Repeatability and agreement between a reference Scheimpflug tomographer and a low-cost Scheimpflug system.

PURPOSE: To assess the repeatability and agreement between Scheimpflug-based corneal topographers, Scansys and Pentacam, in measuring ocular parameters in myopic eyes. SETTING: Grade-A tertiary hospital in Beijing, China. DESIGN: Cross-sectional study. METHODS: The following measurements were performed in 204 subjects undergoing preoperative examinations for refractive surgery from the corneal curvature, astigmatism, corneal thickness, corneal volume, corneal asphericity, anterior chamber depth (ACD) and volume (ACV), and pupil diameters. Repeatability was determined using intraclass correlation coefficient with 95% CI, Cronbach α, coefficient of variation, within-subject SD, test-retest repeatability, and 1-way analysis of variance (1-way analysis of variance). The interdevice agreement was determined using paired t test and Bland-Altman plots. RESULTS: Scansys showed good repeatability in the anterior and posterior corneal flattest meridian (Kf), steepest meridian (Ks), and mean (Km); axis of anterior corneal Ks; anterior corneal astigmatism; pupil central corneal thickness (CCT); CCT; corneal apex thickness; thinnest corneal thickness; corneal volume; photopic pupil diameter; ACD; and ACV. In the agreement study, Bland-Altman plots showed that 95% limit of agreement of corneal curvature, pupil CCT, corneal apex thickness, thinnest corneal thickness, and corneal volume generated by Scansys and Pentacam were narrow. There were no statistically significant differences in the anterior corneal Kf and Km. CONCLUSIONS: Scansys showed good repeatability in measuring corneal curvature of anterior and posterior surfaces, anterior corneal astigmatism, corneal thickness, corneal volume, photopic pupil diameter, ACV, and ACD. Scansys and Pentacam can only be used interchangeably in measuring anterior corneal curvature.

Long-Term Outcomes After Small-Bone-Window Posterior Fossa Decompression and Duraplasty in Adults with Chiari Malformation Type I.

BACKGROUND: Small-bone-window posterior fossa decompression with duraplasty is one of the popular surgical options for Chiari malformation type I, but its efficacy is controversial and the risk factors of clinical outcome remain unclear. METHODS: The study cohort included 152 patients with Chiari malformation type I who received small-bone-window posterior fossa decompression at Beijing Tiantan hospital from January 2008 to September 2009. All patients underwent combined surgical procedures: a small-bone-window suboccipital decompression (diameter, 2.5-3 cm) and a C1 laminectomy (1.5- to 2-cm wide) followed by a duraplasty with an autologous graft. Clinical manifestations, radiologic features, and follow-up data during a 6-year span were analyzed. Risk factors associated with outcome were investigated by the use of χ(2) analysis and logistic regression analysis. RESULTS: The average follow-up duration was 74 months. Symptoms were improved in 126 patients (82.9%), remained stable in 21 patients (13.8%), and deteriorated in 5 patients (3.3%). There was no mortality. Postoperative magnetic resonance imaging scans were available for all patients. Preoperatively, 112 patients were associated with syringomyelia, and the follow-up magnetic resonance images showed obvious reduction of syringomyelia in 73 patients (65.2%) and no significant change in 39 patients (34.8%). In addition, enlargement of the cistern magna was observed in 92 patients (85.2%). Regression analysis indicates preoperative motor dysfunction, brainstem herniation and basilar invagination may influence the clinical outcome (P < 0.05). CONCLUSIONS: Small-bone-window posterior fossa decompression with duraplasty is an effective and safe treatment option with a low complication rate. Motor dysfunction, brainstem herniation, and basilar invagination are predictors of poor clinical prognosis.