Light absorbing properties of indocyanine green (ICG) in solution and after adsorption to the retinal surface — an ex-vivo approach

BACKGROUND: To evaluate potential differences in light absorbing properties and stability of indocyanine green (ICG) adsorbed to the retinal surface and of ICG dissolved in water and balanced salt solution. METHODS: The retina of four human donor eyes was prepared by removing the vitreous from the retinal surface. The inner surface of the specimen was covered with two to three drops of a 0.05% or 0.15% ICG solution respectively. After 1 min, the dye was removed by careful irrigation using BSS plus. The retinal specimens were then investigated by diffuse reflection spectroscopy (UV/VIS/NIR Spectrometer Lambda 900/Perkin Elmer equipped with a PELA-1020 integrating sphere accessory) and their absorption evaluated by the Kubelka-Munk function. To control the sensitivity of the setting, diffuse reflectance spectra of ICG adsorbed to a cellulose membrane and Al(2)O(3) were measured. For comparison, absorption spectra of ICG dissolved in water and BSS plus solution were measured in relation to ICG concentration and time using an UV/VIS/NIR Spectrometer Lambda 900/Perkin Elmer. RESULTS: On the retinal surface, absorption spectra exhibited a steep increase of absorption beginning at 620 nm, with a maximum at 736 nm (0.05%) and a shoulder at 745 (0.15%) and a second maximum at approximately 800 nm for both concentrations. Repeated measurement of the retinal surface 13 days after the ICG exposure revealed no changes in the position of the maxima as compared to the initial measurements. Light absorbing properties of ICG on cellulose or Al(2)O(3) are similar to those seen on the retinal surface with respect to the pattern and location of absorption maxima. In contrast, ICG dissolved in water or BSS plus disclosed variations in absorption characteristics depending on dye concentration, solute and time of measurement. CONCLUSIONS: Absorption characteristics and stability of ICG bound to the retinal surface could be of relevance when investigating potential pathomechanisms of ICG related toxicity, which might be related not only to intraoperative but also to postoperative light exposure of patients after intravitreal use of ICG.     

Blinded, Externally Controlled Multicenter Evaluation of Light Microscopy and PCR for Detection of Microsporidia in Stool Specimens

The quality parameters for the detection of microsporidia in identical sets of 50 stool samples were determined for six laboratories where technicians used light microscopy and for six laboratories where technicians used PCR. The average overall sensitivities were 67% (89% for patient samples only) for the PCR laboratories and 54% (80% for patient samples only) for the light microscopy laboratories. Specificities were 98 and 95%, respectively. Differences in results were most apparent between the individual laboratories rather than between the two major methods used.     

Effect of saline infusion on net reabsorption of endogenous sulfate relative to that of phosphate in intact and thyroparathyroidectomized rats

Clearance experiments have been performed to study the effects of saline infusion on the reabsorption of inorganic sulfate (SO₄) at endogenous levels. Adult female Sprague-Dawley rats on a standard diet were used. Both intact and thyroparathyroidectomized (TPTX) animals were infused with a 130 mmol/l sodium chloride solution at a low (0.15 ml/min) and a high (0.375 ml/min) rate. This increase of the infusion rate decreased the reabsorption of SO₄ in both groups of animals significantly. The fractional excretion of SO₄ in theintact rats increased from 9.9±5.6 to 18.4±3.6% (mean values±SD,p<0.001) and in theTPTX rats from 5.3±2.5 to 22.4±6.3% (p<0.001). It is concluded that endogenous parathyroid hormone has no major effect on the saline-induced inhibition of reabsorption of SO₄.This work was supported by a grant from the Deutsche Forschungsgemeinschaft (Fr 239/9-1)     

Removal of silicone oil with vision improvement after rhegmatogenous retinal detachment following CMV retinitis in patients with AIDS

PURPOSE: To report that silicone oil may be safely removed from immuno-recovered patients with acquired immunodeficiency syndrome (AIDS) after instillation for cytomegalovirus (CMV)-related rhegmatogenous retinal detachment. METHOD: We report two patients with CMV-related retinal detachment who had previously been treated with vitrectomy and silicone oil. RESULTS: Six months after removal of silicone oil, the retina remained attached in both patients. Without specific anti-CMV therapy, there was no relapse of CMV retinitis while patients were undergoing highly active antiretroviral therapy. Best-corrected visual acuity improved in both patients. CONCLUSION: It appears to be possible to remove silicone oil safely from patients with AIDS who show immune recovery, thus avoiding side effects of long-standing silicone oil and increasing quality of life. After silicone oil removal, visual acuity was improved.     

Surgical extraction of subfoveal choroidal new vessels and submacular haemorrhage in age-related macular degeneration: results of a prospective study

· Background: The surgical extraction of subfoveal choroidal new vessels (CNV) is one of several possibilities to treat subfoveal CNV or haemorrhages in age-related macular degeneration (ARMD). · Methods: Prospective study, follow-up 3–6 months. Clinical and angiographic differentiation of three subgroups: (1) subfoveal well-defined CNV (24 eyes); (2) subfoveal ill-defined CNV with or without well-defined components (10 eyes); (3) submacular haemorrhages (20 eyes). · Results: The mean and median visual acuity and the proportion of eyes with ≥20/200 vision increased slightly in group 1 and decreased slightly in group 2; the differences were not significant. Group 3 demonstrated mean improvement but was heterogeneous, depending on the site and type of underlying CNV. The proportion of eyes with 3 or more lines of improvement after 3 months was 35.3% (7/17), 10% (1/10) and 38.9% (7/18) respectively. The proportion of eyes with a loss of 3 or more lines after 3 months was 5.9% (1/17), 20% (2/10) and 5.6% (1/18) respectively. The recurrence rate was 29.2% (7/24), 8.3% (1/11) and 25% (5/20). Intraoperative complications were iatrogenic central tears in 7.3% (4/55), peripheral tears in 14.5% (8/55) and peripheral retinal detachment in 3.6% (2/55). A postoperative retinal detachment was observed in 2 of 55 eyes (3.6%). All these complications could be managed without ill effect. · Conclusion: Subfoveal surgery might perserve remaining retinal function in eyes with well-defined CNV. However, subgroups of the MPS subfoveal laser trials with comparable initial visual acuity demonstrated postoperative functional stabilisation and similar recurrence rates in well-defined CNV. Though selected cases of submacular haemorrhage did profit from surgery, TPA-assisted gas injection will probably be a better alternative. Unfortunately, surgery for ill-defined CNV, found in the vast majority of eyes with exudative ARMD, seems to worsen the natural course. Surgery has to be combined with restoration of Bruch’s membrane before it can become a possible therapeutic option in ARMD. Received: 6 February 1998 Revised version received: 29 April 1998 Accepted: 12 May 1998     

In vivo imaging of the human zonular apparatus with high-resolution ultrasound biomicroscopy

· Background: To investigate the potential of high-resolution ultrasound biomicroscopy (UBM) for studying the zonular apparatus of human beings in vivo. · Methods: Using transducer frequencies of 34 MHz and 50 MHz, criteria were developed to identify transcorneal and transscleral sections that allowed reproducible identification of the different fiber groups of the zonular architecture. For that purpose, 10 volunteers between the ages of 14 and 41 years underwent high-resolution ultrasound biomicroscopy under conditions of consensual far- and near-accommodation. The online video recordings of the respective UBM investigations were afterwards analyzed image by image. Good visibility of zonular fibers was obtained when the ultrasound wave propagation comprised an angle close to 90° with the fiber orientation and when the oscillations of the UBM scan had a strict radial orientation towards the limbus and avoided, simultaneously, the ciliary processes. · Results: In all the volunteers, high-resolution ultrasound biomicroscopy imaged the zonular fiber groups known from histology. In addition, it detected fibers that do not follow the course of the inner ciliary body surface but take a direct route from the ora serrata to the lens. It also demonstrated that fibers that seem to change direction at crossings with other fibers. Under conditions of near-accommodation, the zonular fibers showed signs of relaxation. · Conclusions: High-resolution ultrasound biomicroscopy seems well suited for in vivo investigations of the zonular apparatus and of accommodation in man. The results support the fundamental features of the Helmholtz theory on accommodation. Received: 8 June 1998 Revised version received: 7 September 1998 Accepted: 14 September 1998     

Preoperative infection prophylaxis with 1 % polyvidon-iodine solution based on the example of conjunctival staphylococci

Background: Most germs causing postoperative endophthalmitis derive from the conjunctival bacterial normal flora. Postoperative endophthalmitis is often induced by staphylococcal germs. The application of polyvidone-iodine solution to the conjunctiva is one possibility to reduce potential endophthalmitis-causing bacteria. The aim of this study was to evaluate the effectiveness of 1 % polyvidone-iodine solution concerning the reduction of colonization with staphylococci in the course of intraocular surgery. This is to evaluate the effectiveness of 1 % polyvidone-iodine solution concerning coagulase-negative and positive staphylococci.     

N‐acetylcysteine regimens for paracetamol overdose: Time for a change?

Paracetamol overdose is one of the commonest pharmaceutical poisonings in the world. For nearly four decades, intravenous acetylcysteine regimens have been used to treat most patients successfully and prevent or mitigate hepatotoxicity. However, the rate of occurrence of adverse reactions to acetylcysteine is quite high, and there is a potential for these to be reduced. Recent studies show that distributing the loading‐dose of acetylcysteine over the first few hours of treatment may decrease the incidence of adverse reactions. In addition, varying the duration of acetylcysteine administration may potentially benefit certain cohorts of poisoned patients, depending on their risk of developing hepatotoxicity.