Biomedical subjects

Toshiro Sakuma

Publications and source records attributed to Toshiro Sakuma.

7 recordsLinked to original sources

PubMed2006

In vivo and in vitro feasibility studies of intraocular use of seprafilm to close retinal breaks in bovine and rabbit eyes.

PURPOSE: Seprafilm, a sodium hyaluronate/carboxymethylcellulose absorbable barrier developed to prevent adhesions after abdominal surgery, adheres well to wet tissue. The authors studied the efficacy of this film for sealing retinal breaks in animals. METHODS: In an in vitro study, a retinal detachment with a hole was created in bovine eyecups after the vitreous gel was removed. Seprafilm was placed over the retinal hole, and the strength of the retinal adhesion was measured by pulling the film. Permeability was tested by applying methylene blue to the film covering the retinal break. Seprafilm also was soaked in balanced salt solution (BSS) incubated at 37 degrees C, and the pH of the BSS containing Seprafilm was measured as it melted. In an in vivo study, Seprafilm was powdered and mixed in BSS solution, and 0.1 mL was injected into the right vitreous cavity in study rabbits. The same amount of BSS was injected into the right vitreous cavity in control rabbits. Ophthalmologic examinations were performed. Bilateral electroretinograms were recorded simultaneously before and 6 weeks after injection. Both eyes were enucleated for histologic evaluation. RESULTS: Seprafilm adhered well to the retina, was impermeable to methylene blue, and remained solid in BSS for 30 days before it dissolved, and its pH ranged from 7.2 to 8.0. No intraocular inflammatory reaction occurred after intravitreous injection of Seprafilm solution. There was no significant difference in amplitudes or implicit times of electroretinogram a-waves, b-waves, and oscillatory potentials before and after injection and between study and control groups. No significant retinal abnormality was detected by light microscopy in either group. CONCLUSIONS: The film adhered well to the retina with no signs of ocular toxicities. Further study is warranted for possible means of patching retinal breaks.

Animals↗

PubMed2005

Safety of in vivo pharmacologic vitreolysis with recombinant microplasmin in rabbit eyes.

PURPOSE: To investigate the safety of intravitreal microplasmin in rabbits and to confirm previous findings of posterior vitreous detachment (PVD). METHODS: Different doses of microplasmin, from 12.5 microg to 250 microg, in 0.1 mL balanced salt solution (BSS) were injected into the vitreous cavity of rabbit eyes to induce PVD. Fellow eyes were injected with the same volume of BSS. Slit-lamp biomicroscopy, ophthalmoscopic fundus examinations, A- and B-mode ultrasonography, and electroretinography were performed to assess the retina. Electroretinograms (ERGs) were recorded up to 90 days after injection. Morphologic alterations were assessed by light microscopy, scanning electron microscopy (SEM), and transmission (TEM) electron microscopy. RESULTS: A slight aqueous flare and cells were observed in the anterior chamber after microplasmin and BSS injection. A slight inflammatory reaction was also observed transiently in the vitreous cavity. In control eyes, B-mode ultrasonography and SEM examination demonstrated that PVD did not develop after BSS injection. Intravitreal injections of 125 microg or greater of microplasmin induced complete PVD with an internal limiting membrane (ILM) devoid of vitreous collagen fibrils. Eyes injected with 12.5 microg microplasmin had partial PVD, and SEM showed residual fibrils covering the ILM. In all eyes, there was a transient reduction in the a- and b-waves of the ERG on days 2 through 7. The ERGs showed less effect with < 250 microg microplasmin. CONCLUSIONS: Intravitreal injection of recombinant microplasmin in the rabbit induces no ERG or retinal ultrastructural abnormalities. Pharmacologic vitreolysis with this agent may be a useful adjunct to vitreous surgery and could be used to induce PVD without vitreous surgery.

Animals↗

PubMed2003

Penetrating keratoplasty surgery combined with vitrectomy after failing previous corneal surgery.

PURPOSE: The preoperative and postoperative factors influencing visual outcome were analyzed in 15 eyes of 15 patients with graft opacity after keratoplasty associated with vitreoretinal disease who underwent combined surgery of fresh corneal retransplantation and vitrectomy. MATERIALS AND METHODS: The data obtained consisted of diagnosis, preoperative visual acuity, corneal and vitreoretinal findings at the time of surgery, interval between the first visit and surgery, intraocular pressure before surgery, gonioscopic findings, results of bacterial culture of surgical specimens, surgical procedure for vitrectomy, corneal and vitreous findings after surgery, visual acuity 6 months after surgery, intraocular pressure after surgery, and additional surgical techniques. RESULTS: The cause of corneal opacity was graft rejection in all patients, who had been treated with high-dose administrations of steroids and cyclosporin. The preoperative diagnosis was proliferative vitreoretinopathy (PVR) in eight eyes and fungal endophthalmitis in seven eyes. Corneal transparency was achieved in 7 eyes (46.6%) 6 months after surgery. Vitreoretinal findings improved in 9 eyes (60%) and PVR recurred in 6 eyes (40%). Visual acuity improved in 7 eyes (46.6%), did not change in 2 eyes (13.3%), and deteriorated in 6 eyes (40%). The six eyes with decreased visual acuity developed phthisis bulbi. Preoperative intraocular pressure was 2.1 mmHg on average in the phthisis bulbi group, significantly lower than in the group with superior prognosis. Goniosynechia was noted before surgery and did not improve after surgery in all six eyes. CONCLUSIONS: The outcome was poor in eyes with goniosynechia and ocular hypotony, and combined surgery is not indicated for either anatomic or visual preservation in such cases. Care should be taken not to overlook intraocular infection in patients undergoing immunosuppressive therapy against graft rejection. The early detection of retinal detachment is also important in eyes exhibiting hypotony after surgery.

Adult↗

PubMed2003

[Preparation of high-purity and safe autologous plasmin and its clinical application].

PURPOSE: To report an improved preparation of safer and highly-purified autologous plasmin and to demonstrate its clinical applications. METHODS: Prior to clinical application, animal experiments were carried out. In addition, the activity of plasmin in the vitreous cavity after injection was measured serially. In preparation for clinical use, the proteinase inhibitors aprotinin and benzamidine were used for suppression of protein denaturation. The samples were incubated for 48 hours to check for contamination. The preparation was applied to patients with idiopathic macular hole and diabetic macular edema. RESULTS: The plasmin detached the vitreous body from the inner limiting membrane of the retina without any ill effects in animal experiments. The specific activity reached a peak in 5-10 minutes and decreased rapidly thereafter. By adding a suppressor of protein denaturation in the purification process, 0.2 IU (0.1 ml) of high-purity plasmin could be prepared from each patient. No bacterial contamination was noted. Complete vitreous detachment could be induced in two clinical cases. Urokinase was used instead of streptokinase to activate plasminogen. CONCLUSIONS: Vitreous detachment is considered to be induced safely and consistently by injection of plasmin prepared using a protein denaturation suppressor and activated with urokinase. This method is expected to be of clinical value.

Animals↗

PubMedDate not supplied

Multifunction vitreous forceps (maculorrhexis forceps).

We developed novel multifunction vitreous forceps to decrease the frequency of forceps insertion and enable the removal of the internal limiting membrane and other intravitreal membranes for better surgical results. The basic forceps were conventional continuous curvelinear capsulorrhexis (CCC) forceps. The size of the shaft is 23G and its pointed end measures 500 microm in diameter. Additionally, there is a platform in its tip. The pointed end with platform helps to hold the membrane because the outer sheath can be moved while the tip of the forceps is fixed in position, and its pen hold type grip helps to reduce hand movement. The most advantageous thing is that the sharp point enables us to make an initial flap easily and the desired area of internal limiting membrane can be peeled off by firmly holding the platform.

Capsulorhexis↗

PubMedDate not supplied

Efficacy of daunorubicin encapsulated in liposome for the treatment of proliferative vitreoretinopathy.

BACKGROUND AND OBJECTIVE: To investigate the efficacy of daunorubicin encapsulated in liposome as a drug delivery system to treat proliferative vitreoretinopathy (PVR). MATERIALS AND METHODS: An experimental PVR model was made in pigmented rabbits by injecting a suspension of conjunctival fibroblasts and platelet-rich plasma into the vitreous cavity. Daunorubicin was encapsulated in newly developed empty liposome by mixing the empty liposome with the drug solution. Studies were performed 24 hours, 1 week, and 1 month after injection of daunorubicin encapsulated in empty liposome in an experimental PVR model. RESULTS: Compared with the control PVR model, daunorubicin prevented the formation of PVR. Although pathologic changes were observed in the eyes injected with daunorubicin alone, there were no adverse effects observed in the eyes injected with daunorubicin encapsulated in empty liposome. CONCLUSIONS: Daunorubicin encapsulated in empty liposome seems to be effective in preventing PVR without causing any adverse effects to the retina.

Animals↗

PubMedDate not supplied

Retinal vessel changes in a patient with primary systemic nonfamilial amyloidosis.

A case is described that demonstrates retinal vessel changes and suggests the favorable effects of hemodialysis to treat pathology in a patient with primary systemic nonfamilial amyloidosis. A 47-year-old woman diagnosed as having primary systemic nonfamilial amyloidosis at the age of 30 years had linear and dot hemorrhage, venous dilatation, and tortuosity in the right eye. Fluorescein angiography revealed low-density amorphous areas in the walls of dilated veins near the optic disc. These findings diminished with hemodialysis.

Amyloidosis↗