Biomechanical profile of refractive procedures; is there a biomechanical privilege?

Abstract

AbstractThe cornea shows regional in‐plane variation in strain and deformation. Paracentral and peripheral cornea is stiffer than the central cornea due to differing orientation and number of collagen fibrils. Corneal elastic strength is a function of depth, with decreasing strength from the anterior to the posterior stroma.During central myopic ablation, an immediate circumferential severing of corneal lamellae is produced. resulting in a forward herniation. Additionally central ablation also relaxes lamellar tension in residual peripheral lamellar segments, which decreases local resistance to swelling leading to peripheral stromal thickening. Expansion of the peripheral stroma may generate centripetal stress in underlying lamellae through dense interlamellar connections at the margin of the ablation zone, resulting central flattening.Empirically, the hyperopic response is dominant when ablation is limited to the anterior stroma, and progressively deeper circumferential insults result in a shift towards corneal steepening. Central flattening response augments the effects of a myopic procedure but impedes efforts to correct hyperopia.