Search PubMed⌕ Search

Biomedical subjects

M Shirakashi

Publications and source records attributed to M Shirakashi.

34 records · Page 2Linked to original sources
PubMed1993

Intraocular pressure-dependent progression of visual field loss in advanced primary open-angle glaucoma: a 15-year follow-up.

We studied the relationship between intraocular pressure (IOP) and progression of visual filed loss in 83 eyes of 83 patients with advanced primary open-angle glaucoma (loss of at least one quarter of the visual field on Goldmann perimetry). During the 15-year follow-up study, 71 eyes (86%) showed progression of visual field loss. The mean IOP was significantly lower in eyes that remained stable (13.4 +/- 1.3 mm Hg) than in those that showed progression of visual field loss (19.4 +/- 2.6 mm Hg). These results suggest that it is necessary to reduce IOP to below 15 mm Hg to prevent further progression of visual filed loss in advanced glaucoma.

Adult↗
PubMed1993

[Fluorescein angiographic findings regarding the optic disc in cases of low-tension glaucoma and the chronic stage of anterior ischemic optic neuropathy].

The optic disc was studied by stereofluorescein angiography in 7 cases of the chronic stage of anterior ischemic optic neuropathy (AION) and 20 cases of low-tension glaucoma (LTG), to clarify the difference in vasculature. In the LTG patients, a selective and well-defined decrease of laminar and prelaminar capillaries in the upper and (or) lower temporal area of the optic disc was found in 38 (95%) of 40 eyes in the 20 cases. In the AION patients, a decrease of laminar and prelaminar capillaries was also found in 3 (43%) of 7 eyes in the 7 unilateral cases, but the specific area and form of vascular reduction were not found. These results show that the angiographic picture of the optic disc in LTG is clearly different from that in AION.

Adult↗
PubMed1992

Extracellular matrix changes of the optic nerve lamina cribrosa in monkey eyes with experimentally chronic glaucoma.

Using light microscopic immunohistochemistry, we studied the immunolocalization and immunoreactivity of the extracellular matrix, including collagen types III, IV, VI, laminin, and alpha elastin in the lamina cribrosa of monkey eyes with normal and experimentally chronic glaucoma. Our results showed: (1) abnormal linearlike immunodeposits of both collagen type IV and laminin in the margin of the lamina cribrosa with significant density in the glaucomatous eyes; (2) the immunoreactivity of collagen type III resembled that of the normal eye, but was slightly stronger at the laminar surface; (3) findings with collagen type VI resembled those of type III with an enhanced linearlike staining surrounding the nerve-fiber bundles. Furthermore, staining of alpha elastin demonstrated dramatic changes in both reactivity and localization. The lamina cribrosa of glaucomatous eyes showed a markedly reduced immunoreactivity as well as an irregular, interrupted pattern. These observations suggest that the changes might be a secondary to the long-standing elevation of intraocular pressure. The alteration of these macromolecules may modify the course of glaucomatous optic damage.

Animals↗
PubMed1992

Changes in reversal of cupping in experimental glaucoma. Longitudinal study.

BACKGROUND: The authors prospectively and longitudinally studied changes in optic disc topography during spontaneous reduction of intraocular pressure (IOP) in five monkeys with experimental glaucoma, using a computerized image analyzing system (Topcon IMAGEnet). METHODS: Glaucomatous optic neuropathy was produced in one eye of each animal by repeated argon laser photocoagulation of the trabecular meshwork. The duration of follow-up was 12 months. After laser treatment, IOP fluctuated and tended to increase. Spontaneous reduction in IOP was frequently observed during follow-up. Changes in optic disc parameters (vertical and horizontal cup-to-disc ratios, rim area/disc area, cup volume/disc area) that accompanied a given magnitude of spontaneous reduction in IOP at the early stage of glaucoma (first 4 months of follow-up) were compared with those at the later stage of glaucoma (last 4 months of follow-up). RESULTS: All optic disc parameters improved significantly during IOP reduction at each stage of glaucoma. Although there was no significant difference between the two stages in the magnitude of IOP reduction, the extent of improvement in each disc parameter was significantly less in the later stage than in the early stage. In both stages, reversal of cupping occurred symmetrically in the vertical and horizontal dimensions. Expansion of the cup occurred symmetrically in the early stage, but this was predominantly vertical in the later stage. CONCLUSION: These results suggest that the extent of cupping reversal after IOP reduction may decrease with progressive glaucomatous damage in primate glaucoma.

Animals↗
PubMed1991

Prevalence of migraine in low-tension glaucoma and primary open-angle glaucoma in Japanese.

We studied the prevalence of migraine in low-tension glaucoma (LTG) and primary open-angle glaucoma (POAG). Seventy seven Japanese patients with LTG, 73 with POAG, and 75 normal subjects were randomly selected and tested with a headache questionnaire. The prevalence of headache with or without typical migrainous features (unilateral headache or ocular pain, nausea, vomiting, and visual disturbance before headache) was 51% in LTG, 42% in POAG, and 44% in normal patients. The prevalence of headache with two migrainous features or more (probable migraine) was 17% in LTG, 11% in POAG, and 12% in normal subjects. The prevalence of headache with three migrainous features (classical migraine) was 5% in LTG, 3% in POAG, and 3% in normal subjects. There was no statistically significant difference in the prevalence of any types of migraine between the three groups of patients (p greater than 0.05). These results suggest there is no significant relationship between migraine and LTG or POAG in Japanese patients.

Adult↗
PubMed1991

Reversal of cupping in experimental glaucoma.

We studied the change in the optic disk topography during spontaneous pressure reduction in laser-induced primate glaucoma (7 eyes, follow-up of 20 weeks) using computerized image analysis (vertical and horizontal cup-to-disk ratios CDR(V), CDR(H); neuroretinal rim area/disk area; cup volume/disk area). A significant correlation was found between the percent pressure reduction and the percent reversal in each disk parameter. There was no significant difference in the percent reversal between CDR(V) and CDR(H). These results suggest that reversal of cupping may depend on the percent pressure reduction, and may occur symmetrically in primate glaucoma.

Animals↗
PubMed1990

Long-term efficacy of low power argon laser trabeculoplasty.

We studied the long-term efficacy of argon laser trabeculoplasty, applying low-power (a mean of 450 mW), a duration of 0.1 second, and a small number of burns (a mean total energy of 1.85 J) over 90 to 120 degrees of the trabecular meshwork. Fifty-four eyes with poorly controlled open-angle glaucoma were treated. The mean follow-up was 46 months. The mean intraocular pressure decrease was 5.3 mmHg in 35 eyes at one year, 6.1 mmHg in 23 eyes at 3 years, 5.1 mmHg in 13 eyes at 5 years, and 5.4 mmHg in 5 eyes at 6 years. Life-table analysis showed that the probability of success was 58% at one year, 49% at 3 years, and 46% at 5 years. Both the incidence and magnitude of the intraocular pressure rise in the early post-laser period were minimal and no serious complications were observed.

Aged↗
PubMed1990

The effects of intraocular pressure elevation on optic nerve axonal transport in the monkey.

Blockage of axonal transport by intraocular pressure (IOP) elevation was studied quantitatively in monkey eyes, using liquid scintillation counting. After 5 h of IOP elevation (perfusion pressure of 30 mmHg), axonally transported protein was measured in the distal third of each optic nerve, which was divided into superotemporal, inferotemporal, superonasal, and inferonasal portions. The ratio of the amount of radioactive protein in each portion of the optic nerve to that in the whole optic nerve was calculated. In eyes with IOP elevation, the mean ratio for the temporal optic nerve was significantly lower than that for the nasal optic nerve. It appeared that axonal transport was not affected homogenously throughout the optic nerve but was more impaired by the temporal half of the optic nerve following IOP elevation.

Analysis of Variance↗
PubMed1990

Visual disturbance in patients with melanocytoma of the optic disk.

Visual disturbance in 11 patients with melanocytoma of the optic disk was analyzed. Goldmann visual field examination showed enlargement of Mariotte's blind spot in 7 of 10 patients (70%) and visual field defect or depression in 7 patients (70%). In 6 of the 7 patients with visual field defect of depression (86%), the portion of visual field damage corresponded with the location of the tumor and retinal nerve fiber bundle defect. In 1 patient, sudden loss of visual acuity occurred, presumably due to anterior ischemic optic neuropathy induced by melanocytoma.

Adult↗
PubMed1990

[Axonal transport blockage by acute intraocular pressure elevation in monkeys].

The distribution of orthograde rapid axonal transport blockage in the optic nerve head by acute intraocular pressure (IOP) elevation in monkeys was studied by autoradiography. Tritiated leucine was injected intravenously two hours before IOP elevation, and the IOP was elevated for five hours, maintaining a perfusion pressure of 30mmHg. Serial step cross sections from the optic nerve head at the level of the lamina cribrosa were prepared for light microscopic autoradiography, and the accumulation and distribution of grains were quantitatively analyzed using computerized image analysis. The area of focal grain accumulation was expressed as a percent of the defined optic nerve area and each eight sectors, divided by axially intersecting vertical, horizontal, and diagonal lines, respectively. In eyes with IOP elevation, the mean area of focal accumulation of grains in the temporal half of the optic nerve was significantly larger, compared with the nasal half. Within axonal bundles, the focal high accumulation of grains was frequently identified to be in association with trabecular beams of connective tissue in the peripheral portion of the axonal bundle. These results suggest temporal dominant blockage of axonal transport in the optic nerve head, which may be induced by mechanical compression of the axonal bundles during IOP elevation.

Animals↗
PubMed1989

Argon laser trabeculoplasty for chronic angle-closure glaucoma uncontrolled by iridotomy.

Nineteen eyes of 19 Japanese patients with medically uncontrollable chronic angle-closure glaucoma following laser iridotomy or surgical iridectomy underwent argon laser trabeculoplasty (ALT), applying low-power and a small number of laser burns over a small extent of the trabecular meshwork. All the eyes had glaucomatous optic disc damage, visual field loss, and intraocular pressure elevation before ALT. In each case, the extent of peripheral anterior synechiae was equal or less than 50% of the angle. The mean follow-up was 35 months. Life-table analysis (Kaplan-Meier method) showed that the probability of success was 66% at the end of three years after ALT. It is concluded that in the cases of uncontrollable chronic angle-closure glaucoma following laser iridotomy or surgical iridectomy, ALT should be tried before filtration surgery.

Female↗
PubMed1989

[Optic disc measurements with computerized image analysis in experimental chronic glaucoma].

We quantitatively analyzed morphological changes of the optic disc of ten Japanese monkey eyes exposed to sustained intraocular pressure (IOP) elevation by repeated argon laser application to the trabecular meshwork. Using a computerized image analyzer (Topcon IMAGEnet), we measure the cup-disc ratio (CDR), disc area (DA), cup volume/disc area (CV/DA), and rim area/disc area (RA/DA). The duration of IOP elevation was 48.4 +/- 0.8 (mean +/- SD) weeks, and the mean IOP during the experiment was 26.3 +/- 2.6 mmHg [the mean IOP during the experiment/pre-treatment IOP was 2.05 +/- 0.55 (IOP ratio)]. In advanced glaucomatous eyes (the duration of IOP elevation of approximately one year), comparing pretreatment, the CV/DA increased 4.96 times, the vertical CDR increased 1.78 times, the horizontal CDR increased 1.69 times, the DA increased 1.42 times, and the RA/DA decreased 0.54 times. A significant positive correlation was found between the IOP ratio and, both the vertical CDR (gamma = 0.65) and the CV/DA (gamma = 0.68). These results suggested that the development of glaucomatous optic disc cupping correlated with the degree of IOP elevation in monkey eyes. Using this computer image analyser, the longitudinal quantitative follow-up of disc changes of experimental glaucoma may be useful for understanding the mode of human glaucomatous optic nerve damage.

Animals↗
PubMedDate not supplied

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

PURPOSE: To determine it there are any age-dependent changes in the thickness of the retinal nerve fiber layer (RNFL) in the peripapillary area. METHODS: Sixty normal volunteers (31 men, 29 women) (120 eyes) whose ages ranged from 23-75 years (mean 48.4 years) participated in this study. The thickness of the RNFL was determined using a scanning laser polarimeter along the peripapillary area with a 1.75 disc diameter and along another ring 0.8 mm away from the disc margin. RESULTS: The thickness of the RNFL was not significantly correlated with age in either of the two ring areas. However, the RNFL thickness ratio of total/nasal area decreased significantly with increase in age in both rings. There was an increase in the difference of RNFL thickness between the right and left eyes of the same individual with aging, in both rings. CONCLUSIONS: It was suggested that the RNFL thickness determined along both rings demonstrated almost identically the relationship between age and RNFL thickness in normal subjects.

Adult↗