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S Yoneya

Publications and source records attributed to S Yoneya.

At least 37 records · Page 2Linked to original sources
PubMed1998

[Chorioretinal malformation in vascular loop formation on the optic disc].

We have studied the eyes of a 57 year-old man, with good visual acuity, who was found to have an unusual prepapillary vascular loop formation in both eyes. Ophthalmoscopic examination revealed that the central retinal vein ran a course beneath the retinal pigment epithelium in right eye. Fluorescein angiography showed the prepapillary vascular loops to originate from the central retinal artery in both eyes. We also noted arterial, but not arteriovenous, shunt formation in the retina of both eyes. By indocyanine green angiography we demonstrated the presence of a drainage system, the so called posterior ciliary vein, which was connected directly to the central retinal vein temporal to the optic disc in the right eye. We believe this to be a new type of chorioretinal vascular formation which is different from the chorio-vaginal vein and the optico-ciliary vein.

Choroid↗
PubMed1998

Binding properties of indocyanine green in human blood.

PURPOSE: Binding properties of indocyanine green (ICG) to human plasma proteins were identified using electrophoresis and a fundus video system. METHODS: Blood samples were obtained from three healthy volunteers after intravenous administration of ICG. The resulting plasma samples were fractionated by agarose gel immunoelectrophoresis and polyacrylamide gel DISC electrophoresis. In the former, antisera, anti-apolipoprotein (Apo)-A, and anti-Apo-B antibodies were used to identify all classes of plasma proteins, high-density lipoprotein (HDL), and low-density lipoprotein (LDL), respectively. In the latter method, plasma samples could be separated into chylomicron, very low-density lipoprotein, LDL, and HDL. The electrophoretic pattern obtained by each method was observed with an ICG fundus video system. Furthermore, we studied the affinity of ICG for lipids that were common molecular components of HDL and LDL. Four kinds of ICG solutions mixed with phospholipid, free cholesterol, esterified cholesterol, and triacylglycerol were observed with the ICG fundus video system. RESULTS: Both electrophoretic studies showed that ICG bound intensely to HDL and moderately to LDL, and only the solution with phospholipid fluoresced brightly when observed with the ICG fundus video system. CONCLUSIONS: These findings indicated low vascular or tissue permeability of ICG, which is caused by the larger molecular size of HDL and LDL. Also noted was that the ICG fluorescence observed in the angiogram may be equivalent to the hemodynamics of HDL alone or in combination with LDL in the bloodstream. This biochemical consideration may be a basis for the further understanding of ICG angiography.

Blood Proteins↗
PubMed1998

[Apoptotic changes after pressure-induced ischemia-reperfusion injury in the rat retina].

50 eyes of 30 Sprague-Dawley rats were subjected to 60 minutes of pressure-induced ischemia, then fixed for light and electron microscopy with no reperfusion, or reperfusion after 30 minutes, 1, 2 or 4 hours, and 1 or 3 days from the time ocular ischemia was relaxed. The TdT-mediated dUTP-biotin nick end labeling (TUNEL) method revealed apoptotic signs at the inner retina as early as 1 hour after reperfusion. However, the incidence of apoptotic signs with the TUNEL method did not accord with the results of electron microscopic examination. During the time after the reperfusion started, especially after more than 4 hours, apoptotic signs became obvious and extended from the inner to the outer retina. These apoptotic findings could be seen with both the TUNEL method and electron microscopy. By 3 days after the reperfusion, necrotic cells in the ganglion cell layer, and the inner and outer nuclear layer became more prominent than apoptotic cells. These results may provide a baseline for therapeutic strategy and the prognosis of ischemia-reperfusion injury in the retina.

Animals↗
PubMed1997

[Potential of photodynamic therapy with a second-generation sensitizer: mono-L-aspartyl chlorin e6].

We evaluated the potential for photodynamic therapy of a new photosensitizer, mono-L-aspartyl chlorin e6 (NPe6), whose tissue uptake and clearance are rapid. Firstly, NPe6 solution was exposed to a diode laser at 664 nm that fits the maximum absorption of NPe6. Immediately after laser exposure, the solution was subjected to electron spin resonance (ESR) to detect generation of activated oxygen species. With ESR, O2-, .OH, and 1O2 were detected in the NPe6 solution. O2- and .OH disappeared when superoxide dismutase was added to the solution. Next, the fundi of pigmented rabbits were irradiated with the diode laser after administration of NPe6. Histopathologically, there was necrosis of endothelial cells and vascular occlusion in the choroid, especially in the choriocapillaris. Retinal pigment epithelial cells were also injured. In contrast, the sensory retina was undamaged even after use of a large amount of dye. This new combination of NPe6 and diode laser at 664 nm enables us to occlude choroidal vessels efficiently by generating various activated oxygen species. Thus, photodynamic therapy with NPe6 is potentially useful in treating retinochoroidal involvement.

Animals↗
PubMed1997

[Angiography by scanning laser ophthalmoscope with fluorescein compounds of different physicochemical properties].

We performed angiography in photocoagulated eyes using four fluorescent dyes that have different molecular weight, lipid solubility, and electric charge. These findings were compared with those of sodium fluorescein (Naf) and indocyanine green (ICG). Angiograms were obtained with Naf, ICG and two fluorescein isothiocyanate dextrans at different molecular weight (FITC-D4: MW 4,400, FITC-D40: MW 38,900). We also used two other dyes: carboxyfluorescein (Caf: less lipid soluble) and calcein (Calc: a highly negatively charged molecule). Two and four days after laser photocoagulation of retina, dye leakage was still evident at the photocoagulated sites with Naf, Caf, Calc and FITC-D4. Angiograms taken after Caf and Calc injection showed more intense and rapid dye leakage than with Naf. Contrary to this, little dye leakage was observed with ICG and FITC-D40. These findings indicated that the critical molecular weight for permeation lay between 4,400 and 38,900 once the breakdown of blood retinal barrier occurred. In addition, difference in molecular weight is a major factor determining dye permeability at the photocoagulated retinal lesions, among other possibilities such as lipid solubility and electric charge.

Animals↗
PubMed1997

[Fundus hypothermia inhibits retinal damage induced by visible blue light].

We evaluated the role of fundus hypothermia in modifying photic retinopathy. The fundus was cooled with a copper plate inserted behind the eyeball. The anterior end of the plate was chilled with dry ice. Retinal temperature was thus reduced to 30 and 33 degrees C. This cooling manipulation had no effect on body temperature, retinochoroidal architecture, or choroidal circulation. The fundus was then exposed to visible blue light at an irradiance of 8 mW/cm2 for one hour. Retinal damage developed in 9 out of 10 eyes after the exposure alone, and in 3 out of 10 eyes when retinal temperature was reduced to 30 degrees C. The incidence of light damage with the cooling manipulation was decreased significantly when compared to that of controls (p < 0.05). Contrary to this, 5 out of 5 retinas treated with hypothermia at 33 degrees C showed damage and there was no significant difference in the incidence from that of controls. This finding indicates that local hypothermia at 30 degrees C protects the retina from light damage and that a subtle temperature milieu plays a role in producing retinal damage.

Animals↗
PubMed1996

[Vitrectomy with autoserum for idiopathic macular hole].

Using autoserum, we operated on eyes with full thickness macular hole and achieved greater anatomic and visual success than with eyes that underwent vitrectomy alone. A total of 34 eyes were treated with vitrectomy and fluid-gas exchange: 14 eyes with autoserum instillation and 15 eyes without autoserum. Five eyes with macular holes persisting after initial vitrectomy underwent reoperation with autoserum. After vitrectomy and fluid-air exchange, 0.1 to 0.3 ml of autoserum was placed for about 7 minutes over the hole, and then 30% SF6 was instilled. After treatment, successful anatomic closure occurred in 53% of the eyes without autoserum, in 86% of those with autoserum, and in 80% of those which underwent reoperation with autoserum. Visual acuity improved 2 lines or more in 53% of the eyes without autoserum, in 79% of those with autoserum, and in 60% of those that underwent reoperation with autoserum. The results of the current preliminary study shows that treatment of full-thickness macular holes with autoserum seems to be more beneficial than vitrectomy alone.

Blood↗
PubMed1996

[A study of serum protein fraction binding to indocyanine green (ICG) by combined method of immunoelectrophoresis and ICG fundus videosystem].

Binding characteristics of indocyanine green (ICG) to human serum were investigated, with a combination of immunoelectrophoresis and an ICG fundus video system. Serum samples were obtained from three healthy volunteers, 1 minute after intravenous administration of 50 mg/2 ml ICG, and then fractionated immunoelectrophoretically on agarose plates. Electrophoretic patterns on these plates could be observed with an ICG fundus video system as well as an immunoviewer. Using anti-human sera, only one infrared fluorescent line showing the ICG binding immunoprecipitate was recognized near the area of beta fraction, which was also identified by the use of anti-beta-lipoprotein (Lp) antibody. We also studied the affinity of ICG for apolipoproteins (Apo) AI, B, and CIII, which were the main protein components of serum Lps. Electrophoresis showed that ICG bound only to Apo-B, but not to the others. These results indicated that ICG mainly bound to beta-Lp in the blood, and that ICG angiographic patterns were directly reflecting the dynamics of serum Lps, especially for LDL. The high affinity of ICG for only Apo-B could explain the reason why ICG mainly bound to beta-Lp among several serum Lps, because large amounts of Apo-B are included in beta-Lp but a little in other serum Lps.

Apolipoproteins B↗
PubMed1995

[Fundus hypothermia at 29 degrees C prevents ischemic injury of the outer retina].

We evaluated quantitatively the protective effect of local fundus hypothermia under pressure-induced ischemia using morphometric analysis. Retinochoroidal ischemia was produced in albino rabbit eyes by increasing the intraocular pressure for 60 minutes. During the ischemic procedure, a copper plate was inserted behind the eyeball. The retinal temperature in the posterior pole was thus reduced to 29 degrees C by placing solid carbon dioxide, and to 32 degrees C by placing an ice cube at the anterior end of the plate. Histopathological changes in the group with ischemia alone were obvious in visual cells and retinal pigment epithelial cells (RPE), but the retina treated with additional hypothermia was well preserved. In the retina with hypothermia at 29 degrees C, there was no significant difference from the controls in the mean thickness of the photoreceptor layer (PRL) and the RPE, and the average count of nuclei in the outer nuclear layer (ONL). In the retina with hypothermia at 32 degrees C, there was also no significant difference from the controls in the thickness of the PRL and the RPE. Otherwise, the count of nuclei in the ONL decreased significantly when compared to that of controls (p < 0.001). These findings indicate that even mild hypothermia at 29 degrees C preserves the outer retina from ischemic damage and that the protective effect of hypothermia at 32 degrees C is insufficient.

Animals↗
PubMed1994

[Reaction of the retina to injected subretinal fluids].

Experimental retinal detachment was produced by injecting various fluids into the subretinal space in pigmented rabbits. We selected autologous aqueous humor, autologous vitreous, and autoserum as substitutes for subretinal fluid. Retinal detachment disappeared within 24 hours. The eyes were enucleated 7 days after surgery for histopathological study. Destructive changes in photoreceptor layer occurred most severely when the eye was treated with serum. There was a decrease in the number of outer nuclear layer cells. Macrophages and fibroblastic cells had migrated into the subretinal space. Histopathological changes with vitreous were less pronounced than with serum. The cytoplasm of Mueller cells appeared to compensate for the loss of photoreceptor cells in the outer nuclear layer. Mild decrease in the number of photoreceptor cells was the sole pathological feature when the eye was treated with aqueous humor. The retina thus showed different reactions to the subretinal fluids of differing nature.

Animals↗
PubMed1992

[Retinal damage induced by visible blue and near-infrared light of an operating microscope].

The authors evaluated possible hazards to the retina caused by the longer wavelength component in the illumination system of the surgical microscope. Thirty six pigmented and eleven albino rabbit eyes were exposed to blue or near-infrared light for 60 minutes. Ophthalmoscopically visible light damage to the retina developed in 4 of 5 pigmented rabbit eyes after illumination at a power setting of 8 mW/cm2 for blue and 50 mW/cm2 for near-infrared light. These power settings were equivalent to those used in clinical tests. The light damage developed immediately after illumination with near-infrared light and a few days after illumination with blue light. No light damage developed in albino rabbits with near-infrared light at current power setting. The findings suggest the possibility that clinical retinal damage may develop in human eyes when exposed to near-infrared light from surgical microscopes.

Animals↗
PubMed1992

[Spectral absorption characteristics of ocular tissues].

We studied the ocular spectral characteristics of monkey and rabbit eyes in the range of 300 to 900 nm. Measurements were performed on dissected specimens of the cornea, lens, vitreous, sensory retina and retinal pigment epithelium (RPE) plus choroid. Xanthophyll and monkey blood were also studied. Components of the ocular media showed high absorption over the ultraviolet range. The absorption curve of the sensory retina was similar to that of the ocular media. RPE plus choroid showed high absorption over the whole spectral range, with gradual decrease in absorption above 600 nm. The specific absorption curve of both xanthophyll and blood became manifest only when diluted to more than 1:20,000 in the former and to more than 1:100 in the latter. The spectral absorption of the ocular tissue thus became specific only when the thickness or density of the tissue was within a certain range.

Animals↗
PubMed1992

[Fluorescein angiographic observation of cellular changes in the retinal pigment epithelium after laser photocoagulation].

Lesions in the retinal pigment epithelium (RPE) of 16 pigmented rabbits were produced by dye laser photocoagulation using with three different wavelengths: 514, 577 and 630 nm. The power setting and exposure time was the same throughout. The size of the coagulation spot was set either at 500 or 1,000 microns. The retinal lesions were examined by high resolution fluorescein angiography on day 2, 7 and 30 after photocoagulation. Scanning electron microscopic examination of RPE was also performed in selected cases. On fluorescein angiography, the damaged RPE cells appeared as negative fluorescent spots with intense fluorescent margins, throughout the period of observation. The size of the lesion also remained constant. There were no difference in the damage or recovery of RPE cells in relation to the 3 different laser wavelengths. In some area of lesion, the fluorescein angiographic findings closely matched those observed by scanning electron microscopy.

Animals↗
PubMed1991

Retinal and vitreal neovascularization in retinopathy of prematurity. A scanning electron microscopic study in the kitten.

The angioarchitecture of vitreal and retinal neovascularizations produced experimentally in the eyes of kittens aged 2 to 9 weeks was studied with scanning electron microscopy. Various forms of new retinal and vitreal vessels were observed depending on topographic locations. Intraretinal neovascularization was observed at the retinal periphery as it grew toward the avascular zone in forms of short vascular buds, aneurysmal outgrowths, and neovascular loops. Posterior or to this frond of neovascularization, intertwining intraretinal telangiectasia was observed. At the posterior pole, capillaries with microaneurysms extended posteriorly toward the deeper layers of the retina from the vascular trunks at the nerve fiber layer. Vitreal neovascularization broke through the internal limiting membrane and exhibited aneurysmal outgrowths, clusters of glomerular swellings, and sinusoidal vascular channels. At the optic disc, vitreous neovascularization took the form of aneurysmal outgrowths and long vascular buds. Vitreal neovascularization showed different characteristics from the intraretinal neovascularization. We hypothesize that the topographic variation of the angioarchitecture of retinal and vitreal neovascularizations depends on the maturity of the vessels and might be related to the hemodynamics at each site.

Animals↗
PubMed1991

[Morphology of live retinal pigment epithelial cells].

We attempted to observe, by means of fluorescein angiography, the retinal pigment epithelial cells in pigmented rabbits. Fluorescein angiography was performed in 31 pigmented rabbits, after intravenous injection of 14mg/kg fluorescein sodium. The angiograms were evaluated as prints and as negative film under a light microscope. Animals were sacrificed and submitted to studies by scanning electron microscopy and fluorescein light microscopy. On fluorescein angiograms, we observed mosaic pattern which consisted of numerous polygonal spots overlying choroidal vasculature. Each polygonal spot showed central hypofluorescent area surrounded by hyperfluorescent rim. They were seen in all the eyes except 4 lightly pigmented eyes. They seemed to correspond, in size, to each retinal pigment epithelial cell. This pattern appeared from the early choroidal phase on, to become more distinct 5 to 15 minutes after dye injection. A hexagonal pattern was regularly seen away from the medullary rays by 3 or more disc diameters. The pattern became larger in the periphery than in the posterior pole. These angiographic findings closely matched those of retinal pigment epithelial cells as seen by scanning electron microscopy and fluorescein light microscopy in sizes and shapes. The findings indicate that it is possible to identify retinal pigment epithelial cells in pigmented rabbits by conventional fluorescein angiography.

Animals↗