Corneal Biomechanics Using a Scheimpflug-Based Noncontact Device in Normal-Tension Glaucoma and Healthy Controls

To determine if a novel biomechanical parameter, corneal applanation velocity, as measured by the Corvis ST, is associated with a diagnosis of normal-tension glaucoma (NTG).

Prospective, cross-sectional study.

Study and control subjects were recruited from the ophthalmology clinic of a university teaching hospital in Hong Kong over an 8-week period in 2013. A total of 80 eyes with NTG diagnosis and 155 healthy eyes randomly selected to be in the control group were included in the final analysis. All subjects underwent corneal biomechanical testing with the Oculus Corvis ST non-contact tonometer. Logistic regression analysis adjusted for age and central corneal thickness was conducted to assess the relationship between inward and outward applanation velocity and the risk of NTG. Secondary outcome variables included corneal applanation time, length, amplitude, and highest concavity.

Inward applanation velocity was faster in the NTG eyes (0.15 ± 0.02 m/s) than in the control eyes (0.14 ± 0.02 m/s) (P = 0.016). The odds ratio for a 0.01 m/s increase in inward applanation velocity when comparing NTG eyes with control eyes adjusted for age and central corneal thickness was 1.15 (95% confidence interval, 1.03-1.30) (P = 0.016). There was no evidence that outward applanation velocity or any secondary corneal biomechanical variable differed between the NTG and control eyes.

Normal-tension glaucoma eyes demonstrated a small, statistically significant faster corneal inward applanation velocity than normal control eyes.