Impact of Myopia on Corneal Biomechanics in Glaucoma and Nonglaucoma Patients

Abstract

PurposeWe evaluated the impact of myopia on corneal biomechanical properties in primary open-angle glaucoma (POAG) and nonglaucoma patients, and the effect of modification of glaucoma on myopic eyes.MethodsThis cross-sectional study included 66 POAG eyes (33 myopia, 33 nonmyopia) and 66 normal eyes (33 myopia, 33 nonmyopia). Seven corneal biomechanical parameters were measured by ultra-high-speed Scheimpflug imaging, including corneal deformation amplitude (CDA), inward/outward corneal applanation length (ICA, OCA), inward/outward corneal velocity (ICV, OCV), radius, and peak distance (PD).ResultsMean age (SD) of the 65 male (49%) and 67 female (51%) patients was 59 (9.82) years. Myopia was associated with significantly higher CDA (adjusted effect = 0.104, P = 0.001) and lower OCV (adjusted effect = −0.105, P < 0.001) in the POAG group. Within the nonglaucoma group, myopic eyes had a significantly lower OCV (adjusted effect = −0.086, P < 0.001) and higher CDA (adjusted effect = 0.079, P = 0.001). All parameters except PD suggested that glaucoma modified the effect of myopia on corneal biomechanics. Percentage differences in the adjusted myopic effect between POAG and nonglaucoma patients was 31.65, 27.27, 31.65, 50.00, 22.09, and 60.49 for CDA, ICA, OCA, ICV, OCV, and radius, respectively.ConclusionsMyopia had a significant impact on corneal biomechanical properties in the POAG and nonglaucoma groups. The differences in corneal biomechanical parameters suggest that myopia is correlated with significantly lower ocular rigidity. POAG may enhance the effects of myopia on most of these parameters.

Age distribution and associated factors of cornea biomechanical parameter stress-strain index in Chinese healthy population

“…Chang’s study pointed out that the axial elongation led to corneal flattening and thickness reduction [ 35 ], suggesting that the increase of axial length may affect the biomechanics of the cornea and previous studies have proved this. Myopia in glaucoma and normal eyes would lead to biomechanical parameters changes such as corneal deformation amplitude (CDA), outward corneal applanation (OCA) and cornea stiffness (CS) [ 36 , 37 ]. Especially the cornea in high myopia had faster outward corneal velocity (OCV) and higher CDA compared to emmetropia [ 16 ].…”

Imaging in myopia: potential biomarkers, current challenges and future developments

“…Although most of the refractive error associated with myopia comes from the axial length, it is increasingly recognised that changes of the anterior segment in high myopia lead to significant optical and higher order aberrations 60. A potentially interesting aspect is the study of biomechanical changes associated with corneal thickness in high myopia, which may affect the evaluation of intraocular pressure61 and diagnosis of glaucoma—elaborated further later in this review 62. However, current studies have variable results due to the different imaging techniques and the technological limitations in measuring on the biomechanical changes of the cornea associated with increasing myopia 63…”

Dynamic Scheimpflug Ocular Biomechanical Parameters in Untreated Primary Open Angle Glaucoma Eyes

“…16,22 For example, most prior studies included glaucoma patients with high baseline 18,19 or relatively high treated IOP. 16,17,22 In a previous study, we demonstrated the greater compliance of glaucoma eyes compared with healthy eyes after controlling for these confounding effects. 23 However, because most previous studies, including ours, enrolled glaucoma patients under medical treatment, the question remains unanswered as to whether biomechanical alterations in glaucoma eyes were caused by glaucoma per se, medications for glaucoma, or both.…”