Vision loss in a parrot: cataracts, the signs in a flying bird, and adapting the cage

Quick answer

The eye is the easiest organ in a parrot to inspect and the one most often looked past. A close look in good daylight, once a month, is the whole routine.

A parrot losing its sight rarely looks ill. It looks clumsy, then cautious, then quiet, and every one of those is usually put down to age or mood.

The check that matters is not the one most owners try. Shining a light at a bird's eye and watching the pupil tells you almost nothing, because a bird's iris is under voluntary muscular control. Parrots widen and narrow their pupils on purpose. Judge vision by behaviour and by looking at the eye itself.

• A pupil that looks white, grey or milky in daylight is a lens change and needs an avian vet.
• An African grey's iris lightening from dark to pale yellow as it matures is normal, and is constantly mistaken for a cataract.
• Confidence inside a familiar cage proves memory, not sight. Test in the parts of the day and the room where the light is poorer.
• Never rearrange the cage of a bird you suspect cannot see well.
• Increasing night frights in an older bird are often the first real sign, because a bird that cannot orient in the dark cannot stop thrashing.

Decide in 60 seconds

Why the mammalian eye tests do not transfer

The pupil is voluntary.

In mammals the iris is smooth muscle, so pupil size is an involuntary reflex and a genuine window on the nervous system. In birds the iris muscle is striated, the kind of muscle an animal controls deliberately. Parrots pin and flash their eyes as a communication signal, which is only possible because they are choosing to do it.

The consequence is direct. A parrot's pupil constricting when you shine a light does not prove the eye is working, and a pupil that stays wide does not prove it is not. Anyone assessing a bird's vision from the pupil is guessing.

The same fact explains a practical problem at the vet. The dilating drops used routinely in dogs and cats act on smooth muscle and do very little to a bird's pupil, so examining the back of a parrot's eye properly requires either specialist drugs or a specialist.

The retina is built differently.

A bird's retina has no blood supply running across it. Instead a heavily folded, pigmented structure called the pecten projects into the eye from the optic disc and supplies the retina by diffusion. This is part of why avian eyes achieve such high resolution: nothing casts a shadow across the light sensing surface.

It also means retinal problems in birds do not look like the ones a vet is used to seeing in mammals, and it is another reason avian ophthalmology is its own field.

Vision does more work in a bird.

A parrot flying across a room is solving a continuous three dimensional problem at speed with almost no margin. It also selects food partly by ultraviolet cues we cannot see, and reads other birds by them.

Losing a portion of that is not equivalent to a person needing glasses. It changes what the animal can safely do, which is why the practical part of this article is about the cage and the routine rather than about drops.

Reading the eye itself

A mature grey's iris is pale. In a young grey it is dark, and the change between them is normal maturation, not disease.

Do this in daylight, near a window, without a torch and without flash. Photograph each eye straight on and from slightly in front, once a month, and keep the images dated.

The pupil.

Look at the colour of the pupil itself, not its size. It should be black and clear. White, grey, blue-grey or milky means the lens or the material behind it has changed, and that is the classic cataract appearance.

The iris.

Colour varies enormously by species, sex and age. In African greys, dark in a young bird and pale yellow in a mature one is the normal sequence. In cockatoos, iris colour differs between the sexes in many species. Change is only meaningful if it is asymmetric, sudden, or accompanied by anything else.

The surface.

The cornea should be glossy and perfectly clear, so that a window reflects cleanly off it. Any dullness, haze, blue tinge or roughness is significant.

The lids and the surrounds.

Swelling, thickening, crusting, matted feathers, or a change in the shape of the eye opening. In a bird on a seed based diet these point towards vitamin A deficiency, which thickens the tissues around the eye and blocks the ducts before it does anything more dramatic.

Symmetry.

Compare left with right in the same photograph. Almost every meaningful eye finding shows up as a difference between the two.

What causes it, and how the causes differ

Cataract.

The commonest cause of gradual vision loss in an older parrot, and reported most in the longer lived species that people keep for decades. It can also follow inflammation inside the eye, follow trauma, or accompany a metabolic problem.

It looks like a whitening of the pupil and it progresses over months. The bird adapts as it goes, which is why owners often date the onset to the week they finally noticed.

Trauma.

Window strikes, night frights, ceiling fans, a cage mate, and cat or dog contact. Sudden, usually one sided, usually with a squint and often with visible damage. A cat related injury is an emergency regardless of how minor it looks, because of the bacteria involved.

Inflammation inside the eye.

Uveitis, from infection or from disease elsewhere in the body. The eye looks dull, the iris colour may change, and the bird is uncomfortable. Chlamydiosis, mycobacterial disease and fungal disease can all present this way, and all three have implications beyond the eye.

Vitamin A deficiency.

Widespread in seed fed birds and entirely preventable. It damages the glandular tissue around the eye and the respiratory tract, producing swollen lids, discharge, and repeated infections that never quite resolve.

Neurological and toxic causes.

Heavy metal poisoning, head trauma and brain disease can blind a bird whose eyes look completely normal. The distinguishing feature is a normal looking eye with abnormal behaviour, often alongside other neurological signs such as head tilt, incoordination or seizures.

The behavioural signs, in the order they appear

Approach a bird with reduced sight from the front, in its field of view, and speak first. An object arriving unseen beside the head is what causes falls and defensive bites.

Early, and easily missed.

Reluctance to fly when the light drops. Landing short or long. Hesitating at the cage door. Reaching for your hand and touching with the beak before stepping up, more than it used to. Taking a treat by feel rather than reaching straight for it.

Established.

Staying on one perch. Reluctance to move around the cage. Increasing night frights, because a startled bird that cannot see cannot find a landing point and keeps crashing. Contact calling more than usual. Turning the head consistently to inspect things with the same eye.

Advanced.

Falling from the perch. Not flying at all. Startling badly when touched. Difficulty finding the food bowl if anything about its position has changed. Reduced grooming of the areas it cannot see.

Two things are worth saying plainly. Birds hide disability extremely well, and a familiar cage lets them run almost entirely on memory. And every sign on this list is also produced by arthritis, by pain, and by general illness, which is why the eye examination and the physical examination happen together.

What the vet will do

A full ophthalmic examination, usually with magnification, comparing both eyes. Fluorescein stain to show corneal ulceration, which is invisible without it.

Examination of the back of the eye where possible. Expect a discussion about referral here, because dilating a bird's pupil is genuinely difficult and a specialist ophthalmologist has both the drugs and the equipment.

A general examination, weight, and usually blood work, because eyes go wrong as part of systemic disease more often in birds than in mammals. Testing for chlamydiosis where the picture fits. Imaging of the head after trauma. Blood lead and zinc where poisoning is possible.

Treatment depends entirely on the cause. Ulcers and uveitis are treated medically and urgently. Vitamin A deficiency is corrected through the diet, which is slow and permanent rather than fast. Cataracts can be removed surgically in birds by veterinary ophthalmologists, most often in larger species, under general anaesthesia, and availability is limited in most of the world. For many birds the honest plan is management rather than surgery, and that is not a failure.

Living with a parrot that cannot see well

What never to do

Do not judge vision by the pupil. In a bird it is a voluntary muscle and it proves nothing.

Do not put any drop, ointment or rinse in a bird's eye without an avian vet examining it first.

Do not rearrange the cage, move the perches, or redecorate the room.

Do not assume a lightening iris in a young African grey is a cataract. It is normal maturation.

Do not let a bird with reduced vision free fly in an open room, and do not solve that by clipping its wings without discussing the trade-off, because a clipped bird crashes rather than lands.

Do not test vision by startling the bird or by moving a hand quickly at its face. Birds respond to the air movement and to your body language, and you will get a false reassurance.

When to get help

A bird that knows its space, moving confidently in it. That confidence is worth protecting, and it depends on the space staying the same.

Same day, treat as urgent:

• A squint, a held-shut eye, or any swelling of the lids
• Any injury to the head or face, especially from a cat or another bird
• Sudden loss of vision with normal looking eyes, which points at the brain rather than the eye
• Blood in or around the eye
• A bird that has stopped eating alongside any eye change

Book within the week:

• A pupil that looks white, grey or milky
• Repeated night frights in a bird that did not have them before
• Landing errors, falls from the perch, or a bird that has stopped flying
• Discharge or matted feathers around the eye in a seed fed bird
• Head always turned to inspect with one eye

Bring the dated eye photographs, the weight record, a video of the bird moving around its cage and landing, the exact diet including the brand, the age of the bird if known, the cage layout, and a note of any head knock, night fright or fight in recent months.

Ask two questions before you leave: whether a fluorescein stain was done, and whether the back of the eye could be assessed or whether referral is needed to see it. The answers determine whether you have a diagnosis or only a description.