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PurposeBlind individuals who have photoreceptor loss are known to perceive phosphenes with electrical stimulation of their remaining retinal ganglion cells. We proposed that implantable lateral geniculate body (LGB) stimulus electrode arrays could be used to generate phosphene vision. We attempted to refine the basic reference of the electrical evoked potentials (EEPs) elicited by microelectrical stimulations of the optic nerve, optic tract and LGB of a domestic pig, and then compared it to visual evoked potentials (VEPs) elicited by short-flash stimuli.MethodsFor visual function measurement, VEPs in response to short-flash stimuli on the left eye of the domestic pig were assessed over the visual cortex at position Oz with the reference electrode at Fz. After anesthesia, linearly configured platinum wire electrodes were inserted into the optic nerve, optic track and LGB. To determine the optimal stimulus current, EEPs were recorded repeatedly with controlling the pulse and power. The threshold of current and charge density to elicit EEPs at 0.3 ms pulse duration was about ±10 µA.ResultsOur experimental results showed that visual cortex activity can be effectively evoked by stimulation of the optic nerve, optic tract and LGB using penetrating electrodes. The latency of P1 was more shortened as the electrical stimulation was closer to LGB. The EEPs of two-channel in the visual cortex demonstrated a similar pattern with stimulation of different spots of the stimulating electrodes. We found that the LGB-stimulated EEP pattern was very similar to the simultaneously generated VEP on the control side, although implicit time deferred.ConclusionsEEPs and VEPs derived from visual-system stimulation were compared. The LGB-stimulated EEP wave demonstrated a similar pattern to the VEP waveform except implicit time, indicating prosthetic-based electrical stimulation of the LGB could be utilized for the blind to perceive vision of phosphenes.

PurposeTo evaluate the effectiveness of silicone oil tamponade in patients with chronic serous retinal detachment (SRD) persisting for three months after the resolution of ocular inflammation.MethodsA total of 17 eyes of 17 patients diagnosed with chronic SRD persisting for three months after the resolution of ocular inflammation and with high risk of phthisis bulbi by secondary ocular hypotony and macular detachment by subretinal fibrous membrane formation were subjected to surgical intervention. Subjects underwent silicone oil tamponade after surgical drainage of subretinal fluid. Retrospective analyses on anatomical and functional success rates were then performed.ResultsAnatomical success with retinal reattachment was observed in ten of the 17 eyes (58.82%), while functional success measured as difference in the best-corrected visual acuity before and after the surgery were logarithm of the minimum angle of resolution (logMAR) 1.95 ± 0.66 and logMAR 1.51 ± 0.66, respectively (p < 0.05).ConclusionsThis study suggests that, in patients with chronic SRD despite prolonged medical treatment and resolution of inflammation, surgical drainage of subretinal fluid with silicone oil tamponade can achieve anatomical and functional success.