Temperature dependence of thermal damage to the sclera: exploring the heat tolerance of the sclera for transscleral thermotherapy.

Thermal damage to the human sclera in relation to temperature and duration of exposure was studied in order to determine the heat tolerance of the sclera with respect to transscleral thermotherapy of choroidal melanoma. Samples of human sclera were submerged in saline for 10 sec to 10 min at temperatures of 37-100 degrees C. The effects of heat on the shape, weight and size of the samples were studied. Thermal damage of scleral collagen was examined by polarized light microscopy (LM) and electron microscopy (EM). The sclera was embedded in epoxy resin and stained with toluidine blue for LM and with uranyl acetate and lead citrate for EM. Thermal damage of scleral collagen on polarized LM was graded on a five point scale. Scleral damage was visible on macroscopic examination and on LM and EM in sclera heated at 65 degrees C for 20 sec or longer, at 70 degrees C for 10 sec or longer, and at higher temperatures. A sigmoidal function was used to define the relation between temperature and changes in diameter, thickness, and weight of scleral samples. Using fitted functions, the threshold temperature for thermal damage was estimated to be 59-61 degrees C when samples were heated for 10 min, 62-63 degrees C when heated for 1 min, and 66-67 degrees C when heated for 10 sec; the threshold exposure time at 60 degrees C was estimated to be 7-12 min. These results indicate a temperature of 60 degrees C for 1 min is well tolerated by human donor sclera; information of in vivo studies is required to validate whether this setting can be used in transscleral thermotherapy (TSTT) for choroidal melanoma.

Transpupillary thermotherapy: results in 50 patients with choroidal melanoma.

OBJECTIVE: To evaluate the efficacy and safety of transpupillary thermotherapy in treating choroidal melanoma. METHODS AND PATIENTS: To perform transpupillary thermotherapy, infrared diode laser energy at 810 nm was used with a beam diameter of about 3 mm and 1-minute exposure time. All 50 patients had choroidal melanoma. We performed transpupillary thermotherapy in 21 tumors that had responded insufficiently to 800 Gy ruthenium 106 brachytherapy; it was combined with 800 Gy106Ru brachytherapy for 10 tumors greater than 5 mm in height and with 600 Gy for 19 tumors 5 mm or less in height. RESULTS: All but 1 tumor exhibited reduction in tumor height within a mean follow-up of 20.5 months (range, 6-49 months). In 41 eyes (82%), the tumor flattened completely. Visual acuity was 20/60 or better in 43 eyes (86%) before treatment and in 14 eyes (28%) at the last examination because of radiation vasculopathy. Neovascular glaucoma developed in 1 eye, and total retinal detachment developed in 2 eyes. Tumor recurrence was observed in 1 patient. CONCLUSIONS: Although long-term results are necessary to properly appraise this new therapy, transpupillary thermotherapy may be useful as a complementary modality to brachytherapy.

Transpupillary thermotherapy in choroidal melanomas.

OBJECTIVE: To determine safety and efficacy of transpupillary thermotherapy (TTT) as a new treatment for choroidal melanoma. METHODS AND PATIENTS: To perform TTT, diode laser energy at 810 nm was used with a beam diameter of 1.5 to 4.5 mm for a 1-minute exposure. All 12 patients had choroidal melanoma. Six had had insufficient response to ruthenium 106 (106Ru) brachytherapy. Three patients with tumors more than 5 mm in height were treated simultaneously with 106Ru and TTT. Three patients with juxtapapillary or macular tumors were treated by TTT only. RESULTS: All but one tumor exhibited a reduction of tumor height in a follow-up period of 3 to 14 months. Side effects were minimal. Severe visual loss occurred in two patients due to radiation retinopathy, in two patients whose foveas were included in the TTT area, and in one patient resulting from a serous retinal detachment that extended over the posterior pole. CONCLUSIONS: Treatment with TTT may be useful as a complementary modality to brachytherapy. A longer follow-up period is required for final evaluation.