Argon laser photodynamic therapy of human corneal neovascularization after intravenous administration of dihematoporphyrin ether

Up-to-date molecular medicine strategies for management of ocular surface neovascularization

Ocular surface neovascularization and its resulting pathological changes significantly alter corneal refraction and obstruct the light path to the retina, and hence is a major cause of vision loss. Various factors such as infection, irritation, trauma, dry eye, and ocular surface surgery trigger neovascularization via angiogenesis and lymphangiogenesis dependent on VEGF-related and alternative mechanisms. Recent advances in antiangiogenic drugs, nanotechnology, gene therapy, surgical equipment and techniques, animal models, and drug delivery strategies have provided a range of novel therapeutic options for the treatment of ocular surface neovascularization. In this review article, we comprehensively discuss the etiology and mechanisms of corneal neovascularization and other types of ocular surface neovascularization, as well as emerging animal models and drug delivery strategies that facilitate its management.

Photodynamic Therapy for Infectious Keratitis

Infectious keratitis is a sight-threatening microbial infection. The prevalence of antimicrobial resistance in cases of infectious keratitis has increased the demand for fortified compounded antimicrobial drops. Even with proper medical management, severe cases of infectious keratitis can further evolve into corneal perforation, requiring surgical intervention in the form of keratoplasty to control the infectious process. Due to the invasive nature of the procedure and the shortage of available donor tissue around the world, alternative treatments are needed for the management of progressive infectious keratitis. In ophthalmology, photodynamic therapy (PDT) has been used for numerous applications. PDT with Rose Bengal as a photosensitizer combined with green light optical irradiation (RB-PDAT) is a novel treatment with dual purpose: to arrest the infection from progressing and strengthen the collagen of the cornea. RB-PDAT may be considered as an adjunct therapy in severe cases of infectious keratitis to minimize the need for a therapeutic keratoplasty.

Effects of VEGF Inhibitor Conbercept on Corneal Neovascularization Following Penetrating Keratoplasty in Rabbit Model

Purpose

To evaluate the effects of the vascular endothelial growth factor inhibitor conbercept (KH902) on corneal neovascularization and wound healing following penetrating keratoplasty in rabbits.

Methods

Conbercept was administered to New Zealand white rabbits through topical and subconjunctival routes. Corneal neovascularization and wound healing were examined by slit-lamp photography and histological analyses. The expressions of vascular endothelial growth factor inhibitor, α-smooth muscle actin, and keratocan in the corneal grafts were measured by real-time quantitative polymerase chain reaction (RT-qPCR).

Results

The anterior segment photographs demonstrated that corneal neovascularization started in the 2nd week. In the 4th week, histologically, the superficial corneal stroma layer showed disordered arrangement, and there were large numbers of dense inflammatory cells and blood vessels in the stroma layer. Vascular endothelial growth factor in the experimental groups was significantly decreased at all time points compared with the control group (both P = 0.001). Expression of α-smooth muscle actin in corneal grafts demonstrated an increase in time even it was lower in experimental groups, but the difference was not statistically significant (P equaled to 0.507 and 0.723, respectively). There were no significant differences with the expression of keratocan in all groups except that it significantly declined at the 4th week as to the second week in all groups and P values were 0.022, 0.020 and 0.014 in control (C), topical (E1), and subconjunctival (E2) group, respectively.

Conclusion

The study found that conbercept inhibited the formation of corneal neovascularization without affecting keratocan-mediated corneal wound healing and there were no significant differences between topical administration of different doses of conbercept on the rabbit corneal neovascularization after penetrating keratoplasty in this study.

Risk of Corneal Graft Rejection After High-risk Keratoplasty Following Fine-needle Vessel Coagulation of Corneal Neovascularization Combined With Bevacizumab: A Pilot Study

Background

Corneal neovascularization is considered an important risk factor for allograft rejection after corneal transplantation (keratoplasty). Therefore, the aim of this study was to determine whether preoperative reduction of corneal neovascularization by fine-needle thermal cauterization combined with bevacizumab reduces the incidence of allograft rejection after subsequent high-risk keratoplasty.

Methods

In this interventional uncontrolled clinical pilot study, 31 eyes of 31 patients with corneal neovascularization in at least one corneal quadrant were included. All eyes were treated by fine-needle thermal cauterization of corneal vessels and subconjunctival injection of bevacizumab. Both treatments were repeated in the cases of visible reperfusion of occluded vessels. Afterward, penetrating keratoplasty was performed. When corneal neovascularization was present on the day of keratoplasty, additional vessel cauterization and injection of bevacizumab was performed. Patients were then followed to determine the incidence of allograft rejection.

Results

In 18 eyes, vessel cauterization with bevacizumab injection was performed once before keratoplasty, whereas 13 eyes required retreatment before keratoplasty. No complications were observed. In 23 eyes, corneal neovascularization was present on the day of keratoplasty due to reperfusion of previously occluded vessels and simultaneous vessel cauterization with bevacizumab injection was performed. During follow-up (mean: 560 days; range: 59-1095 days), 4 graft rejection episodes in 4 eyes were observed. Estimated probabilities of corneal graft survival were 92.9% after 1 year (number at risk: 23), 78.4% after 2 years (number at risk: 9), and 78.4% after 3 years (number at risk: 3).

Conclusions

Our initial results indicate that angioregressive treatment of pathological corneal vessels by fine-needle thermal cauterization combined with subconjunctival injection of bevacizumab before high-risk keratoplasty seems to result in graft survival rates comparable to survival rates seen in normal-risk keratoplasty. The findings of our pilot study warrant further controlled clinical trials with longer follow-up in a larger patient cohort.

Current and emerging therapies for corneal neovascularization

The cornea is unique because of its complete avascularity. Corneal neovascularization (CNV) can result from a variety of etiologies including contact lens wear; corneal infections; and ocular surface diseases due to inflammation, chemical injury, and limbal stem cell deficiency. Management is focused primarily on the etiology and pathophysiology causing the CNV and involves medical and surgical options. Because inflammation is a key factor in the pathophysiology of CNV, corticosteroids and other anti-inflammatory medications remain the mainstay of treatment. Anti-VEGF therapies are gaining popularity to prevent CNV in a number of etiologies. Surgical options including vessel occlusion and ocular surface reconstruction are other options depending on etiology and response to medical therapy. Future therapies should provide more effective treatment options for the management of CNV.

Therapeutic approaches for corneal neovascularization

Angiogenesis refers to new blood vessels that originate from pre-existing vascular structures. Corneal neovascularization which can lead to compromised visual acuity occurs in a wide variety of corneal pathologies. A large subset of measures has been advocated to prevent and/or treat corneal neovascularization with varying degrees of success. These approaches include topical corticosteroid administration, laser treatment, cautery, and fine needle diathermy. Since the imbalance between proangiogenic agents and antiangiogenic agents primarily mediate the process of corneal neovascularization, recent therapies are intended to disrupt the different steps in the synthesis and actions of proangiogenic factors. These approaches, however, are only partially effective and may lead to several side effects. The aim of this article is to review the most relevant treatments for corneal neovascularization available so far.

Role of Frequency Doubled Nd: Yag Laser in Treatment of Corneal Neovascularisation

INTRODUCTION

Cornea is the outermost transparent coat of eye along with sclera, for which its avascularity is essential for maintaining its transparency to have normal visual acuity. Corneal neovascularization is characterized by the invasion of new blood vessels into the cornea from the limbus interfering with corneal transparency, resulting in reduction in visual acuity. It also increases the risk of graft rejection. So their being a dire need to treat corneal neovascularisation, with laser photocoagulation being an effective means of treating it.

AIM

To evaluate the efficacy and safety of frequency doubled Nd:Yag laser photocoagulation in treatment of corneal neovascularisation.

MATERIALS AND METHODS

A single centre prospective study was carried out on patients attending the outpatient department of ophthalmology in Maharani Laxmi Bai Medical College, Jhansi. Forty eyes of 40 patients having corneal neovascularisation with quiescent eyes satisfying the inclusion criteria were selected and treated with laser. The efficacy of the procedure was noted in terms of area of corneal neovascularisation, status of treated vessels, area of corneal opacity, visual acuity. The above parameters of selected patients were recorded before treatment and subsequent follow up visits at 1 week, 1 month, 2 month and 3 month after laser. Paired t-test was used to calculate the p-value.

RESULTS

There was a statistically significant difference in the percentage mean area of corneal neovascularisation with a pre laser value of 31.93% to 17.62% after 3 months of laser treatment (p-value<0.0001). The percentage mean area of corneal opacity decreased from 30.75% to 23.74% (p<0.0001). Out of 185 corneal vessels, 99 (53.51%) vessels were completely occluded,17(9.18%) vessels were partially occluded and 69(37.29%) vessels were recanalised at the end of 3 months after laser treatment.

CONCLUSION

Frequency doubled Nd:Yag laser is an effective and safe method for the treatment of corneal neovascularisation.

[Current treatments for corneal neovascularization]

The extension of blood vessels into the normally avascular stroma defines corneal neovascularization. Though this phenomenon, pathophysiological and clinical features are well characterized, therapeutic modalities have been hindered by a lack of safe, efficacious and non-controversial treatments. In this literature review, we focus on available therapeutic options in light of recent evidence provided by animal and clinical studies. First, this review will focus on pharmacological treatments that target angiogenesis. The low cost and market availability of bevacizumab make it the first anti-angiogenic therapy choice, and it has demonstrable efficacy in reducing corneal neovascularization when administered topically or subconjunctivally. However, novel anti-angiogenic molecules targeting the intracellular pathways of angiogenesis (siRNA, antisense oligonucleotides) provide a promising alternative. Laser therapy (direct photocoagulation or photo-dynamic therapy) and fine needle diathermy also find a place in the treatment of stabilized corneal neovascularization alone or in association with anti-angiogenic therapy. Additionally, ocular surface reconstruction using amniotic membrane graft or limbal stem cell transplantation is essential when corneal neovascularization is secondary to primary or acquired limbal deficiency.

Assessment of rose bengal versus riboflavin photodynamic therapy for inhibition of fungal keratitis isolates

PURPOSE

To compare the in vitro effect of rose bengal and riboflavin as photosensitizing agents for photodynamic therapy (PDT) on fungal isolates that are common causes of fungal keratitis.

DESIGN

Experimental study.

METHODS

Three isolates (Fusarium solani, Aspergillus fumigatus, Candida albicans) recovered from patients with confirmed fungal keratitis were used in the experiments. Isolates were grown on Sabouraud-Dextrose agar, swabbed, and prepared in suspension, and 1 mL aliquots were inoculated onto test plates in triplicate. Test plates were separated into 5 groups: Group 1, no treatment; Group 2, 0.1% rose bengal alone; Group 3, 518 nm irradiation alone; Group 4, riboflavin PDT (riboflavin + 375 nm irradiation); and Group 5, rose bengal PDT (rose bengal + 518 nm irradiation). Irradiation was performed over a circular area using either a green light-emitting diode (LED) array (peak wavelength: 518 nm) or an ultraviolet-A LED array (peak wavelength: 375 nm). Test plates were irradiated with an energy density of 5.4 J/cm(2). Later, plates were placed in a 30 C incubator and observed for growth.

RESULTS

Rose bengal-mediated PDT successfully inhibited the growth of all 3 fungal isolates in the irradiated area. All other groups exhibited unrestricted growth throughout the plate.

CONCLUSIONS

Rose bengal-mediated PDT successfully inhibited the growth of 3 types of fungi. No other experimental groups, including riboflavin-mediated PDT, had any inhibitory effect on the isolates. The results might be useful for the treatment of patients suffering from corneal infection.

Topical ranibizumab as a treatment of corneal neovascularization

PURPOSE

To examine the effect of topical ranibizumab on clinically stable corneal neovascularization (NV).

METHODS

This was a prospective, open-label, monocentric, uncontrolled noncomparative study. Ten eyes of 9 patients with corneal NV received topical ranibizumab (1%) 4 times a day for 3 weeks with a follow-up period of 16 weeks. The main corneal NV outcome measures were: neovascular area, the area occupied by the corneal neovessels; vessel caliber (VC), the mean diameter of the corneal neovessels; and invasion area (IA), the fraction of the total cornea area covered by the vessels. This study was conducted at the Massachusetts Eye and Ear Infirmary, Boston, MA.

RESULTS

Statistically significant decreases in neovascular area (55.3%, P < 0.001), which lasted through 16 weeks, and VC (59%, P < 0.001), which continued to improve up to week 16, were observed after treatment. No significant decrease was observed in IA (12.3%, P = 0.49). There was no statistically significant change in visual acuity or intraocular pressure. No adverse events ascribed to the treatment were noted.

CONCLUSIONS

Topical application of ranibizumab is effective in reducing the severity of corneal NV in the context of established corneal NV, mostly through decrease in VC rather than IA.

Corneal neovascularization and the utility of topical VEGF inhibition: ranibizumab (Lucentis) vs bevacizumab (Avastin)

Corneal avascularity is necessary for the preservation of optimal vision. The cornea maintains a dynamic balance between pro- and antiangiogenic factors that allows it to remain avascular under normal homeostatic conditions; however, corneal avascularity can be compromised by pathologic conditions that negate the cornea's "angiogenic privilege." The clinical relevance of corneal neovascularization has long been recognized, but management of this condition has been hindered by a lack of safe and effective therapeutic modalities. Herein, the etiology, epidemiology, pathogenesis, and treatment of corneal neovascularization are reviewed. Additionally, the authors' recent findings regarding the clinical utility of topical ranibizumab (Lucentis®) and bevacizumab (Avastin®) in the treatment of corneal neovascularization are summarized. These findings clearly indicate that ranibizumab and bevacizumab are safe and effective treatments for corneal neovascularization when appropriate precautions are observed. Although direct comparisons are not conclusive, the results suggest that ranibizumab may be modestly superior to bevacizumab in terms of both onset of action and degree of efficacy. In order to justify the increased cost of ranibizumab, it will be necessary to demonstrate meaningful treatment superiority in a prospective, randomized, head-to-head comparison study.

Treatments for corneal neovascularization: a review

Corneal neovascularization (CNV) may be a physiological response to various stimuli, but a chronic and persistent upregulation of neoangiogenesis can result in pathological CNV. Pathological blood vessels are immature and lack structural integrity, predisposing the cornea to lipid exudation, inflammation, and scarring. CNV can therefore become a potentially blinding condition. In this review, we frame CNV in an epidemiological perspective, consider risk factors for CNV, provide an overview of CNV pathogenesis, and consider the impact of CNV on corneal transplantation. We consider treatments that are of largely historical interest, before reviewing contemporary medical and surgical treatments. Within medical treatments, we report on steroids, nonsteroidal anti-inflammatory agents, antivascular endothelial growth factor agents, and cyclosporine. Within surgical treatments, we report on the use of lasers, photodynamic therapy, superficial keratectomy, and diathermy/cautery-based treatments.

Horizons in therapy for corneal angiogenesis

Corneal neovascularization can lead to a devastating disease process that involves the breakdown of the limbal barrier and the formation of blood vessels in the cornea, leading to severe visual impairment. This review discusses the delicate balance between antiangiogenic and angiogenic factors that govern the antiangiogenic privilege of the cornea. Current treatment methods, clinical trials, and future prospects in the management of corneal neovascularization also are discussed.

Resolution of bilateral corneal neovascularization and lipid keratopathy after photodynamic therapy with verteporfin

PURPOSE

The aim of this study was to describe the result of photodynamic therapy with verteporfin (Visudyne(®), Novartis Ophthalmics AG, Hettingen, Switzerland) on bilateral corneal neovascularization (CN) and lipid keratopathy.

METHODS

A 36-year-old man with bilateral CN and visually significant lipid keratopathy presented to the King Khaled Eye Specialist Hospital with decreased visual acuity in both eyes; bilateral refractive surgery had been done several years before. He was wearing hard contact lenses and had a history of repeated keratitis in both eyes. Eyes were treated with nonthermal laser light at 689 nm delivered 15 minutes after an intravenous infusion of verteporfin, 6 mg/m(2) of body surface area, which was repeated 2 months after his first session. He was followed up regularly for 4 years with ophthalmic examinations and photographic documentation.

RESULTS

Successful occlusion of the CN was observed by the third month, and a dramatic resorption of lipid keratopathy was noticed by the end of the first year in both eyes. Best-corrected visual acuities improved from 20/80 in the right eye and 20/100 in the left eye to 20/30 with each eye. During the 4-year follow-up period, neither recurrence nor complications of the treatment was observed.

CONCLUSIONS

Laser therapy with verteporfin can be added to the armamentarium of treatments for CN as a safe and effective option.

Ophthalmic light sensitive nanocarrier systems

The eye is afflicted by chronic vision debilitating neovascular disorders, such as age-related macular degeneration, proliferative diabetic retinopathy, and corneal angiogenesis. Photodynamic therapy (PDT) is an innovative, evolving approach for treating neovascular diseases of the eye. PDT refers to the process of activating a light sensitive agent or carrier with non-thermal light to induce chemical reactions that ameliorate a pathological condition. Key components of PDT include a photosensitizer, a colloidal carrier or formulation and a light source. This article summarizes currently available clinical PDTs, desirable features of PDTs and photosensitizers, useful light sources for PDT and investigational nanosystems, and colloidal carriers for PDT.

Photodynamic therapy with verteporfin for corneal neovascularization

PURPOSE

To investigate the efficacy of photodynamic therapy with verteporfin for the treatment of patients with corneal neovascularization.

DESIGN

Prospective interventional case series.

METHODS

Eighteen eyes of 18 patients with stable corneal neovascularization who were refractory to conventional treatment were treated with photodynamic therapy with verteporfin (6 mg/m(2)). Five patients were treated following penetrating keratoplasty (PK), and two patients were treated before PK. Anterior segment photography was performed before and after treatment. Best-corrected visual acuity (BCVA) and area of corneal neovascularization were measured.

RESULTS

At the one-year follow-up, 14 eyes (77.8%) showed a decrease in corneal neovascularization, and nine eyes (50.0%) showed complete vascular occlusion. In five patients who had corneal allograft, complete or partial occlusion was achieved in all eyes. Two patients who underwent subsequent keratoplasty did not manifest allograft rejection or revascularization. Seventeen eyes (94.4%) had stable or improved vision. The mean area of corneal neovascularization significantly decreased from 25.5 +/- 14.2 mm(2) to 14.9 +/- 14.6 mm(2) (P < .01), respectively. No significant complications associated with photodynamic therapy were observed except mild stromal haze in one eye.

CONCLUSION

Photodynamic therapy with verteporfin may be effective for the treatment of corneal neovascularization.