Norihiko Yanagiya

Posterior vitreous detachment induced by injection of plasmin and sulfur hexafluoride in the rabbit vitreous.

PURPOSE To investigate whether an injection of plasmin and sulfur hexafluoride (SF6) can induce posterior vitreous detachment (PVD) without vitrectomy. METHODS One eye each of 15 New Zealand white rabbits was assigned to one of three groups. Eyes in group 1 received a vitreous injection of 1 unit of human plasmin (0.1 mL reconstituted in balanced salt solution) and 0.5 mL of SF6; eyes in group 2 received a vitreous injection of plasmin alone; eyes in group 3 received a vitreous injection of SF6 alone. Seven days after injection, all animals were monitored electroretinographically and killed, and the eyes were enucleated. After fixation, scanning electron microscopy was performed. RESULTS In group 1 eyes, the retinal surface was smooth except for the vitreous base, which showed complete separation of the vitreous cortex from the retina, indicating PVD. In group 2 and 3 eyes, sparse collagen fibers remained on the retinal surface. CONCLUSION Vitreous injection of plasmin combined with SF6 can induce PVD without vitrectomy.

Imaging of Epiretinal Membranes in Macular Holes by Scanning Laser Ophthalmoscopy

PURPOSE Because recognition and removal of an epiretinal membrane are important in macular hole surgery, we used the scanning laser ophthalmoscope preoperatively to study epiretinal membranes in patients with idiopathic macular holes. METHODS We studied 67 eyes (60 consecutive patients) with idiopathic macular holes. We evaluated the thickness and the extent of the epiretinal membrane by using a scanning laser ophthalmoscope. We then compared the fundus images obtained with the scanning laser ophthalmoscope with red-free monochromatic fundus photographs. RESULTS Confocal imaging of the fundus with either argon blue (488 nm) or argon green (514 nm) laser illumination clearly showed the epiretinal membranes. In all eyes, we observed lesions ranging from a patchy glinting light reflex to a dense epiretinal membrane. A well-demarcated dense epiretinal membrane around the macular hole was observed in seven (44%) of 16 eyes with stage 2 macular holes and in 12 (40%) of 30 eyes with stage 3 holes, but in only two (10%) of 21 eyes with stage 4 holes. The prevalence of the dense epiretinal membrane in stage 2 or 3 holes was significantly higher than in stage 4 holes (P = .025 and .024, respectively). CONCLUSIONS Fundus imaging using the scanning laser ophthalmoscope with argon laser illumination is useful preoperatively to evaluate epiretinal membranes in eyes with idiopathic macular holes.

Effects of peroxynitrite on rabbit cornea

Abstract Background: Nitric oxide (NO) reacts rapidly with the superoxide anion to generate peroxynitrite, which has been found in the aqueous humor in eyes with uveitis. We evaluated the functional and anatomic effects of peroxynitrite on rabbit cornea. Methods: One eye of each rabbit received an anterior chamber injection of 3-morpholino-sydonimine N-ethylcarbamide (SIN-1), which simultaneously generates both NO and the superoxide anion. The corneal thickness was measured using an ultrasonic pachymeter before and after the injection. The eyes were fixed and the corneal specimens were prepared for electron microscopy. Results: Anterior chamber injections of SIN-1 caused a significant increase in the corneal thickness (25.1±3.0 µm) 30 min after injection. Transmission electron microscopy showed swollen mitochondria and large vacuoles in the cytoplasm, and scanning electron microscopy revealed obscuring of the mosaic pattern by increased ruffling of endothelial cell surface and borders. Conclusion: The results suggest that peroxynitrite generated in the aqueous humor may cause corneal endothelial cell damage, which leads to transient corneal edema.

Three-Dimensional Analysis of Macular Diseases With a Scanning Retinal Thickness Analyzer and a Confocal Scanning Laser Ophthalmoscope

OBJECTIVE To compare three-dimensional analysis of macular diseases obtained using the scanning retinal thickness analyzer (RTA) with that obtained using the confocal scanning laser ophthalmoscope, Heidelberg Retina Tomograph (HRT). PATIENTS AND METHODS Both the RTA and the HRT were used to examine 50 eyes of 36 patients with diabetic macular edema, macular edema following branch retinal vein occlusion, age-related macular degeneration, and idiopathic macular holes. RESULTS In most macular diseases, the retinal thickness map constructed using the RTA agreed with the image obtained with the HRT. The two maps were not consistent with each other, however, in patients with dense retinal hemorrhages and with extrafoveal fixation. CONCLUSIONS Although both the RTA and the HRT give additional information to clinically evaluate macular diseases, they do have limitations. The discrepancy between these two analyses in some specific macular pathologies might be caused by the different wavelengths of the laser beam and the different methodologies used to scan the retina.

Copper-Ion-Catalyzed Vitreous Liquefaction in vivo

To investigate copper-ion (Cu2+)-catalyzed vitreous liquefaction in vivo, Cu2+ solution (10 mumol) was injected into the vitreous cavity of rabbits. At 24 h after the injection, the gel and liquid vitreous were weighed, and the percent of vitreous liquefaction was calculated. Cu2+ injection resulted in liquefaction of 58% of the vitreous, although control eyes had 12% liquefaction (p < 0.1). The vitreous liquefaction was more pronounced in the presence of exogenous ascorbic acid. However, the addition of mannitol, a hydroxyl-radical-specific scavenger, significantly suppressed the Cu(2+)-catalyzed vitreous liquefaction. The free radicals generated by the Cu(2+)-catalyzed oxidation system may cause vitreous liquefaction in vivo.

Three-dimensional characteristics of macular pseudoholes using confocal laser tomography.

BACKGROUND Epiretinal membranes with macular pseudoholes are sometimes confused with full-thickness macular holes. Because both the natural course and clinical management of the two differ, an accurate differential diagnosis is needed. PATIENTS AND METHODS We obtained three-dimensional images of macular pseudoholes in 12 eyes using the Heidelberg retina tomograph (HRT). Another 15 eyes with a full-thickness macular hole were also studied. In addition, we measured the area and the maximum depth of both types of holes. RESULTS Irregular rippling undulations were frequently observed on the three-dimensional topographic maps around the pseudoholes, whereas elevated cuffs were observed around the full-thickness holes. The maximum depth of the macular pseudoholes (mean, 57 microm) was significantly shallower than that of the full-thickness macular holes (mean, 156 microm; P < 0.01). CONCLUSION Three-dimensional images obtained by the HRT and the measurement of the maximum depth may be useful in differentiating macular pseudoholes from full-thickness macular holes.

Sensitivity of Chorioretinal Atrophic Lesions in High Myopia Detected by Scanning Laser Ophthalmoscope Microperimetry

The purpose of this study was to investigate the sensitivity of chorioretinal atrophic lesions in high myopia. Twelve eyes from 11 highly myopic patients with well-circumscribed chorioretinal atrophy (CRA) were examined. Static perimetry was performed using scanning laser ophthalmoscope (SLO) microperimetry under the following conditions: background, 10cd/m2; spot size, Goldmann III; stimulation time, 100ms; intensity, 0 dB. Two types of SLO angiography were performed, fluorescein angiography and indocyanine green angiography. SLO microperimetry revealed absolute scotomas in the central CRA lesion in all patients. However, the stimulus was perceived in 6/12 (50%) at the CRA margin. There were no differences in SLO angiography in eyes with or without sensitive areas at the CRA margin. In addition, a case was observed in which absolute scotomatous areas enlarged outward and sensitive areas diminished during a 1.5-year follow-up period. Our findings indicate that retinal function was unimpaired in some peripheral CRA lesions. The inner retinal destruction may occur after the CRA develops, and the functional retinal damage may enlarge outward with time in the CRA lesion.