Introduction
A potentially blinding disorder known as corneal neovascularization involves the introduction of vascular pathology into the typically avascular cornea. Other ocular pathologies that might contribute to this include traumatic circumstances, post-corneal transplantation, immunological hypersensitivity, autoimmune diseases, chemical harm, and post-infection inflammation.
What Is the Etiology Associated With Corneal Neovascularization?
A pathologic disease of the cornea called corneal neovascularization (NV) is marked by the development and expansion of new vascular capillaries inside and into the formerly avascular corneal regions, extending from the limbus into the superficial or deep parts of the cornea. An imbalance between the angiogenic and antiangiogenic elements that maintain corneal transparency is the root cause of it. Immature new blood vessels can cause prolonged inflammation, scarring, and lipid exudation, endangering the cornea's transparency and visual acuity. A corneal graft recipient's ability to see may be irreversibly compromised in advanced stages when ingrown blood vessels have already reached the visual axis. These conditions also increase the risk of rejection.
What Is the Pathophysiology Associated With Corneal Neovascularization?
Numerous corneal pathologies, such as congenital illnesses, contact lens-related hypoxia, inflammatory conditions, chemical burns, limbal stem cell shortage, allergies, trauma, infectious keratitis, autoimmune diseases, and corneal transplant rejection, all-cause corneal neovascularization. These illnesses cause an imbalance between proangiogenic and antiangiogenic factors, which might cause vascular endothelial cells to proliferate and migrate into the corneal stroma.
The increase of angiogenic cytokines mediates the in-growth of new blood vessels. While proteolytic enzymes enable vascular epithelial cells to reach the stromal layer of the cornea, metalloproteinase, the cornea's extracellular matrix, and the basement membrane are destroyed.
When there is ocular inflammation, macrophages, certain inflammatory cells, and corneal epithelial and endothelial cells release angiogenic growth factors such as VEGF and fibroblast growth factors. VEGF promotes the development of new blood vessels by stimulating endothelial cell synthesis of matrix metalloproteinases in the limbal vascular plexus.
What Are Signs and Symptoms of Corneal Neovascularization?
In the case of corneal vascularization, a patient may not exhibit any symptoms, although sometimes they may have the following:
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Eye discomfort.
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Redness.
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Teary eyes.
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Photophobia (the fear of light).
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An inability to use contacts for more than a few hours.
How Can Corneal Neovascularization Be Diagnosed?
A provider can use several methods to find ocular neovascularization.
They might consist of the following:
1. An eye exam with a dilated slit light.
2. Optical coherent tomography.
3. Angiography using indocyanine green or fluorescein.
What Are the Treatment Modalities That Are Used to Treat Neovascularization?
There are several medicinal methods for treating corneal neovascularization, all of which are employed off-label. Before considering more invasive surgical interventions, we advise thoroughly investigating these choices. It is crucial to stop wearing contact lenses while neovascularization is treated if contact lens-related hypoxia is detected. After corneal NV resolution, lenses with greater gas permeability may be recommended.
1. Steroids - The primary therapy method for corneal neovascularization should be topical steroids and nonsteroidal anti-inflammatory medications (NSAIDs). Before leukocyte infiltration and recruitment, these medications should be provided within 24 hours of the first corneal injury. However, the outcomes might vary greatly. Infection, glaucoma, cataracts, and recurrence of herpes simplex are all risks that steroids increase, while excessive NSAID usage raises the risk of corneal ulceration and melting.
2. Anti-VEGF Agents - Monoclonal anti-VEGF antibodies have demonstrated promising effects in treating corneal neovascularization. Bevacizumab or Ranibizumab have shown strong short-term safety and effectiveness when applied topically or subconjunctivally, but no long-term studies are available.
3. Inhibitors of MMP
Suppression of the enzymes that affect the cornea's structural integrity may prevent neovascularization from developing in inflammatory situations. A nonselective MMP inhibitor, Doxycycline, has been proven to decrease neovascularization when combined with topical corticosteroids.
There are many laser and surgical options to treat corneal neovascularization. Due to their invasive nature, these treatments should only be used on individuals in whom medicinal therapy has failed to yield the desired outcomes.
1. Laser Ablation - By coagulating blood arteries and ablating tissue, argon, and Nd: YAG lasers can occlude invasive blood vessels. Because consequences, including corneal hemorrhage and corneal thinning, might arise, extreme care must be used to prevent excessive radiation and harm to surrounding tissues. Because of the depth, size, and high blood flow rates of afferent arteries, occlusion attempts are frequently futile.
2. Diathermy and Cautery - A little needle may puncture the feeder veins near the limbus. Both thermal cautery using an electrolysis needle and the administration of a coagulating current using a unipolar diathermy device can occlude vessels. Although preliminary investigations indicated that these methods were secure and efficient.
3. Photodynamic Therapy - Reactive oxygen species are produced in the artery lumen due to the irradiation of a previously injected photosensitive dye, which leads to the endothelium and basement membrane going through apoptosis and necrosis. The vessel is sealed up due to the extremely specific tissue injury and the subsequent thrombogenic reaction. Despite its effectiveness, photodynamic treatment is not widely used in clinical settings because of the high costs and possible risks associated with laser irradiation and the production of reactive oxygen species.
Conclusion
A potentially blinding disorder known as corneal neovascularization involves the introduction of vascular pathology into the typically avascular cornea. Other ocular pathologies that might contribute to this include traumatic circumstances, post-corneal transplantation, immunological hypersensitivity, autoimmune diseases, chemical harm, and post-infection inflammation. Redness, watery eyes, photophobia, and an inability to use contact lenses for more than a few hours are all symptoms of corneal neovascularization. Steroids are among the topical therapies for corneal neovascularization, and anti-VEGF medications are presently the standard first therapy. Surgical treatments, including laser surgery, are available for corneal neovascularization therapy.
