Treatment of unilateral visual impairment on preschool vision screening

Editor—Clarke et al provide evidence that deferring treatment for amblyopia from age 4 to 5 is not harmful as visual acuity remains the same after treatment.¹ Deferring makes it easier to target the population, mobilise resources, and motivate children to wear glasses and patches. They also recommend that fewer children need patching. Hence, it is an important article that could change current practice.

Figure 1.

The efficacy of patching, however, depends on several variables such as total duration of patching, severity of amblyopia, initial visual acuity, the cause of amblyopia, and compliance.²,³

Although two thirds of the children for whom patching was advised wore patches for a mean of 20 weeks, the paper is not clear about the number of hours advised daily and the compliance. Cleary showed that maximal improvement occurs in response to 400 hours of occlusion wear or less, and to full time occlusion.³ She defines full time occlusion as wearing more than 8 hours a day (8-12 hours prescribed) and part time wear as less than 7 hours (2-6 hours prescribed). Improvement in acuity with six hours of prescribed daily patching is similar to that with prescribed fulltime patching in severe amblyopia.⁴ Shorter times of occlusion (such as 1 hour daily) fail to produce a clinically or statistically significant improvement in vision.⁵

I wonder whether the patching regimen and outcome in children with microtropia was similar to that in those without a squint.