In the current study, it was aimed to evaluate the changes in myelinated and unmyelinated nerve fibers in
retinal ischemia‑reperfusion
injuries caused by acute
ocular hypertension and to determine the sequence of these changes. Adult healthy New Zealand white rabbits were randomized to the hemodynamic group [n=12; used to determine the optimal intraocular pressure (IOP) for the subsequent experiments] and the
hypertension group (n=6; 70‑mmHg
hypertension induced in one eye). IOP was adjusted using a
cannula and saline. Doppler ultrasound was used to measure the velocity of the optic artery under different intraocular pressures. Immunohistochemistry for
myelin basic protein (MBP) was performed. Apoptosis of
retinal cells was detected by
terminal deoxynucleotidyl transferase biotin‑dUTP nick end labeling (TUNEL) assay. Electron microscopy was used to investigate the changes in myelinated and unmyelinated nerve fibers. IOP of the
hypertension eyes was maintained at 70.2±1.0 mmHg, while IOP of control eyes was 7‑14 mmHg. Doppler ultrasound demonstrated an obvious decline of peak systolic velocity and an increase of resistance index of
retinal bloodstream under a 70‑mmHg IOP. MBP immunohistochemistry and electron microscopy demonstrated obvious
injuries to the myelin fibers. TUNEL indicated a significantly higher apoptosis rate in the
hypertension eyes compared with control eyes. The apoptosis rate of retinal ganglion cells and bipolar cells in unmyelinated regions was higher than in myelinated regions. In conclusion, an IOP of 70 mmHg led to incomplete
retinal ischemia but was the threshold for
retinal ischemia, leading to obvious
injuries to the myelin fibers.