REFRACTIVE SURGERY CAN IMPROVE VISUAL OUTCOMES IN SELECTED CHILDREN

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Increasing evidence suggests that refractive surgery can improve the visual outcomes and binocularity of selected children with amblyopia, accommodative esotropia, and high myopia in whom conventional therapies have failed. However, the long-term risks are unknown and critics of such approaches have questioned the quality of the evidence.

The conventional treatments for amblyopia and high ametropia include optical correction with glasses or contact lenses and, in the case of amblyopia, patching or atropine in the better eye. In the majority of cases those interventions can produce satisfactory results with a corrected visual acuity of 20/40 or better in both eyes.

However, in a small proportion of children the treatment will fail, despite the best efforts on the part of their parents, their physicians, orthoptists and optometrists. The failure can be due to a number of reasons. For example, amblyopic children with high degrees of anisometropia can have overwhelming difficulties with spectacles because of the disparity between the sizes of the two images they present to their two eyes. Moreover, children with very high myopia require thick glasses that can cause a disturbing prism effect.

Contact lenses can produce excellent optical results in many such cases but require a lot in the way of supervision on the part of the parents and cooperation on the part of the children. Compliance with spectacle and contact lens use and patching can also be extremely difficult hurdles to overcome in some children with neurobehavioural disorders, such as autism and Down’s syndrome.

The main types of refractive surgery that have been performed in children have been LASIK, surface ablations such as LASEK and PRK, and the implantation of phakic IOLs, such as the iris-fixated Artisan and Artiflex IOL. The results of many studies have indicated that the techniques can produce satisfactory outcomes, but they all have their potential drawbacks.

For example LASIK could in theory present a greater risk of flap complications in children than in adults, not only from eye-rubbing but also from the normal rough-and-tumble in which children commonly engage. Moreover, the depths of ablation required in many cases could put the patients at risk for ectasia. For the same reason, surface ablation procedures could entail an increased risk of haze. Phakic IOLs, meanwhile, might pose a higher risk to the corneal endothelium than would be the case in adults, given the additional decades the IOL would be in the eye.

So far, so good

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Those who practise paediatric refractive surgery maintain that their experience shows that concern about the risks, while understandable, has been somewhat exaggerated. Moreover, they argue that the studies conducted to date indicate that not only does refractive surgery appear to be effective in the treatment of amblyopia and high ametropia, but it is also as safe in children as it is in adults, with little evidence of the most feared potential consequences.

“All clinicians should consider this therapy for children where traditional methods fail. If you laser the refractive error away the vast majority of children that had not previously responded to conventional treatment will respond to it afterwards,†said William F Astle MD, FRCSC, Alberta Children’s Hospital, University of Calgary, Calgary, Alberta, Canada, in an interview.

He said that in his experience of treating paediatric patients over the past 12 years with surface ablations such as PRK and LASEK for refractory anisometropia amblyopia and bilateral myopia, treatment has resulted in an overall improvement in best-corrected visual acuity and stereopsis with fairly predictable refractive outcomes with minimal to no haze.

For example, a five-year follow-up review of 56 eyes of 39 paediatric patients who underwent PRK or LASEK at a mean age of 6.5 years showed that the mean spherical equivalent was -1.73 D. Prior to surgery they had more than 3.0 D of anisometropic amblyopia and/or more than -5.0 D of bilateral myopia (Astle et al, J Cataract Refract Surge 2008; 34: 411-416).

Moreover, among 28 eyes in which visual acuity was measurable preoperatively, there was a mean improvement of 1.6 lines, with a range of zero to seven lines of improvement. In addition, 19 (49 per cent), had measurable stereopsis after surgery, compared to only seven patients (18 per cent) preoperatively. Furthermore, none of the children had a reduction in BCVA or binocular fusion postoperatively.

In addition, in their responses to a quality-of-life questionnaire, parents noted numerous improvements in the behaviour and general demeanour of the children following their treatment and over 90 per cent said they would recommend LASEK for children with similar problems, Dr Astle said. He noted that although trace corneal haze occurred in nine patients, all cases resolved over time.

“In our initial studies we had three or four children who were a little over the -15 D range who got significant haze that we had to re-laser. But at about that time LASEK came on board and we added mitomycin to the mix. That combination of LASEK and mitomycin virtually eliminated that problem, so haze is never a significant issue anymore,†Dr Astle said.

He noted that an inherent difficulty with corneal ablative techniques in very young children is that they require the use of general anaesthesia. Therefore children cannot fixate during the procedure. However, Dr Astle said that the iris recognition capabilities of the Technolas laser he now uses could provide an acceptable result. Patients tended to have a satisfactory resolution of their anisometropic amblyopia if the refraction of their treated eye was within two or three dioptres of their fellow eye, he added.

Moreover, as the patients’ eyes grew, the normal myopic shift that occurs as a child grows generally occurred at the same rate in the two eyes, maintaining their refractive balance. He added that he currently corrects them by about a dioptre extra to compensate for the myopic shift of the children’s growing eyes. “You get the occasional outlier where you have to tweak it again but usually they'll shift at the same rate in both eyes,†he added.

Long follow-up with LASIK

Dr Michael O’ Keefe FRCS, Mater Private Hospital, Dublin, Ireland, said that his 10-year results with LASIK in a small series of seven eyes of six amblyopic children show that postoperative refraction has remained fairly stable throughout the follow-up period and that five children achieved an improvement in visual acuity.

The study involved children ranging from two to 12 years in age. In their treated eyes the mean preoperative spherical equivalent was -10 D and ranged from -5.00 D to -16.0 D and the mean preoperative visual acuity ranged from hand movements to 6/18.

After a mean follow-up of 9.5 years the mean spherical equivalent was -4.3 D, compared to -9.6 D preoperatively. In addition, visual acuity improved by a mean 2.5 Snellen lines in six eyes, although one eye remained amblyopic. Postoperative visual acuity ranged from 6/6 to 6/60. One child gained no improvement because of non-compliance with postoperative patching.

“My findings were that I didn't have any complications and my youngest was aged two. Those that improved were the ones that I did early and could patch later. There were no flap complications and no signs of ectasia,†Dr O’Keefe told EuroTimes.

Another finding was that there were no complaints from the children regarding photic phenomena, despite the high amounts of aberrations the procedure produced, he said.

“We didn’t have wavefront-guided ablations or any of those things, so we induced a lot of higher order aberrations on these corneas. But none of these children complained about haloes or glare of any form so maybe they have some sort of adaptation but they don’t get any of the symptoms associated with higher order aberrations,†he said.

Phakic IOLs becoming more favoured option

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Dr O’Keefe told EuroTimes that since conducting those cases he has converted from the corneal ablative approach to a lenticular approach using Artisan and Artiflex iris-clip IOLs, which he said have become the preferred option for most practitioners of paediatric refractive surgery in Europe. He noted that he has been using the lenses in children and has found that they appear to produce very predictable results.

“Implants have become the more common option for amblyopic anisometropia for a number of reasons. First of all, there is quicker rehabilitation, second it can be done in the ordinary operating room and can be done by surgeons who don't have any expertise in using lasers or for cutting flaps or doing corneal refractive surgery, and of course it's also less expensive because you don't need all this equipment.“

An additional advantage of phakic IOLs is that they can be replaced if refraction changes significantly as the child grows. Furthermore, it leaves the cornea largely untouched, leaving the option open for future corneal ablative procedures.

On the other hand, some have expressed concern that although the Artisan lens has a proven track record regarding safety in the adult population, the situation is less clear in children, given the short follow-up available to date and the greater number of years the implants would likely be in the child’s eye.

“These implants have been used for a greater period of time in Europe than in the US. However the 15-year experience in an adult eye is not comparable to the same 15 years in a child's eye. My particular concerns are low-grade iritis and pigment dispersion, along with gradual but inexorable endothelial cell loss. We may or may not find that in 15-20 years we are explanting phakic IOLs placed in children, and/or performing lamellar corneal transplantation,†said Sandra Brown MD, Cabarrus Eye Centre, Concord, North Carolina, US.

However, Dr O’Keefe said the benefits may justify the risks, particularly since in his experience to date the implants have been as free of complications in children as they have been in adults.

“My experience to date is that these implants work really well in children as well. We haven't seen pigment dispersion in adults or children in any shape or form and although we haven’t done endothelial cell counts we have no reason to believe the results will be different in children than adults. Another thing that critics of refractive surgery in children say is that children might displace their implant by rubbing their eyes, but again, I don't buy into that either,†he said. 'I have shown significant improvement in all vision specific sub-scales of National Eye Institute VFQ-25 using foldable iris-fixated intraocular lens implantation in a subset of paediatric patients with special refractive needs who were intolerant of conventional treatment (article published in Acta Ophthalmol February 2012).'

Patient selection still a matter of debate

The current indications for paediatric refractive surgery include anisometropic amblyopia, high bilateral high myopia and accommodative esotropia that has not responded to conventional treatment. Those who perform such procedures say that eligibility for such procedures is often obvious at an early stage.

“The anisometropic amblyope, the classic one, is a child who starts at 20/400 and after patching treatment they get to 20/80 but no matter what you do it won't change. If you’ve done six months to a year of traditional treatment and it's really not responding you can add this to the armamentarium,†Dr Astle said.

On the other hand, while there is a broad consensus that an essential eligibility criteria for paediatric refractive surgery in a given patient is the failure of conventional treatment, there appears to be less agreement about what actually constitutes treatment failure. And some have expressed concern that the availability of refractive surgery for children with amblyopia and high ametropia may cause the parents of affected children to regard it as an easy option.

“If by ‘failure’ it is meant that the parent comes back and says the child didn't want to wear glasses, I would have that every day. And if we told those families: 'by the way, if you fail wearing glasses, then we will laser the child,' how many of those families would've failed the glasses, knowing they had another option?†said David B Granet MD, UCSD Ratner Children's Eye Centre, La Jolla California, US.

He noted that in a study he conducted a few years ago involving children with hyperopic anisometropia he was able to achieve satisfactory results in 97 per cent of cases. He noted however, that he had fewer qualms about recommending refractive surgery to children with refractive disorders who have neurobehavioral disorders.

“You have a child with autism, cerebral palsy, Down's syndrome, or some other behavioural issue who for some reason will not wear glasses or cannot wear glasses. By doing refractive surgery on them you give them the opportunity to re-engage with the world and see clearly and interact. To me that falls into the category of a blessing, it is a blessing to be able to do that for that child because those kids really need our help, and they really have no other choice,†Dr Granet said.

Dr Brown said that she has seen some interesting preliminary results in a study involving developmentally delayed children with bilateral high myopia who underwent phakic IOL implantation.

“The study was spearheaded by Evelyn Paysse MD and has a more rigorous design vis-à-vis measuring 'soft' outcomes like socialisation, mobility, and environmental awareness. Rather than showing considerable improvement in these paramaters, the early data showed a slower rate of decline compared to age-matched normal children. I do not think this surgery should be offered outside of an IRB-sanctioned investigation with a safety monitoring committee,†she added.

Dr Brown noted she had more reservations about performing corneal photoablative procedures in paediatric eyes. She said that such procedures would be best restricted to very cooperative patients who could undergo wavefront-customised treatment, and even then, only if testing with contact lenses could prove that definite gains in binocular vision were possible.

“Such gains would include better oculomotor alignment if strabismus is present, and markedly improved stereopsis. Ideally the patient would reliably and convincingly report improvement in activities of daily living when wearing a contact lens as opposed to spectacles or no optical correction, although such self-reports must be interpreted with caution,†she said.

Dr Brown has published several articles in ophthalmology journals criticising paediatric refractive surgery as currently practised. She said her principal objection has been that investigators have focussed mainly on refractive outcomes and visual acuity, but with, in her opinion, inadequate attention to the child’s binocular quality of life.

“When you propose an operation with inherently unknown long-term complications, you have to be honest with parents and patients about how the surgery is going to change the child's life for the better. And the answer to this question needs to be concrete and relevant to the particular child in question,†she told EuroTimes. 'It needs to positively affect the child's function with both eyes open.'

Meanwhile, proponents of paediatric refractive surgery argue that the benefits to children are clear from the results thus far achieved. They warn, furthermore, that an overly cautious attitude to paediatric refractive surgery could result in a lot of children not receiving treatment at an age when it would be most effective.

“I think that the time to consider paediatric refractive surgery is now because there are a lot of people around the globe who are looking into this and we’re all getting the same results and it works extremely well. I'm not suggesting that we laser every child who wears glasses, but for the ones who are falling through the cracks and struggling and not doing well it's the way to go and it's time to really consider it seriously because it really works,†Dr Astle said.