When to see a vet urgently
Contact a vet immediately if your cat has any of the following:
- an eye that stays closed, or squinting and rubbing;
- rapidly developing cloudiness, or a visible depression, bulge or dark area on the surface;
- an eye struck by a claw, sharp object or chemical;
- a sudden change in eye appearance or apparent sight loss.
Overview
The cornea is the transparent layer of the eye that admits light and helps focus an image. Damage to its surface cells or connective tissue layer breaks its integrity, causing inflammation, pain and a risk of secondary infection. Ulcers may be superficial, limited to the epithelium, or deep, extending into connective tissue layers and potentially progressing to perforation.
The surface epithelium provides protection, while the stroma beneath gives the cornea strength. Even a small surface injury can allow microbes into deeper layers. Depth is crucial to treatment and cannot be inferred from the amount of discharge alone.
If the supporting layer thins away almost completely and only the deepest protective membrane remains, a descemetocele forms. This lesion is at risk of perforation. A closed eye or a small visible wound does not make the situation safe; the structure needs examination.
Causes
- viral infections, with feline herpesvirus FHV-1 among the most important causes;
- injuries, such as claw scratches and foreign bodies;
- bacterial and fungal eye infections;
- dry eye, or keratoconjunctivitis sicca;
- eyelid abnormalities, including inward-turning lids, known as entropion, and distichiasis;
- chronic conjunctival and corneal inflammation;
- chemical burns.
After infection, herpesvirus can remain dormant in nerve cells and reactivate later. An adult cat's eye symptoms may therefore relate to an old infection rather than a recent encounter with a sick cat. However, recurrence is not an inevitable consequence of every ulcer.
An eyelid or hair rubbing against the cornea can maintain damage despite medication. The mechanical cause then also needs correction. Bacteria can complicate an existing ulcer; finding them does not necessarily mean they caused the initial injury.
Risk factors
- kittens and young cats with herpesvirus infection;
- cats with chronic eye diseases;
- cats in crowded conditions, such as breeding establishments and rescue centres;
- short-nosed breeds, such as Persians and British Shorthairs, which are more prone to corneal injury.
Breed predisposition relates to particular eye structures and corneal diseases, but the listed breeds cannot be placed in the same risk category without more detail. Evidence on the size of the risk in an individual breed is particularly limited. Non-pedigree cats also develop ulcers, and examination assesses the individual's eyelid position and eye surface.
Typical symptoms
- watering and eye discharge;
- eyelid spasm, with squinting or holding the eye closed;
- light sensitivity;
- conjunctival redness and swelling;
- corneal cloudiness or roughness;
- an ulcer visible on examination;
- sight loss with deep ulcers or perforation.
Your cat may rub the eye with a paw or against furniture, and the third eyelid may become more visible. Rubbing can worsen tissue damage. An ulcer may be too small for you to see even when the eye is clearly painful.
Cloudiness can result from fluid in the tissue, inflammation or later scarring. A white or bluish colour alone does not reveal depth. Redness also cannot distinguish a superficial ulcer from a deeper eye disease.
Complications and consequences
- secondary bacterial infections;
- deep ulcers at risk of corneal perforation;
- prolapse of the iris;
- scarring and impaired vision;
- loss of the eye in severe disease.
In a complicated ulcer, the corneal supporting tissue can break down and soften rapidly, known as corneal melting. This may need urgent intensive medical treatment and surgical support.
Cats can also develop a corneal sequestrum, a brown or black area of dead tissue. It is often associated with a chronic, poorly healing ulcer, but does not follow every ulcer. Do not remove a dark area at home: depth and the need for surgery are assessed during an eye examination.
Diagnosis at the vet
- an eye examination;
- fluorescein staining to identify corneal damage;
- bacterial culture for complicated ulcers;
- detailed examination of the eye to assess depth;
- eye pressure measurement to rule out concurrent glaucoma.
The examination establishes symptom onset, any fight or chemical exposure and previous eye problems. The vet also checks eyelid edges, hair direction, the eye surface and, where necessary, tear production. Successful treatment requires finding any source of ongoing irritation.
Fluorescein is a dye that adheres to tissue exposed by surface damage. Staining helps identify an ulcer and monitor closure. Depth is also assessed with magnification and focused light, such as a slit lamp. The detailed examination listed above means close examination of the eye, rather than usually inserting an endoscope inside it.
Pressure measurement does not automatically suit every ulcerated eye. A deep, infected or near-perforating cornea can be damaged even by light contact. The vet first assesses tissue strength and selects safe tests. Do not force the eyelids open or press on the eye at home.
A deep or infected ulcer may need cytology and bacterial culture to target antimicrobial treatment. PCR can detect herpesvirus genetic material. A positive result alone does not prove the virus caused this ulcer because symptom-free shedding also occurs.
Treatment
Treatment depends on ulcer depth, infection and the underlying cause. A superficial injury may be treated with a topical antimicrobial, a lubricating preparation and pain relief suitable for cats. Herpesvirus-associated disease may need an antiviral. An antibiotic does not itself treat a virus or correct an inward-turning eyelid.
A deep, melting or perforated ulcer may need surgery by a vet experienced in eye disease. Damaged tissue can be removed and the surface supported with a tissue graft. The procedure depends on the strength of the remaining cornea and the injury's location. Not every superficial ulcer needs surgery.
Do not start a corticosteroid eye medicine on an open ulcer yourself: it can slow healing and worsen damage. Anaesthetic drops used during examination are not for home pain relief either, as repeated use can damage the cornea. Always have an old eye medicine's suitability checked again.
Home care
A protective collar prevents pawing and rubbing. Use it as instructed even if your cat already seems calmer. If it prevents eating or drinking, ask the practice for help finding a suitable model and arrangements. Do not stop eye protection yourself.
Wash your hands before and after giving eye medicine. The bottle tip must not touch the eye surface, eyelids or other surfaces. Ask the practice to demonstrate administration if it feels difficult. Handle a painful eye gently; another person can help keep your cat calm.
Give only prescribed preparations according to written instructions. If a medicine clearly increases pain or redness, contact the vet before the next administration. Explain if treatment is not practical too. Arrangements may need changing so the eye receives essential medication.
Monitoring and prognosis
Follow-up assesses depth and healing, and fluorescein staining may be repeated. Less squinting alone does not show that the protective surface has closed. Do not skip an agreed check or medication simply because the eye looks better.
A superficial ulcer treated promptly often heals well. Deep damage, infection, melting tissue or continuing eyelid irritation make recovery longer and more difficult. Scarring or extensive blood vessel growth can reduce corneal clarity even after recovery. Suddenly increasing pain, cloudiness or altered eye shape needs another urgent assessment.
Prevention
- Have FHV-1 infection treated promptly.
- Prevent eye injuries by supervising play and protecting against foreign objects.
- Arrange regular eye checks for cats with chronic conjunctivitis.
- Monitor eyelid defects and have them surgically corrected in good time.
Herpesvirus treatment does not usually eliminate dormant virus from the body. Vaccination reduces disease severity but does not prevent every infection or carrier state. A calm routine and infection management in multi-cat homes support prevention, but new eye pain still needs investigation rather than assuming it is the same viral problem again.
Keep irritating cleaning agents and dusty renovation materials away from cats. An eyelid structural defect is assessed individually: a lid repeatedly rubbing the cornea may need correction, but surgery is not performed solely because of a breed name. A recurrent ulcer warrants a search for ongoing irritation or another underlying disease.
Important for cat owners
A corneal ulcer is painful and can threaten sight. Remember that squinting, discharge or a cloudy eye is urgent. The earlier treatment starts, the better the chance of preserving sight and preventing loss of the eye.
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
Can there be an ulcer without a visible scratch?
Yes. A small surface defect may only show with staining. Painful squinting, discharge or cloudiness warrants examination even if you cannot see a wound.
Can I use eye drops left over from last time?
Do not start them without veterinary assessment. Treatments for different eye diseases vary, and a corticosteroid preparation, for example, can worsen an open corneal ulcer.
Has the ulcer healed once my cat keeps the eye open?
Not necessarily. Pain can decrease before the surface closes. Healing is confirmed at the agreed follow-up, and medicines and collar use stop only as instructed.
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
- Disorders of the Cornea in Cats, Merck Veterinary Manual, accessed 2026-11-03.
- Corneal Ulcers in Cats, VCA Animal Hospitals, accessed 2026-11-03.
- Guideline for Feline Herpesvirus Infection, European Advisory Board on Cat Diseases, accessed 2026-11-03.
- Corneal Ulcers, Cornell Feline Health Centre, accessed 2026-11-03.
- Applying Eye Drops to Cats, VCA Animal Hospitals, accessed 2026-11-03.
- Eye ulcers (corneal ulcers) in cats, PDSA, accessed 2026-11-03.
- Deep Stromal Corneal Ulcers, Descemetocele, and Iris Prolapse in Small Animals, Merck Veterinary Manual, accessed 2026-11-03.
- Corneal Sequestrum, American College of Veterinary Ophthalmologists, accessed 2026-11-03.
- Frequently Asked Questions: tonometry safety, Icare Finland, accessed 2026-11-03.