Fluorescein-potentiated argon laser therapy improves symptoms and appearance of corneal neovascularization

Management of corneal neovascularization: Current and emerging therapeutic approaches

Corneal neovascularization (CoNV) is a sight-threatening condition affecting an estimated 1.4 million people per year, and the incidence is expected to rise. It is a complication of corneal pathological diseases such as infective keratitis, chemical burn, corneal limbal stem cell deficiency, mechanical trauma, and immunological rejection after keratoplasties. CoNV occurs due to a disequilibrium in proangiogenic and antiangiogenic mediators, involving a complex system of molecular interactions. Treatment of CoNV is challenging, and no therapy thus far has been curative. Anti-inflammatory agents such as corticosteroids are the mainstay of treatment due to their accessibility and well-studied safety profile. However, they have limited effectiveness and are unable to regress more mature neovascularization. With the advent of advanced imaging modalities and an expanding understanding of its pathogenesis, contemporary treatments targeting a wide array of molecular mechanisms and surgical options are gaining traction. This review aims to summarize evidence regarding conventional and emerging therapeutic options for CoNV.

Bilateral Lipid Keratopathy in the Setting of Brimonidine Tartrate Use

Lipid keratopathy (LK) is a rare disease involving lipid deposition in the cornea resulting in corneal opacification. Primary LK can arise sporadically while secondary LK is seen in patients with a history of ocular trauma, medication exposure, infection, inflammation, or disorders resulting in derangements of lipid metabolism. Secondary LK is more common and occurs due to neovascularization. Use of precipitating medications should be considered in LK workup, particularly for patients in whom other etiologies have been ruled out. Brimonidine, an ocular hypotensive medication, can be associated with LK. We present a case of bilateral secondary LK in a patient with a history of prolonged brimonidine use, without additional contributing factors.

Subconjunctival bevacizumab and argon laser photocoagulation for preexisting neovascularization following deep lamellar anterior keratoplasty

We report a rare case of deep anterior lamellar keratoplasty (DALK) neovascularization managed with combination of subconjunctival bevacizumab and argon laser photocoagulation. A 24 year old male underwent Deep anterior lamellar keratoplasty for corneal stromal opacity following presumed viral keratitis. Deep corneal neovascularization was observed postoperatively which was successfully managed using a combination of subconjunctival bevacizumab and argon laser photocoagulation within one week of DALK. The neovascularization resolved by 3 months and at 2 years follow up, patient maintained good visual acuity of 6/12 Snellen's without recurrence of vascularization. A combination of bevacizumab and argon laser may be an effective approach to manage neovascularisation in the immediate postoperative phase (Post DALK) and improve graft survival.

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.

SPONTANEOUS RESOLUTION OF MACULAR EPIRETINAL MEMBRANES AFTER FLUORESCEIN POTENTIATED ARGON LASER TREATMENT OF VON HIPPEL-LINDAU ASSOCIATED RETINAL HEMANGIOMAS: CASE REPORT AND REVIEW OF LITERATURE

PURPOSE

To illustrate spontaneous resolution of macular epiretinal membranes and inactivation of retinal hemangioma exudation after fluorescein potentiated argon laser treatment of bilateral capillary hemangiomas in a patient with a de novo heterozygous deletion in Exon 2 of the von Hippel-Lindau gene.

METHODS

Interventional case report.

RESULTS

A 23-year-old man with subjective complaints of blurry vision, photophobia, and glare. On presentation, visual acuity was 20/20 in the right eye and 20/25 in the left eye with metamorphopsia. On the basis of bilateral retinal hemangiomas on clinical examination and characterization with multimodal imaging, a diagnosis of von Hippel-Lindau disease was made. Genetic testing identified a de novo, disease-causing heterozygous deletion in Exon 2 of the von Hippel-Lindau gene. The patient underwent 4 sessions of fluorescein potentiated 532 nm argon green laser treatment directed at retinal hemangiomas. No adverse sequelae of laser treatment were noted. Seven months after the initial presentation, the patient's vision was 20/20 in both eyes with interval resolution of metamorphopsia. There was spontaneous resolution of a macular epiretinal membrane with normalization of the macular retinal microstructure. The retinal hemangiomas in both eyes appeared inactive, and no new lesions were noted.

CONCLUSION

Fluorescein potentiated argon laser successfully treated bilateral retinal hemangiomas in our patient with von Hippel-Lindau disease. Additional studies to characterize the full clinical potential of fluorescein potentiated argon laser therapy may be warranted.

Clinical correlates of common corneal neovascular diseases: a literature review

A large subset of corneal pathologies involves the formation of new blood and lymph vessels (neovascularization), leading to compromised visual acuity. This article aims to review the clinical causes and presentations of corneal neovascularization (CNV) by examining the mechanisms behind common CNV-related corneal pathologies, with a particular focus on herpes simplex stromal keratitis, contact lenses-induced keratitis and CNV secondary to keratoplasty. Moreover, we reviewed CNV in the context of different types of corneal transplantation and keratoprosthesis, and summarized the most relevant treatments available so far.

Argon laser phototherapy in the treatment of refractory fungal keratitis

PURPOSE

To report the beneficial properties of argon laser as an adjunctive therapy in 2 patients with refractory fungal keratitis.

METHODS

Case reports and a review of the literature. Two cases of Fusarium keratitis refractory to topical and systemic antifungals were further treated with argon laser. Before laser treatment, the eye was medicated with proparacaine 0.5%, lidocaine 4%, and a single drop of fluorescein sodium 0.25%. Argon laser irradiation of the affected cornea was performed using argon blue-green wavelength (Coherent Ultima 2000; Coherent, Inc). A spot size of 500 μm, pulse duration of 0.10 seconds, and power ranging from 500 to 900 mW were used.

RESULTS

During the first week after laser treatment, both patients showed complete resolution of the infiltrates. Two signs were observed during the procedure: a blanching of the corneal stroma and small cavitations that reached the middle stroma. No adverse effects were observed.

CONCLUSIONS

Argon laser phototherapy is useful as an adjunctive treatment of refractory fungal keratitis. More cases are needed to validate our findings.

Anti-VEGF therapy with bevacizumab for anterior segment eye disease

PURPOSE

To review the current literature concerning the use of bevacizumab in treating neovascular disorders affecting the anterior segment ocular structures.

METHODS

The authors reviewed the literature on anti-vascular endothelial growth factor (VEGF) therapy with bevacizumab for various anterior segment neovascular disorders that was indexed in MEDLINE (up to January 2011).

RESULTS

Response to bevacizumab anti-VEGF therapy is variable, based on the amount of scarring, the chronicity and extent of corneal neovascularization, the disease process, and the medication formulation and its route of administration. Anti-VEGF agents are especially effective when administered early, before anatomical changes, such as corneal neovascularization and/or angle closure, are established. Neovascularization can recur if the ischemic or inflammatory process is not reversed, so eyes with long-standing diseases, such as autoimmune disorders that involve ongoing inflammation and VEGF production, seem to be less responsive to bevacizumab anti-VEGF therapy. For established neovascularization, combining anti-VEGF agents with the removal of established vessels may be more effective than anti-VEGF therapy alone. Subconjunctival bevacizumab may be more appropriate for focal, deep, and peripheral neovascularization, whereas diffuse superficial neovascularization with central corneal involvement may be best treated via topical application.

CONCLUSIONS

Besides the widely accepted use of bevacizumab in cancer therapy and chorioretinal neovascularization, the initial, striking, short-term response and patients' high tolerance of local bevacizumab therapy offer encouraging results for the potential role of anti-VEGF agents in treating anterior segment neovascular disorders. Controlled prospective trials are needed to establish the long-term safety, efficacy, and dosing guidelines for the use of anti-VEGF agents in anterior segment neovascularization.

Hemangiogenesis and lymphangiogenesis in corneal pathology

PURPOSE

We characterized the presence of hemangiogenesis (HA) and lymphangiogenesis (LA) in human corneal specimens exhibiting 13 underlying pathologies.

METHODS

Human corneal specimens were obtained from consenting subjects (n = 2 or n = 3 for each pathology; total sample size, n = 35). The pathological specimens were stained with hematoxylin and eosin (H&E) to determine the presence or absence of corneal neovascularization (NV) and superficial or deep stromal distribution of NV. Immunohistochemical staining was then performed to differentiate HA (positive for CD31) from LA (positive for lymphatic vessel endothelial hyaluronan receptor-1 [LYVE-1]).

RESULTS

The double-negative (CD31(-)/LYVE-1(-)) immunostaining, indicating the absence of NV, was exhibited by 21 specimens (60%). CD31(-)/LYVE-1(-), indicating the presence of HA and absence of LA, was exhibited by 12 specimens (34%). The double-positive (CD31(+)/LYVE-1(+)) phenotype, indicating both HA and LA, was exhibited by 2 specimens (6%). Notably, the CD31(-)/LYVE-1(-) phenotype, indicating the presence of LA and absence of HA, was not detected among the specimens. Deep stromal NV was exhibited in a 4:3 ratio to superficial stromal NV. The double-negative immunostaining was more prevalent in noninflammatory pathologies, particularly in comparison with combined neovascular phenotypes (ie, CD31(+) or LYVE-1(+)). Among the neovascular phenotypes, HA was 7 times more common than LA. Specimens exhibiting LA presented only with the double-positive phenotype.

CONCLUSIONS

HA is the predominant component of NV in corneal pathologies. LA accompanies HA; however, isolated LA (from lymphatics in the conjunctiva) does not occur in these corneal pathologies. Our results suggest the potential therapeutic utility of targeting antineovascular therapies specifically for corneal HA and/or LA pathology.

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.

Ultrastructural pathology of corneal neovascularization after photodynamic therapy in rabbits

AIM

To investigate the ultrastructural pathogenesis of photodynamic therapy (PDT) for the experimental corneal neovascularization (CNV) by Hematoporphyrin Derivate (HPD) as photosensitizer and Argon laser as light source.

METHODS

Experimental CNV models were induced in 7 white rabbits using alkali burn. Six weeks after models establishment, animals with CNV were injected with HPD intravenously, and 48 hours after the injection, 7 eyes were irradiated with argon laser (power 800mw, wavelength 514.5nm, spot diameter 200µm, exposure time 2ms). The irradiated CNV was observed by light microscopy and scanning electron microscopy.

RESULTS

Histopathological study indicated that there was a striking decrease in the number of the CNV, vascular endothelium became degeneration and necrosis, some vessels were atrophy and attenuated, and vessels cavity were blocked by some thrombosis. No obvious abnormal histopathological findings were noted in surrounding tissues.

CONCLUSION

The high precise action on CNV and minimal damage to surrounding tissues with PDT by HPD as photosensitizer suggested that PDT might be an effective and safe modality in the treatment of CNV.

Novel aspects of corneal angiogenic and lymphangiogenic privilege

In this article, we provide the results of experimental studies demonstrating that corneal avascularity is an active process involving the production of anti-angiogenic factors, which counterbalance the pro-angiogenic/lymphangiogenic factors that are upregulated during wound healing. We also summarize pertinent published reports regarding corneal neovascularization (NV), corneal lymphangiogenesis and corneal angiogenic/lymphangiogenic privilege. We outline the clinical causes of corneal NV, and discuss the angiogenic proteins (VEGF and bFGF) and angiogenesis regulatory proteins. We also describe the role of matrix metalloproteinases MMP-2, -7, and MT1-MMP, anti-angiogenic factors, and lymphangiogenic regulatory proteins during corneal wound healing. Established and potential new therapies for the treatment of corneal neovascularization are also discussed.

Inhibition of corneal neovascularization with plasmid pigment epithelium-derived factor (p-PEDF) delivered by synthetic amphiphile INTeraction-18 (SAINT-18) vector in an experimental model of rat corneal angiogenesis

The use of Synthetic Amphiphile INTeraction-18 (SAINT-18) carrying plasmid pigment epithelium-derived factor (p-PEDF) as an anti-angiogenesis strategy to treat corneal neovascularization in a rat model was evaluated. Four partially dried forms (Group A: 0 microg, B: 0.1 microg, C: 1 microg, D: 10 microg) of a p-PEDF-SAINT-18 were prepared and implanted into the rat subconjunctival substantia propria 1.5 mm from the limbus at the temporal side. The 1 microg of plasmid-basic fibroblast growth factor--SAINT-18 (p-bFGF-SAINT-18) (1 microg) was prepared and implanted into the rat corneal stroma 1.5 mm from the limbus on the same side. Inhibition of neovascularization was observed and quantified from day 1 to day 60. PEDF (50-kDa) and bFGF (18-kDa) protein expression were analyzed by biomicroscopic examination, Western blot analysis, and immunohistochemistry. Gene expression in corneal and conjunctival tissue was observed as early as 3 days after gene transfer and stably lasted for over 3 months with minimal immune reaction. Subconjunctival injection of a highly efficient p-PEDF-SAINT-18 successfully inhibited corneal neovascularization. Successful gene expression of bFGF, PEDF and a mild immune response of HLA-DR were shown by immunohistochemistry staining. We concluded that SAINT-18 was capable of directly delivering genes to the ocular surface by way of subconjunctival injection, and delivered sustained, high levels of gene expression in vivo to inhibit angiogenesis.

Corneal transparency: genesis, maintenance and dysfunction

Optimal vision is contingent upon transparency of the cornea. Corneal neovascularization, trauma and, surgical procedures such as photorefractive keratectomy and graft rejection after penetrating keratoplasty can lead to corneal opacification. In this article we identify the underlying basis of corneal transparency and factors that compromise the integrity of the cornea. With evidence from work on animal models and clinical studies, we explore the molecular mechanisms of both corneal avascularity and its dysfunction. We also seek to review therapeutic regimens that can safely salvage and restore corneal transparency.

Bevacizumab (avastin) and argon laser to treat neovascularization in corneal transplant surgery

PURPOSE

Two eyes with corneal neovascularization were treated with argon laser and bevacizumab (Avastin) to enhance transplant survival after penetrating keratoplasty.

PATIENTS AND METHODS

Before penetrating keratoplasty, pathologic corneal vessels were treated with argon laser coagulation and a simultaneous, subconjunctival bevacizumab injection. Four to 6 weeks after this treatment, corneal transplantation was performed, followed by an intraocular injection of bevacizumab.

RESULTS

A marked reduction of corneal neovascularization was observed in both eyes after the combined argon laser coagulation and subconjunctival bevacizumab injection. No major bleeding from corneal vessels occurred during the recipients' cornea trephination. At the end of the transplantation, bevacizumab was injected into the anterior chamber, the posterior chamber, and subconjunctivally without any immediate side effects. No recurrence of pathologic vessels' spreading into the graft was observed. Both transplants have remained clear without signs of rejection for more than 6 months.

CONCLUSIONS

The combination of argon laser coagulation and bevacizumab injections may be a promising tool in treatment of neovascularization in association with corneal transplant surgery. Antivascular endothelial growth factor substances may increasingly play a role in anterior segment surgery in the future.

Inhibition of corneal neovascularization with endostatin delivered by adeno-associated viral (AAV) vector in a mouse corneal injury model

The use of a recombinant adeno-associated viral (rAAV) vector carrying endostatin gene as an anti-angiogenesis strategy to treat corneal neovascularization in a mouse model was evaluated. Subconjunctival injection of recombinant endostatin-AAV was used to examine the inhibition of corneal neovascularization induced by silver nitrate cauterization in mice. The results showed that gene expression in corneal tissue was observed as early as 4 days after gene transfer and stably lasted for over 8 months with minimal immune reaction. Subconjunctival injection of a high-titer rAAV-endostatin successfully inhibited neovascularization. Immunohistchemistry staining of CD 31 and endostatin showed that the treatment significantly inhibits angiogenesis in cornea. We concluded that the rAAV was capable of directly delivering genes to the ocular surface epithelium by way of subconjunctival injection and was able to deliver sustained, high levels of gene expression in vivo to inhibit angiogenesis.

Bilateral severe progressive idiopathic lipid keratopathy

PURPOSE

To report a case with bilateral progressive lipid keratopathy.

METHODS

A 44-year-old healthy man without previous ocular disease presented with bilateral lipid keratopathy which was more severe in his right eye. Evidence of hyperlipidemia or clinical corneal neovascularization was not apparent.

RESULTS

Penetrating keratoplasty (PKP) was performed, initially in the right eye and four years later in the left eye. Histochemical examination showed focal stromal vascularization and staining for lipids. During the follow-up period, one episode of graft rejection occurred in each eye; both responded to systemic steroid therapy.

CONCLUSION

Severe bilateral progressive lipid degeneration can develop in previously healthy corneas in healthy patients without underlying pathology. The nature of the process remains unclear. When PKP is performed and neovascularization is identified in the removed corneal button, close follow-up is advisable because corneal grafts can be prone to rejection.

“Steel Wool Keratopathy”

PURPOSE

To introduce into the clinical nomenclature a sign frequently observed in our patients with persistent corneal inflammation associated with herpetic stromal keratitis.

METHODS

Case reports and review of the literature.

RESULTS

Four representative patients with herpesvirus stromal keratitis are presented. Herpes simplex virus-1 (HSV-1) was confirmed by culture in 1 case and by polymerase chain reaction in a second case. In the remaining 2 cases, the diagnosis was made based on characteristic clinical findings for herpes simplex virus and varicella zoster virus (VZV). On clinical examination, all 4 representative cases of stromal keratitis revealed a well-defined, localized region of intertwined, metallic-like, polychromatic material in the corneal stroma, a sign we have termed steel wool keratopathy. We have only rarely observed this finding in patients with stromal keratitis not caused by a herpesvirus.

CONCLUSION

Steel wool keratopathy seems to represent a focal region of stromal degeneration or deposition associated with chronic inflammation. Although we most often observe this finding in patients with stromal keratitis secondary to HSV or VZV, we cannot exclude the possibility that this sign represents the sequelae of chronic/recurrent inflammation rather than a specific pathologic response to herpetic antigens.

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

PURPOSE

Long-term evaluation of dihematoporphyrin ether (DHE) safety and efficacy as photodynamic therapy (PDT) for patients with corneal neovascularization (KNV).

DESIGN

Prospective multi-center interventional case series.

METHODS

Seven patients were enrolled after Institutional Review Board approval and a detailed informed consent were obtained. Eligible patients presented with clinically stable KNV without active vessel progression or inflammation. All patients with severe hypertension, history of renal or hepatic disease, or sensitivity to porphyrins, and those with active keratitis or uncontrolled ocular surface disease were excluded. DHE was administered as an intravenous bolus (2 mg/kg). Seventy-two hours later, PDT was carried out using argon green laser (514 nm). The main outcome measure, extent of vascular thrombosis, was estimated during postoperative follow-up examinations performed at day 1, 1 week, 6 months, and up to 12 years postoperative.

RESULTS

All patients obtained an immediate reduction in measurable corneal vascularization. With at least 6 months of follow-up, six of seven patients maintained a significant reduction (52.5% +/- 19.6%, P < .01) in KNV. The mean length of followup was 5.4 years (Range = 6 months to 12 years) during which time there were no other ocular changes attributable to laser treatment. Three patients suffered significant systemic short-term phototoxicity reactions.

CONCLUSIONS

Intravenous DHE followed by photodynamic treatment in humans is effective for the reduction of inactive, established KNV. However, the significant short-term adverse effects related to systemic administration of this drug are of particular concern and warrant further investigation.

Fluorescein angiographic monitoring of corneal vascularization in lipid keratopathy

The use of digital fluorescein corneal angiography to assist argon laser photocoagulation is reported. Photocoagulation was performed on the vascular supply of lipid keratopathy in the left eye of a 44-year-old woman.