Electroretinographic studies in rhegmatogenous retinal detachment before and after reattachment surgery

Changes in the scotopic electroretinogram (ERG) and oscillatory potentials (Ops) were examined in patients who had rhegmatogenous retinal detachment within 3 days before and also at regular intervals after a successful reattachment operation. Electroretinograms were recorded in 38 patients (age 10 to 62 years) for the recent 5 year period. The amplitudes of the scotopic a-wave and b-wave in the detached eye were significantly decreased compared to the fellow normal eye preoperatively. Statistically significant differences were found between the preoperative and the postoperative recordings of the diseased eye. However, postoperative interocular differences in the amplitude of the a-wave between the reattached and normal fellow eye were not statistically significant. The amplitudes of the a-wave and b-wave were inversely related to the extent of the retinal detachment area, the duration of the detachment, and the extent of the buckles that were applied. Significant interocular differences in the b/a wave amplitude ratio and the Ops amplitude were observed. These results strongly suggest that the retinal function, even after successful reattachment surgery, might be compromised mainly by an inner retinal malfunction rather than from a photoreceptor dysfunction.

Partial Optic Nerve Evulsion

Optic nerve evulsion is a devastating, uncommon cause of sudden visual loss following major head trauma. Less frequently, it is associated with pointed non penetrating orbital injuries with minimal ocular trauma. Possible mechanisms of injury include extreme rotation and forward displacement of the globe, penetrating orbital injury causing a backward, pull on the optic nerve, and sudden increase in intraocular pressure causing rupture of the lamina cribrosa. Funduscopic examination may reveal total or partial lack of the optic disc and variable degrees of intraocular hemorrhage. Fluorescein angiographic finding is variable, visually evoked potential often shows the delay in latency or the decrese in amplitude, Computed tomography or magnetic resonance imaging usually demonstrates an intact optic nerve sheath. We report a case of optic nerve evulsion which diagnosed by retinoscopic finding, fluorescein angiography, computed tomography, and clinical history. We present it with a review of the literature.

Aconite induced myelo-optic neuropathy in a rabbit model

Aconite is a common remedy of herb doctors and is widely used in the Far East. Clinical aspects of the visual disturbance produced by this drug have been described, but little is known about its pathology. Tinctura aconiti (0.6 mg of total alkaloid/kg 2x) was administered intraperitoneally in rabbits to evaluate its toxic effects on the visual system. The alteration in the visual evoked potential following aconite injection consisted of a delay in the onset and peak latency. Histopathologically, there were damages to the myelin sheath of the visual pathway, spinal cord and peripheral nerves. These findings suggest that aconite may cause primarily myelo-optic neuropathy.

The Changes of the Visual Evoked Potential for Aconitine Induced Visual Pathway Demyelination in Rabbit Model

Aconitine, a principal constituent of aconite, may cause myelopathy on the visual pathway, spinal cord and peripheral nerve of the rabbits. A single dose of aconitine (O.6mg/kg), was administered intraperitoneally in order to analyze electrophysiological change of the eye in a rabbit model. The changes of the VEP after an aconitine injection consisted of delay in the onset and peak latency, and a reduction in the amplitude of the contralateral a cortical response. The amplitude of YEP was reduced prominently for several days after the aconitine injection and thereafter recovered quickly. However, the onset and peak latency were significantly delayed until 8 weeks after the aconitine injection. The analysis of YEP afttords us an excellent opportunity to access the precise structural correlates of the functional changes associated with demyelination within the central nervous system in rabbits.