Biomedical subjects

Yasushi Ikuno

Publications and source records attributed to Yasushi Ikuno.

At least 19 recordsLinked to original sources

PubMed2007

Residual indocyanine green fluorescence pattern after vitrectomy for idiopathic macular hole with internal limiting membrane peeling.

BACKGROUND: Internal limiting membrane (ILM) peeling with indocyanine green (ICG) staining is a commonly used procedure to treat idiopathic macular holes (MH). AIM: To report changes in the patterns of residual ICG fluorescence over time after vitrectomy using the Heidelberg Retina Angiograph 2 (HRA2, Heidelberg Engineering, Heidelberg, Germany). METHODS: 10 patients (10 eyes) who had undergone vitrectomy for MH with ILM peeling were included. 9 (90%) patients underwent ILM peeling with ICG, and 1 (10%) patient had it with triamcinolone acetonide (TA). We observed residual ICG using HRA2, postoperatively. Autofluorescence, optical coherence tomography images and best-corrected visual acuity (BCVA) measurements were also obtained. The minimal follow-up was 3 months. RESULTS: The MHs were closed postoperatively in all patients (100%). In eyes that underwent ILM peeling with ICG, the BCVA improved significantly (p<0.001) in 8 (89%) eyes and was unchanged in 1 (11%) eye. HRA2 showed the ICG fluorescence patterns but not TA postoperatively. The ICG hyperfluorescent signal was typically diffuse at the posterior retina and was hypofluorescent around the fovea. The hyperfluorescence then migrated towards the optic nerve disc presumably along the nerve fibre, and the area of ILM peeling was clearly identified. A large number of hyperfluorescent dots were observed instead of diffuse hyperfluorescence that was observed just after surgery. CONCLUSIONS: Patterns of residual ICG fluorescence were sequentially observed with HRA2 after vitrectomy for MH with ICG-assisted ILM peeling.

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PubMed2006

Reoperation for persistent myopic foveoschisis after primary vitrectomy.

PURPOSE: We performed vitrectomy on two eyes for persistent myopic foveoschisis (MF) after primary surgery that did not include internal limiting membrane (ILM) peeling. DESIGN: Interventional case reports. METHODS: Two highly myopic eyes of two patients with persistent MF after primary vitrectomy and gas tamponade but without ILM peeling were treated with pars plana vitrectomy, residual vitreous cortex removal, ILM peeling, and long-term gas tamponade. RESULTS: Total foveal reattachment was achieved and best-corrected visual acuity (BCVA) improved in both eyes. CONCLUSIONS: Reoperation including complete vitreous cortex removal and ILM peeling could be beneficial for patients with persistent MF after primary surgery, indicating that vitreous cortex removal and ILM peeling are critical in treating MF.

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PubMed2006

Vitrectomy for macular holes associated with myopic foveoschisis.

PURPOSE: We reviewed the surgical results of vitrectomy for macular holes (MHs) associated with myopic foveoschisis (MF). DESIGN: Noncomparative, interventional case series. METHODS: setting: Institutional. participants: Eight eyes of eight patients with MHs associated with MF. intervention procedure: All patients underwent vitrectomy, internal limiting membrane peeling, and gas tamponade. main outcome measures: Slit-lamp-based biomicroscopy, optical coherence tomography examinations, and best-corrected visual acuity (BCVA) measurement. RESULTS: The MHs closed in two eyes (25%), and the BCVA improved more than 2 lines in three (37.5%) eyes, remained unchanged in three (37.5%), and worsened in two (25%). The MH size increased significantly in a case with an unresolved MH (P < .05). The postoperative BCVA was significantly correlated with the preoperative BCVA (P < .05). CONCLUSIONS: Although significant visual improvement occurs in less than 50% of cases, vitrectomy can be beneficial for some cases.

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PubMed2006

Tractional internal limiting membrane detachment in highly myopic eyes.

PURPOSE: To report the clinical features of tractional internal limiting membrane (ILM) detachment in highly myopic eyes with posterior staphyloma. DESIGN: Observational case report. METHODS: We reviewed the optical coherence tomography images of 249 eyes in the high myopia clinic. ILM detachment was observed in six eyes (2.4%). We investigated the clinical feature of this finding. RESULTS: Myopic foveoschisis (MF) was present in four of the six eyes (67%) (six patients, two men and four women; mean age, 57.3 years). The mean axial length was 29.3 mm and the mean refractive error was -15.0 diopters. The best-corrected visual acuity levels ranged from 20/400 to 20/13. CONCLUSIONS: Rigidity of the ILM seems to cause tangential traction and results in a major cause of a disease specific to high myopia; that is, MF.

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PubMed2006

[Sub-Tenon's injection of triamcinolone acetonide for choroidal neovascularization].

PURPOSE: To evaluate the efficacy of sub-Tenon's injection of triamcinolone acetonide for age-related macular degeneration (AMD) and polypoidal choroidal vasculopathy (PCV). METHOD: Sub-Tenon's injection of triamcinolone acetonide was performed in patients (27 eyes) with the subfoveal choroidal neovascularization of AMD and in patients (10 eyes) with PCV, and its efficacy was evaluated. The visual acuity and the exudation from lesions evaluated by fluorescein angiography or optical coherence tomography (OCT) at three months or six months after injection were compared to the baseline values. RESULTS: Visual acuity was maintained in 23 of the 27 eyes (85.0%) with AMD and in 8 of the 10 eyes (80.0%) with PCV at three months after injection. Six months after infusion, the rate declined to 76.0% and 66.7%, respectively. Exudation from lesions had decreased in 10 eyes of 25 eyes(40.0%) with AMD and in 2 eyes of 9 eyes (22.2%) with PCV by six months after injection. Complete suppression of the lesions was observed in seven eyes (18.9%) with relatively small lesions. CONCLUSION: Sub-Tenon's injection of triamcinolone acetonide is useful as a treatment modality for AMD and PCV.

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PubMed2006

[Pathogenesis and treatment of myopic foveoschisis].

Myopic foveoschisis (MF) can now be recognized as the result of recent progress in imaging diagnostic technology such as optical coherence tomography (OCT). MF predominantly occurs in highly myopic eyes with posterior staphyloma, and often induces visual loss and/or metamorphopsia. In order to better understand the detailed pathogenesis of MF, we observed 21 myopic eyes after vitrectomy using OCT. Retinal microfolds along the retinal vessels were observed in over 60% of the patients 6 months after surgery. Relative inflexibility of retinal arterioles/venules may be one of the causes for MF. We performed a pilot study (6 eyes of 5 patients) to treat MF by vitrectomy including vitreous cortex removal, internal limiting membrane peeling, and gas tamponade. In all 6 eyes the fovea was reattached and vision improved by more than two lines. This pilot study indicates that vitrectomy is an effective and safe treatment for MF.

Fovea Centralis↗

PubMed2005

Mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3 kinase (PI3K) pathways differently regulate retinal pigment epithelial cell-mediated collagen gel contraction.

Retinal pigment epithelial (RPE) cell-mediated extracellular matrix contraction is believed to contribute to developing proliferative vitreoretinopathy. It has been shown that platelet-derived growth factor (PDGF) and its intracellular signaling pathway, including mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3 kinase (PI3K), are mainly involved in this process. The aim of this study is to investigate how these downstream signaling pathways are related to RPE-mediated collagen gel contraction. We performed the gel contraction assay to evaluate the effect of PDGF in cultured ARPE-19 cells under the presence or absence of PD98059, MAPK inhibitor or wortmannin, PI3K inhibitor. Experiments treated with neutralizing antibody for various subtypes of integrin were also performed and the effect on PDGF-induced gel contraction was investigated. Expression changes of integrin alpha1, alpha2 and beta1 after PDGF stimulation was evaluated using quantitative real-time PCR and flow cytometry. The results showed that PDGF up-regulated ARPE-19 cell-mediated gel contractile activity. PDGF-induced collagen gel contraction was attenuated under presence of PD98059, wortmannin, or neutralizing antibody for integrin alpha1, alpha2, or beta1, all of which are critical subset for binding with type I collagen. The expression of integrin alpha1 and alpha2 was increased after PDGF stimulation in both real-time PCR and flow cytometry, however beta1 expression was not increased. PD98059 significantly attenuated integrin alpha1 and alpha2 expressions. However, wortmannin did not have the same effect. In conclusion, PDGF promotes ARPE-19 cell-mediated gel contraction via both MAPK and PI3K. This was probably due to an increased expression of integrin alpha1 and alpha2, which is mediated by MAPK, but not by PI3K. PI3K may regulate collagen gel contraction by another mechanism other than the up-regulation of integrin expression.

Androstadienes↗

PubMed2005

Electrophysiological and histological studies of chronically implanted intrapapillary microelectrodes in rabbit eyes.

PURPOSE: To determine the safety and efficacy of transsclerally placed intrapapillary wire microelectrodes implanted chronically into the optic nerve head of rabbit eyes. METHODS: Four platinum wire microelectrodes were passed through the sclera and implanted into the optic nerve head of five rabbit eyes for 4-6 months. Color fundus photography, fluorescein angiography, electroretinograms (ERGs), and visually evoked potentials (VEPs) were used to monitor the retina. Electrically evoked potentials (EEPs) were elicited by bipolar electrical stimulation of the optic nerve axons by different combinations of the four electrodes immediately after the implantation and at 1-month intervals thereafter. The effects of the chronic implantation of the electrodes on the morphology of the optic nerve were evaluated by histological and immunohistochemical examinations at 4 and 6 months after the implantation. RESULTS: All of the electrodes remained stable in the implanted sites throughout the post-implantation period, except for one electrode that had pulled out of the optic nerve head at 1 month after implantation. No intraocular infection, inflammation, or vitreoretinal proliferation was observed in any eye. EEPs could be elicited from each pair of electrodes at all testing times. The mean threshold currents (charge densities) to evoke EEPs increased from 19.3 +/- 9.2 microA (6.0 +/- 2.9 microC/cm2) on the implantation day to 78.8 +/- 31.9 microA (24.6 +/- 10.0 microC/cm2) at 1 month after implantation, but did not change significantly thereafter. The implicit time and amplitude of the a- and b-waves of the ERGs and of P1 of the VEPs did not change significantly throughout the post-implantation period. Histological evaluation of the optic nerve head revealed slight tissue encapsulations surrounding the electrode and increased expression of glial fibrillary acidic protein near the surface of the optic nerve. CONCLUSIONS: Implantation of transscleral intrapapillary microelectrodes appears to be safe and effective. These findings indicate that the implantation of microelectrodes in the optic nerve head should be considered for an optic nerve-based prosthesis.

Animals↗

PubMed2005

Ultrastructure of internal limiting membrane in myopic foveoschisis.

PURPOSE: To reveal the pathogenesis of myopic foveoschisis (MF). DESIGN: Clinicopathological report. METHODS: Internal limiting membranes (ILMs) were collected from ten patients with MF and five patients with idiopathic macular hole (IMH) as a control. Samples were subjected to transmission electron microscopic study. Characteristics of the ILM were compared between the two groups. RESULTS: Collagen fiber and cell debris were identified on the inner surface of ILM in seven eyes (70%) with MF, significantly more (P < .05) than found in IMH subjects (0%). More fibrous glial cells were likely to be found on the inner surface of ILM. No significant difference in fibroblast-like cell adhesion was observed. CONCLUSIONS: Collagen fiber and cellular component are suggested to play an important role in developing MF. ILM peeling may be essential for vitrectomy for MF.

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PubMed2005

New micro vertical scissors for the surgical ablation of retinal angiomatous proliferation.

PURPOSE: To develop new micro vertical scissors for the ablation of retinal angiomatous proliferation (RAP) to minimize possible retinal damage. DESIGN: Interventional case report. METHODS: New micro vertical scissors were developed and used for the ablation of RAP vessels. RESULTS: The length of the inner side of the tip is 180 microm, which is approximately one seventh that of regular vertical scissors. The scissors handled easily and the RAP vessels were ablated with less retinal damage compared with that associated with use of standard vertical scissors. Postoperatively, intraretinal hemorrhage was reduced and hyperfluorescence seen on indocyanine green angiography resolved. CONCLUSIONS: The new micro vertical scissors developed for the ablation of RAP vessels can be used safely and effectively during this surgical procedure.

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PubMed2005

Potent retinal arteriolar traction as a possible cause of myopic foveoschisis.

PURPOSE: To report retinal microfold formation after vitrectomy for myopic foveoschisis (MF). DESIGN: Prospective observational study. METHODS: We observed 21 eyes of 17 patients who had undergone vitrectomy for MF with optical coherence tomography (OCT) in this institutional study. We also evaluated the three-dimensional retinal architecture using the OCT-ophthalmoscope in selected cases. Vitrectomy included core vitrectomy, vitreous cortex removal, internal limiting membrane (ILM) peeling with indocyanine green, and gas tamponade. RESULTS: Horizontal linear folds were commonly observed postoperatively. The folds, which were 1,000 to 2,000 microm superior, inferior, or both superior and inferior to the fovea, were detected only by OCT and not by conventional slit-lamp-based biomicroscopy. The microfolds were found in only five eyes (24%) 1 month postoperatively. The incidence increased over time, however, and a microfold was detected in nine eyes (43%) 3 months after surgery and in 13 (62%) 6 months after surgery. OCT-ophthalmoscope examination confirmed the location of the microfold coincided exactly with that of retinal arteriole. The presence of microfolds was not significantly related to the postoperative visual acuity. CONCLUSIONS: Retinal microfolds are common in eyes with MF after vitrectomy with ILM peeling, and they seem to be generated as the result of insufficient flexibility of the sclerotic retinal arteriole during axial length elongation in highly myopic eyes. This finding suggests that the inward tractional force on the retina along the arteriole may be closely related to the pathogenesis of vitreoretinal diseases specific to high myopia, including MF or paravascular microhole formation.

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PubMed2005

Retinal vascular microfolds in highly myopic eyes.

PURPOSE: Retinal microfolds attributable to retinal vessels were first observed after vitrectomy for myopic foveoschisis and were believed to indicate inward retinal traction, possibly leading to high myopia-specific retinal diseases. We report retinal microfolds in high myopia without vitrectomy. DESIGN: Observational case series. METHODS: This is an institutional study. Seven eyes of seven patients in which retinal microfolds were observed using optical coherence tomography (OCT) were included in the study. We used an OCT-ophthalmoscope to confirm the precise location of the microfolds. We also investigated the relationship between the presence of microfolds and subjective distortion detected by examination of the corresponding retinal area using the Amsler grid chart in three eyes. RESULTS: All microfolds detected by OCT coincided with the retinal vessels using the OCT-ophthalmoscope. The folds coincided only with the retinal arterioles in six eyes (86%) and with both arterioles and veins in one (14%). Subjective distortion was detected in the retinal area corresponding to the microfolds in two eyes (67%) but was not detected in one eye (33%). CONCLUSIONS: The incidence of retinal microfolds is 2.9%, and thus they are not uncommon in highly myopic eyes without vitrectomy. The coincident appearance of the folds and vessels suggests that inflexibility of the retinal vessels and retinal stretching attributable to ocular elongation may cause the microfolds. The presence of these microfolds indicates that inward retinal vascular traction could be common in highly myopic eyes.

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PubMed2004

Transretinal electrical stimulation by an intrascleral multichannel electrode array in rabbit eyes.

BACKGROUND: A new method of stimulating the retina electrically, called suprachoroidal transretinal stimulation (STS), was shown to be effective in eliciting electrically evoked cortical potentials (EEPs) in Royal College of Surgeons (RCS) rats. Before extending this technique to patients, it is important to determine its safety and feasibility in eliciting EEPs from medium-size animal (rabbits). The purpose of this study was to determine the safety and efficacy of the surgical procedures used to implant an multichannel electrode array into a scleral pocket, and to determine whether the implanted electrodes can stimulate the retina effectively. METHODS: These acute experiments were conducted on six rabbits. An array of eight gold microelectrodes, embedded in polyimide, was implanted into a scleral pocket over the visual streak area. The size of the microarray was 2 x 4 x 0.180 mm. The reference electrode was implanted into the vitreous. The electrode array and reference electrodes were connected to a stimulator to deliver monophasic current pulses. Cortical responses were recorded with a stainless steel electrode implanted into each rabbit's skull over the visual cortex. After the experiment, the eyes and electrodes were examined histologically. RESULTS: The surgical procedures for electrode implantation were accomplished without serious complications. EEPs were recorded after monophasic electrical pulse stimulation from each electrode. The mean threshold for EEPs was 55.0+/-10.0 microA with a 0.5-ms duration inward current pulse. The charge delivered at threshold was about 27.5 nC, and the charge density was about 56.0 microC/cm2. Histopathological examination of the retinal tissue around the area of stimulation did not show damage at the light microscope level with the electrical parameters used. CONCLUSIONS: Our technique for STS with an intrascleral microelectrode array is safe in rabbit eyes, and EEPs were elicited by current densities that did not induce tissue damage. These results suggest that STS via intrascleral multichannel electrodes is a feasible method for stimulating the retina.

Animals↗

PubMed2004

Direct stimulation of optic nerve by electrodes implanted in optic disc of rabbit eyes.

PURPOSE: To determine whether wire microelectrodes implanted in the optic disc can be used to elicit cortical potentials. METHODS: Two or four platinum wire electrodes of two types, viz., the cut-end type and the exposed-tip type, were inserted through the vitreous and fixed in the optic disc of 16 rabbit eyes. Electrically evoked potentials (EEPs) were recorded after bipolar electrical stimulation with the two wire electrodes and by different combinations of the four-electrode system. The optic discs were examined histologically after the experiment. RESULTS: The wire electrodes were successfully implanted and fixed into different positions of the optic disc without serious complications in all 16 eyes. EEPs could be elicited after bipolar electrical stimulation of the optic nerve using either the two-electrode system or different pairs of the four-electrode system. Threshold charge densities to elicit EEPs were 0.32-0.64 mC/cm(2) in eyes using the cut-end type of electrodes and 0.93-6.21 muC/cm(2) in eyes using the exposed-tip type. The amplitude of the EEPs increased with increasing electrical stimulus intensities. Histological evaluation revealed limited damage to the neural tissue adjacent to the electrode track. CONCLUSIONS: The visual cortex can be activated by direct microelectrical stimulation of the optic nerve. The acute implantation of the wire microelectrodes into the optic disc by a transvitreal approach is feasible and results in only limited damage to the optic nerve.

Animals↗

PubMed2004

Wide-angle viewing lens for vitrectomy.

PURPOSE: To report a new wide-angle viewing contact lens for vitrectomy. DESIGN: New surgical instrument. METHODS: The new wide-angle viewing lens is made of glass and polymethyl methacrylate without a plastic rim. The diameter is reduced to 16.2 mm. In addition to a smaller diameter than the currently available lens, the new lens is partially cut to reduce the lens diameter. RESULTS: A smaller diameter makes it possible to eliminate contact between surgical instruments and the wide-angle lens. Instruments can be inserted through sclerotomies without removing the wide-angle lens. The optical properties are otherwise identical to the standard wide-angle lens. CONCLUSION: The new wide-angle viewing lens may be easier to use in vitreous surgery.

Contact Lenses↗

PubMed2004

Vitrectomy and internal limiting membrane peeling for myopic foveoschisis.

PURPOSE: Myopic foveoschisis is common in high myopia. We report results of a pilot study of vitrectomy for patients with myopic foveoschisis. DESIGN: Interventional case series. METHODS: In an institutional setting five patients with high myopia (six eyes), and who had progressive visual impairment presumably due to myopic foveoschisis were studied. No eyes had a macular hole preoperatively based on optical coherence tomography (OCT). We performed vitrectomy including vitreous cortex removal, internal limiting membrane (ILM) peeling, and gas tamponade. Patients were followed for at least 6 months. Best-corrected visual acuity (BCVA), OCT. Scanning laser ophthalmoscope (SLO) microperimetry was examined in three eyes. RESULTS: The foveal detachment resolved completely in five eyes and partially in one eye. No serious complications developed including macular hole formation or retinal detachment; BCVA improved more than two lines in all eyes (100%) 6 months postoperatively (P <.01); SLO microperimetry showed smaller scotoma compared with preoperatively and stabilized fixation. CONCLUSIONS: Vitrectomy with vitreous cortex removal, ILM peeling, and gas tamponade could be useful to treat myopic foveoschisis in highly myopic eyes. Because the natural course of the disease is not well-understood, further study should establish indications for this surgery.

Basement Membrane↗

PubMed2004

Posterior vitreous detachment and macular hole formation in myopic foveoschisis.

PURPOSE: To report two cases of macular hole (MH) associated with myopic foveoschisis (MF). DESIGN: Interventional case report. METHODS: Two women presented with metamorphopsia. Preoperative optical coherence tomography (OCT) showed an MH and MF. We performed vitrectomy, internal limiting membrane (ILM) peeling and gas tamponade. RESULTS: Preoperative OCT examination and intraoperative microscopic observation revealed partial posterior vitreous detachment (PVD) at the posterior retina and vitreous strands adhering to the edge of the MHs. The MF resolved in both patients, but the MHs remained open postoperatively. CONCLUSIONS: Although the contribution of tangential traction cannot be excluded, the mechanism of MH formation in eyes with MF may be anteroposterior traction via abnormal vitreofoveal adhesion resulting from partial PVD.

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PubMed2004

Multiple components of epiretinal tissues detected by triamcinolone and indocyanine green in macular hole and retinal detachment as a result of high myopia.

PURPOSE: To examine three layers of membranes detected by triamcinolone acetonide (TA) and indocyanine green (ICG) during surgery for macular hole and retinal detachment (MHRD) as a result of high myopia. DESIGN: Histologic study. METHODS: We excised three layers of membranes visualized with TA and ICG that were tightly adhering to the retinal surface during vitrectomy and examined them by transmission electron microscopy. RESULTS: The first membrane was made of acellular collagen fibers, suggestive of vitreous, and the second was comprised of parts of fibroblast-like cells and collagen fibrils, suggesting a proliferative epiretinal membrane. The third membrane was an internal limiting membrane. CONCLUSIONS: Multiple components of epiretinal tissue could be delaminated with the assistance of TA and ICG during surgery for myopic MHRD.

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