Retinal burns from experimental laser iridotomy

Simulated argon laser iridotomy was performed in 12 cynomolgus monkey eyes to evaluate the effectiveness of the Abraham iridectomy lens in preventing inadvertent retinal burns. At 600 milliwatts, only two of the three eyes developed small retinal burns using the Abraham lens, whereas three eyes developed larger retinal burns without the Abraham lens. At 1000 milliwatts, retinal burns occurred with or without the Abraham lens, but the size and intensity of the burns were reduced with the lens.     

Chemical Injury to the Eye from EMLA Cream During Erbium Laser Resurfacing

BACKGROUND: EMLA cream is commonly used as a topical anesthetic by physicians performing dermatologic surgery. OBJECTIVE: The purpose of this article is to inform physicians that EMLA cream is highly alkaline and can be particularly toxic to the eye. Symptoms of eye irritation may be initially masked because of local anesthetic effects. METHODS: Two patients are described who developed corneal abrasions from inadvertent exposure of the eye to EMLA cream prior to erbium laser resurfacing. RESULTS: The patients developed corneal abrasions and conjunctivitis, consistent with chemical alkaline burns. CONCLUSION: EMLA cream should be used with extreme caution near the eye and probably should be avoided when there is a need to insert laser eye shields.     

Simultaneous irradiation and imaging of blood vessels during pulsed laser delivery

BACKGROUND AND OBJECTIVE: Simultaneous irradiation and viewing of 10-120 microm cutaneous blood vessels were performed to investigate the effects of 2-micros 577-nm dye laser pulses. STUDY DESIGN/MATERIALS AND METHODS: A modified scanning laser confocal microscope recorded vessel response to different radiant exposures (J/cm2). Probit analysis determined the 50% probability ("threshold") radiant exposure necessary to cause embolized or partly occluding coagula, coagula causing complete blood flow stoppage, and hemorrhage. RESULTS: A statistically significant difference in the threshold radiant exposure existed for each damage category for blood vessels 10-30 microm in diameter, but not for larger vessels. For vessels over 60 microm, complete flow stoppage was unattainable; increasing laser pulse energy produced hemorrhage. In larger vessels, coagula often were attached to the superficial vessel wall while blood flowed underneath. Monte Carlo optical and finite difference thermal modeling confirmed experimental results. CONCLUSION: These results provide insight into the role of pulse duration and vessel diameter in the outcome of pulsed dye laser irradiation.     

Penetrating keratoplasty for corneal perforation in an obtunded patient.

A ventilator-dependent patient obtunded from severe head trauma suffered a spontaneous corneal perforation with lens extrusion secondary to nosocomial Pseudomonas keratitis. Despite the patient's guarded condition, a successful tectonic penetrating keratoplasty with lens removal was performed for restoration of the globe. Upon recovery, the patient's only useful vision was in her operated eye. Preventative measures against prolonged corneal exposure in an obtunded patient include copious artificial tears and lubricants, use of scleral lenses, moisture chambers, bandage contact lenses, or tarsorrhaphies.     

Temperature controlled burn generation system based on a CO2 laser and a silver halide fiber optic radiometer

BACKGROUND AND OBJECTIVES: Experimental animal study of burns is dependent on a reliable burn generation system. Most of the experimental systems used today are unable to produce precise partial thickness burns. This limits the ability to study minor changes associated with burn care. The aim of the study was to develop a method for generating burns with a fixed depth using a CO2 laser burn generation system. MATERIALS AND METHODS: The burn generation system was composed of two components: a burn generation device and a temperature sensing and control system. These components were designed to operate together in order to keep a constant, predetermined skin surface temperature during prolonged burn generation. One hundred thirty-eight spot burns were generated on the back of five shaved 450 g male Wistar rats. The rat skin was exposed to a 70 degrees C for 5-60 seconds. The burned areas were excised and underwent evaluation by hematoxylin-eosin-stained slide microscopy. RESULTS: A linear correlation was found between the duration of exposure and the average burn depth (r = 0.93). This correlation is represented by the equation: burn depth in millimeters = 0.012x (duration in seconds of skin exposure at 70 degrees C). CONCLUSIONS: The fiber-optic-controlled laser burn generation system studied is a reliable tool for creating partial thickness as well as full thickness skin burns in rats.     

Neodymium:YAG laser interaction with intraocular lenses: an in vitro toxicity assay

Use of the Nd:YAG laser is an effective technique to open an opacified posterior lens capsule. However, in the presence of a posterior chamber intraocular lens (IOL), precise focusing of the laser on the capsule is required to avoid pitting the lens optic. The question has been raised whether toxic products may result from laser damage to the IOL. We addressed this issue in the present study by exposing primary human corneal endothelial cell and human corneal organ cultures to solutions produced by purposefully hitting IOLs immersed in cell growth medium with a Nd:YAG laser. The lenses studied were lathe-cut polymethylmethacrylate (PMMA), injection-molded non-UV PMMA, injection-molded UV PMMA, and cast-molded UV PMMA. Samples of each material were irradiated in a holder containing 1 ml of cell culture medium using the following conditions: 5, 10, and 50 laser bursts at 10 millijoules (mJ), and 50 laser bursts at 5 mJ. The solutions were applied to the endothelial cell cultures (all materials) and to the corneal organ cultures (injection-molded non-UV lenses only). There was no toxicity in either assay for any of the materials studied.     

Unintentional macular injury following high-energy cosmetic laser calibration

Unwelcome hair has become a significant issue encountered in our society by young people, particularly young women. Hair removal has been achieved through various methods, both mechanical, with intense pulse light therapy and laser photoablation of hair follicles using various energy delivery systems. There is a relative paucity of clinical trials comparing the safety and efficacy of various hair removal modalities. A comparative study between alexandrite, diode, and intense pulsed light (IPL) was conducted and found similar safety profile across all three modalities. Several adverse effects have been noted as a result of this therapy. Laser-assisted hair removal can lead to ocular anterior segment and/or retinal injury. A laser beam directed toward the eye may easily penetrate both the eyelid or the cornea and cause catastrophic ocular injury. Unfortunately, regulation and licensing of the use of laser-assisted hair removal devices has not yet been well elucidated nor standardized across Australia. There are few cases in the literature reporting retinal burns following inadvertent laser injury, with even fewer directly involving the macula. We report a case of unilateral anterior uveitis and a macular defect following inadvertent laser exposure, leading to photophobia and pain, and reduced visual acuity.     

Effects of 810 nm laser irradiation on in vitro growth of bacteria: comparison of continuous wave and frequency modulated light

BACKGROUND AND OBJECTIVES: Low intensity laser therapy may modify growth of wound bacteria, which could affect wound healing. This study compares the effects on bacteria of 810 nm laser using various delivery modes (continuous wave or frequency modulated light at 26, 292, 1000, or 3800 Hz). STUDY DESIGN/MATERIALS AND METHODS: Staphylococcus (S.) aureus, Escherichia (E.) coli, and Pseudomonas (P.) aeruginosa were plated on agar and then irradiated (0.015 W/cm(2); 1-50 J/cm(2)) or used as controls (sham irradiated); growth was examined after 20 hours of incubation post exposure. RESULTS: There were interactions of species and modulation frequency in the overall effects of irradiation (P = 0.0001), and in the radiant exposure mediated effects (P = 0.0001); thus individual frequencies and each bacterium were analysed separately. Bacteria increased following 3800 Hz (P = 0.0001) and 1000 Hz (P = 0.0001) pulsed irradiation; at particular radiant exposures P. aeruginosa proliferated significantly more than other bacteria. Pulsed laser at 292 and 26 Hz also produced species-dependent effects (P = 0.0001; P = 0.0005); however, the effects for different radiant exposures were not significant. Bacterial growth increased overall, independent of species, using continuous mode laser, significantly so at 1 J/cm(2) (P = 0.02). Analysis of individual species demonstrated that laser-mediated growth of S. aureus and E. coli was dependent on pulse frequency; for S. aureus, however, there was no effect for different radiant exposures. Further tests to examine the radiant exposure effects on E. coli showed that growth increased at a frequency of 1000 Hz (2 J/cm(2); P = 0.03). P. aeruginosa growth increased up to 192% using pulsed irradiation at 1000-3800 Hz; whereas 26-292 Hz laser produced only a growth trend. CONCLUSIONS: The findings of this study point to the need for wound cultures prior to laser irradiation of infected wounds. Similar investigations using other common therapeutic wavelengths are recommended.     

Damage to the corneal endothelium by minus power anterior chamber intraocular lenses

We present 16 phakic myopic eyes (from -10.00 to -25.00 diopters) corrected by minus power intraocular lenses implanted in the anterior chamber whose corneal endothelium was observed by specular microscopy during a postoperative period from 6 to 18 months. Significant morphologic endothelial changes were noted in three eyes along the border of the lens optic. Around dark zones, which appeared acellular, endothelial cells were enlarged, deformed, and separated. These findings may be produced by intermittent contact between the endothelium and lens. Corneal indentation during specular microscopy occasionally caused a curvilinear reflection which corresponded to the optic border. In three eyes, dark areas without cellular abnormality were observed near the curved edge of the lens. These findings probably resulted from the disturbance of the specular reflection on part of the endothelium due to this edge.     

Importance of cutaneous cooling during photothermal epilation: theoretical and practical considerations

BACKGROUND AND OBJECTIVES: Sapphire contact cooling is widely used to prevent non-specific epidermal injury from occurring during selective laser treatment of unwanted hair and vascular lesions. This small study was performed to examine the clinical response of the skin to 800-nm laser irradiation with varying extent of cutaneous sapphire contact cooling. Observed clinical responses are compared to those predicted by theoretical analysis in an attempt to construct a more complete picture of sapphire contact cooling and its role in preventing non-targeted tissue devitalization during laser treatment of the skin using a wavelength, pulse duration, and radiant exposure commonly used for laser hair removal. STUDY DESIGN/MATERIALS AND METHODS: Three subjects each received a total of three pulses of laser light (800 nm) of equal radiant exposure (60 J/cm(2)), pulse duration (30 msec), and spot size (9 mm x 9 mm), but with varying extent of cutaneous cooling. One site was pre-cooled and heat-sinked with a chilled (5 degrees C) sapphire window in contact with the skin; another site was heat-sinked only with a room-temperature (20 degrees C) sapphire window in contact with the skin; and a third site received no pre-cooling or heat-sinking. Each site was examined immediately after treatment and at intervals throughout a 3-month period. The thermal response of the tissue was calculated in each case using a Monte Carlo model for light transport in multi-layered tissues coupled with an axisymmetric finite-difference heat diffusion model. Thermal injury was modeled as a first-order kinetic rate process using an Arrhenius expression. RESULTS: In all three subjects, the sites that were pre-cooled and heat-sinked showed no evidence of epidermal or dermal devitalization. The three sites that were heat-sinked only had a few patches of perifollicular epidermal devitalization and subsequent desquamation without any permanent epidermal or dermal injury, as would be evidenced by pigmentary alteration or textural change. In each subject, the site that received no pre-cooling or heat-sinking sustained epidermal and dermal devitalization, appearing as ulceration and resulting in sustained erythema and textural alteration. Clinical responses predicted by theoretical analysis agree with the clinical observations and show that the dominant effect of sapphire contact cooling for pulse durations of 30 msec or less is the reduction of fluence within the epidermis resulting from index matching at the skin surface. CONCLUSIONS: The results of this small study suggest that by judiciously selecting the laser pulse duration and pre-cooling and heat-sinking the epidermis in a manner that provides index matching and compression of the skin, epidermal damage can be avoided while administering the highest, most effective radiant exposures.     

Port wine stain treatment with a dual-wavelength Nd:Yag laser and cryogen spray cooling: a pilot study

BACKGROUND AND OBJECTIVES: We report on a pilot study of port wine stain (PWS) treatment with a prototype Nd:YAG/KTP laser system, emitting simultaneously at 1,064 and 532 nm, and equipped with a cryogen spray cooling (CSC) device. STUDY DESIGN/PATIENTS AND METHODS: On 10 patients (4-36 years old, mean: 16.2 years) with skin types II-III, therapeutic efficacy of the dual-wavelength laser (KTP+) was compared with a standard KTP laser (532 nm only) at the same pulse duration (25 millisecond), spot diameter (3 mm), and CSC parameters. The fluences were selected in order to obtain the same immediate response with both laser systems. Blanching of each test segment was assessed 8 weeks post treatment by an independent evaluator and by the subjects, and graded on a 1-4 scale. RESULTS: Significant blanching of PWS was noted 8 weeks after a single therapeutic session with the KTP+ laser (mean: 532 nm radiant exposure: 8.2 J/cm(2)), very similar to that observed with KTP at 12.4 J/cm(2). The evaluator noticed a slight brownish coloration in areas treated with the KTP+ laser. Isolated beam-sized atrophic scars were present in two patients where KTP+ (9 and 10 J/cm(2)) and KTP (14 J/cm(2)) lasers were used. CONCLUSIONS: The addition of 1,064 nm radiation allowed a significant reduction of 532 nm radiant exposure with no loss of efficacy in PWS treatment.     

Excimer ablation of human intervertebral disc at 308 nanometers

Excimer laser energy, which has been shown to photoablate tissue at a precisely controllable rate with minimal thermal damage, was applied to human intervertebral disc in an effort to develop a technique for percutaneous discectomy. Cadaveric samples of human disc were used. Excimer laser energy was produced by a XeCl, magnetically switched, long-pulse laser working at 308 nm, 20 Hz. Annulus tissue of approximately 1 mm thickness was placed in contact with the output tip of a 400 microns core diameter quartz fiber, and measurements of ablation rate were made at different radiant exposures. Ablation rates were found to vary linearly with radiant exposure, from 0.7 micron/pulse at 10 mJ/mm2 to 11.0 microns/pulse at 55 mJ/mm2, with a correlation coefficient of 0.984. Threshold radiant exposure, calculated by extrapolation, was found to be about 7 mJ/mm2. Histologic analysis showed a minimum of thermal damage in these specimens, and when ablated with modification to maintain constant fiber-tissue contact, thermal injury was nearly absent, as compared to samples ablated with Nd:YAG through a contact probe. Thermographic analysis, performed using the AGA 782 Digital Thermography system, showed increasing temperature with increasing radiant exposure, with a maximum temperature of 47.2 degrees C at 55 mJ/mm2. In that precise tissue ablation was demonstrated with minimal generated heat, and excimer energy at 308 nm is transmissible through fiber optics, excimer holds great promise for the development of a percutaneous discectomy technique.     

Influence of laser wavelength and pulse duration on gas bubble formation in blood filled glass capillaries

BACKGROUND AND OBJECTIVES: Hypervascular skin lesions (HVSL) are treated with medical lasers characterized by a variety of parameters such as wavelength lambda, pulse duration t(p), and radiant exposure E that can be adjusted for different pathology and blood vessel size. Treatment parameters have been optimized assuming constant optical properties of blood during laser photocoagulation. However, recent studies suggest that this assumption may not always be true. Our objective was to quantify thermally induced changes in blood that occur during irradiation using standard laser parameters. STUDY DESIGN/MATERIALS AND METHODS: Glass capillary tubes (diameter D = 100, 200, and 337 microm) filled with fresh or hemolyzed rabbit blood were irradiated once at lambda = 585, 595, or 600 nm, t(p) = 1.5 milliseconds; and also at lambda = 585 nm, t(p) = 0.45 milliseconds. E was increased until blood ablation caused formation of permanent gas bubbles. In a corroborative study, human blood was heated at 50 degrees C and absorbance spectra were measured as a function of time. RESULTS: Threshold radiant exposure, E(thresh), for gas bubble formation was found not to depend on lambda, which might be surprising in view of the 10-fold lower absorption coefficient at 600 nm as compared to 585 nm. The spectroscopic study revealed heat-induced changes in blood constituent composition of hemoglobins (Hb) from initially 100% oxyhemoglobin (HbO2) to deoxyhemoglobin (HHb) and, ultimately, methemoglobin (metHb) as the major constituent. Model calculations of E(thresh)(lambda,D) based on changing constituent blood composition during heating with milliseconds lasers were found to correlate with experimental results. CONCLUSIONS: For laser treatment of HVSL it appears that lambda is of secondary importance and that the choice of t(p) is a more important factor.     

Electron microscopic appearances of human corneal endothelium following Nd:YAG laser iridotomy.

We looked at the electron microscopic appearances of the corneal endothelium following neodymium:YAG (Nd:YAG) laser iridotomy in a patient with a shallow anterior chamber. An area of denuded endothelial cells approximately 500 microns in diameter was produced when no contact lens was used. The area of cell loss was reduced by approximately 50% when an Abraham YAG goniolens was used. We conclude that the use of a positive plus contact lens can help minimize cell loss following Nd:YAG laser iridotomy.     

Mid-IR laser ablation of articular and fibro-cartilage: a wavelength dependence study of thermal injury and crater morphology

BACKGROUND AND OBJECTIVE: The aim of this study was to evaluate areas of collateral thermal injury and crater morphology for evidence of wavelength-dependent effects on the ablation of articular cartilage and fibro-cartilage (meniscus) using selected mid-IR wavelengths produced by a free electron laser. STUDY DESIGN/MATERIALS AND METHODS: Two types of cartilage, articular cartilage and fibro-cartilage were used in the study. The wavelengths (lambda) evaluated were 2.79, 2.9, 6.1, and 6.45 microm generated by a free electron laser (FEL) using a 4 microseconds macropulse configuration. The zone of thermal injury and crater morphology produced by laser ablation were examined by light microscopy following standard histologic processing. RESULTS: The zone of thermal injury and crater morphology created in cartilage by the FEL at selected mid-IR wavelengths were examined as a function of incident radiant exposure. Ablation using lambda = 6.1 microm provided the largest crater size for both articular and fibro-cartilage at all radiant exposures. For the zones of collateral thermal injury in articular cartilage, lambda = 6.1 microm produced the least thermal injury at the radiant exposure of 7.6 J/cm2. When the radiant exposure is increased to 20.4 J/cm2, both lambda = 6.1 and 6.45 microm produced less thermal injury than the ablation using lambda = 2.79 and 2.9 microm. The greatest amount of collateral thermal injury was produced by lambda = 2.79 microm for both tissue types. CONCLUSIONS: The results demonstrate that crater depth and collateral thermal injury produced in articular cartilage and fibro-cartilage are wavelength-dependent with 6.1 microm providing the largest craters at all radiant exposures. The least amount of thermal injury was created in articular cartilage using lambda = 6.1 microm at the radiant exposure of 7.6 J/cm2. Both 6.1 and 6.45 microm wavelengths demonstrated similar amount of thermal injury at 20 J/cm2 that was less than lambda = 2.79 and 2.9 microm at similar fluences. These observations are explained based on the absorption by water and protein in the tissue types studied. It is further observed that the use of crater dimensions may not provide a reliable estimate for the amount of tissue removal provided by an ablation procedure.     

Arterial response to excimer and argon laser irradiation in the atherosclerotic swine

Injury associated with laser-induced tissue ablation may be reduced by using pulsed energy delivery at low repetition rates, as opposed to using continuous wave energy delivery. This study was designed to examine the similarities and differences between these two systems as regards the healing process, and to examine whether one is superior to the other. In order to test this postulate, the healing response of normal and atherosclerotic aorta were examined after exposure in vivo to argon and excimer (XeCl 308 nm) laser radiation in hypercholesterolemic swine. Swine were fed hyperlipidemic diets for eight months following balloon denudation of the descending aorta. Following general anaesthetic, the descending aorta was isolated and laser burns were made on both normal and atherosclerotic intima using a continuous wave argon laser delivered through a 50 diameter quartz fibre, and a XeCl excimer laser carried through a 1 mm diameter fibre. Energy levels of 3 to 5 J were applied with the argon laser. The pulse duration for the excimer laser was 30 ns and craters were produced using 10 to 60 pulses at a repetition rate of 20 Hz and an energy density of 2 J cm^–2.Forty-eight hours after laser application, craters created by both lasers were filled with thrombus material. Argon burns were surrounded by thermal and acoustic injury which was not seen with excimer burns. Three weeks after laser application all crater surfaces were reconstituted. Unlike the excimer burns, argon craters demonstrated necrosis well beyond the crater margins and were characterized by multinucleate giant-cell reaction surrounding char debris. By nine weeks both excimer and argon laser burns were covered by fibrous tissue but could be distinguished by the fact that char debris and subjacent tissue injury arose with the argon burns.The results suggest that both lasers can be used to remove focal atherosclerotic plaque from arteries without inducing excessive thrombogenicity. Rapid healing is observed with both; however, damage to surrounding tissue is significantly greater with a continuous energy delivery laser as opposed to pulsed energy delivery.Work supported in part by: Heart and Stroke Foundation of Ontario, Grant-in-Aid No. 5-17     

Increase of dermal blood volume fraction reduces the threshold for laser-induced purpura: implications for port wine stain laser treatment

BACKGROUND AND OBJECTIVES: The average success rate in achieving total blanching of port wine stain (PWS) lesions treated with laser-induced selective photothermolysis is below 25%, even after multiple treatments. This is because smaller diameter (5-20 microm) PWS blood vessels are difficult to destroy with selective photothermolysis since the volumetric heat generated by absorption of laser light is insufficient to adequately heat the entire vessel wall. The aim of this study was to investigate a potential technique for more efficient photocoagulation of small diameter PWS blood vessels in PWS that respond poorly to selective photothermolysis. STUDY DESIGN/MATERIALS AND METHODS: The blood volume fraction (BVF) in the upper dermis of the forearm of human volunteers was increased by placing an inflated blood pressure cuff on the upper arm. Applied pressures were in the range of 80-100 mm Hg for up to 5 minutes. The increased BVF was determined by matching reflectance spectra measured with that computed using a diffusion model. The impact of increased BVF on purpura formation induced by a 0.45 milliseconds pulsed dye laser (PDL) at 585 nm wavelength was investigated in normal and in PWS skin. RESULTS: In the presence of a 100 mm Hg pressure cuff, the BVF, as determined from the diffusion model, increased by a factor of 3 in the forearm and by 6 in the hand. Increasing BVF by a factor of 3 corresponds to an increase in blood vessel diameters by a factor of radical 3 approximately 1.7. BVF increased at 1-3 minutes after application of the pressure cuff, remained constant at 3-5 minutes, and returned to baseline values at 3 minutes after removal of the pressure cuff. Approximately 40% less radiant exposure was needed to induce the same amount of purpura after PDL irradiation when the blood pressure cuff was used. Applying an 80 mm Hg pressure cuff reduced the required radiant exposure for purpura formation by 30%. Heating of blood vessels was calculated as a function of vessel diameter and of radiant exposure (at 585 nm and at 0.5 and 1.5 milliseconds pulse duration). CONCLUSIONS: Enlarging the vessel lumen, for example, by obstructing venous return, can significantly reduce the "small-vessel-limitation" in PDL treatment of PWS. Dilation of PWS blood vessels enables a more efficient destruction of smaller vessels without increasing the probability of epidermal damage.     

Dynamic reflectometer for control of laser photocoagulation on the retina

In retinal laser photocoagulation, constant exposure parameters do not result in identical lesions. This lack of reproducibility increases the rate of complications from over-or undertreatment and inhibits determination of the optimal treatment endpoints for different retinal disorders. To this end, a feedback-controlled photocoagulator could make retinal photocoagulation a safer, more reproducible, and faster procedure. A dynamic confocal reflectometer was integrated into a slit lamp laser delivery system. Real-time reflectance changes on the retinas of pigmented rabbits were obtained by monitoring the increasing back-scattered light of the coagulating beam during argon laser photocoagulation. Reproducible temporal reflectance patterns were measured that correlated with ophthalmoscopically assessed lesion intensity independent of the exposure parameters, the transparency of the optical media, and the focusing conditions. As a step toward the development of a feedback-controlled photocoagulator, the confocal reflectometer has been proven in animal trials closely resembling clinical practice. © 1994 Wiley-Liss, Inc.     

Photomechanical transdermal delivery: the effect of laser confinement

BACKGROUND AND OBJECTIVE: Photomechanical waves can transiently permeabilize the stratum corneum and facilitate the delivery of drugs into the epidermis and dermis. The present study was undertaken to assess the effect of pulse characteristics to the penetration depth of macromolecules delivered into the skin. STUDY DESIGN/MATERIALS AND METHODS: Photomechanical waves were generated by confined ablation with a Q-switched ruby laser. Fluorescence microscopy of frozen biopsies was used to assay the delivery of macromolecules through the stratum corneum and determine the depth of penetration. RESULTS: Photomechanical waves generated by confined ablation of the target have a longer rise time and duration than those generated by direct ablation. Confined ablation required a lower radiant exposure (from approximately 7 J/cm(2) to approximately 5 J/cm(2)) for an increase in the depth of delivery (from approximately 50 microm to approximately 400 microm). CONCLUSIONS: Control of the characteristics of the photomechanical waves is important for transdermal delivery as they can affect the depth of drug penetration into the dermis.     

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.