PubMed Health⌕ Search

Biomedical subjects

T Desmettre

Publications and source records attributed to T Desmettre.

At least 19 recordsLinked to original sources
PubMed2003

[Status of low-vision rehabilitation for age-related macular degeneration by orthoptists in the North of France].

AIM OF THE STUDY: To evaluate the status of low-vision rehabilitation carried out by the orthoptists in the North of France. This study was a preliminary step in setting up a network between different vision professionals for the management of age-related macular degeneration (AMD) the North of France. METHODS: The ASO (Association Septentrionale d'Ophtalmologie) conducted a survey funded by the URCAM (Union Régionale des Caisses d'Assurance Maladie) with the FAQSV (fond d'aide à la qualité des soins de ville). The survey was based on the analysis of two forms sent to orthoptists of the North region of France. RESULTS: The survey analyzed 46 responses (a representative sample with 69% responses) providing a description of the orthoptists of the North of France: 19% males, 81% females whose mean professional experience was 13.3 years. Thirty-four percent of the orthoptists have had training in low-vision rehabilitation. This training was given during the university courses for 21% of responders and during a postgraduate course for 79%. Of the orthoptists surveyed, 64% worked in a private context, 9% in a public context, and 27% in both public and private contexts. Their main activity was in their own private practice for 60%, in an ophthalmologist's office for 20%, in a public institution for 16%, and a private institution for 4%. The mean number of patients treated was 70 per week per orthoptist, with 21% working mostly with children, 36% working mainly with adults between 16 and 60 years of age, and 7% with the elderly, whereas 36% reported no specificity related to patient age. The mean number of patients dealt with for low vision related to AMD was 4.1 per month per orthoptist. The average number of patients dealt with for low vision with no relation to AMD was 1.5 per month. The prescriber of low-vision rehabilitation was an ophthalmologist for 88.9% of the orthoptists and a general practitioner for 11.1%. Questions addressed to AMD patients: at the beginning of the survey, 83.8% of the patients did not have sufficient visual acuity to be able to read a text of current size (Parinaud 4); 40.4% of the patients required help for everyday life, and 59.6% were autonomous. For 7.1% of the patients, low-vision rehabilitation was carried out less than 1 month after the stabilization of retinal lesions, but in 35.3%, rehabilitation was carried out more than 2 years after lesions were stabilized. The main request of the patients involved improvement of near vision (89.9%). CONCLUSION: This survey will be a preliminary step in setting up a regional health network coordinating the ophthalmological and orthoptic management of AMD.

Aged↗
PubMed2001

Heat shock protein hyperexpression on chorioretinal layers after transpupillary thermotherapy.

PURPOSE: To assess a biological effect induced by temperature elevation during transpupillary thermotherapy (TTT). METHODS: Six pigmented rabbits were anesthetized, and TTT was performed on the right eye using an 810-nm diode laser installed on a slit lamp (spot size, 1.3 mm; duration, 60 seconds; power, 92-150 mW). A series of laser pulses were aimed at the posterior pole of the retina. The left eyes were used as the control. Twenty-four hours after laser irradiation, a histologic study was performed on the chorioretinal layers. Tissue samples were fixed in formalin and embedded in paraffin. A monoclonal antibody was used to detect heat shock protein (Hsp)70 immunoreactivity, followed by a biotinylated goat anti-mouse antibody, revealed by the avidin-biotin complex and the 3-amino-9-ethyl-carbazole (AEC) chromogen. Retinal structures were further identified by hematoxylin erythrosin saffron (HES) coloration. RESULTS: The photocoagulation threshold was found to be at the 150-mW laser power. Under this threshold, Hsp70 immunostaining was the strongest at the 127-mW power, with staining of some choroidal cells, including capillary endothelial cells. No Hsp70 immunoreactivity was observed on the retina. At the 107-mW power, Hsp70 reactivity was observed only in occasional choroidal cells. At the 98-mW power, only mild, diffuse Hsp70 immunoreactivity was observed in the choroid. At the 92-mW power, as in nonirradiated eyes, no Hsp70 immunoreactivity was detected. CONCLUSIONS: Subthreshold transpupillary 810-nm laser irradiation induces choroidal Hsp hyperexpression. This confirms that choroidal Hsp hyperexpression can be induced during TTT, as has been recently hypothesized by several investigators.

Animals↗
PubMed2001

[Choroidal heat shock overexpression in transpupillary thermotherapy: preliminary results].

PURPOSE: To assess retinochoroidal overexpression of heat shock proteins (HSP-70) induced by a transpupillary laser irradiation below the photocoagulation threshold. METHODS: Four pigmented rabbits were anesthetized and TTT was performed on the right eye using a 810nm diode laser (Iridis, Quantel-Medical, France) adapted on slit lamp (spot size: 1.3 mm, duration: 60 seconds; power 92-150 mW). Series of laser impacts were aimed at the posterior pole of the retina. Left eyes were used as control. Twenty-four hours after laser irradiation, a histological study was done on chorioretinal layers. Tissue samples were fixed in formalin and embedded in paraffin. A monoclonal antibody was used to detect HSP-70 immunoreactivity (mouse IgGl, SPA-810, Stress Gen, Canada), followed by a biotinylated goat antimouse antibody (Dako, Denmark), revealed by the avidin-biotin complex (Vectastain kit, Vector, USA) and the AEC chromogen. Retinal structures were further identified by HES coloration. RESULTS: The photocoagulation threshold was obtained for laser power at 150 mW. Under this threshold, HSP-70 immunostaining was the strongest for power 127 mW with a staining of some choroidal cells, including capillary endothelial cells. No HSP-70 immunoreactivity was observed on the retina. For the laser power 107 mW, HSP-70 reactivity was observed only in occasional choroidal cells. For the laser power 92 mW, as for nonirradiated eyes, no HSP-70 immunoreactivity was detected. CONCLUSIONS: Transpupillary 810 nm laser irradiation under the photocoagulation threshold induces choroidal HSP overexpression. This study concludes that choroidal HSP overexpression can be induced during TTT.

Animals↗
PubMed1999

Quantitative fluorescein angiography following diode laser retinal photocoagulation.

OBJECTIVE: An in vivo study was done to establish if laser-induced damage of the retina could be quantified using fluorescein angiography. METHOD: This study was carried out on rabbit eyes (n = 6) with an 810 nm diode laser (spot diameter: 500 microm, pulse duration: 1 second, power: 100 mW-400 mW) adapted on a slit lamp. Fluorescence measurements were performed with a fundus camera connected to a fluorescence imaging system. Fluorescence staining of the retina was evaluated by mathematical modeling. Lesions were correlated to laser parameters and to histologic data. RESULTS: Image analysis shows that the laser lesions stained progressively. Fluorescence appears first at the borders of the lesion exhibiting a fluorescent ring. A progressive increase of the fluorescence into the central zone is observed. The maximum fluorescence intensity into the center of the laser spot is obtained after a delay depending on the laser energy. Below 100 +/- 20 mW, lesions are detectable by fluorescence imaging only. A fluorescence plateau appears for a threshold light dose above 200 +/- 20 mW. Mathematical modeling demonstrates that quantitative assessment of laser-induced damage to the retina is feasible using fluorescence imaging. CONCLUSION: The quantification of fluorescence staining in terms of both intensity and time can contribute to a better quantification of laser-induced damage. At last, since laser damage may mimic naturally occurring pathology, this method should also be considered to quantify different types of lesions.

Animals↗
PubMed1998

Indocyanine green: physicochemical factors affecting its fluorescence in vivo.

This study reinvestigates the spectral properties of ICG (Indocyanine green) in vivo, the role of quenching, and the possibility of an interaction of ICG with blood components and/or vessel walls. ICG quenching as a function of concentration was studied by spectrophotometry on whole blood samples from golden hamsters. Fluorescence ICG characteristics were evaluated by front-face fluorometry. In vivo, fluorescence measurements were performed on the femoral artery of golden hamsters. In vitro, on whole blood samples, fluorescence intensity is modified by ICG quenching as concentration increases above 80 microgram/ml. The maximum fluorescence peak is not affected and remains centered at 832 nm. The in vivo measurements display a similar fluorescence intensity shape, which is affected only by ICG concentrations. However, the maximum fluorescence emission peak is modified significantly with time. Between 0 and 120 min, four phases can be distinguished in which a wavelength shift from 826 to 835 nm is observed. The wavelength shift with change in fluorescence intensity observed in vivo could be due to a localization of ICG molecules in sites more hydrophobic than serum proteins. It is possible to hypothesize the presence of an endothelium-bound form with a specific fluorescence spectrum. The amphiphilic properties of ICG are consistent with fixation of some ICG molecules on sites other than plasmatic proteins after injection. The process of fixation of ICG molecules on surface components or within the vascular endothelium could be due to a change in the microenvironment of some ICG molecules.

Animals↗
PubMed1998

[Diode laser-induced retinal thermal damage control with a liposome-dye system].

PURPOSE: To evaluate the feasibility of retinal thermal damage assessment in a rabbit eye model by using laser-induced release of liposome-encapsulated dye. METHODS: After anesthesia, thermosensitive liposomes (DSPC) loaded with 5,6-Carboxyfluorescein were injected intravenously to pigmented rabbits. Retinal photocoagulations were performed with a 810 nm diode laser (p = 100 to 400 mW, phi = 500 microns, 1s) (OcuLight, IRIS Medical Instruments Inc., USA). Fluorescence measurements in the area of the laser exposures were then made with a digitized angiograph (CF-60UVi, Canon-Europe, The Netherlands; OcuLab, Life Science Resources Ltd, England). RESULTS: Fluorescent spots were observed for power ranging from 100 +/- 5 mW to 400 +/- 5 mW. The fluorescence intensity increased linearly with the power and reached a plateau at 300 +/- 5 mW. The fluorescence intensity was correlated to the maximum temperature at the center of the laser spot with a linear increase from 42 +/- 3 degrees C to 65 +/- 3 degrees C. These results are consistent with our two previous studies with DSPC liposomes for temperature measurements in a tissue model and then in a vascular model. CONCLUSION: This preliminary study demonstrates the possibility of a laser-induced release of liposome-encapsulated dye for a quantification of diode laser induced thermal damage in ophthalmology. Such a method could be useful for a real-time monitoring of laser photocoagulation for conditions such as choroidal neovascular membranes when a precise thermal damage is required near the foveolar area.

Animals↗
PubMed1997

Thermal damage assessment of blood vessels in a hamster skin flap model by fluorescence measurement of a liposome-dye system.

BACKGROUND AND OBJECTIVES: The present study was undertaken to evaluate the feasibility of thermal damage assessment of blood vessels by using laser-induced release of liposome-encapsulated dye. STUDY DESIGN/MATERIALS AND METHODS: Experiments were performed in a hamster skin flap model. Laser irradiation was achieved with a 300 microm fiber connected to a 805 nm diode laser (power = 0.8W, spot diameter = 1.3 mm and pulse exposure time lasting from 1 to 6 s) after potentiation using a specific indocyanine green (ICG) formulation (water and oil emulsion). Liposomes-encapsulated carboxyfluorescein were prepared by the sonication procedure. Carboxyfluorescein (5,6-CF) was loaded at high concentration (100 mM) in order to quench its fluorescence. The measurements were performed after i.v. injection of DSPC liposomes (1.5 ml) and lasted 40 min. Fluorescence emission was measured with an ultra high sensitivity intensified camera. RESULTS: Three different shapes of fluorescent spots were identified depending on target (blood vessel or skin) and energy deposition in tissue: (i) intravascular fluorescence, (ii) transient low fluorescence circular spot, and (iii) persistent high intense fluorescence spot. These images are correlated with histological data. CONCLUSION: Real-time fluorescence imaging seems to be a good tool to estimate in a non-invasive manner the thermal damage induced by a diode laser combined with ICG potentiation.

Animals↗
PubMed1997

Selective laser photocoagulation of blood vessels in a hamster skin flap model using a specific ICG formulation.

BACKGROUND AND OBJECTIVE: The present study was undertaken to evaluate the selective laser photocoagulation of blood vessels in a hamster skin flap model using a specific indocyanine green (ICG) formulation. STUDY DESIGN/MATERIALS AND METHODS: Experiments were performed in a hamster skin flap model after injection of ICG in aqueous solution (ICGA), or after injection of a specific formulation of ICG (ICG in emulsion: ICGE). Laser irradiation was achieved 30 minutes after injection with a 300 microns fiber connected to a 805 nm diode laser (power = 0.8W, spot diameter = 1.3 mm and pulse exposure time lasting from 1 to 5 s). Macroscopic observation and acute histology were performed to compare the tissue effects obtained for each ICG formulation and to assess the selectivity of vessel damage. RESULTS: The ICGE clearance process was slowed down as compared to the ICGA process. After 30 minutes, the concentration of ICG in blood is higher (2.27 +/- 0.4, P < 0.003) for ICGE compared to ICGA. With ICGA, vessel coagulation required a minimum fluence of 240 J/cm2, which led to very significant skin damage. Conversely with ICGE, vessel coagulation required a fluence of 120 J/cm2. With such a fluence, no laser effect could be detected on the skin. Histological examination confirmed blood vessels coagulation in depth, whereas epidermis and dermis remained intact. CONCLUSION: The major restrictions of ICG in aqueous solution, which are the very-short half-life of ICG in blood and consequently the lack of selectivity in blood vessels after a few minutes, are alleviated when ICG is used in emulsion. ICG in emulsion increases the circulating half-life of ICG and moreover confines ICG in the vascular compartment. Thanks to this specific property, it is possible to obtain a selective vascular damage 30 minutes after injection.

Animals↗
PubMed1996

Fluorescence measurement of 805 nm laser-induced release of 5,6-CF from DSPC liposomes for real-time monitoring of temperature: an in vivo study in rat liver using indocyanine green potentiation.

BACKGROUND AND OBJECTIVE: This in vivo study examines the validity of using fluorescence measurements of laser-induced release of temperature-sensitive, liposome-encapsulated dye for real-time monitoring of temperature and for prediction of tissue thermal damage. STUDY DESIGN/MATERIALS AND METHODS: An in vivo study is performed in rat liver after i.v. injection of liposomes loaded with a fluorescent dye and i.v. injection of indocyanine green (ICG) for diode laser potentiation. Temperature-sensitive liposomes (DSPC: Di-Stearoyl-Phosphatidyl-Choline) are loaded with 5,6-carboxyfluorescein (5,6-CF). These liposomes (1.5 ml solution) and ICG (1.5 ml solution-5mg/kg) are injected in adult male wistar rats. Two hours later, the liver is exposed and irradiated with a 0.8 W diode laser using pulses lasting from 1-6s (fluence ranging from 16-98 J/cm2). Simultaneously, the fluorescence emission is analysed with an ultrahigh sensitivity intensified camera. RESULTS: The fluorescence intensity I(F) increases linearly from 18 J/cm2 up to 75 J/cm2. These fluences correspond to surface temperatures between 42 degrees C and 65 degrees C. The measurements appear to be highly reproducible. In this temperature range, the accuracy is +/- 3 degrees C. The maximum intensity is observed immediately after the laser is switched off. A decrease of the fluorescence intensity (27% in 20 minutes) is observed due to the 5,6-CF clearance. However, the ratio I(F)/I(BCK) (I(BCK): background fluorescence intensity) remains almost stable over this period of time and the determination of the temperature is still possible with good accuracy even 20 minutes after laser irradiation. CONCLUSION: Real-time temperature monitoring by using fluorescence measurement of laser-induced release of liposome-encapsulated dye is clearly demonstrated. This procedure could conceivably prove useful for controlling the thermal coagulation of biological tissues.

Animals↗
PubMed1996

Laser photocoagulation around the foci of toxoplasma retinochoroiditis: a descriptive statistical analysis of 35 patients with long-term follow-up.

Thirty-five patients with toxoplasma retinochoroiditis, receiving medical treatment and then treated with laser photocoagulation around the foci, were retrospectively evaluated for the risk of recurrence of the retinochoroiditis with a Kaplan-Meier representation. The recurrence rates with 95% symmetric confidence intervals were: at 1 year, 12.7 + or - 13%, at 2 years, 19.8 + or - 15%; at 3 years, 24.0 + or - 16%; at 4 years, 33.3 + or - 19%; at 5,6 and 7 years, 53.5 + or - 21%; at 8 and 9 years 66. 8 + or - 22%. With the data provided by our series, it is not possible to show the efficacy of laser photocoagulation as a prevention of recurrence in toxoplasma retinochoroiditis. Moreover, because of their heterogeneity, the recurrence rates from the literature cannot provide precise data for a comparison. Concerning the laser-induced thermal damage, the potential therapeutic mechanism of the laser procedure is discussed.

Adolescent↗
PubMed1996

[Control of photocoagulation intensity by thermo-induced release of a fluorescent marker encapsulated in liposomes: study of an in vivo vascular model].

PURPOSE: To evaluate the feasibility of thermal damage assessment of blood vessels by using laser-induced release of liposome-encapsulated dye. METHODS: A skin flap window model of aluminium was implanted on the loose skin on the back of adults Golden hamsters to expose skin blood vessels in vivo. Thermosensitive liposomes (DSPC) loaded with 5,6-Carboxyfluorescein were injected together with a specific Indocyanine green (ICG) formulation (O/W emulsion) in order to enhance diode laser absorption. Photocoagulations were then performed on the vessels with a diode laser (lambda = 810 nm, P = 0.8W, phi = 1.3 mm, 1 to 6s). Fluorescence measurements were realized with an ultra high sensitivity intensified camera (Hamamatsu Argus 50 imaging system). RESULTS: Two different fluorescence intensity curves corresponding to the variability of absorption of the targets were observed. Variability was related to the amount of ICG. For each curve, 3 zones were identified: (i) for fluences ranging from 60 +/- 20 J/cm2 to 110 +/- 20 J/cm2 a transient intravascular fluorescence was observed only for the loser pulses targeted on the vessels, (ii) for fluences ranging from 110 +/- 20 J/cm2 to 190 +/- 20 J/cm2 a permanent fluorescent spot limited to the vessel was observed for the laser pulses targeted on the vessels; for the laser pulses targeted on the skin a transient low fluorescence circular spot was observed. For this fluence range a selective photocoagulation of a vessel was performed. (iii) for fluences ranging from 190 +/- 20 J/cm2 to 300 +/- 20 J/cm2 persistent intense fluorescence spots were observed on both skin and vessels. This type of fluorescence was related to an overdosage. CONCLUSION: These results are in fair agreement with the data of the literature about liposomes and with the data we obtained in a previous study on a vascular model. This study demonstrates the interest of a laser-induced release of liposome-encapsulated dye for a real-time quantification of thermal damage. Such a method could be useful for laser photocoagulation in ophthalmology for indications such as choroidal neovessels where the production of a precise thermal damage is required.

Animals↗