Key parameters assessed by the CST are repeatable. Keratoconus is associated with greater DA than in healthy eyes, even when controlled for CCT and IOP. Deformation amplitude may be a useful adjunct in keratoconus assessment and monitoring, but cannot solely discriminate between healthy and keratoconic corneas.

Citation: Vellara HR, Ali NQ, Gokul A, Turuwhenua J, Patel DV, McGhee CNJ. Quantitative analysis of corneal energy dissipation and corneal and orbital deformation in response to an airpulse in healthy eyes. Invest Ophthalmol Vis Sci. 2015;56:6941-6947. DOI:10.1167/iovs.15-17396 PURPOSE. To examine and evaluate ocular biomechanical metrics and additionally derived corneal and orbital components using a noncontact Scheimpflug-based tonometer (CorVis ST) in a population of healthy eyes. METHODS.A total of 152 eyes of 152 participants were examined by slit-lamp biomicroscopy, corneal tomography, and the CorVis ST (CST). This determined the distribution of outputs from the CST, such as deformation amplitude (DA), and additionally derived parameters, including maximum corneal deformation (MCD), maximum orbital deformation (MOD), and corneal energy dissipation (CED).RESULTS. The mean age of participants was 35.88 6 13.8 years. Deformation amplitude significantly correlated with age (r ¼ 0.24, P ¼ 0.002) but not sex or ethnicity (P > 0.05). Multiple linear regression analysis revealed significant correlations between DA and age (r ¼ 0.19, P ¼ 0.006) and DA and IOP (r ¼ À0.59, P < 0.001). Age correlated with MCD (r ¼ 0.20, P ¼ 0.01), MOD (r ¼ 0.18, P ¼ 0.03), and CED (r ¼ 0.39, P < 0.001). Males had a lower MOD than females (0.24 vs. 0.26 mm, respectively, P ¼ 0.01); however, there were no differences in MCD or CED between sexes (P > 0.05). There were no significant differences between ethnicities for MCD, MOD, and CED (P > 0.05). Multiple linear regression analysis revealed significant correlations between MCD and IOP (r ¼ À0.65, P < 0.001), CED and age (r ¼ 0.41, P < 0.001), CED and IOP (r ¼ 0.28, P ¼ 0.001), and between CED and central corneal thickness (CCT) (r ¼ À0.36, P < 0.001).CONCLUSIONS. The isolation of the corneal component (MCD) should be used when analyzing deformation characteristics in diseases that only affect the cornea. This study establishes a baseline for a population of healthy eyes. Future publications will identify differences in MCD, MOD, and CED between healthy and diseased populations.

No author has a financial or proprietary interest in any material or method mentioned.

Patients with glaucoma and ocular hypotension are satisfied with topical ocular hypotensives. Efforts to improve patient satisfaction should focus on convenience and ease of administration.

Importance Keratoplasty is a surgical procedure to create a more regular optical surface following biomechanical weakening of the cornea in keratoconus. The ideal keratoplasty procedure should also restore corneal biomechanics to that of the healthy cornea. Background This study aimed to evaluate and compare the biomechanical properties of corneas following penetrating keratoplasty (PKP) and predescematic deep anterior lamellar keratoplasty (DALK) to those of healthy eyes. Design Prospective cross‐sectional study. Participants Two cohorts of post‐keratoplasty eyes (42 eyes with PKP and 27 eyes with DALK) with each other, and with a cohort of 152 healthy eyes. Methods All eyes were examined by slit‐lamp biomicroscopy, tomography, anterior segment‐OCT and non‐contact tonometry CorVis ST (CST). Main Outcome Measures CST biomechanical parameters, maximum corneal deformation (MCD) and corneal energy dissipation were compared between keratoplasty techniques, and with healthy eyes. Results The mean age of participants with PKP and DALK were 35 ± 13.7 and 36.1 ± 12.6 years, respectively. None of the CST parameters were significantly different between PKP and DALK eyes. However, when compared to healthy corneas, numerous parameters were significantly different for both keratoplasty techniques. Of note, MCD was significantly higher in PKP compared to DALK and healthy corneas, after controlling for co‐factors. Conclusions and Relevance Neither type of keratoplasty technique utilized in keratoconus completely restored corneal biomechanical properties to that of healthy corneas. However, PKP resulted in a greater number of parameters significantly different to healthy corneas, compared to DALK.