Penetrating keratoplasty versus deep anterior lamellar keratoplasty: which technique establishes healthy corneal biomechanics?

Abstract

Purpose : The cornea is biomechanically compromised in keratoconus. Ideal management options would restore the corneal biomechanics to that of a healthy cornea. This study analysed the corneal biomechanical properties of keratoconic corneas which had undergone either a penetrating keratoplasty (PKP) or a deep anterior lamellar keratoplasty (DALK) and compared them to those of healthy control corneas

Methods : All eyes were examined by slit-lamp biomicroscopy, Pentacam tomography, and the CorVis ST (CST). The CST is a non-contact tonometer coupled with an ultra-high speed Scheimpflug camera which provides descriptors of ocular biomechanics. Furthermore, specialised software was designed in house to remove the collateral globe displacement to the air-pulse to isolate the maximum corneal deformation (MCD). A multiple regression analysis was used to compare CST outputs and additionally derived parameters between groups after controlling for patient age, intra-ocular pressure (IOP), central corneal thickness (CCT), maximum simulated keratometry (K_MAX), suture number, and time from surgery.

Results : This study included 42 PKP, 27 DALK, and a 152 healthy control eyes. There were no significant differences in patient age, IOP, time from surgery, K_MAX, donor size, and donor age, between treated groups (p>0.05). CCT was significantly higher in DALK-treated corneas (590 ± 52µm, p<0.001) (compared to PKP-treated (542 ± 50µm), and healthy control corneas (544 ± 34µm)). Furthermore, there were no significant differences in patient age, IOP, and K_MAX between treated and control groups (p>0.05). However, multiple regression analysis revealed a significantly higher MCD in PKP-treated corneas (0.86 ± 0.02mm) than in DALK (0.80 ± 0.02 mm, p=0.03) and healthy controls (0.79 ± 0.01mm, p=0.02). Additionally, the PKP-treated corneas had a greater number of parameters significantly different to control corneas than DALK-treated corneas.

Conclusions : DALK-treated corneas were biomechanically more similar to healthy controls than PKP-treated corneas. This might be due to the scar tissue interface in DALK-treated corneas redirecting the force applied to the peripheral cornea and the scar interface in PKP-treated corneas resulting in an incomplete transfer of energy to the peripheral cornea.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.