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PubMed2000

Peripheral retinal ablation for threshold retinopathy of prematurity in preterm infants.

BACKGROUND: This section is under preparation and will be included in the next issue. OBJECTIVES: In premature infants with threshold retinopathy of prematurity (ROP) does peripheral retinal ablation, by any means, reduce the incidence of adverse ophthalmic outcome? SEARCH STRATEGY: The standard search strategy of the Cochrane Neonatal Review Group was used. This included a search of the Cochrane Neonatal Group Register of Clinical Trials, MEDLINE, EMBASE, previous reviews including cross references, abstracts from pediatric and ophthalmologic meetings, letters and expert informants. Search terms included "Retinopathy of Prematurity" [MeSH Terms], "Retrolental Fibroplasia" [All Fields] and "Lightcoagulation" [All Fields] or "Cryosurgery" [All Fields]. In addition, a personal bibliographic database was used as a cross-reference. SELECTION CRITERIA: All trials in human premature infants with threshold ROP utilizing random or quasi random allocation to either peripheral retinal ablation of the avascular retina, by any means, or concurrent control group with independent outcome assessment were initially selected for review. Following methodologic review, only studies using random allocation were selected for data extraction. DATA COLLECTION AND ANALYSIS: Relevance and validity were assessed by the two authors and consensus reached. Each author extracted clinical outcomes from valid reports independently. Data analysis was conducted according to the standards of the Cochrane Neonatal Review Group. MAIN RESULTS: Two randomised trials were identified. Data from these studies show that peripheral retinal ablation reduces the risk of (1) early unfavorable retinal structure from 47. 9% to 28.1% (absolute risk reduction 19.8% [95% CI 27.9 - 11.8%]), (2) unfavorable retinal structure in early childhood from 44.3% to 26.3% (absolute risk reduction 18% [95% CI 27.0 - 9.1%]) and (3) unfavorable visual acuity in early childhood from 63% to 50.6% (absolute risk reduction 12.2% [95% CI 21.2 - 3.1]). In addition, visual fields in sighted eyes were slightly smaller in the treated (51.3 degrees +/- 11.8 degrees ) group as compared to the control (58.2 degrees +/- 14.5 degrees ) group. REVIEWER'S CONCLUSIONS: Peripheral retinal ablation reduces the incidence of adverse ophthalmic outcome in premature infants with threshold ROP. In sighted eyes, peripheral retinal ablation may reduce the size of the visual field. At this stage, long term outcomes remain unknown.

Cryosurgery↗
PubMed1994

Rate process model for arterial tissue thermal damage: implications on vessel photocoagulation.

A numerical model for thermal damage to human arterial tissue is presented, based on protein denaturation kinetics. The model involves determination of coefficients of rate processes A & delta E, which are tissue type-dependent (arterial tissue in this study), and definition of threshold damage. A feedback-controlled constant surface temperature device was used to induce 80 coagulative lesions of arterial human tissue ranging in temperature from 66 degrees C to 76 degrees C and in duration from 15 to 1,500 seconds. The measured coefficients were determined to be A = 5.6 x 10(63) s-1 and delta E = 430 KJ mole-1. These numerical values closely approximate the coefficients of the rate process for denaturation of collagen molecules. These and other histological observations strongly suggest collagen to be the primary coagulating component of arterial tissue at the onset of thermal coagulative damage. The ability of this model to predict onset of tissue coagulation during laser coagulation was studied using 10 postmortem human arterial samples exposed to argon laser irradiation.

Algorithms↗
PubMed2002

Analysis of ulcer data using hierarchical generalized linear models.

In multi-centre clinical trials, heterogeneities in individual hospital treatment effects can be modelled as random effects. Estimates of the individual hospital treatment effects and estimate of the mean treatment effect, allowing for the presence of overall hospital differences, are required, together with some measure of their uncertainty. Systematic inferences from the hierarchical-likelihood are now possible, using hierarchical generalized linear models. We show how to construct profile likelihoods for the treatment effects of individual hospitals.

Data Interpretation, Statistical↗
PubMed1981

Time-dependent decrease in the extent of visual deafferentation in the lateral geniculate nucleus of adult cats with small retinal lesions.

Small, round photocoagulator lesions of 3-6 degrees (0.6-1.2 mm) diameter were placed nasally on the retina of adult cats. Histological controls proved the complete destruction of all retinal layers within the lesions. Changes in lesion size by shrinkage of the retinal scar did not exceed 0.1 mm or 0.5 degrees. At different times after photocoagulation, single cells were recorded in layers A and A1 of the contralateral lateral geniculate nucleus (LGN) with tungsten microelectrodes. Acute lesions of this size completely deafferented single LGN cells in layer A whose receptive field (RF) area was within the lesion. Thirty days and more after coagulation, light-excitable cells were detected in the originally deafferented LGN region, with RFs in the immediate surround of the retinal lesion. The spontaneous activity and light excitability of these neurons were altered. The representation of 3-4 degrees retinal lesions at 20 degrees horizontal eccentricity was found to be completely filled in by excitation in the LGN. Excitation had spread from the unsevered parts of the retina into the region of deafferentation. Single cells with signs of multiple activation from more than one border region of the retinal lesion were occasionally detected.

Animals↗
PubMed2006

A randomized controlled trial to evaluate the efficacy of ultrasound-guided laser photocoagulation for treatment of benign thyroid nodules.

This randomized controlled study was designed to test the efficacy and safety of percutaneous ultrasound (US)-guided laser photocoagulation (PLP) for treatment of subjects with compressive symptoms due to benign thyroid nodules and/or at high surgical risk. Twenty six subjects were randomized to the intervention (no. 13, age 68+/-3 yr, mean+/-SEM) or observation (no. 13, age 71+/-2 yr) groups. In the control group, the volume of nodules did not significantly change over the 30 week period of observation. In the intervention group, median nodule volume at baseline was 8.2 ml (range 2.8-26.9) and was not significantly different from that of the control group. Nodules decreased significantly (p<0.0001) by 22% after 2 weeks (6.5 ml; range 2.4-16.7) and by 44% after 30 weeks (4.6 ml; range 0.69-14.2). Energy given was correlated (p<0.05) with the reduction of thyroid nodule volume. All patients tolerated the treatment well and reported relief from compressive and cosmetic complaints (p<0.05). At the time of enrolment 7/13 (54%) and 6/13 (46%) of patients in the intervention and control groups, respectively, had sub clinical hyperthyroidism. PLP normalized thyroid function at 6 and 30 weeks after treatment. In conclusion, PLP is a promising safe and effective procedure for treatment of benign thyroid nodules in patients at high surgical risk.

Aged↗
PubMed1975

Intracellular postsynaptic potentials of cat lateral geniculate cells and the effects of degeneration of the optic terminals.

(1) The synaptic signal transmission was studied in the lateral geniculate nucleus (LGN) during the late phase of degeneration, 50-80 h after light coagulation of the optic disc and the retinal vessels of one eye. Postsynaptic potentials and action potentials were intracellularly recorded from normal LGN principal cells (N-cells) and cells with degenerating optic terminals (D-cells). EPSPs and postsynaptic action potentials were elicited by electrical stimulation of the optic tract. Two neuronal classes (I and II) were characterized according to their response latency to optic tract stimuli. (2) Spontaneous small EPSPs and slow changes of the membrane potential were found in D-cells and the EPSP-IPSP pattern normally present in N-cells was absent. (3) The responses to optic tract stimuli applied at low stimulus frequencies (less than 5 stimuli/sec) were identical in D-cells and N-cells. (4) At higher stimulus frequencies (greater than 50 stimuli/sec), the EPSP amplitude was, on average, significantly smaller in D-cells than in N-cells. (5) At frequencies above 50 stimuli/sec, the fluctuation of the EPSP amplitudes and the latency scattering of postsynaptic action potentials were larger in D-cells than in N-cells. (6) The slope of the rising phase of the EPSPs increased slightly in N-cells and decreased in D-cells when the stimulus frequency was raised from 5/sec to 100/sec (class I cells). (7) The decay time constant of the EPSP, the latency of the onset and the peak amplitude of EPSPs did not change during degeneration. (8) The hypothesis put forward to account for the results is that the amount of transmitter released by each action potential in degenerating terminals is reduced, but its variability is increased. This is probably caused by a reduction in both the transmitter reserve and the transmitter resynthesis, and also by a larger fluctuation of the size of transmitter quanta.

Action Potentials↗
PubMed2002

Endoscopic photocoagulation of the ciliary body after repeated failure of trans-scleral diode-laser cyclophotocoagulation.

PURPOSE: To report the successful control of intraocular pressure with endoscopic cyclophotocoagulation after repeated failure of trans-scleral diode-laser cyclophotocoagulation. DESIGN: Interventional case report. METHODS: A 3 1/2-year-old child had intraocular pressure around 30 mm Hg in one eye despite full medical treatment and three procedures of trans-scleral diode laser photocoagulation. RESULTS: Endoscopic view of the ciliary body revealed many misplaced laser burns in the pars plana region. Using direct endoscopic visualization of the ciliary body, precise, confluent burns were applied to the ciliary body. Six months after the procedure, intraocular pressure has remained under 20 mm Hg. CONCLUSION: Endoscopic cyclophotocoagulation can effectively lower intraocular pressure after recurrent external diode-laser photocoagulation has failed to do so. The direct visualization during the endoscopic procedure is particularly advantageous in cases with atypical ciliary body morphology, such as in pediatric glaucoma.

Child, Preschool↗
PubMed1994

Transscleral contact krypton laser cyclophotocoagulation for treatment of glaucoma.

PURPOSE: To evaluate the usefulness of the krypton laser for transscleral contact cyclophotocoagulation. METHODS: Transscleral contact krypton laser cyclophotocoagulation was performed in 62 eyes of 57 patients with therapy-resistant glaucoma. A minimum follow-up for 6 months was obtained for 59 eyes. The krypton laser was delivered via a fiberoptic probe with compression of the sclera by the probe. The energy used was 4 to 5 J per application at the tip of the probe with an exposure time of 10 seconds. RESULTS: The intraocular pressure (IOP) decreased from the baseline mean of 34.8 +/- 11.0 mmHg to 20.4 +/- 8.3 mmHg within 10 days, to 22.6 +/- 12.5 mmHg at 1 month, to 21.3 +/- 11.3 mmHg at 3 months, and to 20.9 +/- 9.1 mmHg at 6 months postoperatively. Intraocular pressures of 8 to 24 mmHg were obtained in 62% of the eyes at 1 month, 60% at 3 months, and 73% at 6 months postoperatively with one or more cyclophotocoagulations but no other hypotensive procedures. The corresponding success rates after 6 months were 82% for eyes in which the procedure was performed to preserve vision and 50% for eyes in which the procedure was performed to relieve pain. No clinical signs of scleral injury or cyclodestruction-related loss of vision were detected. CONCLUSIONS: Krypton laser cyclophotocoagulation appears to be an effective and well-tolerated means of lowering IOP in therapy-resistant glaucoma. An advantage of the method is that standard retinal krypton photocoagulators can be used for the procedure.

Ciliary Body↗
PubMed1986

[Diminution of myopia following operation of macular hole-induced retinal detachment].

This paper presents an assessment of the diminution of myopia in 25 eyes after surgery according to the technique of G. P. Theodossiadis for retinal detachment due to a macular hole. The procedure consists in the stretching and fixation of a silicone sponge at the posterior pole and dispenses entirely with either cryocoagulation or light coagulation. The sponge is stretched and fixed to the sclera at both ends (12 and 6 o'clock), far from the posterior pole. The scleral protrusion thus obtained in the macular area leads to a considerable diminution of the high myopia usually present in such cases. The reduction of myopia is proportionate to the degree of protrusion of the scleral buckle, which in turn depends on the stretching of the sponge and on the amount of subretinal fluid released.

Humans↗
PubMed2006

Treatment of recurrent epistaxis in HHT.

No optimal treatment modality is currently available for the treatment of recurrent epistaxis in HHT. In this review, different therapeutic concepts are discussed together with their pathophysiologic background. Patients often profess a preventive effect for nasal ointments and use packings which can be self-administered in the case of bleeding. An effective first-line treatment for physicians is the endonasal laser coagulation or argon plasma coagulation. A second line surgical procedure is septodermoplasty according to Saunders which can provide long-lasting relief if performed correctly. There have been reports on antifibrinolytic agents and hormones, but their efficacy has yet to be determined.

Animals↗
PubMed2005

Minimally invasive techniques in orthopedic oncology: radiofrequency and laser thermal ablation.

Image-guided percutaneous thermal ablation is a safe and effective method to reduce pain in patients with painful bone tumors. Computed tomography-guided radiofrequency or laser ablation is the modality of choice for most osteoid osteomas. Radiofrequency or laser thermal ablation also offers an alternative method for palliation of localized, painful osteolytic metastatic lesions. Pain can be reduced and neural damage prevented, improving the quality of life for patients with cancer who often have multimorbid conditions and limited life expectancy. A multidisciplinary approach that includes orthopedic surgeons, neurosurgeons, medical and radiation oncologists, and interventional radiologists is essential to manage these patients.

Bone Neoplasms↗
PubMed1999

[Diode laser trans-scleral cyclo-photo-coagulation].

The purpose of this study is to present the results of treatment of refractory glaucoma with diode laser transscleral cyclophotocoagulation (DLCT). 88 patients (from 10 to 91 years old) were treated with diode laser. The follow up was 6 months. Mean intraocular pressure (IOP) before treatment was 38.2 mm Hg, 1 week after treatment--23.8 mm Hg, 1 month after treatment--21.3 mm Hg, after 6 months--19.0 mm Hg. We repeated treatment in 5 patients (5.6%). In 2 patients we observed hypotony--about 2 mm Hg. Diode laser cycloablation is a relatively safe and effective method in treatment of advanced refractory glaucoma.

Adolescent↗
PubMed2000

Transpupillary laser phototherapy of tumors and vascular anomalies of retina and choroid: theoretical approach and clinical implications.

BACKGROUND: Small retinal and choroidal tumors situated near the optic nerve or macula, such as retinoblastomas and malignant melanomas, as well as various other anomalies, in particular vascular malformations, may successfully be treated by photocoagulation. Model assumptions geared towards maximizing efficiency and minimizing undesirable side effects are forwarded, and the most important parameters subserving photothermal destruction, such as radiation field and thermal energy, analyzed. The influence exerted by physical traits of various tissues involved are also considered. METHODS: The model approximations presented are based on classical radiation and absorption laws, as well as on the scattering properties of the various tissues implicated, these being considered as a function of wavelength and their relevance to the photodestructive task at hand. Particular attention is paid to the rate processes and reaction kinetics of irradiated proteins. CONCLUSIONS: Radiation sources emitting in the near-infrared range of the electromagnetic spectrum, such as the diode (810 nm) and the cw Nd:YAG (1064 nm) lasers, are optimal for the treatment of tumors and large, voluminous entities (such as Hippel-Lindau angiomas), owing to the good tissue penetration properties of their light. Those emitting in the shorter wavelength range, such as the argon ion (488 and 514 nm) and first harmonic--mode Nd:YAG (532 nm) lasers, are not suitable for such tasks, but they are ideal for the destruction of fine sanguinous structures, within which their light is strongly absorbed but through which it penetrates poorly. For the treatment of large anomalous structures, a combined short/long wavelength--strategy should also be considered as a viable alternative. Such a "wavelength mixture" is emitted by the xenon high pressure lamp of the once renowned Meyer-Schwickerath light coagulator. The precision and safety of photothermal destruction methods depend, in the first approximation, upon the details of the pulse energy deposition (wavelength, pulse height and duration, pulse dynamics, mode composition, focussing), the choice of which is determined by the optical and thermal constants of the irradiated tissues. Higher pulse energies will, of course, be more effective in destroying neoplastic cells, but the risk of producing undesired collateral heat damage will also increase concomitantly. Until we can ascertain the physical properties of the pathological tissues treated with certainty, we will hardly be able to achieve more than an approximation of an ideal treatment strategy. But with increasing developments in in vivo-diagnostic techniques, we expect that this goal will be attainable in the not too distant future.

Animals↗
PubMed2001

[New therapies for the treatment of age-related macular degeneration].

Age-related macular degeneration has a natural progression from the precursors (the drusen) towards atrophic or neovascular complications. Choroidal neovascularization is undoubtedly the aspect of the disease that benefits most from new therapeutical approaches. Destructive photocoagulation based on fluorescein angiography has demonstrated since 20 years its efficiency on choroidal neovascularization. The same approach based on indocyanine green (ICG) angiography would increase the number of patients available to therapy. Very recently photodynamic therapy has demonstrated its efficiency to stabilize visual acuity at least at two years in patients with choroidal new vessels predominantly well defined. Other treatment developments are considered, such as refinement of photocoagulation techniques or of surgery. Until now, none has demonstrated its efficiency although they raise justified hopes. The future approaches rely upon the progress of the research both in physiopathology of the disease and on the angiogenic process requiring a constant interaction with all thematics of research. Finally, palliative treatments will be required before heading up to a preventive treatment.

Aged↗