In vivo biocompatibility of a new cyanine dye for ILM peeling.

PURPOSE: To investigate the biocompatibility of the new cyanine dye: 3,3'-Di-(4-sulfobutyl)-1,1,1',1'-tetramethyl-di-1H-benz[e]indocarbocyanine (DSS) as a vital dye for intraocular application in an in vivo rat model and to evaluate the effects of this dye on retinal structure and function. METHODS: DSS at a concentration of 0.5% was applied via intravitreal injections to adult Brown Norway rats with BSS serving as a control. Retinal toxicity was assessed 7 days later by means of retinal ganglion cell (RGC) counts, light microscopy, optical coherence tomography (OCT), and electroretinography (ERG). RESULTS: No significant decrease in RGC numbers was observed. No structural changes of the central retina were observed either in vivo (OCT) or under light microscopy. ERGs detected a temporary reduction of retinal function 7 days after injection; this was no longer evident 14 days after injection. CONCLUSIONS: DSS showed good biocompatibility in a well-established experimental in vivo setting and may be usable for intraocular surgery as an alternative to other cyanine dyes. In contrast to indocyanine green, it additionally offers fluorescence in the visual spectrum. Further studies with other animal models are needed before translation into clinical application.

[Pathophysiology of cataract formation after vitrectomy]. / Pathophysiologie der Katarakt-Entwicklung nach Vitrektomie.

Cataract formation is one of the most common complications after vitrectomy and cataract extraction in such cases will have to be performed under more difficult conditions. A knowledge of the different types of cataract, their frequency and causes may help to develop strategies to prevent this complication. In addition to a progressive nuclear opacification, which may occur after any type of vitrectomy, transient feathering of the lens often occurs after intraocular gas tamponade, while permanent subcapsular opacification may occur in silicone oil-filled eyes. Nuclear opacification after vitrectomy morphologically and histologically resembles age-related cataracts, but shows a faster progression: two years after vitrectomy half of the eyes require cataract extraction and there seems to be an age limit: the opacification progresses faster in patients over 50 years old. The main cause for nuclear cataracts most probably is oxidative stress. Oxygen in the avascular lens is provided by diffusion, meaning that the surrounding oxygen content is crucial for the oxygen content within the lens and thus for the formation of reactive oxygen species. In rabbits and also in humans the partial oxygen pressure is highly elevated in the vitreous cavity after vitrectomy and posterior to the lens since the vitreous is lacking as a diffusion barrier for the oxygen. The partial oxygen pressure might be additionally elevated by ventilation with oxygen and a high oxygen pressure in the infusion fluid during surgery. This elevated partial oxygen pressure may lead to increased oxygen stress and thus to lens opacification by oxidation of structural proteins. The key for the prevention of cataract formation therefore seems to be avoidance of oxidative stress, factors that might increase the protective or repair systems are so far not available. Ventilation with oxygen should be minimised as should be the partial oxygen tension in the infusion fluid. New hydrogels as vitreous substitutes might have a beneficial influence on intraocular partial oxygen tension.

Extraocular surgery for implantation of an active subretinal visual prosthesis with external connections: feasibility and outcome in seven patients.

BACKGROUND: Due to low energy levels in microphotodiode-based subretinal visual prostheses, an external power supply is mandatory. We report on the surgical feasibility and the functional outcome of the extraocular part of an approach to connect a subretinal prosthesis to an extracorporeal connector in the retro-auricular space via a trans-scleral, transchoroidal cable. METHODS: Seven volunteers with retinitis pigmentosa received an active subretinal implant; energy was supplied by gold wires on a trans-sclerally, transchoroidally implanted polyimide foil leading to the lateral orbital rim where it was fixated and connected to a silicone cable. The cable was implanted subperiostally beneath the temporal muscle using a trocar to the retro-auricular space where it penetrated the skin for connection to a stimulator. To avoid subretinal movement of the implant, three tension relief points have been introduced. RESULTS: All implantations were performed as planned without complications, and no serious adverse events occurred in the postoperative period. Fixation of the implants was stable throughout the entire study duration of 4 weeks; permanent skin penetration proved to be uncomplicated. Motility was minimally restricted in downgaze and ab-/adduction. Explantation was uneventful. CONCLUSION: The above-described procedure provides a method for stable fixation of a subretinal device with a trans-scleral, transchoroidal cable connection to an extracorporeal connector.

Sensitivity and specificity of ELISA and immunoblot for diagnosing neurocysticercosis.

In patients with neurocysticercosis (NCC), clinical manifestations and the results of neuroimaging procedures vary widely and often do not facilitate a definite diagnosis. In order to determine the value of immunodiagnosis for NCC, 222 serum and cerebrospinal fluid samples from patients with NCC and healthy subjects were examined. The samples represented patients from various endemic regions, those with other neurological disorders from an endemic area (Mexico), persons with various helminth infections other than NCC, and a group of healthy volunteers. All specimens were tested by enzyme-linked immunosorbent assay and immunoblot for the presence of Taenia solium-specific antibodies. The sensitivities of the enzyme-linked immunosorbent assay and the immunoblot test in NCC patients were almost identical (80% and 81.7%, respectively). For both tests, the sensitivity was higher when cerebrospinal fluid (86%) was tested compared with serum (75%). The overall specificity of enzyme-linked immunosorbent assay was only 75.3% because of frequent false-positive results in patients with other helminth infections, especially in those with echinococcosis. The specificity (99.4%) of the immunoblot test was clearly superior. It is concluded that enzyme-linked immunosorbent assay as a screening method and immunoblot as a confirmatory test contribute considerably to the diagnosis of NCC.