Three-dimensional anatomy and dynamic changes of the conjunctival fornix assessed by high-resolution magnetic resonance imaging

Abstract Background To characterise the three-dimensional (3D) anatomy and dynamic changes of the conjunctival fornix across different gaze positions using high-resolution magnetic resonance imaging (MRI). Subjects/methods Three eyes of three healthy adult female volunteers without ocular or systemic disease, prior ocular surgery, or ocular surface pathology. A scleral buckling sponge was inserted into the superior and inferior conjunctival fornices to create an implant-induced forniceal space (IFS). High-resolution orbital MRI was performed during primary gaze, upgaze, downgaze and eyelid closure. IFS volume, surface area, fornix depth (FD) and cornea-fornix (C-F) distance were quantified and compared across positions. Results At primary gaze, the superior fornix showed larger IFS volume and surface area than the inferior fornix, though differences were not significant. Both superior and inferior FD and C-F distance varied with gaze. Superior FD was shortest at downgaze and longest at upgaze and eyelid closure, while inferior FD was shortest at primary gaze and longest at eyelid closure. Superior C-F distance was shortest during eyelid closure, whereas inferior C-F distance was longest at primary gaze and shortest at downgaze. Conclusions This first MRI-based 3D quantitative assessment demonstrated gaze-dependent variability of the conjunctival fornix. The fornix should be regarded as a dynamic rather than static structure, with potential implications for ocular surface disease evaluation, surgical planning and the design of fornix-based implants.