Experimental long-term vitreous replacement with purified and nonpurified perfluorodecalin

Use of Perfluorochemicals in Li-Air Batteries: A Critical Review

As lithium-ion (Li-ion) batteries approach their theoretical limits, alternative energy storage systems that can power technology with greater energy demands must be realized. Li-metal batteries, particularly Li-air batteries (LABs), are considered a promising energy storage candidate due to their inherent lightweight and energy-dense properties. Unfortunately, LAB practicality remains hindered by inadequate oxygen solubility and diffusion rates within the electrolyte, both which are fundamental for LAB operation. Due to exceptionally high oxygen solubilities, perfluorochemicals (PFCs) have been investigated as a promising solution to this issue. Although PFCs have been reported to enhance LAB performance and longevity when implemented within the cathodic regions of LABs in several studies, the influence of this class of compounds on other components of the battery (including the anode and the electrolyte) is also highly important. This paper reviews the use of PFCs in LABs to date and discusses the performance enhancements resulting from their implementation. We identify and discuss future prospects and emerging research directions for the use of PFCs into LAB design, in the effort toward realization of high-performing LAB technologies.

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.

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.

PFOh No: Spontaneous Globe Rupture During Injection of Perfluoro-n-Octane (PFO) During Retinal Detachment Repair

The authors describe a case of spontaneous globe rupture during instillation of perfluoro-n-octane (PFO) during retinal surgery. A 71-year-old male with a macular-involving rhegmatogenous retinal detachment underwent pars plana vitrectomy. During instillation of PFO manually on a single-bore cannula by the assisting resident, spontaneous globe rupture occurred superotemporally in an area with no visible underlying structural abnormalities. Factors that led to this complication include the use of single-bore cannula, error in judgment of resistance during PFO injection, and inexperience. This is the first report of this complication without an identifiable structural abnormality predisposing patient to perforation.

Chorioretinal Toxicity of Perfluorooctane (Ala Octa): Results From 48 Surgical Procedures in Geneva

PURPOSE

To compare outcomes of patient who underwent surgery using perfluorooctane (PFO; C₈F₁₈; Ala Octa) with those who underwent surgery with perfluorodecalin (F-Decalin).

DESIGN

Retrospective, consecutive, comparative, interventional case series.

METHODS

A total of 48 eyes that underwent vitrectomy with PFO were compared to 29 eyes that underwent vitrectomy with perfluorodecalin. Two experienced surgeons performed vitrectomies at the Geneva University Eye Clinic. Visual acuity before, at 8 and 24 weeks after surgery, was documented, and spectral domain optical coherence tomography (SD-OCT) images were analyzed for abnormalities.

RESULTS

Two patients experienced severe retinal toxicity, including 1 with severe vision loss. However, no statistical differences in VA were observed between the PFO and perfluorodecalin patients. Analysis of SD-OCT images showed differences in occurrence of several abnormalities, for example, inner segment-outer segment alterations were found in 60.4% of eyes treated with PFO and in 10.3% of perfluorodecalin-treated eyes; retinal atrophic areas were found in 41.7% of PFO and in none of the perfluorodecalin eyes; inner limiting membrane contraction was found in 58.4% of PFO and in none of perfluorodecalin eyes; inner retina cystic alterations were found in 58.3% of PFO eyes and 17.2% of perfluorodecalin eyes; outer retina cystic alterations were found in 39.6% of PFO eyes and 13.8% of perfluorodecalin eyes; retinal holes were found in 14.6% of PFO eyes and in none of the perfluorodecalin eyes; and outer retinal inclusions were found in 20.8% of PFO eyes and in 3.45% of perfluorodecalin eyes.

CONCLUSIONS

Perfluorooctane caused significantly more toxic damage than perfluorodecalin. Special consideration should be given to develop a central European Union (EU) control agency for medical devices and to reevaluate safety procedures currently accepted by the EU and International Organization for Standardization for intraocular surgery.

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.

Chemical and Physical Stability of Perfluorocarbons with Laser Treatment

Physical and toxicological aspects of different perfluorocarbons and semifluorinated compounds are discussed. The urgent need for ultrapurification of perfluorocarbons is demonstrated. In vitro laser treatment simulating physiological conditions of two ultrapurified perfluorocarbons used for temporary tamponade and mechanical fixation of unfolded retina in case of giant tears, and one semifluorinated diether resulted in no detectable chemical alteration. Cytotoxic examinations of both laser treated and untreated probes showed no difference in cell proliferation.

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.

Impacts of Conformational Geometries in Fluorinated Alkanes

Research of blood substitute formulations and their base materials is of high scientific interest. Especially fluorinated microemulsions based on perfluorocarbons, with their interesting chemical properties, offer opportunities for applications in biomedicine and physical chemistry. In this work, carbon K-edge absorption spectra of liquid perfluoroalkanes and their parent hydrocarbons are presented and compared. Based on soft X-ray absorption, a comprehensive picture of the electronic structure is provided with the aid of time dependent density functional theory. We have observed that conformational geometries mainly influence the chemical and electronic interactions in the presented liquid materials, leading to a direct association of conformational geometries to the dissolving capacity of the presented perfluorocarbons with other solvents like water and possibly gases like oxygen.

Internal Osmotic Pressure as a Mechanism of Retinal Attachment in a Vitreous Substitute

In this study, the possibility of using the internal osmotic pressure of intraocular polymeric hydrogel materials to attach the retina in the repair of a retinal tear or hole was investigated. This is in contrast to the conventional methods of retinal detachment repair (intraocular gas, polydimethylsiloxane, or n-perfluorooctane), which rely on surface tension and have recognized limits. The system selected for implementation of this scheme was based on an acrylamide copolymer that was crosslinked in an aqueous solution to provide a transparent hydrogel which allowed control of the swelling pressure. Synthetic hydrogels, such as those selected here, provide an alternative to materials currently used as vitreous prostheses.

Fluorination-dependent molecular orbital occupancy in ring-shaped perfluorocarbons

Perfluorocarbons are a family of molecules consisting mainly of carbon and fluorine atoms. They have interesting chemical properties and have diverse applications in biomedicine, physical chemistry and polymer science. In this work, carbon K-edge absorption and emission spectra of liquid decalin are presented and compared to perfluorodecalin. A comprehensive picture of the electronic structure of decalin is provided based on soft X-ray absorption and emission spectroscopies. Experimental data are compared to theoretical time-dependent density functional theory for the hydrocarbon, the perfluorocarbon and the stepwise fluorinated derivatives. We observed a molecular orbital change from unoccupied to occupied orbitals for perfluorodecalin, which was induced through the fluorination process.

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.

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.

[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.

Iatrogenic retinal traumas in ophthalmic surgery

BACKGROUND

To describe the main retinal iatrogenic traumas possibly related to ophthalmic surgery and the precautions to be adopted to avoid them.

METHODS

The article reviews the main peer-reviewed literature concerning retinal injuries caused by surgically related maneuvers. Safety measures alleged to inhibit any possible iatrogenic damage are also evaluated.

RESULTS

Photochemical damage of the retina, retinal complications after strabismus surgery, retinal complications related to local anesthesia for ophthalmic surgery, retinal damage during cataract surgery and retinal damage during vitreoretinal surgery are the most common iatrogenic retinal injuries. Their incidence is related to risk factors peculiar to each condition.

CONCLUSIONS

Ophthalmic surgeons are aware that there are a number of circumstances in which several undesirable retinal iatrogenic injuries might occur, sometimes with serious consequences. This is why surgeons should take every precaution at each surgical step to avoid any possible retinal iatrogenic damage.

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.

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.

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.

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]).

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.

Perfluorocarbon-perfused vitrectomy: a new method for vitrectomy--a safety and feasibility study

PURPOSE

To evaluate the safety and feasibility of perfluorocarbon-perfused vitrectomy (PCPV) as a technique during vitrectomy for proliferative diabetic retinopathy (PDR) and rhegmatogenous retinal detachment (RRD).

METHODS

In an experimental, prospective, noncomparative and interventional study, 28 eyes of 28 patients were submitted to vitrectomy with the PCPV technique, 18 eyes with PDR and 10 with RRD. In this technique we replaced the traditional balanced saline solution (BSS) in the infusion line (conventional vitrectomy) by perfluorocarbon liquids (PCL). Some patients with PDR were treated with oxygenated PCL. Clinical evaluation, electroretinography (ERG), and endothelial cell count (ECC) were used to assess the safety of this procedure. An arbitrary grading system (grades 0-5) was used to classify the surgery and maneuvers to assess feasibility.

RESULTS

No eyes had a significant decrease in ECC, and the patients in whom we could obtain ERG postoperatively showed no significant differences from preoperative ERG. In the PDR group (using oxygenated and nonoxygenated PCL), 77.8% were graded 5/5; in the RRD group 90% were 5/5. PCPV allowed better visualization of vitreous and intraocular structures, rapid retinal reattachment, less blood in the vitreous cavity, subretinal fluid resolution, blood confinement, retinal stabilization, and easier dissection of epiretinal membranes. In all cases at least one surgical step was eliminated.

CONCLUSIONS

PCPV in humans is a safe and feasible technique. Probably in selected cases the use of PCL offers several advantages over BSS, because of their properties (gravitational forces, immiscibility with bodily fluids, and ability to transport oxygen). Prospective and comparative studies are necessary to establish formal indications and possible contraindications.

What pressure is exerted on the retina by heavy tamponade agents?

BACKGROUND

Histological changes in the retina during the use of heavy tamponade agents have been linked with the pressure on the retina caused by the increased specific gravity of the agent. This paper calculates the possible increases in pressure due to these agents and questions the validity of this argument.

METHODS

A model eye chamber was used to make measurements of the shape of F6H8 bubbles, with incrementally increasing volumes, and thus calculate the maximum possible increase in pressure under the tamponade agent.

RESULTS

The maximum increase in pressure under an F6H8 tamponade which completely fills an eye with a diameter of 2.2 cm would be 0.52 mmHg.

CONCLUSIONS

This increase in pressure is within normal diurnal pressure changes in the eye; therefore, it would seem unlikely that such an increase could cause the histological changes observed. With increasing volumes of a heavy tamponade agent, aqueous is excluded from a greater area of retina. This could account for the pathological changes reported.

The effect of specific gravity of perfluorocarbon liquid on the retina after experimental vitreous substitution

PURPOSE

To evaluate the histological changes in the retina after experimental vitreous substitution with various amounts of perfluorophenanthrene (PFPH).

METHODS

Thirty-two rabbit eyes were mechanically vitrectomized and filled up with 0.8 cc or 0.2 cc highly purified PFPH. The substance remained for 1 week (4 eyes), 2 weeks (8 eyes), 4 weeks (10 eyes) or 8 weeks (10 eyes). Eight eyes underwent the same surgical procedure without PFPH exchange to serve as a control group. A histological comparison of corresponding areas in the center and in the periphery of the inferior retina ensued.

RESULTS

After 2 weeks, nuclear drop-downs and irregularities of the outer plexiform layer and of both nuclear layers were observed centrally in the eyes with a 0.8 cc substitution. The changes proceeded to irregularities and cell loss of all retinal layers with focal areas of complete destruction of the retinal architecture after 8 weeks. In contrast, single nuclear drop-downs, wrinkling of the outer nuclear layer and cell loss in the photoreceptor layer were observed in the peripheral retina at the end of the observation period. In those eyes where 0.2 cc PFPH was exchanged nuclear drop-downs were found after 2 weeks, leading to focal thinning of the outer plexiform layer and irregularities of the outer nuclear layer after 4 weeks with an insignificant increase after 8 weeks. At this time these histological alterations were comparable with those that we observed after 2 weeks in the eyes with a 0.8 cc tamponade in a corresponding area.

CONCLUSIONS

Even high purification of PFPH does not prevent retinal damage. The different results in different areas after vitreous substitution with 0.2 cc and with 0.8 cc demonstrate that the high specific gravity of the substance may also play a role in the development of histological changes after extended tamponade.

Our experience with perfluorohexyloctane (F6H8) as a temporary endotamponade in vitreoretinal surgery

PURPOSE

To evaluate the use of F6H8 as a temporary endotamponade for complicated and special cases of retinal detachment instead of silicone oil.

METHODS

We have used F6H8 with 14 patients since February 1999. Eight suffered from rhegmatogenous retinal detachment (RRD) with multiple tears located inferiorly. Three presented inferior traction retinal detachment (TRD) under silicone oil, two suffered from ocular trauma with inferior TRD, and one had idiopathic macular hole. The substance was introduced into the eye after pars plana vitrectomy and membrane peeling if needed, and we tried to introduce as much as possible.

RESULTS

With F6H8 the retina was easily reattached in all cases, like with perfluorocarbon liquids. The postoperative view was very good. F6H8 was removed in all cases after 3-8 weeks. Anatomical success was achieved in 12 out of 14 eyes. Two eyes presented severe PVR. F6H8 entered the anterior chamber in 4 cases, but no corneal complications occurred. In one case there was a marked IOP rise due to an anterior block, treated with superior iridotomy. In two cases retinal detachment (RD) occurred in the upper part and was treated with additional surgery, F6H8 removal and silicone oil injection.

CONCLUSIONS

F6H8 seems to be a promising tamponade agent for special cases of RD.

Determination of the solubility of perfluorocarbon liquids in silicone oil in vitro and in vivo

PURPOSE

To investigate the solubility of perfluorocarbon liquids (PFCL) in silicone oil.

METHODS

Forty-eight samples of silicone oil (1,300 mPas, n = 22; 5,000 mPas, n = 26) were analyzed for dissolved fluorocarbon molecules after surgical removal from patients who had initially undergone vitreoretinal surgery with (n = 41) and as control without (n = 7) the use of perfluorodecalin in headspace gas chromatography. In vitro, the solubility of three different PFCL-perfluorooctane (PFO), perfluorodecalin (PFD), and fluoromethylcyclohexane (FMCH)-in silicone oil of various viscosities was determined. The diffusion phenomena during a direct exchange were studied.

RESULTS

In 39 of 41 silicone oil samples removed from patients who had undergone vitreoretinal surgery with the use of PFD, small amounts of dissolved perfluorocarbons could be detected. The mean value in 5,000-mPas silicone oil was 939.0 x 10-4 m/% and in 1,300-mPas silicone oil was 322.75 x10(-4) m/%. No perfluorocarbon molecules were found in seven control patients. In vitro, the following maximum solubilities in 1,000-mPas silicone oil were measured at room temperature: PFO, 3.2 m/%; PFD, 5.1 m/%; and FMCH, 10.3 m/%. The maximum values measured in 5,000-mPas silicone oil were PFO, 3.3 m/%; PFD, 5.7 m/%; and FMCH, 8.5 m/%; and in 100-mPas silicone oil were PFO, 2.4 m/%, and PFD, 5.1 m/%.

CONCLUSION

Perfluorocarbon liquids dissolve in silicone oil. This may lead to transient formation of "heavy silicone oil," but no stable heavy silicone oil can be created adding PFCL. Intraocularly, retained PFCL vanish in silicone oil and are removed during silicone oil removal.

Perfluorodecalin-induced intravitreal inflammation

OBJECTIVE

To report an unusual case of intravitreal inflammation in a human eye caused by the presence of residual perfluorodecalin in a case of giant retinal tear and retinal detachment.

METHODS

The posterior capsule of the lens, which was infiltrated with deposits, was collected during surgery. The specimen was stained with hematoxylin and eosin, with periodic acid-Schiff, and for melanin. Part of it was examined with electron microscopy. Immunohistochemical staining was performed to demonstrate CD68 antigens, cytokeratin, and glial fibrillary acid protein.

RESULTS

Vacuolated macrophages and retinal pigment epithelial cells infiltrated the posterior capsule. Electron microscopy showed the presence of membrane-lined vacuoles within the macrophages. A monolayer of epithelial cells covered the cellular infiltration.

CONCLUSION

Residual perfluorodecalin can induce an intraocular chronic macrophage response.

Polar application of test substances in an organotypic environment and under continuous medium flow: a new tissue-based test concept for a broad range of applications in pharmacotoxicology

We have established a new test concept for in vitro pharmacological trials. Our model employs tissue explants to test compounds for toxicity which arises with the metabolic interactions among different cell types. Microsurgical preparation of tissue explants avoids the destruction of the organ-specific tissue architecture. Explants were mounted in tissue carriers to improve nutrition and handling of the sample. To allow for the omission of serum supplementation of the culture medium, explants were cultured under continuous medium flow. Test substances are applied considering the polar architecture of most tissues in vivo, for example, covering the apical aspect of epithelia. In principal, all tissues obtained from any species, including man, can be used in this system. A trial application was performed with vitreous body substitutes, substances used in ophthalmology. One compound had passed cell culture tests, but caused massive blood vessel deterioration in vivo. Using our test system based on the developing renal vessel system, we could confirm, within 24 hours, severe vessel damage which resembles the injury suffered by the rabbit retina. We demonstrate that an improved tissue culture assay is a suitable tool for the detection of toxicity that remained unidentified in cell culture tests.

Biomaterials used in the posterior segment of the eye

The treatment of posterior segment eye disease and related conditions has improved greatly in recent years with the advent of new therapies, materials and devices. Vitreoretinal conditions, however, remain significant causes of blindness in the developed world. Biomaterials play a major role in the treatment of many of these disorders and the success rate of vitreoretinal surgery, especially in the repair of retinal detachment and related conditions, would increase with the introduction of new and improved materials. This review, which focuses on disorders that feature retinal detachment, briefly describes the anatomy of the eye and the nature and treatment of posterior segment eye disorders. The roles, required properties and suitability of the materials used in vitreoretinal surgery as scleral buckles, tamponade agents or drug delivery devices, are reviewed. Experimental approaches are discussed, along with the methods used for their evaluation, and future directions for biomaterial research in the posterior segment of the eye are considered.

Perfluorocarbons and semifluorinated alkanes

The introduction of perfluorocarbons (PFCs) and, more recently, semifluorinated alkanes (SFAs) has greatly facilitated vitreoretinal surgery. A distinction is made between the use of these substances as intraoperative tools and internal tamponade agents. This article reviews the physical and chemical properties of PFCs and SFAs and discusses the indications, results, and complications. The effectiveness of these substances as internal tamponade agents is discussed with reference to the specific gravity, contact angle, viscosity and ability to fill model eye chambers and the vitreous cavity. The evidence for the toxicity in animal and human is examined.

Proliferative vitreoretinopathy: an overview

Proliferative vitreoretinopathy (PVR) is still the most common cause of failure of surgery for rhegmatogenous retinal detachment, despite the substantial effort that has been devoted to better understanding and managing this condition during the past 25 years. Basic research has indicated that PVR represents scarring, the end stage of the wound-healing process that occurs after retinal detachment surgery. Medical treatment has been directed toward preventing inflammation, the first phase of the wound healing process, and inhibiting cell proliferation, the second phase. The 1983 Retina Society classification was modified in 1989 by the Silicone Study Group, whose classification differentiates between posterior and anterior forms of PVR and recognizes three patterns of proliferation: diffuse, focal, and subretinal. The anterior form has a worse prognosis than the posterior form, and its treatment requires more complex surgical procedures. In this review, risk factors and pathobiology of PVR are discussed, and management of PVR of various degrees of severity are considered.

13-cis-retinoic acid in silicone-fluorosilicone copolymer oil in a rabbit model of proliferative vitreoretinopathy

The purpose of this study was to evaluate the effect of 13-cis-Retinoic Acid (RA) in Silicone-Fluorosilicone Copolymer Oil (SiFO) in a rabbit model of proliferative vitreoretinopathy (PVR). Rabbits underwent gas-compression vitrectomy. During gas-SiFO exchange, group 1 was injected with 1 ml (10 microg ml-1) 13-cis-RA in SiFO, group 2 with 1.5 ml (9 microg 1.5 ml-1) all-trans-RA in SiFO, group 3 with 1 ml SiFO alone, and group 4 with balanced salt solution (BSS). Groups 1-4 were also injected with 0.1 ml suspension of fibroblasts (75,000 0.1 ml-1) and 0.05 ml platelet rich plasma (70,000 0.1 ml-1), and were observed for 4 weeks. Group 5 was injected with SiFO alone, group 6 with 1 ml (10 microg ml-1) 13-cis-RA in SiFO, group 7 with 1.5 ml (9 microg 1.5 ml-1) all-trans-RA in SiFO, and group 8 with BSS. After 4 weeks, groups 5-7 underwent SiFO-BSS exchange. ERG and histopathology were performed to test for retinal toxicity in groups 5-8. The incidence of traction retinal detachment at 4 weeks was: group 1, 42.9%; group 2, 36.4%; group 3, 87.5%; and group 4, 88.9%. A significant difference in the incidence of PVR was noted between treated eyes (groups 1 and 2) and control eyes (groups 3 and 4) at 2, 3, and 4 weeks (P<0.05). No significant difference in the incidence of PVR was found between groups 1 and 2 during the same observation periods. ERG and histopathological studies showed no differences between the treated and the control fellow eyes (group 5-7) after 4 weeks. 13-cis-RA in SiFO (10 microg ml-1) is as effective as all-trans-RA in SiFO (9 microg 1.5 ml-1) in controlling the incidence of PVR when used for short term retinal tamponade and does not appear to be associated with retinal toxicity.

Safety evaluation of perfluoropolyethers, liquid polymers used in barrier creams and other skin-care products

Fomblin HC products are a 'family' of high-purity perfluoropolyethers manufactured for barrier cream and other personal care applications which involve direct application to the skin. To confirm the safety of such use, representative Fomblin HC products were tested in experimental animals for acute toxicity, primary and repeated insult irritancy, sensitization and photosensitization, subacute oral toxicity and comedogenicity; mutagenicity was examined in vitro, and irritancy or sensitization was also investigated on human skin (in patch tests with volunteers). A high molecular weight Fomblin HC only was tested in rats for subacute oral toxicity and in man for dermal effects. Single oral doses of 15 g/kg body weight were without evident toxicity to rats, as were single dermal applications or an ip injection at 5 g/kg. No primary irritant action was seen in rabbits or man, and similarly there was no evidence of skin sensitization or photosensitization in guinea pigs, or sensitization in man. No mutagenic action on Salmonella strains of tester bacteria was seen. In repeat dose irritancy or oral toxicity tests in rabbits or rats, no adverse effects of Fomblin HC products were noted; in particular, daily oral administration (1000 mg/kg/day) to rats over 28 days produced no significant reaction. No comedogenic action was found. From the known chemistry of the perfluoropolyethers, the test programme reported here and the limited published data, it is concluded that the intended use of Fomblin HC products in formulations applied to human skin has a high margin of safety.

Retained perfluorodecalin after retinal detachment surgery

Liquid perfluorocarbons such as perfluorodecalin are widely used as intraoperative vitreous substitutes in certain complicated vitreoretinal conditions. Retained perfluorodecalin postoperatively has been reported to be associated with retinal damage and other complications. We report on a case of retained intraocular perfluorodecalin for eleven postoperative days after retinal detachment surgery with good anatomical and visual outcome after one year follow-up.

Perfluorocarbon heavy liquids

Perfluorocarbon heavy liquids (PFCL) facilitate the transfer of intraocular fluids and other surgical manoeuvres in the posterior segment. The indications for their use have extended since first described in the management of giant retinal tears and proliferative vitreoretinopathy. We reviewed our personal experience and experimental evidence, including adverse effects, in order to identify the current role of PFCL in vitreoretinal surgery. High-density perfluorocarbon liquids represent a major advance in vitreoretinal surgery. Clinical experience and the results of experimental investigations have demonstrated their efficacy and safety as an intraoperative device.