Keratoconus Management With Customized Photorefractive Keratectomy by Artificial Intelligence Ray-Tracing Optimization Combined With Higher Fluence Corneal Crosslinking: The Ray-Tracing Athens Protocol

Abstract

Purpose: The aim of this study was to report novel ray-tracing customization of surface excimer laser ablation combined with higher fluence corneal crosslinking (CXL) in the stabilization and normalization of ectasia and visual rehabilitation of progressive keratoconus. Methods: A 28-year-old man with bilateral progressive keratoconus was treated with Athens protocol: CXL combined with photorefractive surface ablation customized by a novel artificial intelligence platform calculating lower- and higher-order aberrations based on wavefront, Scheimpflug tomography, and interferometry axial length data from a single diagnostic device. Visual acuity, refractive error, keratometry, optical coherence tomography and Scheimpflug tomography, and endothelial cell density were evaluated over 12 months. Results: Keratoconus stabilized in both eyes. Uncorrected distance visual acuity changed from 20/80 to 20/20 in the OD and from 20/40 to 20/25 in the OS at 12 months. Keratometry changes were as follows: from 40.7 and 42.7 at 165.1 degrees to 41.4 and 43.1 at 169.3 degrees in the OD and from 40.9 and 42.6 at 15.9 degrees to 44.1 and 44.7 at 9.8 degrees in the OS. Corneal surface normalization was as follows: index of height decentration from 0.115 to 0.099 and index of surface variance from 77 to 67 in the OD and index of height decentration from 0.066 to 0.014 and index of surface variance from 49 to 31 in the OS. Conclusions: We introduced in this study the management of progressive keratoconus with CXL combined with novel excimer laser customization using several independent up-to-now diagnostics calculated by software, evaluating bidirectional theoretical ray tracing. It bears the potential advantage of addressing more accurately normalization of the distorted human eye optics associated with corneal ectasia, compared with using anterior corneal surface data or wavefront data alone.

Ray-Tracing Transepithelial Excimer Laser Central Corneal Remodeling Plus Pachymetry-Guided Accelerated Corneal Crosslinking for Keratoconus

“…Only a small percentage of overcorrections have been reported. 8,14 Finally, the possibility of precisely calculating the refractive contribution of the posterior corneal surface and corneal epithelium in topography-guided treatments by means of ray-tracing-guided customized ablations could make the difference by avoiding overcorrections, improving functional results, and sparing stromal tissue, as shown by pivotal studies 5,6,23 and confirmed in our case series in the long-term follow-up.…”

“…The raytraced-customized corneal t-PRK has been shown to be able to solve many of the problems reported and to place itself as a possible reference standard for the personalized programming of these special treatments. 6,7,23 In our study, topography-guided custom surface ablation followed by individualized constant-fluence pachymetryguided ACXL uses a no-touch all-surface ablation with a transepithelial approach to minimize stromal consumption, taking into account the masking effect of the corneal epithelium in KC irregular corneas. The RT t-PRK plus M nomogram ACXL protocol was based on topography-guided custom ablation with ray-traced planning.…”

“…22 The introduction of ray-tracing technology in treatment planning allows the calculation of the refractive contribution of the posterior corneal surface and epithelium, thus avoiding undesirable overcorrections often reported in the literature with topography-guided techniques and minimizing stromal tissue ablation. 23 We present the results of a tissue-preservation algorithm based on ray-tracing-guided transepithelial excimer laser CCR plus pachymetry-guided individualized ACXL treatment (M nomogram, developed by Mazzotta C at Siena Crosslinking Center, Italy) 24 in a case series of patients with stable KC who were intolerant to RGP CL and had poor QoV. The procedure was performed purely on the basis of improving visual function in patients with stable KC in the past 12 months.…”

“…22 The introduction of ray-tracing technology in treatment planning allows the calculation of the refractive contribution of the posterior corneal surface and epithelium, thus avoiding undesirable overcorrections often reported in the literature with topography-guided techniques and minimizing stromal tissue ablation. 23…”

Evaluation of the effectiveness of combined staged surgical treatment in patients with keratoconus

“…Keratoconus is a progressive bilateral pathology of cornea, which is manifested by its thinning and protrusion that lead to astigmatism and deterioration of vision [ 1 ]. Different treatment options, such as spectacles and contact lenses [ 2 ], intrastromal corneal ring segments (ICRS) [ 3 – 7 ], keratoplasty (penetrating and deep anterior lamellar), corneal collagen cross-linking (CXL) [ 8 – 11 ] with topography-guided customized excimer laser ablation treatment—photorefractive keratectomy (PRK) [ 12 – 21 ], and combinations of the above-mentioned methods [ 16 , 21 – 23 ] with the application of novel ray-tracing excimer laser customization [ 24 ] could be used in patients with keratoconus, depending on its severity and grade. All treatment methods are reported to be effective and safe.…”