[In vivo imaging of retinal cell apoptosis following acute light exposure]

Outer nuclear apoptosis following acute light exposure has previously only been shown histologically. This study investigated whether in vivo detection with DARC (detection of apoptosing retinal cells) technology could identify cells undergoing apoptosis.

Acute blue light damage (lambda=405 nm; 3.2 mW/cm(2)) was applied to eyes of dark Agouti rats over 2 h. In vivo retinal imaging using confocal scanning laser ophthalmoscopy was performed before and directly after light exposure as well as after 24 h of dark adaptation. Development of retinal cell apoptosis was then assessed using intravitreal fluorescent-labeled annexin-5 with DARC technology in vivo.

Directly after light exposure, no pathological retinal changes were observed by in vivo imaging. However, retinal flattening and the development of apoptosis within the irradiated retina occurred 1 day later and following dark adaptation. Confocal live scanning through the exposed retina revealed hyperfluorescent apoptotic cells at the level of the outer retina. Histological analysis confirmed the occurrence of photoreceptor cell death and the development of cellular damage at the outer retina.

This study confirms acute light-induced outer nuclear apoptosis using in vivo DARC technology. This may open new and promising ways to assess programmed cell death of the photoreceptor cells, which - until now - was possible only with postmortem analysis.