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A Obana

Publications and source records attributed to A Obana.

32 records · Page 2Linked to original sources
PubMed1993

[Quantification of indocyanine-green enhancement of diode laser photocoagulation].

The enhancement by indocyanine-green (ICG) of diode laser photocoagulation was quantified. Since ICG concentration in blood increases and decreases rapidly after a single injection, it is difficult to quantify the exact enhancing effect of ICG. A steady-state plasma concentration (about 30 micrograms/ml) of ICG was achieved by injection of 2.5 mg/kg of ICG followed by continuous injection of 0.45 micrograms/kg/min of ICG. The threshold energy values to obtain grayish white retinal burn or choriocapillary occlusion were evaluated at this steady concentration of ICG, and compared with the values in the absence of ICG. The use of ICG decreased the energy values 7% for retinal burn and 8% for choriocapillary occlusion. Although the total dosage of ICG during the continuous injection was high, the enhancement of retinal burn and choriocapillary occlusion was small.

Animals↗
PubMed1992

[Indocyanine green enhanced photocoagulation in the pigmented rabbit].

We performed histological studies of rabbit eyes after intravenous administration of indocyanine green (ICG) and fundus endophotocoagulation with diode laser at the wavelength of 810 nm. As continuation of our previous experiments in albino rabbits, we used 10 eyes of 5 pigmented rabbits which more simulate human eyes. We created weak photocoagulation spots 5 to 30 seconds after intravenous ICG, 4 mg/kg. Each photocoagulation lasted 0.2 sec and its irradiation power was averaged 170 mW. One hour after photocoagulation, there were no changes in the inner retinal layers. In the choroid, we observed occlusion of the choriocapillaris, destruction or loss of endothelial cells of large choroidal vessels, and stromal edema. One month after photocoagulation, large choroidal vessels had disappeared. Whole choroidal layers were replaced by fibrous scar tissue. The findings seemed to indicate that ICG enhanced photocoagulation effect can be observed in eyes with pigmented retinal pigment epithelium and that irreversible choroidal damages can be induced throughout the whole thickness of the choroid. The observed choroidal damages were less in intensity than those in albino rabbits.

Animals↗
PubMed1991

Dye laser photocoagulation through experimentally induced retinal hemorrhage.

The histological effects of photocoagulation obtained by using each of 4 wavelengths of the dye laser (577, 590, 610, and 630 nm) on experimentally induced retinal hemorrhage in cat eyes were examined. Energy from 577, 590, and 610 nm laser was directly absorbed by red blood cells in the retinal hemorrhage and destroyed the inner layers of the retina. Red blood cells were not directly coagulated with the use of 630 nm laser, and the retinal pigment epithelial cells (RPE cells) and choroidal melanocytes were coagulated. These results suggest that the use of yellow or orange dye lasers for photocoagulative therapy in a retinal hemorrhage is dangerous, because of the risk for destruction of the inner layers of the retina. A 630 nm dye laser is useful for photocoagulation of a retinal hemorrhage, while the laser energy is unable to reach the RPE cells and the choroid with the use of other wavelengths.

Animals↗
PubMed1991

Effects of indocyanine green dye enhanced diode laser photocoagulation in non-pigmented rabbit eyes.

Dye enhanced photocoagulation using indocyanine green (ICG) and diode laser has recently been introduced for occlusion of the choroidal neovascular tissue of age-related maculopathy. However, the effects of photocoagulation generated only by dye enhancement have not yet been studied. To discover the threshold amount of ICG for the minimum effect of photocoagulation, various photocoagulation parameters were tried in the fundus of albino rabbit. That is to say, ICG dosage laser power and exposure time were varied at the range of 0.5 mg to 14.0 mg/Kg, 80 to 500 mW and 0.2 or 1.0 sec, respectively. Histopathologic evaluation revealed that the effect of the enhanced photocoagulation was more marked in the choroid than in the retina, and was particularly noticeable in the large vessels in the deep layer of the choroid, even in lower threshold lesions. In clinical application, we should take into consideration the excessive reaction in the choroid.

Animals↗
PubMed1989

Possibility of choriocapillary occlusion under experimental subretinal hemorrhage by photocoagulation with lasers of different wavelengths.

To clarify the possibility of occluding choroidal neovascularization in subretinal hemorrhage with various laser wavelengths, lesions of experimental subretinal hemorrhage were photocoagulated with argon, dye, and krypton lasers and were examined by light and electron microscopy. Our experimental results revealed that laser photocoagulation with wavelengths longer than 590 nm was effective in occluding the choriocapillaries under a thin subretinal hemorrhage. Complete occlusion of choriocapillaries was accomplished by red dye laser (630 nm) or krypton red laser. The choroidal lesion coagulated by 590 nm dye laser showed more extensive reaction than the other lesions at a posttreatment interval of 7 days. The red dye laser (630 nm) or krypton red laser is recommended for the treatment of neovascular maculopathy under thin subretinal hemorrhage because of less reaction and complete occlusion of the choroidal neovascularization.

Animals↗
PubMed1989

[The effect of melanin and hemoglobin on the dye laser photocoagulation in pigmented and albino rabbits].

Photocoagulation was performed in pigmented and albino rabbits using four different wave-lengths of the dye laser (577 nm, 590 nm, 610 nm and 630 nm), and each photocoagulated lesion was examined histologically. The 577 nm dye laser produced chorioretinal coagulation in albino rabbits, which was almost the same as that in pigmented rabbits. This result confirmed that the 577 nm dye laser was well absorbed by hemoglobin in the choriocapillaris, and could produce the sufficient coagulation even if there was no melanin pigment. The 590 nm dye laser produced chorioretinal coagulation in albino rabbits, but it was weaker than that in pigmented rabbits. It was considered that this was because the absorption by hemoglobin of the 590 nm dye laser was less than that of the 577 nm dye laser. The 610 and 630 nm dye laser could not yield appropriate coagulation in albino rabbits under the same conditions as in the 577 nm dye laser. More intense coagulation, that is longer duration and higher power, was required to make chorioretinal coagulation in albino rabbits using the 610 and 630 nm dye laser. In photocoagulation of normal fundus, melanin is the main substance of laser absorption, but in various disorders lacking melanin, the differences of the hemoglobin absorption rate becomes important.

Animals↗
PubMedDate not supplied

Accumulation of photosensitizer ATX-S10 (Na) in experimental corneal neovascularization.

PURPOSE: To determine the most appropriate time for laser irradiation to produce selective occlusion of new corneal vessels by photodynamic therapy (PDT) with a new photosensitizer, ATX-S10(Na). METHODS: The time course of the plasma levels of ATX-S10(Na) and the degree of dye accumulation in the corneal neovascularization after intravenous administration was determined in rabbit eyes. Plasma concentration of ATX-S10(Na) was analyzed by a spectrophotometer. The amount of ATX-S10(Na) in the new corneal vessels was measured by nitrogen-pulsed laser spectrofluorometry. Frozen sections of neovascularized cornea and iris were observed by fluorescence microscopy. RESULTS: Plasma ATX-S10(Na) concentration was highest 5 minutes after dye injection and rapidly decreased and reached almost zero at 24 hours, indicating its prompt excretion from the body. The amount of ATX-S10(Na) in the new corneal vessels as measured by nitrogen-pulsed laser spectrofluorometry increased and reached maximal level at 2 to 4 hours. Under fluorescence microscopy, the dye was more abundantly localized in the wall of new corneal vessels than in the normal tissue at 2 to 4 hours. CONCLUSION: These results indicate that laser irradiation between 2 and 4 hours after dye injection is appropriate for selective PDT with ATX-S10(Na) for the occlusion of new corneal vessels.

Animals↗
PubMedDate not supplied

A retrospective pilot study of indocyanine green enhanced diode laser photocoagulation for subfoveal choroidal neovascularization associated with age-related macular degeneration.

PURPOSE: The effectiveness and limitations of indocyanine green (ICG) enhanced diode laser photocoagulation in treating subfoveal choroidal neovascularization (CNV) associated with age-related macular degeneration (AMD) were investigated retrospectively. METHODS: Thirty-eight eyes of 37 patients with subfoveal CNV received ICG enhanced diode laser (wavelength, 805 nm) photocoagulation in our preliminary series. Nineteen eyes had classic CNV and the others had occult CNV, which was well-delineated on ICG angiography. The rate of anatomical success and functional outcomes were investigated. Factors prognostic of a final visual acuity of 0.1 or better were analyzed. The follow-up period ranged from 6 to 51 months (mean +/- SD = 26.5 +/- 14.4 months). RESULTS: Occlusion of CNV was achieved in 35 of 38 eyes (92%), and 7 eyes (18%) showed recurrence, which was occluded by retreatment in all but 1 eye. Ten eyes (26.3%) showed improvement of visual acuity; 16 (42.1%) showed no change; and in 12 eyes (31.6%) visual acuity deteriorated. Factors prognostic of a final visual acuity of 0.1 or better were good preoperative visual acuity (Mann-Whitney U-test, P =.0028), and a relatively short distance between the edge of laser burns and the center of the foveal avascular zone (unpaired t-test, P =.0285). CONCLUSION: Indocyanine green enhanced photocoagulation achieved a higher anatomical success rate but functional outcomes equal to those with argon or krypton laser photocoagulation. A controlled prospective study is necessary to prove the efficacy of this treatment.

Aged↗
PubMedDate not supplied

A case of glaucoma with choroidal hemangioma managed by nonpenetrating trabeculectomy.

BACKGROUND: Nonpenetrating trabeculectomy was used in a patient with glaucoma complicated by diffuse choroidal hemangioma. CASE: A 12-year-old boy suffered from glaucoma with choroidal hemangioma in the left eye. Intraocular pressure was 28 mm Hg and visual acuity was 0.04. Nonpenetrating trabeculectomy was then performed. OBSERVATIONS: Postoperative intraocular pressure was controlled at around 15 mm Hg with pilocarpine hydrochloride eye drops. Visual acuity and visual field were preserved over 19 months after the operation. CONCLUSIONS: An increase in aqueous outflow resistance was considered to be the major mechanism in the rise in intraocular pressure, based on distinct dilatation and tortuosity of the episcleral blood vessels and congestion of Schlemm's canal. Therefore, construction of aqueous drainage by nonpenetrating trabeculectomy was effective. Retaining the trabecular meshwork was also considered effective in controlling complications such as choroidal hemorrhage and postoperative flat anterior chamber.

Angiography↗
PubMedDate not supplied

Treatment parameters for the efficacy of transscleral cyclophotocoagulation in rabbits using a diode laser.

PURPOSE: To determine parameters for the efficacy of transscleral cyclophotocoagulation (TSCPC) using a diode laser. METHODS: We performed TSCPC on 74 pigmented rabbits with different exposure powers and varying number of applications, followed by clinical observation and histological examination up to 24 weeks. RESULTS: Based on observation of the clinical course, the most favorable parameters were 600 mW and 36 or 48 applications, which did not cause severe complications and sufficiently lowered intraocular pressure (IOP). Histological examination revealed coagulation of the epitheliums and stroma of the ciliary body at 600 mW. The stroma of the ciliary body was severely damaged at 900 mW. CONCLUSIONS: Transscleral cyclophotocoagulation at 600 mW with a larger number of applications than previously reported did not cause severe complications and effected greater and more lasting lowering of IOP than TSCPC with more intense coagulation and fewer applications.

Animals↗
PubMedDate not supplied

Computer assisted image analysis using the subtraction method in indocyanine green angiography.

The choroidal vessels are three dimensionally distributed and very complex in their patterns. They often appear to be overlaid in indocyanine green (ICG) angiograms so it is harder to analyze ICG angiography than fluorescein angiography. When an earlier frame is subtracted from a later frame in a sequence of angiograms, the fluorescence which has increased during the time between the two frames can theoretically be demonstrated. We applied computer-assisted image subtraction methods in selected clinical cases of directly acquired digital ICG angiography to demonstrate how this method works. We used software already installed in an IMAGEnet computer system (Topcon) for image subtraction. We applied the subtraction technique in 18 cases with various diseases. When two images with a time difference of several seconds were subtracted, filling of the choriocapillaris, the neovascularization or the pathological vessels could be observed. When the images had a time difference of several minutes, intrachoroidal dye leakage could be seen more clearly. This method is very helpful for analyzing pathological changes in ICG angiography in clinical cases, when two images are selected appropriately.

Adult↗
PubMedDate not supplied

Photodynamic therapy for corneal neovascularization using topically administered ATX-S10 (Na).

BACKGROUND AND OBJECTIVE: We investigated the effect of photodynamic therapy (PDT) using topically administered ATX-S10(Na) on corneal neovascularization (CoNV). MATERIAL AND METHODS: Rabbit eyes with induced CoNV were treated with ATX-S10(Na) eye drops (10 mg/mL) every 5 minutes, 5 to 25 times. Five to ninety minutes after topical administration, the CoNV were irradiated with a diode laser using a wavelength of 670 nm. RESULTS: The CoNV were occluded fluorescein angiographically in 7 of 16 treated eyes. The eyes having occluded, CoNV were irradiated using fluence of 510-1019 J/cm2 within 20 minutes of eye-drop administration. However, the effect was more variable than what we found using systemic administration in our previous investigation. CONCLUSIONS: Experimental CoNV was occluded by photodynamic therapy using topically administered ATX-S100(Na), suggesting this modality as a possible treatment for CoNV avoids the side effects found with systemic administration of the dye. Further efforts to improve the eye drops in terms of pH and osmotic pressure are needed to achieve increased dye accumulation.

Administration, Topical↗