Comparison among Ocular Response Analyzer,Corvis ST and Goldmann applanation tonometry in healthy children

AIM： To explore the relationship between different parameters of Ocular Response Analyzer（ORA） and Corvis ST（CST） in a sample of healthy Iranian school-aged children and the relationship between parameters of these 2 instruments against intraocular pressure（IOP）, measured by the Goldmann applanation tonometer（GAT-IOP）, age and gender, and find possible correlation between ORA and CST with GAT.METHODS： This cross-sectional study included 90 healthy children. A general interview and complete eye examination were performed. Following successful GATIOP measurement, ORA and CST were conducted. The CST parameters were A 1/2 length（A1 L, A2 L）, A 1/2 velocity（A1 V, A2 V）, highest concavity deformation amplitude（HCDA）, radius of curvature（Ro C）, peak distance（PD）, central corneal thickness（CCT） and IOP. The ORA parameters were corneal hysteresis（CH）, corneal resistance factor（CRF）, Goldmann-correlated IOP（IOP-G） and corneal compensated IOP（IOP-CC）. Extracted data was analyzed using the Statistical Package for Social Science software.RESULTS： Totally 39 males with age of 9.08±1.60（6-12）y and 51 females with age of 8.96±1.55（6-13）y were included. Many CST parameters were significantly correlated with CH, CRF, IOP-G and IOP-CC. Some CST parameters had a significant correlation with GAT-IOP, including IOP-CST in both eyes and HCDA, A2 L, PD, and RoC in the left eye, but none with age, except A2 L in the right eye. The CRF measurement showed a significant correlation with GAT-IOP in both eyes and CH in the right eye, yet, none with age. Among all CST and ORA parameters, CCT-CST in both eyes and A1 L in right eye had a significant correlation with gender, although this was a negligible negative correlation. Comparison of mean IOP values by different devices showed a significantly highest IOP overestimation by CST and lowest by IOP-CC compared with GAT. Also, IOP-G versus IOP-CST significantly had the lowest IOP overestimation among others. Overall, either low positive correlation or negligible correlation was found between IOP measurements by 3 instruments.CONCLUSION： The study finds the highest IOP overestimation by CST and lowest by IOP-CC compared with GAT. Overall, either low positive correlation or negligible correlation is found between IOP measurements by the 3 instruments.

Corneal biomechanical data and biometric parameters measured with Scheimpflug-based devices on normal corneas

AIM： To analyze the correlations between ocular biomechanical and biometric data of the eye,measured by Scheimpflug-based devices on healthy subjects.METHODS： Three consecutive measurements were carried out using the corneal visualization Scheimpflug technology（Cor Vis ST） device on healthy eyes and the 10 device-specific parameters were recorded.Pentacam HR-derived parameters（corneal curvature radii on the anterior and posterior surfaces;apical pachymetry;corneal volume;corneal aberration data;depth,volume and angle of the anterior chamber） and axial length（AL） from IOLMaster were correlated with the 10 specific CorV is ST parameters.RESULTS： Measurements were conducted in 43 eyes of 43 volunteers（age 61.24±15.72y）.The 10 specific Cor Vis ST data showed significant relationships with corneal curvature radii both on the anterior and posterior surface,pachymetric data,root mean square（RMS） data of lower-order aberrations,and posterior RMS of higher-order aberrations and spherical aberration of the posterior cornea.Anterior chamber depth showed a significant relationship,but there were no significant correlations between corneal volume,anterior chamber volume,mean chamber angle or AL and the 10 specific CorV is ST parameters.CONCLUSION： Cor Vis ST-generated parameters are influenced by corneal curvature radii,some corneal RMS data,but corneal volume,anterior chamber volume,chamber angle and AL have no correlation with the biomechan-ical parameters.The parameters measured by CorV is ST seem to refer mostly to corneal properties of the eye.