Can floater surgery cause a cataract?

Why does removing the gel affect the lens?

Oxygen reaches the inside of the eye mainly from the blood vessels of the retina, at the back. In a healthy eye the vitreous gel slows its movement forwards, and vitamin C (ascorbate) dissolved in the gel reacts with oxygen and uses it up. The result is that the lens, at the front of the gel, normally sits in a low-oxygen environment.

Vitrectomy replaces the gel with clear fluid. Fluid mixes freely, and the eye's store of vitamin C falls, so oxygen travels to the lens far more easily. Measurements taken during surgery show the change directly: the oxygen level beside the lens rose from about 9 to about 70 mmHg once the gel had been removed. That very high reading reflects the fluid used during the operation and is expected to fall afterwards, as it did in animal studies, but eyes that have had a vitrectomy in the past still have more oxygen near the lens, and less vitamin C, than eyes that have not.

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The centre of the lens, called the nucleus, is made of old cells packed with the proteins that keep the lens clear. It depends on a protective antioxidant, glutathione, which seeps in slowly from the outer layers, and this supply slows with age. Extra oxygen wears down that protection, the proteins clump together, and the centre of the lens gradually turns yellow-brown and cloudy. This is a nuclear cataract, the same type that develops with ageing, but arriving years earlier. The guide to what causes cataracts describes the other types.

Front viewSide view

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How sure are researchers about the oxygen explanation?

It is the leading explanation and it is strongly supported, although it has not been proven in a clinical trial, and much of the laboratory work comes from one research group. Several independent observations point the same way:

• People who have many sessions of hyperbaric oxygen treatment become more short-sighted, and some develop a nuclear cataract.
• People whose retina receives less oxygen because of severe diabetic eye disease develop less cataract after vitrectomy.
• In donated eyes, the more the vitreous gel has naturally turned to liquid, the more nuclear cataract there is, even allowing for age.
• When a retinal membrane was removed with an operation that left the vitreous gel in place, the lens did not change measurably over about two years.

A cataract after vitrectomy is therefore an expected effect of removing the gel. It does not, by itself, mean anything went wrong during the operation.

What else can contribute?

Oxygen is not the only factor. Others that can add to it are:

• Age and any existing clouding. An older lens, or one that already shows early cataract, is more likely to progress.
• An air or gas bubble. Gas is associated with faster progression, but it is not normally needed for routine floater surgery.
• Silicone oil. Used for some retinal detachments, not for floaters.
• Contact with an instrument. Rarely, an instrument touches the lens during surgery, which can cause a more localised cataract. In a large UK database this happened in about 1 to 2 in 100 vitrectomies on eyes with a natural lens.
• Light and operating time. Bright light from the surgical light pipe and the length of the operation have also been suggested, with less evidence.

Vitrectomy probe →1Infusion line →2Floaters →3Light pipe →4Retina →5+

1. Vitrectomy probe2. Infusion line3. Floaters4. Light pipe5. Retina

How common is cataract after floater surgery?

In eyes that still have their natural lens, published series of floater surgery report that roughly one in five to more than half of eyes went on to have cataract surgery, usually within about two years. The range reflects differences in age, surgical technique and length of follow-up.

In one large US practice, 36% of eyes with their natural lens had cataract surgery after limited floater surgery. By comparison, 8% of eyes in people who chose to wait rather than have surgery needed cataract surgery during a year or more of follow-up (some for many years), although the two groups were not strictly comparable. Series in which the surgeon removed more of the gel, often after separating it from the retina, reported about half of eyes or more. Across all types of vitrectomy, including retinal detachment repair, a US national registry estimated that 46% of eyes with a natural lens had cataract surgery within two years.

These figures describe groups of eyes. They count people who had cataract surgery, not everyone whose lens began to change.

Does age make a difference?

Age is the strongest factor that has been identified. In the largest series of limited floater surgery, 3 of 37 eyes (8%) in people under 50 went on to cataract surgery, compared with 40% of eyes in people aged 50 to 60 and 45% over 60. Studies of other kinds of vitrectomy show the same pattern: nuclear cataract progressed about six times faster in people over 50 than in those under 50, while each extra decade after 50 made little further difference.

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Fifty is not a sharp cut-off. A younger person may keep a clear lens for many years, and the three younger people in that series who did need cataract surgery were all short-sighted. If you are in your forties or younger, cataract is a less likely consequence, but not an impossible one.

How soon does a cataract develop?

When cataract surgery is needed after floater surgery, it has typically been about one to two years later on average, although it ranges from a few months to many years.

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The first sign is often a change in glasses rather than a cloudy view: as the centre of the lens hardens, the eye becomes more short-sighted, sometimes within three to twelve months of vitrectomy. Some people notice that their distance glasses seem too weak, or that they can read without their reading glasses.

Does the type of floater surgery matter?

Possibly. Floater surgery varies in how much gel is removed. Some surgeons remove mainly the central gel and leave a layer, about 3 to 4 mm thick, behind the lens, without deliberately separating the gel from the retina. This limited approach was designed partly to reduce cataract, on the basis of the oxygen research: the remaining gel should still slow oxygen on its way to the lens.

In one comparison of eyes followed for at least two years, cataract surgery was needed in 35% after limited surgery and 87% after more extensive surgery, and it came later after the limited approach. That is a large difference, but the groups were not randomised, they differed in age, and most of the evidence for limited surgery comes from one research group. Leaving gel attached to the retina also makes new floaters more likely later, particularly in younger, short-sighted people. The vitrectomy surgery page describes the operation itself.

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The size of the instruments makes no measurable difference to cataract. Modern small-gauge instruments reduce other problems, but in studies comparing gauges, nuclear cataract progressed similarly and the rate of cataract surgery was the same.

Can anything reduce the risk?

There is no reliable way to prevent it. No eye drop, supplement or diet has been shown to prevent a cataract after vitrectomy. The factors that seem to matter most are ones you cannot change, such as your age, or ones that depend on the operation, such as how much gel is removed and whether a gas bubble is needed.

The practical choices are about timing and planning rather than prevention:

• Waiting longer before floater surgery does not protect the lens from the effect of the operation, but it does give floaters the chance to settle so that surgery may not be needed at all. The eye floaters guide explains how floaters are assessed.
• For people with an early cataract, cataract surgery can be planned at the same time, before or after the floater operation.
• For a small group of floaters, laser treatment is an alternative that does not remove the gel. The article on YAG laser for floaters explains who may be suitable.

How would I notice a cataract developing?

A cataract after vitrectomy usually comes on gradually over months. Common signs are vision slowly becoming hazy, colours looking duller or more yellow, more glare from headlights or sunlight, and glasses that suddenly seem too weak for distance because the eye is becoming more short-sighted. Vision in the operated eye may seem noticeably different from the other eye when you compare them.

Because the change is gradual and painless, it is usually picked up at a routine review or when you notice the difference between your eyes. It is not an emergency. A sudden change in vision after vitrectomy is different and needs urgent assessment (see the final section).

What if I have already had cataract surgery?

If your natural lens has already been replaced with a lens implant, you cannot develop a cataract in that eye, so the main downside of floater surgery does not apply. Other risks, such as retinal detachment, remain.

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The thin capsule that holds the implant can become cloudy months or years after cataract surgery. That is a different problem, called posterior capsule opacification, and it is usually treated with a quick laser procedure. The article on YAG laser after cataract surgery explains it.

What happens if I need cataract surgery later?

Cataract surgery after vitrectomy is a common, well-established operation, and the aim is the same as usual: to replace the cloudy lens with a clear lens implant. The eye behaves a little differently during surgery because there is no gel behind the lens, and the fibres that hold the lens can be weaker, so the operation is planned with that in mind. The article on cataract surgery after vitrectomy explains what is different and what to expect.

For people who are short-sighted, the later cataract operation is also a chance to reduce their dependence on glasses, a point Dr Chen made in his 2018 review of floaters for optometrists. The article on cataract surgery with myopia covers the planning involved.

Should cataract surgery be done at the same time?

It can be, and it is worth discussing if you are over about 50 and a cataract is already starting. Combining the operations means one operation and one recovery instead of two, and avoids a cataract clouding the improvement from floater surgery a year or two later.

Against that, combined surgery removes a lens that may still be fairly clear and, in people in their forties or fifties, may still be focusing a little for near vision. Swelling at the centre of the retina (macular oedema) is more common after the lens is removed, whether at the same time or later. The evidence comparing combined and separate surgery for floaters comes from small, short studies, so the choice is individual. The article on whether cataract and retinal surgery should be done together or separately sets out the trade-offs.

Combined cataract and retinal surgery: time-lapse

Combined cataract and retinal surgery: time-lapse

Dr Chen performing cataract surgery and vitrectomy in one operation, shown as a 90-second time-lapse of real eye surgery.

Watch on YouTube →

Other questions about cataract after floater surgery

Where can I read more?

When should I seek urgent help?

A cataract develops gradually and is not an emergency. After floater surgery, contact your ophthalmologist urgently, or attend an emergency department, if you notice sudden loss of vision, severe or increasing pain, new flashes of light, a sudden shower of new floaters, or a shadow or curtain across part of your vision. These can be signs of a retinal tear or detachment, infection or bleeding. Do not wait for your next appointment.