Xiaoyun Fang

Transretinal Electrical Stimulation with a Suprachoroidal Multichannel Electrode in Rabbit Eyes

PurposeSeveral approaches for placing an electrode device for visual prosthesis have been previously proposed. In this study, we investigated if transretinal stimulation from the suprachoroidal space can elicit an electrical evoked potential (EEP) in albino rabbits.MethodsA flat electrode array (polyimide plate, platinum electrode) was developed and used for this study. After performing a scleral incision at 2–2.5 mm from the limbus and placing an anchoring suture, the array was inserted into the suprachoroidal space in the posterior portion of the eye by direct observation under a microscope. A platinum wire was implanted into the vitreous space as a reference electrode. For electrical stimulation, a biphasic pulse was used. When the electrode was stimulated, the EEP was recorded.ResultsWhen the electrical stimulation from the suprachoroidal space was applied, the EEP could be recorded with an epidural electrode, and the threshold was 66.0 ± 32.1μA (42.0μC/cm2). Histological examination indicated the absence of major damage to the retina and choroid from the insertion and placement of the array and the electrical stimulation.ConclusionsTransretinal electrical stimulation from the suprachoroidal space could elicit EEP, suggesting that this approach may be useful for a retinal prosthesis system.

Efficacy and safety of one intravitreal injection of bevacizumab in diabetic macular oedema.

Purpose:  To assess the efficacy, duration of effect and safety of one intravitreal injection of bevacizumab in diabetic macular oedema (DMO).

Electrical stimulation with a needle-type electrode inserted into the optic nerve in rabbit eyes.

PurposeTo investigate whether electrical stimulation of the optic nerve can elicit an electrical evoked potential (EEP) in rabbits and to determine whether such stimulation is a useful approach for the placement of a visual prosthesis.MethodsTwo needle-type electrodes were inserted into the optic nerve using a transvitreal approach. For electrical stimulation, monophasic and biphasic pulses were used. By stimulating the optic nerve, the EEP was elicited. After evaluation of the EEP, a histological study was carried out.ResultsWhen electrical stimulation was applied, the EEP could be recorded. The threshold with monophasic and biphasic stimulation was 10 ± 0 µA and 20 ± 8.2 µA, respectively. Histological examination revealed no major complications, such as bleeding or degeneration, which might have resulted from the insertion of electrodes or the electrical stimulation.ConclusionsElectrical stimulation of the optic nerve can elicit an EEP, suggesting that this approach may be useful for a visual prosthesis system. Jpn J Ophthalmol 2004;48:552–557

Efficacy and safety of one intravitreal injection of bevacizumab in diabetic macular oedema – authors’ reply

Editor, W e thank Dr Kumar et al. (2009) for their interest in our report, ‘Efficacy and safety of one intravitreal injection of bevacizumab in diabetic macular oedema’ (Fang et al. 2008). We reanalysed our data from our cases of diabetic macular oedema with a serous macular detachment and have some additional information about our patients. Eleven (29%) of 38 cases of diabetic macular oedema reported in our article had a serous macular detachment. The mean height of the serous macular detachment decreased significantly at 3 months after an intravitreal injection of bevacizumab compared to before the injection (197 ± 106 and 76 ± 94 lm, respectively; p = 0.002). The mean central retinal thickness also decreased significantly at 3 months compared to before the injection (578 ± 205 and 394± 175 lm, respectively; p =0.047). However, in four cases (36%), the height of the serous macular detachment still exceeded 150 lm; in six cases (55%), the central retinal thickness still exceeded 300 lm at 3 months. There was no significant difference in the best-corrected visual acuity before the injection and 3 months after the injection. We found that visual acuity improved more than two lines 3 months after the injection of bevacizumab in only four cases (36%). An intravitreal injection of bevacizumab seems to be effective in reducing serous macular detachments in some patients but is ineffective in increasing visual acuity. However, this study had a small number of cases, including patients who had undergone vitrectomy or been treated with panretinal photocoagulation. Therefore, we should evaluate more cases as well as cases with a longer follow-up to determine the efficacy of an intravitreal injection of bevacizumab for this condition.