Descriptive Anterior Assessment of the Palpebral Fissure

Description

Framed in an anterior facial view, the palpebral fissure is defined by the free margin of the superior eyelid (with its lid crease and lash line) superiorly and the inferior eyelid margin inferiorly, forming an elliptical aperture over the exposed bulbar conjunctiva and anterior sclera. Medially, the fissure tapers toward the medial canthus, where the lacrimal caruncle and plica semilunaris typically sit just lateral to the lacrimal lake. Laterally, the margins converge at the lateral canthus, where the upper and lower lids meet at a sharper commissure. The upper lid overlaps more of the corneal dome than the lower lid in primary gaze. Accurate appraisal of palpebral fissure height and canthal position underpins routine oculoplastic and neuro-ophthalmic assessment. Small differences matter. Ptosis from levator palpebrae superioris dysfunction or Horner syndrome narrows the fissure, while thyroid eye disease, facial nerve palsy, or cicatricial ectropion can widen it and expose the inferior cornea, predisposing to exposure keratopathy. The medial and lateral canthi also serve as dependable surface landmarks when planning blepharoplasty incisions, canthotomy, or canthopexy, and when documenting traumatic lid lacerations. Ideal for ophthalmology and head and neck anatomy teaching where surface anatomy must be tied to function, this illustration also supports clinical documentation templates, patient-facing surgical consent materials, and textbook figures on eyelid position, ptosis grading, and canthal anatomy. Anatomical accuracy verified by SciePro's Medical Advisory Board.