Experience with the Pascal® photocoagulator: An analysis of over 1200 laser procedures with regard to parameter refinement.

Aim: To systematically refine and recommend parameter settings of spot size, power, and treatment duration using the Pascal® photocoagulator, a multi-spot, semi-automated, short-duration laser system. Materials and Methods: A retrospective consecutive series with 752 Caucasian eyes and 1242 laser procedures over two years were grouped into, (1) 374 macular focal / grid photocoagulation (FP), (2), 666 panretinal photocoagulation (PRP), and (3) 202 barrage photocoagulation (BP). Parameters for power, duration, spot number, and spot size were recorded for every group. Results: Power parameters for all groups showed a non-gaussian distribution; FP group, median 190 mW, range 100 – 950 mW, and PRP group, median 800 mW, range 100 – 2000 mW. On subgroup comparison, for similar spot size, as treatment duration decreased, the power required increased, albeit in a much lesser proportion than that given by energy = power × time. Most frequently used patterns were single spot (89% of cases) in FP, 5 × 5 box (72%) in PRP, and 2 × 2 box (78%) in BP. Spot diameters as high as ≈ 700 μm on retina were given in the PRP group. Single session PRP was attempted in six eyes with a median spot count of 3500. Conclusion: Overall, due to the small duration of its pulse, the Pascal® photocoagulator tends to use higher powers, although much lower cumulative energies, than those used in a conventional laser. The consequent lesser heat dissipation, especially lateral, can allow one to use relatively larger spot sizes and give more closely spaced burns, without incurring significant side effects.

Estudo experimental da aplicação retiniana do laser infravermelho via transescleral sob condições de baixa visibilidade / Transscleral infrared laser retinal photocoagulation experimental study under low visibility conditions

OBJETIVOS: Pesquisa experimental, com laser de diodo infravermelho, para estimar a segurança, a reprodutibilidade e a permeabilidade da parede ocular à sua atuação clínica, quando aplicado via transescleral, em condições de baixa visibilidade. MÉTODOS: Submetemos olhos de coelhos pigmentados da raça Nova Zelândia à fotocoagulação retiniana por laser de diodo infravermelho. No olho direito, realizamos fotocoagulação via transescleral sob parâmetros de potência e tempo pré-determinados clinicamente. No olho esquerdo, foram repetidos os mesmos valores da potência e tempo usados no olho direito, desta vez, via transpupilar. Imediatamente e após 2 meses, estudos clínicos baseados na retinografia e histopatológicos foram realizados. RESULTADOS: A permeabilidade da parede ocular, quando da aplicação do laser de diodo infravermelho via transescleral, variou entre 58,95 e 63,87 por cento. A média da permeabilidade da parede ocular a 300 mW (63,14 por cento) mostrou-se significativamente superior àquela da permeabilidade da parede ocular encontrada a 500 mW (59,11 por cento), (P<0,05). CONCLUSÕES: Este estudo sugere a existência da relação dose-resposta em relação aos parâmetros empregados na aplicação do laser de diodo infravermelho via transescleral, com permeabilidade da parede ocular mensurável e reprodutível. Nenhuma rotura, hemorragia ou descolamento da retina ou vítreo foi constatado aos exames subseqüentes às aplicações do laser de diodo infravermelho, o que torna o uso da fotocoagulação via transescleral, no modelo experimental, seguro, mesmo sob condições de baixa visibilidade dos meios.

PURPOSE: Retinal photocoagulation under poor visualization condition is often required. Transscleral infrared laser can be used as an alternative to regular transpupillary treatment. Based upon retinographic measurements, we proposed to estimate the reproducibility as well as ocular wall permeability rate for this treatment. Our primary goal was to evaluate whether this technique can deliver adequate photocoagulation at predetermined parameters without direct retinal visualization. METHODS: In New Zealand pigmented rabbits, optimal transscleral infrared diode laser settings were administered to the right eye. With the same parameters, transpupillary photocoagulation was repeated in the left eye. Retinographic and clinical examinations were performed immediately and two months later. RESULTS: Ocular wall permeability rate varied between 58.95 and 63.87 percent. Average permeability using a power of 300 mW (63.14 percent) was found to be higher than that encountered before its enhancement up to 500 mW (59.11 percent), (P<0.05). CONCLUSIONS: Setting parameters showed dose-response effect. No retinal hole or retinal detachment was noticed in any rabbit. Transscleral infrared photocoagulation appeared to be a reproducible and secure method in the experimental model.

Estabilidade visual na retinopatia diabética tratada por panfotocoagulação com laser / Visual stability in diabetic retinopathy treated by panretinal laser photocoagulation

OBJETIVO: Avaliar o efeito da "laserterapia" na acuidade visual em portadores de retinopatia diabética avançada e sem queixas visuais. MÉTODOS: Desenvolveu-se estudo observacional descritivo em portadores de retinopatia diabética avançada e sem queixas visuais, submetidos a panfotocoagulação retiniana com laser de argônio. Foi realizado exame oftalmológico completo. Entre o 3° e o 5° meses do tratamento, foi repetido o exame inicial. Para comparação da acuidade visual, entre período pré e pós-tratamento, foi utilizado o teste não-paramétrico de Wilcoxon. RESULTADOS: A amostra foi constituída por 44 pacientes, totalizando 67 olhos, sendo que 37 (55,2 por cento) apresentavam retinopatia diabética proliferativa e 30 (44,8 por cento) não proliferativa grave ou muito grave. A acuidade visual pré-tratamento variou de 0,5 a 1,0 (média de 0,83 ± 0,17). Não houve alteração estatisticamente significante na acuidade visual (p= 0,057) pré e pós-tratamento no período estudado. CONCLUSÃO: Houve estabilidade visual pós-tratamento com a panfotocoagulação, o que enfatiza a necessidade de intervenções em fases mais precoces da retinopatia diabética para preservar a função visual.

PURPOSE: To evaluate the effect of laser treatment in the visual acuity caused by advanced diabetic retinopathy without visual complaints. METHODS: A descriptive observational study was developed in advanced diabetic retinopathy patients not presenting visual complaints. The patients were submitted to argon laser panretinal photocoagulation after ophthalmological examination as well as retinography and retinal angiofluoresceinography. The same initial exams were repeated between third and fifth months after the treatment. The non-parametric Wilcoxon test was employed for statistical evaluation between the visual acuities before and after the treatment. RESULTS: The sample involved 67 eyes of 44 patients. Of these 67 eyes, 37 (55.2 percent) presented proliferative diabetic retinopathy and 30 (44.8 percent) showed severe and severe non proliferative diabetic retinopathy. The visual acuity before the treatment ranged from 0.5 to 1.0 (mean 0.81 ± 0.16). There was no significant statistical difference between the visual acuity (p= 0.057) before and after the treatment during the follow-up period of five months. CONCLUSION: The visual stability after panretinal argon laser photocoagulation indicated the need of this treatment in early phases of diabetic retinopathy in order to preserve the visual function.

technique for safe liver resection: the value of the argon beam coagulator

25 patients with primary hepatic tumors [20 patients with hepatocellular carcinoma and 5 patients with liver cell adenoma] were subjected to liver resection in one year. 2 patients were operated upon as an emergency due to bleeding tumors. A technique of liver resection with preliminary temporary vascular control of the corresponding branches, securing the hepatic veins with great attention to the caval ligament and liver transection using the argon beam coagulator is described with median loss of 450 ml. No mortality occurred in this series. The argon beam coagulators is highly recommended for safe and almost bloodless liver resection