Akira Kubota

Comparison of three techniques of foveal translocation in patients with subfoveal choroidal neovascularization resulting from age-related macular degeneration

PURPOSE To report the results of three methods of foveal translocation in the presence of subfoveal choroidal neovascular membrane resulting from age-related macular degeneration. METHODS We treated 51 eyes of 51 consecutive patients with subfoveal choroidal neovascular membranes resulting from age-related macular degeneration with one of three techniques of foveal translocation surgery: foveal translocation with partial retinotomy (n = 6), limited translocation (n = 9), and translocation with 360-degree retinotomy (n = 36). All patients were followed for at least 6 months postoperatively. The size of the choroidal neovascular membrane and the amount of foveal displacement, the best-corrected visual acuity, and complications were recorded preoperatively and postoperatively. RESULTS The mean distance of the foveal translocation was greater in the 360-degree retinotomy group (3340 microm) than in the partial retinotomy (1060 microm, P <.001) and the limited translocation groups (1120 microm, P <.001). A final visual acuity of 20/200 or better was achieved in two eyes (33%) in the partial retinotomy group, seven eyes (78%) in the limited translocation group, and 23 eyes (64%) in the 360-degree retinotomy group. The final visual acuity improved by 0.2 logarithm of minimal angle of resolution (logMAR) unit or more in one eye (17%), one eye (11%), and seven eyes (19%), respectively. The final visual acuity was maintained within 1 line in zero eyes, five eyes (56%), and 19 eyes (53%), respectively. A retinal detachment developed postoperatively in five eyes (83%), zero eyes (0%), and 15 eyes (42%), respectively. CONCLUSIONS A significant number of patients improved or maintained best-corrected visual acuity after translocation with 360-degree retinotomy, and limited translocation, whereas translocation with 360-degree retinotomy is suitable for larger choroidal neovascular membranes because it resulted in the greatest foveal displacement among the three translocation procedures.

A method for enhancing the ocular penetration of eye drops using nanoparticles of hydrolyzable dye.

This report describes a method for enhancing the ocular penetration of eye drops using nanoparticles of hydrolyzable dye, which is similar to a prodrug approach. The entry of eye drops into the ocular globe is restricted predominantly by corneal barrier functions. The barrier functions are epithelial tight junctions as well as a physicochemical property consisting of the opposite characteristics of a lipophilic epithelium and a hydrophilic stroma. We found that using a formulation of nanoparticles of hydrolyzable dye (with particles of 200 nm in diameter on average) attained a greater than tenfold higher (about 50-fold) ocular penetration than that of micron-sized particles. The nanoparticles were prepared by a carrier-free technique; i.e., the reprecipitation method. Confocal laser fluorescence microscopy showed that dyes originating from the nanoparticles surmounted the corneal epithelium barrier, which has tight junctions, and achieved deeper penetration into the cornea. The high penetration rate of the dyes into the cornea was attributed to the size of particles (i.e., nanoparticles) and a transformation of dye polarity from lipophilic to hydrophilic in in vivo hydrolysis reactions. We concluded that utilizing in vivo hydrolysis reactions to alter the physicochemical nature of nanoparticles consisting of hydrolyzable compounds was an effective approach for enhancing the ocular penetration of eye drops.

Susceptibility comparisons of normal preoperative conjunctival bacteria to fluoroquinolones.

PURPOSE: To compare the susceptibility and efficacy of 3 fluoroquinolones, (levofloxacin, gatifloxacin, and moxifloxacin) in treating conjunctival bacteria in patients having ocular surgery. SETTING: Osaka University Hospital, Osaka, and Tohoku University Hospital, Miyagi, Japan. METHODS: Eyes of patients were examined preoperatively. Aerobic and anaerobic cultures were obtained from conjunctival swabs. The minimum inhibitory concentrations (MICs) of levofloxacin, gatifloxacin, and moxifloxacin for isolated strains were determined. Using the MIC values, descriptive statistics (median, MIC50, MIC90, mode, and range), susceptibility, and efficacy of each fluoroquinolone were calculated for the bacteria isolated, and the data were analyzed statistically. RESULTS: Of the 200 eyes sampled, 163 (81.5%) had positive bacterial growth. From the 163 eyes, 235 bacterial strains were isolated: 116 (49.4%) Propionibacterium acnes; 58 (24.7%) coagulase‐negative Staphylococcus (CNS), including 36 methicillin‐sensitive CNS (MS‐CNS) and 22 methicillin‐resistant CNS (MR‐CNS); 10 (4.3%) Staphylococcus aureus, including 6 methicillin‐sensitive S aureus and 4 methicillin‐resistant S aureus (MRSA); and 29 (12.3%) Corynebacterium. Approximately 40% of Staphylococci (22/58 CNS, 37.9%; 4/10 S aureus, 40.0%) were methicillin‐resistant. Furthermore, 18 (81.8%) of MR‐CNS and all 4 MRSA were fluoroquinolone resistant. The MICs of moxifloxacin and gatifloxacin were statistically significantly lower than those of levofloxacin for CNS and P acnes (P<.05, Kruskal‐Wallis test). However, there was no statistically significant difference in the susceptibility patterns of the fluoroquinolones for these strains (P>.05, McNemar test). CONCLUSION: Because many methicillin‐resistant and fluoroquinolone‐resistant strains were isolated from the conjunctiva preoperatively, clinicians should be mindful of endophthalmitis or ocular infections associated with these strains.

Transparent, tough collagen laminates prepared by oriented flow casting, multi-cyclic vitrification and chemical cross-linking.

The lamellar architecture found in many natural fibrous tissues has a significant bearing on their specific functions. However, current engineered tissues have simultaneously no realistic structures and no adequate functions. This study demonstrates a two-step process for obtaining structurally mimicking laminates in natural fibrous tissues with good optical and mechanical characters from purified-clinically-safe collagen molecules. Stacked lamella structures can be created by repeating flow casting, with the controlling parallel/orthogonal directionalities of each thin single-layer (2-5 μm in thickness). The transparency of laminates is successfully improved by a unique multi-cyclic vitrification with chemical cross-linking. The directionalities of optical and mechanical functions in laminates are strongly related with the preferential collagen alignments in the laminates. The tensile strength of laminates is extremely higher than any other engineered materials as well as native cornea, which exhibit an orthogonal laminated collagen structure and a good optical transmission.

Flow-manipulated, crosslinked collagen gels for use as corneal equivalents.

Our aim was to construct a mechanically stable and optically transparent collagen gel from an acidified atelocollagen solution which is suitable for use as a corneal stromal equivalent. Light transmission and mechanical testing were conducted on variously crosslinked constructs at different pH levels. Ultrastructural analysis was performed to assess directionality of the molecular arrangement produced by flow manipulation, as well as the amount of collagen fibrillogenesis which resulted from different pH and/or crosslinking conditions. Clinical and histological integration of the gels with living tissue was examined following implantation into rabbit corneal intra-stromal pockets. Transmission electron microscopy revealed the importance of the fine control of pH levels during gel formation and indicated that the stage at which collagen fibrillogenesis is halted within the constructs was critically dependent on the pH of the collagen solution. Transparency testing disclosed that high levels of collagen fibrillogenesis, as well as high levels of crosslinker concentration, detrimentally affected the transparency of the construct. As a result, a dual titration was required to achieve good light transmission through the gels. It was also evident that the amount of crosslinking required to gelate the collagen solution was reduced as the level of fibrillogenesis progressed. Thus, it was necessary to establish a balance between the solution pH and crosslinker concentration. Implantation of the collagen constructs into partial depth intra-stromal pockets in rabbits was followed up for 6 months, and demonstrated favourable biocompatibility. This showed that gels which had lower levels of both fibrillogenesis and crosslinking were degraded more readily by the host tissue. The collagen gels described here are mass-production friendly, and have promise as potential functional stromal equivalents for use in stromal grafting, or in constructing full thickness artificial corneas.

Anisotropic Mechanical Properties of Collagen Hydrogels Induced by Uniaxial-Flow for Ocular Applications

Engineering of well-organized tissue constructs is active in the field of material science for biomedical applications. Here, we propose a method for orienting collagen in transparent high-density collagen hydrogels using a simple rolling method. Structural organization and mechanical function were adjusted by regulating the thickness of the construct and the cross-linking reagent. Directionality of collagen alignment on the microscopic scale was achieved parallel to the extensional flow. The preferential alignment of collagen significantly affected the mechanical properties of the construct, with strong tensile strength in the direction parallel to the collagen, and high elastic strain in the perpendicular direction. The tensile strength in the parallel direction was effectively increased by 67% by increasing the cross-linking reagents by 33%, without affecting transparency which remained at 70–80% to visible light. The constructs exhibit good biocompatibility for as a substrate for the expansion of corneal epithelial cells isolated from human donor cornea, indicating the potential for tissue engineering and biomedical applications, particularly for ocular treatments.

Amsler grid examination and optical coherence tomography of a macular hole caused by accidental Nd:YAG laser injury

PURPOSE To compare a macular hole from accidental Nd:YAG laser injury with idiopathic macular holes. METHODS Case report. In a 24-year-old man with accidental Nd:YAG laser injury, right eye, Amsler grid testing and optical coherence tomography were performed. RESULTS Nd:YAG laser injury was responsible for a macular hole about 700 microm in diameter. The visual acuity was 20/100. Amsler grid testing displayed a central scotoma with no surrounding distortion. Optical coherence tomography showed a defect in all retinal layers at the macula. CONCLUSION The scotoma caused by Nd:YAG laser injury is not surrounded by distortion; the hole is produced by the defect of all retinal layers. In contrast, idiopathic macular holes generally produce a pincushion pattern on Amsler grid testing and have no tissue loss.

Irreversible optical clearing of sclera by dehydration and cross-linking

This study manipulates both clear cornea and opaque sclera by two dehydration processes for revealing the relationship between altered tissue structures and change in optical functions. In contrast to the high levels of light scattering in dehydrated tissues by critical point dry, a simple dehydration at 4-8 °C effectively and significantly improved their visible-light transmission, even in the sclera, with accompanying dense fiber packing. Further improvement in visible-light transmission, from 40-50% to 80-90%, has been achieved by flatting tissue surface with cover glasses during dehydration at low temperature. Such optical clearing of sclera by dehydration is reversible. However, chemical cross-linking effectively stabilizes their densely packed microscopic structures and visible-light transmission at over 50% irreversibly, even at wet conditions. Interestingly, the repetition of both low temperature dehydration/cross-linking treatments effectively reduced the required amounts of cross-linking reagents to keep a high transparency. Wet transparent cross-linked sclera can also show a characteristic strong tensile strength. Furthermore, rabbit corneal epithelium has regenerated on the transparent sclera with cross-linking in vitro.

Human Herpesvirus 8 in Corneal Endotheliitis Resulting in Graft Failure After Penetrating Keratoplasty Refractory to Allograft Rejection Therapy

A lthough corneal allograft rejection after penetrating keratoplasty responds to corticosteroids, in some edematous grafts, herpes simplex virus, varicella-zoster virus, or cytomegalovirus causes corneal endotheliitis refractory to steroids and leads to graft failure without appropriate antiviral therapy. However, other cases with idiopathic corneal endotheliitis refractory to steroids remain to be studied. Human herpesvirus 8 (HHV-8) is associated with neoplastic diseases. We report graft failure after penetrating keratoplasty, with aqueous humor positive for HHV-8 DNA by real-time polymerase chain reaction.

Physical and Specific Crosslinking of Collagen Fibers by Supramolecular Nanogelators

Stimuli-sensitive polymers that display in situ physical crosslinking due to physicochemical driving forces such as hydrophobic interactions, hydrogen bonding, stereocomplexation, ligand–receptor interactions, and the self-assembly of peptides have been investigated as smart injectable biomaterials for drug or cell delivery and tissue engineering. [ 1–11 ] Such noncovalent physical approaches provide a much more convenient and biocompatible way to maintain the activity of encapsulated biomolecules and to adhere them to living tissues compared to covalent chemical approaches. [ 9 ] However, most injectable polymers lack the specifi city to target tissue components, especially extracellular matrix (ECM) proteins. The specifi c interaction of injected polymers with target tissue components promotes the effi cient local delivery of encapsulated substances. [ 12 ] Moreover, the in situ non-covalent crosslinking of ECM proteins (especially collagen fi bers) that provides a structural framework during tissue development and repair should be useful for tissue engineering including the treatment of degenerative stromal diseases such as keratoconus. We employed a collagen mimetic peptide (CMP), (POG) 10 (P = proline, O = hydroxyproline, G = glycine), to fabricate a high-performance injectable biomaterial possessing specifi city for collagen fi bers. It is known that (POG) 10 , a synthetic peptide composed of a collagen-like repetitive amino acid sequence, has played a central role in elucidating the triple-helical structure and thermal stability of natural collagens. [ 13–17 ] Recently, various CMPs have been studied as drug-delivery carriers, thermosensitive gelators, and collagen modifi cation tools due to their unique thermoresponsive triple-helix formation and collagen binding properties via hydrogen bonding. [ 18–20 ] Herein, we synthesize a multiarmed poly(ethylene glycol) (PEG) terminally modifi ed