Keratoconus Management With Customized Photorefractive Keratectomy by Artificial Intelligence Ray-Tracing Optimization Combined With Higher Fluence Corneal Crosslinking: The Ray-Tracing Athens Protocol
PURPOSE/OBJECTIVE: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.
Comparison of Planned Versus Achieved Central Stromal Thickness Reduction in LASIK Versus SMILE: A Contralateral Eye Study
PURPOSE/OBJECTIVE:To compare attempted versus achieved corneal stromal thickness reduction in a consecutive case series of patients undergoing laser in situ keratomileusis (LASIK) in one eye and small incision lenticule extraction (SMILE) in the other eye. METHODS:This prospective, randomized, contralateral eye study included 22 consecutive patients (44 eyes), one eye randomized to have myopic LASIK and the contralateral eye to have SMILE. Anterior segment optical coherence tomography was performed preoperatively and at 3 months postoperatively. For each of the treatment groups, the achieved maximum stromal thickness reduction was compared to the planned/attempted thickness. The deviation of planned versus achieved stromal thickness reduction was then compared between the two groups. RESULTS:< .001). CONCLUSIONS:.
Keratoconus concordance in monozygotic twins before and after combined CXL/PRK (Athens Protocol) using Scheimflung and OCT tomography
PUPOSE/UNASSIGNED:To describe the concordance of keratoconus expression in two pairs of monozygotic twins before and after a combined CXL/PRK procedure. SETTING/METHODS:Private Ambulatory Eye Surgery Unit. DESIGN/METHODS:Retrospective Interventional Twin Study. METHODS:Two pairs of male monozygotic twins with keratoconus (KCN) were studied retrospectively. Improvement of flattest (k1) and steepest (k2) keratometry, Index of Height Decentration (IHD), corneal thickness at thinnest point and corneal epithelial thickness measured by AS-OCT and Scheimpflug tomography was compared between respective eyes of monozygotic twin siblings 1 to 5 years after the application of combined corneal cross linking (CXL) and topography guided photorefractive keratectomy (PRK) of part of the refractive error (the Athens Protocol). RESULTS:Significant improvement was noted in all the keratometric indices of all 8 eyes after the combined CXL/PRK procedure.The difference in k1, k2, IHD corneal thickness at thinnest point and corneal epithelial thickness percentage improvement between the right eyes of each pair of twins was statistically significant 1 and 5 years post-operatively (P < .05). Statistically significant discordance in the aforementioned parameters percentage improvement was likewise observed between the left eyes of each pair of twins (P < .05). CONCLUSIONS:Although a genetic predisposition in KCN is well documented, the discordance in keratometric indices improvement after a CXL/PRK procedure between respective eyes of monozygotic twins suggests that environmental influences may contribute to the disease expression as well. Variable degree of synergy in a combined CXL/PRK procedure may also explain the aforementioned discordant improvement.
Comparison of effective corneal refractive centration to the visual axis: LASIK vs. SMILE, a contralateral eye digitized comparison of the postoperative result
PURPOSE/OBJECTIVE:To define and compare the centration of the ablation effect in LASIK to the corresponding effect in SMILE, in myopic laser vision correction in order to possibly explain the refractive performance differences noted between the two procedures in a contralateral eye study. SETTING/METHODS:Private Ambulatory Eye Surgery Unit. DESIGN/METHODS:Prospective randomized contralateral eye study. METHODS:In 22 consecutive patients (44 eyes), one eye was prospectively randomized to have myopic topography-guided LASIK treatment and the contralateral eye to have SMILE; Digital image analysis of the achieved centration to the aimed corneal vertex was assessed for both procedures on the perioperative Scheimpflug tangential curvature maps, using a proprietary digitized methodology. RESULTS:The radial displacement between the attempted centration on the corneal vertex versus the center of the effective anterior corneal curvature flattening was on average 130 Â± 62 Î¼m in the LASIK group and 313 Â± 144Î¼m in the SMILE group (P<0.001). CONCLUSIONS:In this contralateral eye study, topography-guided myopic LASIK was found to achieve significantly better effective centration compared to myopic SMILE, in regards digitally measured decentration of the effective refractive change achieved in the anterior corneal curvature from the corneal vertex. This may explain the previously reported superior visual outcomes in the LASIK group eyes when compared to the contralateral SMILE group eyes.
Does Pregnancy Affect Refractive and Corneal Stability or Corneal Epithelial Remodeling After Myopic LASIK?
PURPOSE/OBJECTIVE:To investigate possible refractive changes in pregnant women who have previously undergone myopic laser in situ keratomileusis (LASIK). METHODS:This prospective study included 64 pregnant women (128 eyes) who had previously undergone bilateral myopic LASIK. Uncorrected distance visual acuity (UDVA), spherical equivalent, corneal keratometry, topography and tomography, and epithelial mapping were evaluated before LASIK, 12 months after LASIK, during the third trimester of pregnancy, and 1 year postpartum. RESULTS:The average age at the time of recruitment was 32.5 Â± 5 years (range: 24.5 to 39.5 years). The evaluation during pregnancy was at an average 55 months (range: 12 to 108 months) from the initial LASIK procedure. The preoperative mean refractive error was -6.72 Â± 2.96 diopters (D) (range: -1.00 to -11.00 D). Comparing 12-month refractive data after the original LASIK procedure to the those within the third trimester of the subsequent pregnancy, the average UDVA was 20/18, the residual refractive error was -0.63 Â± 1.00 to -0.51 Â± 0.82 D, the steepest keratometry value was 40.85 Â± 1.89 to 40.88 Â± 2.84 D, and the central epithelial thickness was 56.4 Â± 3.89 to 57.38 Â± 5.04 Âµm, respectively. CONCLUSIONS:In this study, pregnancy did not affect the refractive stability of LASIK. Pregnancy-related changes in refractive error, corneal stability, and total corneal and epithelial thickness in women after LASIK were not found to be statistically significant. [J Refract Surg. 2022;36(2):118-122.].
Scheimpflug vs Scanning-Slit Corneal Tomography: Comparison of Corneal and Anterior Chamber Tomography Indices for Repeatability and Agreement in Healthy Eyes
Purpose/UNASSIGNED:To evaluate and compare the repeatability and agreement of Scheimpflug vs scanning-slit tomography of the cornea and the anterior chamber in terms of keratometric and tomographic indices in healthy eyes. Methods/UNASSIGNED:The 20 eyes of 10 healthy participants underwent 3 consecutive measurements using both Scheimpflug-tomography and scanning-slit tomography, diagnostic devices. Multiple corneal and anterior chamber tomographic parameters were recorded and evaluated to include corneal keratometry and its axis; corneal best-fit sphere (BFS), pachymetry mapping, angle kappa, anterior chamber depth (ACD), pupil diameter, and location. Repeatability for each device was assessed using the within each subject standard deviation of sequential exams, the coefficient variation (CV) and the intraclass correlation coefficient (ICC). Agreement between the two devices was assessed using Bland-Altman plots with 95% limits of agreement (LoA) and correlation coefficient (r). Results/UNASSIGNED:Both devices were found to have high repeatability (ICC>0.9) both in keratometric and other tomographic measurements. Scheimpflug tomography's repeatability though appeared superior in the average keratometry values, anterior and posterior BFS, thinnest corneal pachymetry value and location (p<0.05). Agreement: Statistically significant inter-device differences were noted in the mean values of K1, K2, BFS, ACD and thinnest corneal pachymetry (p<0.05). Despite the agreement differences noted, the two devices were well correlated (r>0.8) in respective measurements with Scheimpflug delivering consistently lower values than the scanning-slit tomography device. Conclusion/UNASSIGNED:Scheimpflug-tomography repeatability was found to be superior to that of scanning-slit tomography in this specific study, in most parameters evaluated. Inter-device agreement evaluation suggests that reading from the two devices may not be used interchangeably in absolute values, yet they are well correlated with Scheimpflug delivering consistently lower values in most.
Initial Outcomes with Customized Myopic LASIK, Guided by Automated Ray Tracing Optimization: A Novel Technique
Purpose/UNASSIGNED:Safety and efficacy of a novel automated ray tracing optimization in customization of excimer ablation in myopic LASIK. Methods/UNASSIGNED:In a consecutive case series, 25 patients (50 eyes) undergoing femtosecond-laser-assisted myopic LASIK were evaluated. The novel, artificial-intelligence platform initially calculates the ablation profile based on a model eye for each case, based on interferometry axial length data. Low- and high-order aberration calculation is performed by raytracing based on wavefront and Scheimpflug tomography measurements, all from a single diagnostic device. Visual acuity, refractive error, keratometry, topography, high-order aberrations and contrast sensitivity were evaluated, over six months follow-up. Results/UNASSIGNED:Change from pre- to 6 months post-operative: mean refractive error improved from -5.06 Â± 2.54 diopters (D) (range -8.0 to -0.50 D) to -0.11 Â± 0.09 D (range -0.25 to + 0.25); refractive astigmatism from -1.07 Â± 0.91 D (range -4.25 to 0 D) to -0.15 Â± 0.04 D (range -0.25 to 0); and topographic astigmatism from -1.65 Â± 0.85 D to -0.26 Â± 0.11 D (range -0.60 to 0). About 65% of eyes gained one line of vision and 38% 2 lines. Pre- to post-operative high-order aberration average: RMSh changed from 0.25 um to 0.35 um. Contrast sensitivity improved post-operatively. Conclusion/UNASSIGNED:We report safe and effective preliminary outcomes with a novel excimer laser customization by ray tracing optimization, for myopic LASIK treatments, employing several independent up-till-now diagnostics and a customized eye model reference for each case. It bears the potential advantage through total eye aberration data and ray tracing refraction calculation to offer improved and more predictable visual outcomes.
December consultation #4
Ten-Year Outcomes of Progressive Keratoconus Management With the Athens Protocol (Topography-Guided Partial-Refraction PRK Combined With CXL)
PURPOSE/OBJECTIVE:To report the safety and long-term efficacy of topography-guided partial-refraction PRK combined with corneal cross-linking (CXL) (the Athens Protocol), refractive, topographic, and pachymetric changes of keratoconic eyes treated were studied. METHODS:Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refraction, keratometry, qualitative and quantitative assessment of corneal keratometric, and pachymetric properties recorded by topography and tomography were evaluated for 10 years postoperatively. RESULTS:A total of 144 eyes were followed up for a mean 128 Â± 4 months (range: 120 to 146 months). Mean UDVA markedly improved at 1 year (0.19 Â± 0.17 to 0.53 Â± 0.21 decimal) with further improvement to 0.55 Â± 0.19 decimal at 10 years. CDVA increased from 0.59 Â± 0.21 to 0.80 Â± 0.17 decimal at 1 year and further to 0.81 Â± 0.19 decimal at 10 years. Corneal thickness decreased from 468.74 Â± 35.05 to 391.14 Â± 40.07 Î¼m at 1 year (P < .01) and up to 395.42 Â± 32.21 Î¼m at 10 years. Steep keratometry decreased from 50.57 Â± 2.80 to 45.87 Â± 2.70 diopters (D) (P < .01) at 1 year and to 44.00 Â± 3.22 D at 10 years. Maximum keratometry decreased from 53.43 Â± 2.97 to 46.17 Â± 1.18 D at 1 year and 44.75 Â± 2.14 D at 10 years (P < .01). A total of 94.4% demonstrated ectasia stabilization and 3.5% showed progressive "overcorrection" or "hyperopic" shift. CONCLUSIONS:The Athens Protocol confirms long-term safety and efficacy for corneal ectasia and visual function. Most parameters had little change after 1 year, through year 10. [J Refract Surg. 2019;35(8):478-483.].
Long-Term Stability With the Athens Protocol (Topography-Guided Partial PRK Combined With Cross-Linking) in Pediatric Patients With Keratoconus
PURPOSE/OBJECTIVE:To evaluate the safety, efficacy, and stability of topography-guided partial PRK combined with corneal cross-linking (CXL) (the Athens Protocol [AP]) in pediatric patients with keratoconus over a 4-year follow-up period. METHODS:This prospective study included 39 keratoconic eyes of 21 patients younger than 18 years with clinical and imaging evidence of keratoconus progression. Partial topography-guided excimer laser ablation in conjunction with high-fluence CXL was performed in all patients according to the AP. Uncorrected distance visual acuity, corrected distance visual acuity, refraction, keratometry, endothelial cell density, topography, and tomography using both Scheimpflug and optical coherence tomography (OCT) were evaluated for 4 years postoperatively. RESULTS:At 4 years postoperative, there was significant improvement in mean uncorrected distance visual acuity from 0.51 Â± 0.31 (decimal) to 0.65 Â± 0.26 (decimal; P < 0.05). Mean corrected distance visual acuity improved from 0.71 Â± 0.22 (decimal) preoperatively to 0.81 Â± 0.19 (decimal; P < 0.05), respectively. Mean flat keratometry (K1) and mean steep keratometry (K2) readings reduced from 44.95 Â± 3.71 D and 49.32 Â± 5.05 D, respectively, preoperatively to 43.14 Â± 2.95 D and 46.28 Â± 4.87 D, respectively, (P < 0.05) at 4 years. The mean anterior maximum keratometry (Kmax) reading reduced from 56.81 Â± 2.94 D preoperatively to 48.11 Â± 3.17 D at 48 months. The mean index of height decentration was 0.105 Â± 0.054 Î¼m preoperatively and 0.049 Â± 0.024 (P < 0.05) at 4 years postoperative. Mean preoperative corneal thickness at the thinnest point was 436.7 Â± 42.6 Î¼m preoperatively, 392.50 Â± 45.68 Î¼m at 12 months postoperative, and 418.42 Â± 17.01 Î¼m at 4-year follow-up. Late-onset deep corneal haze, a potential intrinsic complication of this technique in pediatric patients, was encountered in 2 cases at least 1 year after the procedure. CONCLUSIONS:Long-term results of the AP seem to be safe and effective in pediatric patients, with marked improvement in visual function and keratometric symmetry indices.