Portal de Periódicos da CAPES

High myopes have lower normalised corneal tangent moduli (less ‘stiff’ corneas) than low myopes

2016; Wiley; Volume: 37; Issue: 1 Linguagem: Inglês

10.1111/opo.12335

1475-1313

Ying Hon, Guozhen Chen, Shu‐Hao Lu, D.C.C. Lam, Andrew Lam,

Ocular Surface and Contact Lens

Abstract Purpose To compare corneal tangent moduli between low and high myopes. Methods Corneal hysteresis ( CH ) and corneal resistance factor ( CRF ) of 32 low and 32 high myopes were obtained using an Ocular Response Analyzer, followed by a corneal indentation device that measured corneal stiffness. Corneal topography, pachymetry, Goldmann applanation tonometry intraocular pressure ( GAT ‐ IOP ), and corneal compensated intraocular pressure ( IOP cc) were also obtained. Corneal tangent modulus was calculated on the basis of corneal stiffness, central corneal thickness and corneal radius. Comparisons between groups and associations between corneal biomechanical and ocular parameters were performed. Results Corneal tangent moduli were positively correlated with GAT ‐ IOP ( R 2 = 0.078, p = 0.025), and IOP cc ( R 2 = 0.12, p = 0.006). Despite similarity in corneal thickness and radius, high myopes exhibited a significantly higher IOP cc (16.4 ± 2.51 mmHg) than low myopes (13.1 ± 1.96 mmHg; t (62) = −5.57, p < 0.0001). Both groups had similar corneal stiffness (0.063 ± 0.0085 and 0.063 ± 0.0079 N mm −1 for low and high myopes, respectively) and CRF (9.6 ± 1.58 and 9.5 ± 1.90 mmHg for low and high myopes, respectively). Moreover, high myopes exhibited a significantly lower CH (9.5 ± 1.51 mmHg) than low myopes (10.6 ± 1.38 mmHg; t (62) = 2.92, p = 0.005). After normalising corneal tangent moduli to the mean intraocular pressure in normal eyes (15.5 mmHg) using IOP cc, high myopes showed a significantly lower corneal tangent moduli (0.47 ± 0.087 MP a) than low myopes (0.57 ± 0.099 MP a; t (62) = 4.17, p < 0.0001). Conclusions High myopes had lower normalised corneal tangent moduli than low myopes, which indicated that their corneas were less stiff. This is the first in vivo study comparing elastic moduli of the cornea in different refractive groups. Further studies are warranted to understand whether a less stiff cornea is a cause for or an outcome from myopia development.