Tempol protects against intravitreous indocyanine green-induced retinal damage in rats

Purpose

Indocyanine green (ICG) has been widely used as a vital dye for macular surgery. However, ICG can be toxic to retinal cells. Here we evaluate whether tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl), a free radical scavenger, can protect against ICG-induced retinal damage in rats.

Methods

Brown Norway rats received intravitreal injections of ICG 0.5?% or BSS as controls. Tempol (20?mg/kg BW) or PBS as a control was administered intraperitoneally 24?h and 30?min before ICG and once daily for 7 consecutive days. Tempol was detected in the retina using electron paramagnetic resonance (EPR) spectroscopy. One?week after ICG injections, the effects of tempol on retinal toxicity were assessed by retinal ganglion cell (RGC) back-labeling and by light microscopy. Electroretinography (ERG) was performed after 1 and 2?weeks.

Results

ICG administration reduced RGC numbers by 17?% (1,943?±?45 vs. 2,342 ± 31 RGCs/mm²). Tempol treatment rescued RGCs in a significant manner (2,258?±?36, p?<?0.01) and diminished morphological changes detected by light microscopy. ICG-injected eyes showed a significant reduction of ERG potentials only in PBS-treated animals (V_max 530?±?145?μV vs. 779?±?179?μV, p?=?0.0052), but not in the tempol-treated group.

Conclusions

Tempol significantly attenuates ICG-induced toxicity in rat retinas and may therefore be considered for further evaluation as accompanying treatment in ICG-assisted chromovitrectomy.