Electroretinography in healthy subjects in relation to systemic glucocorticoid intake

This study examined electroretinographic function in healthy subjects before and after prednisolone intake. To separate the effect of prednisolone on the retina from the potentially confounding hyperglycemia-inducing effect of prednisolone, electroretinography was made while fasting and at a pre-specified level of clamped hyperglycemia. The study included 10 eyes in 10 healthy lean men aged 25 ± 3 years (mean ± SD). The subjects were examined before and after oral intake of prednisolone 37.5 mg/day for 9.1 ± 1.4 days. The diabetogenic potential of prednisolone was reinforced by the intake of a high-caloric diet and by the reduction of physical activity. Full-field electroretinography (ffERG) demonstrated no significant change (P < 0.05) in amplitudes or implicit times in relation to prednisolone intake, neither at fasting glycemia levels, which were 4.9 ± 0.2 mM before and 5.0 ± 0.3 mM (P = 0.467) after the intervention, nor at 10 mM clamped hyperglycemia. Specifically, the fasting b-wave amplitude of the combined rod-cone response was 432 ± 84 mV before and 463 ± 71 mV (P = 0.13) after prednisolone intake. Furthermore, the ffERG could not be shown to be influenced by the doubling of glycemia from fasting to clamped hyperglycemia, neither before, nor after prednisolone (P > 0.05). The stability of ffERG performance in the face of shifting glycemia levels, which differs from what has been found in diabetes, was not influenced by the mild diabetogenic effect of the intervention on insulin resistance (P = 0.011) and post-prandial glycemia (P = 0.023). We conclude that prednisolone had no detectable effect on the ffERG in healthy lean men in this study. Retinal function may be less sensitive to changes in glycemia in healthy subjects than in people with diabetes, a characteristic that was unchanged by a short course of prednisolone.