LASIK ablation centration: an objective digitized assessment and comparison between two generations of an excimer laser.

PURPOSE: To objectively define the effective centration of myopic femtosecond laser-assisted LASIK ablation pattern, evaluate the difference between achieved versus planned excimer laser ablation centration, and compare these results from two different generations of an excimer laser system. METHODS: The study retrospectively evaluated 280 eyes subjected to myopic LASIK. Digital image analysis was performed on Scheimpflug sagittal curvature maps (difference of preoperative to postoperative). Centration was assessed via proprietary software digital analysis of the coordinate displacement between the achieved ablation geometric center and the planned ablation center, which was the corneal vertex. Results from two different excimer laser generations (Eye-Q 400 [140 eyes] and EX500 [140 eyes]; Alcon/WaveLight, Fort Worth, TX) were compared. RESULTS: Radial displacement was on average 360 ± 220 µm (range: 0 to 1,030 µm) in the Eye-Q 400 laser group and 120 ± 110 µm (range: 0 to 580 µm) in the EX500 laser group (P < .01). The percentage of eyes with displacement of greater than 300 µm was 52% in the Eye-Q 400 laser group and 4% in the EX500 laser group. CONCLUSIONS: Displacement of ablation pattern may depend on the laser platform used. The improvement in the efficiency of centration indicates that newer generation excimer lasers with faster eye tracking and active centration control appear to achieve a significantly more accurate centration of myopic ablation patterns. The authors propose this novel, objective technique for laser refractive surgeon evaluation may point out significant outcome measures not currently used in standard metrics of refractive laser efficiency.

Keratoconus management: long-term stability of topography-guided normalization combined with high-fluence CXL stabilization (the Athens Protocol).

PURPOSE: To investigate refractive, topometric, pachymetric, and visual rehabilitation changes induced by anterior surface normalization for keratoconus by partial topography-guided excimer laser ablation in conjunction with accelerated, high-fluence cross-linking. METHODS: Two hundred thirty-one keratoconic cases subjected to the Athens Protocol procedure were studied for visual acuity, keratometry, pachymetry, and anterior surface irregularity indices up to 3 years postoperatively by Scheimpflug imaging (Oculus Optikgeräte GmbH, Wetzlar, Germany). RESULTS: Mean visual acuity changes at 3 years postoperatively were +0.38 ± 0.31 (range: -0.34 to +1.10) for uncorrected distance visual acuity and +0.20 ± 0.21 (range: -0.32 to +0.90) for corrected distance visual acuity. Mean K1 (flat meridian) keratometric values were 46.56 ± 3.83 diopters (D) (range: 39.75 to 58.30 D) preoperatively, 44.44 ± 3.97 D (range: 36.10 to 55.50 D) 1 month postoperatively, and 43.22 ± 3.80 D (range: 36.00 to 53.70 D) up to 3 years postoperatively. The average Index of Surface Variance was 98.48 ± 43.47 (range: 17 to 208) pre-operatively and 76.80 ± 38.41 (range: 7 to 190) up to 3 years postoperatively. The average Index of Height Decentration was 0.091 ± 0.053 µm (range: 0.006 to 0.275 µm) preoperatively and 0.057 ± 0.040 µm (range: 0.001 to 0.208 µm) up to 3 years postoperatively. Mean thinnest corneal thickness was 451.91 ± 40.02 µm (range: 297 to 547 µm) preoperatively, 353.95 ± 53.90 µm (range: 196 to 480 µm) 1 month postoperatively, and 370.52 ± 58.21 µm (range: 218 to 500 µm) up to 3 years postoperatively. CONCLUSIONS: The Athens Protocol to arrest keratectasia progression and improve corneal regularity demonstrates safe and effective results as a keratoconus management option. Progressive potential for long-term flattening validates using caution in the surface normalization to avoid overcorrection.

Corneal refractive power and symmetry changes following normalization of ectasias treated with partial topography-guided PTK combined with higher-fluence CXL (the Athens Protocol).

PURPOSE: To investigate preoperative and postoperative anterior and posterior keratometry and simulated corneal astigmatism in keratoconic eyes treated with collagen cross-linking combined with anterior surface normalization by partial topography-guided excimer ablation (the Athens Protocol). METHODS: Anterior and posterior corneal keratometry were measured by Scheimpflug imaging for 267 untreated keratoconic eyes. Following treatment, they were assessed 1 year postoperatively. RESULTS: Before treatment, average anterior keratometric value was 47.06 ± 6.02 diopters (D) for flat and 51.24 ± 6.75 D for steep. The posterior keratometric values were -6.70 ± 0.99 D (flat) and -7.67 ± 1.15 D (steep). Anterior astigmatism was on average with-the-rule (-1.97 ± 6.21 D), whereas posterior astigmatism was against-the-rule (+0.53 ± 1.02 D). The posterior and anterior astigmatism were highly correlated (r(2) = 0.839). After treatment, anterior keratometric values were 43.97 ± 5.81 D (flat) and 46.55 ± 6.82 D (steep). Posterior keratometric values were -6.58 ± 1.05 D (flat) and -7.69 ± 1.22 D (steep). Anterior astigmatism was on average with-the-rule (-1.56 ± 3.80 D), whereas posterior astigmatism was against-the-rule (+0.45 ± 1.29 D). The statistically significant (P < .05) keratometric changes indicated anterior surface flattening -3.09 ± 2.67 D (flat) and -4.19 ± 2.96 D (steep). The posterior keratometric changes were not statistically significant (P > .05). CONCLUSIONS: Before treatment, there was a strong correlation between posterior and anterior corneal astigmatism. After treatment, statistically significant anterior keratometric values flattened. The posterior surface keratometric values did not demonstrate statistically significant postoperative change: there was minimal posterior change, despite the significant anterior surface normalization.

Corneal epithelial remodeling following cataract surgery: three-dimensional investigation with anterior-segment optical coherence tomography.

PURPOSE: To map corneal and epithelial layer thickness changes following cataract removal surgery employing a spectral-domain anterior-segment optical coherence tomography system. METHODS: Corneal and epithelial thickness three-dimensional profile distribution was clinically imaged preoperatively and up to 3 months postoperatively with anterior-segment optical coherence tomography in 116 consecutive cases. Descriptive statistics investigated central corneal thickness, minimum corneal thickness, and epithelial thickness at the central 2-mm area, the mean over the 6-mm area, and mid-peripherally at 5-mm ring. RESULTS: In comparison to preoperative, the center, mean, and mid-peripheral epithelial thickness at the first postoperative day increased by +2.84, +2.35, and +2.25 µm, respectively (P < .001, < .001, and = .0014). One week postoperatively, the epithelial thickness differences were -1.91, -2.62, and -2.76 µm, respectively (P < .001, < .001, and < .001). Four weeks postoperatively, the differences of -0.20, -0.59, and -0.66 µm for the center, mean, and mid-periphery were not statistically significant (P = .6449, .1512, and .11097). Three months postoperatively, the differences were -0.05, -0.28, and -0.09 µm, respectively (P = .8722, .2341, and .6431). CONCLUSIONS: Qualitative and quantitative assessment of epithelial remodeling following cataract removal indicated that the early (1 day and 1 week) corneal and epithelial thickness returned to the preoperative baseline 4 weeks postoperatively. This in vivo epithelial and corneal screening with optical coherence tomography can be valuable for the postoperative assessment and follow-up.

Longitudinal postoperative lasik epithelial thickness profile changes in correlation with degree of myopia correction.

PURPOSE: To evaluate epithelial thickness profile changes following myopic femtosecond laser-assisted LASIK in relation to the degree of myopia corrected, evaluated with a spectral-domain anterior-segment optical coherence tomography system. METHODS: Sixty-one consecutive cases were observed for corneal epithelial thickness distribution preoperatively and at 1 day, 1 week, 1 month, and 1 year postoperatively. Epithelial thickness mapping was obtained with a spectral-domain optical coherence tomography system (Optovue Inc., Fremont, CA). Descriptive statistics investigated epithelial thickness at the central 2-mm area, the mean over the central 6-mm area, and mid-peripherally at the 5-mm ring area. RESULTS: Preoperatively, the pupil center epithelial thickness was 51.67 ± 2.57 µm (range: 45 to 56 µm), mean was 51.76 ± 2.66 µm (range: 45 to 57 µm), and mid-periphery was 51.78 ± 2.71 µm (range: 46 to 57 µm). Compared to the preoperative values, the epithelial thickness for the center, mean, and mid-periphery was −0.30, +1.07, and +1.35 µm at 1 week, +1.58, +2.88, and +3.31 µm at 1 month (P = .0036, < .001, and < .001), and +1.42, +2.90, and +3.19 µm at 1 year postoperatively (P = 0.146, < .001, and < .001), respectively. The correlation analysis between the epithelial thickness increase and the spherical equivalent of myopic correction showed a trend toward epithelial thickness increase with the amount of myopic ablation, particularly at the mid-peripheral 5-mm area. CONCLUSIONS: In this comprehensive study of postoperative corneal epithelial thickness remodeling following femtosecond laser-assisted myopic LASIK correction, an increase at the 1-month and up to 1-year postoperative interval suggested postoperative epithelial activity in connection to the extent of ablation.

Ray-Tracing Customization in Myopic and Myopic Astigmatism LASIK Treatments for Low and High Order Aberrations Treatment: 2-Year Visual Function and Psychometric Value Outcomes of a Consecutive Case Series.

Purpose: The safety and long-term efficacy of automated ray-tracing customized myopic and myopic astigmatic femtosecond laser-assisted LASIK. Methods: This consecutive case series retrospective analysis, of 20 subjects (40 eyes) treated with automated raytracing named Wavelight Plus, to include low and high order aberrations based on a three-dimensional custom virtual eye for each case-calculated from interferometry data-obtained from a single diagnostic device that also provides Hartman-Shack Wavefront and Scheimpflug tomography data. We evaluated before and after the customized LASIK procedure: visual acuity, refractive error, high order aberrations, contrast sensitivity, and psychometric post-operative visual function data. Results: At 24 months, the comparison of the pre-operative to the post-operative refractive and visual function value changes in average were: subjective manifest refraction from -4.38 ± 2.54 diopters (D) (range -9.75 to -1.25 D) to +0.11 ± 0.19 D; subjective manifest refractive astigmatism from -0.76 ± 0.91 D (range -2.75 to 0 D) to -0.13 ± 0.16 D, corneal astigmatism from -1.16 ± 0.64 D (range -0.2 to -2.8) to -0.47 ± 0.11 D. 65% of the eyes studied demonstrated an increase of at least one line of vision, while from the same group 38% demonstrated 2 lines of increase. High order aberrations, contrast sensitivity as well as the subjective psychometric input based on the VFQ-25 questionnaire demonstrated actual improvement. Conclusion: This longer-term follow-up, single-arm retrospective consecutive case series documents LASIK treatment customization that appears to be safe and effective in the correction of myopia and myopic astigmatism. Markedly improved objective and subjective visual function post-operatively, underlying the potential importance of simultaneously attempting to correct high order aberrations and improving the spatial alignment of total, measured human eye optics.

Topographic Keratoconus Incidence in Greece Diagnosed in Routine Consecutive Cataract Procedures: A Consecutive Case Series of 1250 Cases over 5 Years.

Background: Scheimpflug tomography has for many years been an integral part of our pre-operative assessment in cataract extraction. We retrospectively reviewed the incidence of topographic keratoconus and keratoconus suspicion in our routine cataract surgery population over 5 years. Setting: The Laservision Clinical and Research Institute, Athens, Greece. Methods: In 1250 consecutive cataract surgery cases in otherwise naïve eyes, accounting for years 2017 to 2021, we retrospectively evaluated preoperative Pentacam HR imaging. The cases already classified as keratoconus were included in group A. The residual cases were assessed by five different experienced evaluators (two ophthalmic surgeons and three optometrists) for topographic and tomographic keratoconus suspicion based on irregular pachymetry distribution, astigmatism truncation, and/or astigmatic imaging irregularity and included in group B. Regular corneas, by this assessment, were included in group C; irregular corneas, as determined by the evaluators but unrelated to keratoconus, were included in group D. Results: Based on the above, 138 cases (11.08%) were classified by Pentacam tomography as keratoconus and by default were included in group A. Of the residual cases, 314 or 25.12% were classified as suspect keratoconus and included in group B; 725 cases (58%) were classified as normal and non-keratoconus and included in group C; and 73 cases or 5.84% were placed in group D as non-keratoconus but abnormal. There was no disagreement between the five evaluators over any of the cases in groups C and D, and little variance among them for cases included in group B (less than 5% by ANOVA). Conclusions: The incidence of keratoconus and corneas suspicious for keratoconus in Greece appears to be much higher than respective reports from other regions: one in ten Greeks appear to have topographic keratoconus, most not diagnosed even by the age of cataract surgery, and almost an additional one in four may have suspicious corneal imaging for keratoconus. These data strongly imply that routine screening for disease should be promoted among Greeks, especially during puberty, to halt possible progression; moreover, careful screening should be performed when laser vision correction is being considered.

International Multicenter, Myopic and Myopic Astigmatism Femto LASIK, Customized by Automated Ray-Tracing Ablation Profile Calculation: A Postmarket Study.

Purpose: To assess the safety and efficacy of a customized ablation treatment (InnovEyes) to correct myopia and myopic astigmatism with femtosecond laser-assisted in situ keratomileusis (Femto LASIK). Patients and Methods: In this prospective, nonrandomized, multicenter study, 113 patients (225 eyes) with preoperative myopia less than -9.0 diopters (D) and astigmatism 0 to -4.0 D (based on InnovEyes refraction) underwent wavefront, tomography, and biometry assessment using a single diagnostic device (InnovEyes sightmap). These data were imported and used unmodified by the InnovEyes algorithm to automatically calculate and optimize correction of lower- and higher­order aberrations (HOAs) treated by the EX500 ablation profile. Visual acuity, refractive error, HOAs, and patient satisfaction were evaluated over 3 months. Results: A total of 106 patients (212 eyes) completed the study and were included in the analysis. Mean preoperative manifest refraction spherical equivalent (MRSE) was -3.38±1.76 D. At Month 3, uncorrected distance visual acuity was 20/20 or better in 208/212 (98.1%) eyes, and it was the same as, or better than, the preoperative best-corrected distance visual acuity (CDVA) in 162/212 (76.4%) eyes; 76/212 (35.8%) eyes gained ≥1 line of CDVA. MRSE was within ±0.5 D in 195/212 (92.0%) eyes. Additionally, 201/209 (96.2%) eyes had no change (defined as a change between -0.1 µm and 0.1 µm, inclusive) in HOAs, and 105/106 (99.1%) patients reported to be satisfied with the results. Conclusion: Customizing ray-tracing Femto LASIK with this platform appeared safe and effective in correcting myopic astigmatism and also achieved a significant percentage of eyes gaining lines of vision, potentially by addressing HOAs, along with a consistently high level of patient satisfaction.

Very high fluence collagen cross-linking as a refractive enhancement of a regressed previous astigmatic keratotomy.

PURPOSE: To report a novel application of collagen cross-linking (CXL) in refractive astigmatic enhancement of previously performed astigmatic keratotomy. METHODS: A 28-year-old woman with prior history of bioptics correction of high myopic astigmatism with femtosecond laser-assisted astigmatic keratotomy followed by topography-guided LASIK showed long-term regression of the astigmatism 4 years later. A novel CXL application was employed in an attempt to reverse the regression of the astigmatic keratotomy. RESULTS: The high fluence CXL intervention resulted in correction of 2 diopters of topographic and refractive cylinder. Uncorrected distance visual acuity changed from 20/50 to 20/20 and refraction from -0.50 -2.00 @ 90 to +0.25 -0.25 @ 90 at the 7-month follow-up. CONCLUSIONS: A possible novel application of high fluence CXL with refractive cornea effect is introduced. It may offer rapid and simple rehabilitation and its effect may be tapered.

Refractive and keratometric stability in high myopic LASIK with high-frequency femtosecond and excimer lasers.

PURPOSE: To evaluate safety, efficacy, ergonomy, and refractive and keratometric stability in high myopia LASIK procedures using a novel femtosecond and excimer laser surgery platform. METHODS: One hundred sixteen eyes in consecutive cases of high myopic LASIK ( ≥ -6.00 diopters [D]) with the Alcon-WaveLight FS200 femtosecond and EX500 excimer lasers (Alcon Laboratories, Fort Worth, TX) were evaluated preoperatively and postoperatively for the following parameters: refractive error, corrected distance visual acuity, uncorrected distance visual acuity, spherical equivalent correction, keratometry (with Placido topography and Scheimpflug tomography), and refractive astigmatism. Average follow-up time was 6.2 months (range: 3 to 12 months). RESULTS: Postoperative average refractive error was -0.37, -0.43, and -0.25 D for the 3-, 6-, and 12-month period, compared to -7.67 ± 1.55 D preoperatively. At 3, 6, and 12 months postoperatively 94%, 96.3%, and 100% of eyes, respectively, were within 1.0 D defocus equivalent. Postoperative refractive astigmatism was -0.21, -0.21, -0.13 D for the 3-, 6-, and 12-month period compared to -1.07 ± 1.91 D preoperatively. The proportion of eyes with postoperative astigmatism within 0.25 D was 85.3%, 81.5%, and 100%, for the 3-, 6-, and 12-month visit, respectively. Keratometric stability was within 0.22 D after the 12-month visit. There was no epithelial ingrowth or diffuse lamellar keratitis in any case. CONCLUSIONS: Clinical outcomes with this technique and technology appear to be promising in high level uncorrected visual rehabilitation of high myopia. There was small regression potential in the sample evaluated.

Combined Photorefractive Keratectomy and Corneal Cross-Linking for Keratoconus and Ectasia: The Athens Protocol.

ABSTRACT: Customized photorefractive keratectomy with minimal tissue ablation combined with corneal cross-linking seems to be a long-term safe and effective strategy for anatomical and visual management of keratoconus, postsurgical ectasia, and other ectasia management. Multiple published studies, many with long-term follow-up, have supported the Athens Protocol and its various forms as a means to manage corneal ectatic disorders, which not only stabilize corneal shapes but also improve functional vision.

Topography-guided hyperopic LASIK with and without high irradiance collagen cross-linking: initial comparative clinical findings in a contralateral eye study of 34 consecutive patients.

PURPOSE: To evaluate the safety and efficacy of intrastromally applied collagen cross-linking (CXL) in a comparative contralateral eye study of topography-guided femtosecond laser-assisted hyperopic LASIK. METHODS: Thirty-four consecutive patients with hyperopia and hyperopic astigmatism elected to have bilateral topography-guided LASIK and were randomized to receive a single drop of 0.1% sodium phosphate riboflavin solution under the flap followed by 3-minute exposure of 10 mW/cm2 ultraviolet A (UVA) light with the flap realigned in one eye (CXL group) and no intrastromal CXL in the contralateral eye (no CXL group). All eyes were treated with the WaveLight FS200 femtosecond laser and WaveLight EX500 excimer laser (Alcon Laboratories Inc). Refractive error and keratometric, topographic, and tomographic measurements were evaluated over mean follow-up of 23 months. RESULTS: Preoperatively, mean spherical equivalent refraction was +3.15 +/- 1.46 diopters (D) and +3.40 +/- 1.78 D with a mean cylinder of 1.20 +/- 1.18 D and 1.40 +/- 1.80 D and mean uncorrected distance visual acuity (UDVA) (decimal) of 0.1 +/- 0.26 and 0.1 +/-0.25 in the CXL and no CXL groups, respectively. At 2 years postoperatively, mean spherical equivalent refraction was -0.20 +/- 0.56 D and +0.20 +/- 0.40 D with mean cylinder of 0.65 +/- 0.56 D and 0.76 +/- 0.72 D and mean UDVA of 0.95 +/- 0.15 and 0.85 +/- 0.23 in the CXL and no CXL groups, respectively. Eyes with CXL demonstrated a mean regression from treatment of +0.22 +/- 0.31 D, whereas eyes without CXL showed a statistically significant greater regression of +0.72 +/- 0.19 D (P = .0001). CONCLUSIONS: Topography-guided hyperopic LASIK with or without intrastromal CXL is safe and effective, with greater long-term efficacy (less regression) in eyes with CXL. Our data suggest that the regression seen with hyperopic LASIK may be related to biomechanical changes in corneal shape over time.

Presbyopic Corneal Inlay Extrusion Consequent to Sterile Keratolysis: Surgical Revision and Long-Term Management.

PURPOSE: The purpose of this study was to report a serious complication of early sterile keratolysis associated with a presbyopia inlay implantation combined with hyperopic laser in situ keratomileusis (LASIK). METHODS: A 55-year-old hyperopic man underwent uneventful topography-guided bilateral femtosecond laser-assisted hyperopic LASIK, combined with same-day polymer refractive inlay implantation in the nondominant eye for additional presbyopia correction. Within 2 months, anterior sterile keratolysis and partial extrusion required surgical explantation of the inlay, and long-term medical management over 9 years achieved effective visual rehabilitation documented also with corneal imaging. RESULTS: Immediate postoperative results were binocular 20/20 uncorrected distance visual acuity and J1 uncorrected near visual acuity. The early progressive anterior sterile keratolysis and partial extrusion necessitated surgical explantation at 2 months, severe anterior scarring of the perforated flap area and severe focal flattening of the cornea of over 10 diopters, developed despite aggressive topical corticosteroid use. The uncorrected distance visual acuity in the OS dropped from 20/25 to 20/400. The LASIK flap portion that underwent keratolysis and perforated, remodeled long-term from a scarred, epithelial plug with early significant surface concavity to evidently a mild subepithelial localized hazy area with regularized curvature over a period of 9 years. CONCLUSIONS: Some refractive synthetic corneal inlays have been recalled because they may result in significant corneal haze. We present herein a case of severe keratolysis that necessitated surgical explantation and further document long-term care for eventual visual rehabilitation.

Concordance of keratoconus in monozygotic twins before and after combined corneal crosslinking/photorefractive keratectomy (Athens Protocol) using Scheimpflug and OCT tomography.

PURPOSE: To describe the concordance of keratoconus (KC) expression in 2 pairs of monozygotic twins before and after a combined corneal crosslinking (CXL)/photorefractive keratectomy (PRK) procedure. SETTING: Private ambulatory eye surgery unit. DESIGN: Retrospective interventional twin study. METHODS: Two pairs of male monozygotic twins with KC were studied retrospectively. Improvement of flattest (K1) and steepest (K2) keratometry, index of height decentration (IHD), and corneal thickness at the thinnest point and corneal epithelial thickness measured by anterior segment optical coherence tomography and Scheimpflug tomography was compared between respective eyes of monozygotic twin siblings 1 to 5 years after the application of combined CXL and topography-guided 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 the thinnest point, and corneal epithelial thickness percentage improvement between the right eyes of each pair of twins was statistically significant 1 year and 5 years postoperatively (P < .05). Statistically significant discordance in the aforementioned parameters percentage improvement was similarly observed between the left eyes of each pair of twins (P < .05). CONCLUSIONS: Although a genetic predisposition in KC 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.

Management of corneal ectasia after LASIK with combined, same-day, topography-guided partial transepithelial PRK and collagen cross-linking: the athens protocol.

PURPOSE: To evaluate a series of patients with corneal ectasia after LASIK that underwent the Athens Protocol: combined topography-guided photorefractive keratectomy (PRK) to reduce or eliminate induced myopia and astigmatism followed by sequential, same-day ultraviolet A (UVA) corneal collagen cross-linking (CXL). METHODS: Thirty-two consecutive corneal ectasia cases underwent transepithelial PRK (WaveLight ALLEGRETTO) immediately followed by CXL (3 mW/cm(2)) for 30 minutes using 0.1% topical riboflavin sodium phosphate. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent, keratometry, central ultrasonic pachymetry, corneal tomography (Oculus Pentacam), and endothelial cell counts were analyzed. Mean follow-up was 27 months (range: 6 to 59 months). RESULTS: Twenty-seven of 32 eyes had an improvement in UDVA and CDVA of 20/45 or better (2.25 logMAR) at last follow-up. Four eyes showed some topographic improvement but no improvement in CDVA. One of the treated eyes required a subsequent penetrating keratoplasty. Corneal haze grade 2 was present in 2 eyes. CONCLUSIONS: Combined, same-day, topography-guided PRK and CXL appeared to offer tomographic stability, even after long-term follow-up. Only 2 of 32 eyes had corneal ectasia progression after the intervention. Seventeen of 32 eyes appeared to have improvement in UDVA and CDVA with follow-up >1.5 years. This technique may offer an alternative in the management of iatrogenic corneal ectasia.

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

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.

Comparison of effective corneal refractive centration to the visual axis: LASIK vs SMILE, a contralateral eye digitized comparison of the postoperative result.

PURPOSE: To define and compare the centration of the ablation effect in laser in situ keratomileusis (LASIK) with the corresponding effect in small-incision lenticule extraction (SMILE), in myopic laser vision correction to possibly explain the refractive performance differences noted between the two procedures in a contralateral eye study. SETTING: Private ambulatory eye surgery unit. DESIGN: Prospective randomized contralateral eye study. METHODS: In 22 consecutive patients (44 eyes), 1 eye was prospectively randomized to undergo myopic topography-guided LASIK treatment and the contralateral eye to undergo SMILE; digital image analysis of the achieved centration to the aimed corneal vertex was assessed for both procedures on perioperative Scheimpflug tangential curvature maps, using a proprietary digitized methodology. RESULTS: The radial displacement measured in micrometers in the above treated 44 eyes, between the attempted centration point on the corneal vertex vs the center of the measured effective anterior corneal curvature flattening was on average 130 ± 62 mm in the 22 eyes of LASIK group and 313 ± 144 mm in the 22 contralateral eyes of the SMILE group (P < .001). CONCLUSIONS: In this contralateral eye study, topography-guided myopic LASIK was found to achieve significantly better effective centration compared with myopic SMILE, in regard to 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 with the contralateral SMILE group eyes.

Comparison of Planned Versus Achieved Central Stromal Thickness Reduction in LASIK Versus SMILE: A Contralateral Eye Study.

PURPOSE: 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: At 3 months postoperatively, LASIK had a lower difference between planned versus attempted stromal thickness reduction compared to SMILE (13.72 ± 14.45 vs 24.00 ± 19.45 µm, P = .03). Graphical analysis revealed this deviation to be exaggerated in higher myopic errors, when a higher maximum stromal reduction was planned. The mean stromal reduction thickness was 83.40 ± 29.52 µm achieved versus 97.13 ± 25.69 µm mean planned ablation depth in the LASIK group (P < .001) compared to 76.45 ± 29.69 µm achieved versus 100.45 ± 26.56 µm planned ablation depth in the SMILE group (P < .001). CONCLUSIONS: LASIK had a significantly lower difference between planned versus achieved stromal thickness reduction when compared to SMILE (P = .03). This difference was more apparent in higher myopic corrections. [J Refract Surg. 2021;37(7):454-459.].

Scheimpflug vs Scanning-Slit Corneal Tomography: Comparison of Corneal and Anterior Chamber Tomography Indices for Repeatability and Agreement in Healthy Eyes.

PURPOSE: 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: 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: 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: 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.