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July 1995

Experimental Transconjunctival Diode Laser Retinal Photocoagulation Through Silicone Scleral Exoplants

Author Affiliations

From the Department of Ophthalmology, Eye Institute, Medical College of Wisconsin, Milwaukee. The authors have no proprietary interest in the methods or products mentioned in this article.

Arch Ophthalmol. 1995;113(7):926-931. doi:10.1001/archopht.1995.01100070100032

Objective:  To study the feasibility of inducing a chorioretinal lesion under a previously placed scleral buckle by experimental transconjunctival diode laser photocoagulation.

Methods:  We performed transconjunctival diode laser photocoagulation in the peripheral retinas of seven pigmented rabbit eyes with a silicone exoplant (No. 42 band or No. 276 tire) and seven eyes without an exoplant. Each eye received burns with an intensity of grades 1 to 3 in different quadrants at varying power levels, with a 0.5-second duration and 650-μm spot size. Eyes were enucleated for histopathologic studies 1 day and 1 week after treatment.

Results:  Although the irradiance emitted through the No. 42 band and the No. 276 tire was attenuated by 17% and 23%, respectively, the range of threshold powers needed to produce grades 1 to 3 burns was similar between eyes with and without a silicone exoplant. At 1 day, full-thickness coagulative necrosis was observed in all lesions, except that the ganglion cell layer and inner nuclear layer were preserved in two of four grade 1 burns and the ganglion cell layer was intact in one of six grade 2 burns. Inner scleral changes were noted acutely in three of five grade 3 lesions. At 1 week, burns of all intensity grades showed a full-thickness atrophic chorioretinal lesion with inner scleral changes.

Conclusions:  Experimental transconjunctival diode laser photocoagulation through hard silicone elements reproducibly created a chorioretinal lesion with histopathologic findings similar to those of lesions obtained without these elements. Although retinal photocoagulative effects were prominent, inner scleral abnormalities were also observed histologically.

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