Normal Tension Glaucoma Results in Softer Corneas

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Researchers determine biomechanical properties inherent in normal- and high-tension glaucoma patients by comparing these properties with normal control individuals and evaluating stiffness and modulus.

Patients with normal-tension glaucoma (NTG) have softer corneas than individuals with high-tension glaucoma (HTG) and healthy individuals, according to research published in the American Journal of Ophthalmology.

Researchers enrolled 334 individuals (mean age, 42.7±16.9 years; 186 men) including patients with NTG (n=108), HTG (n=113), and healthy control individuals (n=113). All participants underwent complete ophthalmic examinations including corneal biomechanical assessment, Scheimpflug imaging, and visual field and retinal nerve fiber layer (RNFL) measurements. Patients with NTG were significantly older (aged 50.4±15.1 years) compared with HTG individuals (aged 41.4±16.2 years) and control individuals (aged 36.5±16.6 years).

Overall, patients in the NTG group had less corneal stiffness (71.0±10.9 Newtons per meter (N/m)) compared with both control individuals (75.6±11.0 N/m; P =.023) and participants with HTG (77.3±15.6 N/m; P =.001). A positive association between central corneal thickness (CCT) and corneal stiffness existed in patients with NTG (P =.028), but not in those with HTG (P =.509)

Mean deformation amplitude (DA) in the NTG group was higher compared with the HTG group, but similar to that of the control group (P =.038 and P =.939, respectively).

Stiffness was associated with CCT in the NTG group and modulus was inversely related to CCT in both groups. (P <.001 for both). DA, DA ratio, and integrated ration (IR) were inversely related to CCT in both groups and stiffness parameterA1 was associated with CCT.

“[T]he corneas of NTG patients are softer than those of HTG patients and normal controls, as determined by [corneal indentation device], which are associated with thinner CCT,” according to the researchers. “These might suggest different ocular biomechanical properties in NTG and HTG. There was no correlation among corneal biomechanics, visual field, and RNFL thickness.”

Study limitations include the heterogeneity in glaucoma therapy, age differences between the groups, and the single center design.


Xu Y, Ye Y, Chen Z, et al. Corneal stiffness and modulus of normal-tension glaucoma in Chinese. Am J Ophthalmol. Published online June 24, 2022. doi:10.1016/j.ajo.2022.06.014