Abstract
Purpose: :
To examine the thickness changes of retinal layers in vivo after an intravitreal injection of endothelin-1 in rat eye by optical coherence tomography (OCT).
Methods: :
Endothelin-1 (200 pmol) was injected intravitreally in one eye of Brown-Norway rats (n=5). Contralateral eye which received an intravitreal injection of phosphate buffered saline served as control. Circumpapillary OCT scans with a circle diameter of 500 µm centered on the optic disc were performed as described previously (Nagata A, et al. IOVS 2009) before and 1, 2, and 4 weeks after injections. The thickness of retinal layers was measured using built-in auto-segmentation software. The number of retinal ganglion cells was counted in retinal flatmounts which was prepared at 4 weeks post-injection and immunostained with Thy-1 antibody.
Results: :
The thickness of the inner retinal layer (from retinal nerve fiber layer to inner nuclear layer) decreased significantly at 1 week post-injection and progressed thereafter (baseline, 92.2 ± 2.0 µm; 1 week, 70.4 ± 3.9 µm; 2 weeks, 60.4 ± 5.5 µm; 4 weeks, 54.7 ± 2.1µm; mean ± standard deviation; p<0.05). The thickness of retinal nerve fiver layer increased at 1 week post-injection and then decreased thereafter (baseline, 25.0 ± 1.1 µm; 1 week, 28.4 ± 2.5 µm; 2 weeks, 23.8 ± 1.7 µm; 4 weeks, 18.9 ± 2.0µm; p<0.05). Control eyes did not show significant thickness changes. Retinal nerve fiber layer thickness at 4 weeks post-injection was significantly correlated with the number of retinal ganglion cells in retinal flatmounts (r=0.74, p=0.014).
Conclusions: :
OCT revealed that a decrease in retinal nerve fiber layer thickness due to retinal ganglion cell loss occurs following a decrease in inner retinal layer thickness after an intravitreal injection of endothelin-1 in rat eye.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • nerve fiber layer