Congenital ptosis is a rare condition characterized by an abnormal drooping of the upper eyelid that is present since birth or occurs within the first year of life, resulting in the reduction of the vertical palpebral fissure. Although isolated congenital ptosis can have an autosomal, either dominant or recessive, inheritance, it may be part of a larger spectrum of birth defects combined with other ocular or systemic conditions. It usually presents with a variable loosening of the upper eyelids due to a loss of muscular or nerve function that can be unilateral or bilateral.
The superior branch of the third cranial nerve (CN III) is involved in the contraction of the levator palpebrae superioris muscle and the superior rectus muscle that are responsible for the elevation of the eyelids. The impairment of this function leads to abnormal visual development, resulting in a long-lasting uncorrected astigmatism or deprivational amblyopia. This form of amblyopia is defined as a disruption in the normal image-forming ability of the eye early in life caused by diminished performance of the visual system and severe reduction of the visual acuity due to an obscured visual field.4 The incidence of amblyopia in the overall population has been assessed at ~3%. However, a recent paper published by Willshaw5 provides information of an overall rate of amblyopia of up to 26.45% in a group of pediatric patients with blepharoptosis of different etiologies. Among them, 18.7% have visually significant refractive errors, while 14.19% are present with squint.