Corneal Hysteresis as a Biomarker for Screening and Diagnosis of Normal Tension Glaucoma

Author(s): Abir Bin Sajj, Tohura Sharmin, Omar Faroque, Siddiqur Rahman, Masudul Hasan, Muhammad Moniruzzaman, Tajmilur Rahman.

Background: NTG stands as a subtype of glaucoma, which results in optic nerve damage with visual field loss when IOP remains within the normal range. The traditional IOP measurement technique causes NTG diagnosis to be delayed. Glaucoma risk assessment and progression evaluation now rely on corneal hysteresis as a measurement for understanding corneal biomechanics. Objective: The study aims to explore corneal hysteresis as a diagnostic tool in NTG diagnosis at the same time examining its relationship to RNFL measures. Methodology: This analytical cross-sectional research involved 100 participants, including 50 patients who had received an NTG diagnosis and 50 healthy subjects matched for age and gender. A complete eye examination, including a procedure for IOP measurement by Goldmann applanation tonometry and CH evaluation through Ocular Response Analyzer (ORA) testing and assessment of central corneal thickness (CCT) with pachymetry and RNFL thickness assessment with optical coherence tomography (OCT), was performed on 100 participants. SPSS conducted the statistical evaluation utilizing p<0.05 as the significance threshold. Result: NTG patient CH levels averaged 9.2 ± 0.6 mmHg, which showed a significant difference compared to control values at 9.5 ± 0.8 mmHg (p=0.036). The average RNFL thickness was considerably thinner in NTG eyes (77.3 ± 8.6 μm) than in control eyes (96.8 ± 7.2 μm) based on statistical assessment (p=0.001). Reduction of CCT measured at 512.9 ± 23.7 μm occurred in subjects with NTG and produced statistically significant results when compared with controls (521.6 ± 19.8 μm, p=0.049). Research results identified a statistically significant relationship between decreased CH and RNFL thinning in patients suffering from NTG (Pearson correlation, p = 0.002), indicating optic nerve structure damage based on reduced CH levels. Conclusion: The clinical value of corneal hysteresis emerges from its ability to predict progression of retinal nerve fiber layer thickness deterioration in NTG patients as the study shows lower corneal hysteresis in NTG patients is associated with increased retinal nerve fiber layer thinning, making it a possible additional tool for screening NTG patients and to support risk assessment through non-invasive testing