Management of submacular hemorrhage with intravitreal versus subretinal injection of recombinant tissue plasminogen activator

To compare the efficacy of pars plana vitrectomy (ppV) with intravitreal injection of recombinant tissue plasminogen activator (rtPA) and gas versus ppV with subretinal injection of rtPA and intravitreal injection of gas

Bound States and Critical Behavior of the Yukawa Potential

We investigate the bound states of the Yukawa potential $V(r)=-\lambda \exp(-\alpha r)/ r$, using different algorithms: solving the Schr\"odinger equation numerically and our Monte Carlo Hamiltonian approach. There is a critical $\alpha=\alpha_C$, above which no bound state exists. We study the relation between $\alpha_C$ and $\lambda$ for various angular momentum quantum number $l$, and find in atomic units, $\alpha_{C}(l)= \lambda [A_{1} \exp(-l/ B_{1})+ A_{2} \exp(-l/ B_{2})]$, with $A_1=1.020(18)$, $B_1=0.443(14)$, $A_2=0.170(17)$, and $B_2=2.490(180)$.Comment: 15 pages, 12 figures, 5 tables. Version to appear in Sciences in China

TRANSCHOROIDAL SUBRETINAL CHIP IMPLANTATION IN BLIND RETINAL PIGMENTOSA PATIENTS. THE CHOROIDAL CHALLENGE

Purpose: Active subretinal visual prostheses require a transchoroidal implantation due to their necessary connection to extraocular parts of the device for energy supply. When starting the program surgically the choroidal access was assumed to be one of the major problems. Material and Methods: 26 legally blind retinal pigmentosa (RP) patients were included in the multicenter study and implanted with a chronic active prosthetic device via a transchoroidal access. 12 out of these 26 patients were operated by one surgeon who developed the transchoroidal procedure and had experience with it. Only this subgroup was analyzed to eliminate the learning curve effects of multiple surgeons. Results: All implantations were carried out successfully in terms of intended position of the implant and stability of the retinal situation. Feared major bleedings were not observed even when accidental perforation of the choroid occurred (1) in the area of the posterior pole. Minor problems concerning surgery were observed when advancing the guide foil or the implant subretinally. The reason were adhesions between retinal pigment epithelium (RPE) and retina. These adhesions seem common in the area of dense pigmentation or scaring in RP patients. Other technical problems during the complex surgical procedure were unintended sub RPE implantation. This occurred twice but could be corrected within the implantation. This pitfall never led to bleedings or other unexpected effects that were harmful for the patient. Conclusion: Problems resulting from the choroid are manageable and seem not to be a limiting factor for this complex surgical procedure. Unintended perforations that occurred did not have a threatening or harmful decisive side effect. One of the reasons may be the rather atrophic choroidal situation in RP. Proper design and geometry of the guide foil and implant are relevant and are under improvement to minimize incidents resulting from this challenge. Thus even difficult retinal situations are no contraindication for chip implantation // Russian Ophthalmological Journal, 2016; 2: 27-32. doi: 10.21516/2072-0076-2016-9-2-27-32

Implantation and testing of subretinal film electrodes in domestic pigs

By definition, an electronic subretinal visual prosthesis requires the implantation of stimulation electrodes in the subretinal space of the eye. Polyimide film electrodes with flat contacts were implanted subretinally and used for electrical stimulation in acute experiments in anaesthetised domestic pigs. In two pigs, the film electrode was inserted through a sclerostomy into the vitreous cavity and, subsequently, via a retinotomy into the subretinal space around the posterior pole (ab interno approach). In three other pigs the sclera and pigment epithelium were opened for combined ab interno and transscleral positioning of the subretinal electrode. In all cases, perfluorocarbon liquid (PFCL) was used to establish a close contact between the film electrode and the outer retina. After cranial preparations of three pigs for epidural recording of visual cortex responses, retinal stimulation was performed in one pig with a film electrode implanted ab interno and in two pigs with film electrodes implanted by the ab interno and transscleral procedure. The five subretinal implantations were carried out successfully and each polyimide film electrode tip was positioned beneath the outer retina of the posterior pole. The retina was attached to the stimulation electrode in all cases. Epidural cortical responses to light and electrical stimulation were recorded in three experiments. Initial cortical responses to Ganzfeld light and to electrical stimuli occurred about 40 and 20 ms, respectively, after stimulation onset. The stimulation threshold was approximately 100 microA and, like the cortical response amplitudes, depended both on the correspondence between retinal stimulation and cortical recording sites and on the number of stimulation electrodes used simultaneously. Our results in a domestic pig model demonstrate that polyimide film electrodes can be implanted subretinally and tested by recording cortical responses to electrical stimulation. These findings suggest that the domestic pig could be an appropriate animal model for basic testing of subretinal implants

la détermination de la loi applicable : les correctifs au rattachement

Revue Droit et PatrimoineInternational audienceno abstrac