Biomechanical properties of the cornea in floppy eyelid syndrome

Background: Floppy eyelid syndrome (FES) is a frequently underdiagnosed disorder of unknown pathogenesis. FES has been associated with ocular conditions such as keratoconus. At present, despite the frequent combination of FES and keratoconus, there are almost no data on the biomechanical properties of the cornea in these patients. Aims: to determine the cornea’s biomechanical properties in patients with floppy eyelid syndrome. Methods: The study included 40 patients (54 eyes) with hyper-extensible eyelid syndrome. The average age was 53.9±6.7 years. The central corneal thickness averaged 551±25 µm. All the patients underwent a standard ophthalmological examination, including pneumotonometry. The intraocular pressure (IOP) and biomechanical properties of the cornea were measured using dynamic bidirectional applanation. Results: The study of the cornea’s biomechanical properties in patients with floppy eyelid syndrome showed a decrease in the corneal hysteresis (CH) indices to 9.96±0.61 mm Hg on the average, in the corneal resistance factor (CRF) - to 9.54±0.64 mm Hg. Moreover, their value varied depending on the severity of the syndrome. The mean value of the corneal compensated IOP (IOPcc) in the entire sample was 15.5±1.0 mm Hg, Goldman IOP (IOPg) - 15.1±2.0 mm Hg, pneumotonometric IOP - 11.61±2.9 mm Hg. Regardless of the severity, the pneumotonometric IOP indices did not have statistically significant differences, while as this syndrome progressed, the IOPcc and IOPg indices showed a steady decrease in the mean values. Conclusions: It was found that, in floppy eyelid syndrome, the biomechanical parameters of the cornea were reduced. At the same time, the value of these indicators varied significantly with the severity. The largest and the smallest decrease were observed in the corneal hysteresis index and the corneal-compensated IOP, respectively.