Potential Therapeutic Applications of LTD

POTENTIAL THERAPEUTIC APPLICATIONS OF LTD Laser-Targeted Photo-Occlusion 

The limitations of PDT are possibly the result of needing to keep the dose of the photosensitizer and the irradiating light low enough to avoid collateral damage. The low dose is most likely sufficient to cause thrombus formation but insufficient to achieve the desired effect of vascular wall damage. Such an occlusion may thus be temporary, due to dissolution of the clot and vessel re-canalization. 

Extensive experiments in nonhuman primates, rabbits, rats, and dogs have demonstrated that LTO possesses the following additional features  

LTO has been shown to be relatively free of damage to the normal vessels and to the RPE (16,17). CNV lesions were created in a rat model, some of which were treated with LTO and some left untreated. Light and electron microscopy showed that three of four untreated CNVs had more than one lumen open and no occlusion, and that one CNY had spontaneously occluded vessels (18). Microscopic examination of eight LTO-treated CNVs showed six with no CNV, one with partial occlusion and one without occlusion. LTO-treated areas next to the CNVs showed normal photoreceptors, RPE, Bruch s membrane, and choriocapillaris (Fig. 3) (15). The preservation of the RPE may be particularly important in AMD, because it is already abnormal and may be more sensitive to additional injury. The intact nature of Bruch s membrane is also important in AMD because breaks are believed to be associated with further proliferation of the CNV into the subretinal space. 

LTO promises to offer effective treatment to both kinds of CNV ( classic as well as occult ), as action is based on the presence of photosensitizer in the CNV at the time of irradiation. Large CNVs would also be amenable to treatment for the same reason (4). 

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