Biomedical subjects

M Shirakashi

Publications and source records attributed to M Shirakashi.

At least 19 recordsLinked to original sources

PubMed2001

Mathematical and optimal clustering of test points of the central 30-degree visual field of glaucoma.

PURPOSE: To determine a mathematically optimal sector pattern of the central 30 degree visual field for the follow-up of glaucomatous visual field change based on a large number of actual visual field test data of patients with glaucoma. METHODS: Visual field test data obtained from 1,039 eyes of 1,039 patients with open-angle glaucoma (OAG) using the 30-2 program of the Humphrey Field Analyzer were used for sectorization of the central 30 degree visual field. Of the 1,039 visual field data, 698 (modeling data) were used for determining the sector pattern and 341 (testing data) for checking the sector pattern. The modeling data were further divided into three groups according to the mean deviation (MD) (MD > or = -10 dB, -20 < or = MD < -10 dB, and MD < -20 dB), and the sector pattern was constructed from visual field data of each group using a clustering procedure called VARCLUS. The testing data were used for determining the optimal sector pattern. In a separate set of repeated visual field data of 303 patients with OAG, the fluctuation of MD, sector values of each sector determined, and total deviation of each test point were calculated and compared. RESULTS: The sector pattern constructed from visual field data of MD > or = -10 dB summarized the visual field performance most effectively. The fluctuation of the sector value of each sector was roughly 1.5 times smaller than the total deviation of each test point. CONCLUSION: The sector pattern determined may be useful in analyses of the visual field data of patients with glaucoma.

Glaucoma, Open-Angle↗

PubMed2001

Expression and localization of angiogenic inhibitory factor, chondromodulin-I, in adult rat eye.

PURPOSE: To determine the role in the eye of chondromodulin (ChM)-I, which has been identified in cartilage as an angiogenic inhibitor, the expression and localization and a possible function of ChM-I were investigated. METHODS: Expression and localization of ChM-I in rat eyes were examined by RNase protection assay and in situ hybridization and by immunostaining, using an antibody against a synthetic peptide. The effect of recombinant ChM-I on tube morphogenesis of retinal endothelial cells was examined in culture. RESULTS: The rat ChM-I gene was determined to encode the open reading frame of 334 amino acid residues, and ChM-I mRNA was exclusively expressed in cartilage, eye, and cerebellum in rats. ChM-I mRNA expression was evident in the iris-ciliary body, retina, and scleral compartments, but not in other compartments of the eye. In situ hybridization revealed mRNA expression in the ganglion cells, inner nuclear layer cells, and pigment epithelium in the retina and in the nonpigment epithelium of the ciliary body. Immunoreactive ChM-I was present in these cells and also in the vitreous body. Western blot analysis detected an approximately 25-kDa band of ChM-I presumed as a secretory form in the aqueous humor and vitreous body and an approximately 37-kDa band as a precursor form in the retina. Recombinant human ChM-I inhibited tube morphogenesis of human retinal endothelial cells in vitro. CONCLUSIONS: These observations indicate a potential role for ChM-I in inhibition of angiogenesis in the rat eye.

Amino Acid Sequence↗

PubMed2001

[An ultrasound biomicroscopic study of eyes after non-penetrating trabeculectomy].

PURPOSES: We studied the control of intraocular pressure(IOP) by various types of blebs after non-penetrating trabeculectomy(NPT) and the difference between bleb formation after penetrating trabeculectomy(PT) and that after NPT. METHODS: The filtering blebs of 45 yeys from 40 patients after NPT were studied using ultrasound biomicroscopy. They were grouped into four types, and the space under the scleral flap was classified into three types. The filtering blebs and the space under the scleral flap were correlated with IOP level. RESULTS: Overall, 40% of the blebs were L(low-reflective) type, 16% H(high-reflective) type, 16% E (encapsulated) type, and 29% F(flattened) type, but in good IOP control cases 59% of the blebs were L type, 14% H type, 14% E type, and 14% F type. L type blebs were found in 94% of eyes with good IOP control. CONCLUSION: Though filtering blebs of the L type could produce sufficient IOP reduction, blebs after NPT showed a greater tendency to become flattened than after PT. Additional systematic therapy must be designed to maintain the L type of filtering blebs after NPT.

Glaucoma↗

PubMed2001

[Persistent hyperplastic primary vitreous--a case report of adult onset acute angle-closure glaucoma].

BACKGROUND: We report a patient with persistent hyperplastic primary vitreous(PHPV) who presented with acute angle-closure glaucoma in his adult life. CASE: A 30-year-old man had an attack of acute angle-closure glaucoma associated with retrolenticular fibrous tissue, atrophic retina, and elongated cilliary process in his right eye. RESULT: Ultrasound biomicroscopy(UBM) study showed iris bowing, shallow anterior chamber, and elongated cilliary body which were being pulled by the retrolenticular mass. The posterior chamber was normal. CONCLUSION: Although the mechanisms of secondary angle-closure glaucoma in PHPV are complicated, we suspected pupillary block resulting from constriction by the retrolenticular mass in this case.

Acute Disease↗

PubMed2000

Measurement of microcirculation in the optic nerve head by laser speckle flowgraphy and scanning laser Doppler flowmetry.

PURPOSE: To evaluate and compare blood flow measurements by laser speckle flowgraphy and scanning laser Doppler flowmetry in the optic nerve head of normal volunteers. METHODS: This prospective study included 60 eyes of 60 normal volunteers (50.0 years; range, 21 to 77 years). Measurements were taken at the temporal neuroretinal rim away from visible vessels. The square blur rate, a quantitative index of relative blood velocity, was measured by laser speckle flowgraphy. Using scanning laser Doppler flowmetry, volume, flow, and velocity were measured at the same neuroretinal rim locations. RESULTS: The average square blur rate, volume, flow, and velocity were 7.11 +/- 1.65, 7.74 +/- 3.19, 151.85 +/- 70.63, and 0.53 +/- 0. 23 arbitrary units, respectively (n = 60). Square blur rate correlated significantly with flow and velocity (r =.361, P =.005; r =.359, P =.005, respectively). However, there was no significant correlation between square blur rate and volume (r =.101, P =.441). Although square blur rate decreased significantly with increasing age (r = -.375, P =.003), volume, flow, or velocity showed no significant correlation with age (r = -.249, P =.054; r = -.166, P =. 205; r = -.143, P =.275, respectively). Square blur rate also decreased significantly with mean blood pressure (r = -.315, P =. 014), but volume, flow, or velocity showed no significant correlation with mean blood pressure (r = -.159, P =.225; r = -.059, P =.654; r = -.043, P =.742, respectively). CONCLUSION: We found only a weak correlation between the blood flow indexes, as measured by laser speckle flowgraphy and scanning laser Doppler flowmetry because of basic differences in the principles of measurement.

Adult↗

PubMed2000

Measurement of microcirculation in optic nerve head by laser speckle flowgraphy in normal volunteers.

PURPOSE: To report blood flow in the optic nerve head between the right and left eyes or the superior and inferior neuroretinal rims in normal volunteers using laser speckle flowgraphy. METHODS: This prospective study included 120 eyes of 60 normal volunteers (mean age, 50.0 +/- 16.9 years; range, 21 to 77 years). The square blur rate was measured by laser speckle flowgraphy (Kyushu Institute of Technology, Iizuka, Japan). The sequence of eye measurements was randomized. In each eye, measurements were taken at the neuroretinal rim away from visible vessels. Linear regression analysis, paired two-tailed t test, and two-way analysis of variance were used for statistical analysis. P values less than.05 were accepted as statistically significant. RESULTS: There was a significant correlation in square blur rate between the right and left eyes (r = 0.587, P <.001). Square blur rate in the superior temporal neuroretinal rim significantly correlated with that in the inferior temporal neuroretinal rim in each of the right (r = 0.546, P <.001) and left (r = 0.465, P <.001) eyes. Square blur rate in the right eye was higher than that in the left eye (P =.049). Square blur rate in the superior neuroretinal rim was higher than that in the inferior neuroretinal rim in both the right (P =.035) and left (P =. 005) eyes. CONCLUSION: There were statistically significant differences of optic nerve head blood flow in normal volunteers using laser speckle flowgraphy between the right and left eyes and between the superior and inferior temporal neuroretinal rims. These normal data can be used for understanding physiological ocular hemodynamics.

Adult↗

PubMed1999

Measurement of retinal nerve fibre layer by scanning laser polarimetry and high pass resolution perimetry in normal tension glaucoma with relatively high or low intraocular pressure.

AIMS: To determine whether any differences may exist in the relation between the neural capacity as determined by high pass resolution perimetry and the thickness of the retinal nerve fibre layer (RNFL) in patients having normal tension glaucoma (NTG) with a relatively high intraocular pressure (IOP) between 16 and 21 mm Hg (HNTG) v those with a lower IOP below 15 mm Hg (LNTG). METHODS: Scanning laser polarimetry and high pass resolution perimetry were performed in 20 eyes of 20 patients with HNTG and 21 eyes of 21 patients with LNTG. The correlation between total and regional thickness of the peripapillary RNFL and the corresponding total and regional neural capacity with linear regression analysis were evaluated. RESULTS: Overall, although the total RNFL thickness was not significantly correlated with the total neural capacity, the RNFL thickness in each of the superior and inferior quadrants was significantly correlated with the corresponding regional neural capacity (r = 0.44, p = 0.0045; r = 0.39, p = 0.0126 for each). The RNFL thickness in each of the superior and inferior quadrants in the HNTG group was significantly correlated with the corresponding regional neural capacity (r = 0.52, p = 0.0196; r = 0.49, p = 0.0286 for each). No significant correlation between neural capacity and the RNFL thickness was observed either globally or regionally in the LNTG group. CONCLUSION: The degree of the correlation between neural capacity as determined by high pass resolution perimetry and thickness of the RNFL as measured by scanning laser polarimetry appeared to differ in NTG patients with an IOP higher than 15 mm Hg v those with a lower IOP.

Adult↗

PubMed1998

The relationship between deterioration and reversal of optic disc cupping in monkeys with chronic experimental high-pressure glaucoma.

PURPOSE: To investigate the correlation between the deterioration in optic disc cupping during the chronic elevation of intraocular pressure (IOP) and the reversal of cupping during a subsequent reduction in IOP in experimental glaucoma. METHODS: We examined changes in the vertical and horizontal cup to disc ratios, the rim area to disc area ratio, and the cup volume to disc area ratio in 11 monkey eyes with laser-induced glaucoma using computerized stereo-image analysis. Correlations between changes in disc parameters during a spontaneous IOP reduction and changes in disc parameters during a period of chronic IOP elevation from baseline before laser exposure (baseline) to before the IOP reduction (pre-IOP reduction) and during the period from baseline to after the reduction in IOP (post-IOP reduction) were determined by linear regression analysis. RESULTS: All disc parameters improved significantly during IOP reduction and deteriorated significantly during the periods from baseline to the pre-IOP reduction and from baseline to the post-IOP reduction. The degree of reversal in disc parameters was correlated with the deterioration from baseline to the pre-IOP reduction and from baseline to the post-IOP reduction in the vertical cup to disc ratio (r = 0.68, P = 0.0218 and r = 0.97, P < 0.0001, respectively), the horizontal cup to disc ratio (r = 0.57, P = 0.0649 and r = 0.98, P < 0.0001, respectively), the rim area to disc area ratio (r = 0.68, P = 0.0227 and r = 0.98, P < 0.0001, respectively), and the cup volume to disc area ratio (r = 0.67, P = 0.0256 and r = 0.88, P = 0.0004, respectively). CONCLUSION: The degree of deterioration in cupping from baseline before the induction of glaucoma may be an important determinant of the degree of cupping reversal during subsequent reductions in IOP in primate glaucoma.

Animals↗

PubMed1998

Relation between size of optic disc and thickness of retinal nerve fibre layer in normal subjects.

AIMS: To evaluate the relation between the optic disc size and the thickness of the peripapillary retinal nerve fibre layer (RNFL) in normal Japanese subjects by means of scanning laser polarimetry. METHODS: Scanning laser polarimetry was performed in 60 normal subjects. One eye of each subject was randomly selected for study. Using a scanning laser polarimeter, the integral of RNFL thickness was measured totally and regionally within a circular band located 1.75 disc diameters from the centre of the optic disc. The correlation between the optic disc size and the integral of RNFL thickness was examined. RESULTS: The optic disc size showed a significant correlation with the integral of RNFL thickness (R = 0.497, p < 0.001). A significant negative correlation was observed between the optic disc size and the ratio of inferior integral to total integral of RNFL thickness (R = -0.274, p = 0.034). CONCLUSIONS: The cross sectional area occupied by the RNF, measured by scanning laser polarimetry increased significantly with an increase in optic disc size while the ratio of inferior to total cross sectional area decreased significantly. These facts should be considered when one evaluates the RNFL thickness in patients with progressive optic neuropathies such as glaucoma.

Adult↗

PubMed1998

[Influences of trabeculectomy combined with the use of mitomycin C on corneal endothelial cells].

We used a specular microscope to evaluate the corneal endothelial cells in 119 eyes before and 2 to 3 weeks after trabeculectomy with topical mitomycin C. The endothelial cell density per square millimeter averaged 2,569 +/- 487 (mean +/- standard deviation) before surgery and 2,444 +/- 536 after surgery, showing a decrease of 4.98%. The hexagonality decreased by 1.7%, the coefficient of variation increased by 1.9, and the average cell area increased by 6.82%. There were no statistical differences as a whole in these values. Decrease in hexagonality was more frequent in eyes with prior intraocular or glaucoma surgery. Eyes treated by laser trabeculoplasty showed a decrease in endothelial cell density, an increase in coefficient of variation and an increase in hexagonality. Eyes with postoperative flat anterior chamber showed significant changes in each parameter. The findings show that trabeculectomy with topical mitomycin C does not significantly affect the corneal endothelial cells at 2 to 3 weeks after surgery.

Administration, Topical↗

PubMed1998

[Relationship between age and thickness of the retinal nerve fiber layer in normal subjects].

We measured the thickness of retinal never fiber layer (RNFLT) in the peripapillary area in 120 eyes of 60 normal subjects. We used a scanning laser polarimeter, or Never Fiver Analyzer (NFA) by Laser Diagnostic Technologies, USA. Measurements were made along the peripapillary ring with the diameter of 1.75 disc diameter (DD) and another one 0.8 mm away from the disc margin. The RNFLT was not significantly correlated with age along The two rings. The RNFLT ratio of total/nasal area significantly decreased with increase in age. There was an increase in the difference of RNFLT between both eyes with increase in age in spite of considerable interindividual variations. The RNFLT values along both rings thus showed age-related changes in normal subjects.

Adult↗

PubMed1998

[Glaucoma with microcornea; morphometry and differential diagnosis].

To evaluate the characteristics of 10 glaucomatous cases with microcornea, we measured corneal diameter, curvature, axial length, and depth of anterior chamber, and examined the eyes with a specular microscope and an ultrasound biomicroscope. The ten cases examined in this study included 1 case of cornea plana, 2 cases of sclerocornea, 2 cases of nanophthalmos, and 5 cases of anterior microphthalmos. Three of the 10 cases were combined with open angle glaucoma, and the others with closed angle glaucoma. Open-angle glaucoma seemed like developmental glaucoma with angle maldevelopment. The closed angle type may appear at a younger age than in patients who have simple pupilary block. There are probably complex mechanisms related with closed angle glaucoma with microcornea. While differential diagnosis among these cases is relatively easy, we should evaluate how or why the intraocular pressure rises as far as possible before forming a treatment plan for each patient.

Adolescent↗

PubMed1997

Measurement of thickness of retinal nerve fiber layer by scanning laser polarimetry and high-pass resolution perimetry in patients with primary open-angle or normal-tension glaucoma.

PURPOSE: To evaluate the correlation between neural capacity, determined by high-pass resolution perimetry, and thickness of the retinal nerve fiber layer, evaluated by scanning laser polarimetry, in patients with primary open-angle glaucoma or normal-tension glaucoma. METHODS: Thickness of the peripapillary retinal nerve fiber layer was measured by scanning laser polarimetry in 19 eyes of 19 patients with primary open-angle glaucoma and in 23 eyes of 23 patients with normal-tension glaucoma. There were no significant differences between the two groups in mean age, sex ratio, or mean neural capacity. RESULTS: Neural capacity was significantly correlated with thickness of the retinal nerve fiber layer in all 42 eyes (r = 0.31, P = 0.0429). Neural capacity was significantly correlated with thickness of the retinal nerve fiber layer in the eyes of patients with primary open-angle glaucoma (r = 0.60, P = 0.0061), but not in the eyes of patients with normal-tension glaucoma (r = 0.04; P = 0.8522). CONCLUSION: The degree of correlation between neural capacity determined by high-pass resolution perimetry and thickness of the retinal nerve fiber layer measured by scanning laser polarimetry appeared to differ in patients with primary open-angle glaucoma vs those with normal-tension glaucoma.

Female↗

PubMed1997

[Posterior iris bowing after accommodation--elucidation of the etiology of pigment dispersion syndrome].

Recent advancements in imaging the anterior segment structures using the ultrasound biomicro scope (UBM) have proven the involvement of posterior iris bowing due to reverse pupillary block as the cause of pigment dispersion syndrome. In this report, we examined whether the posterior iris bowing occurs even in normal eyes following accommodation, and whether the degree of iris concavity tends to be greater in myopic eyes than in emmetropic eyes. The subjects were normal eyes with sufficient accommodation power, i.e. 5 myopic eyes with less than-5 diopter reflection, 5 emmetropic eyes within +/- 1 dioptor reflection, respectively. We obtained UBM images of the iris at 4 portions before and after accommodation, and measured the degree of posterior iris bowing. We found that almost all data shift posteriorly after accommodation, and that the iris concavity is more distinct in myopic eyes than in emmetropic eyes both before and after accommodation (before: p = 0.0004, after: p < 0.0001). From these results, we confirmed that iris concavity after accommodation occurs in normal eyes but not enough for iridozonular contact, and that pigment dispersion syndrome results from augmented iris concavity owing to pre-existing factors such as iris flexibility, myopia, and sufficient accommodation power.

Accommodation, Ocular↗

PubMed1997

[Parapapillary chorioretinal atrophy and parapapillary avascular area in glaucoma].

We measured the area of parapapillary chorioretinal atrophy (PPA), i.e. zone alpha and zone beta in fluorescein angiography, and parapapillary avascular area (PPAVA) in indocyanine green angiography, using scanning laser ophthalmoscope in a total of 66 eyes of 39 patients. There were 26 eyes of 16 patients with normal tension glaucoma (NTG) and 40 eyes of 23 patients with primary open angle glaucoma (POAG). Although there was no significant correlation between the areas of PPAVA, PPA, zone alpha or zone beta, and mean deviation of Humphrey field analysis, there was significant correlation between all areas except for zone alpha and the spherical equivalent. The areas of PPAVA and zone beta in the NTG group were significantly larger than those in the POAG group (p = 0.04434, 0.02750, respectively). These results suggest that the pathogenesis of disease may be different in NTG and POAG.

Adult↗

PubMed1997

[Plateau iris configuration as a risk factor for malignant glaucoma].

To provide evidence for diagnosing malignant glaucoma, as well as to elucidate the pathogenetic mechanism of the disease, ultrasound biomicroscopy (UBM) is a useful tool. We examined the anterior segments of three patients with post-operative malignant glaucoma with UBM regarding the state before operation, the state of the opposite eye, and the state after the release of the cilio-lenticular block. Case 1 was a 76-year-old female who was diagnosed as having chronic angle-closure glaucoma (CACG) and was treated by trabeculectomy, phacoemulsification, aspiration (PEA), and simultaneous intraocular lens (IOL) implantation. Case 2 was a 22-year-old male diagnosed as having CACG secondary to plateau iris syndrome and was treated by trabeculectomy. Case 3 was a 73-year-old female diagnosed as having normal-tension glaucoma with narrow angle and was treated by PEA and IOL implantation. Slit-like anterior chamber angle and anteriorly positioned ciliary body were observed in all 3 cases, which were identical to those Pavlin reported in 8 cases with plateau iris syndrome. UBM seems to be an important pre-operative examination to evaluate the risk of malignant glaucoma and to consider which surgical procedure and post-operative management is proper. The pre-operative configuration of the ciliary body may be associated with the onset of malignant glaucoma in some patients with CACG or narrow angle.

Adult↗

PubMed1996

Detection of visual dysfunction in optic atrophy by functional magnetic resonance imaging during monocular visual stimulation.

PURPOSE: To evaluate functional magnetic resonance imaging as an objective method for detecting visual dysfunction in various ophthalmologic disorders involving the optic nerve and the chiasm. METHODS: We performed functional magnetic resonance imaging during monocular visual stimulation on seven patients with visual field loss caused by lesions of the optic nerve and the chiasm and on three normal control subjects with no visual field loss. We correlated static threshold perimetry in the seven patients with the results of functional magnetic resonance imaging. RESULTS: In the three normal control subjects, we found good intrasubject similarity in areas of bilateral occipital lobe activation between monocular stimulation of the right and left eyes. In the patients with unilateral optic neuropathy, including glaucoma, stimulation of the affected eye induced no activation of the primary visual cortex in the portion corresponding to the central visual field defects and reduced activity of the associated visual cortex. In the patients with chiasmal compression, monocular stimulation resulted in a marked asymmetry of activation in the primary visual cortex, which corresponded to the visual field abnormality. CONCLUSIONS: Functional magnetic resonance imaging appears to be useful in confirming the clinical diagnosis of optic atrophy because it can objectively disclose visual field loss, even a small defect such as central scotoma.

Adult↗

PubMed1996

[Slow axonal transport in primate experimental glaucoma].

Axonal transport abnormality has been reported to be deeply related to glaucomatous optic nerve injury. These reports mainly investigate the axonal transport blockage using the model of acute elevation of intraocular pressure in normal primates. We studied such axonal transport abnormality especially of slow flow in laser-induced glaucomatous monkey eyes by tissue autoradiography. Abnormal silver grain accumulation suggesting axonal transport damage was seen in the areas of distorted lamina cribrosa in glaucomatous eyes. Accumulation of grains was also seen in the retro-laminar optic nerve in some areas. Normal control eyes showed almost homogenous grain distribution in the pre-lamina, lamina and post-lamina areas. Areas of slightly elevated, accumulation of grains were seen around the lamina cribrosa and disc margin suggesting physiological blockage of axonal transport.

Animals↗