Retinal and choroidal vessel closure using phthalocyanine photodynamic therapy

Chloro-aluminum sulfonated phthalocyanine (CASPc) is a photoactive dye capable of generating photochemical reactions when excited with 675 nm light. We used CASPc to produce photochemical closure of retinal medullary ray vessels and choroidal vessels in normal rabbits. Irradiation prior to CASPc injection produced no photographic, angiographic, or histologic lesions in any eyes. Identical irradiation of medullary ray and choroidal vessels after CASPc injection produced complete vessel closure in all eyes. Histopathologic examination showed marked thrombosis of medullary ray and choroidal vessels, with minimal damage to contiguous tissues including the neurosensory retina. We conclude that CASPc can produce profound closure of normal retinal and choroidal vessels with minimal deleterious effect on surrounding tissues. © 1994 Wiley-Liss, Inc.     

Selective occlusion of choroidal neovascularization by photodynamic therapy with a water-soluble photosensitizer, ATX-S10

BACKGROUND AND OBJECTIVE: To determine the optimal treatment parameters for selective occlusion of choroidal neovascularization (CNV) by photodynamic therapy (PDT) by using the photosensitizer ATX-S10 and a diode laser (wavelength = 670 nm). MATERIALS AND METHODS: Experimental CNV was induced in rat fundi by argon laser photocoagulation. The distribution of ATX-S10 in the chorioretina was analyzed by fluorescence microscopy, and the optimal treatment parameters for selective occlusion of CNV were investigated by changing the dosage and timing of laser irradiation. CNV closure and resulting damage of the surrounding tissue were documented by fluorescein angiography and light and electron microscopies. RESULTS: Fluorescence of ATX-S10 was observed to be localized in the vascular lumen of the retina and choroid within 5 min after dye injection and increased in intensity in CNV up to 2-6 h and decreased rapidly in normal tissue. Laser irradiation with radiant exposures of 7.4 J/cm2 applied immediately after dye injection or with 22.0 J/cm2 at 2-4 h later effectively occluded the induced CNV without causing significant damage to normal retinal capillaries and large choroidal vessels. CONCLUSIONS: PDT using ATX-S10 can selectively occlude CNV. ATX-S10 is a potentially useful photosensitizer for the treatment of CNV.     

Photodynamic laser cyclodestruction with chloroaluminum sulfonated Phthalocyanine (CASPc) or photofrin®(PII) Vs. Nd:YAG laser cyclodestruction in a pigmented rabbit model

Background and Objective: To investigate Photofrin® (PII) and CASPc for photodynamic therapy (PDT) of the ciliary body in rabbits. Study Design/Materials and Methods: PII (10 mg/kg) or CASPc (1 mg/kg) was given by ear vein. Pharmacokinetics were studied in frozen sections by fluorescence microscopy (CCD camera based low light detection system with digital image processing) at 1 and 24 h (8 rabbits;16 eyes). Laser light was delivered (argon pumped dye laser;630 and 675 nm;8 rabbits;16 eyes) by contact fiberoptic. To compensate for iris attenuation, irradiance was 125 mW/cm² (20, 40, 80, or 160 J/cm²). Controls (4 rabbits;8 eyes) received laser light without photochemicals (OD) and for comparison, continuous wave Nd:YAG laser by fiberoptic (0.8–1.2J;OS). Results: Localization studies showed intravascular distribution with some selective ciliary body distribution at 24 h (PII > CASPc). Rabbits treated with PII or CASPc exhibited variable amounts of gross ciliary body edema, infarction, and necrosis by 24–48 h. This response was not seen in PDT control tissues;damage was seen in the iris and ciliary body, with partial vacuolization of the pigment epithelium. Conclusion: PDT may offer a more selective approach to ciliary body destruction. A small but significant thermal effect was seen during PDT from melanin photon uptake with damage to iris and ciliary body. Thermal damage and potential interaction with ocular visual pigments may limit use of these photochemicals and wavelengths for PDT of the ciliary body © 1995 Wiley-Liss, Inc.     

The morphological and functional changes in rat bladder following photodynamic therapy with phthalocyanine photosensitization

We have studied photodynamic therapy (PDT) in the rat bladder with a new photosensitizer, aluminium sulfonated phthalocyanine (AlSPc) given intravenously and intravesically. The microscopic distribution of photosensitizer fluorescence in the bladder wall was studied by laser fluorescence microscopy. Prior to PDT the bladder capacity and compliance were assessed by filling cystometry. Intravesical red light (675 nm.) from a copper vapour pumped dye laser was used to activate the photosensitizer using light doses of 20 to 200 J/cm2. Urodynamic and histologic changes were studied at intervals for up to three months. The fluorescence studies showed that AlSPc was eliminated from the deeper muscle layers more quickly than from the superficial layers of the bladder wall so that by 24 hours there was four times as much fluorescence from the mucosa and lamina propria compared to the deeper muscle. Control bladders illuminated with laser light alone showed no effects at these light doses. Animals treated 24 hours after sensitization showed a reduction in bladder capacity of up to 78% (20 J/cm2. light and 1.5 mg./kg.AlSPc). An initial reduction in compliance recovered in two weeks after low doses (0.5 mg./kg.) of AlSPc but was still abnormal at three months after higher doses (1.5 mg./kg.); though there was no long term histologic abnormality seen. Aluminium sulfonated phthalocyanine is a promising photosensitizer for bladder photodynamic therapy and using low doses of the drug it is possible to produce a superficial necrosis without muscle damage across a range of light doses. This heals by epithelial regeneration with no long term functional impairment. Direct absorption of this photosensitizer following intravesical administration seems unreliable.     

Possibility of choriocapillary occlusion under experimental subretinal hemorrhage by photocoagulation with lasers of different wavelengths

To clarify the possibility of occluding choroidal neovascularization in subretinal hemorrhage with various laser wavelengths, lesions of experimental subretinal hemorrhage were photocoagulated with argon, dye, and krypton lasers and were examined by light and electron microscopy. Our experimental results revealed that laser photocoagulation with wavelengths longer than 590 nm was effective in occluding the choriocapillaries under a thin subretinal hemorrhage. Complete occlusion of choriocapillaries was accomplished by red dye laser (630 nm) or krypton red laser. The choroidal lesion coagulated by 590 nm dye laser showed more extensive reaction than the other lesions at a posttreatment interval of 7 days. The red dye laser (630 nm) or krypton red laser is recommended for the treatment of neovascular maculopathy under thin subretinal hemorrhage because of less reaction and complete occlusion of the choroidal neovascularization.     

Effectiveness of corneal neovascularization photothrombosis using phthalocyanine and a diode laser (675 nm)

We used chloroaluminum sulfonated phthalocyanine as a photosensitizer and a diode laser as a light source for induction of photothrombosis of corneal neovascularization. Corneal neovascularization was induced in 1 eye of each of 10 New Zealand white rabbits using intrastromal 6.0 silk sutures. After the intravenous injection of phthalocyanine in a dose of 4 mg per kg of body weight, photothrombosis was carried out using a diode laser emitting at 675 nm. The animals were followed up by both fluorescein angiography and slit-lamp photography for up to three months. At the end of the follow-up period the eyes were prepared for histology. After photothrombosis, thrombus formation was induced within new vessels demonstrating histological characteristics of both arterioles and venules. Most of the vessels disappeared or remained closed during the follow-up period. Recanalization of some of the thrombosed vessels occurred within the first 20 days after the operation. The combination of phthalocyanine and a 675 nm diode laser is effective for the induction of photothrombosis of corneal neovascularization. © 1993 Wiley-Liss, Inc. © 1993 Wiley-Liss, Inc.     

Accidental Nd:YAG laser-induced choroidal neovascularization

BACKGROUND: There are few reports in the literature to describe the natural history of an occupational Nd:YAG laser-induced retinal injury. METHODS: The chronological response to a Nd:YAG laser-induced injury was studied in a 48-year-old male using the techniques of color fundus photography, fluorescein angiography and optical coherence tomography. When he developed choroidal neovascularization his response to photodynamic therapy with verteporfin was recorded. RESULTS: The patient initially developed a macular hole, which spontaneously closed. Three months after the injury a choroidal neovascular membrane developed. This stabilized after the use of photodynamic therapy. CONCLUSIONS: Surgical closure of Nd:YAG induced macular holes should be delayed to allow spontaneous closure. Photodynamic therapy was successful in treating choroidal neovascularization in this case.     

Threshold parameters for choroidal vessel closure with the photosensitizer, lambda 27

Objective: To determine the threshold photodynamic therapy parameters, required for choroidal vessel closure, with the photosensitizer, Lambda 27, in Dutch belted rabbits, using fluorescein angiography and histopathology. Design: A pre-clinical experiment. Place and Duration of Study: Department of Ophthalmology at the Tulane University Health Sciences Center, between June 2001 - July 2002. Patients and Methods: Dutch belted rabbits were divided into two groups. The first group was injected intravenously with an aqueous solution of Lambda 27 at 1mg/kg. Saline was injected intravenously into the second group (controls). Approximately 5 minutes after injection of Lambda 27, a diode laser, mounted on Zeiss 30 SL-M slit lamp, emitting light at a wavelength of 719 nm was used to apply photodynamic therapy to the fundus. Lesions were placed on the choroid of the rabbits at a fixed spot size of 1.5 mm, using powers ranging from 50 to 120 mW, for a duration of 5 to 80 seconds. Choroidal vessel closure was documented by fluorescein angiography, the following day, and by light microscopy, after the animals were sacrificed. Results: Choroidal vessel closure was documented using fluorescein angiography for all of the lesions placed at fluence of 22.7 J/cm2 and above. Histopathology also confirmed this finding. No choroidal vessel closure was seen in the rabbits treated with fluences less than 22.7 J/cm2 or in the control group. Conclusion: This experiment establishes threshold parameters for choroidal vessel closure using the photosensitizer, Lambda 27.     

Comparison of intravenous and intravesical administration of chloro-aluminum sulfonated phthalocyanine for photodynamic treatment in a rat bladder cancer model.

Photodynamic therapy is an experimental treatment of superficial bladder tumors. Photofrin, a mixture of porphyrins, is the only photosensitizer in clinical use in the U.S.A. and its major side effect is prolonged cutaneous phototoxicity. In order to circumvent this problem of phototoxicity, new photosensitizers are being examined. Cutaneous phototoxicity may also be minimized by local administration of photosensitizer. Therefore, in this study, we investigated the photosensitizer chloro-aluminum sulfonated phthalocyanine (CASPc) in vivo in a rat bladder carcinoma model, and compared two different routes of CASPc administration. AY-27 rat bladder carcinoma cells were transplanted into rat bladders. Eight days after tumor transplantation the biodistribution of CASPc in bladder, skin, muscle and bladder tumor was determined by fluorescence measurements after dye extraction. Photosensitizer administered by intravenous injection and intravesical instillation, were compared. The concentration of CASPc in bladder and bladder tumor after intravenous injection and intravesical instillation was similar. The ratio of dye uptake between tumor and normal bladder after either administration was approximately two. Although no systemic absorption of the photosensitizer was observed after intravesical instillation, there was no reduction in tumor uptake or in the ratio between tumor to normal surrounding tissue. Therefore, no systemic side effects of skin phototoxicity are expected upon intravesical instillation. The microscopic biodistribution of CASPc after intravenous injection and intravesical instillation was also compared. After intravenous injection, the photosensitizer was distributed within the whole tumor with increased fluorescence around the microvasculature. In the normal bladder wall, weak fluorescence was seen in the area of the vasculature in the submucosa and the muscularis. After intravesical instillation, strong fluorescence was detected only at the tumor surface and in normal urothelium; no fluorescence was found in other areas of the tumor or in submucosa or muscularis. A comparison of the photodynamic treatment of model bladder tumors showed that tumor destruction after either method was similar but that there were less side effects to normal bladder wall after intravesical instillation of the CASPc. Intravesical administration of photosensitizers may, therefore, be a viable alternative to intravenous injection with potential for reduced systemic and normal tissue toxicity.     

Measurement of the Emission Profiles of Cylindrical Light Diffusers Using a Video Technique

The uniformity of the emission profile produced by a cylindrical light diffuser is an important parameter for determining the light dose received by the target tissue during laser therapies such as photodynamic therapy (PDT) and interstitial laser photocoagulation (ILP). A technique originally used for determining the profile of a laser beam with a commercial video camera is adapted in order to measure the distribution of light from a cylindrical diffuser. The method can produce quantitative one-dimensional beam profiles in both the circumferential and axial direction of the light diffuser. The system allows the use of tissue phantoms that provide a convenient and effective method for comparing manufacturer's measurements often made in air with those to be expected in vivo. The technique is a quick and easy method for assessing light diffusers before treatment, and utilises readily available equipment that does not require specialist knowledge. Also, the response of the video camera facilitates the assessment of diffusers over a relatively broad optical spectrum, which encompasses the range of wavelengths currently used for both PDT (515–675 nm) and ILP (800–1064 nm). Paper received 25 January 1998; accepted after revision 8 June 1998.     

Long-term effectiveness of photodynamic therapy by using a hydrophilic photosensitizer ATX-S10(Na) against experimental choroidal neovascularization in rats

BACKGROUND AND OBJECTIVE: We previously demonstrated that a hydrophilic photosensitizer ATX-S10 had a potent photodynamic effect. This study was designed to reveal the long-term effectiveness of photodynamic therapy (PDT) with this agent in occluding choroidal neovascularization (CNV) and its selectivity in the neovascular tissue. STUDY DESIGN/MATERIALS AND METHODS: Experimental CNV was induced by intense photocoagulation in rat eyes. Immediately or 2 hours after intravenous injection of 8 mg/kg body weight of ATX-S10(Na), a cis isomer of ATX-S10, eyes were irradiated by a diode laser at the radiance of 3.25-65.3 J/cm(2) Vascular occlusion was identified by fundus photography, fluorescein angiography, and histology at 1, 3, 7, 14, and 28 days after PDT. As controls, non-neovascular eyes were subjected to PDT and similarly analyzed. RESULTS: By using the following treatment parameters, PDT with ATX-S10(Na) successfully occluded CNV without causing occlusion of retinal capillaries for 28 days; 7.4 and 19.6 J/cm(2) immediately after dye injection and 36.7 and 65.3 J/cm(2) 2 hours after injection. Although these conditions also caused occlusion of normal choriocapillaries and mild injuries of retinal vessels, retinal pigment epithelium, and photoreceptors at 1 day, retinal vessels and pigment epithelial cells recovered from damages by 28 days. No injuries were found in the inner retina. CONCLUSION: In optimal treatment conditions, PDT with ATX-S10(Na) can induce long-term, selective occlusion of CNV without causing irreversible damages in the inner retina.     

Photodynamic therapy for esophageal lesions: selectivity depends on wavelength, power, and light dose

BACKGROUND: Photodynamic therapy with 5-aminolevulinic acid-induced photosensitization could selectively eliminate esophageal epithelial lesions. This study aimed at optimizing laser parameters for 5-aminolevulinic acid photodynamic therapy of the normal rat esophagus. METHODS: Sixty rats received 200 mg/kg 5-aminolevulinic acid orally and were illuminated 3 hours later with either 633 or 532 nm light (n = 30 for each group) through an endoesophageal balloon catheter. Rats received either 8.3 or 25 J/cm diffuser, applied with a 33, 100, or 300 mW/cm diffuser. During illumination, tissue fluorescence measurements and light dosimetry were done. Rats were sacrificed at 48 hours after photodynamic therapy. RESULTS: During illumination, protoporphyrin IX fluorescence declined faster when a higher power output was used. Fluence rate at the esophageal surface was highest for 633-nm light. At 532 nm, light caused less damage to the epithelium and muscle than 633-nm light. Illumination with 33 mW resulted in selective epithelial ablation, whereas illumination with 300 mW caused muscle damage with minor epithelial damage. CONCLUSIONS: The assumed selective epithelial damage of 5-aminolevulinic acid photodynamic therapy in the esophagus largely depends on the combination of wavelength, power, and light dose applied. Most selective epithelial damage was found when low-power 633-nm light was used.     

Attempt of photodynamic therapy on esophageal varices

Small vessels gradually reappear within the esophageal wall after endoscopic injection sclerotherapy or endoscopic variceal ligation, which causes late recurrent bleeding. Additional ligation or a small amount of sclerotherapy of these thin and serpentine vessels is sometimes difficult to perform, and stenosis of the esophagus sometimes occurs after a small amount of sclerotherapy. In this study we attempted endoscopic photodynamic therapy on newly visible vessels and evaluated its ability to prevent recurrent bleeding. Fourteen patients with newly visible vessels within the esophageal wall were enrolled. All patients had esophageal varices secondary to hepatitis B and had their varices eliminated through endoscopic sclerotherapy before neovascularization. Seven patients received photodynamic therapy, and seven patients served as the control group. In the photodynamic therapy group, intravenous injection of 5 mg/kg of hematoporphyrin monomethyl ether was given and immediately followed by endoscopic irradiation of the newly visible vessels by copper vapor laser for 40 min with a power density of 150 mW/cm². Endoscopic examination was performed 3 months later to evaluate the therapeutic effect. The duration of non-bleeding was compared between the two groups. The number of newly visible vessels was found to have decreased after photodynamic therapy when compared with the control group (P < 0.001). Kaplan–Meier analyses demonstrated a longer period of non-bleeding in the photodynamic therapy group. The recurrent bleeding rate in the photodynamic therapy (PDT) group was lower than that in the control group (P = 0.027). One patient in the photodynamic therapy group suffered from facial dermatitis from shining direct light. Endoscopic photodynamic therapy seemed to be effective in the elimination of esophageal newly visible vessels and the prevention of recurrent bleeding.     

Integral laser photodynamic treatment of refractory multifocal bladder tumors

Integral photodynamic therapy with hematoporphyrin derivative was performed on 35 patients who had resistant transitional cell carcinoma of the bladder, mainly carcinoma in situ. The light source was an argon ion pumped dye laser (wavelength 630 nm.) using rhodamine B. Two types of laser light scattering diffuser developed at our department were used: a motor driven laser light scattering diffuser with computer regulation, and an endoscope modified light scattering diffuser tipped with a small quartz bulb containing a lipid nutritious solution as the scattering medium. The total energy density used was 10 to 30 J./cm.2. Of the 35 patients 24 (68.6%) achieved a complete response and 5 (14.3%) a partial response at 3 months. In 10 of the 24 patients there was no recurrence with an average tumor-free interval of 20.9 +/- 16.7 months, ranging from 5 to 60 months. Bladder capacity was decreased to approximately 150 ml. for 3 months after the integral photodynamic therapy without any evidence of hydronephrosis on excretory urograms, except for 2 patients who had a contracted bladder before photodynamic therapy. Integral photodynamic therapy may prove to be useful for the treatment of carcinoma in situ of the bladder.     

Photodynamic therapy with chloroaluminum sulfonated phthalocyanine in the rat window chamber.

The efficacy of photodynamic therapy tumor destruction is dependent upon both the interruption of the tumor vasculature and the resultant production of unstable oxygen species causing cellular oxidation and death. Chloroaluminum sulfonated phthalocyanine (CASP) is a recently developed photosensitizer. In order to study the direct vascular effects of CASP on a non-tumor system, a rat window chamber was utilized. Twelve rats were implanted with the window chamber, and were divided into two groups of six. Three rats served as controls for each group (receiving light alone, CASP alone, or no treatment). The remaining 6 rats received 10 mg/kg CASP intravenously 4 days after chamber placement. Photoactivation with light was performed 24 hours after injection (power density 200 mW/cm2, irradiance 100 J/cm2, lambda = 675 nm). Utilizing integrating sphere measurements and image analysis, marked vascular changes in the form of initial vasospasm followed by vaso-constriction and loss of chamber neovascularization were noted in the CASP-PDT group. The control groups exhibited no significant changes. Manipulation of the chamber vasculature at strategic time-points may translate into improved response rates for photodynamic therapy in a tumor model.     

A comparison of novel light sources for photodynamic therapy

A diode laser, light-emitting diode (LED) array bandwidth 25 nm, full width half maximum (FWHM) and filtered arc lamp (bandwidth 40 nm, FWHM), all with peak emission at about 650 nm, suitable for the photosensitizer tetra(meta-hydroxyphenyl)chlorin (mTHPC), were compared with a copper vapour laser pumped dye laser, using depth of necrosis in normal rat liver as a measure of photodynamic effect. A three-way comparison between a DL10K dye laser, the LED array and the filtered arc lamp resulted in mean depths of necrosis of 4.64, 4.29 and 4.04 mm, respectively, at 20 J cm^-2, the values for the laser and arc lamp being significantly different at the 5% level. A further comparison of a narrower linewidth DL20K dye laser with the LED array, using a light dose of 20 J cm^-2, showed a significant difference between the mean depths of necrosis of 4.97 and 4.05 mm, respectively (p=0.01). A final study, comparing the DL20K dye laser with the diode laser and a light dose of 10 J cm^-2, demonstrated no significant difference in depths of necrosis (3.23 and 3.25 mm, respectively). The results obtained in the three studies are attributed to the relative bandwidths of light emission for the various sources. A simple mathematical model is presented explaining the results in terms of the relative activation of the photosensitizer and the consequent threshold fluence required for the induction of necrosis. It is concluded that, in order to achieve the same depth of effect as a laser when using the broad band sources, the incident fluence would have to be approximately doubled. However, when the low cost and ease of use of the non-laser sources are taken into consideration, these devices are likely to find widespread applications in clinical photodynamic therapy.     

Effect of photodynamic therapy on blood flow in normal and tumor vessels

The aim of this series of experiments was to determine the dynamic blood flow changes that occur in normal and neoplastic tissues during photodynamic therapy. Mice bearing SMT-F tumors and rats with transplanted chondrosarcomas were injected with graded doses of dihematoporphyrin ether. Studies of changes in single-vessel and whole-tumor blood flow were carried out with 630 nm light activation. A helium neon laser Doppler velocimeter was used to stimulate dihematoporphyrin ether, as well as to measure changes in flow velocity in both single-vessel and whole-tumor models. There was a reduction of flow velocity in all vessels and tumors in animals injected with 1 to 40 mg/kg dihematoporphyrin ether intraperitoneally. The extent of flow reduction was related to drug dose administered. Decreases in blood flow began within 10 seconds of light stimulation and were maximal within 5 minutes. Both normal and tumor vessels responded similarly. We conclude that photodynamic therapy leads to significant microcirculatory changes that may be pertinent to the mechanism of tumor necrosis.     

Comparison of lasers for photodynamic therapy with a phthalocyanine photosensitizer

Three different lasers were compared under the same conditions for their effectiveness at producing photodynamic damage to normal colon following sensitization with aluminium sulphonated phthalocyanine (AlSPc). One laser was an argon ion pumped continuous wave (CW) dye laser and the other two were pulsed at 10 kHz (copper vapour laser pumped dye laser, and 5 Hz (flashlamp pumped dye laser). The CW and 10 kHz laser were equally effective at producing damage. The 5 Hz laser failed to produce a photodynamic effect, although occasionally caused a photomechanical effect when the laser fibre was placed touching the colonic mucosa. Quantitative analysis suggests that the high energy pulses of the flashlamp pumped dye laser saturate AlSPc, so very little of the available energy can be used to produce a photodynamic effect, in contrast to the two other lasers which do not produce saturation conditions.     

Direct comparison of in-vitro and in-vivo Photofrin-II mediated photosensitization using a pulsed KTP pumped dye laser and a continuous wave argon ion pumped dye laser.

A pulsed KTP pumped dye laser (25 kHz repetition rate and 470 nsec pulse width) has been compared to a continuous wave argon ion pumped dye laser as the source of 630 nm light during in-vitro and in-vivo Photofrin-II mediated photosensitization studies. Individual experiments documented the effectiveness of each laser system on a) photosensitizer induced cytotoxicity and induction of stress protein synthesis using Chinese hamster fibroblasts; b) photobleaching of Photofrin-II in aqueous solution; c) Photofrin II mediated photosensitization of normal mouse skin; d) Photofrin II mediated photodynamic therapy of a mouse mammary carcinoma; and e) tumor temperature levels generated during laser exposure. Comparable results were obtained for both laser systems in all experiments.     

An in vivo comparison of the photodynamic action of a new diode laser and a copper vapour dye laser at 652 nm

Initial pre-clinical evaluation of a new 652 nm diode laser system for photodynamic therapy was performed to establish its efficacy in photo-activating the second-generation photosensitizer meta-tetrahydroxyphenychlorin (mTHPC). The diode laser was compared directly to a copper vapour laser pumped dye laser using depth of necrosis in normal rat liver as a measure of the photodynamic effect. No significant difference between the two lasers was observed.