PubMed Health⌕ Search

Biomedical subjects

Masayuki Horiguchi

Publications and source records attributed to Masayuki Horiguchi.

At least 19 recordsLinked to original sources
PubMed2006

Retinal blood flow and macular edema after radial optic neurotomy for central retinal vein occlusion.

PURPOSE: To determine the effect of radial optic neurotomy (RON) on retinal blood flow (RBF) and macular edema in eyes with a central retinal vein occlusion. DESIGN: Prospective interventional study. METHODS: Seven eyes of seven patients with central retinal vein occlusion underwent RON and vitrectomy and were followed for at least 6 months. The RBF was calculated from dye dilution curves of video fluorescein angiograms. The foveal thickness was determined by optical coherence tomography. RESULTS: At 1 week after surgery, the RBF was significantly reduced from 28.5 +/- 5.4 to 21.1 +/- 6.6 pixel(2)/s (P < .01). At 6 months after surgery, the RBF (26.0 +/- 7.7 pixel(2)/s) was not significantly different from the preoperative RBF, although chorioretinal anastomoses were found in all seven eyes. The foveal thickness was significantly decreased from 711 +/- 271 to 488 +/- 182 mum (P = .03). The postoperative visual acuity was better than the preoperative visual acuity by two or more lines in three out of seven eyes, and was worse in two eyes. CONCLUSIONS: Neither RON nor chorioretinal anastomoses improved the RBF but macular edema was improved. These findings suggest that removal of the vitreous could reduce macular edema as in diabetic macular edema. However, we cannot exclude the possibility that the changes represent the natural course of this disease.

Adult↗
PubMed2006

Effects of basic fibroblast growth factor on experimental diabetic neuropathy in rats.

Basic fibroblast growth factor (bFGF) stimulates angiogenesis and induces neural cell regeneration. We investigated the effects of bFGF on diabetic neuropathy in streptozotocin-induced diabetic rats. Diabetic rats were treated with human recombinant bFGF as follows: 1) intravenous administration, 2) intramuscular injection into thigh and soleus muscles with cross-linked gelatin hydrogel (CGH), and 3) intramuscular injection with saline. Ten or 30 days later, the motor nerve conduction velocity (MNCV) of the sciatic-tibial and caudal nerves, sensitivity to mechanical stimuli, sciatic nerve blood flow (SNBF), and retinal blood flow (RBF) were measured. Delayed MNCV in the sciatic-tibial and caudal nerves, hypoalgesia, and reduced SNBF in diabetic rats were all ameliorated by intravenous administration of bFGF after 10, but not 30, days. Intramuscular injection of bFGF with CGH also improved sciatic-tibial MNCV, hypoalgesia, and SNBF after 10 and 30 days, but caudal MNCV was not improved. However, intramuscular injection of bFGF with saline had no significant effects. bFGF did not significantly alter RBF in either normal or diabetic rats. These observations suggest that bFGF could have therapeutic value for diabetic neuropathy and that CGH could play important roles as a carrier of bFGF.

Angiogenesis Inducing Agents↗
PubMed2005

Changes in multifocal electroretinograms induced by transpupillary thermotherapy.

OBJECTIVE: To determine retinal function after transpupillary thermotherapy (TTT) for subfoveal choroidal neovascularization using multifocal electroretinograms (mfERGs). METHODS: Multifocal electroretinograms were recorded before and after TTT (wavelength, 810 nm; diameter, 3 mm; duration, 60 seconds; power, 350 mW) in 9 eyes in 9 patients with subfoveal choroidal neovascularizations. The stimulus consisted of 7 hexagons; the central hexagon covered the laser-irradiated area and the surrounding 6 hexagons covered the nonirradiated area. Each recording was completed within 1 minute, and mfERGs were recorded periodically during the first 60 minutes after TTT and also at 24 hours and 1 week after TTT. RESULTS: The amplitude of mfERGs from irradiated areas was significantly reduced at 1 minute after TTT (P< .01) and then recovered soon. The peak time was prolonged at 15 minutes after TTT (P< .01), recovered to pre-TTT levels at 60 minutes, and then was prolonged again at 24 hours (P< .05) and 1 week (P< .05) after TTT. The mfERGs in nonirradiated areas were unchanged during the observational period. CONCLUSIONS: We found amplitude reduction in central focal ERGs at 1 minute after TTT, transient peak-time delay at 15 minutes, and a delay at 24 hours. Early reduction is probably directly caused by an increase in temperature during TTT as previously reported in focal flicker ERGs. Peak-time delays at 15 minutes and 24 hours may be caused by other factors, such as increased intracellular calcium (Ca(2+)), the release of nitric oxide or heat shock proteins, vasodilation, or change in choroidal neovascularization. Our findings indicate that recording mfERGs may be a useful tool for evaluating TTT procedures.

Adult↗
PubMed2005

Effect of arteriovenous sheathotomy on retinal blood flow and macular edema in patients with branch retinal vein occlusion.

PURPOSE: To determine the effect of arteriovenous sheathotomy on retinal blood flow (RBF) in eyes with branch retinal vein occlusion (BRVO). DESIGN: Interventional case series. METHODS: Seven eyes of 7 patients with BRVO underwent sheathotomy and were followed for more than 6 months. RESULTS: At 1 week postoperatively, the RBF in the affected vessels was significantly improved from 14.1 +/- 5.7 to 27.3 +/- 11.3 pixel(2)/sec (P < 0.01), and the foveal thickness (FT) was significantly reduced from 536 +/- 84 to 366 +/- 134 microm (P = 0.03). However, the RBF was reduced again to 11.7 +/- 7.7 pixel(2)/sec at 1 month postoperatively, and the FT was increased to 424 +/- 184 microm. CONCLUSIONS: Arteriovenous sheathotomy led to a transient improvement of the RBF and was effective in reducing macular edema. It is not clear whether the transient effect of sheathotomy affects the long-term visual acuity and macular edema.

Aged↗
PubMed2005

Central retinal vein occlusion with further reduction of retinal blood flow one year after radial optic neurotomy.

PURPOSE: To report a case of central retinal vein occlusion (CRVO) that had vitrectomy with radial optic neurotomy (RON), but the retinal blood flow (RBF) was still reduced 1 year later. DESIGN: Interventional case report. METHODS: An 80-year-old woman had undergone vitrectomy and RON for a CRVO. She had a complete ophthalmic examination, including the RBF analysis using the dye dilution method before and after RON. RESULTS: Seven months after RON, her visual acuity improved from 20/50 to 20/25, and her foveal thickness was decreased from 733 to 213 microm. Indocyanine green angiography demonstrated chorioretinal anastomoses. At 1 year postoperatively, the RBF was reduced from 23.2 to 18 0.1 pixel(2)/s, and the foveal thickness was increased to 767 microm. Her visual acuity decreased to 20/100. The chorioretinal anastomoses were still patent. CONCLUSIONS: These results demonstrate that a further reduction of RBF can occur after RON, and blood flow in the chorioretinal anastomoses may be insufficient to prevent the event.

Aged↗
PubMed2005

Spatial and temporal properties of interocular timing differences in multifocal visual evoked potentials.

The multifocal VEPs (mfVEPs) obtained from the right and left eyes are practically identical in shape and amplitude, however small differences in the implicit times (ITs) have been reported. We have analyzed the ITs in detail to show that they are dependent on the radial location of the stimulus in the visual field. The differences are large, up to 8.3 ms, near the horizontal meridian, and are probably due to differences in the distances of the nasal and temporal ganglion cell axons from the optic disc. The intraretinal conduction velocity of ganglion cell axons, determined by dividing the axonal length to the optic disc by the ITs, was 0.29 m/s at an eccentricity of 0.5-1.4 degrees and 1.39 m/s at 8-12 degrees .

Adult↗
PubMed2005

Suppression by an h current of spontaneous Na+ action potentials in human cone and rod photoreceptors.

PURPOSE: The sense of vision in humans is robust, and visual flickering is rarely experienced. To investigate this mechanism, electrophysiological and molecular biological techniques were used on human cone and rod photoreceptors. METHODS: Voltage-gated currents were recorded using the patch-clamp technique on isolated human cones, and especially their voltage-gated Na+ currents were analyzed in detail. Whether Na+ channel transcripts could be detected in single photoreceptors using RT-PCR was also examined, to test the expression of voltage-gated Na+ channels in cones and/or rods. RESULTS: Under current-clamp conditions, blocking h currents (hyperpolarization-activated cationic currents) with Cs+, Tl+, or ZD7288 hyperpolarized the resting potentials of cones and rods by approximately 10 to 15 mV, and surprisingly generated spontaneous action potentials. The spontaneous spikes were blocked by 1 microM tetrodotoxin, but not by 1 mM Co2+, suggesting that they were Na+ spikes rather than Ca2+ spikes. Under voltage-clamp conditions, application of Cs+ and ZD7288 markedly decreased the steady inward current through the h channel. This is consistent with Cs+-induced hyperpolarization under a current-clamp condition. SCN2 Na+ channel was observed in both cones and rods by single-cell RT-PCR analysis, suggesting that human photoreceptors express the SCN2 Na+ channel. CONCLUSIONS: The data confirmed that voltage-gated Na+ channels were expressed not only in human rods but also in cones by electrophysiological and molecular biological experiments. These results suggest that the h current may contribute to preventing visual flickering by inhibiting the generation of spontaneous Na+ spikes in human photoreceptors.

Action Potentials↗
PubMed2004

Tomographic and multifocal electroretinographic features of idiopathic epimacular membranes.

OBJECTIVE: To determine the relationship between the tomographic and electrophysiologic characteristics of the retina with an idiopathic epimacular membrane. METHODS: Sixty patients with unilateral idiopathic epimacular membranes underwent optical coherence tomography and multifocal electroretinography (mfERG). The mfERGs were elicited by a pseudorandom m-sequence stimulus with 37 hexagonal elements, and the mfERGs in area 1 (central 4.1 degrees ), area 2 (ring from 4.10 degrees -7.15 degrees ), and area 3 (ring from 7.15 degrees -13.75 degrees ) were compared with the tomographic features of the corresponding area. The data from the normal fellow eyes served as control. MAIN OUTCOME MEASURES: The retinal thickness, amplitudes, and implicit time of the mfERG. RESULTS: On optical coherence tomographs, the retina was thickest in area 1, followed by area 2 with low tissue reflectivity of the outer retina, and area 3 was of normal thickness. Electroretinography showed the amplitude ratio (affected vs fellow eyes) of mfERGs from areas 1, 2, and 3 was significantly lower than that of the controls (P<.01), and the implicit times were significantly delayed (P<.01). The amplitude ratio was reduced the most in area 1, and the implicit time was delayed the most in area 3. The foveal thickness was negatively correlated with visual acuity (rho = -0.46; P<.001). The mfERG amplitude in area 1 was not significantly correlated with the visual acuity. CONCLUSIONS: It is likely that retinal thickness is correlated with neural dysfunction, but mfERGs demonstrated various physiological changes in the retina.

Adolescent↗
PubMed2004

Effect on visual outcome after macular hole surgery when staining the internal limiting membrane with indocyanine green dye.

OBJECTIVES: To determine the effect on the visual outcome after macular hole surgery when staining the internal limiting membrane (ILM) with indocyanine green (ICG) dye and to study the mechanism of the adverse effects. PATIENTS AND METHODS: We studied 40 eyes of 38 patients with an idiopathic macular hole (size, <0.5 disc diameter; duration, <12 months). The concentration, exposure time, and amount of the ICG solution that was minimally required to make the ILM visible were determined. The patients were randomly divided into group 1 (20 eyes of 19 patients) who underwent ILM peeling without ICG staining, and group 2 (20 eyes of 19 patients) who underwent ILM peeling with ICG staining. Routine examinations were conducted during the 12-month follow-up period. Multifocal electroretinogram, optical coherence tomography, and fluorescein angiography were performed on 31 eyes of 30 patients. RESULTS: The macular hole was closed in all patients. Visual acuity was improved in both groups, but it was significantly better in group 1 (median, 0.85) than in group 2 (median, 0.60; P =.02) after 12 months. The improvement of visual acuity in group 1 (logarithm of the minimum angle of resolution [logMAR] units [SD], 0.82 [0.19]) was significantly better than that in group 2 (logMAR units, 0.67 [0.21]; P =.30). The multifocal electroretinogram and optical coherence tomographic findings were not significantly different in the 2 groups. Fluorescein angiogram showed only weak hyperfluorescence at the macula in some patients of both groups. CONCLUSIONS: The results suggest that ICG staining should not be used as long as the visibility of the retinal surface is good. However, ICG staining may be acceptable at a low concentration when a clear view of the retinal surface is unattainable. The results of the multifocal electroretinogram, optical coherence tomography, and fluorescein angiography suggest that the differences in visual recovery were caused not only by pigment epithelial cell damage or retinal toxic effect but also probably by the effect of ICG staining on ganglion cells and their axons.

Axons↗
PubMed2004

Retinal blood flow analysis using intraoperative video fluorescein angiography combined with optical fiber-free intravitreal surgery system.

PURPOSE: To report a new method to perform intraoperative video fluorescein angiography (VFA) using an optical fiber-free intravitreal surgery system (OFFISS) and retinal blood flow analysis during surgery. DESIGN: Observational case series. METHODS: Four eyes of four patients with macular edema as a result of branch retinal vein occlusion underwent vitrectomy and intraoperative VFA with a bolus of 0.8 ml fluorescein dye. The segmental blood flow was calculated using dye dilution technique. Intraocular pressure was maintained at 15 mm Hg. RESULTS: The VFA was clearly recorded with stable excitation light and very little eye movement under retrobulbar anesthesia. The segmental blood flow of the affected vessels (6.1 +/- 1.2 pixel(2)/s) was significantly lower than that of the healthy vessels (17.9 +/- 7.9 pixel(2)/s) (P < .05). CONCLUSION: The combination of VFA and OFFISS can facilitate intraoperative VFA, and may be useful for evaluating retinal blood flow during surgery.

Aged↗
PubMed2003

Kinetics of indocyanine green dye after intraocular surgeries using indocyanine green staining.

OBJECTIVE: To determine the elimination kinetics of indocyanine green (ICG) after intraocular operations using ICG staining. METHODS: Intraocular fluorescence of ICG was determined using the ICG angiographic mode of a scanning laser ophthalmoscope (in vivo) and fluorescence microscopy (in vitro) after circular curvilinear capsulorhexis with ICG staining during cataract surgery and internal limiting membrane (ILM) peeling with ICG staining during macular hole surgery. SUBJECTS: We studied 9 eyes of 7 patients with white cataracts and 14 eyes of 14 patients with idiopathic macular holes. RESULTS: Scanning laser ophthalmoscopy revealed fluorescence in the anterior segment of patients with cataracts on the first postoperative day, and fluorescence remained for a mean +/- SD of 6.0 +/- 2.2 days postoperatively. Scanning laser ophthalmoscopy also revealed fluorescence in the posterior pole of patients with macular holes, and it remained for a mean +/- SD of 2.7 +/- 1.4 months postoperatively. Fluorescence microscopy showed fluorescence of the entire tissues, suggesting that ICG had stained not only the surface of the membranes but had also entered them. In both operations, visual outcomes were not significantly different from the results obtained without ICG. CONCLUSIONS: Because entire tissues were stained, the differences in ICG kinetics might also be caused by factors other than differences in stainability, such as the environment surrounding the tissues or molecular structural differences between the lens capsule and the ILM. Although we found complete disappearance of fluorescence and good functional recovery, the longer resident time of the dye after macular hole surgery may suggest a potential risk to intraocular tissues.

Adult↗
PubMed2003

Removal of lens material dropped into the vitreous cavity during cataract surgery using an optical fiber-free intravitreal surgery system.

We describe a technique for removing lens fragments dropped into the vitreous cavity during cataract surgery using an optical fiber-free intravitreal surgery system (OFFISS) that was developed for bimanual vitrectomy. The dropped nucleus was removed by 2-port corneal vitrectomy using the OFFISS in 3 patients during complicated cataract surgery. No complications occurred, and good visual recovery was achieved. The OFFISS provided a good view of the fundus without fiber optics and allowed the use of 2 ports for vitrectomy through the corneal wound. This technique is suitable for cataract surgeons who have not been trained in 3-port pars plana vitrectomy.

Cataract Extraction↗
PubMed2003

Stray light-induced multifocal electroretinograms.

PURPOSE: To evaluate the characteristics of stray light-induced response in multifocal ERG (mfERG) elicited by the stimulus falling on the disc. METHODS: A patient with an enlarged optic disc (4 x 4 disc diameters of disc of normal fellow eye) and four normal volunteers served as subjects. The mfERGs elicited by different stimulus intensities (0.67-4.67 cd-sec/m(2)) were recorded from the patient, and the mfERGs obtained with stimuli on the enlarged optic disc. For comparison, full-field pseudorandom ERGs (ffprERGs) were also recorded in all subjects. The first-order kernels (K1) and the second-order kernels (K2.1) were analyzed. RESULTS: A small and delayed K1 was recorded on the enlarged disc, but K2.1 was flat on the disc at all intensities. The implicit time of K1 at lower intensities was longer than at higher intensities. ffprERGs at very low intensities in the patient and normal subjects were similar to the mfERG on the disc (delayed K1 associated with flat K2.1). CONCLUSIONS: The responses elicited by stimulating the disc were delayed in K1 and flat in K2.1. Because similar ffprERGs were observed at very low intensities, it is likely that an optic disc with high reflectance scattered the stimulus light to create a weak full-field stimulus. Thus, care must be taken when focal lesions are investigated with mfERGs.

Adult↗
PubMed2003

Multifocal electroretinograms in cases of central areolar choroidal dystrophy.

PURPOSE: To study multifocal electroretinograms (mfERG) in patients with early-stage central alveolar choroidal dystrophy (CACD) with well-demarcated atrophic areas. METHODS: Eight eyes of eight patients with CACD (ages, 47-67 years) and 20 normal control subjects were examined. The first- and second-order kernels (K1 and K2) were extracted from the responses elicited by 61 standard hexagonal elements of a visual response imaging system. The amplitudes and peak times of the focal responses at various retinal eccentricities were studied. RESULTS: The amplitudes of K1 were reduced in the visibly atrophic areas, and they were also decreased in areas with no visible atrophy. The peak time was slightly delayed in many loci, but the delay was not as long as that in congenital stationary night blindness or diabetic retinopathy. The amplitude of K2 was very small in the central and peripheral areas, but the K2/K1 ratio in both areas was not significantly reduced, compared with that in normal subjects. CONCLUSIONS: Although the atrophic area was ophthalmoscopically well demarcated in patients with CACD, the abnormality of retinal function extended beyond the borders of the ophthalmoscopic and angiographic lesions. The retinal dysfunction outside the atrophic areas suggests a centrifugal progression of the disease, and abnormal K2 and K1 with preserved K2/K1 ratio are consistent with a presynaptic mechanism for the retinal dysfunction in this disease.

Adult↗
PubMed2002

Modulation by hyperpolarization-activated cationic currents of voltage responses in human rods.

We used the whole-cell patch-clamp recording technique on surgically excised human retina to examine whether human rod photoreceptors express hyperpolarization-activated cationic currents (I(h)) and to analyze the effects of I(h) on rod's voltage responses. Hyperpolarizing voltage steps from a holding potential of -60 mV evoked a slow inward-rectifying current in both rods in retinal slices and isolated rods. The slow inward-rectifying currents induced by hyperpolarization were markedly reduced by 3 mM Cs(+) (a blocker of I(h)) in the bath, but not by 3 mM Ba(2+) (an anomalous rectifier K(+) current blocker) or 1 mM SITS (a Cl(-) current blocker). A concentration-response curve for block by Cs(+) of the inward currents could be fitted by the Hill equation with a half-blocking concentration (IC(50)) of 41 microM and a Hill coefficient of 0.91. The time course of the inward current activation was well described at all recorded voltages by the sum of two exponentials. Under current-clamp conditions, injection of steps of current, either hyperpolarizing or depolarizing, elicited an initial rapid voltage change that was followed by a gradual decay in the voltage response. The decay in the voltage responses was eliminated by bath application of 3 mM Cs(+). The voltage dependence, pharmacology, and kinetics of the slow inward-rectifying currents described above suggest that human rods express I(h). We suggest that I(h) becomes activated in the course of large hyperpolarizations generated by bright-light illumination and may modify the waveform of the photovoltage in human rods.

Adult↗
PubMed2002

New system for fiberoptic-free bimanual vitreous surgery.

OBJECTIVES: To describe a new system for fiberoptic-free bimanual vitrectomy and to present the outcome of 37 eyes with preretinal membranes due to diabetic retinopathy or proliferative vitreoretinopathy that underwent surgery using this system. METHODS: The system consists of a 40-diopter aspheric field lens suspended from the operating microscope and a prismatic inverting device. The aspheric lens is placed above the cornea, and the illumination from the operating microscope creates an inverted image of the fundus, which is made erect by an inverter system. No fiberoptics are required, and both hands are free to use 2 microinstruments. MAIN OUTCOME MEASURES: The practical utility of this system and its surgical results and complications. RESULTS: The system was used successfully in all cases. Membrane dissection and hemostasis were performed without incident. An improvement in visual acuity of 2 or more lines was found in 30 of 37 eyes. Five eyes did not reveal change of 2 or more lines, and 2 eyes had a decrease in visual acuity of more than 2 lines. There was no evidence of phototoxicity. CONCLUSION: This system is very useful for bimanual vitrectomy.

Diabetic Retinopathy↗
PubMed2002

Transparent irrigation cannula for bimanual lens cortex removal.

A transparent irrigation cannula was developed to facilitate bimanual removal of subincisional lens cortex after phacoemulsification. The cannula allows visualization of the proximal cortex and provides ample inflow to maintain an inflated anterior chamber even at a high aspiration pressure.

Catheterization↗