Comparison of techniques for transscleral diode photocoagulation in the rabbit

Morphological Evaluation of Transscleral Laser Retinopexy in Rabbits: Comparison of Optical Coherence Tomography and Histologic Examinations

Transscleral retinopexy is a preventive technique used against retinal detachment. Fundus examination can allow the monitoring of morphological retinal changes in the progression of photocoagulation lesions, without offering details on the morphological changes by the retinal lesion. The aim of the study was to assess the progression of photocoagulation lesions induced by transscleral retinopexy (840 nm diode laser), by comparing the optical coherence tomography (OCT) and histological images over a period of six weeks on eight pigmented New Zealand healthy rabbits (four males and four females; n = 16 eyes). All rabbits underwent transscleral retinopexy on their left eye on day 0 (D0). Measurements of the photocoagulation lesions were obtained in vivo on D0, D7, D15, D21, and D42 by acquiring OCT images of both eyes from all rabbits. On D1, D7, D21, and D42, two rabbits were euthanized, and their eyes were enucleated. A significant effect by time on the decrease in the central retinal thickness of the photocoagulation lesion was observed from D1 to D7 (p = 0.001); however, no such effect was observed on the horizontal length ((HL) p = 0.584) of the lesion surface. The reliability between the OCT and histological measurements, which were evaluated using intraclass correlation coefficients, was excellent for measuring the retinal thickness at the center (ICC = 0.91, p < 0.001), moderate for the right side of the retinal lesions (ICC = 0.72, p = 0.006), and not significant for the left side and HL (p = 0.055 and 0.500, respectively). The morphological changes observed in the OCT and histopathological images of the photocoagulation lesions were qualitatively described over time. OCT is an effective tool for monitoring changes in photocoagulation lesions. Some measurements and qualitative changes showed an adequate correlation between the OCT and histological findings.

Transscleral thermotherapy with laser-induced and conductive heating in hamster Greene melanoma

The purpose of this study was to investigate the cytotoxic effect of heat as induced by transscleral thermotherapy (TSTT), which may be of interest in the treatment of patients with choroidal melanoma. The aim of TSTT is to heat both the sclera and the tumor up to a cytotoxic temperature of about 60 degrees C. TSTT was performed in hamsters with subcutaneously implanted Greene melanoma covered by a specimen of human donor sclera of thickness 0.5, 0.7 or 0.9 mm. A newly developed applicator, which combines conductive episcleral heating at 60 degrees C with laser-induced heating, was used at laser powers ranging from 500 to 1500 mW delivered by an 810 nm diode laser, beam diameter 3 mm, and exposure time 1 min. Temperatures were measured at the scleral surface and at the sclera-tumor interface. The extent of tumor necrosis was examined by light microscopy and the sclera was examined by polarized light microscopy. Maximal depth of tumor necrosis without scleral damage was 4.4 (SD 1.5) mm. The temperature at the scleral surface after TSTT was 58.8 (SD 2.4) degrees C. The temperature at the sclera-tumor interface ranged from 56.4 (SD 3.7) degrees C at 500 mW to 65.3 (SD 4.4) degrees C at 1250 mW laser power. Structural changes to the scleral collagen started to develop at 1250 mW. TSTT with combined laser-induced and conductive heating caused cytotoxic temperatures in the tumor and the sclera, which were well tolerated by the scleral collagen.

Diode laser transscleral retinopexy in rhegmatogenous retinal detachment surgery

PURPOSE

To evaluate the safety and efficacy of transscleral diode laser for retinopexy in rhegmatogenous retinal detachment surgery.

METHODS

Conventional retinal detachment surgery with transscleral diode laser retinopexy was performed on 52 eyes of 52 patients (22 female, 30 male), aged from 12 to 74 years (mean 51 + 4.1).

RESULTS

Of the 52 eyes 36 (69%) were reattached in a single operation and adequate chorioretinal scars were achieved in 34 of them. Additional transpupillary laser photocoagulation was performed in two cases in the postoperative period. Retinal re-attachment was achieved with exoplant revision and transscleral laser retinopexy in six cases (12%). Ten cases (19%) with severe PVR were reattached with vitreoretinal surgery.

CONCLUSIONS

Transscleral diode laser retinopexy was an effective and safe method, with accurate lesion location, concurrent permanent laser marks on the retina, and easy transmission through the extraocular muscles and solid buckling elements. Minor complications were minimized by gaining experience with the technique.