AUTHOR=Yousefi Atieh , Roberts Cynthia J. , Reilly Matthew A. 

TITLE=The Shape of Corneal Deformation Alters Air Puff–Induced Loading

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2022.848060

DOI=10.3389/fbioe.2022.848060

ISSN=2296-4185

ABSTRACT=<p><bold>Purpose:</bold> To determine the dynamic modification of the load exerted on the eye during air-puff testing by accounting for the deformation of the cornea.</p><p><bold>Methods:</bold> The effect of corneal load alteration with surface shape (<italic>CLASS</italic>) 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 (<italic>t</italic><sub><italic>CD</italic></sub>), maximum <italic>CLASS</italic> value (<italic>CLASS</italic><sub><italic>max</italic></sub>), and the area under <italic>CLASS</italic>-time curve (<italic>CLASS</italic><sub><italic>int</italic></sub>) 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.</p><p><bold>Results:</bold> Accounting for <italic>CLASS</italic> increased the load by 34.6% ± 7.7% at maximum concavity; these differences were greater in KCN subjects (<italic>p</italic> &lt; 0.0001) and lower in OHT subjects (<italic>p</italic> = 0.0028) than in NRL subjects. <italic>t</italic><sub><italic>CD</italic></sub> and <italic>CLASS</italic><sub><italic>int</italic></sub> were significantly longer and larger, respectively, for KCN subjects than those in the NRL and OHT groups (<italic>p</italic> &lt; 0.0001).</p><p><bold>Conclusion:</bold> 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.</p>