Effect of Age on Pentacam Keratoconus Indices

Purpose. To assess the effect of age on elevation and pachymetric Pentacam keratoconus (KC) detection indices, and the need to adjust normative values accordingly. Methods. In a retrospective study, 95 eyes of myopic normal subjects without KC were evaluated using the OCULUS Pentacam, with an age range of 17.4 to 46.8 years. Subjects were categorised into three groups according to their age: the first included those younger than 21 years (19 eyes), the second was for the age range of 21-40 years (65 eyes), and the third comprised subjects older than 40 years (11 eyes). Results. There were statistically significant differences among the three groups regarding many elevation indices: AE from BFS, PE from BFS, and PE minus AE from BFS (P = 0.003, 0.010, and <0.001, resp.), and pachymetric indices: PPI avg, PPI max, ART avg, ART max, and diagonal decentration of the thinnest point (P = <0.001, 0.024, 0.003, 0.026, and 0.026, resp.). On comparing subjects below 21 years to those above 40 years, there was a statistically significant decrease of both PE from BFS and PE minus AE (P = 0.005 and <0.001, resp.) and statistically significant increase in AE from BFS (P = 0.001). Conclusions. Age is an important determinant of elevation indices, significantly altering their normative values. The use of the more robust pachymetry, rather than elevation, indices is recommended in subjects below 21 or above 40 years of age.