Asrani S, Zeimer R
Johns Hopkins University School of Medicine, Wilmer Ophthalmological Institute, Baltimore, MD 21287-9131, USA.
Br J Ophthalmol. 1995 Aug;79(8):766-70. doi: 10.1136/bjo.79.8.766.
AIMS/BACKGROUND: Neovascularisation occurs in many major ocular diseases such as diabetes, age-related macular degeneration, and sickle cell disease. Laser photocoagulation is typically used to obliterate the vessels but it also causes severe damage to adjacent normal tissues. This is a very significant limitation especially in the treatment of choroidal neovascularisation which often covers large areas of the posterior pole and the fovea. A method, laser targeted delivery, has been developed capable of releasing drugs locally and non-invasively in the choroidal or retinal vasculature. This method could be used to target a photo-sensitiser to neovascular membranes and cause their selective occlusion by irradiating them. The targeting properties of the method promise to yield a treatment for neovascularisation that does not damage adjacent tissues and thus preserves vision. The purpose of the present study was to test the feasibility of occluding ocular vessels with this method.
The iris vessels of the albino rat were chosen because the treatment could be assessed unequivocally and followed with time. Aluminium phthalocyanine tetrasulphonate was encapsulated in heat sensitive liposomes and administered systemically. The iris vessels were irradiated with a yellow laser to raise their temperature to 41 degrees C, cause a phase transition in the liposomes and thereby locally release the photosensitiser. The laser was also used to excite the released photosensitiser and cause occlusion. The effect was monitored immediately and for 8 months thereafter. Controls for the effect of the laser and the unencapsulated drug were conducted.
The results demonstrated that occlusion can be achieved and sustained for the period of follow up. The controls showed that the effect was not due to heat or to the activation of the low dose of free drug.
These preliminary findings indicate that laser targeted photo-occlusion is a promising new method for the treatment of neovascularisation.
目的/背景：新生血管形成见于许多主要的眼部疾病，如糖尿病、年龄相关性黄斑变性和镰状细胞病。激光光凝通常用于闭塞血管，但也会对相邻的正常组织造成严重损伤。这是一个非常显著的局限性，尤其是在治疗脉络膜新生血管时，后者常常覆盖后极部和黄斑的大片区域。一种名为激光靶向递送的方法已被开发出来，它能够在脉络膜或视网膜血管系统中局部且非侵入性地释放药物。该方法可用于将光敏剂靶向输送至新生血管膜，并通过照射使其选择性闭塞。该方法的靶向特性有望产生一种不损伤相邻组织从而保留视力的新生血管形成治疗方法。本研究的目的是测试用该方法闭塞眼部血管的可行性。
选择白化大鼠的虹膜血管，因为可以明确评估治疗效果并随时间进行跟踪。四磺基铝酞菁被包裹在热敏脂质体中并全身给药。用黄色激光照射虹膜血管，将其温度升至41摄氏度，使脂质体发生相变，从而局部释放光敏剂。激光还用于激发释放的光敏剂并导致闭塞。立即监测效果，并在之后的8个月内持续监测。对激光和未包裹药物的效果进行了对照。
结果表明在随访期间可以实现并维持闭塞。对照显示该效果不是由于热或低剂量游离药物的激活。
这些初步发现表明激光靶向光闭塞是一种有前景的新生血管形成治疗新方法。
