The extraocular muscle defects, neurotoxins, blindness, mechanical defects, unilateral vision obstruction in childhood, various brain disorders or systemic diseases, amblyopia, paralytic shellfish poisoning, botulism, haemangioma near eye, Guillain-Barré syndrome, Apert syndrome, Noonan syndrome, Prader-Willi syndrome, trisomy 18, congenital rubella, incontinentia pigmenti, cerebral palsy, Laurence-Moon-Biedl syndrome, pseudohyperparathyroidism.