Localization of lipoprotein-delivered benzoporphyrin derivative in the rabbit eye

Half-Fluence, Half-Dose Photodynamic Therapy: Less Direct Damage but More Inflammation?

Objective: To present clinical findings and multimodal imaging of three patients who developed bacillary layer detachments (BALADs) shortly after half-fluence, half-dose (HFHD) verteporfin photodynamic therapy (PDT). Methods: Retrospective observational case series. Three patients were treated with HFHD-PDT for (1) macular neovascularisation five years after resolved central serous chorioretinopathy (CSC), (2) persistent serous retinal detachment (SRD) from chronic CSC, and (3) neovascular age-related macular degeneration with persistent SRD despite intravitreal anti-VEGF therapy. Results: Each patient developed a BALAD after HFHD-PDT. Acute fulminant exudation caused subretinal fluid expansion into the inner photoreceptor layer, cleaving myoid from ellipsoid zones in the central macula. Subretinal fluid and the BALADs subsequently resolved over 6–8 weeks. Conclusions: The subretinal fluid and BALAD following HFHD-PDT were transient and did not cause photoreceptor damage over a 6-month follow-up period. We speculate that the reduced-impact HFHD protocol decreases direct tissue damage but increases proinflammatory cytokines. The long-term pathophysiological consequences of the resolved BALADs are unknown.

Exploring the choroidal vascular labyrinth and its molecular and structural roles in health and disease

The choroid is a key player in maintaining ocular homeostasis and plays a role in a variety of chorioretinal diseases, many of which are poorly understood. Recent advances in the field of single-cell RNA sequencing have yielded valuable insights into the properties of choroidal endothelial cells (CECs). Here, we review the role of the choroid in various physiological and pathophysiological mechanisms, focusing on the role of CECs. We also discuss new insights regarding the phenotypic properties of CECs, CEC subpopulations, and the value of measuring transcriptomics in primary CEC cultures derived from post-mortem eyes. In addition, we discuss key phenotypic, structural, and functional differences that distinguish CECs from other endothelial cells such as retinal vascular endothelial cells. Understanding the specific clinical and molecular properties of the choroid will shed new light on the pathogenesis of the broad clinical range of chorioretinal diseases such as age-related macular degeneration, central serous chorioretinopathy and other diseases within the pachychoroid spectrum, uveitis, and diabetic choroidopathy. Although our knowledge is still relatively limited with respect to the clinical features and molecular pathways that underlie these chorioretinal diseases, we summarise new approaches and discuss future directions for gaining new insights into these sight-threatening diseases and highlight new therapeutic strategies such as pluripotent stem cell‒based technologies and gene therapy.

A new perspective on lipid research in age-related macular degeneration

There is an urgency to find new treatment strategies that could prevent or delay the onset or progression of AMD. Different classes of lipids and lipoproteins metabolism genes have been associated with AMD in a multiple ways, but despite the ever-increasing knowledge base, we still do not understand fully how circulating lipids or local lipid metabolism contribute to AMD. It is essential to clarify whether dietary lipids, systemic or local lipoprotein metabolismtrafficking of lipids in the retina should be targeted in the disease. In this article, we critically evaluate what has been reported in the literature and identify new directions needed to bring about a significant advance in our understanding of the role for lipids in AMD. This may help to develop potential new treatment strategies through targeting the lipid homeostasis.

An in silico model of retinal cholesterol dynamics (RCD model): insights into the pathophysiology of dry AMD

We developed an in silico mathematical model of retinal cholesterol (Ch) dynamics (RCD) to quantify the physiological rate of Ch turnover in the rod outer segment (ROS), the lipoprotein transport mechanisms by which Ch enters and leaves the outer retina, and the rates of drusen growth and macrophage-mediated clearance in dry age-related macular degeneration. Based on existing experimental data and mechanistic hypotheses, we estimated the Ch turnover rate in the ROS to be 1–6 pg/mm²/min, dependent on the rate of Ch recycling in the outer retina, and found comparable rates for LDL receptor-mediated endocytosis of Ch by the retinal pigment epithelium (RPE), ABCA1-mediated Ch transport from the RPE to the outer retina, ABCA1-mediated Ch efflux from the RPE to the choroid, and the secretion of 70 nm ApoB-Ch particles from the RPE. The drusen growth rate is predicted to increase from 0.7 to 4.2 μm/year in proportion to the flux of ApoB-Ch particles. The rapid regression of drusen may be explained by macrophage-mediated clearance if the macrophage density reaches ∼3,500 cells/mm². The RCD model quantifies retinal Ch dynamics and suggests that retinal Ch turnover and recycling, ApoB-Ch particle efflux, and macrophage-mediated clearance may explain the dynamics of drusen growth and regression.

Quantum chemistry studies of meta-tetra(hydroxyphenyl)chlorin (mTHPC) and its isomers

Quantum chemistry methods were used to study the meta-tetra(hydroxyphenyl)chlorin (mTHPC) and its isomers. The mTHPC (Foscan®) is a commercial chlorin, used in photodynamic therapy (PDT) and is classified as a second-generation drug in PDT. The present work is to obtain quantum chemistry properties which can explain the high efficiency of the mTHPC compared with its isomers (ortho and para) and other chlorins. Based in the chemical hardness and ionization potential obtained from HOMO and LUMO orbitals energy, our results show that all chlorins have similar reactivity. Moreover, all chlorins have approximately the same capacity to storage energy in the triplet excited state, with energy differences between the ground state and the triplet excited state of 1.38, 1.39 and 1.36 eV for oTHPC, mTHPC and pTHPC, respectively. The calculated UV spectra (a very important quantity which can be correlated with the photosensitizer (PS) efficiency property), shows that the present chlorins all have a peak at 622 nm. Finally, after analysis of the dipole moment differences, between the three isomers, an explanation about the greater mTHPC efficiency in PDT, was possible. Due to its greater lipophilic character, mTHPC is absorbed by tumor cells to a greater degree than oTHPC and pTHPC. Our findings are consistent with literature and can be used to help new drug design for use in PDT.

Evaluation of verteporfin pharmakokinetics--redefining the need of photosensitizers in ophthalmology

INTRODUCTION

The benzoporphyrine derivative verteporfin has lost its importance to the treatment of the most frequent neovascular eye diseases. Nevertheless, it is still mandatory to define the remaining applications, role, and potential of verteporfin in ocular photodynamic therapy (PDT), including the dosages of administration, effectiveness, and safety profile.

AREAS COVERED

Although verteporfin PDT has forfeited the first-line status and value of treating subfoveal choroidal neovascularization (CNV) due to age-related macular degeneration or pathologic myopia, the treatment remains the standard of care for choroidal haemangioma and polypoidal choroidal vasculopathy. PDT is effective in less pigmented choroidal melanoma as well as in retinal vascular proliferations and retinal angioma. Verteporfin was granted the orphan drug designation for the treatment of chronic or recurrent central serous chorioretinopathy (CSC).

EXPERT OPINION

Evidence-based data regarding optimized parameters (low fluence, reduced dose, fractionated irradiation) adapted to the treated diseases (target structure, dosimetry, blood supply) are scarce. Prospective and large clinical trials are missing, although the scientific community agrees on the fact that the standard treatment protocol does not necessarily provide the optimal efficacy to the specific disease or individual patient. Within the reviewed indications, the adverse effect profile is favorable compared with other therapies.

Choroidal neovascularization in pathological myopia

Myopic choroidal neovascularization (CNV) is one of the leading causes of visual impairment worldwide. The clinical and socioeconomic impact of myopic CNV in Asian countries is particularly significant due to rising trend in the prevalence and severity of pathological myopia. The exact pathogenesis of myopic CNV remains unclear and there is paucity of information with respect to incidence and risk factors for myopic CNV from prospective studies. Furthermore, there are no recognized measures that may prevent or delay the development of CNV in eyes with pathological myopia. Advances have been made in the diagnosis and characterization of myopic CNV over the years. Until recently, treatment modalities for myopic CNV were limited to thermal laser photocoagulation and photodynamic therapy with verteporfin, both these modalities primarily aim at prevention of further visual loss. In the last 5 years, inhibitors of vascular endothelial growth factor (VEGF) have been used successfully and may improve vision to some extent. Nevertheless, the long-term safety and efficacy of anti-VEGF agents remains unknown. Furthermore, the risk of developing chorioretinal atrophy remains the key factor in determining the final visual outcome. This review article summarizes the current literature on myopic CNV, highlighting new evolving diagnostic and treatment modalities, prognostic factors influencing visual outcome, and areas of future research.

The ins and outs of cholesterol in the vertebrate retina

The vertebrate retina has multiple demands for utilization of cholesterol and must meet those demands either by synthesizing its own supply of cholesterol or by importing cholesterol from extraretinal sources, or both. Unlike the blood-brain barrier, the blood-retina barrier allows uptake of cholesterol from the circulation via a lipoprotein-based/receptor-mediated mechanism. Under normal conditions, cholesterol homeostasis is tightly regulated; also, cholesterol exists in the neural retina overwhelmingly in unesterified form, and sterol intermediates are present in minimal to negligible quantities. However, under certain pathological conditions, either due to an inborn error in cholesterol biosynthesis or as a consequence of exposure to selective inhibitors of enzymes in the cholesterol pathway, the ratio of sterol intermediates to cholesterol in the retina can rise dramatically and persist, in some cases resulting in progressive degeneration that significantly compromises the structure and function of the retina. Although the relative contributions of de novo synthesis versus extraretinal uptake are not yet known, herein we review what is known about these processes and the dynamics of cholesterol in the vertebrate retina and indicate some future avenues of research in this area.

Cholesterol oxidation in the retina: implications of 7KCh formation in chronic inflammation and age-related macular degeneration

This review will discuss the formation and potential implications of 7-ketocholesterol (7KCh) in the retina. 7KCh is a proinflammatory oxysterol known to be present in high amounts in oxidized LDL deposits associated with atheromatous plaques. 7KCh is generated in situ in these lipoprotein deposits where it can accumulate and reach very high concentrations. In normal primate retina, 7KCh has been found associated with lipoprotein deposits in the choriocapillaris, Bruch's membrane, and the retinal pigment epithelium (RPE). In photodamaged rats, 7KCh has been found in the neural retina in areas of high mitochondrial content, ganglion cells, photoreceptor inner segments and synapses, and the RPE. Intermediates found by LCMS indicate 7KCh is formed via a free radical-mediated mechanism catalyzed by iron. 7KCh seems to activate several kinase signaling pathways that work via nuclear factor κB and cause the induction of vascular endothelial growth factor, interleukin (IL)-6, and IL-8. There seems to be little evidence of 7KCh metabolism in the retina, although some form of efflux mechanism may be active. The chronic mode of formation and the potent inflammatory properties of 7KCh indicate it may be an "age-related" risk factor in aging diseases such as atherosclerosis, Alzheimer's, and age-related macular degeneration.

Effects of photodynamic therapy using hematoporphyrin monomethyl ether on experimental choroidal neovascularization

Hematoporphyrin monomethyl ether (HMME) is a novel and promising second-generation porphyrin-related photosensitizer for photodynamic therapy (PDT). To study the effects of HMME PDT on choroidal neovascularization (CNV) in rats, the PDT was performed 20 min after HMME bolus injection, which was investigated prior to the PDT by fluorescence microscopy with laser-induced CNV, and delivered at an irradiance of 400, 600 and 1000 mW cm(-2) corresponding to a fluence of 36, 54, 90 J cm(-2) in PDT plan I (15 mg kg(-1) HMME). In PDT plan II (30 mg kg(-1) HMME), the laser had a constant irradiance of 600 mW cm(-2), which was delivered for 60, 90 or 150 s, to also achieve total energy doses of 36, 54 or 90 J cm(-2). CNV closure rates assessed by fluorescein angiography and histologic damage to treated areas of choroid and retina varied as a function of the dose of HMME and of the activating light energy fluence. Endothelial cell labeled by platelet/endothelial cell adhesion molecule-1 presented treated CNV lesions that were significantly reduced in size (P < 0.01). It can be concluded that PDT using HMME can effectively occlude CNV. HMME is a potentially useful photosensitizer for the reduction in CNV size of irradiated areas.

Half-dose verteporfin photodynamic therapy for acute central serous chorioretinopathy: one-year results of a randomized controlled trial

OBJECTIVE

To evaluate the efficacy of photodynamic therapy (PDT) with half-dose verteporfin for treating acute central serous chorioretinopathy (CSC).

DESIGN

Prospective, double-masked, placebo-controlled, randomized clinical trial.

PARTICIPANTS AND CONTROLS

Sixty-three eyes of 63 patients with acute symptomatic CSC of 3 months' duration or less were recruited. Forty-three eyes were randomized to indocyanine green angiography (ICGA)-guided PDT with half-dose (3 mg/m(2)) verteporfin and 21 eyes were randomized to placebo.

INTERVENTION

Patients in the verteporfin group received an infusion of half-dose verteporfin over 8 minutes, followed by ICGA-guided PDT 10 minutes from the start of infusion. Laser was applied for 83 seconds covering the choroidal abnormalities observed in ICGA, with a maximum laser spot size of 4500 mum.

MAIN OUTCOME MEASURES

The primary outcome measure was the proportion of eyes with absence of subretinal fluid at the macula at 12 months. Secondary outcome measures included changes in mean logarithm of the minimum angle of resolution (logMAR) best-corrected visual acuity (BCVA), subjective symptoms, optical coherence tomography (OCT) results, central foveal thickness (CFT), and angiographic findings during the 12-month study period.

RESULTS

Thirty-nine patients in the verteporfin group and 19 patients in the placebo group completed 12 months of follow-up. Thirty-seven (94.9%) eyes in the verteporfin group compared with 11 (57.9%) eyes in the placebo group showed absence of subretinal fluid at the macula at 12 months (P = 0.001). The mean logMAR BCVA at 12 months was significantly better in the verteporfin group compared with the placebo group: -0.05 and 0.05, respectively (P = 0.008). All 39 (100%) verteporfin-treated eyes had stable or improved vision, compared with 15 (78.9%) eyes in the placebo group (P = 0.009). The mean OCT CFT for the verteporfin group also was significantly lower compared with the placebo group at 12 months (P = 0.001). No ocular or systemic adverse event was encountered in the study.

CONCLUSIONS

Photodynamic therapy with half-dose verteporfin is effective in treating acute symptomatic CSC, resulting in a higher proportion of patients with absence of exudative macular detachment and better visual acuity compared with placebo.

Contact transscleral ciliary body photodynamic therapy in pigmented rabbits using verteporfin and diode laser: evaluation of treatment parameters

PURPOSE

To evaluate the treatment parameters necessary for achieving ciliary body photodynamic damage, enough to significantly reduce IOP, using verteporfin and a diode laser.

DESIGN

Animal study.

METHODS

The right eye ciliary body of 30 pigmented rabbits was irradiated using verteporfin (Visudyne) and a diode laser. Photosensitizer dose ranged from 0.375 to 2 mg/kg. Three adjacent laser spots were applied 0.5 mm behind limbus at 12 o'clock position using a contact transscleral technique. The laser power was ranging from 10 to 70 mW and the duration of irradiation from 1 to 5 min per spot. The left eyes of the rabbits were used as controls. Animals were sacrificed 24 hours after the procedure and their eyes were evaluated by means of light and electron microscopy. A step-by-step approach was adopted with adjustment of experimental parameters according to histological findings. The end point was to identify the irradiation parameters necessary for induction of photodynamic damage while minimizing thermal damage. Subsequently, 10 more animals were used in order to verify the effectiveness of these irradiation parameters in reducing the intraocular pressure.

RESULTS

The therapy parameters that led to photodynamic effect avoiding thermal damage were laser power of 25 mW, irradiation time of 3 min per spot, and verteporfin dose of 1 mg/kg. Transscleral ciliary body irradiation using these parameters resulted in vascular thrombosis of ciliary vessels and in substantial edema, resulting in separation of the two ciliary epithelium layers. These parameters were applied to 4 rabbits, resulting in a mean IOP reduction of 1.8 mmHg +/- 1.2 that lasted for 4 days. An increase of the laser power to 35 mW tested in 6 additional animals, resulted in mean IOP reduction of 2.2 mmHg +/- 1.2, lasting 6 days; some minimal thermal damage was seen with the later settings.

CONCLUSION

The combination of verteporfin and 690 nm diode laser is effective for the induction of ciliary body photodynamic damage, which results in significant but temporary IOP reduction, after transscleral PDT in pigmented rabbits. With appropriate parameter selection, intraocular pressure reduction can be achieved while thermal damage is kept to a minimum.

Retinal pigment epithelium changes after photodynamic therapy for choroidal neovascularization in pathological myopia

PURPOSE

To describe changes in the retinal pigment epithelium (RPE) induced by photodynamic therapy (PDT) in eyes with subfoveal choroidal neovascularization (CNV) associated with pathological myopia (PM).

METHODS

We carried out an open-label, prospective, interventional case series including 26 patients affected by subfoveal CNV in PM who underwent PDT with a 12-month follow-up. Particular attention was paid to the detection of changes at the RPE level in the areas exposed to the laser compared with baseline conditions.

RESULTS

The median age of the patients was 58.5 years and the median duration of symptoms was 2 weeks. A pigmentary zone was present before PDT in 20 eyes (77%), incompletely encircling the CNV in all but two of the 20 eyes. At the end of the follow-up, the CNV in all eyes was seen to be completely or incompletely encircled by a band of hyperpigmentation, which was surrounded by RPE alterations, including depigmentation in all cases and atrophic changes in 14 eyes.

CONCLUSIONS

After PDT, alterations in the RPE develop in myopic eyes. These include accentuation of the pigmentary zone surrounding the CNV and progressive atrophic changes. Further studies are needed to correlate post-PDT RPE damage with longterm visual outcome.

Safety enhanced photodynamic therapy with half dose verteporfin for chronic central serous chorioretinopathy: a short term pilot study

AIM

To evaluate short term safety of an enhanced photodynamic therapy (PDT) protocol with half dose verteporfin for treating chronic central serous chorioretinopathy (CSC).

METHODS

20 eyes of 18 patients with symptomatic chronic CSC underwent PDT using 3 mg/m2 verteporfin. Verteporfin was infused over 8 minutes followed by indocyanine green angiography guided laser application 2 minutes later. Serial optical coherence tomography (OCT) and multifocal electroretinography (mfERG) recordings were performed before PDT, at 4 days, 2 weeks, and 1 month after PDT. The best corrected visual acuity (BCVA), OCT central retinal thickness, and mean mfERG response amplitudes and peak latencies were compared longitudinally. Subgroup analysis was further performed for eyes with or without pigment epithelial detachment (PED).

RESULTS

At 1 month after PDT, the median BCVA improved from 20/40 to 20/30 (p = 0.001). The mean central retinal thickness also reduced from 276 microm to 158 microm (p < 0.001) and 17 (85%) eyes had complete resolution of serous retinal detachment and/or PED. MfERG showed no significant changes in the mean N1 and P1 response amplitude and latency for all eyes. Subgroup analysis demonstrated that eyes without PED had a significant increase in the mean central mfERG P1 response amplitude with reduction in P1 peak latency at 1 month post-PDT. For eyes with PED, transient reduction in the mean central P1 response amplitude was observed at 4 days post-PDT.

CONCLUSIONS

The modified safety enhanced PDT protocol with half dose verteporfin appeared to be a beneficial treatment option for patients with chronic CSC, especially in eyes without serous PED. Further controlled study is warranted to demonstrate the long term safety and efficacy of this treatment option.

Effect of photodynamic therapy on the function of the outer blood-retinal barrier in an in vitro model

BACKGROUND

Photodynamic therapy (PDT) is a well established clinical treatment for age-related macular degeneration (AMD), and comprises intravenous injection of verteporfin and subsequent application of a non-thermal laser beam to the area of AMD to induce selective vascular occlusion. Since there is evidence that PDT may cause outer blood-retinal barrier (BRB) breakdown and possibly RPE cell alteration, we investigated the effect of PDT on the BRB function of the RPE in an in vitro model.

METHODS

Twenty-one monolayers of human RPE cells were cultured on semipermeable membranes until a stable barrier function was achieved as determined by transepithelial electrical resistance (TER) and sodium fluorescein permeability. To test the effect of PDT on the outer BRB function, non-thermal laser (692 nm), verteporfin or a combination of both were applied. TER assessment prior to and after PDT was utilized to identify changes in barrier function of the RPE in this in vitro model. Finally, monolayers of RPE cells were evaluated by transmission electron microscopy (TEM).

RESULTS

No significant TER decrease was observed after application of non-thermal laser alone or after administration of verteporfin in therapeutic concentrations, but combination of these modalities resulted in significantly decreased TER within 4 h. Except for intercellular blisters, no damage to the RPE was evident in TEM. Verteporfin added at concentrations higher than therapeutic doses (2 mg/ml) resulted in an immediate decrease in TER and damage to the RPE cells.

CONCLUSION

The combination of a therapeutic concentration of verteporfin and application of non-thermal laser resulted in a morphologically and functionally detectable breakdown of the outer BRB function of the RPE without any damage to the RPE cells themselves in vitro. However, increasing the concentration of verteporfin can result in RPE cell damage.

PHOTODYNAMIC THERAPY FOR CHOROIDAL NEOVASCULARIZATION IN PEDIATRIC PATIENTS

PURPOSE

To report the use of photodynamic therapy (PDT) for choroidal neovascularization (CNV) in pediatric patients.

METHODS

Five patients (age range, 7-15 years) who underwent PDT for idiopathic CNV (n = 2) or CNV secondary to macular toxoplasmic scar (n = 3) were included in this study. Follow-up ranged from 12 months to 18 months. PDT was performed according to the standard protocol. We evaluated visual acuity, fluorescein leakage from the CNV, greatest linear dimension of the lesion, and occurrence of ocular or systemic adverse events at baseline and during follow-up.

RESULTS

No severe or moderate visual loss occurred in all cases during follow-up. PDT reduced CNV leakage in four cases. No serious ocular or systemic adverse events were recorded. Retinal pigment epithelium atrophic changes were observed around the regressed CNV, but they did not appear to cause visual loss.

CONCLUSIONS

PDT was safe for pediatric patients, and visual acuity was substantially stable after one or few treatments. Further follow-up is needed to assess if retinal pigment epithelium atrophic changes around the regressed CNV, possibly related to PDT, could affect vision in the long term.

Applications of liposomes in ophthalmology

This review outlines the applications of liposomal formulations in ophthalmology. In ophthalmology, liposomes have been used to treat disorders of both the anterior and posterior segments. These include dry eyes, keratitis, corneal transplant rejection, uveitis, endophthalmitis, and proliferative vitreoretinopathy. Liposomes also have shown promise as vectors for genetic transfection and monoclonal antibody-directed vehicles. Furthermore, heat-activated liposomes have spurred research in focal laser and heat-induced release of liposomal drugs and dyes for selective drug delivery. These techniques have been useful in selective tumor and neovascular vessel occlusion, angiography, and retinal and choroidal blood-flow studies. Although verteporfin is the only liposomal drug currently approved for use in the eye, the benefits of liposomes will likely be applied widely in all treatment, diagnostic, and research aspects of ophthalmology in the future.

Retinal pigment epithelial tear following photodynamic therapy for choroidal neovascularization secondary to AMD

PURPOSE

To describe retinal pigment epithelial tear following photodynamic therapy (PDT) for subfoveal choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD).

DESIGN

Retrospective interventional case series.

METHODS

A retrospective study in an institutional practice. We describe seven cases of retinal pigment epithelial (RPE) tear, which developed in seven eyes of seven patients following PDT. All eyes had subfoveal CNV secondary to AMD.

RESULTS

Six eyes had occult subfoveal CNV, and one eye had recurrent classic subfoveal CNV. In five patients, the eye that developed the tear was the second eye, whereas the first eye had a disciform scar. In four eyes, the RPE tear developed after one PDT, in one eye the RPE tear developed after the second PDT, and in two eyes the RPE tear developed after the third PDT. In five of seven cases, there was a significant visual deterioration following the RPE tear.

CONCLUSIONS

RPE tear is a complication that may occur following PDT in particular when the PDT is applied to an occult subfoveal CNV.

Severe pigment epithelial alterations in the treatment area following photodynamic therapy for classic choroidal neovascularization in young females

PURPOSE

Although photodynamic therapy (PDT) is an established treatment for choroidal neovascularization (CNV), the mechanisms are still not completely elucidated. Damage to the retinal pigment epithelium (RPE) was observed following uncomplicated PDT in young patients.

DESIGN

Observational case series.

METHODS

Four female patients between the age of 26 and 39 years presented with visual loss because of classic CNV. In two 39 years old females the CNV originated secondary to a small chorioretinal scar, in a 26 and a 36-year-old woman the CNV was of idiopathic cause. All patients received standard PDT according to the Treatment of Age-Related Macular Degeneration with Photodynamic Therapy (TAP) Study protocol.

RESULTS

One to three months after an uncomplicated PDT with verteporfin, severe pigment epithelial alterations in the treatment area were observed. The neovascular membranes responded favorably to the treatment and demonstrated fibrosis and resolution of leakage. Ophthalmoscopically and angiographically, atrophy of the retinal pigment epithelium was seen precisely delineating the size of the treatment spot used. Vision declined in two patients from 0.3 to 0.1 and 0.15 to 0.1. The two other patients demonstrated an increase of visual acuity from 0.7 to 0.9 and from 0.4 to 0.9. The retinal pigment epithelium alterations did not resolve during follow-up, but remained unchanged in area and intensity.

CONCLUSIONS

Characteristic retinal pigment epithelium alterations were observed in young female patients with small classic CNV following PDT. Unusual retinal pigment epithelium damage in young female patients without any associated disease might be related to a possible inherent defect in the RPE or to the hormonal status of this specific patient population.

Photodynamic therapy with verteporfin: a new treatment in ophthalmology

Photodynamic therapy (PDT) with verteporfin is a new treatment modality in ophthalmology that has previously shown its effectiveness in treatment of a variety of neoplastic pathologies. In this therapeutic approach, the photosensitizer verteporfin is activated by non-thermal laser light to obtain closure of neovascular structures. Preclinical and clinical studies have indicated that PDT is a safe, selective, and effective treatment for choroidal neovascularization in age-related macular degeneration. No significant damage to the neurosensory retina was found, which explains why PDT does not cause loss of visual acuity and may be used in a larger population than laser photocoagulation. This review summarizes the mechanisms of action of PDT, and the results of preclinical and clinical studies in ophthalmology.

Verteporfin : a review of its use in the management of subfoveal choroidal neovascularisation

Verteporfin (Visudyne) therapy (photodynamic therapy with intravenous liposomal verteporfin) is the first treatment to effectively prevent the loss of visual acuity in patients with subfoveal choroidal neovascularisation (CNV) secondary to age-related macular degeneration (AMD), pathological myopia or presumed ocular histoplasmosis syndrome (POHS). In adult patients with classic subfoveal CNV or occult with no classic subfoveal CNV secondary to AMD, or subfoveal CNV secondary to pathological myopia or POHS, verteporfin therapy slows or prevents loss of visual acuity. In well designed clinical trials, verteporfin therapy was superior to placebo in patients with subfoveal classic-containing CNV and occult with no classic CNV secondary to AMD at 12 and/or 24 months (Treatment of Age-related macular degeneration with Photodynamic therapy [TAP] Investigation and Verteporfin In Photodynamic therapy [VIP-AMD] trial) and in patients with pathological myopia at 12 months (Verteporfin In Photodynamic therapy [VIP-PM] trial). Limited data suggest that verteporfin therapy also prevents loss of visual acuity in patients with subfoveal CNV secondary to POHS. Verteporfin therapy was generally well tolerated in clinical trials; most adverse events were mild to moderate in intensity and transient. The most frequently reported verteporfin therapy-related adverse events (incidence >2%) were visual disturbance, injection-site reactions, photosensitivity reactions and infusion-related back pain. Approximately 5% of patients with occult with no classic subfoveal CNV secondary to AMD reported severe vision decrease within 7 days of treatment in clinical trials; 3 months later, several patients had recovered some of this loss.

CONCLUSION

Photodynamic therapy with verteporfin, the first photosensitiser approved for the treatment of subfoveal CNV, is a well tolerated treatment that stabilises or slows visual acuity loss in adult patients with predominantly classic or occult with no classic subfoveal CNV secondary to AMD, and subfoveal CNV secondary to pathological myopia or POHS. Thus, verteporfin therapy provides a valuable option for the management of these patients for whom treatment options are few, and should be considered as a first-line therapy in these difficult-to-manage conditions.

Thérapie photodynamique et DMLA : arguments pratiques sur la base de cas cliniques pour retraiter ou surveiller lors du suivi

Clinical and angiographic progression after photodynamic therapy (PDT) is usually slow, sometimes fluctuating and therefore difficult to evaluate. After several sessions of PDT, angiographic follow-up remains the basis for therapeutic management involving either a new PDT session or an alternative treatment. It remains difficult, however, to evaluate the activity and progression potential of the remaining neovessels. Imaging (angiography, optical coherence tomography) and functional data both contribute to the therapeutic decision. Certain patients require several sessions for a progressive reduction of the exudation. For others, the persistence of metamorphopsias and accentuation of the scotoma despite the treatment may entail alternative treatment. Thus, a perifoveal photocoagulation can be proposed to limit the extension of the scotoma if after a reasonable number of sessions, central visual acuity is not recovered; direct photocoagulation of a persistent active neovascular contingent, distant from the fixation zone (foveal or exenterated) can be proposed if it remains on the border of a stabilized lesion; the treatment of a feeder vessel can be proposed if it becomes visible and is associated with active neovessels with a persistent central serous detachment of the neuroretina. Lastly, performance status and patient wishes are important elements in the overall therapeutic project, especially if the eye involved is the second eye, in view of quickly initiating low-vision rehabilitation.

Photodynamic therapy for chronic central serous chorioretinopathy

PURPOSE

To determine whether photodynamic therapy (PDT) is effective for treatment of chronic central serous chorioretinopathy (CSC).

METHODS

Sixteen eyes with chronic CSC and macular detachment documented by optical coherence tomography (OCT) received PDT guided by indocyanine green (ICG) angiography according to the parameters outlined in the TAP Study. One or more laser spots were applied to the areas of choroidal vascular hyperpermeability that corresponded to retinal pigment epithelium decompensation. Patients were observed for 6 to 12 months. Two PDT sessions 1 month apart were performed on 2 eyes. Examinations included visual acuity measurement, fundus biomicroscopy, fluorescein and ICG angiography, and OCT.

RESULTS

Macular exudation resolved completely in 13 eyes (81%) and partially regressed in 3. Choriocapillaris hypoperfusion was shown by ICG angiography for several months at the site of PDT application. Visual acuity improved 1 to 4 lines in 11 eyes and was unchanged in 5 eyes.

CONCLUSIONS

ICG-guided PDT performed according to the parameters outlined by the TAP Study seems effective for treating chronic CSC. Further studies are needed to verify treatment safety and the time and rate of recurrences.

The changes of multifocal electroretinography in the early stage of photodynamic therapy for choroidal neovascularization

To investigate short-term changes in the multifocal electroretinography (ERG) recordings after photodynamic therapy (PDT) for choroidal neovascularization (CNV), 16 patients (17 eyes) with classic CNV confirmed by fluorescein angiography (FA) and indocyanine green angiography (ICGA), including 11 cases (12 eyes) of exudative age-related macular degeneration (AMD), two cases (two eyes) of pathological myopia and three cases (three eyes) of idiopathic causes, were treated using PDT with verteporfin. The multifocal ERGs of these patients were tested with VERIS Science 4.0 imaging system. The latencies and average response densities of all six ring retinal regions were measured and compared before PDT and 3 or 7 days after PDT. The latencies and amplitude densities of the N1 and P1 waves in all six rings remained unchanged at 3 or 7 days post-treatment (p > 0.05). Therefore, there is no significant evidence to suggest an adverse effect from PDT for classic CNV on the outer retinal function in the early stage of treatment, with the aid of the multifocal ERG recordings.

Comparative study of the phototoxicity of two chrolin type photosensitizers, ATX-S10(Na) and verteporfin, on vascular endothelial and retinal pigment epithelial cells

BACKGROUND AND OBJECTIVES

To compare the phototoxicity in photodynamic therapy (PDT) of ATX-S10(Na) and Verteporfin on human microvascular endothelial cells (HMVEC), vascular endothelial cells of monkey choroid and retina (CRVEC), and human retinal pigment epithelial cells (HRPE).

STUDY DESIGN/MATERIALS AND METHODS

PDT was performed in two different ways. In short dye-exposure PDT, HMVEC and CRVEC were exposed to each photosensitizer for 5 minutes followed by laser irradiation of 670 nm wavelength for ATX-S10(Na) or 689 nm for Verteporfin without washing out the photosensitizer in the medium. In long dye-exposure PDT, the cells were exposed to photosensitizers for times ranging from 5 minutes to 2 hours, washed out the photosensitizers, followed by laser irradiation in a fresh medium. PDT was performed on HRPE with PDT doses that resulted in damaging 90% of the HMVEC (ED(90)). Phototoxicity was determined by MTS Assay 1 day after PDT.

RESULTS

The degree of phototoxicity depended on the dye concentration, laser dose, and dye exposure time. In short dye-exposure PDT on HMVEC with a laser dose of 50 J/cm(2), the ED(90) was 6.3 microg/ml of ATX-S10(Na) and 0.04 microg/ml of Verteporfin, while in long dye-exposure PDT the ED(90) was 50.0 microg/ml of ATX-S10(Na) and 0.04 microg/ml of Verteporfin when the medium was supplemented with 5% fetal calf serum. The phototoxic rate on HMVEC was higher when the medium contained 5% as contrasted with 10% of serum. In short dye-exposure PDT, the ED(90) of CRVEC was 100 microg/ml of ATX-S10(Na) and an irradiance of 100 J/cm(2), and 0.08 microg/ml of Verteporfin and an irradiance of 100 J/cm(2) when the medium was supplemented with 10% serum. With some doses of short dye-exposure PDT, the ATX-S10(Na) achieved higher phototoxic rates on HMVEC and CRVEC than on the HRPE. However, long dye-exposure PDT with ATX-S10(Na) and short and long dye-exposure PDT with Vereteporfin failed to obtain higher phototoxic rates on HMVEC and CRVEC than on HRPE.

CONCLUSIONS

Verteporfin had a higher phototoxicity than ATX-S10(Na) on HMVEC and CRVEC. The CRVEC resisted more than HMVEC following PDT with both photosensitizers. In short dye-exposure PDT, ATX-S10(Na) had a more selective phototoxicity on HMVEC and CRVEC than on HRPE.

Treatment of rubeosis iridis with photodynamic therapy with verteporfin--A new therapeutic and prophylactic option for patients with the risk of neovascular glaucoma?

Patients with ischaemic retinopathy who show iris neovascularization despite panretinal laser photocoagulation (PRP) very often develop a neovascular glaucoma. Photodynamic therapy (PDT) has been shown to occlude neovascularization without damage to physiologic vessels or adjacent tissue in the treatment of choroidal neovascularization (CNV) and might also be of value for patients with neovascular glaucoma who did not benefit from the PRP. First results of a monocentre, open label, intra-individual controlled, pilot phase I/II, dose-finding study demonstrate that PDT with verteporfin is capable of occluding neovascular vessels for a defined period of time without damaging adjacent tissue or physiologic iris vessels. Whether this vessel occlusion will have an impact on the progression of rubeosis or neovascular glaucoma will be the subject of further investigation.

Uptake and localisation of mTHPC (Foscan) and its 14C-labelled form in normal and tumour tissues of the hamster squamous cell carcinoma model: a comparative study

The aim of this study was to evaluate the pharmacokinetics of meta(tetrahydroxyphenyl)chlorin (mTHPC) on different tissues of interest in a hamster tumour model and to confirm our earlier animal studies on semi-quantitative fluorescence microscopy. The results obtained by three different evaluation methods were compared: in vivo spectrofluorometry, ex vivo fluorescence microscopy and chemical extraction of (14)C-labelled mTHPC. Following intracardiac injection of 0.5 mg kg(-1) mTHPC, groups of five tumour-bearing animals were used for in situ light-induced fluorescence spectroscopy. Afterwards, the biopsies were taken and snap frozen for fluorescence microscopy. The presence of radioactivity in serum and tissues was determined after chemical digestion in scintillation fluid using a scintillation counter. For each analysed tissue, a good correlation was observed between the three evaluation methods. The highest fluorescence intensity and quantities of mTHPC were observed between 12 and 24 h in liver, kidney, serum, vascular endothelium and advanced neoplasia. The majority of mTHPC was found at around 48 h in smooth muscle and at 96 h in healthy cheek pouch mucosa and early malignant lesions. The lowest level of mTHPC was noted in striated muscle at all times. No selectivity in dye localisation was observed between early squamous cell carcinoma and healthy mucosa. Soon after the injection, a significant selectivity was noted for advanced squamous cell carcinoma as compared to healthy cheek pouch mucosa or striated muscle. A significant difference in mTHPC localisation and quantity was also observed between striated and smooth muscle during the first 48 h following the injection. Finally, this study demonstrated the usefulness of non-invasive in situ spectroscopic measurements to be performed systematically prior to photodynamic therapy as a real-time monitoring for each treated patient in order to individualise and adapt the light dosimetry and avoid over or under treatments.

Photodynamic therapy for choroidal neovascularization: a review

PURPOSE

To review the biophysical basis and current state of therapy for photodynamic closure of subfoveal choroidal neovascularization in the eye.

METHODS

A review of the literature is included, which encompasses the chemical structure, biophysical mechanism of action, range of available agents, status of clinical trials, clinical indications, results of treatments, complications, and future directions.

RESULTS

Photodynamic therapy has been shown to be effective in closing both experimental choroidal neovascularization in animal models as well as subfoveal choroidal neovascularization in humans. The therapy results in temporary closure of choroidal new vessels for a period of approximately 1 to 4 weeks. By 12 weeks, most patients have reperfusion or reproliferation of choroidal new vessels resulting in the need for retreatment to achieve continued closure and visual stabilization. Differences exist in the quantum yield, clinical efficiency, and light and sensitizer dose requirements between different classes of agents. Further clinical trials will be required to determine the optimal form of therapy, with verteporfin (Visudyne) as the only currently approved agent. Other agents, including tin etiopurpurin (Purlytin) and motexafin lutetium (Optrin), are currently undergoing phase III, and phase II trials, respectively.

CONCLUSIONS

Photodynamic therapy is a promising treatment modality shown to be effective in achieving closure and stabilization of vision loss compared with placebo control in eyes with subfoveal choroidal neovascularization.

Localization of rose bengal, aluminum phthalocyanine tetrasulfonate, and chlorin e6 in the rabbit eye

PURPOSE

The localization and site of action of photosensitizers in the eye may be important for photodynamic therapy for fundus disorders but remain poorly understood for most agents. We investigated the intraocular localization of xanthene, phthalocyanine, and chlorin photosensitizers by using fluorescence microscopy and digital fundus fluorescence angiography.

METHODS

Rose bengal (40 mg/kg), aluminum phthalocyanine tetrasulfonate (CASPc) (5 mg/kg), or chlorin e6 (2 mg/kg) was intravenously administered to albino rabbits. The eyes were enucleated and examined by means of fluorescence microscopy 5, 20, 60, and 120 minutes and 24 hours after dye injection. In vivo digital fundus fluorescence angiography with use of rose bengal (2-4 mg/kg), CASPc (2 mg/kg), and chlorin e6 (2 mg/kg) was performed.

RESULTS

For all agents studied pathologically, there was moderate fluorescence from the choroid and retinal pigment epithelium 5 minutes after dye injection. Mild fluorescence detected from the photoreceptor outer segments at 5 minutes was increased at 20 minutes. Angiographic studies with use of rose bengal, CASPc, and chlorin e6 revealed differences in the pattern and rate of photosensitizer accumulation.

CONCLUSIONS

Rose bengal, CASPc, and chlorin e6 accumulate rapidly in the choroid and retinal pigment epithelium and less rapidly in the outer retina. Differences in ocular localization of these photosensitizers were demonstrated. The significance of these findings for potential photodynamic therapy with these agents requires further investigation.

Mechanisms of action of photodynamic therapy with verteporfin for the treatment of age-related macular degeneration

Age-related macular degeneration, especially the neovascular form of the disease, is the leading cause of blindness in elderly people in developed countries. Thermal photocoagulation is still the preferred treatment for choroidal neovascularization that does not involve the fovea, but it is suitable for only a small number of patients and it can lead to immediate loss of visual acuity. Photodynamic therapy with use of photochemical light activation of verteporfin as a photosensitizer (verteporfin therapy) has been shown to be effective in treating vascularized tumors, and its potential to treat other conditions involving neovascularization has also been suggested. Preclinical and clinical studies have indicated that verteporfin therapy can be used to treat choroidal neovascularization secondary to age-related macular degeneration effectively and safely. Selective occlusion of choroidal neovasculature by this therapy causes minimal damage to the neurosensory retina and, therefore, does not induce loss of visual acuity. This benefit allows verteporfin therapy to be used in the large proportion of patients who are not eligible for treatment by laser photocoagulation. The mechanistic aspects of the mode of action of light-activated verteporfin are described in this review.

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.

Highly fluorescent protein labeling using dendritic peptide derivatives

Non-specific fluorescent dyes and photosensitizers are routinely used in clinical practice for the photodetection and photoablation of superficial lesions. Future applications in photomedicine are likely to rely on the selective delivery of photoactive compounds to diseased areas, using specific targeting agents such as antibodies. This fact underlines the need for methods that allow the chemically defined conjugation of several photoactive molecules to a single protein 'vehicle', with full retention of binding affinity. Here, we present methods for the site-specific fluorescent labeling of proteins using dendritic peptides, which had been chemically modified with multiple molecules of fluorescein. Branched peptide derivatives can be stably conjugated to proteins either by reaction with suitable free reactive groups or by using the high-affinity non-covalent interaction between calmodulin and a specific binding peptide. Chemical modification of proteins with one, two or four molecules of fluorescein resulted in a proportional increase in protein fluorescence.

Lutetium texaphyrin (Lu-Tex): a potential new agent for ocular fundus angiography and photodynamic therapy

PURPOSE

To investigate the suitability of lutetium texaphyrin (lu-tex) as a fluorescence imaging agent in the delineation of retinal vascular and choroidal vascular diseases. The utilization of an efficient fluorescent molecule that is also a photosensitizer represents a unique opportunity to couple diagnosis and therapy.

METHODS

Fundus fluorescence angiography comparing lu-tex (motexafin lutetium, Optrin, Pharmacyclics Inc, Sunnyvale, California) with the conventional angiographic dyes, sodium fluorescein, and indocynanine green (ICG), was performed on the eyes of normal and laser-injured New Zealand white rabbits. Plasma pharmacokinetic data and plasma protein binding were assessed in addition to light microscopy of the retina in both imaged and laser-injured eyes.

RESULTS

Normal retinal and choroidal vasculature was well delineated by lu-tex angiography. Experimentally induced choroidal and retinal vascular lesions were enhanced by lu-tex and demonstrated different staining patterns than fluorescein or ICG, particularly at the margins of the lesions. Lu-tex cleared rapidly from the plasma, with 39.7% bound to the high-density lipoprotein (HDL) fraction while 15.8% was bound to the low-density lipoprotein (LDL) fraction. No evidence of retinal toxicity after dye administration was observed by either ophthalmoscopy and fundus photography or by light microscopy.

CONCLUSION

Lu-tex angiography is a potentially valuable method for retinal vascular and choroidal vascular evaluation, and it has advantages over fluorescein and ICG angiography. The same agent could conceivably be used for both the identification of abnormal vasculature and subsequent photodynamic treatment.

Selective targeting and photocoagulation of ocular angiogenesis mediated by a phage-derived human antibody fragment

Molecules that selectively target and occlude new blood vessels would be useful for diagnosis and treatment of pathologies associated with angiogenesis. We show that a phage-derived human antibody fragment (L19) with high affinity for the ED-B domain of fibronectin, a marker of angiogenesis, selectively localizes to newly formed blood vessels in a rabbit model of ocular angiogenesis. The L19 antibody, chemically coupled to a photosensitizer and irradiated with red light, mediates complete and selective occlusion of ocular neovasculature and promotes apoptosis of the corresponding endothelial cells. These results demonstrate that new ocular blood vessels can be distinguished immunochemically from preexisting ones and suggest that the targeted delivery of photosensitizers may be effective in treating angiogenesis-related pathologies.

Analysis of acute vascular damage after photodynamic therapy using benzoporphyrin derivative (BPD)

Benzoporphyrin derivative monoacid ring A (BPD-MA, verteporfin) is currently under investigation as a photosensitizer for photodynamic therapy (PDT). Since BPD exhibits rapid pharmacokinetics in plasma and tissues, we assessed damage to tumour and muscle microvasculature when light treatment for PDT was given at short times after injection of photosensitizer. Groups of rats with chondrosarcoma were given 2 mg kg(-1) of BPD intravenously 5 min to 180 min before light treatment of 150 J cm(-2) 690 nm. Vascular response was monitored using intravital microscopy and tumour cure was monitored by following regrowth over 42 days. For treatment at 5 or 30 min after BPD injection, blood flow stasis was limited to tumour microvasculature with lesser response in the surrounding normal microvasculature, indicating selective targeting for damage. No acute changes were observed in vessels when light was given 180 min after BPD injection. Tumour regression after light treatment occurred in all animals given PDT with BPD. Long-term tumour regression was greater in animals treated 5 min after BPD injection and least in animals given treatment 180 min after drug injection. The correlation between the timing for vascular damage and cure implies that blood flow stasis plays a significant role in PDT-induced tumour destruction.

Age-related macular degeneration: a review of experimental treatments

Age-related macular degeneration (AMD) is the leading cause of irreversible visual loss in the USA. Laser photocoagulation of choroidal neovascular membranes (CNVMs) in exudative AMD is currently the only well-studied and widely accepted treatment modality. It is beneficial for only a small minority of patients who show well-demarcated "classic" CNVMs, and it destroys normal retinal tissue, creates a scotoma, and is associated with an unacceptably high CNVM persistence and recurrence rate. Consequently, investigators have attempted to develop new modalities for treatment of CNVMs. These treatment modalities can be grouped into four major categories: photodynamic therapy; pharmacologic inhibition of CNVM formation with antiangiogenic agents; surgical intervention, including excision of subfoveal CNVMs; and radiation therapy. All of these experimental treatment modalities are directed toward destroyiing CNVMs, the end result of the exudative process, and all have limitations. The ideal treatment of the future must be based on the pathogenesis of the disease at a stage well before CNVMs develop. Investigations in nonexudative AMD are currently focusing on several major areas. Epidemiologic factors, such as genetics, sunlight, and nutrition, are being evaluated in several large studies, including the Age-Related Eye Disease Study, with the possibility of ultimately limiting the risk of AMD through behavior modification. Laser treatment of drusen is being evaluated as a means of limiting the risk of CNVM formation, although mixed results have been reported in the small number of studies to date. Choroidal perfusion abnormalities have been described in AMD, and some investigators postulate that altering blood flow may limit the risk of CNVM formation. No perfusion-treatment trials have been completed to date.