Changes in adhesive force between the retina and the retinal pigment epithelium by laser photocoagulation in rabbits

A closed eyeball model was designed to estimate the chorioretinal adhesion of the laser-photocoagulated region. We used it to measure the duration of development of retinal detachment during vitrectomy before and after killing the test rabbits. During testing, negative pressure was applied into the vitreous cavity of the pigmented rabbits. Laser burns were produced in the posterior retina by exposure to an argon blue-green laser beam with a focus diameter of 200 microns of 0.1 to 0.2 second duration and 150 to 250 mW intensity. One hour and one, two, five, seven and fourteen days following laser photocoagulation, vitrectomy was done with a cutting rate of 500 per minute, aspiration pressure of 50 mmHg and infusion pressure of 55.2 mmHg. After core vitrectomy, the rabbit was killed with an intravenous bolus of 100 mg sodium pentobarbital solution. After killing the rabbit, the vitreous cavity was continuously aspirated under the pressure of 25 mmHg while the infusion was stopped. The changes of the fundus, especially development of retinal detachment, were observed in the laser-treated and untreated regions before and after killing the rabbit. When retinal detachment was noted anywhere before killing the rabbit, this postmortem change was not observed. One hour following laser photocoagulation, the laser-treated retina was detached during core vitrectomy before killing the rabbit, and the untreated area was not detached. One day following photocoagulation, the retina was intact before killing the rabbit. After killing the rabbit, the laser-treated retina was detached in four minutes and the untreated retina in 18 minutes postmortem.

Short-term Observation of Histological Changes on the Rabbit Retina after Endocryopexy

The aim of this study was to evaluate the histopathologic changes of the pigmented rabbit ratina after endocryopexy. We investigated the differences or similarity among endocryopexy, transscleral cryopexy and laser phocoagulation. Their ultrastructural changes were observed with light and electron microscope. The results were as follows; 1. The first day after endocryopexy, we observed rupture of the internal limiting membrane, breakdown the inner and outer retina, separation of intercellular gap junction of pigment epithelial cells, and accumulation of exudation within subretinal space. 2. In the 8th days, there are mull iplication of retinal pigment epithelial cell layer and development of basal infolding. 3. The present study suggested that effects of endocryopexy on the retina to cause chorioretinal adhesion was similar to transscleral cryopexy or laser photocoagulation However it should be operated on the premise that in requires technical skill for the purpose of clinical application.

Contact Transscleral Continuous-wave Nd:YAG Laser Retinopexy: Comparison with Cryoretinopexy

We studied clinical applicability of the contact transscleral retinopexy using the continuous-wave Nd:YAG (CW-YAG) laser. CW-YAG laser photocoagulation was done over sclera through contact probe in the pigmented rabbit eyes. Cryoretinopexy was also done and their morphologic findings were compared. Acute lesions produced with the laser photocoagulation were noted to have the characteristic white-colored distinct depigmentation. Its microscopic findings were oharacterized by choroidal necrosis, disruption of Bruch's membrane, dispersion of retinal pigment epithelial cells, and disorganization of sensory retina. Acute lesions after the cryoretinopexy were much more broader in its area and showed slight tanslucent retinal edema. Its microscopic findings showed relatively well-preserved choroid including Bruch's membrane. These data demonstrated that the contact transscleral CW-YAG laser retinopexy is capable of inducing more localized, stronger chorioretinal adhesion than the cryoretinopexy.

Histopathologic Findings of Chorioretinal Adhesion After Photocoagulation of the Thretinal Break

Adult albino rabbits were used in this study. The retina was treated with laser photocoagulation around the retinal break. The histopathologic findings were evaluated with light and electron microscopes to determine how quickly chorioretinal adhesion was produced after photocoagulation. Adhesion between the rod and cone layer and the pigment epithelium appeared within 1 hour after photocoagulation, probably due to direct burn effect of the laser. A scar tissue appeared in the chorioretinal lesion 5 days after photocoagulation, derived from the proteinaceous coagulum and accompanying fibrosis.