[Correction of astigmatism by controlled bipolar scleral diathermy. Initial clinical experience]. / Korrektur des Astigmatismus durch kontrollierte bipolare Skleradiathermie. Erste klinische Erfahrungen.

Twelve eyes (9 patients with an average age of 35.3 years) were treated for astigmatism using temperature-directed bipolar scleral diathermy applied either directly to the limbus or 1 mm from it. The patients were then followed up for a period of 3 to 15 months. Using an electrode distance of 1 mm, diathermy was applied for 2.5-4.5 s until a scleral temperature of 60-65 degrees C was reached. A decrease in astigmatism from 9.5 dpt (s = 5.55) preoperatively to 1.7 dpt (s = 0.98) postoperatively was achieved as the final result. A further increase in astigmatism was noted up to the 3rd postoperative months of up to 5.4 dpt (s = 1.26). The refractive status achieved after this period proved to be stable. Retrogression of the initial effect varied according to the initial condition. Partial recurrence of astigmatism up to 5.16 dpt (s = 1.26) was observed within 6 months in cases of congenital astigmatism. In contrast, following IOL implantation. A further reduction of astigmatism up to 2.5 dpt 3 months postoperatively was noted after an initial reduction from 6.3 dpt (s = 0.25) preoperatively to 3.5 dpt (s = 1.08) postoperatively. Following perforating keratoplasty, one eye that had not been fitted with a contact lens showed a reduction in astigmatism of from 18 preoperatively to 1.2 dpt post-operatively after treatment. Nevertheless, an increase in astigmatism of up to 10.7 dpt was observed after 3 months. In cases with permanent contact lenses after keratoplasty, the situation was different.(ABSTRACT TRUNCATED AT 250 WORDS)

[Bipolar temperature controlled diathermy of the sclera for controlled refractive change of the cornea]. / Bipolare temperaturgesteuerte Diathermie der Sklera zur kontrollierten refraktiven Veränderung der Hornhaut.

A bipolar scleral diathermy unit measuring tissue temperature beneath the electrodes was used in 27 autopsy eyes to induce corneal curvature changes in order to modify corneal refraction. The optimal coagulation temperature was found to be between 65 degrees and 70 degrees C. The refractive effect was influenced by the distance of the electrodes (1 mm, 2 mm, 3 mm), their location ("limbal distance") and their position in reference to the limbus ("radial", "parallel"). The highest corneal curvature changes were observed with diathermy applied directly at the limbus or 1 mm distance from the limbus. The corneal meridian corresponding to the treated sclera regularly became significantly steeper and the untreated 90 degrees meridian flatter. Limbus parallel diathermy administered directly at the limbus showed a 0.91 mm increase in the corneal curvature with a 2 mm distance or a 0.34 mm increase with a 3 mm distance of both electrodes. Placing the electrodes radially or parallel of the limbus revealed greatest changes in corneal refraction using diathermy directly at the limbus or 1 mm distant from the limbus. The refractive effect decreased as the distance from the limbus increased. Corneal astigmatism could be decreased and increased in a quasi-controlled manner. Over-lapping diathermy offered the potential of gradually changing the corneal power. Histological sections showed that scleral collagen had only a superficial coagulation effect. Scleral diathermy offers great advantages in comparison to corneal incisions for the therapy of corneal astigmatism. Further investigations are in progress.