A new way of removing silicone oil from the surface of silicone intraocular lenses

Alternative Techniques To Remove Retained Silicone Oil Droplets On IOLs

BACKGROUND/PURPOSE

To describe several modified approaches to remove retained silicone oil droplets on intraocular lens (IOLs).

METHODS

Four novel techniques for removing retained silicone oil droplets on IOLs were described.

RESULTS

All four techniques led to an improved IOL with a good view to the posterior segment. No intraoperative or long-term postoperative complications have been seen in any of these eyes. These modified approaches are safe, efficient, low cost, and use existing vitreoretinal operating room supplies to add to the vitreoretinal surgeon's armamentarium to clear retained IOL silicone droplets.

CONCLUSION

It is advocated for having multiple techniques at the disposal of the vitreoretinal surgeon to address retained silicone oil on IOLs. Being able to use multiple techniques may not be superior than a single approach but is often necessary to accomplish the surgical goal of removing these adherent droplets.

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

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

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.

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.

Persistent anterior chamber silicone oil and myopia

A 60-year-old man experienced a marked unilateral myopic shift of 20 diopters following attempted removal of intravitreal heavy silicone oil used in the treatment of inferior proliferative vitreoretinopathy following retinal detachment. Examination revealed heavy silicone oil adherent to the corneal endothelium and forming a convex interface with the aqueous, obscuring the entire pupil. Surgical intervention was required to restore visual acuity. The case highlights the potential ocular complications associated with silicone oil migration into the anterior chamber, including corneal endothelial decompensation and a significant increase in myopia.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Removal of Silicone Oil From Intraocular Lens Using Novel Surgical Materials

PURPOSE

To design, fabricate, and evaluate novel materials to remove silicone oil (SiO) droplets from intraocular lenses (IOL) during vitreoretinal surgery.

METHODS

Three different designs were fabricated using soft lithography of polydimethylsiloxane (PDMS), three-dimensional (3D) inverse PDMS fabrication using water dissolvable particles, and atomic layer deposition (ALD) of alumina (Al₂O₃) on surgical cellulose fibers. Laboratory tests included static and dynamic contact angle (CA) measurements with water and SiO, nondestructive x-ray microcomputer tomography (micro-CT), and microscopy. SiO removal was performed in vitro and ex vivo using implantable IOLs and explanted porcine eyes.

RESULTS

All designs exhibited enhanced hydrophobicity and oleophilicity. Static CA measurements with water ranged from 131° to 160° and with SiO CA approximately 0° in 120 seconds following exposure. Nondestructive x-ray analysis of the 3D PDMS showed presence of interconnected polydispersed porosity of 100 to 300 μm in diameter. SiO removal from IOLs was achieved in vitro and ex vivo using standard 20-G vitrectomy instrumentation.

CONCLUSION

Removal of SiO from IOLs can be achieved using materials with lower surface energy than that of the IOLs. This can be achieved using appropriate surface chemistry and surface topography. Three designs, with enhanced hydrophobic properties, were fabricated and tested in vitro and ex vivo. All materials remove SiO within an aqueous environment. Preliminary ex vivo results were very promising, opening new possibilities for SiO removal in vitreoretinal surgeries.

TRANSLATIONAL RELEVANCE

This is the first report of an instrument that can lead to successful removal of SiO from the surface of IOL. In addition to the use of this instrument/material in medicine it can also be used in the industry, for example, retrieval of oil spills from bodies of water.

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.

[Complications of silicone oil tamponade]

Silicone oil tamponade is used for the management of complicated retinal detachment. Patients should be closely monitored as many complications may occur with intraocular silicone oil. Short-term complications include temporarily increased intraocular pressure and anterior segment inflammation. Long-term complications include cataract, emulsification, ocular hyper- or hypotension, keratopathy and retinal redetachment associated with proliferative vitreoretinopathy.

Removal of silicone oil droplet adhering to a silicone intraocular lens using 25-gauge instrumentation

A 36-year-old man with proliferative diabetic retinopathy who had had silicone oil tamponade and removal, silicone intraocular lens (IOL) implantation, and neodymium:YAG capsulotomy presented with blurred vision. Slitlamp examination revealed a silicone oil droplet on the posterior surface of the silicone IOL. Pars plana vitrectomy using 25-gauge instruments was performed, and the droplet was easily aspirated with the 25-gauge vitreous cutter.

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

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

Semifluorinated alkanes--primitive surfactants of fascinating properties

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

[Management of complicated retinal detachment using a heavy silicon oil as temporary tamponade]

PURPOSE

To assess the efficacy and safety of a heavy silicon oil (a silicon oil-RMN3 mixture, a mixed fluorinated and hydrocarbonated olefin) as temporary internal tamponade in selected cases of retinal detachment with inferior breaks.

PATIENTS AND METHODS

Forty-six patients were operated on (inferior and/or posterior breaks: 38; proliferative vitreoretinopathy > or =C2: 18; anterior proliferative vitreoretinopathy: 14), with a mean follow-up of 39 months. Seventeen patients were operated on with a heavy silicon oil of a 1.03 g/cm3 density and 29 patients with a silicon oil of a 1.02 g/cm3 density. Heavy silicon oil was removed in 41 patients after a mean of 9.3 weeks.

RESULTS

Anatomic success was achieved in 35 cases after a mean follow-up of 39 months. Recurrent retinal detachment with proliferative vitreoretinopathy occurred in eight cases during heavy silicon oil tamponade. The removal was difficult in three cases with the 1.02 g/cm3 density silicon oil. Complications included glaucoma (eight eyes), major emulsification (two eyes), and an intraocular inflammation reaction to topical steroids (five eyes).

CONCLUSION

Heavy silicon oil (Oxane Hd) is as safe and effective as standard silicon oil in the treatment of selected retinal detachment, but intraocular manipulations are quite difficult. A prospective study is necessary to compare the efficacy of Oxane Hd and standard silicon oil in selected cases of retinal detachment with inferior breaks and in cases of large inferior retinectomy.

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.

Interactions of perfluorocarbon liquids and silicone oil as characterized by mass spectrometry

BACKGROUND

Perfluorocarbon liquids (PFCL) are used extensively in complex vitreoretinal surgery, sometimes before the placement of silicone oil (SiO). We suspected that PFCL and SiO interact physically when in opposition, potentially making their removal more difficult. The nature of some of these interactions was explored using a mass spectrometric approach in in-vitro and in-vivo samples.

METHODS

We incubated silicone oil (1,000 or 5,000 centistokes viscosity) and PFCL [perfluoro-n-octane (PFO) or perfluorotributylamine] together in vitro for 6 months and performed electron impact ionization mass spectrometry (EIMS) on the PFCL to characterize interactions between the liquid phases. Packaged samples of PFCL served as controls. We also examined in vivo samples of PFO which had been retained in human eyes for several months prior to surgical removal.

RESULTS

Perfluorocarbon liquids packaged for surgical use all contain SiO in trace amounts, possibly as a manifestation of the processes used in their manufacture. Furthermore, all PFCLs incubated with SiO showed much more prominent contamination with SiO molecular fragments. PFCL was found in the SiO phase of eyes in which both liquids were present for extended periods of time. The EIMS analysis of in vivo samples suggested that proteins coat PFCL droplets, forming micelle-like structures.

CONCLUSION

Medical-grade PFCLs contain small amounts of SiO, and PFCLs dissolve small amounts of oil into solution over time. Interactions between retained vitreous substitutes may have clinical relevance.

Pseudophakic retinal detachment

Pseudophakic retinal detachment is a rare, but potentially serious, complication of cataract surgery. The incidence of pseudophakic retinal detachment following current surgical techniques of cataract extraction, including extracapsular cataract extraction by nuclear expression and phacoemulsification, is lower than that found after intracapsular cataract extraction. The risk of pseudophakic retinal detachment appears to be increased in myopic patients, in those patients in whom vitreous loss had occurred at the time of cataract surgery, and in patients undergoing Nd:YAG posterior capsulotomy. Most cases present to the clinician when the macula is already detached and the central vision is affected. When evaluating patients with pseudophakic retinal detachment, the fundal view is often impaired by anterior or posterior capsular opacification, reflections related to the intraocular lens, or poor mydriasis. Scleral buckling, pneumatic retinopexy, and primary pars plana vitrectomy, with or without combined scleral buckling, are the surgical techniques used to treat pseudophakic retinal detachment. Anatomical success rates are high after vitreo-retinal surgery for pseudophakic retinal detachment, although a smaller proportion of patients recover good vision following surgery.

Interaction of intraocular lenses with various concentrations of silicone oil: an experimental study

The aim of this study was to evaluate the interaction between various widely used intraocular lenses (IOLs) and silicone oils of different viscosities. Four groups of IOLs, including monoblock foldable hydrophilic acrylic IOLs (Morcher, type 92s); monoblock hydrophobic acrylic IOLs (Acrysof-SA60AT, Alcon); single-piece rigid polymethylmethacrylate (PMMA) IOLs (Intraocular Optical International-IOI-65130) and a three-piece foldable silicone optic IOL (CeeOn Edge 911A, Pharmacia UpJohn) were analyzed in vitro to determine the percentage adherence 1,000-centistoke, 1,300-centistoke or 5,000-centistokes silicone oil on the IOL optic. For each IOL type, there was no statistically significant difference in the mean silicone oil coverage (MSC) of the IOL optics for the different viscosities of silicone oil. Silicone IOLs had the highest MSC percentage (79.9%) whereas hydrophilic acrylic IOLs were the least silicone-covered IOLs (7.8%) compared to the other IOL types tested in this study. It is not the concentration of silicone oil that affects silicone oil coverage. When performing small-incision cataract surgery in patients who may require silicone oil injection, foldable hydrophilic acrylic or hydrophobic acrylic lenses should be preferred over standard foldable silicone lenses.

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.

Post cataract-intraocular lens (IOL) surgery opacification

Intraocular lens (IOL) implantation has no doubt been one of the most satisfying advances of medicine. Millions of individuals with visual disability or frank blindness from cataracts had and continue to have benefit from this procedure. It has been reported by ophthalmologists that the modern cataract-intraocular lens (IOL) surgery is safe and complication-free most of the time. This makes the watchword for any cataract surgeon to be 'implantation,' 'implantation,' 'implantation.' In the mid-1980s, as IOLs were evolving rapidly, the watchword of the implant surgeon was 'fixation,' 'fixation,' 'fixation.' Most techniques, lenses and surgical adjuncts now allow us to achieve the basic requirement for successful IOL implantation, namely long-term stable IOL fixation in the capsular bag. However despite this advancement some items 'slipped through cracks.' In this article, we would like to alert the reader to a new watchword, namely 'opacification,' 'opacification,' 'opacification.' Here we will be talking about the good, the bad, and the ugly. Examples of the 'good' include the recent successes now being achieved in reducing the incidence of posterior capsule opacification. Examples of the 'bad' include various proliferations of anterior capsule cells, problems caused by silicone oil adherence to IOLs and problems with piggyback IOLs. The 'ugly' include the sometimes striking and often visually disabling opacifications occurring on and within IOL optics, both on some modern foldable IOLs as well as a poly(methyl methacrylate) (PMMA) optic degradation occurring with some models a decade or more after implantation.

Use of perfluorohexyloctane as a long-term internal tamponade agent in complicated retinal detachment surgery

PURPOSE

To report the use of perfluorohexyloctane, a liquid semifluorinated alkane that is heavier than water, as an internal tamponade agent in surgery for complicated retinal detachments.

DESIGN

A consecutive interventional case series from three study centers.

METHODS

In 23 consecutive eyes (23 patients, 19 men and four women, mean +/- standard deviation (SD) age of 58.5 years +/- 16.1) perfluorohexyloctane was used for long-term internal tamponade. Included were eyes with complicated retinal detachment involving the lower two quadrants of the fundus. Excluded were patients with diseases in the fellow eye or severe systemic disease. A pars plana vitrectomy was performed, including membrane peeling and retinotomy where necessary.

RESULTS

The mean duration for perfluorohexyloctane being left in situ was 76 days (SD 37.64) (range, 35-202 days). Four weeks following the removal of perfluorohexyloctane 19 of the 23 patients had total reattachment of the retina; three eyes had a recurrence of retinal detachment. One patient was lost to follow-up. The mean follow-up after perfluorohexyloctane removal was 97 days (range, 48 to 169 days). Cataract formation or progression was noted in nine of the 10 eyes. There were two cases with high intraocular pressures. Dispersion into small droplets was observed as early as 3 days postoperatively in three of the 23 patients. At least 12 of the 23 patients had an obvious dispersion by the time of perfluorohexyloctane removal. There was no sign of optic atrophy, retinal necrosis, or retinal vascular occlusion.

CONCLUSION

Perfluorohexyloctane was tolerated as a long-term internal tamponade agent without obvious signs of damage to the retina or optic disk. Of all the complications noted, the most common was that of dispersion of the perfluorohexyloctane bubble into droplets.

Effect of heparin surface modification in reducing silicone oil adherence to various intraocular lenses

PURPOSE

To evaluate surface properties of various intraocular lenses (IOLs), including a newly fabricated heparin-surface-modified (HSM) silicone IOL, with special reference to their efficiency in reducing potential silicone oil adherence to the IOL optics.

SETTING

Center for Research on Ocular Therapeutics and Biodevices, Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.

METHODS

Five groups of rigid and foldable IOLs were analyzed in an in vitro test for the percentage of silicone oil adherence: a single-piece foldable hydrophilic-acrylic IOL (n = 9); a single-piece rigid poly(methyl methacrylate) (PMMA) IOL with HSM coating of the lens optic (n = 9); a 3-piece foldable silicone optic IOL with HSM coating of the optic (n = 10); a single-piece standard rigid PMMA IOL (n = 7); and a standard 3-piece foldable silicone optic IOL (n = 9). After the IOLs were immersed in water and then in silicone oil, gross photographs taken. Image analysis was performed to evaluate the percentage of silicone oil coverage of the anterior and posterior surfaces of each IOL optic.

RESULTS

The mean silicone oil coverage of the hydrophilic-acrylic IOLs was 5.6% +/- 2.5% (SD); of the HSM PMMA IOLs, 6.2% +/- 4.3%; of the HSM silicone optic IOLs, 6.7% +/- 3.2%; and of the standard PMMA IOLs, 20.3% +/- 13.3%. The mean silicone oil coverage was greatest on the standard silicone optic IOLs, 98.2% +/- 3.1%.

CONCLUSIONS

Intraocular lenses with a hydrophilic optic have less tendency toward adherence to silicone oil than more hydrophobic designs. A foldable silicone IOL with heparin surface modification can significantly reduce potential silicone oil adherence, comparable to the level achievable with the rigid HSM PMMA designs. Two new foldable IOL styles, the HSM silicone IOL and IOLs in the general class of hydrophilic-acrylic, were highly efficacious in reducing silicone oil adherence. There is now a real choice of foldable lenses for patients with actual or potential vitreoretinal diseases.

Noninvasive Raman spectroscopic identification of intraocular lens material in the living human eye

PURPOSE

To develop a safe noninvasive technique for identifying the material of intraocular lenses (IOLs) implanted in patients.

SETTING

Center for Biomedical Engineering and the Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston, Texas, USA.

METHODS

Raman spectroscopy was used to noninvasively identify the type of IOL implanted after previous cataract surgery in 9 eyes of 6 patients who were legally blind as a result of eye disease. Three IOLs were characterized: poly(methyl methacrylate) (PMMA) (n = 5), acrylic (n = 3), and silicone (n = 1). Confocal Raman spectroscopy was used with a laser power of 95 microW and exposure time of 1 second.

RESULTS

Distinct spectral peaks associated with each type of IOL were obtained. These included spectra peaks at 2840 cm(-1), 2946 cm(-1), and 3000 cm(-1) for PMMA; 2917 cm(-1), 2939 cm(-1), and 3055 cm(-1) for acrylic; and 2900 cm(-1), 2961 cm(-1), and 3048 cm(-1) for silicone. The procedure was well accepted by patients, and there were no complications.

CONCLUSIONS

The specific Raman spectra of the IOLs allowed for noninvasive determination of IOL material with the use of a safe light dose and an exposure time of 1 second.

Silicone oil-intraocular lens interaction: which lens to use?

AIM

To determine a suitable intraocular lens for implantation in patients at high risk of lens exposure to silicone oil in their lifetime.

METHODS

PMMA, AcrySof, AR40, AQUA-Sense, and Raysoft lenses were examined. Each lens was immersed for 5 minute intervals in balanced salt solution (BSS), in stained silicone oil, and again in BSS before being photographed in air and in BSS. Percentage silicone oil coverage of the lens optic was determined.

RESULTS

The mean percentage coating (MPC) for the lens biomaterials ranged from 5.2% to 21.5%. The Raysoft lens had significantly less oil coverage when statistically compared with the other lens types (p < 0.001).

CONCLUSION

A Raysoft (Rayner) lens is a suitable lens for implantation in patients who are at risk of severe vitreoretinal disease.

Solvent for removing silicone oil from intraocular lenses: experimental study comparing various biomaterials

PURPOSE

To evaluate the effectiveness of a perfluorocarbon-perfluorohexyloctane (PFHO)-in removing silicone oil from different intraocular lenses (IOLs) and determine whether any removal technique enhances the removal of silicone oil.

METHODS

Six IOL materials were analyzed: standard poly(methyl methacrylate) (PMMA), heparin-surface-modified (HSM) PMMA, AcrySof, 2 polyHEMAs with different water contents, and a second-generation SLM-2 silicone. One or 2 microL of a highly viscous silicone oil (5700 cs) was applied to the center of each IOL optic. Perfluorohexyloctane (2 mL) was then used to remove the silicone oil by 1 of 3 techniques: immersion of the IOL in PFHO; irrigation of the silicone oil with a small, blunt cannula; mechanical wiping with a PFHO-saturated Merocel swab (used only when irrigation failed). Next, each IOL was examined by light and scanning electron microscopy. The expanse of silicone oil residue remaining on the IOLs was objectively quantified using an integrated computerized analysis system combined with energy-dispersive spectrometry.

RESULTS

After application of 1 microL silicone oil, immersion in PFHO did not remove silicone oil from any IOL material. Irrigation with PFHO removed the silicone oil from the HSM PMMA and polyHEMA IOLs, but oil remained on the other lens materials. Mechanical wiping was necessary to remove the oil from the PMMA, AcrySof, and silicone IOLs. Attempts to remove 2 microL of silicone oil produced similar results. Although mechanical wiping of the AcrySof IOL removed all silicone oil, a slight residue remained on the PMMA and silicone IOLs. The PFHO irrigation removed significantly more silicone oil from the HSM PMMA than the unmodified PMMA IOL (P =.001). More silicone oil was removed from polyHEMA IOLs than from the AcrySof or silicone IOLs (P =.05).

CONCLUSION

Although PFHO can remove silicone oil, it is of limited usefulness. The effectiveness of PFHO depends on the removal technique, IOL material, and amount of silicone oil present. Based on these results, we recommend PFHO irrigation followed by mechanical wiping with a PFHO-saturated swab.

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.

Silicone oil removal from a silicone intraocular lens with perfluorohexyloctane

Silicone oil can be easily dissolved in vivo from silicone intraocular lenses by perfluorohexyloctane. Using specular microscopy, we examined the corneal endothelium in a patient with silicone lens implantation immediately after cataract surgery and 5 weeks postoperatively. There were no signs of acute or chronic toxicity to the endothelium.