Biomechanical Effects of Deep Anterior Lamellar Keratoplasty and Penetrating Keratoplasty for Keratoconus: A Finite Element Analysis

Abstract

Purpose To theoretically compare corneal displacement and the von Mises (VM) stress distribution of deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) for keratoconus (KC) and to evaluate the effects of residual stromal thickness (RST) and intraocular pressure (IOP) on postoperative corneal biomechanics. Methods We performed DALK and PK simulations using Ansys by employing anisotropic nonlinear hyperelastic corneal material properties. We analyzed corneal displacement and VM stress in DALK and PK models under IOPs of 10, 15, 20, and 25 mmHg. We established two DALK models: The ideal-type DALK ensured that postoperative central corneal thickness was constant at 560 µm and the corneal graft thickness varied with RST. The clinical-type DALK ensured that corneal grafts had the same thickness (500 µm) regardless of RST. Then we analyzed the effects of RST and IOP on postoperative corneal displacement and VM stress. Results Corneal displacement and VM stress were lower in the DALK than in the PK model. In the ideal-type DALK model, an increase in RST was associated with increased deformation and decreased VM stress in the healing zone, except for a RST of 0 µm. In the clinical-type DALK model, deformation and VM stress in the healing zone decreased with an increase in RST, except for a RST of 0 µm. Conclusions DALK showed more stability than PK. For the ideal-type DALK model, an increase in RST resulted in decreased postoperative corneal biomechanics in the healing zone. For the clinical-type DALK model, corneal deformation and VM stress decreased with an increase in RST, which provides numerical evidence for the design of corneal transplantation for patients with KC. Translational Relevance In this computational modeling study, we first theoretically compared corneal biomechanics between DALK and PK for KC. Then, the effects of RST and IOP on postoperative corneal biomechanics were investigated. Our findings provide novel insights into the optimal design for corneal transplantation for patients with KC.

Intrastromal Corneal Ring Segments Implantation After Deep Anterior Lamellar Keratoplasty for Astigmatism Correction: Mid-term and Long-term Follow-up

“…In our opinion, the outcomes of this procedure, for visual acuity improvement and astigmatism correction, should be analyzed separately for each keratoplasty technique because the ICRS effect depends on the biomechanical properties of the cornea, and these properties are different in post-DALK and post-PKP eyes. 33,34 However, it is valuable to analyze the ICRS-related complications to evaluate the safety of ICRS implantation in the cornea posttransplant. In total, these previous studies included 157 eyes (37 post-DALK and 120 post-PKP).…”

Fourier-Domain Optical Coherence Tomographic Assessment of Changes in the Schlemm’s Canal of Nonglaucomatous Subjects After Keratoplasty

“…Interestingly, morphological changes in SC were observed only on the temporal side in PK group and only on the nasal side in DALK group. Larger size of SC on the nasal side ( Kagemann et al, 2010 ), different residual stromal thickness in PK and DALK procedures, and negative correlations between corneal deformation and residual stromal thickness ( Li et al, 2021 ) may cause this phenomenon in some unknown and complicated ways that need further exploration.…”

Indications for keratoplasty in management of corneal ectasia

“…Multiple surgical techniques are frequently combined to achieve the best visual outcome. However, surgery may not eliminate the need for contact lens use [15 ▪ ]. The different types of corneal surgeries for ectasia management are reviewed in the following sections.…”