Should my child have a lens implant (IOL) at the time of cataract surgery?
Different ophthalmologists have different points of view on whether to use IOLs in babies and young children. There is a lot of discussion on this issue in groups such as APHAKIC and PGCFA, but it’s often a decision that parents have to make very quickly after a diagnosis, before they’ve had much chance to even get used to the idea that their child has cataracts, or a cataract, let alone find out much more information. So, if you’ve just found yourself in this position, here’s our rough guide to the IOL debate.
What are IOLs?
IOLs are intra-ocular lenses. They are either made from a hard plastic called PMMA or a flexible acrylic, and they have two arms that are used to anchor them in position. They are usually placed in the lens capsule, where the natural lens of the eye used to be, at the time of the cataract surgery. Sometimes a lens is implanted at a later operation but then it rarely can be placed inside the lens capsule and then may be placed in the sulcus, on a preserved ring of the natural lens capsule, or stitched into the eye or, more recently, clipped to the iris. Virtually all older adults who have cataracts removed have IOLs put in; until recently, very few younger children had IOLs put in when they had their cataracts removed.
So what’s the debate?
IOLs cause more complications, especially in children under two years. Whilst many of these are minor complications not affecting a child’s eventual vision and health of eye, there is a greater chance of a second operation in the weeks following the cataract surgery.
The controversy is about major complications especially glaucoma with some surgeons arguing that glaucoma risk is reduced by an IOL and others concerned that in some eyes it may be increased by lens implantation. The younger that cataract surgery is done, the more complications may arise from the surgery whether an implant is used or not but in the case of most early cataracts early surgery gives the best vision result.
But why don’t they know which is better?
The serious complications are glaucoma and retinal detachment, and because they can happen many years after the surgery, really any time in the child’s lifespan, it’s just about impossible to work out which new treatment is better although in some selected groups of eyes there are early indications.
When reading the summaries of the positive publications it is important to know that eyes that receive IOLs will be those that are the best developed and those that are likely to have had the lower risk of major complications and the best chance of good vision.
What is very hard is that no two eyes are the same even, in some cases, in the same baby. Whilst an IOL may be a good option for some eyes it may not be safe or possible in another. These eyes will have different risk factors whatever the surgery or the surgeon and therefore parents rely on their surgeon to guide them as websites cannot give them specific guidance for their child. As decisions usually have to be made quickly it is rare that a parent can obtain a second opinion.
Surgeons will have a clearer idea as to how to guide families on the basis of evidence as more studies are done over the next decade, but that really doesn’t help those of us who are making the decision now. The other problem is that there aren’t large numbers of children with cataracts so the sample size for studies on this is small, which means that the statistics that researchers usually rely on to give them definite answers don’t work very well.
There is a study going on at the moment looking at whether IOLs or contacts are better for babies with unilateral cataracts called the Infant Aphakia Treatment Study (IATS) at Emory University in the US. Their website has information for parents who are participating in this study. A National study of IOL use in the under 2’s is about to start in the UK, (more details on this website soon). There are a number of other different studies in other places and we can hope that there will be some useful results from them in the coming years.
We are only really finding out now how treatments for childhood cataracts that were done in the 1930s have worked out long-term and we will have to wait for our children to grow up and grow old before we really know how good modern-day treatments are. By then of course, medicine will have moved on, so that’s why ophthalmologists differ in their opinions so much – and why they don’t like to give odds or statistics.
So what do they agree on?
Pretty much all surgeons would agree that if a child is over three, then putting an IOL in when the cataract is removed is a good idea. Exceptions to this are eyes that have developed a cataract because of inflammation inside the eye, subluxed lenes where the natural lens is unstable and off centre in the eye and in very small eyes. It’s not always possible to implant a lens safely – sometimes the capsule or bag around the lens breaks during surgery and they can’t fit it. It may be possible to fit an IOL in the sulcus if it can’t be put where the natural lens would go, but this may cause more problems in a child’s eye as it is less stable and the eye is more prone to inflammation than when it is wrapped inside the natural lens capsule.
There are quite a lot of studies that have been done that suggest that there aren’t so many risks and complications and it’s very useful to the child not to have to use aphakic glasses. However, as an eye is still growing the lens implant is not able to maintain perfect focus and glasses or a contact lens needs to be worn as well. At present IOLs are not changed as the eye grows and this would be a very difficult operation with current lenses and techniques.
They put in a lens that is planned to be close to the correct power to focus your child’s vision when their eye is fully grown. This has been compared to buying the pair of shoes for your daughter to wear with her wedding dress, when she is only a few weeks old. There is a good chance of getting the wrong size, but if it is close then any correcting glasses do not have to be very thick and she can see not her best but quite well without any correction. Your child then wears glasses which start off very thick to correct the deliberate under-correction in his or her lens until the eye grows up to fit the lens. When your child reaches about 4 years of age bifocal glasses are given as the IOL unlike the natural lens does not change shape to focus between distance and near. As more of this surgery is done they are getting better at working out the optimum IOL for an eye, but the chance of getting the wrong power of lens puts off some surgeons from thinking that it is a good idea for children under three (more in the US than in the UK)
And what don’t they agree on?
What to do for children under two!
Most sight is lost in children with unilateral cataracts not to surgical complications, but to amblyopia (the ‘bad’ or ‘lazy’ eye just not being rehabilitated), or due to the rest of the eye being abnormally developed. IOLs do not fully focus an infant’s eye and for optimum focus glasses or a contact lens need to be worn in addition, but they have the advantage that the eye has some focus even when this ‘fine tuning’ correction is not worn. This is one of the reasons that some surgeons feel that, although there are more surgical complications, there is a better chance of useful vision for a child with a unilateral cataract if they can implant an IOL. However, many eyes with a congenital unilateral cataract may be too small to safely implant a lens.
Implantation of an IOL in children in the first year of life with bilateral cataracts is more controversial. Some surgeons argue that more vision is lost to surgical complications than to amblyopia in children with bilateral cataracts, and that this outweighs any advantage that a constant optical correction has. They would advise correction with contact lenses or thick glasses alone and consider a secondary operation much later in childhood, and that it is better not to implant them in under-twos with bilateral cataracts.
There is some evidence that a major complication of infant cataract surgery, glaucoma, may be lower in implanted eyes. As surgical techniques and lens implants improve, complications of cataract surgery both with and without IOL have reduced especially in specialist centres. Other surgeons would say that IOLs in babies are still too experimental and therefore too risky to use at all
Each decision is unique and the surgeon will take into account other risk-factors, not just your baby or child’s age when advising on the best type of surgery. There really isn’t a right answer to what to do although medical opinion will probably swing one way or another in this debate over the coming years.
Treatment in other countries is often different. It may be that IOLs are sometimes chosen by surgeons and parents because of the difficulty or cost of getting aphakic glasses or contact lenses on medical insurance policies, which is usually not an issue in the NHS in the UK. It may also be that many surgeons are more cautious about using IOLs in young children in the States because of the greater risk of being sued for trying a newer treatment. It’s well worth bearing all this in mind on international groups such as the APHAKIC and PGCFA Yahoo groups.
Checked for medical accuracy by Miss Isabelle Russell-Eggitt, Consultant Paediatric Ophthalmologist, Great Ormond Street Hospital, London