High dose methylprednisolone treatment of laser-induced retinal injury exacerbates acute inflammation and long-term scarring

To evaluate therapeutics for attenuating retinal laser injury. Methods. New Zealand Red rabbits (n=76) were pretreated (IV) with either a single dose of hydroxyethyl starch conjugated deferoxamine (HES-DFO, n=29) (6-1 ml/kg, 16.4 mg/ml) or methylprednisolone sodium succinate (MP, n=22) (30 mg/kg, followed by taper of 30, 20, 20, and 10 mg/kg/day for a total of 5d). Controls were untreated (n=25). Fifteen min later, animals were irradiated with a multiline cw argon laser (285mW, 10 msec pulse durations, 16 lesions/eye). Funduscopy, fluorescein angiography, histology, and morphometry were performed at 10 min, 1h, 3h, 24h, 1 mo, and 6 mo after irradiation. Leukocytes were counted at lesion centers for retinal and choroidal compartments at 1., 3, and 24h. Results. At 3h, percent area increase for the lesions was highest for MP (44%) and lowest: for HES-DFO (16%) (p<0.05). In hemorrhagic lesions, MP treatment resulted in the highest increase of retinal neutrophils by 24h (p<0.05), and by 1 and 6 mo extensive chorio-retinal scarring occurred in nonhemorrhagic and hemorrhagic lesions. Also, no benefit was demonstrated on sparing of photoreceptors with MP treatment. Conclusions. Treatment of laser-induced retinal injury with MP exacerbates acute inflammation and long-term chorio-retinal scarring; however, HES-DFO therapy ameliorates these aspects of injury. Data suggest caution in the use of MP therapy for laser injuries.