Laser treatment of retinal diseases by subthreshold laser effects

The retinal pigment epithelium (RPE) may play an important role in the therapeutic effect of laser photocoagulation. This suggests a benefit from targeting the RPE instead of the sensory retina. Calculating the actual temperature profile after laser photocoagulation, it can be shown that pulse durations have to be in the order of microseconds (micros) to spare the retina from damage. This is consistent with histological findings after laser exposure with repetitive, 5 micros Nd:YLF laser pulses (527 nm). Therapeutic effects have been shown in patients with diabetic macular edema, drusen, and central serous retinopathy.     

Der stereoselektive Nachweis von l- und d-Methadon in Blutproben von lebenden und verstorbenen Drogenabhängigen

In Germany, there is a special situation that racemic dl-methadone and the (biologically effective) l-form (levomethadone) are both used as a substitute for heroin. The therapeutic effect of methadone is stereo-specific and the metabolism is also enantioselective. Therefore an approach to the dose-effect relationship of methadone requires an enantioselective analytical separation. For this a HPLC method was optimised especially for post-mortem blood samples. After liquid/¶liquid extraction with 1-chlorobutane, the extract was separated on a column combination of 4 cm CN and 10 cm chiral AGP phases with the solvent AcN/ 0.01 M PO₄ buffer ¶pH 5.0/ dimethyloctlyamine (15/85/0.5). ¶The methadone enantiomers elute baseline separated at approx. 15 min (l-form) and ¶18 min (d-form). The two EDDP-enantiomers and drugs which are frequently consumed supplementary to methadone such as heroin, cocaine, benzodiazepines, tricyclic antidepressants, antiepileptics etc. , do not interfere with detection. With this method the methadone l/d-ratio was determined in 93 serum samples from living addicts and 106 post-mortem blood samples from drug deaths. From the l/d-ratio and the concentration of total methadone as determined by other methods (GC-MS or RP-HPLC) the l-methadone concentration was calculated. In approximately 50% of the post-mortem samples the l-methadone concentration was higher than 0.3 mg/l, whereas this level was exceeded in only one of the living persons. ¶If dl-methadone was taken, the individual l/d-ratio in blood samples from living as ¶well as deceased persons differed greatly ranging from approx. 25/75 to 75/25, with ¶a mean of 50/50. In samples from 1999, ¶l-methadone was found exclusively in approx. 20% of the cases. In some cases it was obvious that both l- and dl-methadone had been used. Fatal cases with high l-methadone concentrations (>1 mg/l) gave rise to concern, because the l/d-ratio greatly exceeded 50/50in all cases . This could be considered as an indication of an individually extremely slow metabolism of l-methadone in these cases, resulting in an accumulation of l-methadone. These examples from the forensic casework demonstrate the necessity of an enantioselective quantification of ¶l-methadone as used for therapeutic drug monitoring and in forensic cases.     

Unexpected results found in larvae samples from two postmortem forensic cases

Forensic Toxicology - In forensics, entomological specimens can be used as additional/alternative matrices to detect xenobiotics when human specimens are limited in their application. Despite some...     

Clinical results of intravitreal administration of tissue-type plasminogen activator (tPA) and gas for removal of subretinal hemorrhage in senile macular degeneration

BACKGROUND: Subretinal hemorrhage in age related macular degeneration (AMD) usually causes acute visual loss and is associated with poor visual prognosis. In order to prevent retinal damage and to perform laser treatment of the underlying choroidal neovascularization (CNV) the subretinal hemorrhage has to be removed from the macular region. This could be achieved by intravitreal injection of tissue plasminogen activator (tPA) and gas. PATIENTS AND METHODS: In 8 consecutive patients, suffering from a massive macular hemorrhage (duration of visual problems: mean 9 days), tissue plasminogen activator (tPA) (40 micrograms in 400 microliters BSS) and SF6-gas (0.75 ml) was transsclerally injected into the vitreous cavity to achieve liquification and displacement of the hemorrhage. RESULTS: In all patients liquification and displacement of the hemorrhage out of the macular region was achieved during follow up. During the first week after operation a significant increase of visual acuity was noticed in all patients, however ophthalmoscopically there was just little reduction of the hemorrhage in the foveolar area. After successful removal of the blood the choroidal neovascularization was treated successfully by laser coagulation in one patient. No laser treatment was performed in the other patients because of the subfoveal location of the neovascularisation or because of disciform scar. Visual acuity increased 4 lines after surgery. In one case the procedure was complicated by a persistent vitreous hemorrhage and vitrectomy had to be performed in another patient due to an endophthalmitis. CONCLUSION: Intravitreal injection of tPA assisted gas displacement of subretinal hemorrhage due to AMD leads to a significant increase of visual acuity during the first week after operation. Although a nearly complete removal of the hemorrhage out of the macular area could be achieved, it was difficult to differentiate this from the spontaneous course. Laser photocoagulation could be performed in only few cases.     

Threshold determinations for selective retinal pigment epithelium damage with repetitive pulsed microsecond laser systems in rabbits

BACKGROUND AND OBJECTIVE: In both clinical and animal studies, it has been shown that repetitive short laser pulses can cause selective retinal pigment epithelium damage (RPE) with sparing of photoreceptors. Our purpose was to determine the ophthalmoscopic and angiographic damage thresholds as a function of pulse durations by using different pulsed laser systems to optimize treatment modalities. MATERIALS AND METHODS: Chinchilla-breed rabbits were narcotized and placed in a special holding system. Laser lesions were applied using a commercial laser slit lamp, contact lens, and irradiation with a frequency-doubled Nd:YLF laser (wave-length: 527 nm; repetition rate: 500 Hz; number of pulses: 100; pulse duration: 5 micros, 1.7 micros, 200 ns) and an argon-ion laser (514 nm, 500 Hz, 100 pulses, 5 micros and 200 ms). In all eyes, spots with different energies were placed into the regio macularis with a diameter of 102 microm (tophat profile). After treatment, fundus photography and fluorescein angiography were performed and radiant exposure for ED50 damage determined. Speckle measurements at the fiber tips were performed to determine intensity peaks in the beam profile. RESULTS: Using the Nd:YLF laser system, the ophthalmoscopic ED50 threshold energies were 25.4 microJ (5 micros), 32 microJ (1.7 micros), and 30 microJ (200 ns). The angiographic ED50 thresholds were 13.4 microJ (5 micros), 9.2 microJ (1.7 micros), and 6.7 microJ (200 ns). With the argon laser, the angiographic threshold for 5 micros pulses was 5.5 microJ. The ophthalmoscopic threshold could not be determined because of a lack of power; however, it was > 12 microJ. For 200 ms, the ED50 radiant exposures were 20.4 mW ophthalmoscopically and 19.2 mW angiographically. Speckle factors were found to be 1.225 for the Nd:YLF and 3.180 for the argon laser. Thus, the maximal ED50 -threshold radiant exposures for the Nd:YLF were calculated to be 362 mJ/cM2 (5 micros), 478 mJ/cm2 (1.7 micros), and 438 mJ/cm2 (200 ns) ophthalmoscopically. Angiographically, the thresholds were 189 mJ/cm2 (5 micros), 143 mJ/cm2 (1.7 micros), and 97 mJ/cm2 (200 ns). For the argon laser, the maximal ED50 radiant exposure threshold was 170 mJ/cm2 angiographically. CONCLUSION: The gap between the angiographic and the ophthalmoscopic thresholds for the 200 ns regime (4.5 times above angiographic ED50) was wider than for the 1.7 micros regime (3.3 times above the angiographic ED50). This would suggest the appropriate treatment would be 200 ns pulses. However, histologies have yet to prove that nonvisible mechanical effects increase with shorter pulse durations and could reduce the "therapeutic window." When comparing the thresholds with 5 micros pulses from the argon and Nd:YLF laser, it demonstrates that intensity modulations in the beam profile must be considered.     

Scientific comment on the German human biological monitoring values (HBM values) for mercury

No Abstract     

Selective retina therapy in patients with central serous chorioretinopathy

Background Central serous chorioretinopathy (CSC) is a disease with a localized breakdown of the outer blood–retinal barrier located within the retinal pigment epithelium (RPE) causing subretinal fluid accumulation. Selective retina therapy (SRT) is a new, minimally invasive laser technology that has been designed to selectively target the RPE. SRT spares retinal tissue.Methods Twenty-seven eyes of 27 patients with active CSC were treated with SRT using a pulsed double-Q-switched Nd-YLF prototype laser (λ=527 nm, t=1.7 μs). At baseline, best-corrected visual acuity was determined and fluorescein angiography and optical coherence tomography were performed. The patients were followed for up to 3 months.Results After 4 weeks 85.2% of patients showed complete resolution of subretinal fluid and in 96.3% there was no leakage visible on fluorescein angiography. After 3 months 100% of patients demonstrated no subretinal fluid and 100% of patients had no leakage activity on fluorescein angiography. Visual acuity, 20/40 at baseline, improved to 20/28 after 4 weeks and to 20/20 after 3 months.Conclusion SRT is a safe and effective treatment for active CSC. Especially if the RPE leak is located close to the fovea, SRT is the favoured therapeutic option. We recommend earlier treatment of patients with acute CSC in order to prevent development of chronic changes due to CSC with irreversible anatomical and functional damage. SRT might be considered as a first-line treatment for active CSC.     

Pars plana vitrectomy, phacoemulsification and intraocular lens implantation. Comparison of clinical complications in a combined versus two-step surgical approach

Purpose To report intra-and postoperative complications in pars plana vitrectomy, phacoemulsification and intraocular lens implantation. A comparison of the combined versus two step surgical approach is given.Method Medical records and operative notes of 111 eyes with combined surgery and 50 eyes with sequential surgery were retrospectively analysed. Subgroup analysis was performed to evaluate differences in disease groups, the use of endotamponading or endolaser and cryocoagulation. Postoperative follow-up time was between 3 and 18 months.Results Combined surgery: 64 eyes (57.5%) showed no complications. 17 eyes (15.3%) showed transient intraocular pressure rise, 17 eyes (15.3%) fibrinous exudation in the anterior chamber. Posterior capsule tears occurred in 7 eyes (6,3%), formation of posterior synechia was observed in 7 eyes (6.3%). IOL dislocation was seen in 3 eyes (2.7%), heavy covering of macrophages in 3 eyes (2,7%). Rare complications included silicon oil efflux into the anterior chamber (1.8%), anterior chamber hemorrhage (1,8%) and iris incarceration into the corneoscleral incision (0,9%). One eye needed explantation of the IOL during the follow-up. Sequential surgery: 31 eyes (62%) showed no complication. Transient intraocular pressure rise occurred in 14 eyes (28%), fibrinous exudation in 2 eyes (4%). Formation of posterior synechia was observed in 1 eye (2%), posterior capsule tears occurred in 4 eyes (8%). Dislocation of the IOL was seen in 1 eye (2%). Subgroup analysis revealed fibrinous exudation in the anterior chamber to be significantly more frequent after combined surgery, particularly in cases of proliferative diabetic retinopathy.Conclusion Combined pars plana vitrectomy, phacoemulsification and intraocular lens implantation as well as the two-step procedure are safe and effective. Sequential surgery could be advantageous to minimize the postoperative anterior chamber inflammatory response.