The Retino-Hypothalamic Ultrastructural Changes in Traumatic Optic Neuropathy

Abstract

Aim: To study the retino-hypothalamic ultrastructural changes in traumatic optic neuropathy’s pathogenesis and treatment. Methods: Four groups of mature rabbits were included in this experiment, 30 in each group, 120 in total. The traumatic crush to the optic nerves was reproduced by surgical clips to 90 mature rabbits. The first group (I) included intact/control animals, the second (II) included animals with traumatic optic neuropathy and two other traumatized groups (III and IV) who were given two different doses of treatment. The animals in group III were given infusions of Methylprednisolone 30mg/kg/day for three days. The group IV animals received infusion of 15mg/kg/ day of Methylprednisolone for 3 days in combination with phosphine electric stimulation (PES), starting from the third until the 13th day of the experiment. The electrical pulse which was used on the affected side of the animal was 800 mА and 300 mА on the opposite side. The morphological analysis of the retina and suprachiasmatic nucleus of the hypothalamus of all the four groups of animals included electron microscopy of the semi-thin and ultrathin sections. This analysis was performed a month following the initial injury while the animals were removed from the experiment. The levels of cortisol and adrenocorticotropic hormone (ACTH) in the blood of all experimental animals was tested up to one month following the injury to the optic nerves. Results: We found that trauma to the orbital part of the optic nerve causes collocative necrosis of ganglion cells and swelling of the nerve fiber layer of the ipsilateral retina. In addition, such traumatic damage causes structural changes in the suprachiasmatic nucleus of the hypothalamus. Combined treatment of methylprednisolone with phosphine electro stimulation in traumatized rabbits reduced the thickness of the retina, reduced the cytokaryometric indices and the regeneration processes of bipolar and ganglion cells of the retina. Histopathologically we found an increased number of neurosecretory granules in the suprachiasmatic nucleus of the hypothalamus. ACTH levels in the blood of the group III rabbits were found to be lower, while the cortisol levels higher, and these hormone levels in the IV group rabbits were quite similar to those of the group which was not treated. Conclusion: The combined treatment of traumatic optic neuropathy in rabbits with phosphine electrostimulation and methylprednisolone can be considered a useful treatment, having a beneficial neuroprotective effect.