The Shape of Corneal Deformation Alters Air Puff-Induced Loading

To determine the dynamic modification of the load exerted on the eye during air-puff testing by accounting for the deformation of the cornea. The effect of corneal load alteration with surface shape ( ) was characterized as an additional component of the load produced during the concave phase where the fluid outflow tangential to the corneal surface creates backward pressure. Concave phase duration ( ), maximum value ( ), and the area under -time curve ( ) are calculated for 26 keratoconic (KCN), 102 normal (NRL), and 29 ocular hypertensive (OHT) subjects. Tukey's HSD tests were performed to compare the three subject groups. A p-value less than 0.05 was considered statistically significant. Accounting for increased the load by 34.6% ± 7.7% at maximum concavity; these differences were greater in KCN subjects ( < 0.0001) and lower in OHT subjects ( = 0.0028) than in NRL subjects. and were significantly longer and larger, respectively, for KCN subjects than those in the NRL and OHT groups ( < 0.0001). Load characterization is an essential step in assessing the cornea's biomechanical response to air-puff-induced deformation. The dynamic changes in the corneal surface shape significantly alter the load experienced by the corneal apex. This implies a subject-specific loading dynamic even if the air puff itself is identical. This is important when comparing the same eye after a surgical procedure or topical medication that alters corneal properties. Stiffer corneas are least sensitive to a change in load, while more compliant corneas show higher sensitivity.