Introduction of quantitative and qualitative cornea optical coherence tomography findings induced by collagen cross-linking for keratoconus: a novel effect measurement benchmark

Abstract

PurposeTo introduce a novel, noninvasive technique to determine the depth and extent of anterior corneal stroma changes induced by collagen cross-linking (CXL) using quantitative analysis of high-resolution anterior-segment optical coherence tomography (OCT) post-operative images.SettingPrivate clinical ophthalmology practice.Patients and methodsTwo groups of corneal cross-sectional images obtained with the OptoVue RTVue anterior-segment OCT system were studied: group A (control) consisted of unoperated, healthy corneas, with the exception of possible refractive errors. The second group consisted of keratoconic corneas with CXL that were previously operated on. The two groups were investigated for possible quantitative evidence of changes induced by the CXL, and specifically, the depth, horizontal extent, as well as the cross-sectional area of intrastromal hyper-reflective areas (defined in our study as the area consisting of pixels with luminosity greater than the mean +2 × standard deviation of the entire stromal cross section) within the corneal stroma.ResultsIn all images of the second group (keratoconus patients treated with CXL) there was evidence of intrastromal hyper-reflective areas. The hyper-reflective areas ranged from 0.2% to 8.8% of the cross-sectional area (mean ± standard deviation; 3.46% ± 1.92%). The extent of the horizontal hyper-reflective area ranged from 4.42% to 99.2% (56.2% ± 23.35%) of the cornea image, while the axial extent (the vertical extent in the image) ranged from 40.00% to 86.67% (70.98% ± 7.85%). There was significant statistical difference (P < 0.02) in these values compared to the control group, in which, by application of the same criteria, the same hyper-reflective area (owing to signal noise) ranged from 0.00% to 2.51% (0.74% ± 0.63%).ConclusionHerein, we introduce a novel, noninvasive, quantitative technique utilizing anterior segment OCT images to quantitatively assess the depth and cross-sectional area of CXL in the corneal stroma based on digital image analysis. Mean cross-sectional area showing evidence of CXL was 3.46% ± 1.92% of a 6 mm long segment.

Assessment of a Novel Corneal-Shaping Device With Simultaneous Corneal Collagen Cross-Linking Using a Porcine Eye Model

“…12,26 The hyperreflective demarcation line is thought to be due to induced changes in corneal density or subtle intrastromal scarring. 11,25 Our model also showed the similar presence of an anterior hyperreflective zone with stromal demarcation line by AS-OCT. However, our imaging was performed within 2 hours of the CXL treatment, which is the earliest time point that this demarcation line has been described on AS-OCT imaging to our knowledge.…”

“…The stromal demarcation line was first described as the proposed transition between the cross-linked anterior stroma and untreated posterior stroma, clinically evident as early as 2 weeks after treatment by slit-lamp examination. 11 Since then, it has become widely accepted as a biomicroscopic marker to monitor the depth of effective CXL treatment both at early and longer-term follow-up times (1 month to 3 years), 25 with similar detection by both confocal microscopy and AS-OCT imaging. 12,26 The hyperreflective demarcation line is thought to be due to induced changes in corneal density or subtle intrastromal scarring.…”

Presbyopic PiXL Cross-Linking

“…The procedure known as the Athens Protocol (AP) [38] involves sequentially excimer laser epithelial debridement (50 lm), partial topography-guided excimer laser stromal ablation, and high-fluence UVA irradiation (10 mW/cm 2 ), accelerated (10 0 ) CXL. Early results [39] as well as anterior-segment optical coherence tomography quantitative findings [40] are indicative of the long-term stability of the procedure [41].…”

Comparison of Placido disc and Scheimpflug image-derived topography-guided excimer laser surface normalization combined with higher fluence CXL: the Athens Protocol, in progressive keratoconus

“…We have also reported on sequential partial topography-guided photorefractive keratectomy in conjunction with the CXL treatment,12 which is a promising approach to improve topometric and refractive outcomes,13 with good long-term stability 14,15. Furthermore, we have introduced and extensively reported16–20 the combination of excimer-laser debridement of the top 50 μm of the epithelium, partial topography-guided excimer ablation limited to removal of a maximum of 50 μm stromal tissue, followed in the same session by immediate high-fluence ultraviolet A radiation (5, 6, and 10 mW/cm 2 ) and short-duration (18, 15, and 10 seconds) CXL in a procedure known as the Athens protocol 21,22.…”