Steroid and Nonsteroidal Treatment Following Macular Laser May Increase the Laser Lesion Size at the Level of the Retinal Pigmented Epithelium (RPE)

Abstract

Abstract: : Objective: To determine whether postoperative systemic methylprednisolone or indomethacin reduces retinal laser lesion size in an animal model. Methods: Twenty rhesus monkeys (macaca mulatta) received a grid of Argon green laser lesions in the macula of the right eye (240 mw, 0.01 sec, 200 microns). The animals were randomized to one of four treatment groups: Group A high dose methylprednisolone (30 mg/kg/day IV for 3 days followed by IM taper over 2 weeks), Group B moderate dose methylprednisolone (15 mg/kg/day IV for 3 days followed by IM taper over 2 weeks), Group C indomethacin (1.5 mg/kg/day IV for 3 days followed by IM taper for 2 weeks) or Group 4 control (intravenous saline over 3 days followed by IM saline daily for 2 weeks). The animals were treated within one hour of injury. The lesions were assessed using fluorescein angiography at day 1, day 14, 2 months and 4 months. Angiographic images were analyzed in a masked fashion. An image was selected within the first 15 seconds of the study that demonstrated the greatest contrast of the lesion borders, without dye leakage. The area of each lesion was calculated using Scion Image, an image processing software program. Statistical analysis was performed using ANOVA to identify statistically significant differences in the change in lesion size over time. Results: Laser lesions in the high dose steroid treatment group increased in size by 9% comparing day 1 to four months. Lesions sizes at four months in the moderate dose group and indomethacin group remained essentially unchanged at 1% and 2% larger respectively. Lesions in the control group were 8% smaller at four months compared to day one. The difference between the effect in the indomethacin group compared to control as well as the difference between moderate dose steroids compared to indomethacin were statistically significant at p < .05. Conclusion: Based on measurements at the level of the RPE, treatment with systemic methylprednisolone or indomethacin produced no significant reduction in retinal laser lesion size, 4 months after injury. In fact, high dose corticosteroids caused an increase in lesion size. This is consistent with in-vitro studies that have demonstrated that corticosteroids inhibit growth of RPE cells. Despite these findings, high dose corticosteroids may have a beneficial neuroprotective effect on the neural retina following placement of a laser lesion. Ongoing analysis of the histology of the retinal lesions from these animals will evaluate the effect of these treatments on photoreceptors at the lesion borders.

Keywords: laser • retinal pigment epithelium • animal model