When to see a vet urgently
Seek prompt treatment if your cat develops:
- marked squinting or keeping an eye closed;
- rapidly increasing cloudiness or visible surface damage;
- obvious eye pain and rubbing;
- sudden visual deterioration or symptoms after an eye injury.
Do not wait for vessels to grow if the eye is already painful. You can find a vet near you.
Overview
The cornea is the transparent layer that refracts light at the front of the eye. Its absence of blood vessels makes it completely clear. However, with chronic irritation or damage, the body promotes vessel growth into it to deliver oxygen and nutrients. This is called neovascularisation.
Although vessels temporarily help inflamed or damaged tissue heal, they reduce corneal transparency and vision. Neovascularisation is therefore always considered a sign of disease.
However, vessels may also accompany ongoing wound healing and do not alone indicate continuing infection. They can remain visible after an ulcer has closed. A new finding needs examination, but treatment also depends on whether damage, inflammation or another irritant remains.
A healthy cornea receives nourishment from tears on its outer surface and fluid in the eye's anterior chamber on its inner surface. It therefore normally needs no blood vessels of its own. Swelling, inflammatory cells, pigment and scar tissue also affect transparency. Cloudiness cannot therefore be assessed simply by counting red lines.
Causes
- Chronic corneal inflammation, or keratitis.
- Corneal ulcers caused by injury, infection or a virus.
- Viral infections, with feline herpesvirus one of the most important causes.
- Mechanical injuries, including scratches and foreign bodies.
- Dry eye, or keratoconjunctivitis sicca, with inadequate tear production.
- Eye surface tumours.
- Chemical burns or irritation.
The same visible vessel growth can accompany different diseases. A superficial ulcer, deeper inflammation and chronic eyelid friction, for example, need different treatment. If a rubbing eyelid edge or foreign body remains, medication alone may not resolve the problem. Neovascularisation itself does not identify which listed cause is responsible.
In cats, vessels may also surround a corneal sequestrum, a piece of dead tissue appearing as a brown or black area. Eosinophilic keratoconjunctivitis is another disease involving accumulation of particular inflammatory cells on the eye's surface. Pale or pink raised areas and blood vessels may appear. Distinguishing these from an ordinary ulcer affects medication and possible surgery choices.
Risk factors
- Chronic viral infections, particularly feline herpesvirus.
- Eye injuries in outdoor or fighting cats.
- Congenital or acquired eyelid defects, such as inward-turning eyelids.
- Delayed treatment of eye disease.
Risk factors relate primarily to the disease causing vessel growth. Not every herpesvirus carrier or outdoor cat develops the same eye lesion. An indoor cat can also injure an eye or have an eyelid rub the cornea. Previous eye disease and treatment records are therefore more useful than assuming a particular living environment rules out the problem.
Typical symptoms
- Visible red blood vessels growing into the cornea.
- Corneal cloudiness and reduced transparency.
- Tearing.
- Light sensitivity, making looking towards light painful.
- Squinting, or blepharospasm, and discharge with ulcers.
- Impaired vision, potentially progressing to loss of sight, with severe or chronic neovascularisation.
Vessels visible in the white of the eye or conjunctiva are different from vessels over the transparent cornea. However, distinguishing eye layers is difficult for an owner, especially when the surface is cloudy. A photograph can help monitor changes but does not reliably show ulcer depth or inflammation inside the eye.
Pain may appear as avoiding light, closing the eye or rubbing the face. Not every cat shows equally obvious signs. Watch whether one or both eyes are affected and whether cloudiness or a dark area has enlarged. Explain previous injuries, drops used and whether the eye has ever been completely symptom-free between episodes.
Complications and consequences
- Permanent visual impairment from corneal cloudiness.
- Chronic pain from ulcers and inflammation.
- Corneal scarring.
- Blindness in severe chronic cases.
Visual effects depend on the lesion's location, extent and depth. A small peripheral lesion may not affect sight like a dense central scar. A severe ulcer can thin the cornea and eventually perforate it, threatening the entire eye. Vessel growth therefore does not prove that an ulcer will safely heal by itself.
Diagnosis at the vet
- Slit-lamp eye examination.
- Fluorescein staining to identify corneal ulcers.
- Eye pressure measurement to investigate glaucoma.
- Cytology or bacterial culture if infection is suspected.
- A Schirmer tear test to assess tear production.
A slit lamp is a magnifying instrument used to examine corneal layers and locate damage. The vet also assesses whether vessels accompany swelling, inflammatory cells, pigment or thinning. Eyelid position and ability to close the eye are checked so continuous mechanical damage is not left untreated.
Fluorescein adheres to damaged corneal surfaces and helps identify ulcers. Repeat staining can monitor closure. Tear testing and eye pressure measurement complement the assessment according to findings; pressure measurement alone does not explain vessel growth. Deep injuries require particular care during examination and handling.
Cytology helps establish the type of inflammation. Bacterial culture and susceptibility testing can guide treatment, especially for a deep or suspected infected ulcer. Herpesvirus PCR may support investigation, but a positive result alone does not establish that the virus causes that cat's symptoms. Samples follow clinical suspicion; not every vascularised eye needs every test.
Treatment
Treatment aims to remove the cause of neovascularisation:
- antivirals for herpesvirus infection;
- antibiotics or antifungals for infected ulcers;
- anti-inflammatory medicines, including corticosteroids or NSAIDs, only as prescribed by a vet;
- corneal protective products and artificial tears;
- surgery for deep ulcers, using corneal or conjunctival grafts.
Do not use corticosteroid-containing drops yourself on an open corneal ulcer: they can prevent healing and cause serious complications. Before such treatment, the vet checks the eye's surface. Antibiotics and antifungals are also selected according to confirmed or suspected infection, rather than visible vessels alone.
Vessels supporting healing are not always the first target for reduction. Once an ulcer closes, the need to reduce remaining inflammation or vessels can be assessed separately. In herpesvirus-related disease, the active eye problem is treated even though the virus may remain in the body. Pain is managed with medication appropriate for the eye injury.
For a deep ulcer, surgery aims to reinforce the thinned cornea and prevent perforation. A conjunctival graft may deliberately bring blood supply and support to the lesion. This is compatible with treatment: saving the eye's structure can matter more than perfect clarity immediately after surgery. Graft type depends on the lesion and remaining healthy tissue.
Early treatment improves the chance of restoring corneal clarity and preserving vision.
Home care and check-ups
Give only eye medicines prescribed for this cat and follow their instructions. Do not use leftover corticosteroid drops for new redness. Wash hands before and after handling, and keep the bottle tip away from the eye and eyelids. This reduces contamination and further injury from touching the eye.
If your cat rubs the eye, use protection recommended by the practice. Report difficulties administering drops so treatment is not left undone. If pain, redness or rubbing clearly increase after drops, contact the practice before continuing. Forcible handling, pressing on the eye or trying to remove a dark area are not home care.
Record changes and explain at agreed check-ups how successfully medication has been given. Symptom relief alone does not confirm ulcer closure. Remaining vessel growth may also require monitoring without medication continuing unchanged. Stopping or reducing treatment is agreed according to findings.
Prognosis
Prognosis depends on the underlying disease and whether permanent scarring or significant thinning has developed. Treatment may preserve a comfortable, functional eye even if full clarity does not return. A conjunctival graft may remain opaque. Recurrent herpesvirus-related damage or uncorrected eyelid friction may need a long-term plan to prevent further ulcers.
Prevention
- Treat eye inflammation promptly.
- Protect your cat's eyes from injury, particularly with outdoor access.
- Vaccinate against feline herpesvirus.
- Arrange regular eye examinations for chronic eye disease.
Herpesvirus vaccination reduces disease severity but does not prevent every infection or later relapse. Correcting a structural eyelid problem and appropriately treating eye surface disease may matter more than cleaning alone. Agreed eye check-ups help assess healing even when discharge visible at home has already decreased.
Important for cat owners
Corneal neovascularisation is not an independent disease but a sign of chronic eye inflammation or injury. Remember that vessels appearing in the cornea are a warning requiring veterinary examination, preferably by a vet experienced in eye disease. Timely treatment helps preserve vision and prevent serious complications.
This article provides general information and does not replace veterinary care. If you notice signs of illness in your cat, contact a vet.
Frequently asked questions
Are all red vessels in the eye neovascularisation?
No. The conjunctiva and white of the eye normally contain blood vessels. In neovascularisation, vessels grow into the normally vessel-free cornea. Distinguishing structures and possible injury requires an eye examination.
Why are vessels still visible after an ulcer heals?
Vessels involved in healing may remain after closure. A check-up assesses whether active injury or inflammation remains and whether the change affects vision. A persistent red line alone does not determine medication needs.
Can corticosteroid drops remove the vessels?
In some situations, they can be used under veterinary supervision after checking the eye's surface. They can be dangerous in an open ulcer. Treatment primarily targets the disease causing vessel growth, rather than appearance alone.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
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- The Cornea in Animals, Merck Veterinary Manual, accessed 2026-11-05.
- Corneal Surgery - When Eye Drops Don’t Cut It, American College of Veterinary Ophthalmologists, accessed 2026-11-05.
- Corneal Sequestrum, American College of Veterinary Ophthalmologists, accessed 2026-11-05.
- Eosinophilic Keratoconjunctivitis in Cats, Veterinary Clinics of North America: Small Animal Practice / PubMed, accessed 2026-11-05.
- GUIDELINE for Feline Herpesvirus infection, European Advisory Board on Cat Diseases, accessed 2026-11-05.
- Applying Eye Drops to Cats, VCA Animal Hospitals, accessed 2026-11-05.
- Corneal Ulcers, Cornell Feline Health Centre, accessed 2026-11-05.