Sudden blindness in an older cat is a blood pressure problem until proven otherwise. Three patterns account for most of what a vet sees at the back of the eye: bleeding, fluid leaking under the retina, and slow thinning of the retina itself. Only the third is inherited and quiet for months; the first two can appear within 24 to 72 hours, and both sit on a systolic reading above 160 mmHg.
The 3 types at a glance
| Type | What the vet sees | Speed of onset | Systolic pressure that fits | First recheck |
|---|---|---|---|---|
| 1. Hemorrhage | Red patches 1-3 mm, flame shaped, retina still attached | 24-72 hours | 180 mmHg or higher | 7 days |
| 2. Fluid under the retina | Grey veil over the tapetum, retina lifted 2-5 mm | 2-10 days | 160-200 mmHg | 7-14 days |
| 3. Degeneration, early | Brighter tapetum, vessels narrowing at the edges | 6-12 months | Normal, under 160 mmHg | 8 weeks |
| 3. Degeneration, late | Pale flat disc, vessels hair thin, both eyes even | 12-24 months | Normal, under 160 mmHg | 12 weeks |
The split matters because the first 2 types can be stopped and sometimes reversed, while the third cannot. A cat with the wrong label gets either a course of treatment it did not need or a wait that costs the last of its sight.
Type 1: blood on the retina
Bleeding shows as red patches 1 to 3 mm across, often following a vessel, sometimes with a pale center. It can sit inside the retina, under it, or in the vitreous, where it looks like smoke and blocks the view of everything behind it. A cat with a small patch may still track a moving hand; a cat with blood in both vitreous bodies usually starts bumping into furniture within 24 to 48 hours. This is the pattern that goes with the highest pressure: a reading of 180 mmHg or more plus hemorrhage means treatment starts the same day, not at a recheck.
Type 2: fluid under the retina
A serous detachment looks like a grey sheet laid over the tapetum, and the retina shifts 2 to 5 mm as the fluid moves when the head is tilted. This is the type most likely to reverse. If systolic pressure comes under 160 mmHg within 72 hours, the retina can settle over 5 to 21 days and part of the vision often returns. A detachment that lasts 4 weeks or more leaves folds that never flatten, and the surface then looks pale and wrinkled on every later exam.
Type 3: the retina thins
Inherited degeneration, and the late atrophy that follows other eye disease, moves slowly and evenly. The tapetum turns more reflective across 6 to 24 months, vessels narrow from the edges inward, and the disc flattens. Owners describe night blindness first: the cat hesitates at a doorway at dusk, then stops jumping onto a 1 m table, then walks with its nose near the floor. Both eyes change within 2 to 4 months of each other and blood pressure is usually normal, which is exactly why the other 2 types have to be ruled out before anyone uses the word degeneration.
Where blood pressure fits
Systolic pressure is the number that drives the decision. Under 160 mmHg is normal in a quiet room. From 160 to 179 mmHg a recheck in 2 to 4 weeks is reasonable. At 180 mmHg or above, or with a diastolic over 120 mmHg, the eye, kidney, heart, and brain are all at risk and treatment usually starts at once. One high reading is not a diagnosis: take 5 to 7 readings over 20 to 30 minutes, discard the first 2, and repeat on a second day. White coat effect adds 10 to 15 mmHg, so 165 in a hissing cat is not the same number as 165 in a relaxed one.
Why the kidney is part of an eye exam
Chronic kidney disease is the most common cause of high pressure in cats over 10 years, and the eye is often where it is found first. That is why a fundus exam belongs with every senior panel, and why a cat with a creatinine of 2.5 mg/dL and a pressure of 190 mmHg needs both problems handled together. Urine protein, read as a ratio, is the other number to follow, and early kidney signs lists what changes before creatinine moves.
Timing of the rechecks
Fundus exam on day 1. Pressure recheck at 7 days, because that is when the first drop should show. Second fundus exam at 4 weeks to see whether a detachment has flattened. Third at 8 weeks, when the retina has either settled or scarred. If both eyes are blind and the pupils stay wide at 48 hours, the chance of useful vision returning drops sharply, and the conversation should move to safety at home rather than to more tests.
What an owner can test at home
Three checks, once a week, in the same room at the same light level. Drop a cotton ball from 30 cm and watch for a head turn. Move a hand toward the eye from 20 cm and look for a blink. Put a chair in a new spot and see whether the cat walks around it or into it. Write the result next to the date; a cat that stops blinking at week 4 needs a recheck, not a wait.
When to call the vet today
Sudden blindness with pupils that stay large in bright light, a red eye, or a pupil that no longer reacts is a same-day visit. So is a cat that walks into walls after a jump of 1 m or more, or one that starts pressing its head against furniture. A head tilt with blindness points to a different problem, and vestibular disease explains the 3 patterns that mimic it. Any of these with a pressure of 200 mmHg or more is an emergency, not a next-week appointment.
Five steps for this week
- Get a pressure reading before any eye drops are started, with 5 to 7 readings over 20 to 30 minutes.
- Book the kidney panel and urine protein ratio, since the eye finding usually comes with both.
- Photograph both pupils in a bright room and in dim light, and keep the 2 images with the date.
- Keep furniture in place for 2 to 4 weeks and block the stairs, so a blind cat can map the room.
- Read the cost estimate before the workup, because pressure checks repeat at 7 days, 4 weeks, and 8 weeks.
Terms mentioned in this article
Frequently asked
Can a cat regain vision after hypertensive retinal detachment?
Sometimes, and the window is short. If systolic pressure is brought under 160 mmHg within 72 hours, the retina can settle back over 5 to 21 days and part of the vision often returns. Detachment lasting 4 weeks or more leaves folds that do not flatten, and sight in that eye is usually lost.
How many blood pressure readings are needed before calling it hypertension?
At least 5 to 7 readings taken over 20 to 30 minutes with the first 2 discarded, then a repeat set on a second day. A single reading of 165 mmHg in a frightened cat proves little, because white coat effect alone can add 10 to 15 mmHg.
How do I tell inherited degeneration from a pressure problem?
Both eyes changing evenly over 6 to 24 months with a normal pressure points to degeneration. Sudden loss, uneven pupils, bleeding, or a raised retina 2 to 5 mm high points to pressure. A fundus exam plus a pressure reading separates the two in one visit.