Evaluation of corneal structures in myopic eyes more than twenty‐two years after photorefractive keratectomy

Abstract

The aim of this study is to evaluate corneal epithelial thickness (CET), corneal densitometry (CD) in 84 myopic eyes (57 patients) more than 22 years after photorefractive keratectomy, using anterior segment-optical coherence tomography (AS-OCT) and Scheimpflug imaging system. The CET was significantly higher in all operated eyes than in unoperated eyes in central sector. A statistically significant increase in CD in corneal anterior layer of central sector was shown in groups of operated eyes with greater ablation depth respect to unoperated eyes. While there was no significant difference in CD between the operated eyes groups with lower ablation depth and unoperated eyes. A significant trend toward higher values in anterior CD with deeper ablations in central sector was found. These noninvasive imaging techniques allow to better understand the corneal remodeling process after photoablation and to monitor the patients over time.

Corneal optical density: Structural basis, measurements, influencing factors, and roles in refractive surgery

“…At 3 months post-surgery, a decreased level of haze was associated with a reduction in COD ( Boulze-Pankert et al, 2016 ). In order to evaluate the long-term effect of PRK on corneal densitometry, a recent study was carried out based on myopic patient who had photorefractive keratectomy more than 22 years ( Montorio et al, 2020 ). The authors demonstrated that the COD of the anterior layer in the central zone of the cornea was significantly increased in eyes that had been operated on with greater ablation depth in comparison with unoperated eyes ( Montorio et al, 2020 ).…”

“…In order to evaluate the long-term effect of PRK on corneal densitometry, a recent study was carried out based on myopic patient who had photorefractive keratectomy more than 22 years ( Montorio et al, 2020 ). The authors demonstrated that the COD of the anterior layer in the central zone of the cornea was significantly increased in eyes that had been operated on with greater ablation depth in comparison with unoperated eyes ( Montorio et al, 2020 ). However, there was no significant difference in the CODs of eyes operated on with lower ablation depth and unoperated eyes ( Montorio et al, 2020 ).…”

“…The authors demonstrated that the COD of the anterior layer in the central zone of the cornea was significantly increased in eyes that had been operated on with greater ablation depth in comparison with unoperated eyes ( Montorio et al, 2020 ). However, there was no significant difference in the CODs of eyes operated on with lower ablation depth and unoperated eyes ( Montorio et al, 2020 ).…”

A formula to improve the reliability of optical axial length measurement in IOL power calculation

“…The precision of IOL power calculation after cataract surgery relies on the accurate measurement of the axial length (AL), the mean corneal power (Km) and the estimation of the effective lens position (ELP) 1 . In eyes that underwent corneal refractive surgery 2 – 8 or with corneal irregularities 9 , 10 , these values could be unreliable. These measurements, performed before surgery, do not consider eventual surgical induced changes that could influence the surgical outcome.…”

Comparison between two devices in the detection of corneal thickness changes after cataract surgery

“…Recently, a precise corneal thickness (CT) evaluation has triggered an ever-increasing interest, as a reliable predictor of corneal health 1 . Furthermore, in clinical practice CT is used in case of corneal refractive surgery 2 – 6 , to differentiate contact lens-induced corneal warpage from keratoconus 7 , endothelial cells health and function 8 – 10 , intraocular pressure (IOP) evaluation 11 , 12 . CT measurements can be achieved with devices based on different techniques such as: confocal microscopy, optical coherence tomography (OCT), slit scanning corneal tomography (Orbscan), optical pachymetry with rotating Scheimpflug camera (Pentacam, Precisio, Galilei), dual beam partial coherence interferometry (PCI), contact and non-contact specular microscopy (SM), ultrasound biomicroscopy (UBM) and ultrasound pachymetry (UP).…”