DOGS AND CATS · OWNER EDUCATION
Glaucoma in Dogs and Cats
Glaucoma is pressure buildup inside the eye that damages the nerve carrying visual information to the brain. Sudden glaucoma is painful and can cause irreversible blindness quickly.
THE SHORT VERSION
What matters for your animal?
Start with the warning signs and when-to-contact sections if your animal is unwell. The same outward change can have several causes, so this guide helps you prepare questions rather than identify a diagnosis on your own.
What is this condition?
Glaucoma is pressure buildup inside the eye that damages the nerve carrying visual information to the brain. Sudden glaucoma is painful and can cause irreversible blindness quickly.
The central concern in glaucoma is pressure damaging the structures needed for sight. Waiting for an eye to become visibly enlarged can mean losing valuable treatment time. A veterinarian assesses pressure and remaining vision to decide what can be protected. If sight cannot be restored, relieving continuing pain still matters; blindness does not make a painful eye a resolved problem.
Which species does this guide cover?
The species listed above are the focus of this guide, rather than a complete list of every animal that can develop this condition. Causes, testing and treatment may differ between species and individual patients.
Glaucoma affects dogs and cats. In cats it is less common and often develops secondary to inflammation or another eye disorder. Some dogs have inherited drainage abnormalities. Testing the pressure and underlying cause matters more than copying another animal's eye-drop plan.
Why can it happen?
- Drainage abnormalities can be inherited. Inflammation, lens movement or other eye disease can also block fluid drainage.
What might an owner notice?
- A red or cloudy eye, squinting, a larger-looking eye, a widened pupil, or bumping into objects. Some animals become quiet or stop eating.
An eye can be painful even when there is little discharge. Holding it partly closed, avoiding light, rubbing the face, or becoming reluctant to move through familiar surroundings can be important clues. Surface injury, inflammation inside the eye, and abnormal pressure can look similar from outside. Looking at a photograph cannot replace examination of the structures and measurements that distinguish them. A sudden change in sight or a painful eye deserves prompt attention because some eye problems progress quickly.
How is the problem investigated?
A veterinarian measures eye pressure and examines vision and internal structures. Both eyes are checked, because the other eye may also be at risk.
Eye pressure is measured with an instrument rather than estimated from redness or appearance. Pressure, vision, pupil responses, and the internal eye examination are considered together. Both eyes may need assessment even if only one seems abnormal. Treatment has two related goals: protect any remaining sight and relieve pain. A permanently blind eye can still need treatment for comfort, so the plan is not based only on whether vision can be restored.
What might treatment involve?
Emergency pressure-lowering treatment may preserve remaining vision. Specialist procedures can help selected cases; a blind painful eye still needs a comfort plan.
This is an overview, not a prescription or a recommendation for a specific individual animal.
What can owners do at home?
Use drops exactly as prescribed and keep pressure-check appointments. Ask which changes warrant immediate reassessment.
Comfort is assessed through behavior and function as well as obvious crying or vocalization. Changes in posture, movement, grooming, sleep, social interaction, or willingness to be handled can be useful clues. Compare the animal with its own normal behavior rather than with another animal. Keep a short record of what it can do comfortably and share changes with the care team. If pain control appears inadequate, contact the veterinarian; increasing a dose or combining medicines without advice can introduce serious risks.
Avoid actions that could make care less safe.
- Do not wait for an eye to enlarge or use human redness-relief drops. A seemingly comfortable animal can still have damaging pressure.
What can the longer-term outlook involve?
Vision depends strongly on how long and how severely pressure has been raised. Treatment may protect vision or focus on eliminating pain.
A recheck is not simply a repeat of the first appointment. It assesses whether the original problem is improving, whether complications are appearing, and whether the treatment remains appropriate. The useful measures may include comfort, function, intake, body weight, examination findings, or selected tests. Ask which changes are expected before the visit and which should trigger an earlier call. Improvement in one sign does not always mean that every part of the disease has resolved.
Can risk be reduced?
Inherited susceptibility cannot always be prevented. Discuss screening and protection of the second eye when appropriate.
When should you arrange care?
- Seek immediate veterinary care for a suddenly red, painful, or cloudy eye, or for any sudden loss of vision.
Seek urgent veterinary advice if you notice:
DO NOT DELAY URGENT CARE- Sudden eye pain, redness, cloudiness or loss of vision needs immediate assessment.
What information helps the care team?
Write down when changes started, what makes them better or worse, actual food and water intake, and all medicines and supplements. Short videos and a medication-label photo can help describe changes that may not appear during the appointment.
How should you understand the tests?
Ask what each proposed test is intended to answer. Some tests identify a cause; others assess severity, organ function or treatment safety. Results are interpreted with the examination and history. A normal result does not exclude every problem, and an abnormal result does not always explain every sign.
Questions to ask before leaving
- What is confirmed, and which other explanations are still being considered?
- What changes should we expect with the proposed plan, and when should we reassess if they do not occur?
- Which observations should I record, and which changes mean I should call sooner?
- What medicine or home-care problems should I report, and what are the instructions for a missed dose or suspected side effect?
- When is the recheck, what will it assess, and whom should I contact after hours?
A care plan may be adjusted as results or the response become clearer. Keep the written instructions and tell the team if cost, handling or administration difficulty makes the plan hard to follow.
Sources behind this guide
Glaucoma in Dogs - Dog Owners - Merck Veterinary ManualVeterinary, university or animal-health guidance ↗Merck Veterinary Manual: Glaucoma in CatsVeterinary, university or animal-health guidance ↗Content last reviewed: October 4, 2026. Review status: veterinary-informed; independent veterinarian review not yet completed.