Double vision after cataract surgery – why it happens and when to see a doctor

Double vision after cataract surgery frightens many patients, especially when it appears after an operation that was supposed to improve their vision. In most cases there is an explanation, and it is often temporary. Still, there are situations in which it needs to be checked. On this page we explain how to tell the types of double vision apart, what the possible causes are, what you can do, and when to see a doctor right away.

A simple test: one eye or both eyes?

The first thing to check is whether the doubling appears in one eye or only when both eyes are open. Cover each eye in turn, gently and without pressing on the operated eye:

• Double vision in one eye: the doubling or "shadow" stays even when the other eye is closed. The cause is usually in the eye itself, for example on the surface of the eye or in the lens.
• Double vision of both eyes: the doubling disappears when you close either eye. In this case the problem is usually in the coordination between the two eyes, not in one eye.

Write down what you found and tell the doctor at the check-up. This information helps the doctor quickly understand where the problem comes from.

Common causes in the first days and weeks

In the first stage after surgery, the patient may have blurred vision, mild irritation and extra tearing, which can last from days to a few weeks. During this time the eye is still healing, and its surface may be a little swollen or dry. All of these can cause a blurred image with a "shadow", which patients describe as double vision in the operated eye. In most cases this improves as the eye heals.

Dry eye is a particularly common cause. Temporary dryness of the eye is known in the days and weeks after surgery, and when the surface of the eye is not smooth, the image can look double or smeared and improve for a moment after blinking. As for lubricating drops, ask the doctor before adding any drops to the drops you were given after surgery. More information on the page Blurred vision after cataract surgery.

The period between the first and second eye

The time between the first and second operation is sometimes the least comfortable part of the process. The operated eye now sees through a new, clear lens, while the other eye still sees through a cloudy lens. If the glasses prescription in the operated eye has changed, the eyes may work less well together, and in some cases there may be a feeling of discomfort or a headache.

When the difference between the eyes is large, the brain may find it hard to combine the two images into one, and double vision of both eyes appears. In most cases the feeling of imbalance goes away once the second eye is operated on too. If it greatly disturbs daily life, tell the doctor, because it may affect the planning of the timing of the second operation. More information on the page Cataract surgery in the second eye.

Less common causes

• An existing tendency to squint: some people have a mild tendency to squint that the brain has made up for over many years. When the vision in one eye was weak because of the cataract, the tendency was not felt, and after surgery it may show up as double vision of both eyes.
• Remaining astigmatism: astigmatism that was not fully corrected can cause an image with a "shadow" in one eye. This can often be corrected with glasses once the vision stabilises.
• Movement of the artificial lens: movement of the artificial lens inside the lens capsule can cause double vision or even seeing the edge of the implant. This is rare, and the ophthalmologist can detect it during an examination. More information on the page Cataract surgery complications.
• Secondary cataract: sometimes, months or years after surgery, the membrane behind the artificial lens becomes cloudy. This causes blurring and sometimes also a double image or glare, and it is usually treated with YAG laser. See Secondary cataract.

What you can do

• Keep using the drops exactly as instructed, and do not stop them on your own.
• Give the eye time to heal. In most cases, full recovery usually takes four to eight weeks, and the pace of recovery differs from person to person.
• Do not drive when you have double vision, even if it only appears from time to time. More information on the page Driving after cataract surgery.
• Do not rush to get new glasses. Permanent glasses are usually fitted only after the vision has stabilised, and often only after both eyes have been operated on. Until then, the doctor or optometrist may suggest a temporary solution.
• Tell the doctor at the check-up what you checked: whether the doubling is in one eye or both, whether it is horizontal or vertical, and whether it changes during the day.

How double vision is treated when it does not go away

Treatment depends on the cause. Dry eye is usually treated with drops as recommended by the doctor. A difference in prescription between the eyes usually settles after surgery on the second eye or with glasses. When the problem is in the coordination between the eyes, glasses with a prism may be recommended, and sometimes a referral to a doctor who specialises in squint. Secondary cataract is treated with YAG laser. In the rare cases where the lens has moved out of place, the doctor will discuss the options with you, and sometimes a further procedure is needed.

When to see a doctor right away

Contact your treating doctor right away if the double vision comes with any of the following signs:

• Eye pain that gets worse instead of better.
• Reduced vision, especially after the vision had already improved.
• Redness or swelling that is increasing, or discharge from the eye.

Double vision that appears suddenly together with a severe headache, a drooping eyelid, weakness in the face or limbs, or a speech disturbance may point to a problem not related to the surgery, and requires going to the emergency room immediately.

For the full list of instructions for the recovery period, see Cataract surgery recovery.