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PubMed1988

[Endoscopic treatment of early upper gastrointestinal carcinoma--high-frequency-current polypectomy, laser, and microwave coagulation procedures].

The authors have been treating early gastric carcinoma endoscopically by high-frequency-current polypectomy since 1976, by microwave coagulation since 1982, and by laser coagulation since 1983. In order to achieve absolute curability of early carcinoma, we recommend that polypectomy be performed first, whenever possible. The reason for this is that the resected polypectomised tissue enables a decision to be made as to whether further treatment is necessary, after histopathological examination of the specimen. Otherwise, cases in which snaring is impossible, such as flat or depressed carcinomas of markedly small or large size, should be treated by microwave and/or laser coagulation. In total, we have experienced 92 lesions (83 cases) of early gastric carcinoma treated by all of above 3 methods, and we currently have 5 cases showing more than 5-year survival. Among these, type II a early carcinomas less than 10mm in diameter accounted for the majority; on the other hand, there were 11 type II c cases, also with tumors less than 10mm in diameter. Referring to our surgical data, type II c (without ulcer nor lymph node metastases) less than 5mm in size is limited to the mucosa in 100% of cases, and of 6-10mm in size in 85%. We therefore propose that type II c tumors less than 10mm in size should be treated endoscopically, as well as type II a tumors of the same size. In order to determine the depth of carcinomatous invasion, endoscopic ultrasonography (EUS) is effective. The diagnostic accuracy for Ul(-) early carcinoma is almost 100%, but for Ul(+) cases EUS is not so accurate. Further studies and improvements of EUS are thus needed.

Gastroscopy↗

PubMed1988

Endoscopic Nd-YAG laser therapy in upper gastrointestinal tract.

Forty-seven patients with gastrointestinal bleeding, benign tumor and malignancy were treated by YAG-laser therapy from 1980 to 1987. For active bleeding, laser coagulation was effective in inducing hemostasis. This therapy was also effective for the potential bleeding lesions. Benign sessile lesions such as polyp and adenoma were completely treated by laser vaporization. In cases with malignancy, the small-sized early gastric cancer (less than 15 mm in diameter) could be effectively treated. Among them, one case was followed up for as long as 82 months without any sign of recurrence. On the other hand, poor results were obtained in the cases suffering from early esophageal cancer due to incomplete laser irradiation resulting from the fear of penetration through the thin-walled esophageal mucosa. However, for the malignant stricture, the laser therapy was useful to relieve the lesion due to the regression of the tumor size. After the treatment, the patient was able to take meals orally. The above data demonstrate that the laser therapy is useful for the treatment of bleeding, sessile lesions, small-sized early gastric cancers and malignant strictures induced by advanced cancer.

Adenoma↗

PubMed1991

Long-term treatment effects in patients with bilateral retinoblastoma: ocular and mid-facial findings.

A total of 99 patients with bilateral retinoblastoma who had been treated between 1965 and 1982 were reexamined in April 1988 to study the late effects of treatment. Their median age at the follow-up visit in 1988 was 16 years (range, 6-27 years), and the median follow-up was 15 years (range, 6-26 years). All patients underwent a full eye examination, morphometric measurements of the mid-face and genetic counselling. Each eye or orbit and the corresponding side of the patient's mid-face were evaluated separately, resulting in 198 data sets from 99 individuals. Subjects were divided into four treatment groups according to whether photo- and cryo-coagulation, enucleation, radiation therapy or various combinations thereof were used. In all, 81 eyes had a visual acuity of greater than 0.4 (in 23 of these, however, only with low-vision aids). Within a dose range of 36-51 Gy, the location of the tumor (36%) or cataract (15%) were the main factors responsible for poor visual acuity, whereas radiation retinopathy and/or optic neuropathy occurred in only three cases. Cataracts were more frequently observed following orthovoltage as compared with megavoltage therapy (P = 0.012). A total of 72 eyes had been enucleated and had not received radiation therapy at any time. Cosmetic results (as measured by several parameters) in these cases were significantly better then those in 28 subjects who underwent combined radiation therapy and enucleation. As defined by various subjective as well as objective findings, mid-facial hypoplasia occurred significantly more often following orthovoltage as compared with megavoltage therapy.

Adolescent↗

PubMed2005

Transmission of retinal laser wavelengths through blood.

PURPOSE: Treatment of retinal and choroidal diseases may be influenced by overlying blood. We compared the penetration through blood of various laser wavelengths used in thermal photocoagulation, photodynamic therapy, and transpupillary thermotherapy. METHODS: Laser light of wavelengths 514 nm, 568 nm, 647 nm, 689 nm, and 810 nm was directed through normal saline (control), whole blood with a hematocrit of 40%, and serial dilutions of whole blood until a steady-state reading of laser power output was obtained. Laser power output was measured with an Orion Laser Power/Energy monitor (Ophir Optronics LTD). Laser power was measured in milliwatts and expressed as a percentage of control. RESULTS: Five hundred fourteen-nanometer and 568-nm laser wavelengths penetrated the least through all dilutions of blood tested (>60% attenuation through the highest dilution tested); 647-nm, 689-nm, and 810-nm laser wavelengths penetrated most effectively through blood but were still significantly attenuated ( approximately 46%, 49.6%, and 47.0% attenuation, respectively, at the highest dilution tested). CONCLUSIONS: The presence of hemorrhage may have a significant effect on the delivery of laser energy to underlying structures/tissue. This may affect parameters used in thermal and nonthermal laser treatment of ocular diseases such as choroidal neovascularization.

Adult↗

PubMedDate not supplied

Therapeutic colonoscopy.

Therapeutic colonoscopy has replaced or lessened to a significant degree the need or extent of traditional open surgical procedures. The common uses of therapeutic colonoscopy are hemostasis, resection and ablation of benign and malignant disease, decompression and recanalization of obstructed or dilated bowel, as well as foreign body extraction. Bleeding from arteriovenous and other vascular abnormalities can be controlled with 40% to 80% success rates using endoscopically delivered, monopolar, bipolar, or laser coagulation. The palliation of bleeding recurrent or inoperable colorectal cancer is achieved in up to 90% of patients. Virtually all pedunculated adenomas and most sessile adenomas are regularly removed colonoscopically, while large and recurrent villous adenomas in high risk individuals can be successfully managed by endoscopically delivered laser ablation techniques. Emergency colonoscopic reduction of sigmoid volvulus is performed pre-operatively and decompression of the dilated colon of non-obstructive colonic ileus is now regularly achieved. Colonic strictures have been dilated with a variety of techniques ranging from divulsion with through-the-scope balloon dilators to laser recanalization. Pre-operative endoscopic laser relief of tumor obstruction is employed to avoid preliminary or decompressing colostomy. Endoscopic laser debulking and recanalization of recurrent or inoperable cancer has been achieved with up to 80% success and various foreign bodies may be extracted from the colon with a number of endoscopic techniques. The morbidity of therapeutic colonoscopy has ranged from 1% to 2% for polypectomy to 11% for laser palliation of bleeding from advanced cancer, often with obstruction.

Adenoma↗

PubMed1992

Adriamycin absorption after Nd:YAG laser coagulation compared to electrosurgical resection of the bladder wall.

The toxicity of intravesical drugs used for the treatment of bladder cancer is increased by systemic absorption. Therefore, treatment is often delayed several weeks after transurethral resection until sufficient healing occurs. Since a neodymium:YAG laser causes tissue injury by thermal coagulation, we investigated differences in bladder permeability after laser treatment compared to TUR. Comparable 2.5 cm in diameter areas of tissue injury were created in the bladder of mongrel dogs either by Nd:YAG laser coagulation or transurethral electrocautery resection (TUR). Subsequently, 30 mg. of adriamycin were instilled intravesically. A control group consisted of animals receiving adriamycin alone. Blood was taken at 10, 30, 60, and 120 minutes after instillation and the serum concentration of adriamycin measured quantitatively by high performance liquid chromatography (HPLC) with fluorescence detection. The maximum serum ADM concentration during 120 minutes for the control group was 28.0 +/- 12.9 ng/ml compared to 38.9 +/- 4.8 for the laser group and 102.9 +/- 29.9 for TUR. The area under the curve was 35.1 +/- 10.2 ng x hours/ml for control, 43.5 +/- 3.9 for laser and 127.7 +/- 49.9 for TUR. Using a two-tailed Student's t test, the difference between the TUR and the laser group was significant (p less than 0.01). There was no difference between laser and control. These results suggest that laser treatment has minimal effect on the absorption of drugs from the bladder. The clinical practice of delaying intravesical therapy after TUR is verified but a similar policy may not be necessary after laser treatment.

Administration, Intravesical↗

PubMed1990

Contact transscleral laser cyclocoagulation in glaucoma.

A new way to treat glaucoma by laser coagulation of the ciliary body was developed. The laser beam is channeled to the eye through the fiberoptic system. The tip of the fiberoptic probe is placed in direct contact with the surface of the eye to be treated. The technical equipment developed for contact transscleral laser cyclocoagulation is simple, practical, and easy to use. The method was investigated experimentally (on animals and on human eyes to be enucleated) and tried in clinical practice. Only patients facing glaucoma surgery (on whom all other methods of conservative therapy failed) were selected for this kind of treatment. The immediate hypotensive effect was approximately 13 mmHg during the first 24 hours; then there was a gradual elevation of the tension, reducing the initial effect on average by 30%. This method has definite advantages over surgical cyclocoagulation as far as safety and simplicity are concerned. The use of contact fiberoptic systems may open up new possibilities in other fields of laser treatment of glaucoma, including techniques to channel the laser beam to the structures of the anterior chamber angle.

Animals↗

PubMed1989

[Pneumatic retinopexy. Analysis of the first 20 cases].

The author analyses the results of 20 eyes with retinal detachment (RD) treated by the Pneumatic Retinopexy procedure (intra-vitreal gas injection and coagulation of the retinal breaks). The selected RD's were caused by peripheral retinal breaks located in the superior 270 degrees of the retina and of less than 45 degrees width. Proliferative vitreoretinopathy (PVR) was grade C1 or less. In 15% of the cases, the RD was a recurrence after previous surgery and 10% of the eyes were aphakic. The anatomic success rate was 95% both initially and after 6 months follow up. Three (15%) recurrences of RD were noted within the first postoperative month. One of these was caused by massive PVR. A secondary buckling was proposed when important vitreoretinal traction was noted after pneumatic reattachment. No case of subretinal gas, macular pucker or infection was seen. Postoperative visual acuity greater than or equal to 4/10 was obtained in 80% of the 10 macular off cases. In this limited series, the anatomic success rate of the Pneumatic Retinopexy procedure was similar to that of classical RD surgery, but functional results proved better. If these results are confirmed by larger series, Pneumatic Retinopexy could become the choice procedure in primary repair of uncomplicated rhegmatogenous RD's.

Aged↗

PubMed2003

Implementation of a practical model for light and heat distribution using laser-induced thermotherapy near to a large vessel.

This paper introduces a simulation model for light and heat transport in tissues including perfusion effects. The model enables an efficient simulation of the damaged zone induced with an optical fibre for laser interstitial thermotherapy (LITT). It is designed specially for, but not limited to, tissue ablation in the neck region near to vessels. We describe in detail the effects of the rise in temperature caused by the absorption of light in tissue, using the heat equation and including the cooling effects of flow in vessels and of microperfusion in tissue in order to determine the extent of thermal damage. The extent of the necrosis zone is calculated with a damage function at each point of a finite element method (FEM) mesh. The FEM mesh is implemented with FEMLAB 2.3 as an add-on for finite element modelling for Matlab 6.5. LITT for tumour ablation in liver and some other anatomical regions is a well-known and established method (Bundesärztekammer und Kassenärztliche Bundesvereinigung 2002 Assessment der Bundesärztekammer und der Kassenärztlichen Bundesvereinigung, Köln). Investigations of treatments using LITT in the neck region are still in progress. We propose a refined model to validate the LITT method in the future in another anatomic region, e.g., in the highly sensitive region of the neck. Our calculations show that in order to induce a lesion with a maximum diameter of about 1 cm near to a large vessel, an application time between 3 and 4 min is needed using a laser power of about 10 W with a Nd:YAG 1064 nm radiation wavelength.

Body Temperature↗

PubMed1983

Isolation and functional characterization of the active light chain of activated human blood coagulation factor XI.

Human blood coagulation Factor XIa was reduced and alkylated under mild conditions. The mixture containing alkylated heavy and light chains was subjected to affinity chromatography on high Mr kininogen-Sepharose. Alkylation experiments using [14C]iodoacetamide showed that a single disulfide bridge between the light and heavy chains was broken to release the light chain. The alkylated light chain (Mr = 35,000) did not bind to high Mr kininogen-Sepharose while the heavy chain (Mr = 48,000), like Factors XI and XIa, bound with high affinity. The isolated light chain retained the specific amidolytic activity of native Factor XIa against the oligopeptide substrate, pyroGlu-Pro-Arg-p-nitroanilide. Km and kcat values for this substrate were 0.56 mM and 350 s-1 for both Factor XIa and its light chain, and the amidolytic assay was not affected by CaCl2. However, in clotting assays using Factor XI-deficient plasma in the presence of kaolin, the light chain was only 1% as active as native Factor XIa. Human coagulation Factor IX was purified and labeled with sodium [3H]borohydride on its carbohydrate moieties. When this radiolabeled Factor IX was mixed with Factor XIa, an excellent correlation was observed between the appearance of Factor IXa clotting activity and tritiated activation peptide that was soluble in cold trichloroacetic acid. Factor XIa in the presence of 5 mM CaCl2 activated 3H-Factor IX 600 times faster than Factor XIa in the presence of EDTA. In the absence of calcium, Factor XIa and its light chain were equally active in activating 3H-Factor IX. In contrast to Factor XIa, the light chain in this reaction was inhibited by calcium ions such that, in the presence of 5 mM CaCl2, Factor XIa was 2000 times more effective than its light chain. Neither phospholipid nor high Mr kininogen and kaolin affected the activity of Factor XIa or its light chain in the activation of 3H-Factor IX. These observations show that the light chain region of Factor XIa contains the entire enzymatic active site. The heavy chain region contains the high affinity binding site for high Mr kininogen. Furthermore the heavy chain region of Factor XIa plays a major role in the calcium-dependent mechanisms that contribute to the activation of Factor IX.

Acetamides↗

PubMed1991

[Histopathological study on the monkey retina and choroid by diode laser endophotocoagulation].

The fundi of three cynomolgus monkeys were coagulated using a diode laser endophotocoagulator. The histopathological changes of the retina and the choroid were investigated periodically up to 3 months. The damage of the retina extended into the outer plexiform layer following mild burn, into the inner nuclear layer with moderate burn and into the nerve fiber layer on severe burn. The pigment epithelium proliferated with multiple layer cells 1-3 months after the irradiation. The choriocapillaries were obstructed, regardless of the degree of burns, immediately after the irradiation, but recanaliculation was observed at the mild and moderate burns 1-3 months after the irradiation. The effects on the choroid were localized to the inner layer following mild burn, but the damage extended into the outer layer with moderate burns. Following severe burns obstruction of the medium size vessels was observed. The fibrous changes of the choroid increased in accordance with the degree of the burn. The damaged melanophore in the choroid recovered considerably 1 month after the mild burn. On the other hand, many macrophages still remained in moderate and severe burn lesions. These results suggested that diode laser photocoagulation might be effective for the treatment of the choroidal diseases rather than retinal diseases, because diode laser photocoagulation produced the considerable change in the choroid as well as in the retina.

Animals↗

PubMed1993

[Non-hysteroscopic thermodestruction of the endometrium using radio waves in the treatment of menorrhagia].

OBJECTIVE: To test non-hysteroscopic thermodestruction of the endometrium for safety and efficiency. DESIGN: Prospective pilot study from February 1991 to July 1992. SETTING: University Hospital Nijmegen. PATIENTS AND METHOD: There were 68 patients aged 30-55 years with menorrhagia, who did not want children but wished to retain the uterus. There were two patients with a subserous myoma but with a normal uterine cavity. Patients with hypergonadotropism, a markedly enlarged uterus, abnormalities at cytological examination of the cervix, adnexal lesions, prolapse, intrauterine lesions and coagulation disorders were excluded. By way of preparation, danazol was administered for 4 weeks before the intervention (36 patients). Three patients with side effects were given lynestrenol. From January 1992, an LH-RH analogue was administered (29 patients) for 6 weeks prior to the intervention or in the patients with a subserous myoma for 12 weeks. Thermodestruction of the endometrium by means of radio waves was carried out according to a standard protocol under general or epidural spinal anaesthesia. The intracavitary temperature measured was 62-65 degrees C, mean duration of the treatment 20 minutes. RESULTS: The patients were discharged 10-24 hours after the intervention. A non-disturbing watery discharge of 3-6 weeks' duration was reported. Normal activities were resumed after one week. Success (duration of follow-up 3-21 months) was defined as amenorrhoea (6 patients; 9%) or a markedly reduced menstruation or duration of menstruation (48 patients; 70%). Six patients (9%) reported no improvement and of eight patients (12%) with slight, unsatisfactory improvement three were treated again, with success (4%). During the trial period the method was further adjusted and perfected. There were no complications. CONCLUSION: This preliminary experience shows that thermodestruction with radio waves is simple, safe and efficient.

Adult↗

PubMed1999

[Vitreoretinal surgery in the treatment of neovascular glaucoma].

PURPOSE: Neovascular glaucoma develops on a background of ischemic ocular pathologies, such as diabetic eye diseases or central retinal vein occlusion. Development of neovascular membranes in the chamber angle leads to elevated intraocular pressure. Since treatment by cyclodestructive therapy or drainage surgery often fails, we have examined intense antiproliferative surgery as a treatment for advanced neovascular glaucoma. PATIENTS AND METHODS: Thirty-two patients with neovascular glaucoma subsequent to central vein occlusion or advanced diabetic retinopathy underwent antiproliferative surgery, which comprised vitrectomy, panretinal laser treatment and direct laser coagulation of the ciliary processes, followed by silicone oil tamponade. Patients were followed for a minimum of 1 year and as long as 3 years. RESULTS: After one week following surgery the intraocular pressure (IOP) was normal, ranging from 8 to 21 mm#Hg, in 52% (15/29 eyes), after 3 months the IOP was normal in 50% (16/32 eyes), after 6 months the IOP was normal in 59% (16/27 eyes) and after 1 year the IOP was normal in 72% (18/25 eyes). Of the 10 eyes that lost all sight after the surgery, 7 eyes had a history of central vein occlusion. Hypotony was observed in 6% (2/32) of the eyes 3 months following surgery; after 6 months hypotony was present in 15% (4/27) of the eyes and after 1 year hypotony was present in 12% (3/25) of the eyes. CONCLUSIONS: The theoretical premise of our surgical intervention (antiproliferative surgery) is based on the assumption that laser treatment interrupts the self enhancing pathway of retinal ischemia, release of proliferative factors and increase in intraocular pressure. The silicone oil endotamponade prevents postoperative complications and supports the rapid regression of rubeosis iridis by separating the anterior from the posterior segment.

Aged↗

PubMed2000

[Assessment of colorectal cancer patients exhibiting bilobular multiple hepatic metastases].

We assessed 23 patients who underwent surgical therapy of hepatectomy or microwave coagulation therapy (MCT) for bilobular multiple hepatic metastatic foci following curative resection of the primary lesion of colorectal cancer. Hepatectomy was the first surgical therapy for 10 patients, and 6 of them received combined intra-arterial chemotherapy. All 13 patients in the MCT group received intra-arterial chemotherapy, and 8 of them underwent combined hepatectomy. The two-year survival rate of the hepatectomy group, classified according to the first surgical therapy, was 40% against 52% in the MCT group. In comparison with the H2 (2-5 foci) patients in the hepatectomy group, there were 7 H2 patients in the MCT group, and the two-year survival rate of these 7 patients was 50%. No significant difference was observed between hepatectomy and the MCT as the first surgical therapy. The survival rates of the 5 patients who received treatment for recurrence after the first surgery and of the 18 patients without any recurrence treatment were 80% and 40%, respectively. No significant difference existed between the two groups, but a p value of 0.06 was noted. MCT was considered to be useful local therapy for cancer as the first therapy and as a therapy following recurrence.

Antineoplastic Agents↗

PubMed1991

Histochemical evaluation of the coagulation depth after argon laser impact on a port-wine stain.

A two-step excisional treatment of a port-wine stain (PWS) on the back of a 43-yr-old female patient was performed. Immediately before the first surgical treatment, two corresponding series of argon laser impacts were performed, each on one PWS half. Different laser parameters with irradiances ranging from 95 to 382 W/cm2 and energy fluences ranging from 19 to 114,6 J/cm2 were used. Laser spots on the first part ot be excised were biopsied 10 min after laser treatment and prepared for histochemical analysis by staining with nitro blue tetrazolium chloride (NBTC). Reduction of this redox dye by nicotinamide adenine dinucleotide diaphorase (NADH-diaphorase) leads on frozen tissue sections to an intense blue precipitate. The activity of NADH-diaphorase subsides immediately upon cell damage. All vital epidermal and dermal cells presented a dense blue granular pigment in their cytoplasm, sparing the nuclei. Laser induced arc-shaped epidermal and dermal necrosis did not stain, showing a clear demarcation from surrounding vital tissue. The depth of the thermal injury ranged from 0.28 to 0.45 mm; it did not correlate with the chosen fluences. With these penetration depths, the vast majority of PWS vessels was affected. Assessment of the remaining part of the PWS 8 months later yielded blanching of all laser-treated areas. With the NBTC method, an accurate definition of laser-induced tissue damage is feasible. It could be shown that the exposure time is the most relevant parameter influencing the penetration depth.

Adult↗

PubMed1996

CO2 and Nd:YAG laser-induced pulmonary parenchymal lung injury in a rabbit model.

Laser exposure of the pulmonary parenchyma during treatment of emphysema and other clinical indications causes acute lung injury. Animal investigations are needed to understand and control laser-induced lung injury. We hypothesized that lung injury is deeper from Nd:YAG laser exposures than CO2 exposures because of deeper penetration of Nd:YAG wavelength light. We compared the temporal evolution of histologic injury in rabbits resulting from continuous mode shallow CO2 and Nd:YAG laser pulmonary parenchymal exposures applied in rabbits. Forty-six New Zealand white (NZW) rabbits underwent treatment with CO2 laser (n=18), Nd:YAG laser (n=18), or sham thoracotomy control (n=10) to the visceral pleural surface using 1 min of exposure (5 watts, defocused to 70 W/cm2 power density for both lasers). Animals were killed at 0, 4, 7, 21, and 49 d after exposure. Lung injury, similar to that seen clinically in humans, developed in all laser-treated animals. Injury progressed from ischemia and vascular congestion, to edema and necrosis, followed by pleural and parenchymal fibrosis. The acute injury was qualitatively distinct and slightly deeper in CO2 than Nd:YAG-treated animals (p<0.02) despite the shallower depth of penetration of the CO2 laser. These findings may imply that higher absorption coefficient for CO2 laser energy results in greater focal temperatures and injury in the areas of direct exposure, and suggest that Nd:YAG laser exposure at these settings may cause shallower injury than CO2 lasers in humans undergoing clinical treatment.

Absorption↗

PubMed1982

Comparison of argon laser photocoagulation and bipolar electrocoagulation for endoscopic hemostasis in the canine colon.

Severe bleeding from the lower gastrointestinal tract commonly occurs from mucosal lesions such as angiodysplasia and less often from acute ulcerations. Endoscopic coagulation of such lesions is now feasible. Our purpose was to compare the efficacy and histologic injury of bipolar electrocoagulation and argon laser photocoagulation applied at laparotomy in the canine colon. After right colotomy and heparinization in adult mongrel dogs, bleeding standard ulcers were randomly assigned to treatment or control. The colonic ulcers randomized to each group were not significantly different in size or bleeding rate. Efficacy of treatment was evaluated acutely. Adjacent normal mucosa was treated with the same modality as the ulcer to simulate treatment of a mucosal lesion. The same total exposure time (argon laser photocoagulation) or number of pulses (bipolar electrocoagulation) was used for these paired treatments. Gross and histologic injury were determined after 7 days. Both argon laser photocoagulation and bipolar electrocoagulation were uniformly effective in controlling bleeding from standard colonic ulcers and the incidence of full thickness injury was similar, 33%-48%. The histologic damage seen with normal mucosa treatment was consistently less than with standard ulcers for all treatment groups. The difference is easily explained by the reduction in colonic wall thickness of about 50% with creation of standard ulcers. In our opinion, argon laser photocoagulation and bipolar electrocoagulation are safe enough to be used in clinical trials for control of colonic bleeding from mucosal lesions but not acute colonic ulcers.

Animals↗

PubMed2005

Comparison of laser beam intensity profiles produced by photodynamic therapy (PDT) and transpupillary thermotherapy (TTT) lasers.

BACKGROUND AND OBJECTIVES: For photodynamic therapy (PDT) or transpupillary thermotherapy (TTT) lasers, long irradiation time (typically 1 minute or longer) is used and a large area of retina is treated. Consequently, the power stability but also the light distribution within the laser beam plays a major role. This study aimed to evaluate beam intensity profiles produced by several PDT and TTT lasers. STUDY DESIGN/MATERIALS AND METHODS: A beam profile analyzer (Cohu 4812 camera connected to a LPA-300PC, Spiricon, Logan, UT) was used to compare the beam profiles of PDT lasers: OPAL (Lumenis, USA); ACTIVIS (Quantel Medical, France), VISULAS (Zeiss, Germany). Spots of 2, 3, 4, and 5 mm were tested with each laser. Similarly, TTT lasers: OCULIGHT SLx (Iridex, CA) and IRIDIS trade mark (Quantel Medical, France) were evaluated with 2 and 3 mm spot diameter and power ranging from 200 to 1,000 mW. RESULTS: PDT lasers: OPAL had a "top hat" and homogeneous profile whatever the spot size. Numerous micro-spikes and micro-nadirs of power were observed with the ACTIVIS and the VISULAS. TTT lasers: for the IRIDIS the beam shape was rather gaussian, but the homogeneity was reduced by micro-spikes of power. With the OCULIGHT Slx the beam shape was rather top hat and only few micro-spikes or micro-nadirs of power could be disclosed. DISCUSSION: The literature tends to prove that the shape and homogeneity of the beam profile could play a role on the efficacy of the treatment. CONCLUSION: Since PDT and TTT lasers display different beam profiles, this parameter should be carefully evaluated when performing clinical evaluations of PDT or TTT treatments.

Laser Coagulation↗