AMBLYOPIA

The large, prospective multicentre trials conducted by the Paediatric Eye Disease Investigator Group (PEDIG) have changed his practices for managing amblyopia secondary to anisometropia, strabismus or both, in patients ages three to 17 years, Jonathan Holmes MD, told a session of the 2nd World Congress of Paediatric Ophthalmology and Strabismus. Dr Holmes said that prior to the PEDIG studies he would initiate treatment with spectacle correction based on the cycloplegic refraction plus patching of the sound eye for six hours/day.

“Now I begin treatment with spectacles alone, even when there is strabismus and even in older children, based on PEDIG observational studies showing that amblyopia resolved completely in at least 25 per cent of cases using spectacles alone,†said Dr Holmes, Joseph E and Rose Marie Green Professor of Visual Sciences, Mayo Clinic, Rochester, MN, US.

If spectacles alone are insufficient, options for achieving further visual acuity (VA) improvement include patching the sound eye, atropine to the sound eye or fogging the sound eye with a Bangerter filter. For patching, Dr Holmes said he initially prescribes just two hours a day, even for severe anisometropic/strabismic amblyopia. Use of this low-dose regimen is based on results of randomised clinical trials comparing different patching regimens in children ages three to less than seven. In a trial enrolling patients with severe amblyopia, children were randomised to patching prescribed full-time or six hours/day. A moderate amblyopia trial compared patching prescribed six versus two hours/day.

In each study, the two patching regimens resulted in similar mean VA improvement. In a follow-up randomised clinical trial of two hours of daily patching with or without near activities, some cases of severe anisometropic or strabismic amblyopia also improved with the low-dose twohour- a-day regimen. Another randomised study by Stewart et al, in England, also reported similar outcomes for patching six versus 12 hours/ day. “Using an occlusion dose monitor to determine compliance, Stewart et al found patching time averaged six hours for those in the 12-hour group and four hours in the six-hour group, which may partly explain the similar mean visual acuity improvements with the different regimens,†Dr Holmes said.

However, he added that a review of individual outcomes in the Stewart study showed some patients achieved complete resolution of amblyopia when patched for just one or two hours/day and others had little improvement despite actually patching for more than 10 hours/day. “Currently we do not have enough data to determine potential predictive factors for a child being an extremely poor responder or a super-responder. The inability to identify these children prior to starting patching remains a challenge for clinicians,†Dr Holmes said. He added, “If VA improvement plateaus with two hours of patching, treatment can be switched or the patching time can be increased. Patching two hours a day is very reasonable for starting treatment, but will not be enough for everybody.†The efficacy of atropine one per cent for treatment of amblyopia was demonstrated first in a PEDIG study of moderate amblyopes randomised to atropine one drop every morning or part-time occlusion at least six hours a day.

A follow-up PEDIG study in moderate amblyopes showed outcomes were similar using atropine on weekend mornings only, compared with daily use. A third study compared weekend atropine alone or with a plano lens. The addition of the plano lens (increasing the blurring effect of the atropine) as initial treatment for amblyopia did not enhance mean VA improvement over weekend atropine alone, but it increased by fourfold the percentage of children temporarily losing VA in the sound eye. “Clinicians using a plano lens to enhance the atropine effect need to follow children carefully for reverse amblyopia. VA usually returns to baseline after treatment stops, but some children may require treatment for reverse amblyopia,†Dr Holmes said.

He added that findings from the latter study, which included 60 children with severe amblyopia, support weekend only atropine as a reasonable option even for severe amblyopia. Results of a trial enrolling children ages seven to 17 years led Dr Holmes to offer treatment for amblyopia to older children, especially those seven to 12 years of age. In this PEDIG study, children were randomised to optical correction only or augmented with patching (two to six hours/day) plus near activities.

Children in the augmented treatment arm aged <13 years also received atropine. Among children ages 13 to 17, responder rates were similar in the augmented regimen and optical treatment alone groups. However, the responder rate was more than doubled by augmented treatment in children ages seven to 12. When the children in each age group were further divided based on history of previous treatment for amblyopia, there was a benefit of the augmented regimen among treatment-naive older children (≥13 years).

In the younger subgroup (<13 years), there was a significant benefit of augmented treatment (patching plus atropine) regardless of prior treatment history, but the proportion of responders to augmented treatment was much higher in the treatmentnaive subgroup. “The individual data from this study also highlight significant individual variability in response and identified some children ages 14 to 15 who had a marked improvement in VA,†Dr Holmes observed. “Unfortunately, as clinicians, we can’t yet predict who will be a super-responder, and so it is very reasonable to offer treatment of patching two hours/day to even teenagers with amblyopia, after a trial of spectacles, particularly if they have never had a previous trial of treatment,†he said.