Evaluation of Scheimpflug imaging parameters in blepharospasm and normal eyes.

BACKGROUND: To investigate changes in corneal elevation, pachymetry, and keratometry in discriminating between normal and blepharospasm eyes, as measured by the Pentacam rotating Scheimpflug camera.

METHODS: This was a prospective, cross-sectional study. A total of 47 consecutive patients with a range of blepharospasm severity and 40 age- and sex- matched healthy subjects were included, one eye of each subject was randomly chosen for data analysis. Blepharospasm severity was evaluated using the Jankovic scale and categorized as mild, moderate, or severe. Corneal parameters were measured by the Pentacam rotating Scheimpflug camera to derive corneal tomography information. Various parameters regarding keratometry, elevation at the anterior and posterior corneal surface, pachymetric data, final D value, and topometric indices from the Pentacam software were recorded, and the relationship between the blink rate and corneal parameters was analyzed. Intraclass correlation coefficients (ICCs) were assessed to evaluate the repeatability of intraobserver.

RESULTS: Increased topographic asymmetry was observed in moderate and severe blepharospasm. Front K1and front Km were significantly higher in cases of mild (P < 0.05), moderate (P < 0.0001), and severe (P < 0.0001) blepharospasm as compared with controls. Front K2, back K1, back K2, and back Km were significantly higher in cases of moderate (P < 0.01) and severe (P < 0.001) blepharospasm as compared with controls. For corneal topometric indices, both ISV and IVA were significantly increased in severe blepharospasm (P < 0.05). Radii minimum were significantly increased in cases of moderate and severe blepharospasm (P < 0.05).There were no differences in corneal elevation and corneal pharcymetric parameters among the four groups, except for front BFS, which was significantly different in blepharospasm groups (P < 0.05). Final D values were significantly higher in the severe blepharospasm (P < 0.01) group than that among controls. There were significant correlations between the blink rate and most corneal tomographic parameters. All parameters showed high reproducibility (ICC: 0.921-0.996) for normal and blepharospasm subjects.

CONCLUSIONS: Blepharospasm may lead to a redistribution of the pressure applied by the lids over the cornea and, consequently, may result in corneal shape changes, which can be documented through corneal topography.