Abstract
Purpose: :
The current study demonstrated that the subthreshold transpupillary thermotherapy (TTT) laser irradiation on optical never head protects retinal ganglion cells (RGC) in an optic nerve crush (ONC) model.
Methods: :
TTT was performed in right eyes with an 810-nm diode laser aimed at the center of the optic nerve head using the following protocol: power 60 mW, duration 60 seconds, spot size 50µm. Fluorogold was injected into bilateral superior colliculi 5 days before sacrifice and fluorescent gold labeled RGC were counted under fluorescence microscopy.
Results: :
In the ONC group, a progressive loss of RGC was observed; however, in ONC+ TTT group, RGC density was significantly higher (p < 0.05) in each corresponding subgroup compared to the ONC group, which implied the potential neuroprotective role of TTT. This protective effect seemed to be heat shock protein (Hsp) related, because intraperitoneal Quercetin (an inhibitor of Hsp, 4mg/kg/d for 7 days) could completely abolish this protective effect (p < 0.05 for each subgroup). Minimal collateral damage of TTT on optic nerve head tissue, peripapillary RGCs and the myelin sheath of the optic nerve were observed under transmission electron microscopy.
Conclusions: :
These findings suggest the subthreshold TTT is a safe and practical approach to protect RGC. The underlying mechanism may be related TTT-induced Hsp in the RGC.
Keywords: optic nerve • neuroprotection