This Is How to Measure True Corneal Shape Change

A method to analyze corneal shape change allowed clinicians to determine cut-off values and thus detect true shape change, according to an analysis involving 60 individuals. 

Participants included patients with keratoconus (n=30) and healthy controls (n=30). The method involved precision analysis to distinguish between true corneal change from that which was measured imprecisely. Among the results: 

• Correlation between measurements from the same eye was small. 
• The 99.73% limits of agreement (LOA) of the mean of 3 measurements was more precise than the 95% LOA (2 standard deviations) of single cut-off values.

The authors concluded that the average of 3 repeated measurements provide superior precision when there is little correlation otherwise. 

Brunner M, Czanner G, Vinciguerra R, et al. Improving precision for detecting change in the shape of the cornea in patients with keratoconus. Sci Rep. 2018;8(1):12345. doi: 10.1038/s41598-018-30173-7.