To evaluate in normal healthy eyes the intrasubject repeatability of anterior and posterior corneal curvature measurements and other anatomic anterior segment measurements obtained with a new topography system combining Scheimpflug photography and Placido-disk technology.
Vissum Corp., Alicante, Spain.
Evaluation of technology.
All eyes received a comprehensive ophthalmologic examination including anterior segment analysis with the Sirius system. Three consecutive measurements were performed with the device to assess the intrasubject repeatability of the following parameters: anterior and posterior corneal curvature and shape factor, white-to-white (WTW) corneal diameter, central and minimum corneal thickness, and anterior chamber depth (ACD). The within-subject standard deviation (S(w)) and intraclass correlation coefficient (ICC) were calculated.
This study included 117 eyes of 117 subjects (mean age 42 years; range 7 to 80 years). For anterior and posterior corneal curvatures, the S(w) was 0.04 mm or lower and the ICC was higher than 0.990. For shape-factor measurements, the S(w) was below 0.08 in all cases and ICC values ranged between 0.909 and 0.994. Significantly larger S(w) values were found for the anterior and posterior shape factor calculated for 8.0 mm compared with 4.5 mm (P<.01). An S(w) value below 3 μm was observed for the central and minimum thickness, with ICC values close to 1. The mean S(w) for ACD and WTW was below 0.1 mm.
In healthy eyes, the new topography system provided repeatable measurements of several anterior segment parameters, including anterior and posterior curvature and pachymetry.