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Occlusion of posterior ciliary artery. IV. Electroretinographic studies.

1972; BMJ; Volume: 56; Issue: 10 Linguagem: Inglês

10.1136/bjo.56.10.765

1468-2079

David McLeod, Sohan Singh Hayreh,

Cerebral Venous Sinus Thrombosis

The effects of posterior ciliary artery (PCA) occlusion have been studied in rhesus monkeys by Hayreh and Baines (I972 a, b, c), who reported the effects of occlusion of the medial PCA, lateral PCA, and all the PCAs on the choroidal circulation (Hayreh and Baines, I972a) and optic nerve head (Hayreh and Baines, I972C), and the productionof chorio- retinal lesions (Hayreh and Baines, 1972b).Their results were obtained from occlusions in 85 monkey eyes.The opportunity arose to study electroretinographic (ERG) changes in ten of these monkeys with unilateral PCA occlusion.Since the PCAs supply the pigment epithelium, visual cells, and outer nuclear layer of the retina posterior to the equator, it might be anticipated that occlusion of these arteries would affect the electrophysiological responses from the retina.This study confirmed this, and as no similar study is available in the literature, our findings are reported below. Materials and methodsIn ten rhesus monkeys, the PCAs on one side were exposed by a lateral orbitotomy and cauterized near their entry into the globe.The extraocular muscles were not divided, and the central retinal artery and vortex veins were left undisturbed.ERGs were recorded at varying intervals after occlusion of the medial PCA (4 monkeys), lateral PCA (4 monkeys), and all PCAs (2 monkeys).The monkeys were anaesthetized with intramuscular Nembutal and the pupils were dilated with cyclopentolate.The ERG was recorded by cotton-wick electrodes in response to a brief flash stimulus of varying intensity from a 'Flash-Tac' stroboscope after I5 minutes' dark adaptation.The ERG of the operated eye was compared with that of the unoperated control eye so that the effects of varying depths of anaesthesia, etc., could be minimized.ERGs were displayed on an oscilloscope and photographed (time-constant of recording system o0s sec.).The ERG changes have been quantitated and correlated with the area of choroid supplied by the occluded PCA and with the chorio-retinal lesions seen in these eyes. Results(I) ELECTRORETINOGRAPHIC STUDIES (a) ERG amplitude A consistent reduction in the amplitude of the ERG was seen after PCA occlusion; the percentage change in the b-wave amplitude is shown in the Table (overleaf).The reduction was least apparent after medial PCA occlusion and most marked after occlusion of all the PCAs; preoperative comparison between the two eyes in these animals showed that the ERG amplitudes were very similar (±5 per cent.).