HIGH HYPEROPIA

There are some children with high hyperopia who are intolerant of spectacles or contact lenses but who appear to benefit significantly from surgical refractive correction, according to Ken Nischal FRCOphth, Children’s Hospital, University of Pittsburgh, US.

“We know that hyperopia will not only cause amblyopia but will also have a behavioural effect if it’s left uncorrected. Nonsurgical management of high hyperopia is very successful in the majority of children. However, there is a minority of children who don’t cope with conventional therapies and they are the ones we hope to help with refractive surgery,” Dr Nischal said at the XXXI Congress of the ESCRS in Amsterdam.

Studies have shown that, without correction, there is a high risk of amblyopia in cases where there is more than 4.0 D of bilateral hyperopia, anisometropic hyperopia of greater than 1 D or hyperopic astigmatism of greater
than 1.5 D.

Moreover, hyperopia can have permanently damaging consequences for a child’s fine motor skills and education. There is a great volume of published research showing that children with hyperopia of greater than 4 D tend to have a lower level of educational achievement at primary school level.

Surgical approaches

The types of refractive surgery available today for highly hyperopic children include corneal ablative procedures and phakic IOLs, Dr Nischal said.

In a study involving 47 children who underwent LASEK to treat up to 12.5 D of hyperopia, all eyes were within 2.0 D of emmetropia and, overall 41.7 per cent had improvements in their corrected distance visual acuity. Among children with hyperopia with anisometropia, 83 per cent of eyes were within 1.0 D of the fellow eye and 65 per cent had improvements in uncorrected visual acuity (Astle et al, J Cataract Refract Surg 2010 ; 36, : 260-267).

Dr Nischal noted that in cases where there was more than 5 D of hyperopia, the researchers applied a 0.02 per cent solution of mitomycin-C to the corneal surface for 60 seconds.

“I think it is a bit of a worry because we’re already talking about the possibility of ectasia from corneal refractive procedures in adults. The addition of mitomycin-C on a more elastic tissue, one that is going to continue to grow, I think that for me would be a concern.”

Another finding of the study was that hyperopia appeared to diminish over time after LASEK rather than progress and patients came closer to the optimal refraction as the duration of follow-up increased. The study’s lead author has suggested that the progression that would normally occur is offset by the regression that usually follows correction of high refractive errors.

“We know refraction improves and that's good. But at this moment in time, do we know that it is safe? That is really the question we need to think about,” Dr Nischal said.

Another study involved 63 eyes of 46 patients who underwent LASIK to treat up to 6 D of hyperopia. At 12 months' follow-up, 70 per cent had an improvement in their best-corrected visual acuity, and amblyopia decreased in 24 eyes, and disappeared completely in 20 eyes with no other treatment (Dvali et al, Journal of Refractive Surgery 2005, 21(5 Suppl):S614-6).

“My one word of warning is that children with behavioural problems rub their eyes a lot. If we’re going to do LASIK we have to be prepared for flap problems,” Dr Nischal said.

The literature concerning correction of high hyperopia in children with phakic IOLs is much more sparse, consisting of only two cases implanted with Artisan/Verisyse IOL. Dr Nischal noted that the greatest concern about the implants is that they might induce a progressive corneal endothelial cell loss.

“We know we have concerns about phakic IOLs because there are only two reputed reported cases, and because there’s endothelial cell loss in the high ametropes maybe the posterior chamber ICL would be a better bet,” he suggested.

Accommodative esotropia

Regarding the use of refractive surgery for accommodative esotropia, there are 15 series of patients treated for PRK, LASIK and phakic IOL implantations. The studies showed that among eyes who got within 10 PD of orthotropia, over 90 per cent were successfully aligned without spectacle correction.

He noted that the complications occurring in the eyes undergoing LASIK included corneal striae in two series, diffuse lamellar keratitis in two series, and permanent corneal opacity in one series, and the need for enhancement procedures in one series. Most, but not all of the complications occurred in the paediatric cases.

“Surgery for high hyperopia should be considered in children who have multiple issues, including, but not limited to, neurodevelopmental and behavioural disorders. Parents and guardians of such patients should be made aware of the phakic IOLs and LASIK and LASEK,” he concluded.