Yaqin Liu

Refractive shifts in four selected artificial vitreous substitutes based on Gullstrand-Emsley and Liou-Brennan schematic eyes.

PURPOSE To determine and compare the refractive shifts based on Gullstrand-Emsley and Liou-Brennan schematic eyes after filling them with four selected artificial vitreous substitutes: silicone oil, heavy silicone oil, hydrogels, and encapsuled balanced salt solution. METHODS The optical constants of artificial vitreous body-filled eyes were calculated based on Gullstrand-Emsley and Liou-Brennan schematic eyes with accommodation relaxed. The theoretical refractive shifts in these two models were compared in pars plana vitrectomy (PPV), PPV plus lensectomized and PPV plus intraocular lens (IOL) eyes after four artificial vitreous tamponades. RESULTS The Gullstrand-Emsley schematic eye shows refractive shifts of +8.710, -4.544, +1.136, and -0.338 D in PPV eyes; +11.044, +20.332, +16.351, and +17.413 D in PPV plus lensectomized eyes; and the need for IOL powers of +22.195, +22.366, +22.292, and +22.312 D in PPV plus IOL eyes in silicone oil, heavy silicone oil, hydrogels, and encapsuled balanced salt solution tamponade eyes, respectively. Similarly, the Liou-Brennan schematic eye induced shifts of +6.260, -3.266, +0.817, and -0.272 D in PPV eyes; +13.181, +20.654, +17.451, and +18.305 D in PPV plus lensectomized eyes; and the need IOL powers of +13.522, +23.767, +19.389, and +20.558 D in PPV plus IOL eyes, respectively. CONCLUSIONS The Gullstrand-Emsley schematic eye is a convenient and accurate model for predicting refractive shifts for hydrogels and encapsuled balanced salt solution substitutes in PPV eyes. The Liou-Brennan schematic eye is recommended for silicone oil and heavy silicone oil in PPV eyes and for all four substitutes in PPV plus lensectomized eyes and PPV plus IOL eyes. In addition, the encapsuled balanced salt solution changes the refraction little in either schematic eye.

Evaluation of the levofloxacin release characters from a rabbit foldable capsular vitreous body

The authors have manufactured a novel rabbit foldable capsular vitreous body (FCVB). The aim of this study was to determine whether this rabbit FCVB can release levofloxacin in vitro and in vivo, and to evaluate the release characteristics. In vitro, the rabbit FCVB with levofloxacin 500 μg/mL was immersed in cups of modified Franz diffusion cells. Following this, 200 μL of liquid was aspirated at intervals from 10 minutes to 24 hours. In vivo, the FCVB with levofloxacin was implanted into the right eyes of five rabbits. After implantation, the aqueous humor was aspirated on days 1, 7, 14, 28, and 56. The levofloxacin concentrations in the cups and aqueous humor samples were detected by high-performance liquid chromatography–tandem mass spectrometry. The FCVB was observed under a scanning electron microscope. The results showed that the released levofloxacin was stabilized at 20 ng/mL at time points from 10 minutes to 24 hours in vitro. In vivo, levofloxacin concentrations in the aqueous humor were 132, 50, 39, 11, and 15 ng/mL on days 1, 7, 14, 28, and 56, respectively. In the FCVB capsules, 300 nm apertures were observed. These results suggest the rabbit FCVB released levofloxacin stably in vitro and sustainably in vivo. This study provides a novel combined approach, with the FCVB as a vitreous substitute and drug delivery system for the treatment of bacterial endophthalmitis.

Evaluation of the Flexibility, Efficacy, and Safety of a Foldable Capsular Vitreous Body in the Treatment of Severe Retinal Detachment

PURPOSE To determine the flexibility, efficacy, and safety of a novel foldable capsular vitreous body (FCVB) in the treatment of severe retinal detachment in human eyes. METHODS The study involved 11 patients with 11 severe retinal detachments. A standard three-port pars plana vitrectomy was performed, and the FCVB was triple-folded and implanted into the vitreous cavity. Balanced salt solution was then injected into the capsule of the FCVB to support the retina. The treated eyes were examined by ophthalmoscopy, fundus photography, and tonometry during a 3-month implantation period. B-scan ultrasonography, optical coherence tomography (OCT), ultrasound biomicroscopy (UBM), and electroretinogram (ERG) were also performed. The FCVB was removed and examined in the laboratory at the end of the 3-month treatment time. RESULTS The FCVB was easily implanted into the vitreous cavity through a 3-mm incision and was easily removed through a 2-mm scleral incision. Retinal reattachment was found in 8 (73%) of 11 eyes at the end of the 3-month treatment time. The fundus, B-scan, and OCT showed that the FCVB was well distributed in the vitreous cavity and evenly supported the retina. IOP and visual acuity in the FCVB-treated eyes did not show a significant difference when compared with the preoperative measurements. UBM showed that the FCVB smoothly contacted but did not crush the ciliary body. Laboratory examinations showed no significant inflammatory cells in the balanced salt solution, no decrease in spectral transmittance, and no blocking of tiny apertures from the FCVB after a 3-month implantation period. CONCLUSIONS The FCVB was shown to be flexible, effective, and safe as a vitreous substitute over a 3-month implantation time. (ClinicalTrials.gov number, NCT00910702.).

Technical standards of a foldable capsular vitreous body in terms of mechanical, optical, and biocompatible properties.

We previously proposed a new strategy to fabricate a novel foldable capsular vitreous body (FCVB) as a vitreous substitute and found that the FCVB was a very good replacement for closely mimicking the morphology and restoring the physiologic function of the rabbit vitreous body. The aim of this article was to assess the mechanical, optical, and biocompatible properties of a FCVB made from liquid silicone rubber. The mechanical properties show that the shore hardness is 37.80 degrees, the tear strength is 47.14 N/mm, the tensile strength is more than 7.28 MPa, and the elongation ratio is more than 1200%; in addition, the FCVB has 300 nm mili apertures in the capsule. The optical properties reveal that transmittances are 92%, hazes are 5.74%, and spectral transmittance is 97%. The transmittance mission is 2.3% and can sustain a 1500 mW, 0.2 s, 532 nm green laser. The biocompatible properties are shown in the stable extracts experiment, no significant fever, good genetic safety, and no structural abnormality or apoptosis in the cornea, ciliary body, and retina over a 6-month observation period. These results indicate that the FCVB has good mechanical, optical, and biocompatible properties, and the assessment results can be recommended as the FCVB technical standards for industrial manufacturing and inspection.

Sustained Mechanical Release of Dexamethasone Sodium Phosphate from a Foldable Capsular Vitreous Body

PURPOSE Since 300-nm-mili apertures were present in the capsule of the foldable capsular vitreous body (FCVB), the authors tested whether the FCVB could mechanically release dexamethasone sodium phosphate (DexP) from its capsule. METHODS In the in vitro study, DexP at concentrations of 0.25, 0.5, 1, 2, and 4 mg/mL in a balanced salt solution were injected into the capsules, which were immersed in cups of modified Franz diffusion cells. Two hundred microliters of liquid was aspirated at time intervals of 10, 20, 40, 60, 120, 180, 240, 300, and 360 minutes. In the in vivo study, the capsule was folded and implanted into the vitreous cavities of five rabbits. Approximately 0.6 mL DexP (2 mg/mL) was then injected into the capsule. An intravitreal injection with DexP was performed on another five rabbits as the control group. Aqueous humor was aspirated on days 1, 3, 7, 14, 28, and 42 after implantation. The DexP contents in the cups and aqueous humor were detected by HPLC-MS/MS. RESULTS FCVB released DexP in a time-dependent and dose-dependent manner in vitro with five dosages from 10 to 360 minutes. Especially in the 0.25 mg/mL DexP group, the content (y) had good linear relationships with time (x), as shown by y = 0.7635x + 10.205. The DexP contents in the aqueous humor were detected until day 28 and were undetectable on day 42. However, the DexP contents were detected only before day 3 in the controls. CONCLUSIONS FCVB can sustainably and mechanically release DexP by capsule apertures in a time-dependent and dose-dependent manner in addition to serving as a vitreous substitute.

A Novel Vitreous Substitute of Using a Foldable Capsular Vitreous Body Injected with Polyvinylalcohol Hydrogel

Hydrogels may be the ideal vitreous substitutes due to their wonderful physical features and biocompatibility. However, their drawbacks, short residence time, and biodegradation in vivo, have led to the fact that none of them have been approved for clinical use. In this study, we developed a novel approach of using a foldable capsular vitreous body (FCVB) injected with polyvinylalcohol (PVA) hydrogel as a vitreous substitute for long-term tamponade. The 3% PVA hydrogel that was cross-linked by gamma irradiation showed good rheological and physical properties and had no toxicity in vitro. After 180 days retention, the 3% PVA hydrogel inside FCVB remained transparent and showed good viscoelasticity without biodegradation and showed good biocompatibility and retina support. This new approach may develop into a valuable tool to improve the stability performance of PVA hydrogel as a vitreous substitute and to extend the application function of FCVB for long-term implantation in vitreous cavity.

Preliminary efficacy and safety of a silicone oil-filled foldable capsular vitreous body in the treatment of severe retinal detachment.

Purpose: We previously invented a novel foldable capsular vitreous body (FCVB) in the treatment of severe retinal detachment. The purpose of this study was to determine its hydrolytic stability in vitro and further evaluate its efficacy and safety in human eyes. Methods: The hydrolytic stability test proceeded according to State Food and Drug Administration guidelines about intraocular lenses of the ophthalmic implants. A standard three-port pars plana vitrectomy was performed, and FCVB was triple folded and sent into the vitreous cavity of three eyes; then silicone oil was injected into the capsule to support the retina. The treated eyes were examined using Goldmann applanation tonometry, fundus photography, optical coherence tomography, noncontact specular microscopy, and ultrasound biomicroscopy during a 12-month follow-up appointment. Results: The mass of FCVB with silicone oil after 60-day accelerating aging temperature was equal to that at baseline. The FCVB can easily be implanted into the vitreous cavity through a 3-mm incision. The visual acuity and intraocular pressure after FCVB implantation show a slight elevation compared with those of preoperative eyes. The fundus and optical coherence tomography showed that the FCVB was well distributed in the vitreous cavity and evenly supported the retina. Retinal reattachment was found in 3 eyes at the 12-month examination. There was no statistically significant decrease in the density of corneal endothelial cells from baseline to 12 months after FCVB implantation. Ultrasound biomicroscopy showed that the FCVB smoothly contacted but not crushed the ciliary body. Conclusion: Silicone oil–filled FCVB was shown to be effective and safe in 3 eyes as a vitreous substitute over a 12-month observation time.

Clinical Device-Related Article Evaluation of morphology and functions of a foldable capsular vitreous body in the rabbit eye

We previously proposed a new strategy to replace a vitreous body with a novel foldable capsular vitreous body (FCVB). In this study, the FCVB was designed to mimic natural vitreous morphology, and evaluate its physiological functions compared with traditional silicone oil substitutes, in an established rabbit model of proliferative vitreoretinopathy. We found that FCVB was a very good replacement for closely mimicking the morphology and restoring the physiological functions, such as the support, refraction, and cellular barriers, of the rabbit vitreous body. The study has provided us with a novel research and therapy strategy that could effectively mimic the morphology and physiological function of the rabbit vitreous body.

Protein kinase Cα downregulation via siRNA-PKCα released from foldable capsular vitreous body in cultured human retinal pigment epithelium cells

We previously found that downregulation of protein kinase Cα (PKCα) can inhibit retinal pigment epithelium (RPE) cell proliferation involved in the development of proliferative vitreoretinopathy (PVR). In this study, we tested whether PKCα could be downregulated via small interfering RNA (siRNA)-PKCα released from foldable capsular vitreous body (FCVB) in cultured human RPE cells. SiRNA-PKCα content, determined by ultraviolet (UV) spectrophotometer, was released from FCVB containing 200, 300, 400, 500, and 600 nm siRNA-PKCα in a time-dependent manner from 1 to 96 hours and a dose-dependent manner at five concentrations. The content (y) had a good linear relationship with time (x), especially in the 600 nm siRNA-PKCα group (y = 16.214x, R2 = 0.9809). After treatment with siRNA-PKCα released from FCVBs, the PKCα was significantly decreased by RT-PCR, Western blot, and immunofluorescence analysis in RPE cells. These results indicate that PKCα was significantly downregulated by siRNA-PKCα released from FCVB in human RPE cells and provide us with a new avenue to prevent PVR.

A preliminary study to treat severe endophthalmitis via a foldable capsular vitreous body with sustained levofloxacin release in rabbits.

PURPOSE We investigated whether the foldable capsular vitreous body (FCVB) could release levofloxacin sustainably in vitro and inhibit endophthalmitis in rabbit models. METHODS Approximately 1.0 mL levofloxacin (625 μg/mL) was injected into the capsule of nine FCVBS. The levofloxacin release value was determined in the modified franz diffusion cells over time. In the in vivo study, all right eyes of 45 rabbits were infected with Staphylococcus epidermidis AND were divided randomly into three groups at 24 hours after infection: FCVB plus levofloxacin (n = 15), silicone oil plus subconjunctival levofloxacin (n = 15), and an untreated group (n = 15) during a 30-day observation time. Levofloxacin concentrations in the aqueous humor were detected, and therapeutic efficacy was evaluated with clinical evaluation, bacterial counts, cytokine profiles, and histopathology. RESULTS The FCVB released levofloxacin ranging from 9 to 13.5 ng/mL in vitro and from 42 to 1.6 ng/mL in the aqueous humor during 30 days. In the FCVB and silicone-treated groups, clinical inflammation almost was abolished; no bacteria were detected in the aqueous humor; TNF-α, IL-1β, and IFN-γ expression decreased; and relatively normal corneal and retinal architecture were kept after the 30-day treatment. CONCLUSIONS The FCVB could provide us with dual functions, combining a levofloxacin drug delivery system and a vitreous substitute, to treat endophthalmitis in rabbit eyes.