Correlation of Biomechanical Features of Keratoconus Patients with Severity of Disease

Background and Objective: Keratoconus is a disorder in cornea characterized by constant thinning and prominence that can result in vision defect. Due to ultrasonic changes in the corneal structure caused by keratoconus disease, its rigidity and biomechanical properties are subject to some changes. In this regard, the present study was conducted to determine the correlation of biomechanical features of keratoconus patients with the severity of the disease. Materials and Methods: The case group was selected from the patients with keratoconus who referred to the Corneal Clinic of Nikookari Hospital in Tabriz and the controls had no eye diseases. Corneal biomechanics, corneal hysteresis, and corneal resistance factor were evaluated in all the samples using an ocular response analyzer device. Results: The present study was carried out on 213 keratoconus eyes and 179 normal eyes. The mean scores of corneal hysteresis were obtained at 13.49±1.34 and 7.67±1.01 mmHg for normal and keratoconus eyes, respectively, which were significantly different between the two groups. The differences between the corneal hysteresis of mild (8.86 mm Hg), moderate (8.30 mm Hg), and severe (7.10 mm Hg) keratoconus eyes were also significant. The mean scores of the corneal resistance factor were reported as 12.68±1.15 and 7.36±1.07 mmHg for normal and keratoconus eyes, respectively, which were significantly different between the two groups. The differences between the corneal resistance factor of mild (8.55 mm Hg), moderate (8.05 mm Hg), and severe (6.76 mm Hg) keratoconus eyes were also significant. Conclusion: The obtained results of the present study showed that corneal hysteresis and corneal resistance factor were lower in keratoconus eyes, compared to those in normal eyes and decreased with the severity of the disease.