Thinnest and central corneal thickness
TCT and CCT are important parameters for preoperative refractive surgery screening. In refractive surgery, based on the Munnerlyn formula [CASIA SS-1000 is 4x (repeatability ratio = 0.22–0.24) more precise than Pentacam when repeating TCT and CCT measurements using the same device, and 5x (repeatability ratio = 0.20) more precise than Pentacam when repeating TCT and CCT measurements using different devices.The mean difference in CCT between CASIA SS-1000 and Pentacam of − 10.45 μm (~ 2% of average CCT for all participants) with LOA ranging 45 μm (− 33.75, 12.85) could be considered clinically significant. This difference may lead ophthalmologists to make a safer (more conservative) decision for refractive surgery. However, it may disqualify some patients who would be qualified if measured by Pentacam. The two measurements can be converted by the following equation: CASIA = 10.87 + 0.97 x Pentacam. For example, an eye measured 500 μm CCT by Pentacam can be converted to CASIA measurement as 490.87 μm. Therefore, decreasing the clinical difference in the values can be obtained. Similarly, TCT measurements can be converted by CASIA = 6.88 + 0.97 Pentacam. However, the decreased variability in measurements obtained with the CASIA SS-1000 results in more consistent clinical decisions.In addition, after reviewing 94 papers published between 2000 and 2014, Rozema et al. reported that of the 14 instruments in which Pentacam was compared, five significantly overestimated CCT in normal eyes [