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Morimura Y, Okada AA, Hayashi A, Fujioka S, Kawahara S, Hida T. Histological Effect and Protein Expression in Subthreshold TranspupillaryThermotherapy in Rabbit Eyes. Arch Ophthalmol. 2004;122(10):1510–1515. doi:10.1001/archopht.122.10.1510
To investigate the histological effect of subthreshold transpupillarythermotherapy (TTT) on the retina.
We performed TTT in normal pigmented rabbit eyes using an 810-nm diodelaser with spot size of 1.2 mm, power of 50 mW, and varying durations of 15,30, or 60 seconds. Four weeks later, fluorescein angiography was performed,and the enucleated eyes were examined by means of electron microscopy andimmunohistochemical staining.
Funduscopy immediately and at 4 weeks showed no discernable changesat TTT sites, and fluorescein angiography at 4 weeks showed no abnormalities.However, electron microscopy showed photoreceptor and retinal pigment epitheliumcell disruption, changes more prominent with longer durations of treatment.Immunohistochemical staining was positive for heat shock protein 60, heatshock protein 70, tumor necrosis factor α, and vascular cell adhesionmolecule 1 in the photoreceptors and retinal pigment epithelium at TTT sites.Untreated control eyes showed no staining.
Despite the absence of changes evident by funduscopy and fluoresceinangiography, TTT resulted in dose-dependent histological changes in photoreceptorsand retinal pigment epithelium. The induction of heat shock proteins, cytokines,and cell adhesion molecules may play a role in the tissue response to subthresholdTTT.
Unrecognized damage to the retina and retinal pigment epithelium maycontribute to visual loss in eyes that undergo subthreshold TTT.