Subclinical Optic Nerve Changes After Le Fort I Osteotomy

Fifty patients aged 18-45 years scheduled for isolated Le Fort I osteotomy or Le Fort I osteotomy combined with bilateral sagittal split osteotomy (BSSO) will be enrolled in this single-center, prospective, observational cohort study. Each patient serves as their own control (within-subject comparison across time points). All participants will undergo ophthalmologic examination, RNFL-OCT imaging, optic disc morphology assessment (disc area, elongation ratio, presence of disc head hemorrhage), and Humphrey 30-2 visual field testing at three time points: preoperatively (T0, within 1 week before surgery), 1 week postoperatively (T1), and 3 months postoperatively (T2). All ophthalmologic measurements will be performed by a single examiner blinded to intraoperative surgical details, using the same device throughout. Maxillary advancement amount and pterygomaxillary junction depth/concavity angle will be measured preoperatively on CBCT (pterygomaxillary junction measured bilaterally, with Observer 1 measuring twice for intraobserver reliability and Observer 2 measuring once for interobserver reliability). No intervention, randomization, or treatment-group allocation occurs as part of this study; all participants receive their routine, already-planned orthognathic surgical care. A priori power analysis (G\*Power, RM ANOVA within-between interaction, f=0.25, epsilon=1, alpha=0.05, power=0.90) indicated a minimum required sample size of N=36; n=50 was set to allow for attrition.

Patients undergoing isolated Le Fort I osteotomy or Le Fort I combined with bilateral sagittal split osteotomy (BSSO). No randomization or treatment allocation; all participants receive their routine, already-planned orthognathic surgical care. Diagnostic Test: RNFL-OCT and optic disc morphology assessment (disc area, elongation ratio, disc head hemorrhage), performed preoperatively (T0) and at 1 week (T1) and 3 months (T2) postoperatively. Diagnostic Test: Humphrey 30-2 visual field testing, performed at the same three time points. Diagnostic Test: Preoperative CBCT measurement of pterygomaxillary junction depth and concavity angle, and maxillary advancement amount from surgical planning data.

Diagnostic Test: RNFL-OCT and Optic Disc Assessment · Diagnostic Test: Diagnostic Test · Diagnostic Test: Preoperative CBCT Measurement of Pterygomaxillary Junction

Peripapillary retinal nerve fiber layer thickness and optic disc morphology (disc area, elongation ratio, presence of disc head hemorrhage) measured by optical coherence tomography, performed preoperatively (T0) and at 1 week (T1) and 3 months (T2) postoperatively.

Humphrey 30-2 Visual Field Testing Açıklama: Standard automated perimetry (Humphrey 30-2 program) performed at the same three time points (T0, T1, T2) to assess mean deviation and pattern standard deviation.

Cone-beam computed tomography measurement of pterygomaxillary junction depth and concavity angle, and maxillary advancement amount from virtual surgical planning data, obtained preoperatively.

Plazo: Baseline (T0, preoperative) to 3 months (T2) postoperatively

Change in peripapillary retinal nerve fiber layer (RNFL) thickness, measured by optical coherence tomography (OCT), from baseline (T0, preoperative) to 1 week (T1) and 3 months (T2) after Le Fort I osteotomy.

Plazo: Baseline (T0) to 3 months (T2) postoperatively

Change in optic disc area and elongation ratio (vertical/horizontal), measured by OCT, from baseline (T0) to 1 week (T1) and 3 months (T2) after Le Fort I osteotomy.

Evaluation of Subclinical Optic Nerve Head Changes After Le Fort I Osteotomy Using Retinal Nerve Fiber Layer Optical Coherence Tomography