Introduction: Marcus Gunn syndrome is a rare phenomenon with very less number of cases reported in literature. It may be congenital or acquired. Aim: The aim of this case report was to report the clinical characteristics of Marcus Gunn patient from our Clinic. Case report: A comprehensive opthalmologic examination, CDVA (corrected distance visual acuity), fundus examination and photography, was conducted in Marcus Gunn patient. Clinical findings of patient presented as - chin positioned slightly upwards, extraocular motility normal on both eyes, cover test with normal findings, pupillary examination normal on both eyes. Left upper eyelid was in a lower position than the right one. On right eye, rima interpalpebrarum was 9 mm with upgaze of 13mm. On the left eye, rima interpalpebrarum was 5 mm with upgaze of 6 mm, and with open mouth, left rima interpalpebrarum was 10 mm. Visual acuity on both eyes was 1.0. Cycloplegic refraction on both eyes was +0,75 diopters (D), and Lang test was normal. In the differential diagnosis of patients with ptosis, Marcus Gunn jaw winking syndrome should be considered especially if it improves during feeding, sucking, chewing, smiling or any kind of mouth movement. In case of ptosis always do the jaw test. Have the infant bottle-feed. An older child can chew gum. Have the patient open the mouth, move the jaw from side to side, or protrude the jaw forward. Conclusion: Address first to treatment of any amblyopia if present - eyeglasses, patching etc., or strabismus. Think twice before deciding to operate.
Marcus Gunn, ptosis, jaw winking.