Yu-Chi Liu

Intraocular lens as a drug delivery reservoir

Purpose of review To describe the development and use of intraocular lenses (IOLs) as drug delivery systems and to review the current literature on their application and efficacy. Recent findings Many drugs have been loaded onto IOLs by coating or by attachment in a separate reservoir. With incorporation of polymeric materials either as a coating or by attachment as a separate reservoir, it is possible to achieve a sustained and controlled release of drugs. Experimental evidence in animal models has shown that IOL drug delivery systems are effective in the prevention and treatment of inflammation, infection and posterior capsule opacification after cataract surgery. Summary The use of IOLs as drug delivery reservoirs appears to show great promise. Although excellent results with therapeutic potential have been reported in experimental animal studies, further studies are needed to reach clinical use.

Comparative study of nJ- and μJ-energy level femtosecond lasers: evaluation of flap adhesion strength, stromal bed quality, and tissue responses.

PURPOSE To compare flap adhesion strength, stromal bed quality, and tissue responses after flap preparation using nJ- and μJ-energy level femtosecond lasers. METHODS All corneal flaps were created by either VisuMax laser (μJ-energy level) or femto-LDV (nJ-energy level). Flap adhesion strength in the rabbits was measured with a tension meter 1 and 2 months postoperatively. To investigate tissue responses to laser delivery, immunofluorescence staining and TUNEL assay were performed 4 and 24 hours postoperatively. To assess flap bed smoothness, human donor corneas were used. Surface irregularities were graded based on scanning electron microscopy results. RESULTS The flap adhesion strength in the VisuMax group at month 1 and 2 was 16.95 ± 1.45 kPa and 18.33 ± 1.81 kPa, respectively; and 12.31 ± 4.15 kPa and 13.85 ± 4.78 kPa in the LDV group, respectively. No significant difference was found between the groups. Fibronectin and apoptotic cells were largely absent at the central incision site in the LDV group, but were present in the VisuMax group. The smoothness of flap beds appeared similar for both groups. An observer scored the VisuMax group 8.00 ± 1.00 and the LDV group 7.33 ± 0.58 (P = 0.387). CONCLUSIONS The flap adhesion strength increased over time after treatment with both lasers. The nJ-energy pulses produced minimal wound healing reaction and apoptotic cells along the incision plane. The application of an nJ-energy laser, which can incise the cornea without inducing significant damage to cells and wound healing reaction, offers great potential at reducing scarring following incisional laser stromal surgery.

New Instruments for Lenticule Extraction in Small Incision Lenticule Extraction (SMILE)

Small incision lenticule extraction (SMILE) is an alternative to Laser-Assisted in situ Keratomileusis (LASIK) for correction of myopia. In cases where surgeons inadvertently dissect the posterior surface first, identification of the anterior surface and subsequent removal become difficult since the anterior surface of the lenticule is compacted against the anterior stromal surface. This may result in incomplete lenticule removal, and a remnant of intrastromal lenticule in SMILE may lead to visual sequelae. In order to aid surgeons in lenticule removal, we have designed and developed 5 novel SMILE lenticule strippers to locate and extract the lenticules more easily. The aim of this study was to investigate and compare the efficacy and quality of these lenticule strippers in assisting SMILE. Thirty porcine eyes were used. The ease of extraction and removal of the lenticule with different strippers was graded by an experienced SMILE surgeon, the extracted lenticule circularity was evaluated by calculating the lenticule circularity, and the intactness of the extracted lenticule edge was assessed using scanning electron microscopy. We found these novel strippers can be of great help to improve the safety and quality of SMILE surgery, particularly in those cases of difficult lenticule extraction.

Decellularization of human stromal refractive lenticules for corneal tissue engineering

Small incision lenticule extraction (SMILE) becomes a procedure to correct myopia. The extracted lenticule can be used for other clinical scenarios. To prepare for allogeneic implantation, lenticule decellularization with preserved optical property, stromal architecture and chemistry would be necessary. We evaluated different methods to decellularize thin human corneal stromal lenticules created by femtosecond laser. Treatment with 0.1% sodium dodecylsulfate (SDS) followed by extensive washes was the most efficient protocol to remove cellular and nuclear materials. Empty cell space was found inside the stroma, which displayed aligned collagen fibril architecture similar to native stroma. The SDS-based method was superior to other treatments with hyperosmotic 1.5 M sodium chloride, 0.1% Triton X-100 and nucleases (from 2 to 10 U/ml DNase and RNase) in preserving extracellular matrix content (collagens, glycoproteins and glycosaminoglycans). The stromal transparency and light transmittance was indifferent to untreated lenticules. In vitro recellularization showed that the SDS-treated lenticules supported corneal stromal fibroblast growth. In vivo re-implantation into a rabbit stromal pocket further revealed the safety and biocompatibility of SDS-decellularized lenticules without short- and long-term rejection risk. Our results concluded that femtosecond laser-derived human stromal lenticules decellularized by 0.1% SDS could generate a transplantable bioscaffold with native-like stromal architecture and chemistry.

ITF2357 transactivates Id3 and regulate TGFβ/BMP7 signaling pathways to attenuate corneal fibrosis.

Corneal fibrosis is often seen in patients with ocular trauma and infection that compromises corneal transparency resulting in vision loss. Treatment strategies including NSAIDs, steroids, MMC and corneal transplants have shown tremendous success but with several side effects and cellular toxicity. Histone deacetylase inhibitors (HDACi) have been shown to inhibit corneal fibrosis via TGFβ signaling pathway. In this study, we investigated safety, efficacy and mechanism of action of a HDACi, ITF2357 in TGFβ-stimulated in vitro primary human cornea stromal fibroblasts (pHCSFs) and in vivo in a photorefractive keratectomy-treated rabbit model of corneal fibrosis. We found that in vivo ITF2357 decreased collagen I, collagen IV, fibronectin, integrin αVβ3 expression with a reduction in corneal haze. In addition, ITF2357 reduced myofibroblast formation, suppressed phosphorylation of Smad proteins in TGFβ pathway and inhibited key responsive protein, P4HA1 involved in pro-collagen synthesis. Treatment of pHCSFs with ITF2357 activated BMP7 levels and expressed all the members of inhibitor of differentiation proteins (Id1-Id4), however, it failed to rescue TGFβ-driven transdifferentiation of fibroblasts to myofibroblasts in the presence of siRNA specific to Id3. We conclude that ITF2357 is a potential anti-fibrotic drug that exerts its action via activation of Id3, a downstream target of TGFβ/BMP7 signaling pathways.

Applications of Anterior Segment Optical Coherence Tomography in Cornea and Ocular Surface Diseases

Optical coherence tomography (OCT) is a noncontact technology that produces high-resolution cross-sectional images of ocular tissues. Anterior segment OCT (AS-OCT) enables the precise visualization of anterior segment structure; thus, it can be used in various corneal and ocular surface disorders. In this review, the authors will discuss the application of AS-OCT for diagnosis and management of various corneal and ocular surface disorders. Use of AS-OCT for anterior segment surgery and postoperative management will also be discussed. In addition, application of the device for research using human data and animal models will be introduced.

Use of anterior segment optical coherence tomography to predict corneal graft rejection in small animal models.

PURPOSE To correlate the degree of anterior chamber (AC) inflammation and corneal thickness evaluated by anterior segment optical coherence tomography (ASOCT) with corneal graft rejection status and to explore the value of ASOCT in assisting the diagnosis or prediction of graft rejection using a rat penetrating keratoplasty (PK) model. METHODS A total of 40 PKs were performed using Fisher rats (allogeneic groups) and Lewis rats (syngeneic group) as donors and Lewis rats as recipients: isograft control group (n=10), allograft untreated group (n=10), and allograft with 1% prednisolone acetate treatment group (n=20). All the grafts were evaluated for 28 days by a scoring rejection index (RI) to assess the graft opacity, edema, and neovascularization using slit lamp biomicroscopy. The AC inflammation and corneal graft thickness were assessed using ASOCT. RESULTS All the allogeneic control grafts and four of the 20 allogeneic steroid-treated grafts developed rejection episodes. In the allogeneic treated group, the rejected grafts had a significantly higher mean AC inflammation grade at 1 week (grade 3.25±0.49 vs. 1.83±0.36, P<0.001), significantly thicker central graft thickness at 2 weeks (455.25±42.42 μm vs. 381.247±12.51 μm, P=0.047), and a significantly higher RI at 4 weeks (7.75±0.63 vs. 4.60±0.13, P<0.001) compared to the nonrejected grafts. Eyes with ≥grade 3 AC inflammation at 1 week, or with ≥400 μm central graft thickness at 2 weeks, were significantly associated with graft rejection (odds ratio [OR], 15.15, P=0.009, and OR, 9.75, P=0.014, respectively). CONCLUSIONS The use of ASOCT to evaluate AC inflammation and corneal thickness aids in the early evaluation and diagnosis of graft rejection in animal models. Early increased AC inflammation was an early predictor of graft failure prior to definitive clinical evaluation.

Optimization of subconjunctival biodegradable microfilms for sustained drug delivery to the anterior segment in a small animal model.

PURPOSE We evaluated a biodegradable, sustained-release, prednisolone acetate (PA)-loaded poly[d,l-lactide-co-ε-caprolactone] (PLC) drug delivery system on its biocompatibility, feasibility and release characteristics in vitro and in vivo. METHODS Blank and 40% PA-loaded PLC microfilms with a diameter of 2 mm were fabricated, and the degradation and drug release profiles of the microfilms were characterized in vitro and in vivo. The microfilms were implanted into the subconjunctival space of Lewis rats (n = 48). All eyes were assessed clinically using slit-lamp biomicroscopy, and graded with Hackett-McDonald ocular scoring system and anterior segment optical coherence tomography. Histologic and immunohistochemical analyses were performed comparing blank and PA-loaded microfilm groups. PA concentrations in the aqueous humor were determined by HPLC. RESULTS Subconjunctivally-implanted PLC microfilms were able to deliver PA in a sustained manner over 3 months, with a steady rate of 0.002 mg/d in vivo. Eyes with either blank or PA-loaded implanted microfilms showed a very minimal inflammatory response at the insertion sites and mild degree of collagen encapsulation around the microfilms, with significantly less CD11c cells at 2 and 4 weeks (P = 0.001 and P = 0.002), and collagen formation at 2 weeks (P = 0.001) in the PA-loaded microfilm group. Anterior chamber PA levels were achieved, with concentrations at 76.7 ± 5.9, 70.3 ± 2.3, and 42.7 ± 4.1 ng/mL at 2, 4, and 12 weeks, respectively. CONCLUSIONS PA-loaded PLC microfilms display good biocompatibility, feasibility, and desirable sustained drug release profiles, and have the potential to exhibit antifibrotic and anti-inflammatory effects. This device is applicable to use in small animal models of anterior segment inflammation.

Wound healing profiles of hyperopic-small incision lenticule extraction (SMILE)

Refractive surgical treatment of hyperopia still remains a challenge for refractive surgeons. A new nomogram of small incision lenticule extraction (SMILE) procedure has recently been developed for the treatment of hyperopia. In the present study, we aimed to evaluate the wound healing and inflammatory responses of this new nomogram (hyperopic-SMILE), and compared them to those of hyperopic-laser-assisted in situ keratomileusis (LASIK), using a rabbit model. A total of 26 rabbits were used, and slit lamp biomicroscopy, autorefractor/keratometer, intraocular pressure measurement, anterior segment optical coherence tomography, corneal topography, and in vivo confocal microscopy examinations were performed during the study period of 4 weeks. The corneas were then harvested and subject to immunofluorescence of markers for inflammation (CD11b), wound healing (fibronectin) and keratocyte response (HSP47). The lenticule ultrastructual changes were also analyzed by transmission electron microscopy. Out results showed that hyperopic-SMILE effectively steepened the cornea. Compared to hyperopic-LASIK, hyperopic-SMILE had less postoperative wound healing response and stromal interface reaction, especially in higher refractive correction. However, compared to myopic-SMILE, hyperopic-SMILE resulted in more central deranged collagen fibrils. These results provide more perspective into this new treatment option for hyperopia, and evidence for future laser nomogram modification.

Endothelial Approach Ultrathin Corneal Grafts Prepared by Femtosecond Laser for Descemet Stripping Endothelial KeratoplastyCorneal Graft by Femtosecond Laser Inverse Cutting

PURPOSE To investigate the quality of the ultrathin corneal grafts prepared by femtosecond laser from the endothelial side for Descemet stripping endothelial keratoplasty. METHODS Thirty human corneoscleral buttons were cut from the endothelial side by laser Doppler velocimetry (LDV) with or without viscoelastic materials coating. Two cutting depths were selected: 70 and 90 μm. The postcut endothelial count was determined by specular microscopy, and the graft thickness was evaluated by anterior segment optical coherence tomography. The endothelial viability was determined using Trypan blue/Alizarin red staining, calcein-AM/EthD-1 live/dead cell assay, and scanning electron microscope (SEM). The graft interface smoothness was evaluated by SEM. Another 18 corneoscleral buttons were used as controls for the comparisons. RESULTS The overall targeted cutting depth and achieved cutting depth were significantly highly correlated (r = 0.84). The central to peripheral corneal thickness ratio was 0.976 and 0.998 for the 70- and 90-μm grafts. The percentage of the damaged endothelial cells assessed by vital staining and SEM showed the 70-μm grafts had noticeably more endothelial damage compared with the 90-μm grafts. But the damage was significantly reduced, to the control corneas level, after coating the endothelium with Viscoat. The 90-μm grafts had a slightly rougher graft interface than the 70-μm grafts, but all the grafts dissected by a Chansue dissector exhibited a generally smooth interface. CONCLUSIONS The corneal endothelial grafts prepared by LDV femtosecond laser with endothelial approach produced consistently ultrathin grafts in uniform shape with high accuracy and good endothelial and stromal interface quality.