A left upper lid ptosis and left convergent squint.

In any combination of upper lid ptosis and strabismus, it is important to consider a third cranial nerve paresis. However, here there is a convergent deviation, which is not consistent with a third nerve problem. This child actually has congenital upper lid ptosis and amblyopia in the left eye. The amblyopia has resulted in the unused eye turning inwards. But the ptosis is not severe enough to cover the pupil or visual axis. How can it cause amblyopia ? In fact, many patients with congenital ptosis are at risk of amblyopia, not through occlusion of vision, but through astigmatism. Congenital ptosis has a high association with astigmatism, which through blurring of vision in the affected eye, can lead to amblyopia in childhood.

Lesson : It is important not to think that a child is free of risk of amblyopia from upper lid ptosis just because the ptosis does not impinge on the visual axis. All patients with congenital ptosis must have their refractive status carefully assessed and corrected.