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Motohiro Kamei

Publications and source records attributed to Motohiro Kamei.

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

[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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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

Platelet aggregates in various stages of diabetic retinopathy: evaluation using the particle-counting light-scattering method.

AIMS: To investigate the possible correlation between platelet aggregation and the severity of diabetic retinopathy using the light-scattering method. METHODS: Using a light-scattering platelet aggregometer, we measured spontaneous platelet aggregation in 86 diabetics with retinopathy of varying severity and 30 healthy volunteers (controls). Platelet aggregates were classified as small, medium, and large according to their light intensity; patients were grouped based on the severity of retinopathy. In each patient group, we recorded for 10 min the total light intensities emitted by each aggregate size in the area under the curve (AUC). Then, we compared the AUC of each level of retinopathy severity with the controls and determined the correlation between the AUC of each aggregate size and each severity level. RESULTS: Of the 86 diabetics, 22 had no apparent retinopathy (NAR), 13 had mild nonproliferative diabetic retinopathy (NPDR), 17 had moderate NPDR, 12 had severe NPDR, and 22 had proliferative diabetic retinopathy (PDR). While the NAR group manifested significantly more small aggregates than the controls (20.5 x 10(6) versus 8.3 x 10(6) a.u., p=0.024), none of the other groups showed a significant increase in aggregates of any size. In the AUC of large aggregates, there was a weak-positive correlation with the severity of retinopathy (r=0.255, p=0.018); in the AUC of small and medium aggregates, there was no correlation. CONCLUSION: Although we did not find a significant correlation between platelet aggregation and the severity of diabetic retinopathy, our pilot study did detect some tendencies. Further studies on larger populations are underway to determine whether these tendencies are real.

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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

Proteomic analysis of vitreous from diabetic macular edema.

To identify and analyze diabetic macular edema (DME)-related proteins in the vitreous, en masse, using two-dimensional gel (2D gel) electrophoresis and mass-spectrometry (MS). Vitreous samples were corrected from 20 eyes with pre-proliferative diabetic retinopathy associated with DME (DME group) and without DME (non-DME group). They were subjected to 2D gel electrophoresis, and the spot intensities were compared between the groups. Apparently visible spots were excised from the gel, and the proteins were identified by liquid chromatography tandem MS (LC MS/MS) sequence analysis. We identified 14 proteins from the DME group, and 15 proteins from the non-DME group. The intensity of eight spots was markedly higher in DME than non-DME samples and one spot was detected only in non-DME samples. From the eight spots, six proteins were identified, including PEDF, ApoA-4, ApoA-1, Trip-11, PRBP, and VDBP. On the other hand, Apo H was expressed only in non-DME. Certain vitreous proteins expressed exclusively in DME and lacked in DME. These chemical mediators in the posterior vitreous may play a role in the pathogenesis of DME.

Diabetic Retinopathy↗
PubMed2005

The presence of Propionibacterium spp. in the vitreous fluid of uveitis patients with sarcoidosis.

PURPOSE: An immunological reaction to a bacterial antigen, such as Mycobacterium tuberculosis or Propionibacterium spp., is suspected to be an initial mechanism in the disorder known as sarcoidosis. We investigated whether or not P. acnes, P. granulosum or M. tuberculosis are present in the vitreous fluid of eyes suffering from uveitis with sarcoidosis. METHODS: Using polymerase chain reaction, we analysed the presence of P. acnes, P. granulosum and/or M. tuberculosis DNA in vitreous samples taken from six eyes with sarcoidosis and six control eyes. RESULTS: Among the six uveitis eyes with sarcoidosis, we detected P. acnes DNA in two eyes, P. granulosum DNA in four eyes, and both P. acnes and P. granulosum DNA in one eye, but no Propionibacterium spp. in the control eyes. M. tuberculosis DNA was not present in any of the patient or control eyes. CONCLUSIONS: This is the first report indicating the presence of Propionibacterium spp. and/or its DNA in the vitreous fluid of sarcoidic eyes with uveitis. This, therefore, supports the idea that Propionibacterium spp. are involved in the aetiology of uveitis in sarcoidosis.

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PubMed2005

[Low power transpupillary thermotherapy of choroidal neovascularization].

PURPOSE: To assess the effectiveness of low power transpupillary thermotherapy (TTT) for choroidal neovascularization (CNV). METHOD: We performed TTT on 55 eyes of 55 patients with subretinal CNV between April 2001 and December 2002, and observed them after therapy for more than 6 months. The laser power ranged from 80 to 320 mW when the spot size was 3 mm. We evaluated visual acuity, subretinal fluid (SRF), and CNV size. RESULTS: Visual acuity improved by 2 lines or more in 16 eyes (29%), was unchanged in 19 eyes (35%), and decreased in 20 eyes (36%). SRF decreased in 30 eyes (54%), was unchanged in 13 eyes (24%), and increased in 12 eyes (22%). CNV diminished in 33 eyes (60%), was unchanged in 10 eyes (18%), and became enlarged in 12 eyes (22%). CONCLUSIONS: Low power TTT can be an effective treatment for subgroups of patients with subfoveal CNV.

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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

Stage-dependent effect of pancreatic transplantation on diabetic ocular complications in the Spontaneously Diabetic Torii rat.

BACKGROUND: In terms of the temporal relationship between pancreas transplantation (PTx) and reversal of diabetic ocular complications, it has been difficult but important to determine a "point of no return." Thus, it is of great clinical interest to evaluate the efficacy of PTx on diabetic ocular complications. METHODS: A spontaneous type 2 diabetic model of Spontaneously Diabetic Torii (SDT; RT1) rats was used in the present study, and syngeneic PTx was performed. RESULTS: In the control SDT rats that received no treatment, hyperglycemia (>250 mg/dL) was developed from 25.2+/-3.9 weeks of age. Lens opacity was observed in all rats at 15 weeks after the onset of diabetes. Fluorescein angiography and immunohistochemistry detected the nonperfusion area and neovascularization in the retina at 5 weeks of diabetes. Daily insulin treatment could not prevent or reverse the ocular changes in our experiment. Fluorescein filling defect of the retinal vessels was observed at 10 weeks of diabetes. However, in the PTx rats, normoglycemia was achieved at all experimental time points. Diabetic cataract and retinopathy could have been prevented and improved if PTx had been performed at 5 weeks, but not at 10 weeks after the onset of diabetes. With PTx treatment, an inhibition of angiogenesis in the retina at 5 weeks after the onset of diabetes was demonstrated by immunohistochemistry. CONCLUSIONS: Our results indicate that the potential use of the SDT rat for diabetes study and the positive effect of PTx performed before the "point of no return" could prevent and cure diabetic ocular complications.

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

Macular translocation with chorioscleral outfolding: 2-year results.

PURPOSE: To evaluate the results of macular translocation with radial chorioscleral outfolding in patients with subfoveal choroidal neovascularization (CNV) and to identify factors associated with decreased postoperative visual acuity. DESIGN: Retrospective interventional case series. METHODS: Twenty-seven consecutive patients with surgically treated subfoveal CNV were operated on and followed for more than 2 years. Macular translocation with radial chorioscleral outfolding was performed using titanium clips. Surgical outcomes including visual acuity, foveal displacement, surgically induced astigmatism, and complications were recorded. Factors associated with decreased visual acuity postoperatively were identified by multiple logistic regression analysis. RESULTS: Foveal displacement ranged from 349 to 3391 (median, 1576) microm. Surgically induced astigmatism ranged from 0 to 3.0 (median, 0.5) diopters. Visual acuity after surgery improved in 19 of the 27 patients (70.4%; median, 5 lines), but in 14, final vision ultimately decreased from the best postoperative level. Final visual acuity improved from the preoperative level in 11 patients (40.7%), remained unchanged in seven (25.9%), and decreased in nine (33.3%). In our series, the mean preoperative vision was 20/174, the best postoperative visual acuity was 20/74, and the mean final vision was 20/167. Factors associated with a decrease in postoperative visual acuity included the postoperative enlargement of CNV. CONCLUSION: Macular translocation with radial chorioscleral outfolding improved or stabilized the vision in 66.7% of patients with subfoveal CNV over the course of more than 2 years. Closing the CNV or preventing its further growth is required to maintain a better postoperative visual acuity.

Adult↗
PubMed2004

Comparative effect of antiplatelet therapy in retinal vein occlusion evaluated by the particle-counting method using light scattering.

PURPOSE: To evaluate platelet aggregation in patients with retinal vein occlusion (RVO) by the light-scattering method and compare the effects of three antiplatelet drugs on aggregate formation. DESIGN: Prospective, nonrandomized, interventional clinical trial. METHODS: (1) Platelet aggregation was measured in 42 patients with untreated branch RVO (BRVO), 26 patients with central RVO (CRVO), and 30 healthy control subjects using a light-scattering platelet aggregometer. Platelet aggregates were classified as small, medium, and large according to light intensity. Total light intensities of each aggregate size were compared between BRVO, CRVO, and control subjects. (2) In 33 patients with RVO, platelet aggregation before and 2 weeks after the administration of ticlopidine, beraprost, or aspirin were compared. RESULTS: (1) There was a statistically significant difference (P = 0.0073) between the control subjects (8.3 x 10(6) a.u.) and CRVO patients (22.9 x 10(6) a.u.) with respect to small aggregates. There was no statistically significant difference with respect to medium and large aggregate formation between the control subjects and either patient group. (2) Compared with aggregates formed in the absence of antiplatelet drugs, ticlopidine significantly inhibited only the formation of small aggregates and beraprost that of all sizes; aspirin did not significantly inhibit the formation of any aggregate sizes. CONCLUSIONS: Increase in small platelet aggregates may be attributable to RVO pathogenesis. Beraprost and ticlopidine appear to inhibit small aggregate formation in RVO patients and may represent effective antiplatelet treatments. The light-scattering method is useful to investigate the pathogenesis of RVO and the effects of antiplatelet drugs.

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PubMed2004

Nonaxoplasmic transfer of indocyanine green into the optic nerve after intravitreal application.

PURPOSE: To investigate whether indocyanine green (ICG) migrates into the optic nerve after intravitreal application in the rabbit eye. METHODS: Gas vitrectomy was performed in one eye of adult Dutch belted rabbits by pars plana injection of 0.4 ml of 100% C3F8 (n = 10). One week later, vitrectomy was performed and 0.2 ml of 0.25% ICG was instilled into the vitreous cavity of these vitrectomized eyes. After 30 seconds of ICG application, the vitreous cavity was rinsed with balanced salt solution plus. Unoperated rabbits served as controls (n = 2). Globes, optic nerves, and the entire brain were removed, and ICG fluorescence of the specimens was examined with a digital fundus camera starting from the first day to the fourth postoperative week. Other rabbit eyes (n = 2) were injected with ICG directly into the vitreous without vitrectomy, and assessed for ICG signal after 1 day of ICG application. In the second part of the experiment, four rabbit eyes were gas vitrectomized and ICG was instilled onto retina after blockage of axonal flow by vinblastine. They were evaluated on the first (n = 2) and seventh postoperative days (n = 2). RESULTS: No fluorescein was detected in the visual pathways and the brains of the control group of rabbits. The optic nerves of the ICG-instilled eyes were stained diffusely with ICG starting from the first day after surgery. ICG injected nonvitrectomized eyes showed similar ICG staining patterns when compared with vitrectomized eyes. ICG staining pattern of the optic nerve did not differ in vinblastine-pretreated eyes. Fluorescence extended along the intraorbital portion of the optic nerve but did not transport more posteriorly in all animals. At the fourth week after vitrectomy, ICG signal was still detectable, but staining was less intense. CONCLUSION: Intravitreal ICG injection results in nonaxoplasmic extension into the optic nerve in the rabbit.

Animals↗
PubMed2004

Foveal sensitivity and fixation stability before and after macular translocation with 360-degree retinotomy.

PURPOSE: To evaluate the functional changes of the fovea by scanning laser ophthalmoscopy (SLO) fundus perimetry after macular translocation with 360-degree retinotomy, and to determine whether the preoperative macular function estimated by the sensitivity of the fovea and the stability of fixation can predict visual acuity after the surgery. METHODS: Macular translocation with 360-degree retinotomy and simultaneous torsional muscle surgery were performed on 25 eyes of 25 patients with choroidal neovascularization. The index of foveal sensitivity (Isens) and the index of fixation stability (Ifix) before and after surgery were calculated from the microperimetric data. The preoperative Isens and Ifix were compared with postoperative Isens and Ifix, respectively. The correlations of preoperative Isens and Ifix with the visual acuity after the translocation surgery (VApost) were calculated. RESULTS: Isens increased in 14 (56%) of 25 eyes. Ifix improved in 10 (40%) of 25 eyes. The preoperative Isens and VApost were moderately correlated (r = 0.434, P = 0.0295), while the preoperative Ifix and VApost were highly correlated (r = - 0.530, P = 0.0057). CONCLUSION: An increase in foveal sensitivity and an improvement in the fixation stability were demonstrated quantitatively by microperimetry. The preoperative foveal sensitivity and fixation stability were correlated with the postoperative visual acuity. Microperimetry using SLO can be used to investigate foveal function before and after the translocation and to predict the postoperative visual acuity.

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