Quantification of the neurodegenerative impact on the visual system following sudden retrobulbar expanding lesions - an experimental model.

INTRODUCTION: Afferent disorders of the visual system are a potential consequence following orbital trauma. The aim of this study was to investigate the tolerance of neurons in the retinal ganglion cell layer to acute expanding retrobulbar lesions.
MATERIAL AND METHODS: In 42 male albino rats, intraorbital haemorrhage was simulated by transconjunctival insertion of a retrobulbar micro-balloon (filling volume 0.2-0.5 ml, duration of lesion 60 or 90 min). Neurodegeneration in the retinal ganglion cell layer was investigated by measuring the mean total neuron number and the mean neuron size.
RESULTS: Increased retrobulbar volumes of 0.3 ml for 60 min led to a decrease in a number of neurons by 14.5% and in size of the neurons by 1.7%. Prolongation of the trauma to 90 min resulted in a decrease in number of neurons by 48.3% and in reduction of size of neurons by 22.1%. In contrast, a retrobulbar filling volume of 0.5 ml for 60 min resulted in a decrease in number of neurons by 11.4% and in size of neurons by 6.7%.
CONCLUSION: The duration of a retrobulbar lesion leading to subsequent retinal ischaemia seems to be more important for neuron survival than the exerted pressure (once it is greater than a critical point for producing retinal ischaemia). The results strengthen the need for emergency treatment in cases of retrobulbar haemorrhage. Copyright 2002 European Association for Cranio-Maxillofacial Surgery. Published by Elsevier Science Ltd.