Purpose: To assess the dynamic features of the medial rectus capsulopalpebral fascia (mrCPF) and the lateral rectus CPF (lrCPF) during horizontal eye movements using cine mode magnetic resonance imaging (MRI). Design: Observational case series. Participants: Ten patients (9 males and 1 female; age range, 8-75 years; mean age, 41.1 years) diagnosed with a unilateral orbital blowout fracture (medial wall, floor, or both) and having a normal contralateral orbit. Methods: Cine mode MRI was used to examine the role of the mrCPF and the lrCPF in relation to the eyelid and horizontal recti muscles during horizontal eye movements. Main Outcome Measures: To assess the dynamic features of the mrCPF and the lrCPF. Results: In medial gaze, the medial part of the eyelid moves posteromedially, in synchronicity with medial rectus muscle contraction, mediated by the mrCPF. The lateral part of the eyelid moves anteromedially, in synchronicity with lateral rectus muscle relaxation, mediated by the lrCPF. In lateral gaze, the lateral part of the eyelid moves posterolaterally, in synchronicity with the lateral rectus muscle contraction, mediated by the lrCPF. The medial part of the eyelid moves anterolaterally, in synchronicity with medial rectus muscle relaxation, mediated by the mrCPF. These findings were demonstrated in all 10 patients. Conclusions: Cine mode MRI was used to demonstrate the dynamic roles of the mrCPF and the lrCPF in mediating eyelid position with the corresponding horizontal recti muscles. This study may allow a better understanding of the importance of these anatomic structures and may reduce functional and cosmetic complications during common oculoplastic and strabismus surgeries. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article.