Glaucoma, Ocular Hypertension Affect Corneal Biomechanics Differently

Compared with healthy controls, the corneas of eyes with high-tension glaucoma (HTG) or ocular hypertension (OHT) are stiffer, whereas the corneas of eyes with normal tension glaucoma (NTG) are more deformed, according to findings of a meta-analysis published in the Journal of Glaucoma.

Investigators from Medical College of Soochow University in China searched publication databases through June 2022 for studies of corneal biomechanics in the setting of glaucoma. A total of 31 studies were included in this analysis.

In the setting of POAG, patients had significantly different corneal resistance factor (weighted mean difference [WMD], -0.736; 95% CI, -1.131 to -0.341; I², 82.6%; P =.000), corneal hysteresis (WMD, -1.094; 95% CI, -1.375 to -0.813; I², 81.3%; P =.000), and highest concavity time (WMD, -0.109; 95% CI, -0.195 to -0.023; I², 47.8%; P =.040) compared with healthy controls.

Among patients with POAG, those with NTG differed by corneal hysteresis, corneal resistance factor, time to reach first applanation, highest concavity time, and peak distance at the highest concavity (all P ≤.022) whereas those with HTG differed by corneal hysteresis, time to reach first applanation, length the corneal vertex moved at the second applanation, and deformation amplitude at the highest concavity (all P ≤.022) compared with controls.

Patients with OHT exhibited significantly different corneal hysteresis (WMD, -0.616; 95% CI, -0.922 to -0.31; I², 0.0%; P =.000), time to reach first applanation (WMD, -0.456; 95% CI, -0.87 to -0.043; I², 90.4%; P =.030), radius of the curvature at the highest concavity (WMD, -0.349; 95% CI, -0.681 to -0.018; I², 0.0%; P =.039), highest concavity time (WMD, -0.182; 95% CI, -0.357 to -0.007; I², 27.7%; P =.041), deformation amplitude at the highest concavity (WMD, -0.090; 95% CI, -0.167 to -0.013; I², 86.0%; P =.022), length the corneal vertex moves at the first applanation (WMD, 0.366; 95% CI, 0.029-0.704; I², 90.1%; P =.033), corneal resistance factor (WMD, 1.323; 95% CI, 0.736-1.928; I², 67.9%; P =.000), and stiffness parameter at the first applanation (WMD, 13.334; 95% CI, 8.574-18.095; I², 47.2%; P =0.000) compared with controls.

In a sensitivity analysis which removed one study at a time, time to reach first applanation and length the corneal vertex moves at the second applanation became significantly different from controls in eyes with POAG. All other findings were similar.

This analysis was limited by the high heterogeneity observed in comparisons. The study authors noted that corneal biomechanics can be affected by age, central corneal thickness, and medications which may have contributed to the heterogeneity observed.

“Our study showed that NTG patients have more deformable corneas, while HTG and OHT patients have stiffer corneas, indicating that corneal biomechanical measurements could benefit clinical diagnosis,” the researchers explain.