of foreign body. The related clinical applications include retinal detachment with severe proliferative vitreoretinopathy, giant tear, diabetic retinopathy (DR), retinopathy of prematurity (ROP), and posterior dislocated crystalline and intraocular lenses. The application of perfluorocarbon liquids has been expended over the past fewer years. Several PFCLs related ocular inflammations have been observed in in vitro studies, animal studies, and clinical follow-up. The complete removal of PFCLs is recommended at the end of the surgery in most cases.

F6H8 as an Intraoperative Tool and F6H8/Silicone Oil as a Postoperative Tamponade in Inferior Retinal Detachment with Inferior PVR

Purpose. To evaluate the effectiveness and safety of perfluorohexyloctane (F6H8) for intraoperative flattening of the retina and of F6H8/silicone oil (SO) 1000 cSt as a postoperative tamponade for inferior retinal detachment with inferior proliferative vitreoretinopathy. Methods. This is a retrospective review of 22 patients who underwent pars plana vitrectomy using F6H8 as an intraoperative tool to flatten the retina. At the end of the surgery a direct partial exchange between F6H8 and SO 1000 cSt was performed, tamponing the eye with different ratios of F6H8/SO (70/30, 60/40, 50/50, 40/30, and 30/70). Anatomical and functional results and complications were evaluated over the follow-up period (mean 22.63 months). Results. F6H8 was efficacious for intraoperative flattening of the retina. Twenty-one of the 22 patients achieved a complete retinal reattachment. Postoperative visual acuity (VA) ranged from light perception to 20/70, with 72% of patients obtaining VA better than 20/400. No emulsification/inflammation was observed whatever the ratio of F6H8/SO used. With higher ratios of F6H8/SO (70/30 and 60/40) cloudiness of the tamponade was observed. A transparent mixture was present with all the other ratios. Conclusions. The surgical technique adopted is very simple and safe. The optimal F6H8/SO ratio seems to be between 50/50 and 30/70.

Perfluorocarbon-perfused 23 gauge three-dimensional vitrectomy for complicated diabetic tractional retinal detachment

Background

Perfluorocarbon liquid (PCL)-perfused vitrectomy has been shown in previous studies to be feasible, safe, and to have advantages in managing complicated cases of tractional retinal detachment. The present study had the objectives of describing the anatomical results and measuring surgical time and PCL consumption when combining PCL-perfused techniques with modern vitrectomy equipment.

Methods

A prospective, interventional consecutive case series was investigated. We enrolled patients with diabetic tractional retinal detachment, complicated by proliferative vitreoretinopathy and poor vision. A 23 gauge PCL-perfused vitrectomy was done with three-dimensional settings. During the procedure, we assessed the degree of surgical bleeding, visualization quality, and difficulty of membrane dissections. Visual acuity, intraocular pressure, and anatomical success were assessed at one and 3 months of follow-up.

Results

Twelve patients were enrolled in this study. There were no statistical significant changes in intraocular pressure and visual acuity throughout the follow-up period. Surgery was performed in a hemorrhage-free environment in almost all cases, with good visualization and low technical difficulty. The mean complete surgical time was 94.92 ± 25.03 minutes. The mean effective vitrectomy time was 22.50 ± 19.04 minutes and the mean PCL consumption was 25.08 ± 9.76 mL, with a speed of 1.11 mL/minute. Anatomical success was 67% at 3 months.

Conclusion

Although the technique proved to have some advantages in managing complicated cases of diabetic tractional retinal detachment, there was a high consumption of PCL. A redesign of the entire system is needed in order to decrease the amount of PCL needed for the technique.

Iridolenticular block in heavy silicone oil tamponade

BACKGROUND

The purpose of this study was to report the adverse effect of iridolenticular block glaucoma after vitreoretinal surgery and endotamponade with heavy silicone oil in cases of complicated retinal detachment.

METHODS

A retrospective analysis of 23 eyes of 23 patients who underwent a pars plana vitrectomy and heavy silicone oil (Densiron 68) endotamponade for repair of complex inferior retinal detachment.

RESULTS

Two patients developed high intraocular pressure postoperatively. The mechanism of secondary glaucoma in both patients was a prolapse of heavy silicone oil into the anterior chamber. When lying in a supine position for a prolonged period, the heavy silicone oil occluded the pupil, causing an iridolenticular block.

CONCLUSION

In the presence of heavy silicone oil in the anterior chamber, lying in a supine position causes the oil drop to sink, blocking the entire diameter of the pupil, and inducing an iridolenticular block with acute angle-closure glaucoma. We conclude that every case of heavy silicone oil migration into the anterior chamber should be regarded as an emergency. The possible treatment could include pupil dilation, anterior chamber irrigation, or an Nd YAG-laser iridotomy.

Semifluorinated alkanes--primitive surfactants of fascinating properties

Semifluorinated alkanes (SFAs) are diblock molecules, in which two mutually immiscible moieties, namely the hydrocarbon segment and the perfluorinated segment are bound covalently. The presence of two opposing segments within one molecule makes semifluorinated alkanes a very interesting class of compounds, which show a particular behavior both in bulk and at interfaces. Their highly asymmetric structure, arising from the incompatibility of the both constituent parts, results in surface activity of these molecules (so-called primitive surfactants) when dissolved in organic solvents, and allows for the Langmuir monolayer formation if spread at the air/water interface, despite of the absence of any polar group. Since 1984 (when SFAs have been characterized for the first time by Rabolt et al. [Rabolt JF, Russell TP, Twieg RJ. Macromolecules 1984;17:2786]), semifluorinated alkanes have been subjected to many studies. The present article reviews the results obtained so far and covers the aspects of their synthesis, properties in bulk (solutions and solid state) and applications. Special emphasis is put on the Langmuir monolayer properties and self-organization of SFAs on solid substrates.

Heavy tamponade 1: a review of indications, use, and complications

BACKGROUND

Heavier than water intraocular tamponades have several theoretical advantages over conventional tamponades, especially in the treatment of complicated retinal detachments and proliferative viteroretinopathy of the lower fundus periphery. However, initial clinical series of various heavy tamponades have reported significant complication rates. Therefore, heavy tamponades have not found widespread acceptance. Three recently developed heavy silicone oil tamponades, Oxane HD, Densiron 68, and HWS 46-3000, are much better tolerated and presently seem to enter routine clinical practice.

MATERIALS AND METHODS

Literature review of 21 publications on the clinical application of 9 different heavy tamponades (fluorosilicone, C10F18, F6H8, OL62HV, Oxane HD, O62, F6H8-silicone oil mixture, Densiron 68, and HWS 46-3000).

RESULTS

The first generation (fluorinated silicone and perfluorocarbon liquids) and second generation (partially fluorinated alkanes) of heavy tamponades were associated with relatively high complication rates, for example, tamponade emulsification, intraocular inflammation, and rise in intraocular pressure. The complication spectrum of the new generation of heavy silicone oils (Oxane HD, Densiron 68, and HWS 46-3000) seems to be comparable to conventional silicone oil tamponades while providing better support for the inferior retina and the posterior pole.

CONCLUSION

The recently developed heavy silicone oil tamponades are safe and effective tools for the use of complicated retinal detachments of the inferior fundus.

High-density silicone oil (Densiron) as a primary intraocular tamponade: 12-month follow up

BACKGROUND

The high-density silicone oil (Densiron 68), a mixture of F6H8 with silicone oil, seems to be a therapeutic option, at least in selected patients with complex inferior retinal re-detachment, where standard procedures have already failed. In an interventional case series we used Densiron as a primary endotamponade.

METHODS

Twelve eyes of 12 patients aged 31 years to 85 years with inferior complex rhegmatogenous retinal detachment with secondary proliferative vitreoretinopathy (PVR) grades CP2 to CA8 were included. Surgical techniques (pars plana vitrectomy, membrane peeling, retinotomy, retinectomy, endophotocoagulation, cryocoagulation, endotamponade) did not include a scleral buckling procedure (except one eye). Mean duration of the Densiron endotamponade was 78.3 +/- 29.74 days, with a mean follow up after removal of 400.6 +/- 85.4 days.

RESULTS

After Densiron removal, four patients (33.3%) showed a stable reattached retina without further interventions, while, in six patients (50%), recurrent retinal re-detachment appeared during endotamponade, generally within 2 months. One patient (8.3%) developed re-detachment 5 months after Densiron removal. One eye (8.3%) lost light perception due to severe intraretinal fibrosis with chronic hypotonia, despite complete retinal re-attachment. Visual acuity improved from mean logarithm of the minimum angle of resolution (logMAR) of 2.95 +/- 1.21 to 1.87 +/- 1.32 (statistically significant, P = 0.022). Side effects included temporary inflammatory reaction/fibrin accumulation (n = 2/2), moderate-to-severe intraretinal fibrosis (n = 3), elevated intraocular pressure (IOP) (n = 3), emulsification (n = 2), sterile hypopyon (n = 1), vitreous haemorrhage (n = 1) and chronic hypotony (n = 1).

CONCLUSION

Primary anatomical success rate of 33.3% was less encouraging than as expected. Especially, re-detachments within the posterior staphyloma in highly myopic patients were common during Densiron endotamponade. However, the surgical success increased to 75% after reintervention, even without the use of an additional encircling band. The observed adverse effects and the functional outcomes do not contraindicate the use of Densiron as an internal tamponade for a period of 3 months.

Long-term outcomes of heavy silicone oil tamponade for complicated retinal detachment

PURPOSE

To assess the long-term success rates and complications of heavy silicone oil tamponade (Oxane HD) in the management of complicated retinal detachment with proliferative vitreoretinopathy (PVR).

METHODS

Twenty-one eyes of 21 patients with complicated retinal detachment and PVR were included in this study. Vitreoretinal surgery with heavy silicone oil (Oxane HD) tamponade was performed in all patients. Heavy silicone oil was injected by perfluorocarbon liquid-air-silicone oil exchange, and was removed after 3 months. The main outcomes of the surgery including the success and complication rates were evaluated during the mean follow-up period of 11.4+/-0.88 months. Wilcoxon signed ranks test was used for statistical analysis of visual acuity changes. The outcomes of our study were compared with those of the previous studies.

RESULTS

All eyes had complicated retinal detachment with PVR Grade C3 or worse. Retinal detachment was rhegmatogenous in 6 eyes, secondary to previous detachment surgery in 11 eyes, secondary to proliferative diabetic retinopathy in 3 eyes, and secondary to perforating eye injury in 1 eye. The overall anatomic success rate was 80.9% at the end of the follow-up period. The overall visual success rate was 42.8%, with no statistically significant difference from baseline (p>0.05). Postoperative complications included severe reproliferation (4 eyes), intraocular pressure rise (3 eyes), anterior dislocation of silicone oil (2 eyes), posterior subcapsular cataract formation (4 eyes), vitreous hemorrhage (1 eye), rubeosis iridis (3 eyes), optic atrophy (1 eye), and ocular pain and photophobia (21 eyes).

CONCLUSIONS

According to the results of this study, vitreoretinal surgery with temporary heavy silicone oil tamponade appears to increase the anatomic success rates with minimal complication rate in cases with complicated retinal detachment and PVR.

Biocompatibility assessment of liquid artificial vitreous replacements: relevance of in vitro studies

The biocompatibility of liquid artificial vitreous replacements is generally assessed by performing tests in animal models before their clinical use, whereas in vitro experimentation is seldom carried out due to their physico-chemical characteristics. Since their introduction in vitreoretinal surgery, however, the use of some certified vitreous replacements has been discouraged after clinical trials, because of the occurrence of serious side effects. This observation suggests that the tests currently performed for biocompatibility assessment cannot fully guarantee their safety when they are used in humans. Here we review the available literature on in vitro biocompatibility testing of liquid artificial vitreous replacements and survey our own experience on the subject, obtained by using primary retinal cell cultures, seeded on micro-porous inserts. We suggest that in vitro biocompatibility assessment, conducted before experiments in animal models, could improve the required safety evaluation and decrease the risk of undesired side effects, as well as providing a beneficial reduction of animal experimentation.

[Heavy silicone oil as internal tamponade for retinal detachment: efficacy and tolerance]

INTRODUCTION

To evaluate the tolerance and efficacy of heavy silicone oil as internal tamponade for retinal detachment surgery.

PATIENTS AND METHODS

Sixty-six eyes requiring heavy silicone oil for retinal detachment, with at least 1 month follow-up, were retrospectively studied. Preoperative status, surgical technique, tolerance, and anatomical and functional results were analyzed from the patient's file. Indications for heavy silicone injection were inferior retinotomy or inferior retraction in 65% of cases. PVR grade C was present in at least 63% of cases. Retinotomy was performed in 45% of cases. An exchange procedure was performed versus DKline in 65% of cases. Mean follow-up was 7 +/- 4 months.

RESULTS

At the end of follow-up, 59% of eyes had a completely reattached retina, 32% without internal tamponade. Another surgery was necessary in 54% of cases. During follow-up, mean intraocular pressure was normal, and there was a significant intraocular inflammation in three cases (4.5%). In seven cases of the 44 ablations of heavy silicone oil, an adherence of residual bubbles was present. Redetachment occurred after ablation for anatomical success in 41% of cases. BCVA was better than 0.05 (20/400) in 54% of cases at the end of follow-up.

CONCLUSION

Heavy silicone was well tolerated and seems not to be pro-inflammatory in our study. It is a good alternative to standard silicone for inferior retinotomy and inferior breaks without PVR. It is not a treatment of inferior retraction, and is not a long-term internal tamponade. During the ablation of heavy silicone oil, adherence of residual bubbles is possible, in which case a coaxial light or an endoillumination could be needed during ablation.

First experiences with high-density silicone oil (Densiron) as an intraocular tamponade in complex retinal detachment

BACKGROUND

In this study, we evaluated the anatomic and functional outcome and intraocular adverse effects after a 3-month endotamponade with Densiron 68, a mixture of F(6)H(8) with silicone oil, in complex inferior re-detachments.

METHODS

Forty-eight eyes of 48 patients aged 27-82 years with retinal re-detachment due to proliferative vitreoretinopathy (PVR) grades CP1 to CA7 were included. Mean duration of the Densiron endotamponade was 108.7+/-66.9 days, with a mean follow-up after removal of 102.8+/-31.9 days.

RESULTS

Twenty-two patients (45.8%) showed stable retinal reattachment after Densiron removal. Fourteen patients (29.2%) developed retinal re-detachment after removal, generally within 1 month and in the upper circumference (n=8). In 11 patients (22.9%) recurrent re-detachment (inferior n=8) appeared during Densiron endotamponade. In one eye (2.1%) treatment was primarily unsuccessful. Visual acuity improved from mean logMAR 1.66+/-1.03 to 1.47+/-0.97 (not statistically significant, P=0.257). Side effects included temporary inflammatory reaction (n=10), fibrin accumulation (n=6), sterile hypopyon (n=2), vitreous hemorrhage (n=6), elevated IOP (n=5), emulsification (n=4) and chronic hypotony (n=4).

CONCLUSION

The anatomical success rate without further interventions of 45.8% (22 of 48 patients) seems unsatisfactory. However, in evaluating the potential of Densiron, it should be considered that all patients in this study had previous surgery with standard procedures, including silicone oil, which had already failed. Intraoperative laser photocoagulation of the periphery of the upper quadrants might reduce the risk of retinal re-detachments.

Anatomical and Functional Outcomes after Heavy Silicone Oil Tamponade in Vitreoretinal Surgery for Complicated Retinal Detachment

PURPOSE

To evaluate the effectiveness and safety of a heavy silicone oil (HSO) tamponade for complicated retinal detachment (RD) surgery.

DESIGN

Prospective consecutive interventional case series study.

PARTICIPANTS

The study included 26 patients with RD complicated by severe proliferative vitreoretinopathy (PVR) in the inferior quadrants.

METHODS

All patients underwent pars plana vitrectomy with an internal tamponade using HSO. This tamponade was obtained by mixing 30% by volume perfluorohexyloctane and 70% by volume silicone oil, 1000 millipascal-seconds (polydimethylsiloxane 1000).

MAIN OUTCOMES MEASURES

Anatomical and functional results and complications at 1 year of follow-up.

RESULTS

Twenty-four of 26 patients achieved anatomical success, defined as complete retinal reattachment. Postoperative visual acuity (VA) values ranged from hand movements to 20/25, with 69.2% of patients obtaining VA better than 20/400. Postoperative complications included early postoperative ocular hypertension in 30.7% of cases, which was easily controlled. Dispersion was noted in 1 case and was not felt to be significant. A cataract requiring surgical removal developed in 2 cases, and an after cataract developed in 3 cases.

CONCLUSIONS

In this pilot study, the HSO tamponade obtained by mixing 30% perfluorohexyloctane and 70% polydimethylsiloxane 1000 was associated with a high rate of anatomical success after vitrectomy in cases of RD complicated by severe PVR (greater than CP-6 and greater than CA-6 [updated Retina Society PVR classification]).