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Biomedical subjects

J Akiba

Publications and source records attributed to J Akiba.

At least 73 records · Page 4Linked to original sources
PubMed1993

Age-related changes in the molecular properties of vitreous collagen.

To understand the molecular events underlying rheological vitreous changes, age-related changes in the molecular properties of bovine and human vitreous collagen were monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The adult bovine vitreous showed an increase in the high molecular-weight components of the collagen compared with the young samples. In addition, the apparent molecular size of the alpha-chain of the adult type II collagen was slightly larger than that of the young samples. The same tendency also was observed in human vitreous. The increase of high-molecular-weight components of the vitreous collagen could be attributed to intermolecular cross-links of the peptide chains.

Adult↗
PubMed1992

Metal ion catalyzed liquefaction of vitreous by ascorbic acid: role of radicals and radical ions.

The effect of Fe2+ and Cu2+ on the intact calf vitreous in the presence or absence of exogenous ascorbic acid was investigated in vitro. Liquefaction of vitreous gel was evident in the presence of either ion. The loss of gel structure was greater in the presence of exogenous ascorbic acid than in its absence. As shown by high-performance liquid chromatography, liquefaction was accompanied by depolymerization of vitreous hyaluronic acid which is degraded by .OH, generated by the metal ion catalyzed oxidation-reduction system. The involvement of .OH in this process was also evident from the significant reduction in liquefaction in the presence of the .OH-specific scavenger mannitol.

Animals↗
PubMed1992

Fellow eyes in idiopathic macular hole cases.

The fellow eyes in 84 cases of unilateral idiopathic macular hole were studied retrospectively to determine prognoses and risk factors for this disorder. On initial examination, 15 of 84 eyes (18%) had a macular cystic lesion (group 1), 23 (27%) had a yellow spot in the fovea (group 2), and 46 (55%) had a normal macula (group 3). Of the 84 eyes, 58 (69%) had posterior vitreous attachment. During a mean follow up of 39 months, macular hole developed in 8 of 15 eyes (53%) in group 1, and in 6 of 23 eyes (26%) in group 2. However, a macular hole did not develop in eyes with posterior vitreous separation or a normal macula. Although the risk of developing a macular hole may have been overestimated in our study, posterior vitreous attachment and macular abnormalities may be important in predicting macular hole formation in the fellow eyes in idiopathic macular hole cases.

Aged↗
PubMed1992

[Photodynamically induced vitreous liquefaction in vivo].

Photodynamically induced vitreous liquefaction in rabbit eye was investigated. Photosensitizer, riboflavine phosphate, was injected into the vitreous cavity of the rabbit before white-light irradiation. After the irradiation (0, 1, 3, 6 hr) the rabbit vitreous body was separated into gel and liquid portions. The liquid vitreous body was weighed, and the vitreous liquefaction percentage was calculated. One hour irradiation caused 38% of liquefaction of the eye; 3 hr, 50% liquefaction; 6 hr, 59% liquefaction. Although irradiated control eye (without photosensitizer) and the dark adapted control eye (non-irradiated) showed 10-15% liquefaction throughout the experimental period, the liquefaction percentage of the experimental vitreous bodies was significantly larger than that of the control vitreous. Inhibition experiment showed that the radical scavengers (Cu, Zn-superoxide dismutase, catalase, and mannitol) could suppress the photodynamically induced vitreous liquefaction. Results indicated that free radicals, including hydroxyl radical and superoxide anion, which are generated by photosensitizer and visible light irradiation, may contribute to the age-related vitreous liquefaction of humans.

Animals↗
PubMed1991

Vitreous photography with a +90-diopter double aspheric preset lens vs the El Bayadi-Kajiura preset lens.

Two fundus lenses, a 90-diopter preset lens and a 58.6-diopter El Bayadi-Kajiura lens, were compared. The lenses were evaluated with regard to their optics, magnification, field of view, and photographic usefulness in photographing the posterior vitreous. The 90-diopter lens provided a wider field of view but lower magnification. Both lenses permitted high-quality vitreous photographs through the slit lamp, but the 90-diopter lens allowed photographs to be taken through small pupils and some lens opacities.

Aged↗
PubMed1991

Prognostic factors in idiopathic preretinal macular fibrosis.

We retrospectively studied 124 eyes with idiopathic preretinal macular fibrosis to assess the value of fluorescein angiography and vitreous examination for predicting the visual prognosis. During a mean follow-up period of 43 months (range, 12-14 months), the visual acuity of 33 eyes (27%) declined two or more lines from the initial value, although the appearance of the fibrosis remained unchanged in 114 cases (92%). At initial examination, 38 eyes (31%) showed fluorescein leakage into the macula; these eyes were more prone to further visual deterioration than were those without leakage (P less than 0.05). Of 14 eyes with partial vitreous detachment and vitreous traction to the fibrosis, 6 (43%) had a final visual acuity of 20/200 or worse; this proportion was significantly higher than that found either in eyes with no detachment or in those with complete vitreous detachment (P less than 0.05). The presence of fluorescein leakage and/or vitreous traction to the fibrosis may predict worse functional prognosis in eyes with idiopathic preretinal macular fibrosis.

Adult↗
PubMed1991

Comparative study of vitreoretinal relationships using biomicroscopy and ultrasound.

We prospectively studied 29 consecutive eyes with proliferative diabetic retinopathy that showed media clear enough to enable characterization of vitreoretinal relationships by biomicroscopy. Vitreoretinal relationships were also determined by contact B-scan ultrasound. With both techniques, these relationships were documented by photographs and drawings. Biomicroscopy showed complete posterior vitreous detachment (PVD) in 4 eyes (14%), partial PVD in 18 (62%), and no PVD in 7 (24%). Ultrasound examination revealed complete PVD in 4 eyes (14%), partial PVD in 19 (66%), and no PVD in 6 (21%). The results we obtained using ultrasound agreed significantly with those obtained by biomicroscopy [Cohen's kappa = 0.93, 95% confidence interval = (0.80, 1.06)]. Ultrasound detected vitreous changes more easily than biomicroscopy when mild media opacities were present and when the equatorial areas of the globe were examined. Results suggest that ultrasound is adequate to determine vitreoretinal relationships in eyes with clear media and that it is a good alternative to biomicroscopy in eyes with significant media opacities.

Adolescent↗
PubMed1991

[Prognosis of fellow eyes in idiopathic macular hole cases].

We studied contralateral eyes in 62 cases of unilateral idiopathic macular hole to determine their prognoses and risk factors for this disorder. At the initial examination, 11 of 62 eyes (18%) showed a macular cystic lesion, and 18 (29%) showed a yellow spot in the fovea. During a mean follow-up of 39 months, macular holes eventually developed in 6 of the 11 eyes (55%) with macular cystic lesion and in 4 of 18 eyes (22%) with a yellow spot. Macular holes, however, did not develop in eyes with vitreous separation in the fovea or with a normal macula. Moreover, the macular lesion apparently improved in 14 of 29 eyes (48%) with early stage macular holes. These fourteen eyes showed vitreous separation in the fovea at the initial examination or at the follow-up examination. Therefore, eyes with macular cystic lesions and without posterior vitreous separation are at high risk of a macular hole developing, although these eyes have a chance for improvement by spontaneous vitreous separation.

Fluorescein Angiography↗
PubMed1991

Role of the vitreous in posterior segment neovascularization in central retinal vein occlusion.

We retrospectively studied the relationship between the vitreous condition and the development of retinal or optic disc neovascularization in 60 eyes with central retinal vein occlusion associated with extensive retinal ischemia. At initial examination, 24 of 60 eyes (40%) with central retinal vein occlusion had complete posterior vitreous detachment, a prevalence significantly higher than in the fellow eyes. During a mean follow-up period of 43 months, 13 of 34 eyes (38%) without posterior vitreous detachment developed retinal or disc neovascularization, or both, but none of the 24 eyes with complete posterior vitreous detachment developed neovascularization (P less than .001). Our results suggest that central retinal vein occlusion may induce the development of posterior vitreous detachment, and that posterior vitreous detachment may play a role in protecting eyes with central retinal vein occlusion from posterior segment neovascularization.

Adult↗
PubMed1990

Risk of developing a macular hole.

We followed up 45 eyes with early-stage idiopathic macular hole (mean period, 32 months; range, 7 to 87 months) to investigate their prognoses, especially in relation to the vitreous condition. At initial examination, 18 eyes (40%) showed vitreous separation from the fovea, and 10 (22%) developed vitreous separation during follow-up. None of these 28 eyes progressed to a fully developed macular hole during follow-up. Moreover, the macular disease was apparently improved in 23 (82%) of these eyes. However, of the remaining 27 eyes without vitreous separation from the fovea, 10 eyes (37%) progressed to a fully developed macular hole. We speculate that early-stage macular hole could be reversed by spontaneous vitreous separation from the fovea, and this chance may be greater than the risk of true macular hole formation.

Aged↗
PubMed1990

Role of posterior vitreous detachment in idiopathic macular holes.

The role of posterior vitreous detachment in the formation of idiopathic macular hole was evaluated in 310 eyes. The eyes were classified according to the stage of the initial macular pathology: group 1, macular cyst; group 2, early macular hole; and group 3, fully developed macular hole. The initial prevalence of posterior vitreous detachment was 0% (none of 15 eyes) in group 1, 6% (three of 50 eyes) in group 2, and 27% (67 of 245 eyes) in group 3. During the study, all 15 eyes in group 1 and all 43 eyes in group 2 for which data were obtained progressed to fully developed macular holes without the occurrence of posterior vitreous detachment. The findings strongly suggested that most idiopathic macular holes develop in the absence of posterior vitreous detachment and that the pathogenesis of the holes may be independent of the occurrence of posterior vitreous detachment.

Aged↗
PubMed1990

Posterior vitreous detachment and neovascularization in diabetic retinopathy.

The authors evaluated the effect of posterior vitreous detachment (PVD) in 172 eyes (114 patients) with nonproliferative diabetic retinopathy on the development of retinal or optic disc neovascularization. Patients were followed for more than 6 months after the initial vitreous examination (mean, 32 months). None of the patients 39 years of age or younger had PVD, but this condition became more prevalent thereafter with age. In 124 eyes of patients 40 years of age or older, neovascularization developed eventually in 20 (22%) of 93 eyes without PVD but in only 1 (3%) of 29 eyes with complete PVD (P less than 0.05). A vitreous examination was invaluable in predicting the development of retinal or optic disc neovascularization in diabetic patients 40 years of age or older.

Adolescent↗
PubMed1989

Biomicroscopic evaluation and photography of ocular toxoplasmosis.

The vitreous of 39 eyes with ocular toxoplasmosis was studied and photographed using an El Bayadi-Kajiura preset lens. In active cases of toxoplasmosis, the vitreous showed inflammatory opacities and gel shrinkage. In inactive cases, the vitreous was often liquefied. Compared with 39 normal eyes of age- and sex-matched controls, the prevalence of partial posterior vitreous detachment was significantly higher in toxoplasmosis (P less than .001). A higher prevalence of posterior vitreous detachment was found in eyes with the major chorioretinal lesion outside the temporal vascular arcade than in those with lesions inside the temporal vascular arcade (P less than .05). Our results indicated that various vitreous changes may cause posterior vitreous detachment and that location of the inflammatory focus may influence the vitreous condition.

Adolescent↗