Abstract
BackgroundWe evaluated the relationships between corneal biomechanical properties and structural parameters in patients with newly diagnosed, untreated normal-tension glaucoma (NTG).MethodsAll subjects were evaluated using an Ocular Response Analyzer (ORA) measuring corneal hysteresis (CH) and the corneal resistance factor (CRF). Central corneal thickness (CCT), Goldmann applanation tonometric (GAT) data, axial length, and the spherical equivalent (SE), were also measured. Confocal scanning laser ophthalmoscopy was performed with the aid of a Heidelberg retina tomograph (HRT III). We sought correlations between HRT parameters and different variables including CCT, CH, and the CRF. Multiple linear regression analysis was performed to identify significant associations between corneal biomechanical properties and optic nerve head parameters.ResultsWe enrolled 95 eyes of 95 NTG patients and 93 eyes of 93 normal subjects. CH and the CRF were significantly lower in more advanced glaucomatous eyes (P = 0.001, P = 0.008, respectively). The rim area, rim volume, linear cup-to-disc ratio (LCDR), and mean retinal nerve fiber layer (RNFL) thickness were significantly worse in more advanced glaucomatous eyes (P < 0.001, P < 0.001, P < 0.001, and P = 0.001). CH was directly associated with rim area, rim volume, and mean RNFL thickness (P = 0.012, P = 0.028, and P = 0.043) and inversely associated with LCDR (P = 0.015), after adjusting for age, axial length, CCT, disc area, GAT data, and SE. However, in normal subjects, there were no significant associations between corneal biomechanical properties and HRT parameters.ConclusionsA lower CH is significantly associated with a smaller rim area and volume, a thinner RNFL, and a larger LCDR, independent of disc size, corneal thickness, intraocular pressure, and age.
Highlights
We evaluated the relationships between corneal biomechanical properties and structural parameters in patients with newly diagnosed, untreated normal-tension glaucoma (NTG)
There were no significant differences in axial length, Goldmann applanation tonometric (GAT), Central corneal thickness (CCT), spherical equivalent, Goldmann-correlated intraocular pressure (IOPg), or Corneal-compensated intraocular pressure (IOPcc) between patients with NTG and normal controls, while corneal hysteresis (CH) and the corneal resistance factor (CRF) were significantly lower in eyes with more advanced glaucoma (P = 0.001 and P = 0.008, respectively)
CH was positively correlated with rim area and rim volume, and negatively correlated with linear cup-to-disc ratio in NTG patients (P = 0.001, P = 0.007, and P = 0.013, respectively) (Fig. 1)
Summary
We evaluated the relationships between corneal biomechanical properties and structural parameters in patients with newly diagnosed, untreated normal-tension glaucoma (NTG). Burgoyne suggested that the central pathophysiology of glaucoma is damage to RGC axons within the lamina cribrosa of the optic nerve head [2]. It has been suggested that CH may be related to the biomechanical characteristics of the lamina cribrosa and peripapillary sclera that could affect the susceptibility of the optic nerve head to glaucomatous damage [5, 8, 17]. Khawaja et al reported that a larger cup-to-disc ratio was associated with lower CH [15]; only those with high-tension POAG were included in their study, and the association between structural biomarkers and corneal biomechanical properties in normal-tension glaucoma (NTG) eyes were not assessed [15, 18]
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