Maps of the oxygen distribution in the retina of the mouse eye were obtained by phosphorescencelifetime imaging. Phosphor dissolved in the blood was excited by modulated light and phosphorescence imaged through microscope optics with an intensified-CCD camera. Phosphorescence lifetimes and oxygen pressures were calculated for each pixel of the images. The resolution was sufficient to permit the detection of anomalies that result in reduced oxygen pressures in individual retinal capillaries. High-resolution maps of oxygen distribution in the retina can provide greater understanding of the role of oxygen and vascular function in diseases of the eye.

Objectives: The details of the morphological features of choroidal neovascularization (CNV) remain unclear. The purpose of this study was to establish a CNV rat model and study the natural course of CNV using vascular casts and a scanning electron microscope (SEM). Methods: Focal laser photocoagulation (argon green 50 mW, 0.04 s, 200 µm) was applied to Brown Norway pigmented rats. Choroidal vascular casts were prepared 1 and 3 days, 1 and 2 weeks, and 1, 3 and 6 months after laser photocoagulation. The choroidal casts were examined with a SEM. Results: One day after photocoagulation, corrosion casts and SEM revealed complete defects of the choriocapillaris at the laser shot sites. One week after photocoagulation, small vascular buds originating from the damaged choriocapillaris were observed. Two weeks after photocoagulation, newly formed CNV originating from an individual laser burn was observed. One to three months after photocoagulation, these new vessels were connected to each other to form CNV networks. Six months later, some thin and atrophic vessels were observed in the CNV network. Conclusions: We succeeded in making fine corrosion casts of CNV formed by photocoagulation in pigmented rats and in demonstrating the details of CNV formation and regression. It is hoped that the results of this study will contribute to the development of a drug therapy for CNV and to the interpretation of diagnostic imaging of CNV in humans.

The authors obtained satisfactory results in reducing intraocular pressure by the combination of nonpenetrating trabeculectomy, sinusotomy, and trabeculotomy.

Purpose: To determine whether irsogladine inhibits experimental choroidal neovascularization (CNV) induced by laser photocoagulation in pigmented rats. Methods: Focal laser photocoagulation (argon green 50 mW, 0.04 s, 200 µm) was applied to the retinochoroid of normal Brown Norway rats. Oral administration of irsogladine (5 mg/kg/day or 50 mg/kg/day) was started 1 week before and continued for 2 weeks after laser photocoagulation. Choroidal vascular casts were made 2 weeks after laser photocoagulation and were examined with a scanning electron microscope (SEM). CNV formation was classified according to three grades and evaluated. Results: Laser-induced CNV formation was significantly reduced in rats given 5 mg/kg/day (p < 0.01) or 50 mg/kg/day of irsogladine (p < 0.001). Administration of 50 mg/kg/day of irsogladine was more effective in preventing CNV formation than 5 mg/kg/day (p < 0.001). The development of the vascular bud was especially inhibited by 50 mg/kg/day of irsogladine (p < 0.001). CNVs in rats treated with 50 mg/kg/day of irsogladine looked less well developed than those in controls. There was no significant side effect of irsogladine. Conclusions: Irsogladine inhibits the development of experimental CNV induced by photocoagulation in pigmented rats.

The phosphorescence lifetime imaging system previously used to image oxygen in the retina of the cat eye was modified to allow imaging of phosphorescence lifetimes in the much smaller mouse eye. Following the lead of Shonat and coworkers, a frequency domain approach was used in which the excitation light source was modulated in a 50% on: 50% off square wave while the gate of the intensified CCD camera was similarly modulated but delayed with respect to the excitation. These were analyzed by fitting the intensity at each pixel to a sinusoid. The phase of the phosphorescence relative to the excitation was determined and from the phase shift and frequency, the phosphorescence lifetime was calculated. The Stern-Volmer relationship was then used to calculate the oxygen pressure at each pixel of the image array. High resolution maps of phosphorescence lifetime and oxygen pressure in the retina of the mouse eye have been attained. The retinal veins draining into the optic head appear as large, highly phosphorescent vessels against a lower phosphorescence background with a network of smaller vessels. The oxygen pressure in the retinal veins is typically from 20 to 30 mm Hg while the background has somewhat higher oxygen pressures. Experiments are underway to resolve the oxygen in the choroid from that in the retina. The arteries on the retinal surface can be observed, but their small diameter, relatively high oxygen pressures (> 90 mm Hg), and surrounding tissue with much lower oxygen pressures, makes accurate determination of the oxygen pressure a challenge.