Changes of retinal functions following the induction of ocular hypertension in rats using argon laser photocoagulation.
BACKGROUND
Electroretinography (ERG) provides a longitudinal monitoring of pathological changes in retina. Scotopic threshold response (STR) of ERG was shown to reflect inner retinal activity and is particularly useful in the evaluation of inner retinal changes in ocular hypertension models. Recently, STR was demonstrated to be attenuated after the induction of ocular hypertension using injection of hypertonic saline into episcleral veins which indicates an impairment of retinal function. However, little is known on the changes of retinal function in an ocular hypertension model induced by laser photocoagulation at episcleral veins and limbal veins.


METHODS
Ocular hypertension was induced unilaterally using laser photocoagulation at episcleral veins and limbal veins in adult Sprague-Dawley rats. Intraocular pressure was monitored and the number of retinal ganglion cell loss was counted across the 8-week experimental period. The animals were dark adapted overnight and flash ERGs were measured before the laser treatment, 5 and 8 weeks after treatment. The changes of STR, scotopic negative response, a-wave and b-wave were analysed.


RESULTS
Approximately 1.6-fold elevation of intraocular pressure was induced in the experimental eyes and 3% retinal ganglion cell loss per week was found. The amplitude of STR was significantly attenuated which indicates an impairment of inner retinal activities. There was also a reduction of scotopic negative response, a-wave and b-wave after the induction of ocular hypertension.


CONCLUSIONS
The laser-induced ocular hypertension model in the present study produced a substantial reduction of retinal functions. Understanding the characteristic of pathological changes is crucial for further study using this model.
Li
Rachel S
RS
Department of Anatomy, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong, China.
Tay
David K
DK
Chan
Henry H L
HH
So
Kwok-Fai
KF
D000818:Animals; D002452:Cell Count; D003623:Dark Adaptation; D004195:Disease Models, Animal; D005260:Female; D007429:Intraocular Pressure; D017075:Laser Coagulation / Q000009:adverse effects; D009798:Ocular Hypertension / Q000209:etiology / Q000503:physiopathology*; D010775:Photic Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000503:physiopathology*; D012165:Retinal Ganglion Cells / Q000473:pathology