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Selective photodynamic treatment
| Details |
Inventors: Peyman, Gholam A.;
Assignee:
Primary Examiner: McDermott; Corrine
Assistant Examiner: Matthews; William H
Attorney, Agent or Firm: Wood, Herron & Evans, L.L.P.
A method and apparatus for selectively targeting photodynamic therapy (PDT) to abnormal tissues. The abnormal tissues may be neovascular intraocular tissue or neoplastic cells. In the eye, a photosensitizing agent is to the vessels then the vessels are collapsed by application of pressure before PDT. Abnormal vessels allow agent to leak into the surrounding tissues, while agent in normal vessels is contained. Upon pressure-induced collapse of intraocular vessels, agent is removed from the vessels and is targeted by subsequent PDT only in surrounding tissues which are susceptible to PDT. Vessel occlusion may be enhanced by administering agents to promote and/or prevent dissolution of clots. The interaction of light with the photosensitizing agent which leaked from neovascular tissue results in cellular or tissue destruction in areas where the agent is located. Thus, normal vessels have no photosensitizing agent and are undamaged by light radiation, while abnormal areas are treated. An apparatus to regulate intraocular pressure is also disclosed. |
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DETAILED DESCRIPTION Phototreatment or photodynamic therapy (PDT) is used to selectively target a desired area of the body for treatment.
A photosensitive agent or drug is administered, then after a certain time period a light source with a wavelength corresponding to the absorbance spectrum of the administered agent is targeted to the particular site for treatment.
A laser is preferably used to direct the light to only the specific tissue or area to be treated.
The time period between administration of the agent and phototreatment is usually between about 1-60 min.
The agent, upon activation by the defined wavelength of light, produces cytotoxic oxygen radicals.
These radicals disrupt microvascular structures in the treatment area and result in subsequent tissue damage.
The extent of the damage may vary, but may include death of some or all of the cells that comprise the tissue.
Thus, treatment may range from cell injury to cell death.
Phototreatment has a dual beneficial effect in treatment of neoplastic cells.
It provides a selective coagulation in site-specific areas, thus depleting malignant cells of nourishment by depleting their blood supply.
Additionally, the free radicals formed in phototreatment directly injure cells by disrupting normal cellular processes and thus provide an additional mechanism of cellular injury or death.
Since the cytotoxic effect is localized due to the short half-life of the radicals, malignant cells are selectively destroyed over normal cells.
With reference to FIG.
1, a mammalian eye 10 is shown.
The locations of the anterior chamber 11, cornea 12, conjunctiva 13, iris 14, optic nerve 15, sclera 16, macula lutea 17, lens 18, retina 20 and choroid 22 are illustrated.
FIG.
2 is a diagrammatic enlargement of the circled area of FIG.
1.
Between the retina 20 and the choroid 22 there is an outer segment of photoreceptor cells 24 including rods and cones, a subretinal space 25, and a layer of retinal pigment epithelium (RPE) 26.
In a normal adult, retinal blood vessels 28, including capillaries, have walls or membranes 29 that contain no fenestrations or openings
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