Silicone Oil Emulsification Research Articles

Intraocular silicone implant to treat chronic ocular hypotony: an in vivo trial.

The management of chronic ocular hypotony and complicated proliferative vitreoretinopathy-related retinal detachment represents a challenge. Being non-absorbable and non-biodegradable, a silicone oil implant is expected to restore the volume and the intraocular pressure of the globe, as well as to approximate the detached retina. Further advantages could be a long-term tamponade potential, absence of toxicity, and prevention of silicone oil emulsification or anterior chamber oil-prolapse. The aim of this study was to assess the histological tolerance of the silicone oil implant in a pig model. A seamless silicone balloon implant with optional surface modifications was developed. Mini pigs were used as experimental animals, and three variants of silicone implants with different surfaces were tested: uncoated, NCO-sP(EO-stat-PO) coated, and heparin-NCO-sP(EO-stat-PO) coated silicone implants. An extracapsular lens extraction was achieved via a standard phacoemulsification followed by a standard three-port vitrectomy. The implant was then placed in the posterior segment and filled with 5000 centistoke silicone oil. One month later, the pigs were euthanized, the eyes were enucleated, and histological specimens were prepared for microscopy. The analysis of the histology revealed that adverse histological changes in conjunctiva, cornea, iris, and ciliary body could be excluded in all eyes operated on regardless of which variant of implant had been employed. The retina as the implant-contacting ocular tissue showed overall good tolerance, although some inflammatory reaction and fibrous proliferation was evident in some cases. The silicone oil implant is a promising candidate and has the potential to fulfill clinical requirements to act as a long-term intraocular tamponade agent. The heparin-NCO-sP(EO-stat-PO) coating approach could lead to a novel bioactive surface for intraocular devices with excellent properties to hinder cell adhesion and protein adsorption, although further studies will be necessary to evaluate long-term biocompatibility and long-term resistance to biological attacks.

A perfluorobutylpentane (F4H5)-based solution for the removal of residual emulsified silicone oil.

The emulsification of silicone oil (SO) is associated with many complications. In this study, we investigate a new SO solvent, perfluorobutylpentane (F4H5) with 1% by volume of perfluorinated polyethers-polyethylene glycol-perfluorinated polyethers (PFPE-PEG-PFPE) triblock copolymer, for removing emulsified droplets. An invitro 3D printed model eye chamber was used to evaluate the efficiency of the three test liquids in removing SO droplets, namely saline, F4H5 and F4H5 with surfactant PFPE-PEG-PFPE. The numbers of SO droplets were quantified using a Coulter Counter. The stability of double emulsion formed was tested with a fluidic device based on electro-coalescence. Two retinal cell lines were used to test the biocompatibility of the liquids. The mean number of droplets remaining in the eye chamber after rinsing with a solution of F4H5 with surfactant was 13315±4620/ml compared to saline (23460±7595/ml; p<0.05). The double emulsion was found to be highly stable. The biocompatibility of F4H5 and the surfactant was similar to that of the saline control. By adding a small amount of surfactant, the resultant F4H5 solution is able to promote double emulsification and remove more SO droplets. Although further invivo safety studies are necessary before clinical trials, the result of our study suggests that F4H5 with surfactant is a promising Rinsing Solution for removing emulsified droplets. This work therefore translates a well-known phenomenon in emulsion science to tackle the emulsification problem observed in the routine vitreoretinal surgery.

Analysis of causative factors of high intraocular pressure after vitrectomy combined with silicon oil tamponade

Objective To analyse the causative factors of high intraocular pressure (IOP) after vitrectomy combined with silicon oil tamponade. Methods The data of 78 eyes of 78 patients who underwent pars plana vitrectomy combined with silicon oil tamponade between July 2013 and January 2015 in our hospital were retrospectively analyzed. The follow-up time was 12 months, and the high IOP was defined as IOP≥24 mmHg(1 mmHg=0.133 kPa). Statistical methods were used to analyze the possible causative factors of postoperative high IOP. Results Postoperative high IOP occurred in 27 cases (34.62%). There was no significant difference in age, gender, diabetes mellitus, previous intraocular surgery or ocular trauma between high IOP group and normal IOP group(P> 0.05). Logistic multivariate regression analysis showed that the OR values of high myopia, combined with lentectomy, emulsification of silicone oil, uveitis and time of silicon oil tamponade over 6 months were 10.569(1.519-73.555), 15.325(1.470-159.731), 17.828(2.268-140.171), 25.783(2.579-257.759), 4.327(1.436-13.035), respectively. They were independent risk factors of high IOP after surgery. Conclusion The risk factors of high IOP after vitrectomy combined with silicon oil tamponade from high to low are uveitis, emulsification of silicone oil, combining with lentectomy, high myopia and time of silicon oil tamponade for too long. Key words: Vitrectomy; Silicon oil tamponade; High intraocular pressure, after surgery; Factors, causative

Efficacy observation on staging surgery for complicated ocular trauma patients

Objective To observe the clinical efficacy of first-period, second-period and third-period surgery for 17 cases with complicated ocular trauma. Methods The data of 17 eyes of 17 patients with complicated ocular trauma in our hospital between June 2010 and May 2015 were collected and retrospectively analyzed. All patients underwent eyeball rupture debridement surgery on first-period surgery in our hospital and retrospectively analyzed. All or most iris and lens prolapsed out of the eyeball or were missing. Seventeen patients with different degree cyclodialysis received vitrectomy combined with silicone oil tamponaded and cyclodialysis repair on second-period surgery. Silicone oil of 17 patients were removed and combined with IOL sulcus suture fixation on third-period surgery. Results The eyes of 17 patients were preserved. The ciliary body were all reattached. The visual acuity were all improved after surgery. The detached retinas were all reattached. There was no complication related to silicone oil emulsification or uncontrollable secondary glaucoma. Conclusion The combined surgery for the treatment of complicated ocular trauma with aniridia, aphakic and cyclodialysis can recover their cilary body function, preserve eye balls and improve the visual acuity. Key words: Ocular trauma, complicated, aniridia, aphakic, cyclodialysis; Vitrectomy; Silicone oil tamponade; Implantation, lens, intraocular; Sulcus suture fixation

Comparison of IOL refractive power caculation using different apparatus and various formulas in cataract eyes with silicon oil tamponade

Background Silicon oil tamponade eyes following vitrectomy accelerate and induce lens opacification, so the accurate measurement and calculation of intraocular lens (IOL) diopter before cataract extraction+ IOL implantation is very important for the recovery of visual function. Objective This study was to compare the differences of IOL powers measured and calculated by different apparatus and different IOL power formulas before cataract extraction+ IOL implantation silicon oil tamponade combined with cataractous eyes. Methods A prospective, consecutive, nonrandomized study was performed.Thirty-six silicon oil tamponade with cataract eyes of 36 patients were included in the Second Affiliated Hospital of Soochow University from August 2011 to October 2013.Patients with silicone oil emulsification for 4 months to 2 years prepared to treat by cataract extraction+ IOL implantation+ silicon oil removal.Axial length (AL), corneal curvature (CC) and anterior chamber depth (ACD) were measured with IOLMaster and A-scan with manual kerameter (MK) in the eyes for the prediction of IOL power by SRK-Ⅱ, SRK/T, Hoffer Q, Holladay 1 and Haigis formulas under the oral informed consent.The mean predictive error (MPE) and mean absolute refractive error (MAE) between predictive IOL diopters before operation and actual IOL diopters after operation were evaluated. Results The AL and ACD values measured by IOLMaster was (25.43±0.90)mm and (3.22±0.38)mm, which were significantly higher than (25.21±1.02)mm and (3.07±0.62)mm by A-scan+ MK respectively, the difference between the two measure methods was statistical significance(both at P=0.000). No significant difference was found in measured CC values between IOLMaster and A-scan+ MK ([44.58±1.57]D vs.[44.56±1.62]D) (P=0.568). When the parameters measured by IOLMaster were used, the MAE from SRK/T formula was smaller than that from SRK-Ⅱ, Hoffer Q, Holladay 1 and Haigis formulas (P=0.017, 0.009, 0.012, 0.001), and the MAE from Haigis formula was significantly larger than that from SRK-Ⅱ, Hoffer Q and Holladay 1 formulas (P=0.026, 0.035, 0.021). When measured by A-scan+ MK, the MAE from Haigis formula was significantly larger than that from SRK-Ⅱ, SRK/T, Hoffer Q and Holladay 1 formulas (P=0.007, 0.004, 0.018, 0.006). There was no significant difference in the number of eyes with MAE≤1.0 D between IOLMaster and A-scan+ MK measurements under the calculation of SRK-Ⅰ, SRK/T, Hoffer Q and Holladay 1 formulas (χ2=0.107, 2.250, 0.845, 0.084, all at P>0.05). However, the number of eyes with MAE≤1.0 D was significantly increased in IOLMaster measurement compared with A-scan+ MK under the calculation of Haigis formula (χ2=4.431, P=0.035). Conclusions In silicon oil-filled cataract eyes, SRK/T formula appears to have a more accurate predictive value of IOL power than that of other formulas when employ IOLMaster; when use A-scan+ MK measurement, the predictive value of IOL power seems to be better by using SRK-Ⅱ, SRK/T, Holladay 1 or Hoffer Q formulas. Key words: Biometry/instrumentation; Lens implantation, intraocular; Refraction, ocular/physiology; Algorithms; Cataract; Silicone oils/administration; Prospective studies

&amp;lt;i&amp;gt;In Vivo&amp;lt;/i&amp;gt; Emulsification Analysis of 1000 cs and 5000 cs Silicone Oil after Rhegmatogenous Retinal Detachment Vitrectomy Surgery

Purpose: To compare in vivo emulsification of silicone oil 1000 and 5000 centistokes (cs) after retinal detachment surgery. Design: Comparative non-interventional Retrospective study. Methods: Silicone oils from patients who underwent retinal detachment surgery were investigated using Spectrophotometer UV-Vis. Spectroscopically changes determine emulsification with the time of tamponade, inflammation, patients age and severity of retinal detachment. Results: We found significant difference on absorbance (p = 0.004) between used 1000 Centi stoke (cs) silicon oil (average wave length 2.51 nm; SD: 1.575 nm) and used 5000 cs silicon oil (average wave length 0.910 nm; SD: 0.564 nm). Conclusions: In vivo emulsification was higher in silicone oil 1000 compared to 5000 cs silicone oil after vitreoretinal tamponade 8 - 12 weeks due to retinal detachment surgery. Emulsification related to higher absorbance and lower transmittance in 1000 cs silicone oil. Inflammation may become a factor affecting this condition.

Towards better characterization and quantification of emulsification of silicone oil invitro.

Emulsification is related to complications arising from silicone oil (SO) tamponade. Currently, there is no widely accepted method for testing the propensity of SO to emulsify that are physiologically realistic and quantitative. We compared different ways of inducing emulsification namely vortex mixing, sonication and homogenization. Silicone oil (SO) emulsification was quantitatively assessed using the Coulter counter and laser light scattering. The invitro results are compared with the droplet size distribution profile of vitreous clinical washout. Conventional SO was compared with two novel SO blends with high-molecular-weight (HMW) additives (SOHMW2000 and SOHMW5000 ). Of the three methods for inducing emulsification, homogenization generated the most consistent emulsion samples with the smallest variance. The results from the Coulter counter measurement correlated strongly with the laser light scattering measurement within the range of 1 to 30µm. The droplet size distribution profiles from human eyes were similar to that of emulsions generated invitro by homogenization. The human size distribution profile was within the range of values obtained by the invitro experiment. Compared to the conventional SO, the emulsion droplet counts for the new SO blends were significantly lower (SOHMW2000 and SOHMW5000 were 79% (±17%) and 49% (±18%) of the SO2000 and SO5000 , respectively; p=0.03 and p=0.002). Emulsion generated invitro by homogenization has similar droplet size profile as human eyes filled with SO. Using this method to induce emulsion, SO blends with HMW additives demonstrated less propensity to emulsification with lower droplet counts compared to conventional SO with similar shear viscosity.

The experience of treatment of severe ocular trauma with vitrectomy and combined surgery

Objective To summarize the clinical experience of vitrectomy and combined surgery for the treatment of severe ocular trauma. Methods Forty-two eyes of 42 cases with severe ocular trauma underwent pars plana three-channel vitrectomy and combined with extraction of intraocular foreign bodies, cataract extraction, and/or retinal detachment surgery. Results The postoperative visual acuities of 39 eyes (92.86%) were improved, which were at ≤0.04 in 5 eyes(11.90%), 0.05~0.25 in 15 eyes(35.71%), 0.3~0.5 in 20 eyes(47.63%), ≥0.6 in 2 eyes(4.76%). The visual acuities at ≥0.05 were found in 37 eyes(88.10%) postoperatively and 4 eyes (9.52%) preoperatively.By chi-square test: The difference were statistically significant(χ2=51.887, P=0.000). The main postoperative complications are high intraocular pressure in 5 eyes (11.90%), after cataract in 4 eyes (9.52%), retinal detachment in 1 eye (2.38%), silicone oil emulsification in 3 eyes (7.14%). These complications were cured by the corresponding treatment.No serious complications, such as endophthalmitis, happened. Conclusion Vitrectomy combined with other different surgery for severe ocular trauma may obtain good postoperative vision with few complications. Key words: Ocular trauma, severe; Vitrectomy, combined surgery

Expression of IL-17 in aqueous humor of secondary glaucoma after silicone oil tamponade

Objective To study the expression of IL-17 (Interleukin 17) in aqueous humor of secondary glaucoma after silicone oil tamponade. Methods Sixty-two eyes of 60 patients with retinal detachment treated by vitrectomy and silicon oil tamponade and a secondary surgery of silicon oil removal. They were divided into glaucoma group (20 patients, 20 eyes) and control group (40 patients, 42 eyes) according to the intraocular pressure. The aqueous humor specimen were collected from patients in both two groups before the silicon oil removal operation, concentration of IL-17, IL-6 and TNF-α were detected and compared between the two groups. Results There were no statistically significant differences between the two groups in the silicone oil granule in anterior chamber, peripheral anterior synechia of iris or emulsified silicone oil (P>0.05). The concentrations of IL-17, IL-6 and TNF-α were (200.45±25.79) pg/ml, (355.86±45.27) pg/ml and (863.27±51.66) pg/ml in glaucoma group, which were significantly higher than those in control group (150.65±32.57) pg/ml, (238.49±52.16) pg/ml and (622.15±47.13) pg/ml (t=3.75, P=0.04; t=2.86, P=0.04; t=2.15, P=0.03). Conclusion High concentration of IL-17 was found in the aqueous humor in the patients of secondary glaucoma after vitrectomy and silicon oil tamponade, it might be the mechanism for IL-17 implicating in the pathogenesis of silicon oil glaucoma, through IL-6 and TNF-α expression. Key words: Glaucoma, secondary; Vitrectomy; Silicon oil tamponade eye; IL-17

Effect of hydrophobic modification of hydroxypropyl methylcellulose on silicone oil emulsions

ABSTRACTTo study the effect of hydrophobic modification of the emulsifier on the relationship between emulsion stability and polymer emulsifier concentration, silicone oil emulsions were prepared using hydroxypropyl methylcellulose (original HPMC) and HPMC stearoxy ether (hydrophobic HPMC) at concentrations around their overlap concentrations. Both HPMC types completely emulsified the silicone oil. However, the volume fraction of silicone oil in the emulsion prepared using hydrophobic HPMC was less than that that by the original HPMC, and the average oil droplet size in the former emulsion was less than that in the latter emulsion. Increasing HPMC concentration led to increase in both the amount of adsorbed polymer emulsifier and the storage moduli in the linear region, irrespective of which HPMC was used. Stress-strain sweep curves obtained by a rheo-optical method showed that emulsions stabilized by the hydrophobic HPMC flowed slowly, even beyond the yield stress, whereas emulsions prepared using the original HPMC flowed quickly beyond the yield stress. The storage moduli of the emulsions prepared by the hydrophobic HPMC were larger than those prepared using the original HPMC.

Improved Water Barrier Properties of Calcium Alginate Capsules Modified by Silicone Oil

Calcium alginate films generally offer poor diffusion resistance to water. In this study, we present a technique for encapsulating aqueous drops in a modified calcium alginate membrane made from an emulsion of silicone oil and aqueous alginate solution and explore its effect on the loss of water from the capsule cores. The capsule membrane storage modulus increases as the initial concentration of oil in the emulsion is increased. The water barrier properties of the fabricated capsules were determined by observing the mass loss of capsules in a controlled environment. It was found that capsules made with emulsions containing 50 wt% silicone oil were robust while taking at least twice the time to dry completely as compared to capsules made from only an aqueous alginate solution. The size of the oil droplets in the emulsion also has an effect on the water barrier properties of the fabricated capsules. This study demonstrates a facile method of producing aqueous core alginate capsules with a modified membrane that improves the diffusion resistance to water and can have a wide range of applications.

Хирургия вторичной глаукомы у пациентов с оперированной отслойкой сетчатки, вызванной эмульгированным силиконовым маслом

Хирургия вторичной глаукомы у пациентов с оперированной отслойкой сетчатки, вызванной эмульгированным силиконовым маслом

Apoptosis Factors of Lens Epithelial Cells Responsible for Cataractogenesis in Vitrectomized Eyes with Silicone Oil Tamponade

BackgroundThe aim of this study was to determine the expression of apoptotic factors Bax, Bcl-2, and Caspase-3 in lens epithelial cells (LECs) from cataracts secondary to pars plana vitrectomy with silicone oil (SO) tamponade. We also investigated the impact of SO emulsification on the expression of apoptotic factors.Material/MethodsAnterior capsulotomy specimens of 20 eyes in 20 patients with cataract secondary to SO tamponade (Group 2), were collected. Another 20 eyes of 20 patients with age-related cataract (Group 1) were recruited as controls. The anterior capsule specimens were obtained from the patients during cataract surgery, frozen and later analyzed with respect to immunohistochemical stains of Bax, Bcl-2, and Caspase-3 using a confocal microscope.ResultsAge, sex, and laterality did not show any difference between the 2 groups. There was a greater increase in Bax and Caspase-3 expression in LEC in Group 2 than in Group 1 (PBax<0.0001, PCaspase-3<0.0001). The Bcl-2 expression decreased in Group 2, although the difference was not significant (P=0.616). The changes of apoptosis factors are not associated to SO emulsification (PBax=0.354, PBcl-2=0.728, PCaspase-3=0.939).ConclusionsThe caspase-3-dependent apoptosis of LECs increased in complicated cataract patients with SO endotamponade. The Bax played a critical role in regulating apoptosis of LECs in vitrectomized eyes with SO tamponade. The SO emulsification had no significant impact on the expression of apoptosis factors.

Correlation of spectral domain optical coherence tomography findings in sub-silicone oil foveal depression space and visual outcome in eyes undergoing silicone oil removal

Background/PurposeTo describe small hyper-reflective spherical bodies in sub-silicone oil-foveal depression (SSO-FD) space using spectral domain optical coherence tomography (SD-OCT) and its effect on visual outcomes in eyes undergoing silicone oil removal (SOR). MethodsThis was a prospective interventional comparative study comprising 42 eyes undergoing SOR with clear media. All patients underwent detailed clinical examination and SD-OCT scan of fovea preoperatively and at 30 days and 90 days postoperatively. Patients were divided into Group A (n = 21) and Group B (n = 21) depending on presence or absence, respectively, of small hyper-reflective spherical bodies in the SSO-FD space in preoperative scans. The findings between SD-OCT and best-corrected visual acuity were correlated and analyzed. ResultsThe mean age of patients was 41.9 years (range, 23–60 years) in Group A and 45.6 years (range, 23–60 years) in Group B. Twenty-one eyes showed small hyper-reflective spherical bodies on SD-OCT imaging. These were thought to represent emulsified silicone oil globules trapped in the potential space created by silicone oil meniscus and foveal pit, which is the SSO-FD space. These bodies were absent in all post SOR scans of Group A and Group B. Group A had significant visual improvement (p = 0.0001) after SOR with clearance of these hyper-reflective bodies as compared to Group B (p = 0.356). ConclusionWe conclude that these small hyper-reflective spherical bodies in the SSO-FD space were most likely emulsified silicone oil globules and correlated with significant visual improvement with their clearance after silicone oil removal.

Three-Year Efficacy and Safety of a Silicone Oil-Filled Foldable-Capsular-Vitreous-Body in Three Cases of Severe Retinal Detachment.

PurposeWe previously designed a novel foldable capsular vitreous body (FCVB) to treat severe retinal detachment and evaluated its performance in a 1-year follow up study. The purpose of this study was to determine the efficacy and safety of a silicone oil (SO)-filled FCVB in a 3-year follow-up.MethodsStandard three-port pars plana vitrectomy was performed, and the FCVB was triple folded and implanted in the vitreous cavity of three eyes. The SO then was injected into the capsule to support the retina. The eyes were examined using Goldmann applanation tonometry, fundus photography, optical coherence tomography (OCT), noncontact specular microscopy, and ultrasound biomicroscopy over a 3-year implantation period.ResultsAt the 3-year follow-up, retinal reattachment was achieved in all three cases, with steady intraocular pressure. The visual acuity showed slight fluctuations, and it was slightly increased compared to baseline. Optical coherence tomography revealed decreased retinal thickness and an altered retinal structure in the implanted eyes compared to the control eyes. No keratopathy, glaucoma, SO leakage, SO emulsification, or other apparent complications occurred during the observation period.ConclusionThe SO-filled FCVB was effective and safe as a vitreous substitute in three eyes over a 3-year observation period.Translational RelevanceSilicone oil emulsification is a severe complication after retinal detachment surgery. On the basis of animal experiments, we investigated a new strategy and product, the FCVB, to overcome this complication. In this pilot study, FCVB limited SO emulsification and migration. This study could lay the foundation for a further multicenter clinical trial.

Analysis of thin baked-on silicone layers by FTIR and 3D-Laser Scanning Microscopy

Pre-filled syringes (PFS) and auto-injection devices with cartridges are increasingly used for parenteral administration. To assure functionality, silicone oil is applied to the inner surface of the glass barrel. Silicone oil migration into the product can be minimized by applying a thin but sufficient layer of silicone oil emulsion followed by thermal bake-on versus spraying-on silicone oil. Silicone layers thicker than 100nm resulting from regular spray-on siliconization can be characterized using interferometric profilometers. However, the analysis of thin silicone layers generated by bake-on siliconization is more challenging. In this paper, we have evaluated Fourier transform infrared (FTIR) spectroscopy after solvent extraction and a new 3D-Laser Scanning Microscopy (3D-LSM) to overcome this challenge. A multi-step solvent extraction and subsequent FTIR spectroscopy enabled to quantify baked-on silicone levels as low as 21–325μg per 5mL cartridge. 3D-LSM was successfully established to visualize and measure baked-on silicone layers as thin as 10nm. 3D-LSM was additionally used to analyze the silicone oil distribution within cartridges at such low levels. Both methods provided new, highly valuable insights to characterize the siliconization after processing, in order to achieve functionality.

Characterization of Optical and Structure Properties of Polydimethylsiloxanes

Polydimethylsiloxanes (PDMS), (CH3)3SiO-[Si(CH3)2O]n-Si(CH3)3, known as silicone oil is a tamponade liquid which is very important in vitreoretinal surgery, especially in the treatment of complicated retinal detachment. Here, we investigated the optical properties and structure of silicone oil with high viscosity silicone oil of 5500 cSt and low viscosity silicone oil of 1300 cSt in order to understand the changing of physical properties of silicone oil before and after using in vitreoretinal surgery as a tamponade liquid and analyze the relationship between the tamponade duration and changed in silicone oil properties. From UV-Vis spectroscopy and refractometer measurement, it is found some changes in transmittance and refractive index values in both silicone oil after using as a tamponade liquid. From fourier transform infrared (FT-IR) spectroscopy, some additional of functional groups of N-H and O-H bond are observed at 1634.5 cm-1 and 3435.7 – 3764.5 cm-1, respectively. The changes of optical and structure properties of silicone oil after using as a tamponade liquid are assumed to be responsible in emulsification of silicone oil and affect the transmittance quality at visible light spectrum. However, in this study, there is no linear corelation between tamponade duration and changed in silicone oil properties.

A SURGICAL APPROACH TO LARGE SUBRETINAL HEMORRHAGE USING PARS PLANA VITRECTOMY AND 360° RETINOTOMY

To evaluate the surgical approach of pars plana vitrectomy combined with 360° retinotomy and silicon oil tamponade in the treatment of patients with large subretinal hemorrhage. Prospective, nonrandomized, and noncomparative case series study. Consecutive patients with breakthrough vitreous hemorrhage and massive subretinal hemorrahge were recruited to have combined surgery of pars plana vitrectomy with 360° retinotomy and silicone oil temponade. The main outcomes were best-corrected visual acuity, retina status, and postoperative complications. Twenty-one patients (21 eyes) were included. The mean follow-up was 19.9 ± 7.4 months. The mean preoperative thickness of subretinal hemorrhage was 4.25 ± 0.69 mm. All the patients were observed to have choroidal neovascularization during the surgical procedure. The mean logarithm of the minimum angle of resolution best-corrected visual acuity (Snellen equivalent) significantly improved from preoperatively 2.64 (hand movement) to 1.73 (7/400), 1.50 (6/200), 1.51 (6/200), and 1.45 (7/200) at 1 month, 3 months, 6 months after the initial surgery, and final follow-up. Postoperative complications included temporary higher intraocular pressure, silicone oil emulsification, lens opacification, epimacular membrane, retinal pigment epithelium loss, and subretinal fibrosis. At the end of the follow-up, retinas were all reattached without any recurrence of choroidal neovascularization. Pars plana vitrectomy combined with retinotomy and silicone oil tamponade is effective for eyes with breakthrough vitreous hemorrhage and massive subretinal hemorrahge.

The changes in physical properties of silicone oil after intraocular tamponade

Objective To observe the changes in physical properties of silicone oil after intraocular tamponade. Methods The silicone oil was removed from 99 patients (99 eyes) of primary retinal detachment with 23G vitreous cutter system. The upper silicone oil was collected after put the vitrectomy samples at room temperature for 3 days. According to the time of intraocular tamponade, the silicone oil samples were divide into six groups including group A (1 month, 12 samples), group B (2 months, 15 samples), group C (3 months, 25 samples), group D (6 months, 22 samples), group E (1 - 2 years, 13 samples) and group F (above 2 years, 12 sample). Fresh unused silicone oil was set as blank control group. Then the emulsion particles, kinematic viscosity, surface tension, density, transmittance and refractive index were measured. Results The difference between group A - F and the control was statistical significant (P 0.05). The number of silicone oil emulsion particles has no statistical difference between group A and the control (P>0.05), but was significantly different between group B - F (P 0.05), but was significantly different between group C - F (P 0.05), but is significantly different between group E and F (P 0.05), but was significantly different between group E and F (P 0.05). Conclusions The physical properties of silicone oil will change during the intraocular tamponade. The emulsion particles number will increase and the transmittance will decrease after 2 months, the kinematic viscosity of silicone oil will decrease significantly after 3 months, and the density and surface tension will change significantly after 1 year of tamponade. Key words: Silicone oils/therapeutic use; Silicone oils/ adverse effects

In Vitro Modeling of Emulsification of Silicone Oil as Intraocular Tamponade Using Microengineered Eye-on-a-Chip.

There is a lack of a standardized methodology or a physiologically realistic in vitro model to investigate silicone oil (SO) emulsification. In this study, we replicated the SO-aqueous interface within a microfluidic chip to study the formation of SO emulsion droplets in the eye cavity. A chip made of poly(methylmethacrylate) was used to represent a cross-section of the posterior eye chamber. A retinal ganglion cell line was coated on the inner surface of the chamber to mimic the surface property of the retina. Silicone oil of different viscosities were tested. The SO-aqueous interface was created inside the chip, which, in turn, was affixed to a stepper-motor-driven platform and subjected to simulated saccadic eye movement for four days. Optical microscopy was used to quantify the count and size of SO emulsified droplets. Among SO of different viscosities, SO 5 centistokes (cSt) emulsifies readily, and a high number of droplets formed inside the chip. Silicone oil 100 cSt led to fewer droplets than 5 cSt, but the droplet count was still significantly higher than other SO of higher viscosities. There were no significant differences in the number of droplets among SO with viscosities of 500, 1000, and 5000 cSt. In all SOs tested, the number of droplets increased, whereas their size decreased with longer duration of simulated saccades. The study platform allows quantification of the number and size of emulsified SO droplets in situ. More importantly, this platform demonstrates the potential of microtechnology for constructing a more physiologically realistic in vitro eye model. Eye-on-a-chip technology presents exciting opportunities to study emulsification and potentially other phenomena in the human eye.