Experimental vitreous replacement with perfluorotributylamine

Effects of Perfluorocarbon Use during Rhegmatogenous Retinal Detachment Surgery on Postoperative Outcomes

INTRODUCTION

The aim of this study was to determine whether the use of perfluorocarbon liquid (PFCL) affects the rate of retinal re-attachments after an initial attachment by vitrectomy in eyes with rhegmatogenous retinal detachment (RRD).

METHODS

This was a retrospective, observational, multicenter study of 3,446 eyes registered in the Japanese vitreoretinal surgery treatment information database. Of these, 2,648 eyes had undergone vitrectomy as the first surgery for RRD. The re-attachment rates after the primary vitrectomy with or without PFCL were evaluated. In addition, the significance of factors affecting the re-detachments was determined by univariate and multivariate analyses. The measured outcomes were the rates of re-attachments after the primary vitrectomy with or without the use of PFCL.

RESULTS

A total of 2,362 eyes in the database were analyzed: 325 had and 2,037 did not have PFCL injected into the vitreous cavity during the vitrectomy. The rate of re-attachments was 91.5% in the PFCL group and 93.2% in the non-PFCL group (p = 0.46, χ2 test). Although there were several risk factors associated with the re-detachments in eyes without PFCL (p < 0.05, Welch's t tests, and Fisher's exact tests), they were not associated in eyes with PFCL use. However, multivariate analyses showed that there was no significant association between the use and the non-use of PFCL in the rate of re-detachments (β = -0.08, p = 0.46).

CONCLUSIONS

The use of PFCL during the initial vitrectomy for RRD does not affect the rate of re-attachments.

Use of Heavy Silicon Oil as Intraocular Tamponade for Inferior Retinal Detachment Complicated by Proliferative Vitreoretinopathy: A Multicentric Experience

INTRODUCTION

This is a multicentric study on the use of heavy silicon oil (HSO) as an intraocular tamponade for inferior retinal detachment (RD) complicated by proliferative vitreoretinopathy (PVR).

METHODS

139 eyes treated for RD with PVR were included in the study. 10 (7.2%) were affected by primary RD with inferior PVR, while 129 (92.8%) were affected by recurrent RD with inferior PVR. 102 eyes (73.9%) had received a silicon oil (SO) tamponade in a previous intervention prior to receiving HSO. Mean follow-up was 36.5 (standard deviation = 32.3) months.

RESULTS

The median interval between HSO injection and removal was 4 months (interquartile range: 3). At the time of HSO removal, the retina was attached in 120 eyes (87.6%), whereas in 17 eyes (12.4%), it had re-detached while the HSO was in situ. 32 eyes (23.2%) showed recurrent RD. A subsequent RD relapse was observed in 14.2% of cases with no RD at the time of HSO removal, and in 88.2% if an RD was present at the time of HSO removal. Advancing age showed a positive association with retinal attachment at the end of follow-up, while the risk of RD relapse at the end of the follow-up showed a significant negative association with HSO tamponade duration and with the use of SO rather than air or gas as post-HSO tamponade materials. Mean best corrected visual acuity was 1.1 logarithm of minimum angle of resolution at all follow-up time points. 56 cases (40.3%) needed treatment for elevated intraocular pressure (IOP), with which no clinically relevant variables were associated during follow-up.

CONCLUSION

HSO represents a safe and effective tamponade in cases of inferior RD with PVR. The presence of RD at the time of HSO removal is a negative prognostic factor for the development of a subsequent RD relapse. According to our findings, in cases of RD at the time of HSO removal, a short-term tamponade should definitely be avoided, in favor of SO. Special attention must be paid to the risk of IOP elevation, and patients should be closely monitored.

Main Principles of Vitrectomy Using Intraocular Tamponades - A Basic Course in Surgery

This article is intended to clearly present the basic principles for the use of intraocular tamponades in vitreous/retinal surgery in the event of retinal detachment and other pathologies using additional video footage. It examines the various gases, silicone oils and perfluorocarbon liquids with their indications, administration and in particular intraoperative handling including pitfalls and complications. Characteristic animations show the principles of use in surgery in a comprehensible way. The two lead authors dedicate this article to their teacher Prof. Dr. V.-P. Gabel, who in the early 1990s successfully established the first vitrectomy courses for ophthalmologists at Regensburg University Eye Clinic each year. Many colleagues who still work in retinal surgery today first started learning about this segment on these courses. The other coauthors participated under his supervision in annual vitrectomy wet labs run by the German Academy of Ophthalmology.

Pigmentary lesions in eyes with rhegmatogenous retinal detachment with flap tears: a retrospective observational study

We included 97 patients with unilateral rhegmatogenous retinal detachment (RRD) with posterior vitreous detachment who underwent vitrectomy, and examined pigmentary lesion (PL) characteristics around the sites of original tears using pre- and postoperative ultra-widefield scanning light ophthalmoscopy, green light fundus autofluorescence (FAF) imaging, and intraoperative digital video. If PL did not involve RRD, we used OCT to preoperatively assess any pathologic changes to the lesion. A total of 116 retinal tears (mean count, 1.2 ± 0.5; range, 1–4 per eye) were observed in the detached retina. Overall, 102 (88%), 63 (54%), 14 (12%), and 25 (22%) tears were accompanied by lattice degeneration (LD) or PL, both LD and PL, only LD, and only PL, respectively. In green FAF images, LD showed normal to mild-hyper fluorescence, whereas all PL showed hypofluorescence. On OCT, PL were located at the RPE level, while choroid abnormalities were unclear. In the retinal areas of 22 eyes, which were not affected by RRD, we observed PL without retinal tears; some were accompanied by vitreous traction and tractional retinal detachment. Pre-, intra-, and post-operative assessments of original flap tears suggested that PL might be a risk factor for RRD, developing alongside or separately from LD.

Microgels as globular protein model systems

Understanding globular protein adsorption to fluid interfaces, their interfacial assembly, and structural reorganization is not only important in the food industry, but also in medicine and biology. However, due to their intrinsic structural complexity, a unifying description of these phenomena remains elusive. Herein, we propose N-isopropylacrylamide microgels as a promising model system to isolate different aspects of adsorption, dilatational rheology, and interfacial structure at fluid interfaces with a wide range of interfacial tensions, and compare the results with the ones of globular proteins. In particular, the steady-state spontaneously-adsorbed interfacial pressure of microgels correlates closely to that of globular proteins, following the same power-law behavior as a function of the initial surface tension. However, the dilatational rheology of spontaneously-adsorbed microgel layers is dominated by the presence of a loosely packed polymer corona spread at the interface, and it thus exhibits a similar mechanical response as flexible, unstructured proteins, which are significantly weaker than globular ones. Finally, structurally, microgels reveal a similar spreading and flattening upon adsorption as globular proteins do. In conclusion, microgels offer interesting opportunities to act as powerful model systems to unravel the complex behavior of proteins at fluid interfaces.

Efficacy and Safety of Vitrectomy without Using Perfluorocarbon Liquids and Drainage Retinotomy Associated with Postoperative Positioning Based on Residual Subretinal Fluid for Rhegmatogenous Retinal Detachment

Medical records of 75 eyes from 75 consecutive patients with uncomplicated rhegmatogenous retinal detachment (RRD) who underwent pars plana vitrectomy (PPV) were analyzed. Inclusion criteria were patients with RRD who underwent primary 23- or 25-gauge PPV with air, gas, or SiO tamponade and performed by a single surgeon, no use of perfluorocarbon liquids (PFCL) and drainage retinotomy, and follow-up ≥ six months. Exclusion criteria were patients who underwent previous vitreoretinal surgery, proliferative vitreoretinopathy (PVR) more than grade B, giant tears, and encircling band associated with PPV. The main endpoint was the anatomical retinal reattachment rate after a single surgical procedure. Secondary endpoints were best-corrected visual acuity (BCVA), postoperative retinal displacement, and intraoperative and/or postoperative complications. Primary anatomical success was achieved in 97.3% of cases using this modified surgical procedure. Retinal slippage occurred only in 28.2% of patients and it was not observed in all cases of macula-on RRD. The mean logMAR of the BCVA significantly improved in 92% of patients and no intraoperative complications were observed. The results suggest that complete subretinal liquid drainage is not mandatory for all RRD cases treated with PPV and that using PFCL and performing a drainage retinotomy are not essential in eyes with primary RRD and PVR less than grade B. Postoperative positioning after PPV for uncomplicated RRD based on the presence or absence of residual subretinal fluid at the end of surgery could limit the occurrence of postoperative retinal displacement, while promoting patient compliance.

Substitutes and Colloidal System for Vitreous Replacement and Drug Delivery: Recent Progress and Future Prospective

Vitreoretinal surgeries for ocular diseases such as complicated retinal detachment, diabetic retinopathy, macular holes and ocular trauma has led to the development of various tamponades over the years in search for an ideal vitreous substitute. Current clinically used tamponade agents such as air, perfluorocarbons, silicone oil and expansile gases serve only as a short-term solution and harbors various disadvantages. However, an ideal long-term substitute is yet to be discovered and recent research emphasizes on the potential of polymeric hydrogels as an ideal vitreous substitute. This review highlights the recent progress in the field of vitreous substitution. Suitability and adverse effects of various tamponade agents in present day clinical use and biomaterials in the experimental phase have been outlined and discussed. In addition, we introduced the anatomy and functions of the native vitreous body and the pathological conditions which require vitreous replacement.

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.

Bioinspired Thermosensitive Hydrogel as a Vitreous Substitute: Synthesis, Properties, and Progress of Animal Studies

In many vitreal diseases, the surgeon removes the natural vitreous and replaces it with silicone oils, gases, or balanced salt solutions to fill the eyeball and hold the retina in position. However, these materials are often associated with complications and have properties that differ from natural vitreous. Herein, we report an extension of our previous work on the synthesis of a biomimetic hydrogel that is composed of thiolated gellan as an analogue of type II collagen and poly(methacrylamide-co-methacrylate-co-bis(methacryloyl)cystamine), a polyelectrolyte, as an analogue of hyaluronic acid. This thermosensitive hydrogel can be injected into the eye as a viscous solution at 45 °C. It then forms a physical gel in situ when it reaches body temperature, and later forms disulfide covalent crosslinks. In this article, we evaluated two different formulations of the biomimetic hydrogels for their physical, mechanical, and optical properties, and we determined their biocompatibility with several cell lines. Finally, we report on the progress of the four-month preclinical evaluation of our bio-inspired vitreous substitute in comparison to silicone oil or a balanced salt solution. We assessed the eyes with a slit-lamp examination, intraocular pressure measurements, electroretinography, and optical coherence tomography. Preliminary results are very encouraging for the continuing evaluation of our bio-inspired hydrogel in clinical trials.

[Current importance of heavy fluids as intraoperative aids in vitreoretinal surgery]

A major milestone in the treatment of complex retinal detachment was the development of heavy fluids as intraoperative short-term tamponades. Since the introduction liquid perfluorocarbons and hydrofluorocarbons are particularly noteworthy. Irrespective of the suitability of the substances in principle, the purity during the manufacturing process is a decisive factor that determines possible side effects. Also, the direct exchange with silicone oil can lead to mixing with disadvantageous results. Retinal surgeons should be informed about the properties of the tamponades used. Despite all expectations, the heavy liquids could not become established compared to silicone oil as a long-term tamponade, which is why their domain is the short-term intraoperative use.

Air-Perfused 23-Gauge Sutureless Diabetic Vitrectomy for Control of Intraoperative Bleeding during Removal of Fibrovascular Membrane

PURPOSE

To demonstrate the advantages and efficacy of an air-perfused membrane dissection to control intraoperative bleeding in 23-gauge sutureless vitrectomy for proliferative diabetic retinopathy with severe fibrovascular membranes. Meterials and Methods: A prospective, consecutive, interventional case series of 15 eyes that underwent air-perfused diabetic vitrectomy (air vitrectomy group) for removal of the membranes was compared with a retrospective, membrane-matched case series of 10 eyes that underwent conventional diabetic vitrectomy (conventional vitrectomy group). The main outcome measures were real vitrectomy time, intraoperative and postoperative complications, and anatomic and functional successes at the final examination.

RESULTS

The incidence of intraoperative retinal tears was 30% (3/10 eyes) in the conventional vitrectomy group and 20% (3/15 eyes) in the air vitrectomy group (p > 0.05). The postoperative complications such as vitreous hemorrhage or tractional retinal detachment were not common in both groups during the 6-month follow-up (p > 0.05). In addition, the final anatomic and functional success rates did not differ significantly between the groups (p > 0.05). However, the vitrectomy time was significantly shorter in the air vitrectomy group (67.0 ± 21.8 min) than in the conventional group (84.6 ± 21.1 min) (p = 0.04).

CONCLUSION

Air-perfused vitrectomy showed comparable anatomic and functional success rates and shorter surgical time, compared with conventional vitrectomy in diabetic eyes with severe fibrovascular membranes. We suppose that the shortened surgical time in the air vitrectomy group is related to less intraoperative bleeding and more efficient hemostasis.

BLINDNESS RELATED TO PRESUMED RETINAL TOXICITY AFTER USING PERFLUOROCARBON LIQUID DURING VITREORETINAL SURGERY

PURPOSE

To describe the presumed retinal toxicity after using specific batches of perfluorocarbon liquid ALA OCTA (Alamedics, Dornstadt, Germany) in pars plana vitrectomy.

METHODS

This is an observational retrospective consecutive case series analyses of patients operated on pars plana vitrectomy for retinal detachment or intraocular lens subluxation, using the 150141 or 200114 batches of perfluorocarbon liquid ALA OCTA as assistance during the surgery in a single center. Patients were included in this report if they manifested retinal toxicity signs throughout the follow-up, such as retinal and retinal pigment epithelium atrophy, disk paleness, and intensive macular fibrosis. Spectral domain optical coherence tomography (Spectralis; Heidelberg Engineering, Heidelberg, Germany) and Ultra-Wide Field 200° retinal camera (Optos P200Tx; Optos, Scotland, United Kingdom) images, electrophysiological tests, and visual fields were performed to analyze the retinal structure and functionality.

RESULTS

Seven of 80 patients showed all the described signs of toxicity, after a mean follow-up of 34.29 days (range: 10-87) since surgery. Four patients needed a second pars plana vitrectomy because of tractional retinal detachment and proliferative vitreoretinopathy, and two of them underwent a third surgery because of redetachment. All patients experienced amaurosis or central scotoma, with a final best-corrected visual acuity ranging from 20/200 to light perception.

CONCLUSION

Presumed toxic batches of perfluorocarbon liquid may cause massive retinal toxicity. A rapid suspicion, a correct traceability of surgical products, and informing health authorities are fundamental to prevent further cases of toxicity.

Primary Vitrectomy for Bullous Rhegmatogenous Retinal Detachments Due to Complex Breaks

Introduction

The role of vitrectomy for the treatment of uncomplicated retinal detachments has not been clearly defined. This study reports the results of a series of eyes with bullous rhegmatogenous retinal detachment (RRD) due to complex breaks that were managed by primary vitrectomy.

Methods

The study consisted of a consecutive series of 22 eyes (22 patients) with a bullous RRD not complicated by proliferative vitreoretinopathy (PVR) associated with large, multiple, or posterior breaks. All eyes underwent vitrectomy, injection of perfluorocarbon liquid (PFCL), cryopexy and gas tamponade as the primary procedure. Encircling scleral bands were placed in all cases. Follow-up ranged from 6 to 24 months (mean 10.9 ± 6.5 months).

Results

Anatomical retinal re-attachment was achieved in all eyes after one operation. Best-corrected final visual acuity was improved in all cases. Complications included progressive posterior subcapsular and nucleosclerotic cataract in four (22%) of the 18 phakic eyes and epiretinal membrane in one patient.

Conclusions

These results, together with the relatively low incidence of complications, lead us to conclude that this technique is an effective method for treatment of bullous RRD not complicated by PVR associated with technically difficult breaks. A controlled, prospective, randomized study would be necessary to thoroughly assess the advantages of vitrectomy over scleral buckling alone in these cases.

Experimental Vitreous Replacement with Perfluorophenanthrene

PURPOSE

We studied the toxicity of perfluorophenanthrene (PFP), used as short-, medium-, or long-term internal tamponading substance, on the rabbit choroid and retina. The aim was the check whether PFP is tolerated as a tamponade in the eye or damages the retina, and if any such damage is due to toxicity or to emulsification which may stimulate phagocytosis.

METHODS

Twenty-four right eyes of rabbits operated by vitrectomy were filled with 0.8-1 ml of PFP as retinal tamponading substance. Twelve eyes were operated by vitrectomy and filled with 0.8-1 ml of balanced salt solution as the control group. Direct and indirect ophthalmoscopy was done on the third and seventh day after surgery, then once a week. Enucleation, with histological and immunohistochemical examination, was done on the second day, then in the first, second, fourth and eighth weeks after surgery.

RESULTS AND CONCLUSIONS

Histological examination showed progressive damage of the chorioretinal tissues right from the second week: the chorioretinal structure was completely altered from the eighth week. Immunohistochemical examinations showed that glia cells were involved in the inflammation consequent to internal tamponade with PFP.

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.

Retinal layers measurements in healthy eyes and in eyes receiving silicone oil-based endotamponade

Purpose

To characterize the concordance/symmetry of each retinal layers in individuals without macular pathology and to further characterize the localization of inner retinal thinning in eyes receiving silicone oil-based endotamponade.

Methods

Retinal layers of one hundred eyes of 50 individuals without macular pathology were imaged using spectral domain optical coherence tomography (SD-OCT) and manually segmented using ImageJ software (developed by Wayne Rasband, NIH, Bethesda, MD, USA). In the second part of the study, retrospective analysis of 3028 cases of pars plana vitrectomy in University Eye Hospital Cologne, Germany, was conducted, retrieving nine patients with silicone oil-based endotamponade with no macular condition interfering retinal layers measurements. These patients had retinal detachment not involving the macula due to various conditions. In these patients, retinal layer segmentation was performed and compared with the fellow eye.

Results

There is a moderate-to-high concordance for all retinal layers between the right and the left eye of the same individual. In eyes receiving silicone oil-based endotamponade, the inner retinal layers become subsequently thinner. Ganglion cell and inner plexiform layers contribute most to this thinning, that is, 0.537 ± 0.096 mm³ compared with 0.742 ± 0.117 mm³; p = 0.006. Outer retinal layers were not affected by silicone oil-based endotamponade (p = 0.439 for the differences of calculated outer retinal layers).

Conclusion

Ganglion cell and inner retinal layers become subsequently thinner after the use of silicone oil-based endotamponade. This study advocates the use of spectral domain optical coherence tomography for patient management with silicone oil endotamponade to early detect subsequent retinal thinning.

Inflammation induced by perfluorocarbon liquid: intra- and postoperative use

Perfluorocarbon liquids (PFCLs) are useful and safe surgical tools in vitreoretinal surgery. The use of PFCL as a tamponade has been controversial due to the corneal toxicity, retinal infiltration, and inflammatory reaction in experimental studies. Several authors have studied in humans the anatomical and functional outcome and adverse effects of perfluorocarbon liquids used as short-, medium-, and long-term tamponade. PFCLs develop dispersion a few days after injection and droplets may move into the anterior chamber and cause corneal endothelial damage. When PFCLs are used as postoperative tamponades for more than one week, a foreign-body inflammatory reaction is observed in up to 30% of cases but such a reaction does not induce PVR, and it resolves after removal of PFCLs. Although most clinical studies have found no signs of retinal toxicity such as progressive visual acuity deterioration or macular anatomical changes, few performed ERG or retinal histological analysis.

Pars plana vitrectomy with medium-term postoperative perfluoro-N-octane for recurrent inferior retinal detachment complicated by advanced proliferative vitreoretinopathy

PURPOSE

To describe a series of patients with recurrent inferior retinal detachment complicated by proliferative vitreoretinopathy (PVR) treated with pars plana vitrectomy and postoperative perfluoro-n-octane (PFO).

METHODS

Consecutive patients with recurrent inferior retinal detachment and Grade C PVR were prospectively treated with 25-gauge pars plana vitrectomy and postoperative "medium-term" PFO for 2- to 3-week duration. All patients had subsequent PFO removal in a planned staged procedure.

RESULTS

Forty-four eyes of 44 patients were included. Mean follow-up time was 30.71 ± 12.92 months. Successful reattachment was achieved in 86% of eyes (38/44). Reattachment rates were statistically equivalent between eyes with and without previous scleral buckle. Reasons for redetachment were recurrent inferior PVR (four of six) and new superior break without PVR (two of six). Additional complications observed were cataract progression requiring surgery (42%), persistent intraocular pressure elevation (36%), and transient inflammation (32%). Macula-off status (P = 0.02) and persistent intraocular pressure elevation (P = 0.02) were factors associated with worse visual outcome.

CONCLUSION

Medium-term PFO was found to be an efficacious technique for operative management of recurrent inferior retinal detachments complicated by Grade C PVR. The method of primary repair (scleral buckle vs. pars plana vitrectomy) did not affect reattachment rates. Transient inflammation and intraocular pressure elevation are potential complications associated with this technique. Persistent intraocular pressure elevation was associated with worse visual outcome.

Better surgical method for removing perfluorocarbon liquids from the anterior chamber

PURPOSE

To describe a surgical method for removing perfluorocarbon liquids from the anterior chamber.

METHODS

Perfluorodecalin was noted in the anterior chamber in 2 patients after a vitreoretinal surgery was performed. We removed the perfluorodecalin by using a Rycroft cannula mounted on the tip of a tuberculin syringe with continued irrigation by means of an anterior chamber maintainer.

RESULTS

The perfluorodecalin was removed using a single intervention. We did not observe any perfluorodecalin residue in subsequent postoperative examinations in either patient.

CONCLUSIONS

The method is simple and safe, and it allows the complete removal of perfluorocarbon liquids from the anterior chamber using a single intervention.

[Perfluorocarbon liquids and vitreoretinal surgery in 2011]

Perfluorocarbon liquids (PFCLs) are one of the most innovative recent tools for vitreoretinal surgery. PFCLs are characterized by their number of carbon atoms, which has an impact on the density, viscosity, surface tension, vapor pressure, the boiling point, and the refraction index. PFCLs are routinely used because of their high gravity (double that of water) and their low viscosity. Furthermore, they are immiscible in water, optically clear with refraction indices similar to that of water, allowing visualization of an interface between the PFCL and saline. The use of intravitreally injected liquid PFCLs as adjunctive agents to vitreoretinal surgery plays an important role in facilitating retinal reattachment, especially in cases of giant retinal tear, trauma, and/or proliferative vitreoretinopathy. PFCLs are also used as intraoperative instruments to re-establish intraocular volume, assist in separating membranes adherent to the retina (in proliferative diabetic retinopathy, for example), and manage the dislocated crystalline lens and intraocular lens.

Towards an ideal biomaterial for vitreous replacement: Historical overview and future trends

Removal of the natural vitreous body from the eye and its substitution with a tamponade agent may be necessary in cases of complicated retinal detachment. Many materials have been variously proposed and tested over the years in an attempt to find an ideal vitreous substitute. This review highlights the evolution of research in the field of vitreous replacement and chronicles the main advances that have been made in such a context. The suitability and limitations of vitreous tamponade agents and substitutes in current clinical use are examined, and the future promise of experimentally tested biomaterials are described and discussed. Future trends in research are also considered and, specifically, the great potential of polymeric hydrogels is emphasized, as they seem to be very effective in closely mimicking the features of the natural vitreous and they could successfully act as long-term vitreous substitutes without inducing clinical complications in the patient's eye.

Histopathology and Ultrastructure of Rabbit Retina After Intravitreous Injection of Perfluorohexyloctane (F6H8)

PURPOSE

To describe changes in rabbit retina after intravitreous injection of perfluorohexyloctane (F6H8).

METHODS

Intravitreous injections of C3F8 were performed in the right eye of 48 male New Zealand albino rabbits. All 48 eyes were injected with C3F8. The animals were divided in three groups of 18 each. 18 eyes (6 in each group) were used as controls and 30 (10 in each group) were further injected with F6H8. Animals were sacrificed at days 15, 30, and 60 and the eyes processed for light and electron microscopy and immunohistochemistry.

RESULTS

Vitreous tracts were observed behind the lens in all groups. Epiretinal and retrolental membranes developed in most of the treated eyes. Light microscopy showed retinal vacuolization in all eyes. No significant ultrastructural changes appeared in any of them. Macrophages were observed in the inner limiting membrane.

CONCLUSIONS

Ultrastructural findings can be considered signs of good tolerance to F6H8, though the appearance of epiretinal membranes associated with the presence of macrophagic response suggests we should refrain from using F6H8 until results from clinical trials are available.

En bloc perfluorodissection for tractional retinal detachment in proliferative diabetic retinopathy

OBJECTIVE

En bloc perfluorodissection (EBPD) is a surgical dissection technique that facilitates removal of epiretinal membranes and the posterior hyaloid. It is carried out by injecting perfluorocarbon liquid between the retina and the posterior hyaloid to separate the epiretinal tissues from the subjacent retina. The objective of this study was to describe the technique and to demonstrate the applicability of using EBPD during vitrectomy in eyes with tractional retinal detachment (TRD) in proliferative diabetic retinopathy (PDR).

DESIGN

Prospective, interventional case series.

PARTICIPANTS

Fifty-seven patients (eyes) with TRD in PDR participated in the study.

METHODS

The author performed EBPD in 57 eyes (consecutive patients) during vitrectomy for TRD in severe PDR. Mean age of the patients was 42 years (range, 23-84 years). Mean surgical time was 50 minutes (range, 40-75 minutes). The group of patients was followed up for a mean of 18 months (range, 8-26 months).

MAIN OUTCOME MEASURES

Best-corrected visual acuity (BCVA), retinal status, and complications at the end of follow up.

RESULTS

None of the patients have developed ocular hypertension or undue inflammation, and anatomic success-accompanied by visual improvement (> or =2 Early Treatment Diabetic Retinopathy Study [ETDRS] lines) in 70.1% (40/57)-occurred in 100% (57/57) of eyes. In 14 eyes (24.5%), BCVA remained stable, and in 3 eyes (5.2%), BCVA decreased (> or =2 ETDRS lines). Final BCVA was 20/50 or better in 25%, between 20/60 and 20/400 in 47%, and worse than 20/400 in 28%. Complications included phthisis bulbi in 1 (1.7%) eye, iatrogenic retinal breaks in 4 (7%) eyes, vitreous hemorrhage requiring another procedure in 4 (7%) eyes, and cataract in 15 (26.3%) eyes.

CONCLUSIONS

This report demonstrates the applicability of using EBPD during vitrectomy in eyes with TRD in PDR.

A new heavy internal tamponade in vitreoretinal surgery: an in vitro study

AimTo study the solubility of perfluorohexyloctane (F6H8) in silicone oil (polydimethylsiloxane (PDMS) 1000) and to measure the viscosity and the specific gravity of the mixture obtained (heavy silicone oil or HSO tamponade) to define the ideal ratio of these components.MethodsThe solubility diagram of the mixture was obtained with the turbidimetric method, indicating the miscibility of F6H8 and silicone oil 1000 at all the useful temperatures. The viscosity was measured in steady shear conditions by using a controlled stress rheometer (Haake RS150) and a double cone/plate (DC 60/4) system, both at 25 and 37 degrees C for different volume per cent compositions of the mixture. The specific gravity was measured at 37 degrees C using a digital densimeter.ResultsA mixture of F6H8 30 v% and PDMS 70 v% was found to be transparent and stable at all the useful temperatures. By combining these proportions of the two substances, a resultant density of 1.06 g/cm(3) was obtained. The viscosity of the 30% F6H8 mixture was 203 mPa.s at 25 degrees C and 163 mPa.s at 37 degrees C respectively.ConclusionsThe ideal F6H8 and silicone oil mixture can be obtained combining 30% of F6H8 with 70% of silicone oil 1000. This mixture seems to have rheological properties useful for its use as an alternative intraocular heavy tamponade.Eye (2008) 22, 1082-1088; doi:10.1038/eye.2008.144; published online 6 June 2008.

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.

Vitreous Substitutes

Modern vitreoretinal surgery is a young science. While tremendous developments have occurred in instrument design and technique since Machemer first described vitrectomy surgery in 1973[1], the application of advanced materials concepts to the development of intra-ocular compounds is a particularly exciting area of research. To date, the development of vitreous substitutes has played a significant role in enabling the dramatic and progressive improvement in surgical outcome, but perhaps no other area of research has the potential to further improve the treatment of retinal detachment and other retinal disorders. While prior research has focused solely upon the ability of a compound to re-attach the retina, future research should seek to enable the surgeon to inhibit the development of proliferative vitreoretinopathy and re-detachment, the integration of stem-cell therapies with surgical retina, long-term delivery of medications to the posterior segment, and the promotion of more rapid and complete visual rehabilitation.

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.

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.

Effect of gravity in long-term vitreous tamponade: in vivo investigation using perfluorocarbon liquids and semi-fluorinated alkanes

PURPOSE

In order to investigate whether gravity is the reason for retinal degeneration in long-term vitreous tamponade, perfluorohexyloctane (F6H8), perfluorodecalin (PFD), and a mixture of F6H8/PFD were compared.

MATERIALS AND METHODS

Each group of 5 rabbits received a 3-month tamponade with either PFD (pure) (1.93 g/cm(3)), F6H8 (pure) (1.33 g/cm(3)), or a 1:1 mixture of F6H8/PFD (1.62 g/cm(3)). Electroretinograms (ERG) were performed pre- and postoperatively. Lower and upper retinal areas were compared using immunohistochemical methods. Transmission electron microscopy was performed to investigate alterations in the photoreceptors.

RESULTS

All three substances were tolerated well in rabbit eyes for up to 3 months. Dispersion was seen earliest with PFD and latest with pure F6H8. None of the substances demonstrated inflammatory reactions or vascular alterations. ERGs were not considerably altered with any of the substances. Histology of the retina showed alterations in the cell counts within the inner and outer nuclear layer that were not attributable to the gravity of the tamponading agent.

CONCLUSION

In contrast to previously published work, this study did not detect any tamponade-related structural damage of the retina after a 3-months tamponade in the rabbit model. Based upon this study, we conclude that gravity might not be causally linked to retinal damage.

The combined use of perfluorohexyloctane (F6H8) and silicone oil as an intraocular tamponade in the treatment of severe retinal detachment

BACKGROUND

The purpose of this study was to investigate the combined use of perfluorohexyloctane (F6H8) and 1,000-centistoke silicone oil as a long-term intraocular tamponade in the treatment of complicated retinal detachment.

METHODS

Sixty consecutive eyes affected by complicated retinal detachment with (1) retinal breaks of the lower two quadrants and severe proliferative vitreoretinopathy, (2) inferior giant retinal tear, (3) penetrating trauma or (4) choroidal detachment underwent pars plana vitrectomy using a combined internal tamponade of F6H8 and silicone oil. The double filling (DF) was removed after 40-50 days. The anatomical outcome and the complications due to the DF are reported.

RESULTS

Retinal reattachment was achieved in all but one patient. Thirty-eight (63%) eyes needed further surgery with silicone oil tamponade. Silicone oil was successfully removed in 22 eyes. Sixteen (27%) eyes had retained silicone oil at the last follow-up examination. One eye showed persistent retinal detachment despite further surgery. Main complications of the DF were recurrent retinal detachment of the upper retina in six (10%) eyes and membrane formation in 25 (42%) eyes.

CONCLUSIONS

A combined internal tamponade of F6H8 and silicone oil may be a useful tool in the treatment of complicated retinal detachment involving the lower quadrants of the retina.

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.

Perfluorohexylethan (O62) as ocular endotamponade in complex vitreoretinal surgery

PURPOSE

To investigate the safety and performance of perfluorohexylethan (O62), a partially fluorinated alkane, as an intraoperative tool and heavy ocular endotamponade in complex vitreoretinal surgery.

PATIENTS AND METHODS

In a prospective clinical study, O62 was used as a postoperative ocular endotamponade in 11 eyes of 11 patients after pars plana vitrectomy for the following inferior pathologic conditions, proliferative vitreoretinopathy (n = 8), rhegmatogenous retinal redetachment with inferior tears (n = 1), and inferior giant tear (n = 2). The median duration of the O62 tamponade was 43 days (range, 17-55 days), and the median follow-up period after removal of the tamponade was 16 months.

RESULTS

The initial postoperative retinal attachment rate was 100%. In 7 of 11 eyes, the retina remained attached during the O62 tamponade and after its removal. During the tamponade period, no epiretinal membrane formation or macular pucker was observed in these seven eyes. Recurrent retinal detachments with proliferative vitreoretinopathy developed in 4 of 11 eyes under the tamponade. The median follow-up after removal of O62 was 16 months. A secondary cataract developed in all five phakic eyes. Severe emulsification was noted in all patients starting in the second week after surgery causing a decrease of visual acuity and a significantly reduced funduscopic view. In the early postoperative period, a marked inflammatory reaction in the anterior segment was seen in all patients. Slightly whitish precipitates were noted in 2 of 11 eyes. A transient increase in intraocular pressure up to 35 mmHg was observed in 2 of 11 eyes.

CONCLUSION

O62 showed good tamponade properties for the inferior retina over 6 weeks. However, its use as a postoperative retinal tamponade is limited by its severe emulsification propensity and unclear inflammatory potential.