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Veit-Peter Gabel

Publications and source records attributed to Veit-Peter Gabel.

13 recordsLinked to original sources
PubMed2006

Surgical removal of idiopathic epiretinal membrane with or without the assistance of indocyanine green: a randomised controlled clinical trial.

PURPOSE: To carry out a prospective investigation of the functional and morphological outcome of idiopathic epiretinal membrane (IEM) surgery with or without the assistance of indocyanine green (ICG) in a randomised controlled clinical trial. METHODS: Sixty patients who underwent vitrectomy with removal of IEM combined with cataract surgery were randomly allocated to two groups: 27 patients were operated on with ICG 0.1% in glucose 5%, 33 patients without ICG. Functional outcome was assessed 3-4 months postoperatively with improvement of best-corrected visual acuity (BCVA), Amsler grid test, and automated and kinetic perimetry. Postoperative residual or recurrent IEM was assessed with bio-microscopy, and macular oedema with optical coherence tomography (OCT). Improvement in BCVA was the main outcome measure. RESULTS: BCVA improved in 49 patients, remained unchanged in five and decreased in five. Improvement in BCVA and reduction of macular oedema were statistically significant within both groups (P < 0.01). Improvement in BCVA was not statistically significantly different whether ICG was used or not [0.17 (logarithm of minimum angle of resolution; logMAR) with ICG and 0.24 (logMAR) without ICG] (P = 0.59). There was no statistically significant difference in preoperative or postoperative BCVA, reduction of macular oedema, postoperative Amsler grid test, or incidence of residual or recurrent IEM between the two groups. Visual field defects were detected in two patients operated on with ICG. CONCLUSIONS: Removal of IEM with or without the assistance of ICG equally improved visual function and macular morphology.

Aged↗
PubMed2006

Optical coherence tomography findings in idiopathic juxtafoveal retinal telangiectasis.

PURPOSE: To describe optical coherence tomography (OCT) findings in patients with juxtafoveal retinal telangiectasis (JRT). METHODS: Fourteen consecutive patients (28 eyes) with JRT (12 patients with JRT type II, one with JRT type I and one with JRT type III) were examined using fluorescein angiography (FA) and OCT. RESULTS: Despite prominent leakage in FA, macular oedema was absent in all 26 eyes with type II JRT. In contrast to that, in patients with type I and type III JRT, cystoid macular oedema was evident. In 14 of 28 eyes (all with type II JRT), a single foveal cyst was found in OCT. It varied significantly in size and was associated with visual acuity decrease. An intraretinal hyperreflective lesion was seen in eight of 28 eyes and flattening of the fovea in three eyes. CONCLUSIONS: Foveal cyst, absent macular oedema, intraretinal hyperreflective lesions and foveal flattening were the most common OCT findings in patients with JRT type II. These may represent progressive loss of retinal tissue, possibly due to Müller cells degeneration, and provide additional diagnostic criteria for JRT.

Aged↗
PubMed2006

Correlation between optical coherence tomography and autofluorescence in acute posterior multifocal placoid pigment epitheliopathy.

PURPOSE: To report a case of bilateral acute posterior multifocal placoid pigment epitheliopathy (APMPPE) evaluated by optical coherence tomography (OCT), fundus autofluorescence (AF) and microperimetry, both in the acute phase and after resolution of symptoms. METHODS: Complete ophthalmological evaluation, including fluorescein angiography, OCT, AF, and microperimetry upon presentation and 1 month later, after lesions have subsided. An attempt to correlate the findings on presentation and changes after resolution is performed using the results of these new investigational techniques. RESULTS: APMPPE showed hyperreflectance in OCT at the level of the outer retinal layers, without increase in retinal thickness. AF revealed early decreased fluorescence due to a masking effect, and later reveals increased fluorescence after resolution of OCT findings. Function is disturbed at the lesion sites, as shown by microperimetry, and later returns to near normal values on microperimetry. CONCLUSION: APMPPE shows outer retinal layers changes on OCT, which resolve totally after subsidence of the acute phase. AF shows areas of increased fluorescence after resolution, with near normal return of function on microperimetry.

Acute Disease↗
PubMed2006

Safety testing of indocyanine green in an ex vivo porcine retina model.

PURPOSE: To assess retinal toxicity of indocyanine green (ICG) in a porcine ex vivo perfusion organ culture model, and to measure intraretinal penetration of ICG applied to the retinal surface. METHODS: The retinal surface of fresh porcine retinal tissue was exposed to ICG 0.1% and 1% dissolved in glucose 5% for 1 and 30 minutes with and without concomitant illumination. Specimens were then kept in perfusion organ culture for 24 hours before examination by light microscopy and the TUNEL technique. Tissue samples treated with DNAse served as positive controls, and samples exposed to saline served as negative controls. Fluorescence microscopy was used to localize ICG at 1 minute, 60 minutes, 2 hours, and 3 hours after a 1-minute exposure of the retinal surface to ICG 1%. RESULTS: No increase in TUNEL-positive cells was observed after exposure to ICG 0.1% for 1 minute. Moderate apoptosis was found after 1-minute exposure to ICG 1% and 30-minute exposure to ICG 0.1%, and severe apoptosis was found after 30-minute exposure to ICG 1%. Concomitant application of light did not influence the degree of apoptosis. No signs of cell necrosis were found. After 1-minute exposure of the retinal surface, ICG 1% gradually penetrated the entire retina. CONCLUSIONS: ICG induced apoptosis but not necrosis in all nuclear retinal layers in a dose-dependent manner. Brief exposure to ICG 0.1% for 1 minute and illumination for 3 minutes simulated the intraoperative use of ICG. No retinal apoptosis or necrosis was observed. ICG briefly applied to the retinal surface gradually penetrated the entire retina.

Animals↗
PubMed2005

[The influence of ionizing radiation on the development of posterior capsule opacification in vitro].

BACKGROUND AND PURPOSE: Histologically, the posterior capsule opacification (PCO) corresponds to regenerative tissue of transformed lens epithelial cells (LECs) with extracellular matrix production. In this study, the influence of ionizing radiation on proliferating LECs and the development of PCO was investigated in vitro. MATERIAL AND METHODS: Each four and 14 pork lenses, respectively, were irradiated with 6 MeV electrons with single doses of 8, 10, 12, and 20 Gy. 1-2 h after irradiation the lens was removed by capsulorrhexis and hydrodissection. After fixation of the capsular bag in a special device the proliferation of residual LECs was examined daily. The experiment was considered to be finished when the capsular bag was completely opacified by confluent cell proliferates. RESULTS: Single dose irradiation with electrons in a dose range from 8 to 12 Gy significantly protracted the development of PCO with complete inhibition of PCO after application of 20 Gy. CONCLUSION: To inhibit PCO in vitro, a single dose of 20 Gy is necessary. The actual in vitro model allows an optimal investigation of PCO formation under different external influences and is therefore very suitable for radiobiological questions.

Animals↗
PubMed2005

Preferential Hyperacuity Perimeter (PreView PHP) for detecting choroidal neovascularization study.

PURPOSE: To assess the ability of the Preferential Hyperacuity Perimeter (PreView PHP; Carl Zeiss Meditec, Dublin, CA) to detect recent-onset choroidal neovascularization (CNV) resulting from age-related macular degeneration (AMD) and to differentiate it from an intermediate stage of AMD. DESIGN: Prospective, comparative, concurrent, nonrandomized, multicenter study. PARTICIPANTS: Eligible participants' study eyes had a corrected visual acuity of 20/160 or better and either untreated CNV from AMD diagnosed within the last 60 days or an intermediate stage of AMD. METHODS: After obtaining consent, visual acuity with habitual correction, masked PHP testing, stereoscopic color fundus photography, and fluorescein angiography were performed. Photographs and angiograms were evaluated by graders masked to diagnosis and PHP results. The reading center's diagnosis determined if the patient was categorized as having intermediate AMD or neovascular AMD. MAIN OUTCOME MEASURES: A successful study outcome was defined a priori as a sensitivity of at least 80% and a specificity of at least 80%. RESULTS: Of 185 patients who gave consent to be enrolled, 11 (6%) had PHP results judged to be unreliable. An additional 52 were not included because they did not meet all eligibility criteria. Of the remaining 122 patients, 57 had an intermediate stage of AMD and 65 had neovascular AMD. The sensitivity to detect newly diagnosed CNV using PHP testing was 82% (95% confidence interval [CI], 70%-90%). The specificity to differentiate newly diagnosed CNV from the intermediate stage of AMD using PHP testing was 88% (95% CI, 76%-95%). CONCLUSIONS: Preferential Hyperacuity Perimeter testing can detect recent-onset CNV resulting from AMD and can differentiate it from an intermediate stage of AMD with high sensitivity and specificity. These data suggest that monitoring with PHP should detect most cases of CNV of recent onset with few false-positive results at a stage when treatment usually would be beneficial. Thus, this monitoring should be considered in the management of the intermediate stage of AMD.

Aged↗
PubMed2005

Fundus autofluorescence in acute and chronic-recurrent central serous chorioretinopathy.

PURPOSE: Central serous chorioretinopathy (CSC) affects mostly young and middle-aged adults. Typically, a serous retinal detachment occurs with a focal leakage point in fluorescein angiography. Fundus autofluorescence (AF) is related to the lipofuscin within the retinal pigment epithelium (RPE). As CSC is thought to be associated with RPE disorders, AF measurements might be able to detect distinct changes within the RPE level. The purpose of this study was to compare AF patterns in acute and chronic-recurrent CSC and to evaluate the potential value of AF as a non-invasive monitoring tool. METHODS: From 85 patients diagnosed with CSC (mean age 43 years), AF images were retrospectively evaluated and compared with angiographic and ophthalmoscopic findings. Fluorescein angiography and AF measurements were performed using a Heidelberg retina angiograph. Autofluorescence was excited at a wavelength of 488 nm and detected above 500 nm. RESULTS: Acute CSC as determined by an acute decrease in visual acuity (VA) within the last 6 weeks, focal point leakage and neurosensory retinal detachment was diagnosed in 39 patients. In 36 of those patients (92%), a significantly decreased AF at the leakage point (72%) and/or decreased AF in the area of neurosensory detachment (77%) were observed. Regarding chronic-recurrent CSC as determined by a decrease in VA for longer than 6 weeks and mottled hyperfluorescent appearance in angiography, abnormalities in AF were observed in 44/46 patients (96%). In those patients, decreased or mottled AF was observed at the leakage point itself (76%), whereas significantly increased AF was seen in the area of residual neurosensory retinal detachment (85%). CONCLUSIONS: In acute CSC, decreased AF is presumably due to a blockage caused by oedema, whereas in chronic-recurrent forms, irregular and increased AF is observed, possibly reflecting reactive RPE changes secondary to RPE defects and neurosensory detachment. If these findings could be systematically underlined by prospective clinical studies, AF might be an interesting non-invasive tool for monitoring RPE changes in CSC and for performing differential diagnosis.

Acute Disease↗
PubMed2004

Von Willebrand's disease type I as a cause for subvitreal, retinal and subretinal haemorrhages.

BACKGROUND: Young patients with vitreous, retinal and subvitreal haemorrhages without neovascularisation or prior trauma are a diagnostic challenge for the physician. In this case report, a patient is presented who developed unilateral, spontaneous, subvitreal, retinal and subretinal haemorrhages and was diagnosed with von Willebrand's disease. CASE REPORT: A 33-year-old Caucasian woman presented at our clinic with unilateral subvitreal, retinal and subretinal haemorrhages. The haemorrhages occurred spontaneously without prior trauma, and the patient had no history of prior bleeding complications. Analysis of the coagulation-fibrinolysis system and von Willebrand multimer analysis led to the diagnosis von Willebrand's disease type I. CONCLUSIONS: Spontaneous subvitreal, retinal and subretinal haemorrhages may be associated with coagulation disorders. Especially in young patients, von Willebrand's disease should be considered as a possible cause.

Adult↗
PubMed2004

Retinal replacement--the development of microelectronic retinal prostheses--experience with subretinal implants and new aspects.

BACKGROUND: Progress in the field of microelectronics has led to the development of visual prostheses for the treatment of blinding diseases. Different concepts of retinal replacement are currently under investigation. The aim of the retinal prostheses is to replace the function of lost photoreceptors in degenerative diseases, such as retinitis pigmentosa. METHODS: Within the field of visual prosthetic developments mainly two retinal based concepts are under investigation. One of the concepts is the epiretinal implant which acquires images of an external camera and after preprocessing by a computer reading this visual information into the human visual system. In the subretinal prosthesis design concept an array of stimulation electrodes is placed in the subretinal space. True to the concept the image falling on the retina and its light impulses are converted into electrical currents by microphotodiodes and the retina is stimulated with these locally. To test the feasibility of the concepts the biocompatibility and to determine basic stimulation parameters a lot of animal experiments and first human experiments were carried out. RESULTS: Currently the research conducted by teams in Germany, the USA and Japan into epiretinal and subretinal implants has reached the stage where clinical trials can now be performed. Individual pilot studies were carried out for both the epiretinal and the subretinal implant by different research groups. DISCUSSION: The results achieved by the researchers indicate that cortical action potentials can be triggered by electric retinal stimulation with both concepts. The experimental work has highlighted a whole range of obstacles, not all of which have yet been fully resolved. These findings offer hope that coarse restoration of vision may be feasible by electrical stimulation.

Animals↗
PubMed2002

Clinical findings on the use of long-term heavy tamponades (semifluorinated alkanes and their oligomers) in complicated retinal detachment surgery.

BACKGROUND: Heavy tamponades for pathologies in the lower part of the retina are a new development, and different tamponades have recently come into clinical use: semifluorinated alkanes (F(6)H(6), F(6)H(8)) and their oligomers (OL62HV). METHOD: Nine patients had been operated on using F(6)H(8) (n=5) and by OL62HV (n=4). In all cases the reasons for using the tamponades were complicated retinal detachments in the lower part. In three cases the use was primary and in six cases tamponades were used after reoperations. In all cases the endotamponade was removed within 6 weeks. Fluorescein angiography (FLA) was performed in the F(6)H(8) group. RESULTS: In the F(6)H(8)group dispersion developed in two of the three aphacic patients. In two out of five cases soft epiretinal membranes and cellular material could be found between the substance and the lower periphery. In two membranes examined by light microscopy, cystic cells and amorphous material could be found. In one case (PDRP, aphacic) cyclophotocoagulation had to be performed because of persistent elevated IOP. FLA was unremarkable. In the OL62HV group, severe recurrent PVR reaction occurred in the lower periphery (2/4) and unusual precipitates were observed (4/4). In one case, after a normal postoperative period (VA 0.05 after 5 days) an extensive cellular reaction on the complete surface of the tamponade occurred. After 5 weeks VA was no light perception. During removal of the oligomer unusual adherent cellular components were found on the surface of the retina. The retina appeared necrotic, showed constricted retinal vessels and there was optic atrophy. Histologically, fluffy epiretinal material and a lens capsule obtained from one eye filled with OL62HV resembled the appearance with F(6)H(8). CONCLUSION: Heavy endotamponades on the basis of semifluorinated alkanes can lead to an unusual biological reaction and need further investigation before clinical use.

Adult↗
PubMed2002

What is the meaning of threshold in laser injury experiments? Implications for human exposure limits.

The derivations of human exposure limits for laser radiation rely heavily upon experimental ocular injury studies. The limits are derived by committees of ophthalmic experts through a review of all available threshold data and an understanding of mechanisms of laser/tissue interaction. A major point of discussion in this derivation process relates to the level of uncertainty of the threshold of injury. An indication of the level of uncertainty relates to the slope of the transformed dose-response curve, or the "probit plot" of the data. The most cited point on the probit plot is the exposure that represents a 50% probability of injury: the ED-50. This value is frequently referred to as the "threshold," even though some experimental damage points exist below this "threshold." An analysis of any number of example data sets reveals that the slope in most experiments cannot be explained by biological variation alone. The optical, thermophysical, and biological factors influencing the probit plot are critically analyzed to provide guidance for deriving exposure limits. By theoretically modeling an experiment, small errors in focus are shown to produce a substantial change in the ED-50 and the slope of the probit plot.

Animals↗
PubMedDate not supplied

Fundus autofluorescence before and after photodynamic therapy for choroidal neovascularization secondary to age-related macular degeneration.

BACKGROUND AND OBJECTIVE: To describe fundus autofluorescence patterns in choroidal neovascularization secondary to age-related macular degeneration before and after photodynamic therapy (PDT). PATIENTS AND METHODS: Sixty-eight consecutive eyes were indicated for PDT after standard fluorescein angiography, which showed completely classic choroidal neovascularization (CNV) (n=52), occult with no classic CNV (n=7), and predominantly classic CNV (n=9). Standardized PDT was performed and patients were examined 2 to 3 months later. Angiography and autofluorescence measurements were performed again and compared with preoperative values. RESULTS: At baseline, autofluorescence was mainly decreased in areas of completely classic CNV (79%), but showed a regular or mottled pattern in occult CNV. A slightly increased (50%) or normal (50%) autofluorescence was seen at the rim of the classic lesions within the junctional zone. Membrane demarcation was improved (90%) in classic membranes 2 to 3 months after PDT. After PDT for occult membranes, a transformation into classic membranes with residual leakage and need for further PDT was observed (6 of 7 eyes), showing the described autofluorescence patterns. For the mixed type of CNV, both described patterns of autofluorescence distribution were found. CONCLUSION: Especially classic CNVs reveal distinct characteristics of significantly decreased autofluorescence, presumably due to their localization above the retinal pigment epithelium level, leading to blockage of autofluorescence. Autofluorescence patterns after PDT included enhanced demarcation of the membrane, suggesting reactive retinal pigment epithelial changes. Autofluorescence might be an interesting tool to distinguish noninvasively between classic and occult CNV in age-related macular degeneration and to monitor changes after PDT.

Choroidal Neovascularization↗