Amblyopia in children : therapy and follow-up

Abstract

Amblyopia, the leading cause of unilateral visual impairment in children, is caused by inadequate stimulation of the visual system during the sensitive periods of visual development in childhood. Cataract, anisometropia and strabismus are well-known causes of amblyopia.

Bilateral congenital cataract is a common cause of treatable childhood blindness. Early surgery and intense postoperative amblyopia therapy can result in good visual acuity (VA). In the developing world, the possibilities of such postoperative care are limited. Study I was a prospective 2-year follow-up study. We evaluated the refractive and visual outcome after surgery for paediatric cataract in 65 children aged 3 to 15 years. No postoperative correction with spectacles or occlusion was possible due to the socioeconomic environment in the Ukraine. We found a substantial decrease in the immediate high astigmatism that developed postoperatively, and the preoperative VA improved significantly despite the lack of postoperative amblyopic treatment.

The diagnosis and follow-up of amblyopia depend on measuring the bestcorrected visual acuity (BCVA) with optotypes on test charts. However, studies have shown that VA testing using conventional optotypes is insensitive for detecting subtle defects in visual function. Study II evaluated the foveal function in the eyes of 24 children treated for monocular amblyopia and in 25 control children. The children underwent measurement of the BCVA using a standard decimal chart, the TriVA method at different contrast levels and the Rarebit Fovea Test (RFT). The amblyopic eyes had significantly lower results when the BCVA was evaluated with the decimal chart and the TriVA test compared to the fellow eyes and the control eyes. When foveal function was evaluated with the RFT, no significant difference was found between the amblyopic eyes and the fellow eyes, although both the amblyopic eyes and the fellow eyes had significantly lower results compared to the control group. Our results agreed with those of previous studies that also reported abnormalities in the fellow eye of patients with anisometropia and/or strabismus and indicated that the RFT might provide different information about foveal function compared to the other methods.

Occlusion of the better eye has been the mainstay for amblyopia therapy. Patching might cause social stigmata, skin irritation and disruption of binocular function. Good compliance is important but sometimes difficult to achieve. Therefore, it is valuable to adjust the way we use the occlusion therapy and evaluate alternative treatments. In study III we prospectively randomized 80 children (age, 4-5 years) with anisometropic amblyopia to treatment with spectacles in combination with Bangerter filters or to treatment with spectacles alone. The BCVA, binocular function and refractive errors were measured repeatedly during 1 year. We found more rapid VA recovery with Bangerter filters than with spectacles alone. However, the 1-year median BCVA did not differ significantly between the treatments. The study showed an increase in the median spherical equivalent refractive error in the amblyopic eyes and the fellow-eyes. We also found a decrease in the median anisometropia in both groups. Study IV was a randomized prospective trial designed to compare spectacles plus patching 8 hours or more daily, 6 days a week, to spectacles plus patching 8 hours or more on alternate days as treatment for amblyopia in 40 children aged 4 to 5 years. The BCVA, binocular function, and refractive errors were measured repeatedly over the course of 1 year. There was no significant difference in the magnitude of change in the BCVA between the groups, and the BCVA at 1 year improved to a median 0.1 logMAR in both groups. Therefore, alternate-day patching might be a way to adjust occlusion treatment, especially in families in which daily occlusion is problematic.