High intraocular pressure-induced ischemia and reperfusion injury in the optic nerve and retina in rats.
OBJECTIVE
The purpose of this paper is to describe the damage caused to the retina and the axons of the optic nerve by acute ischemia-reperfusion injury and the extent to which optic nerve damage correlates with the duration if ischemia due to high intraocular pressure (IOP).


METHODS
Acute ischemia in the retina and optic disc was induced in albino rats by increasing the IOP to 110 mmHg for a period of 45-120 min. Thereafter, the eyes were reperfused at normal IOP after 7 days. The retina and optic nerve were examined by light and electron microscopy, and morphometrical counts of the optic nerve axons were performed.


RESULTS
After 45 min of ischemia, electron microscopic examination revealed swelling of mitochondria and degeneration of neurotubules on axons in cross sections of the optic nerve. The axonal counts in eyes subjected to 45 min of ischemia were 29% lower than in control eyes. After 60 min of ischemia, there were distinct disruptions of mitochondria and degeneration of the axons. After 90 min of ischemia, numerous axons showed degeneration with disordered myelin sheaths. Neuronal cell death was seen in the retina, mainly in the ganglion cell layer.


CONCLUSIONS
Damage to the retinal ganglion cell layer and the optic nerve was evident after only 45 min of ischemia in normal eyes. This experiment suggests that seriously injured eyes must be protected from high IOP; if IOP elevation is required during vitrectomy, it is essential to reduce the duration of interruption of blood flow to a minimum.
Adachi
M
M
Department of Ophthalmology, Kansai Medical University, Osaka, Japan.
Takahashi
K
K
Nishikawa
M
M
Miki
H
H
Uyama
M
M
D000818:Animals; D001369:Axons / Q000648:ultrastructure; D002452:Cell Count; D016923:Cell Death; D007429:Intraocular Pressure; D007511:Ischemia / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D009457:Neuroglia / Q000648:ultrastructure; D009798:Ocular Hypertension / Q000150:complications; D009898:Optic Disk / Q000098:blood supply / Q000648:ultrastructure; D009900:Optic Nerve / Q000098:blood supply* / Q000648:ultrastructure*; D009901:Optic Nerve Diseases / Q000209:etiology / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000209:etiology / Q000473:pathology* / Q000503:physiopathology; D012160:Retina / Q000648:ultrastructure*; D012162:Retinal Degeneration / Q000209:etiology / Q000473:pathology; D012165:Retinal Ganglion Cells / Q000648:ultrastructure; D012171:Retinal Vessels