Intravitreal saline injection ameliorates laser-induced retinal damage in rats.

PURPOSE: Injury to the central nervous system has been shown to trigger a physiologic response in the form of some degree of natural self-repair. This beneficial reaction may be boosted by appropriate preconditioning via a reversible injury to the retina. Here we report the ameliorative effect of intravitreal saline injection on laser-induced retinal damage. METHODS: Standard argon laser lesions (514 and 544 nm, 200 µm, 0.1 W, 0.05 seconds) were induced in the eyes of 36 Dark Agouti pigmented rats and immediately followed by injection of saline either intravitreally (5 µL) or intravenously (0.5 mL). Lesions were evaluated histologically and morphometrically after 3, 20, and 60 days. RESULTS: At all 3 time points, the eyes of rats injected intravitreally showed less laser-induced retinal cell loss (P < 0.05) and smaller lesion diameters (P < 0.05) than those of intravenously injected rats. CONCLUSION: Intravitreal saline injection evidently has a neuroprotective effect on the rat retina. The mechanism of action of this effect should be further elucidated and its clinical applicability tested.

Ameliorative effect of NAP on laser-induced retinal damage.

PURPOSE: NAP is the smallest active element of activity-dependent neuroprotective protein (ADNP) in the non-myelinated neural tissue. This study evaluated the neuroprotective effect of NAP in reducing the spread of laser-induced retinal damage in rat. METHODS: Laser lesions were created in 72 DA pigmented rats. Two groups were treated by one intravenous or intravitreal injection of NAP immediately after exposure to laser. Two control groups were similarly administered saline injection. Histological and morphometrical evaluations of the lesions were preformed 3, 20 and 60 days after photocoagulation. RESULTS: After intravitreal treatment with NAP, a significant reduction in the diameter of the laser-induced lesions was found 3 days after photocoagulation (p < 0.001) but not after 20 and 60 days while the systemic treatment significantly reduced lesion diameter 20 and 60 days after photocoagulation (p = 0.001). Significant difference in photoreceptor cell loss was found in eyes treated intravitreally only 3 days after photocoagulation (p = 0.002). In the systemically treated animals such effect was found only after 20 and 60 days (p < 0.001). CONCLUSIONS: Treatment with NAP ameliorates laser-induced retinal lesions. Intravitreal treatment had an early short-term effect while the effect of systemic administration was delayed and prolonged. This treatment may be of clinical significance in reducing laser-induced retinal injuries in humans.

Development and recovery of laser-induced retinal lesion in rats.

PURPOSE: Laser-induced retinal lesions undergo primary and secondary degeneration followed by a partial reduction of the lesion size. To evaluate treatment effects, detailed data regarding the changes of the lesion over time are essential. The purpose of the study is to describe the histologic changes in an argon laser-induced retinal lesion over a period of 60 days. METHODS: Argon laser lesions were produced in retinas of pigmented rats. The lesions were examined by light microscopy 1 hour and 1, 2, 3, 20, and 60 days after the exposure. RESULTS: The diameter of the lesion increased 24 hours after photocoagulation and then decreased by day 20. Most pyknotic nuclei seen in the outer nuclear layer 1 hour after lasering disappeared 3 days later. Remodeling began 3 days after lasering. By day 60, partial filling in of the empty area with sliding of adjacent nuclei was observed. Recovery was also seen in the other retinal layers. CONCLUSION: The course of a laser-induced retinal lesion is gradual: the photoreceptors are damaged first and the damage then spreads to other layers and to the adjacent retina. By day 3, the damage spreading stops, and adjacent cells begin to fill in and remodel the area of the lesion.

Ameliorative effect of PN-277 on laser-induced retinal damage.

BACKGROUND: The retinal damage induced by laser photocoagulation increases considerably by the secondary degeneration process whereby tissues adjacent to the primary lesion are destroyed. As the neuroprotective effect of immunization by PN-277 was previously demonstrated in models of retina, optic nerve, brain, and spinal cord lesions, it may be used also for reducing retinal damage induced by laser. The aim of this study was to evaluate the neuroprotective effect of immunization with PN-277 in reducing the spread of laser-induced retinal damage. METHODS: Standard argon laser lesions were created in 36 DA pigmented rats. Seven days before exposure to laser, the rats were divided into a test group (n = 18) that was pre-immunized with intraperitoneal injection of PN-277 and control group (n = 18) treated with saline. Histological and morphometrical evaluations of the retinal lesions were preformed 3, 20, and 60 days after the injury. RESULTS: Significant ameliorative effect was demonstrated in the retinas of the pre-immunized animals 60 days after exposure to laser. The diameter of the lesion was 356 microm as compared with 406 microm (P < 0.01), the cell density of the photoreceptor cell bodies measured in the whole lesion was 72.4% of normal as compared with 64.5% (P = 0.01), and at the center of the lesion it was 57.3% of normal as compared with 38.2% (P < 0.01) (treated and control groups, respectively). CONCLUSIONS: Immunization with PN-277 has an ameliorative effect in neural tissue such as the retina. This type of immunization may be of clinical significance in reducing laser-induced retinal injuries in humans.

Functional deficits resulting from laser-induced damage in the rat retina.

BACKGROUND AND OBJECTIVES: To determine the threshold for electrophysiological detection of functional changes after laser photocoagulation in rats, and to correlate the functional damage with retinal morphology. STUDY DESIGN/MATERIALS AND METHODS: Argon-laser lesions, covering a quarter or half of the retina, were produced in the right eyes of 25 rats. Eyes were evaluated by flash electroretinography (ERG) and histologically at 3, 21, and 60 days after lasering. RESULTS: Lasering of half the retina, but not of a quarter, produced a significant decrease in signals at all time points. Some functional recovery was evident 60 days after injury, and was consistent with concurrent morphological healing. CONCLUSIONS: In rats, lasering of half the retina, but not a quarter, leads to significant deficits in outer retinal functions over a 2-month period. Thereafter some recovery occurs, presumably as a result of migration of photoreceptors from undamaged areas and their retinal remodeling.