Perfluorohexyloctane as a long-term vitreous tamponade in the experimental animal. Experimental perfluorohexyloctane substitution

Perfluorocarbon liquid as a short-term tamponade for managing severe open globe injuries

PURPOSE

To explore the use of perfluorocarbon liquids (PFCLs) as a short-term tamponade in a staged vitrectomy approach for managing severe open globe injuries (OGIs).

METHODS

This retrospective, interventional case series included patients undergoing 23-gauge pars plana vitrectomy with PFCL tamponade for 7-14 days (mean 11.2 ± 3.36 days), followed by secondary vitrectomy and silicone oil exchange. Key outcome measures included retinal and choroidal reattachment rates, best-corrected visual acuity (BCVA), intraocular pressure (IOP), and postoperative complications. Statistical analyses were performed using McNemar's test and Student's t-test.

RESULTS

Five eyes from five patients (mean age 55.6 ± 10.12 years; male to female ratio 4:1) were included, with a mean follow-up of 8.4 ± 4.9 months. All patients sustained zone II and III globe ruptures secondary to blunt trauma, with baseline visual acuity ranging from light perception (LP) to no light perception (NLP). Intraoperative findings included total hyphema, funnel retinal detachment, traumatic choroidal rupture (TCR), suprachoroidal hemorrhage (SCH) and extensive intraocular hemorrhage (EIH). Following PFCL removal, SCH exhibited full or partial resolution, and the posterior retina remained attached in all cases. All eyes were salvaged, and visual acuity improved to hand motion (HM) on postoperative day 1, maintaining stability throughout follow-up (P = 0.03682). No significant IOP changes were observed postoperatively (preoperative: 9.66 ± 2.38 mmHg; postoperative: 9.48 ± 3.31 mmHg, P = 0.9063). Retinal and choroidal attachment were maintained during follow-up, with no cases of phthisis bulbi, endophthalmitis, recurrent hyphema, or ocular hypertension. One patient developed corneal degeneration three months postoperatively.

CONCLUSIONS

Short-term PFCL tamponade in a staged vitrectomy may facilitates retinal and choroidal stabilization while minimizing complications, offering a viable alternative for managing severe OGIs.

Efficacy of the use of perfluorocarbon as a temporary tamponade agent in severe ocular trauma and/or complex retinopexy: a scoping review

BACKGROUND

Perfluorocarbon (PFC)possesses unique chemical properties that favor the pigment epithelium's adhesion and allows the drainage of subretinal fluid through retinal holes present in retinal detachment cases. However, PFC as a temporary tamponade agent has been limited due to its high potential for toxicity.

MAIN BODY

We conducted a scoping review regarding the use of PFC in vitreoretinal surgery as a temporary tamponade in subjects with severe ocular trauma or severe retinal detachment who received a therapeutic intervention (vitrectomy via posterior approach with the use of PFC as a temporary tamponade), compared to vitrectomy without the use of PFC as a temporary tamponade. Outcomes of interest were retinal reattachment, visual acuity (VA), postoperative complications and retinal toxicity. The search was performed in Medline, Medline In-Process & Other Non-Indexed Citations, Medline Daily Update, Embase databases. Reference lists from relevant review articles were also included. Two hundred thirty-eight studies were found, with no duplicate entries. In the first selection, 230 articles were eliminated; in the second selection, 6 additional articles were discarded. In total, 8 articles were obtained in this review. Two selected articles corresponded to animal studies and 6 to studies in humans. Regarding study design, 5 were case series, and 1 was a cohort study.

CONCLUSION

PFC as a short-term tamponade had high rates of reapplication, improved VA, and the most frequent adverse effects were reversible after PFC withdrawal. Nonetheless, the quality of the studies was poor. Studies with more rigorous methodologies are needed to determine visual and structural outcomes and potential risks of PFC use as a temporary tamponade in vitreoretinal surgery.

Deciphering the Action of Perfluorohexyloctane Eye Drops to Reduce Ocular Discomfort and Pain

Perfluorohexyloctane (F6H8) eyedrops have been recently introduced in Europe as a product to treat dry eye disease, based on its ability to reduce tear film instability in Meibomian gland dysfunction and evaporative dry eye disease, although its mechanism of action is still unknown. In the present pilot study, we evaluated the effects of the ocular instillation of a single drop of commercial F6H8 eyedrops in 20 healthy humans (9 women/11 men), measuring: (a) Corneal surface temperature (CST) from infrared video images; (b) tear volume using phenol red threads; (c) blinking frequency; and (d) ocular surface sensations (cold, dryness, pricking, foreign body, burning, itching, gritty, eye fatigue, watering eyes, and light-evoked discomfort sensations; scored using 10 cm Visual Analog Scales), before and 5–60 min after F6H8 or saline treatment. CST decreased and tearing and blinking frequency increased significantly after F6H8 but not after saline solution. When applied unilaterally, CST decreased only in the F6H8-treated eye. No sensations were evoked after F6H8 or saline. The corneal surface temperature reduction produced by topical F6H8 does not evoke conscious ocular sensations but is sufficient to increase the activity of corneal cold thermoreceptors, leading to an increased reflex lacrimation and blinking that may relieve dry eye condition thus reducing ocular discomfort and pain.

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.

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

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

Unexplained Visual Loss After Silicone Oil Removal: A 7-Year Retrospective Study

Introduction

Unexplained visual loss after removal of silicone oil from the eye has been described. The purpose of this study is to determine the incidence of unexplained loss of visual acuity after SO removal and to provide possible explanations for this phenomenon.

Methods

This retrospective study included patients that underwent vitreoretinal surgery, at Centro Hospitalar São João, between January of 2012 and October of 2018. Inclusion criterion was vitreoretinal surgery in which the chosen endotamponade was SO, followed by removal of SO and exchange with balanced salt solution (BSS) or air. After SO removal, patients with documented loss of best corrected visual acuity (BCVA) on two or more Snellen lines were analyzed and patients in which the cause of the visual loss was identified, namely OHT (intraocular pressure > 21 mmHg), retinal re-detachment, glaucoma, retinal proliferative membrane formation, or corneal decompensation, were excluded. All patients with unexplained visual loss underwent spectral domain optical coherence tomography (SD-OCT) to exclude causes of visual reduction such as cystoid macular edema, epiretinal membrane, or ellipsoid/interdigitation zone disruption. A p value less than 0.05 was considered statistically significant.

Results

A total of 46 eyes underwent SO tamponade and SO removal during the study period. In 34.8% of the cases (n = 16) there was visual acuity loss in at least two Snellen lines. Of 46 eyes, 23.9% (n = 11) showed vision loss due to known secondary causes. Unexplained loss of visual acuity after SO removal occurred in 10.9% of cases. OHT during silicone endotamponade (p = 0.046) and silicone emulsification (p = 0.001) were identified as factors associated with unexplained visual loss after SO removal.

Conclusion

Unexplained loss of visual acuity after SO removal occurred in 10.9% of cases. OHT during silicone endotamponade and SO emulsification were identified as important factors in the ethology of this phenomenon.

Perfluorodecalin Versus Densiron 68 Heavy Silicone Oil in the Management of Inferior Retinal Detachment Recurrence

BACKGROUND AND OBJECTIVE

To assess the efficacy of perfluorodecalin (PFD) or Densiron 68 heavy silicone oil (HSO) in the management of inferior complex retinal detachment recurrence.

PATIENTS AND METHODS

A retrospective, comparative consecutive case series study. Twenty-four eyes of 24 patients affected by inferior complex retinal detachment recurrence underwent pars plana vitrectomy with PFD or HSO as endotamponade. All patients recruited were affected by complicated inferior retinal detachments and had already undergone at least one vitreoretinal procedure. The primary endpoint was anatomical success with primary and secondary surgery. The secondary endpoints were functional outcome and inflammatory complications.

RESULTS

Out of 24 cases of inferior retinal detachment recurrence, 12 were tamponed with PFD (PFD group) and 12 with HSO (D68 group). Retinal reattachment rate at first surgery was 50% for the D68 group and 66.6% for the PFD group. Final reattachment rate after two or more surgical operations was 91.6% for the PFD group and 83.3% for the D68 group. Best-corrected visual acuity improved in both groups from a mean of 1.00 logMAR (20/200; standard deviation [SD]: 1) to 0.60 logMAR (20/80; SD: 0.3), and from a mean of 1.81 logMAR (20/2000; SD: 1.1) to a mean of 2.00 logMAR (20/2,000; SD:1) for the PFD and D68 groups, respectively.

CONCLUSION

Both the endotamponades used showed good results in solving inferior retinal detachment recurrence with a slightly better rate in the PFD group, but it was not statistically significant (P > .05). [Ophthalmic Surg Lasers Imaging Retina. 2019;50:274-280.].

Effects of Perfluorobutylpentane (F4H5) on Corneal Endothelial Cells

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

Comparative assessment of intraocular inflammation following standard or heavy silicone oil tamponade: a prospective study

PURPOSE

To evaluate the inflammation associated with the use of standard silicone oil (polydimethylsiloxane; PDMS) and heavy silicone oil (HSO) Densiron-68™ in patients undergoing vitrectomy for retinal detachment.

MATERIALS AND METHODS

A prospective study was performed involving 35 patients scheduled to undergo vitrectomy for retinal detachment. Patients received PDMS or Densiron-68™ HSO according to superior or inferior retinal localization of the tears, respectively. For assessing the inflammation, prostaglandin E2 (PGE₂ ) and interleukin-1α (IL-1α) levels were evaluated in the aqueous.

RESULTS

Thirty-five eyes of 35 patients completed the study: 20 eyes received HSO, and 15 eyes received PDMS. The mean aqueous PGE₂ level was significantly higher in HSO patients than in PDMS patients (869.16 ± 242.83 pg/ml versus 369.38 ± 209.7 pg/ml, respectively; p < 0.0001). The mean aqueous IL-1α level was also significantly higher in HSO patients than in PDMS patients (81.40 ± 36.9 pg/ml versus 40.8 ± 32.5 pg/ml, respectively; p = 0.002). In HSO, a moderate positive correlation between the endotamponade duration and both PGE₂ (r = 0.44; p = 0.05) and IL-1α (r = 0.48; p = 0.033) levels was observed. In PDMS, a strong positive correlation between the endotamponade duration and both PGE₂ (r = 0.89; p < 0.0001) and IL-1α (r = 0.68; p = 0.006) levels was observed.

CONCLUSION

Although both HSO and PDMS yielded favourable success rates in the surgical treatment of complicated retinal detachments, HSO triggered a more severe inflammatory reaction, in a time-dependent manner.

The Effect of Vitrectomy Infusion Solutions on Postoperative Electroretinography and Retina Histology

Purpose

A prospective, randomised, masked study comparing three different intraocular infusion solutions used during vitrectomy on postoperative electroretinography (ERG) and retinal histology of rabbit eyes.

Methods materials and animals

Twelve rabbit eyes were used with each group of three intraocular infusion solutions: Lactated Ringers (LR), balanced salt solution (BSS) and balanced salt solution-plus (BSS-Plus).

Results

At 24 hours postoperatively, the ERG values were 36%, 68% and 75% of the normal values for LR, BSS and BSS-Plus, respectively. At 72 hours postoperatively, the ERG values were 50%, 84% and 100% of the normal values for LR, BSS and BSS-Plus, respectively. At 72 hours postoperatively, 3/12, 10/12 and 12/12 of the vitrectomised eyes had regained normal-value ERGs for LR, BSS, and BSS-Plus eyes, respectively. At 1 week postoperatively, 4/12 and 12/12 of LR and BSS eyes, respectively, had normal ERGs. The number of LR eyes regaining normal ERG values was 4/12, 6/12 and 9/12, measured at 1, 4 and 15 weeks postoperatively, respectively.

Retina histology

At 15 weeks follow-up, histopathology was performed on several rabbit eyes. Histological examination of LR-irrigated eyes showed 2/7 normal retinas, whereas 5/7 showed changes that ranged from vacuoles in the inner retina to numerous vacuoles in both the outer and inner retina with disruption of the inner nuclear layer. The histology of BSS-infused and BSS-Plus-infused rabbit eyes was normal.

Conclusion

LR solution, when used during vitrectomy, has a more prolonged negative effect on ERG than BSS and BSS-Plus. Histological changes seen in LR eyes may explain the ERG results.

A New, Heavier-Than-Water Silicone Oil: A Solution of Perfluorohexyloctane in Polydimethylsiloxane

Purpose

To prepare and explore new solutions of semifluorinated alkane in silicone oil, which have a specific gravity slightly higher than silicone oil and vitreous fluid (referred to in the following as heavier-than-water silicone oils (HWSs), and to investigate, in vitro, whether HWSs can be used to plug retina holes, while allowing dehydration of the subretinal space.

Methods

HWS solutions were prepared with silicone oil 5000 and perfluorohexyloctane (F6H8). The stability was investigated under different conditions. The viscosity was determined by means of a capillary viscometer. The surface and interface tension were measured using the ring method.

Results

HWSS are insoluble in an aqueous medium. Densiron®68 (HWS 1.06) is a transparent homogeneous liquid which is slightly heavier (1.06 g/cm3) than water and has a refractive index close to that of vitreous liquid. Densiron®68 (HWS 1.06) has a low viscosity (1480 mPas) and interface tension (40.82 mN/m), making it an effective tamponade in the surgical treatment of an inferior detached retina. In addition, the interfaces between Densiron®68 and other perfluorocarbon liquids are clearly visible. However, the interface layer between Densiron®68 and water is not clear. Finally, all HWSs are stable over the long term at ambient temperatures, as well as physically and thermally resistant.

Conclusions

Due to its physiochemical properties, Densiron®68 could meet the requirements for a heavier-than-water tamponade.

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.

Vitreous substitutes: the present and the future

Vitreoretinal surgery has advanced in numerous directions during recent years. The removal of the vitreous body is one of the main characteristics of this surgical procedure. Several molecules have been tested in the past to fill the vitreous cavity and to mimic its functions. We here review the currently available vitreous substitutes, focusing on their molecular properties and functions, together with their adverse effects. Afterwards we describe the characteristics of the ideal vitreous substitute. The challenges facing every ophthalmology researcher are to reach a long-term intraocular permanence of vitreous substitute with total inertness of the molecule injected and the control of inflammatory reactions. We report new polymers with gelification characteristics and smart hydrogels representing the future of vitreoretinal surgery. Finally, we describe the current studies on vitreous regeneration and cell cultures to create new intraocular gels with optimal biocompatibility and rheological properties.

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.

Colored perfluorocarbon liquids as novel intraoperative tools

BACKGROUND

Perfluorocarbon liquids (PFCLs) are used as intraoperative tools to stabilize the retina during vitreoretinal surgeries. Their use would be much facilitated if PFCLs were colored and not transparent. We describe the development of a colored PFCL for vitreoretinal surgeries.

METHODS

Perfluorohexyloctan (F6H8) was colored by adding a blue, biocompatible anthraquinone dye, and then mixed with perfluorodecalin (PFD) or perfluorooctane (PFO) at different volume percentages. The thus-obtained colored PFCLs were incubated with lens, lens capsule, vitreous body, and retina of enucleated porcine eyes for staining purpose and analyzed microscopically. To analyze possible interactions between colored PFCLs and silicone oil, colored PFCLs were exchanged to BSS and silicone oil respectively in enucleated pig eyes.

RESULTS

By mixing different volume% of colored F6H8 with perfluorodecalin (PFD) or perfluorooctane (PFO), colored PFCLs of different density and staining intensity were obtained. Cornea, lens, lens capsule, vitreous, and retina showed no signs of staining after incubation with colored PFCLs for 10 min. Colored PFCLs were transparent despite intense coloring, thus allowing a clear visibility of the underlying tissue. Immediately after instillation of silicone oil, the colored PFCL bubble was well-defined, and colored PFCL was easily aspirated. After 5 minutes reaction time, considerable diffusion of the dye from the PFCL bubble into the silicone oil was observed.

CONCLUSIONS

The staining intensity can be varied according to the volume% of the colored F6H8 phase. Colored PFCL is clearly visible when installed in the vitreous cavity of a pig eye, and can easily be removed. It does not stain the intraocular tissues in pig eyes. Colored PFCL can be exchanged with silicone oil. But a time-dependent diffusion of the dye into the silicone oil was observed in pig eyes, indicating that the contact should be limited.

[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.

Vitreous substitutes: a comprehensive review

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

Ocular tolerance and efficacy of short-term tamponade with double filling of polydimethyloxane and perfluoro-n-octane

Objective:

The aim of the study was to evaluate the ocular tolerance and efficacy of double filling with perfluoro-n-octane (n-C8F18) (PFO) and polydimethyloxane (PDMS) as a temporary vitreous substitute in patients with retinal detachment complicated by proliferative vitreoretinopathy (PVR).

Material and methods:

Tamponade was performed in 30 eyes of 30 patients by double filling with 30% PFO and 70% PDMS for an average of 23 (standard deviation 2.2) days. The follow-up visits were scheduled 1 week, 1 month, and 3 months after surgery. The main outcome measures were visual acuity, intraocular pressure (IOP), PVR reproliferation, and electrophysiological parameters.

Results:

The primary success rate was 80% (24/30). Fourteen patients (46.7%) had a postoperative improvement in visual acuity, 12 patients (40.0%) maintained their preoperative visual acuity, and four patients (13.3%) experienced a reduction in visual acuity. The mean postoperative IOP was 19.7 mm Hg (11–32 mm Hg); nine cases (30.0%) developed an IOP increase that was treated with topical drops and/or systemic carbonic anhydrase inhibitors. The electroretinogram (ERG) and the bright flash electroretinogram (bf ERG) parameters showed a statistically significant difference of means between 4- and 8-week follow-up visits.

Conclusion:

Our experience with double filling in selected cases of retinal detachment has been positive. No electroretinographic signs of retinal toxicity and a low incidence of PVR reproliferation were observed.

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.

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.

Heavy silicone oil versus standard silicone oil as vitreous tamponade in inferior PVR (HSO Study): design issues and implications

PURPOSE

Proliferative vitreoretinopathy (PVR) is the most important reason for blindness following retinal detachment. Presently, vitreous tamponades such as gas or silicone oil cannot contact the lower part of the retina. A heavier-than-water tamponade displaces the inflammatory and PVR-stimulating environment from the inferior area of the retina. The Heavy Silicone Oil versus Standard Silicone Oil Study (HSO Study) is designed to answer the question of whether a heavier-than-water tamponade improves the prognosis of eyes with PVR of the lower retina.

METHODS

The HSO Study is a multicentre, randomized, prospective controlled clinical trial comparing two endotamponades within a two-arm parallel group design. Patients with inferiorly and posteriorly located PVR are randomized to either heavy silicone oil or standard silicone oil as a tamponading agent. Three hundred and fifty consecutive patients are recruited per group. After intraoperative re-attachment, patients are randomized to either standard silicone oil (1000 cSt or 5000 cSt) or Densiron((R)) as a tamponading agent. The main endpoint criteria are complete retinal attachment at 12 months and change of visual acuity (VA) 12 months postoperatively compared with the preoperative VA. Secondary endpoints include complete retinal attachment before endotamponade removal, quality of life analysis and the number of retina affecting re-operation within 1 year of follow-up.

RESULTS

The design and early recruitment phase of the study are described.

CONCLUSIONS

The results of this study will uncover whether or not heavy silicone oil improves the prognosis of eyes with PVR.

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

INTRODUCTION

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSION

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

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.

Intrapulmonary perfluorooctyl bromide instillation in fetal rabbits

BACKGROUND

Instilling perfluorooctyl bromide (PFOB) into the fetal lung may lead to alveolar distension.

OBJECTIVE

The aim of the study was to evaluate the safety of PFOB instillation into fetal lungs and to determine the radiographic distribution and tissue concentration of PFOB in New Zealand white rabbits.

METHODS

Sibling fetuses of pregnant (day 27) New Zealand white rabbits were randomized to intratracheal instillation of 1 mL PFOB with tracheal ligation, instillation without ligation, and unmanipulated controls. The maternal animals were killed directly after instillation, at 3 or 6 hours (n = 10 each). For each study cohort, we determined fetal lung/body weight (FLBW) ratios, the radiographic distribution of PFOB, as well as pulmonary PFOB and water content by tissue distillation. PFOB concentrations in maternal and fetal tissues were assessed by gas chromatography.

RESULTS

The relative amount of fetal lung PFOB recovered by fractional distillation was highest in ligated (25%) and lower in unligated lungs (9%). Extrapulmonary PFOB was found in the fetal brain (2.0 +/- 0.7 ppm), but not in any other fetal or maternal tissues. Mean FLBW ratios were highest in ligated fetuses, followed by unligated fetuses and controls. PFOB partially displaced fetal lung water. PFOB was visible in the lungs of all treated fetuses. Fetal survival between manipulated and unmanipulated fetuses did not differ.

CONCLUSIONS

After prenatal intrapulmonary instillation, some PFOB remains in the lung, even if the trachea is not ligated, and may exert distending pressure on the alveoli.

Long-Term Vitreous Replacement with Perfluorohexyloctane and Silicone Oil: Preliminary Reports of a Multicentric Study

AIM

To report on the use of a combined intra-ocular tamponade with silicone oil and perfluorohexyloctane (F(6)H(8)) in the treatment of complex retinal detachment.

DESIGN

A prospective consecutive interventional case series from seven study centres.

PARTICIPANTS

69 patients presenting a retinal detachment with proliferative vitreoretinopathy (PVR) and retinal breaks of the inferior two quadrants of the fundus.

METHOD

Patients were divided into two groups: (1) 28 eyes which had not been operated on before; (2) 41 eyes affected by recurrent retinal detachment that had had unsuccessful previous surgery with silicone oil or gas tamponade. A pars plana vitrectomy, membrane peeling and -- when necessary -- a retinotomy were performed; the vitreous cavity was filled with two thirds of F(6)H(8) and one third of silicone oil 1,000 mPas (double filling, DF). The endotamponade was removed after 30-45 days (median 38) and replaced by balanced salt solution or silicone oil according to the condition of the retina.

RESULTS

Retinal reattachment was achieved in 52 out of 69 cases (75%) 6 months after removal of the DF without any endotamponade.

CONCLUSION

The DF with F(6)H(8) and silicone oil allows a good endotamponading to the inferior retina and the posterior pole. The DF appeared to be well tolerated. Further studies are necessary to evaluate whether a DF is advantageous in respect to silicone oil filling alone in case of retinal breaks and PVR of the inferior retina.

Influence on membrane-mediated cell activation by vesicles of silicone oil or perfluorohexyloctane

PURPOSE

This study was conducted to investigate whether macrophage activation through cell membrane attachment might be supported by emulsified tamponade droplets of a certain vesicle size. It has been hypothesized that emulsification of vitreous tamponades might stimulate retinal membrane formation.

METHODS

In this laboratory investigation, similarly sized vesicles of silicone oil and the partially fluorinated alkane perfluorohexyloctane (F6H8) were produced by extrusion through polycarbonate membranes. Human neutrophils were obtained from blood donors. Human monocytes were negatively isolated from mononuclear cells by depletion of other cells. Cell activation status of phagocyting blood neutrophils was measured by a chemiluminescence assay. Fluorescent attached or internalized vesicles were monitored by fluorescent microscopy. The main outcome measures were the altered activation status of monocytes after vesicle incubation and the ability of human macrophages to attach and/or internalize vesicles in vitro.

RESULTS

Extruding silicone oil through a polycarbonate membrane resulted in the production of vesicles that remained stable for at least 2 days. F6H8 vesicles had to be stabilized with an emulsifier, in this case Pluronic PE6800 or Lipoid EPC. The mean vesicle diameter was similar with both components (F6H8: 13.08+/-2.95 microm, silicone oil: 10.05+/-4.6 microm). Neutrophil activation was not influenced by either emulsifier alone or by silicone oil vesicles without emulsifier. Stabilized F6H8 vesicles had a dose-dependent influence on blood neutrophil activation. Only silicone oil vesicles together with Lipoid EPC, not Pluronic PE6800, had a comparable influence on neutrophil activation. Neutrophil activation was influenced neither by 0.125% human serum albumin (HSA) alone nor by vesicles of F6H8 or silicone oil prepared with 0.125% HSA. Monocyte cell membrane attachment of silicone fluid was two times higher than that of F6H8 fluid. F6H8/Pluronic PE6800 vesicles enhanced this process 20-fold, whereas silicone oil vesicles did not enhance cell membrane attachment significantly.

CONCLUSIONS

These in vitro data do not support the hypothesis that emulsification of the tamponades silicone oil or F6H8 in the microenvironment of the eye might easily activate neutrophils or stimulate phagocytosis by monocytes. A prerequisite is the combination of a vesicle shape of the tamponades with specific stabilizing or modifying surfactants. Emulsified tamponades stabilized by artificial surfactants, but not by the naturally occurring protein HSA, favor cell activation by cell membrane attachment.

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

BACKGROUND

To report long-term intraocular tolerance of perfluorohexyloctane (F(6)H(8)).

METHODS

F(6)H(8) was used as an endotamponade in 18 patients (9 male and 9 female) with a median age of 65 years (range, 14-82 years) and complicated pathologic conditions of the inferior fundus: rhegmatogenous retinal detachment (17 patients) and tractional retinal detachment owing to proliferative diabetic retinopathy (1 patient). In six eyes, additional proliferative vitreoretinopathy was present. The use of F(6)H(8) was primary in 2 patients, and 16 patients had had previous retinal detachment surgery (median number, 2). F(6)H(8) was left in the eye for a median duration of 8 weeks (range, 2-14 weeks).

RESULTS

The median follow-up period was 6 months (range, 3-18 months). Permanent reattachment was achieved in 10 (56%) eyes after removal of F(6)H(8). In 8 (44%) of 18 eyes, a redetachment occurred. Two eyes became phthisic. Adverse side effects included photophobia in two patients, pain in two, hypotony in four, early emulsification in one, corneal lesion in one, fibrinous membranes in five, posterior lens opacification in one, and retinal scar formation in one.

CONCLUSION

Perfluorohexyloctane provides good support to the inferior retina. Because of numerous adverse side effects, it should be considered carefully when used as a long-term tamponade. Early removal may reduce the number of side effects.

Clinical Research. Further evidence for proinflammatory nature of perfluorohexyloctane in the eye

BACKGROUND

The authors present a clinicopathological report of their initial experience with perfluorohexyloctane (F6H8), a novel semifluorinated liquid fluorocarbon developed as a long-term vitreous substitute.

METHODS

A retrospective observational review was performed of five patients in whom F6H8 had been used for management of rhegmatogenous retinal detachment. Surgical specimens taken from two patients at the time of F6H8 removal were also submitted for histopathological, immunohistochemical and electron microscopic analysis.

RESULTS

Clinical and histological analysis of the present small case series confirmed the propensity of F6H8 to emulsify, and suggested a probable biological reaction to F6H8. Surrounding and engulfing the F6H8 were numerous cells morphologically in keeping with macrophages. Immuno-histochemistry confirmed macrophage phenotype but electron microscopic evaluation showed epithelial ultra-structural features. It is suggested that the finding of macrophagic phenotype in cells with epithelial ultra-structure provides further evidence for a continuum of phenotypic differentiation of the pigment epithelial cells as part of the repair and regeneration that is the proliferative vitreo-retinopathy (PVR) response.

CONCLUSIONS

The data do not indicate any benefit of F6H8 over other perfluorocarbons for use in short-term post-operative intraocular tamponade. Although early experience suggests that F6H8 use in primary vitrectomy with minimal PVR is acceptable and produces temporary inflammatory effects only, these cases can often be successfully managed by conventional scleral buckling techniques, or vitrectomy with standard tamponading agents, without the need for F6H8 and subsequent extra surgical procedures. Furthermore in eyes already predisposed to inflammation through prior surgery and/or presence of PVR, the inflammatory effects were not insignificant. The use of F6H8 is not recommended in the clinical setting, except as part of a controlled trial subject to the approval of an ethics committee and informed consent.

Silicone oil-RMN3 mixture ("heavy silicone oil") as internal tamponade for complicated retinal detachment

PURPOSE

To evaluate the efficacy and safety of a silicone oil-RMN3 mixture ("heavy silicone oil") as heavier as water internal retinal tamponade after vitrectomy for complicated retinal detachment. The relative density of the heavier-than-water silicone oil was 1.03 g/cm3, and the viscosity was 3,800 cSt. Heavy silicone oil is designed to tamponade the inferior retina in complicated retinal detachment.

METHODS

Patients with a complicated retinal detachment involving the inferior part of the retina requiring internal tamponade with silicone oil were recruited for this prospective study. Inclusion criteria were retinal detachment secondary to proliferative vitreoretinopathy (stage > or = C2), inferior or posterior tears, or penetrating trauma. The heavy silicone oil was injected at the end of surgery after peeling of retinal membranes or retinotomy. Follow-up examinations were scheduled at 1, 3, 6 months, and 1 year after the initial surgery.

RESULTS

A total of 33 eyes of 33 patients aged from 20 to 84 years (mean, 56 +/- 18 years) were treated with heavy silicone oil. Follow-up ranged from 12 to 16 months. Rhegmatogenous retinal detachment with significant proliferative vitreoretinopathy accounted for 17 cases, inferior holes for three, and trauma with retinal detachment for three. Initial visual acuity ranged from 20/50 to hand motions. Initial retinal reattachment was achieved in all cases. Complications included increased intraocular pressure in six eyes (18%), intraocular inflammation and synechia formation in one eye (3%), a central retinal artery occlusion after heavy oil removal in one eye, and scattered retinal hemorrhages during follow-up in two eyes (6%). Significant emulsification was not observed during intraocular tamponade with heavy silicone oil. At the last follow-up, all eyes had macular attachment, and 24 eyes had a visual acuity better than or equal to 20/400.

CONCLUSIONS

The results of this prospective study show the good intraocular tolerance of heavy silicone oil as tamponade in complicated retinal detachment. Its specific gravity allows for sufficient tamponade of inferior retinal tears for at least 3 months without significant side effects.

Perfluorohexyloctane (F6H8) induces structural modifications and increases apoptosis in rat primary retinal cultures

The effects of perfluorohexyloctane (F6H8), recently investigated as a long-term artificial vitreous substitute, were studied in vitro, with the use of rat retinal cultures seeded on microporous inserts that allow the cell layer to be in contact with the material to be tested, on the apical side, and with the nutrient medium, on the basal side. After 72 h of treatment with F6H8, retinal cultures lost the characteristic two-layered organization with glial cells at the bottom and neuronal cells on top of them. They appeared to be composed of only one layer of polyhedrical, flattened, and disconnected cells. TUNEL assay revealed an evident increase in the percentage of apoptotic cells in F6H8-treated cultures (30.1 +/- 4.5), compared to control (10.3 +/- 2.6) and perfluoroctane-treated cultures (10.1 +/- 1.7). Immunolabeling of MAP-2, a protein of neuronal cytoskeleton, evidenced a marked loss of neurites. The results suggest that F6H8 is harmful to retinal cells in vitro and can therefore be potentially noxious to the retina as an artificial vitreous substitute.

Perfluorohexyloctane endotamponade for treatment of persisting macular hole

PURPOSE

To report the use of perfluorohexyloctane to endotamponade a persisting macular hole.

METHODS

A 62-year-old patient presented with persisting stage IV macular hole, after uncomplicated, but unsuccessful, pars plana vitrectomy with peeling ok the inner limiting membrane of the retina for treatment of the disorder. A second pars plana vitrectomy was performed in combination with cataract surgery, using perfluorohexyloctane as a new heavy-weight ocular endotamponading agent. No additional membrane peeling was done.

RESULTS

Four weeks later, marked emulsification of the perfluorohexyloctane and pronounced opacification of the posterior lens capsule were observed. After removal of the perfluorohexyloctane ten weeks after instillation, the macular hole was closed, and visual acuity increased from 0.1 to 0.3. The whole retinal surface was covered with a whitish amorphous membranous layer, that could partially be sucked off. After another four weeks, the membrane had mostly disappeared, and visual acuity increased to 0.5.

CONCLUSIONS

Perfluorohexyloctane merits further evaluation for ocular endotamponade in patients with persisting macular holes. Formation of epiretinal membranes needs to be thoroughly investigated.

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.

Perfluorohexyloctane endotamponade for treatment of subfoveal hemorrhage

PURPOSE

To report on the use of perfluorohexyloctane as a heavy liquid to temporarily tamponade the fovea for the prevention of recurrent massive subfoveal hemorrhage in patients with exudative age-related macular degeneration (ARMD).

METHODS

The case series comprised seven patients with acute massive subfoveal hemorrhage due to exudative ARMD. The patients underwent pars plana vitrectomy, drainage of the subretinal blood, and foveal endotamponade with perfluorohexyloctane. The perfluorohexyloctane was removed 80.4 +/- 38.1 days (median 98 days; range 22-118 days) after the primary surgery in a second pars plana intervention.

RESULTS

In six patients (85.7%) the subretinal hemorrhage removed during the first pars plana vitrectomy did not recur after removal of perfluorohexyloctane. In the seventh, however, a subretinal hemorrhage re-developed five days after release of perfluorohexyloctane. No large epiretinal membranes were observed. In six eyes (85.7%), the retina remained attached after removal of perfluorohexyloctane but in one eye proliferative vitreoretinopathy developed, with central retinal detachment. After the first pars plana vitrectomy, visual acuity increased slightly but not significantly (p = 0.25), from 0.03 +/- 0.03 to 0.05 +/- 0.07. Intraocular pressure rose from 15.0 +/- 1.9 mm Hg to 24.9 +/- 16.9 mm Hg. After a follow-up of 69.7 +/- 121.0 days after removal of the perfluorohexyloctane, final visual acuity was 0.02 +/- 0.04.

CONCLUSIONS

Perfluorohexyloctane may be a useful additional tool for preventing the recurrence of subfoveal re-bleeding in exudative ARMD.