Dose-related structural effects of photodynamic therapy on choroidal and retinal structures of human eyes

Abstract

PDT with verteporfin at a dosage used clinically induces selective occlusion of the physiological choriocapillaris without affecting deeper choroidal, retinal, and optic nerve vessels or the overlying retinal pigment epithelium and neurosensory retina. The main mechanism of action appears to be vascular thrombosis induced by cytotoxic damage of endothelial cells and platelet activation. An increase in light dose enhances the occlusive effect with thrombosis within deeper choroidal layers and damage to the retinal pigment epithelium. However, photoreceptors remained intact at all light doses used.

Follow-up after intravitreal triamcinolone acetonide for exudative age-related macular degeneration

“…Although randomized trials comparing an intravitreal triamcinolone acetonide monotherapy with a combination of intravitreal triamcinolone acetonide and photodynamic therapy for the treatment of exudative age-related macular degeneration have not been published yet, and although photodynamic therapy may lead to a collateral tissue damage in the macula in contrast to intravitreal triamcinolone acetonide, 36 the present study in combination with results published in the literature may suggest that the combined treatment consisting of verteporfin photodynamic therapy and intravitreal triamcinolone acetonide may be superior to the intravitreal triamcinolone acetonide monotherapy.…”

Half-dose vs one-third-dose photodynamic therapy for chronic central serous chorioretinopathy

“…Previous studies have shown that cytotoxicity and vascular damage associated with PDT are dose dependent. 25,26 In this prospective clinical trial, we compared the efficacy and safety of 1/2 PDT with those of 1/3 PDT for chronic CSC. Zhao et al 20 conducted PDT with verteporfin at 30% of the conventional dosage in 8 eyes with acute CSC, and all eyes (100%) had resolution of SRF.…”

Platelets, photosensitizers, and PDT

“…This is confirmed by many experimental studies. E.g., an electron microscopic study on the Verteporfin PDT effects on choroidal and retinal structures in the hum eye clearly showed swelling, shrinking and fragmentation of the choriocapillary endothelium, basement detachment, and ultimately thrombus formation [101]. Similar results were obtained with a liposomal formulation of a (phthalocyaninato)zinc(II) derivative [102].…”