Allowable movement of wavefront-guided contact lens corrections in normal and keratoconic eyes

PURPOSE

The goal was to use SyntEyes modelling to estimate the allowable alignment error of wavefront-guided rigid contact lens corrections for a range of normal and keratoconic eye aberration structures to keep objectively measured visual image quality at or above average levels of well-corrected normal eyes. Secondary purposes included determining the required radial order of correction, whether increased radial order of the corrections further constrained the allowable alignment error and how alignment constraints vary with keratoconus severity.

METHODS

Building on previous work, 20 normal SyntEyes and 20 keratoconic SyntEyes were fitted with optimised wavefront-guided rigid contact lens corrections targeting between three and eight radial orders that drove visual image quality, as measured objectively by the visual Strehl ratio, to near 1 (best possible) over a 5-mm pupil for the aligned position. The resulting wavefront-guided contact lens was then allowed to translate up to ±1 mm in the x- and y-directions and rotate up ±15°.

RESULTS

Allowable alignment error changed as a function of the magnitude of aberration structure to be corrected, which depends on keratoconus severity. This alignment error varied only slightly with the radial order of correction above the fourth radial order. To return the keratoconic SyntEyes to average levels of visual image quality depended on maximum anterior corneal curvature (Kmax). Acceptable tolerances for misalignment that returned keratoconic visual image quality to average normal levels varied between 0.29 and 0.63 mm for translation and approximately ±6.5° for rotation, depending on the magnitude of the aberration structure being corrected.

CONCLUSIONS

Allowable alignment errors vary as a function of the aberration structure being corrected, the desired goal for visual image quality and as a function of keratoconus severity.

Implantation of Intracorneal Ring Segments in Keratectasia: Effects on Corneal Biomechanics in 112 Eyes

PURPOSE

The aim of this study was to analyze changes in corneal biomechanical properties after implantation of intracorneal ring segments (ICRSs) in keratectasia.

METHODS

This retrospective single-center study included 112 patient eyes that underwent femtosecond laser-assisted ICRS implantation (Intacs SK; Addition Technology Inc, Des Plaines, IL) for keratectasia. Biomechanical analysis was performed using the Ocular Response Analyzer (ORA; Reichert Inc, Depew, NY), with determination of corneal resistance factor, corneal hysteresis, and Keratoconus Match Index, as well as by Corvis ST (OCULUS, Wetzlar, Germany), with determination of stiffness parameter A1, Ambrosio relational thickness to the horizontal profile (Arth), integrated radius, deformation amplitude ratio, and stress-strain index as well as Corvis Biomechanical Index and Tomographic Biomechanical Index. Data collection was performed preoperatively and 6 months postoperatively for ORA and Corvis ST and additionally after 1 and 2 years for ORA.

RESULTS

The corneal resistance factor decreased significantly postoperatively (5.8 ± 1.7 mm Hg) compared with preoperatively (6.75 ± 3.7 mm Hg; P = 0.021) and increased again during follow-up (6.2 ± 1.9 mm Hg; P = 0.024), without regaining preoperative values. Corneal hysteresis and Keratoconus Match Index did not change significantly. Stiffness parameter A1 ( P = 0.045) increased significantly after ICRS implantation and Arth decreased significantly from 181 ± 85 to 150 ± 92 ( P = 0.016). However, there was no significant postoperative change for others Corvis parameters.

CONCLUSIONS

Corneal biomechanical properties showed inconsistent changes after ICRS implantation. Classical corneal biomechanical parameters (using single central air-puff tonometers) do not seem to be suitable for follow-up after ICRS implantation.

Does collagen cross linking have any effect on retinal circulation in patients with keratoconus? An optical coherence tomography angiography (OCTA) study

BACKGROUND

We aimed to employ Optical Coherence Tomography Angiography (OCTA) to comprehensively assess changes in the optic nerve head (ONH) and macular perfusion before and after the Corneal Collagen Cross-Linking (CCL) procedure in patients with keratoconus.

METHODS

A total of 22 keratoconus patient's candidate for CCL procedures were included based on specific criteria, with meticulous exclusion criteria in place to minimize potential confounders. Participants underwent OCTA assessments of the ONH and macula using the Spectralis OCT (Heidelberg) before CCL, as well as at 1- and 3-months post-CCL. MATLAB software was utilized for image analysis.

RESULTS

The mean age of the participants was 20.09 ± 6.11, including 59% male, and the mean intraocular pressure (IOP) before the surgery was 13.59 ± 2.85 mmHg. Peripapillary Retinal nerve fiber layer (ppRNFL) thickness and overall retinal thickness remained stable post-CCL. However, significant alterations were observed in macular vessel density, emphasizing regional variations in vascular response. For macular large vessel density (LVD), both superficial and deep vascular complex (SVC and DVC) demonstrated significant differences between before surgery and the 3 months post-surgery follow-up (p < 0.001 and p = 0.002, respectively). Optic nerve head markers demonstrated relative stability, except for changes in avascular complex density, which was 49.2 ± 2.2% before the surgery and decrease to 47.6 ± 1.7% three months after the operation (P-value = 0.005).

CONCLUSION

While CCL appears to maintain the integrity of certain ocular structures, alterations in macular perfusion post-CCL suggest potential effects on retinal blood supply. Long-term monitoring is crucial to understand the implications of these changes, particularly in the context of conditions such as diabetes.

Evaluation of dynamic corneal response parameters and the biomechanical E-staging after Intacs® SK implantation in keratoconus

PURPOSE

This retrospective longitudinal study evaluated the biomechanical E-staging in KC corneas before and after intracorneal ring segment (ICRS) implantation (Intacs® SK, Addition Technology, Illinois, United States).

METHODS

Biomechanical E-staging for ectatic corneal diseases was applied retrospectively on 49 KC corneas of 41 patients who underwent ICRS implantation. The main outcome parameters included the Corvis Biomechanical Factor (CBiF, the linearized Corvis Biomechanical Index and the biomechanical parameters included), the resulting biomechanical E-staging, the stress-strain index, thinnest corneal thickness (TCT), maximal anterior keratometry (Kmax), and the anterior radius of curvature (ARC). They were evaluated at 1.9 ± 1.1 months preoperatively and postoperatively after 2.8 ± 0.7, 5.8 ± 1.0, and 10.6 ± 2.3 months.

RESULTS

The CBiF decreased (4.9 ± 0.5 | 4.7 ± 0.5, P = 0.0013), and the E-staging increased significantly (2.8 ± 0.8 | 3.1 ± 0.9, P = 0.0012, paired t-test) from preoperatively to the first postoperative follow-up. The difference remained significant after 6 months; however, there was no more difference after 11 months. TCT was stable, whereas Kmax and ARC significantly decreased after ICRS implantation (TCT: 464 ± 49, 470 ± 51, 467 ± 38, 461 ± 48; Kmax: 56.3 ± 4.5, 54.7 ± 4.5, 54.2 ± 4.8, 54.1 ± 4.3; ARC: 51.5 ± 3.4, 48.3 ± 3.8, 48.6 ± 3.0, 48.6 ± 3.2 preoperatively and 3, 6, and 11 months postoperatively, respectively). Besides Kmax and ARC, Ambrósio's relational thickness to the horizontal profile (ARTh) was the only parameter that was significantly lower than preoperatively at any follow-up (P ≤ 0.0024, Wilcoxon matched-pairs test).

CONCLUSION

Intacs® SK implantation results in an increasing biomechanical E-staging in the first postoperative months with stabilization near preoperative values after 1 year. Significantly lower ARTh values at any follow-up document the ICRS effect and contribute to a slightly higher postoperative biomechanical E-staging value.

Evaluation of the results of contact lens assisted corneal cross-linking treatment in keratoconus patients with thin corneas

PURPOSE

We aimed to compare the efficacy and safety of accelerated contact lens-assisted cross-linking (CA-CXL) with Lotrafilcon B and Comfilcon A lenses in keratoconus (KC) patients with thin corneas.

STUDY DESIGN

Retrospective, single-center study.

MATERIALS AND METHODS

We retrospectively included 51 eyes of 39 KC patients with corneal thickness <400µm after epithelial scraping (Epi-off), who underwent accelerated CA-CXL treatment with Lotrafilcon B (n=20) and Comfilcon A (n=31). Uncorrected and corrected distance visual acuity (UDVA and CDVA), manifest refraction values, corneal topographic data and endothelial cell density were recorded at preoperative and postoperative 1st, 3rd and 6th month controls.

RESULTS

CDVA in the Comfilcon A group was higher than CDVA before surgery at 6 months postoperatively (p<0.001). When the two lenses were compared, CDVA was found to be significantly higher in the Lotrafilcon B group in the preoperative, postoperative 1st month and 3rd month values, but there was no significant difference between the postoperative 6th month values (p=0.028, p=0.018, p=0.044, p=0.181, respectively). The maximum keratometry (Kmax) value at the 6th month after surgery in the Comfilcon A group was significantly lower than in the Lotrafilcon B group (p=0,009). There was no significant difference between the endothelial cell density values between the groups (p=0.623, p=0.609, p=0.794, p=0.458, respectively). There was no significant difference between the progression, regression, and stability rates of the two groups (p=0.714).

CONCLUSIONS

Accelerated CA-CXL with Lotrafilcon B and Comfilcon A silicone hydrogel lenses is a safe and effective method to stop progression in patients with thin corneas.

Comparison of refractive surgeries (SMILE, LASIK, and PRK) with and without corneal crosslinking: systematic review and meta-analysis

Corneal crosslinking (CXL) is used for treating keratoconus and post-laser in situ keratomileusis ectasia. However, refractive surgery is not usually performed with prophylactic CXL. Therefore, we performed a meta-analysis comparing outcomes of refractive surgeries with vs without prophylactic CXL. We systematically searched databases for studies comparing refractive surgeries for myopic correction with vs without prophylactic corneal crosslinking. Review Manager 5.4.1 was used to perform statistical analysis. We included 2820 eyes from 28 studies. Compared with refractive surgery alone, surgery with prophylactic CXL resulted in decreased central corneal thickness, corrected distance visual acuity logMAR, and safety and efficacy indices. There were no significant differences in postoperative uncorrected distance visual acuity of 20/20 or better at ≥12 months and other visual outcomes among both groups. More randomized controlled trials with standard crosslinking protocols are needed to analyze the prophylactic use of crosslinking with refractive surgeries.

Comparative evaluation of biomechanical changes and aberration profile following accelerated collagen cross-linking using hypo-osmolar and iso-osmolar riboflavin: A prospective study

PURPOSE

To compare the changes encountered in corneal biomechanics and aberration profile following accelerated corneal collagen cross-linking (CXL) using hypo-osmolar and iso-osmolar riboflavin in corneal thicknesses of <400 and >400 microns, respectively.

METHODS

This is a prospective, interventional, comparative study involving 100 eyes of 75 patients with progressive keratoconus. Eyes were divided into two groups based on corneal thickness: group 1 included eyes with a corneal thickness of <400 microns who underwent hypo-osmolar CXL, and group 2 included eyes with a corneal thickness of >400 microns who underwent iso-osmolar CXL. Corneal biomechanical and aberration profiles were evaluated and compared between groups.

RESULTS

In group 1, all higher-order aberrations (HOA) except secondary astigmatism significantly decreased from baseline; however, in group 2, only coma and trefoil decreased. The corneal resistance factor and corneal hysteresis significantly improved in both groups, which was significantly greater in group 2 than in group 1. The change in inverse radius, deformation amplitude, and tomographic biomechanical index was significantly improved in group 2 as compared to group 1.

CONCLUSION

Improvement in corrected distance visual acuity and decrease in HOA were significantly better in the hypo-osmolar CXL group; however, the improvement in biomechanical strength of the cornea was significantly better in the iso-osmolar group.

Comparison of keratoplasty outcomes at the scar versus edema stages of keratoconus

PURPOSE

To assess the outcomes of deep anterior lamellar keratoplasty or penetrating keratoplasty at the scar and the edema stages.

METHODS

Forty-five patients (45 eyes) with keratoconus scar stage (scar group, n=26; penetrating keratoplasty a subgroup, n=7; deep anterior lamellar keratoplasty b subgroup, n=19) and keratoconus edema stage (edema group, n=19; penetrating keratoplasty c subgroup, n=12; deep anterior lamellar keratoplasty d group, n=7) who received penetrating keratoplasty or deep anterior lamellar keratoplasty from 2000 to 2022 were retrospectively studied. At 1, 6, and 12 months after surgery, the best-corrected visual acuity, astigmatism, spherical equivalent, corneal endothelial cell density, and complications were analyzed.

RESULTS

The best-corrected visual acuity and average corneal endothelial cell loss rate were not significantly different between the scar and edema groups (p>0.05). At 6 and 12 months after surgery, the astigmatism and spherical equivalent in the scar group were significantly lower than those in the edema group (p<0.05). The spherical equivalent of the deep anterior lamellar keratoplasty b subgroup was lower than that of the penetrating keratoplasty a subgroup in the scar group 6 months after surgery (p<0.05). In the edema group, there was no significant difference in spherical equivalent between subgroups (p>0.05). There were no significant differences in best-corrected visual acuity and astigmatism between subgroups within the two groups (p>0.05). In comparison to the scar group, the edema group experienced more complications. According to a survival analysis, there was no statistically significant difference between the scar group and the edema group regarding the progression of vision.

CONCLUSIONS

In terms of the outcomes and prognosis for vision after keratoplasty with edema stage and scar stage, deep anterior lamellar keratoplasty may be as effective as penetrating keratoplasty.

Computational analysis of retinal image quality with different contact lens designs in keratoconus

PURPOSE

To determine 1) the relative differences in optical quality of keratoconic eyes fitted with four routinely used CL designs and 2) the Zernike coefficients in the residual wavefront aberration map that may be responsible for differences in the optical quality of keratoconic eyes fitted with these CLs.

METHODS

Wavefront aberrations over a 3-mm pupil diameter were measured without and with Kerasoft IC®, Rose K2®, conventional spherical Rigid Gas Permeable (RGP), and Scleral CLs in 15 mild to moderate keratoconic eyes (20 - 28 years) and under unaided viewing in 10 age-similar non-contact lens wearing controls. The resultant through-focus curves constructed for the logarithm of Neural Sharpness (logNS) Image Quality (IQ) metric were quantified in terms of peak value, best focus, and depth of focus. Sensitivity analyses determined the impact of the residual Zernike coefficients of keratoconic eyes fitted with CLs on the IQ of controls at emmetropic refraction.

RESULTS

The peak IQ and depth of focus were similar with Rose K2®, conventional RGP, and Scleral CLs (p > 0.05, for all) but significantly better than Kerasoft IC® CLs (p < 0.01 for all). Best focus was similar across all four CLs (p > 0.2 for all). However, the IQ parameters of all the lenses remained significantly poorer than the controls (p < 0.01, for all). The IQ of the controls dropped to keratoconic levels with induced residual lower-order Zernike terms and 3rd-order coma across all lenses in the sensitivity analysis (p < 0.001).

CONCLUSIONS

IQ of keratoconic eyes remain suboptimal with routinely dispensed CL designs, largely due to residual lower-order aberrations and coma, all relative to the controls. The performance drop appears greater for the Kerasoft IC® CL relative to the other CL designs. These results may provide the optical basis for psychophysical spatial visual performance reported earlier across these four CL designs for keratoconus.

Outcomes After Corneal Crosslinking for Keratoconus in Children and Young Adults

PURPOSE

The aim of this study was to assess the effect of corneal crosslinking on vision and keratometry in children and young adults with progressive keratoconus.

METHODS

A retrospective medical records review of patients aged 22 years or younger with keratoconus who underwent corneal crosslinking between January 2013 and November 2019 at Byers Eye Institute at Stanford University was conducted. Outcome measures included logarithm of the Minimum Angle of Resolution corrected distance visual acuity (CDVA); keratometry, including maximum keratometry (Kmax); pachymetry; and total wavefront aberration. Measurements were taken at baseline and at 12 and 24 months postoperatively.

RESULTS

Fifty-seven eyes of 49 patients aged 12 to 22 years were assessed. The mean preoperative CDVA was logarithm of the Minimum Angle of Resolution 0.38 ± 0.32 (20/48), with a mean postoperative CDVA of 0.29 ± 0.31 (20/39) and 0.31 ± 0.31 (20/41) at 12 and 24 months postoperatively, respectively. Compared with preoperative mean Kmax, there was an improvement of -0.8 diopters (D) to a mean postoperative Kmax of 59.1 ± 9.1 D at 12 months and -1.3 D to 59.7 ± 8.8 D at 24 months. Subanalysis excluding the second eye of patients who underwent bilateral crosslinking showed similar results. Linear mixed modeling showed significant improvement in Kmax at both 12 and 24 months postoperatively. Minimum central corneal thickness initially decreased but stabilized at 24 months after crosslinking. Total wavefront aberration remained stable.

CONCLUSIONS

Corneal crosslinking stabilizes, and in some cases improves, visual and corneal parameters in pediatric and young adult patients with keratoconus. The procedure is safe and well-tolerated and may prevent keratoconus progression in young patients.

Clinical evaluation of flat peripheral curve design with aspherical-curve and multi-curve hard contact lenses for keratoconus

Aspherical- and multi-curve rigid gas-permeable hard contact lenses (HCLs) have a flattened curve in the peripheral zone and are mostly used for patients with keratoconus who cannot wear glasses, soft contact lenses, or spherical HCLs. In this retrospective study, a total of 95 eyes of 77 patients who used aspherical- or multi-curve HCLs (mean age: 40.0 ± 11.0 years) were evaluated. This study examined the types of aspherical- and multi-curve HCLs, best-corrected visual acuity (BCVA) values before and after wearing HCLs, the association with the Amsler-Krumeich classification, duration of wear, corneal/conjunctival disorder, and the frequency of changing HCLs. There were 78 eyes that used aspherical-curve HCLs and 17 that used multi-curve HCLs. BCVA significantly improved from 0.42 logMAR to 0.06 logMAR after wearing either form of HCL. The Amsler-Krumeich classification showed that aspherical-curve HCLs were commonly used for patients with stage 2 keratoconus, and multi-curve HCLs were commonly used for stage 4 patients. The BCVA values were worse when the disease stage was more severe (stages 3 and 4) regardless of HCL type. The mean base curve of the lenses was steeper in multi-curve HCLs than in aspherical-curve HCLs. The more severe the disease stage, the steeper the base curve in both aspherical- and multi-curve HCLs. The duration of wear significantly improved from 2.1 h to 10.2 h, and corneal/conjunctival disorder similarly improved. The mean frequency of changing HCL types was 1.1 times. This study suggests that a flat peripheral curve design with aspherical- and multi-curve HCLs is useful for patients with keratoconus.

Predicting factors for the efficacy of cross-linking for keratoconus

Purpose

To evaluate predictors for success in corneal crosslinking (CXL) for keratoconus in a large cohort and extended follow-up.

Design

A retrospective study based on a prospectively built database.

Methods

Participants underwent CXL for keratoconus from 2007 to 2018. Statistical analysis was performed for patients with at least 1-year follow-up. We analyzed effects of CXL type (Epithelium-on or Epithelium-off and Accelerated (9mW/cm2@10min) or Standard (3mW/cm2@30min)) and pre-operative factors including age, gender, baseline LogMAR visual acuity (LogMARpre), maximal corneal power (Kmaxpre), pachymetry, refractive and topographic cylinders, spherical equivalent (SEpre), mean corneal power (MeanK) and follow-up time on outcome measures. The outcome measures were the final change of Kmax (Delta Kmax) and the final change in LogMAR visual acuity (Delta LogMAR). A more negative Delta Kmax or Delta LogMAR represents a favorable effect of crosslinking.

Results

517 eyes had Kmax results, and 385 eyes had LogMAR results with more than one year follow-up. These eyes were included in the study. The mean follow-up time was 2.29 years. Mean Kmax decreased from 54.07±5.99 diopters to 52.84±5.66 diopters (p<0.001), and Mean LogMAR decreased from 0.28±0.20 to 0.25±0.21 (p<0.001). Non-accelerated epithelium-off CXL resulted in greater flattening of Kmax when compared with other protocols. Visual acuity improvement was similar when comparing different CXL protocols. Multivariate analysis showed four factors associated with negative Delta Kmax: high Kmaxpre, high SEpre, high MeanKpre, and non-accelerated procedure. Multivariate analysis showed three factors associated with negative Delta LogMAR: high LogMARpre, high SEpre, and Low MeanKpre. After excluding corneas with Kmaxpre >65 D or Pachymetry<400 microns, multivariate analysis showed that high Kmaxpre, high SEpre, and non-accelerated CXL were associated with negative Delta Kmax while high LogMARpre and high SEpre were associated with negative Delta LogMAR.

Conclusion

CXL for keratoconus is a highly effective treatment, as evident by its effects on the outcome measures: Delta Kmax and Delta LogMAR. CXL was more successful in eyes with high Kmaxpre, high SEpre, and high LogMARpre, which express disease severity. The non-accelerated epithelium-off protocol was associated with greater flattening of corneal curvature but did not show a better effect on visual acuity as compared to the other CXL protocols.

One-Year Front Versus Central and Paracentral Corneal Changes After Bowman Layer Transplantation for Keratoconus

PURPOSE

To report the front corneal versus central and paracentral corneal changes after Bowman layer transplantation for keratoconus in a tertiary hospital in the United Kingdom.

METHODS

Five eyes of 5 patients receiving Bowman layer transplant for advanced keratoconus in Royal Gwent Hospital (Newport, United Kingdom) were included. Preoperative and postoperative visual acuity; Kmax; Kmean, and corneal cylinder in the front cornea, 4.5 mm central, and 6 mm central; and corneal thickness were analyzed.

RESULTS

Corneal flattening and reduction in corneal astigmatism was observed, more marked in the central and paracentral zone, allowing for improvement in best-corrected visual acuity with the aid of visual correction in 4 eyes.

CONCLUSIONS

These results support previous data reporting Bowman layer transplantation as a useful strategy in the treatment of advanced keratoconus and suggest greater attention may be focused on central or paracentral corneal changes.

Effect of Previous Crosslinking on Intraoperative and Postoperative Outcomes and Complication Rates of Big-Bubble Deep Anterior Lamellar Keratoplasty for Keratoconus: A Comparative Study

PURPOSE

To compare surgical outcomes and intraoperative and postoperative complications of big-bubble deep anterior lamellar keratoplasty (DALK) in patients with and without a history of previous corneal collagen crosslinking (CXL) for keratoconus.

METHODS

Patients with keratoconus who underwent DALK surgery with big-bubble technique between January 2013 and January 2018 were retrospectively reviewed. Operative findings, intraoperative and postoperative complications, and visual and refractive outcomes were recorded. Patients were divided into 2 groups: with previous CXL (CXL-DALK group: 27 eyes) and without previous CXL (DALK group: 50 eyes). All parameters were compared between groups.

RESULTS

Big bubble was successfully achieved in 24 eyes (88.9%) in the CXL-DALK group and in 45 eyes (90.0%) in the DALK group (P = 0.87). Type 1 bubble was obtained in 22 eyes (91.7%) in the CXL-DALK group and in 42 eyes (93.3%) in the DALK group (P = 0.79). Intraoperative microperforation occurred in 3 eyes (11.1%) in the CXL-DALK group and in 5 eyes (10.0%) in the DALK group (P = 1). Visual and refractive outcomes were similar between groups. The mean endothelial cell loss rates were 5.7% ± 2.3 at 1 year and 10.2 ± 3.1 at 2 years in the CXL-DALK group and 6.4% ± 4.7 at 1 year and 10.9% ± 5.4 at 2 years in the DALK group. Postoperatively, persistent epithelial defect was the most common complication in both groups, and postoperative complication rates were similar between groups.

CONCLUSIONS

Our results have shown that previous CXL treatment does not influence the success of bubble formation and does not increase intraoperative or postoperative complication rates of DALK surgery for keratoconus. The improvement in visual acuity and refractive errors and endothelial cell loss rates were similar between CXL treated and untreated eyes after 2 years of follow-up.

The Aotearoa Research Into Keratoconus Study: Geographic Distribution, Demographics, and Clinical Characteristics of Keratoconus in New Zealand

PURPOSE

To investigate the epidemiologic, demographic, and basic clinical characteristics of individuals with keratoconus managed by optometrists in New Zealand (NZ)/Aotearoa.

METHODS

A prospective, longitudinal, nationwide, survey protocol was completed for every patient with keratoconus who underwent a consultation with participating optometrists in a 2-year period. Data for each patient included date of birth, sex, self-reported ethnicity, new or previous diagnosis, uncorrected (UCVA) and best-corrected visual acuity (BCVA), type of refractive correction required to obtain BCVA and keratometric readings obtained using keratometry or computerized topography.

RESULTS

One thousand eight hundred sixty-nine cases were identified, with a mean age of 41.0 ± 15.7 years, 56.4% being men, and 87.3% with previous diagnosis. The distribution of cases was skewed toward Auckland (41.6%), Waikato (21.3%), Wellington (16.8%), and Bay of Plenty (13.3%). Self-reported ethnicities were predominantly NZ European (54.4%), Māori (24.7%), and Pacific Peoples (15.5%), disproportionate to the general population profile (74.0%, 14.9%, and 7.4% respectively). Most eyes (64.3%) were managed with rigid contact lenses (corneal lens in 34.2%). The mean K-mean was 49.0 ± 5.7 D. The mean UCVA was 6/42 and BCVA was 6/9. Māori and Pacific Peoples had both the highest K-mean and proportions of eyes graded stage IV on the Amsler-Krumeich scale.

CONCLUSIONS

The results indicate that keratoconus is relatively common in NZ with at least 1869 patients managed by optometrists in 2 years. Most eyes had mild to moderate disease; however, Māori and Pacific Peoples seem to have greater disease severity. An ethnic predilection is apparent, with Māori and Pacific Peoples overrepresented relative to their population proportions, reinforcing a long-held clinical suspicion.

Bowman Layer Onlay Grafting: Proof-of-Concept of a New Technique to Flatten Corneal Curvature and Reduce Progression in Keratoconus

PURPOSE

The aim of this study was to describe a new surgical technique for flattening the corneal curvature and to reduce progression in eyes with advanced progressive keratoconus (KC) by using Bowman layer (BL) onlay grafting and to report on the preliminary outcomes of this procedure.

METHODS

In this prospective interventional case series, 5 patients with advanced progressive KC underwent BL onlay grafting. After removal of the epithelium, a BL graft was placed and "stretched" onto the stroma, and a bandage lens was placed to cover the BL graft. In 1 case, BL onlay grafting could be performed immediately after ultraviolet corneal crosslinking; all other eyes were ineligible for ultraviolet corneal crosslinking. Best spectacle- and/or best contact lens-corrected visual acuity, refraction, biomicroscopy, corneal tomography, anterior segment optical coherence tomography, and complications were recorded at 1 week and at 1, 3, 6, 9, and 12 to 15 months postoperatively.

RESULTS

All 5 surgeries could be performed successfully. Average maximum keratometry went from 75 diopters (D) preoperatively to 70 D at 1 year postoperatively. All eyes showed a completely reepithelialized and a well-integrated graft. Best spectacle-corrected visual acuity improved at least 2 Snellen lines (or more) in 3 of 5 cases and best contact lens-corrected visual acuity remained stable, improving by 3 Snellen lines in case 1 at 15 months postoperatively. Satisfaction was high, and all eyes again had full contact lens tolerance.

CONCLUSIONS

BL onlay grafting may be a feasible surgical technique, providing up to -5 D of corneal flattening in eyes with advanced KC.

Comparative Efficacy and Safety of Standard Versus Accelerated Corneal Crosslinking for Keratoconus: 1-Year Outcomes From the Save Sight Keratoconus Registry Study

PURPOSE

The aim of this study was to compare the efficacy and safety of standard [Ultraviolet (UV) light power: 3 mW/cm2, duration: 30 minutes] versus accelerated (UV power: 9 mW/cm2, duration: 10 minutes) corneal crosslinking (CXL) for stabilizing keratoconus.

METHODS

A total of 684 eyes (555 patients; mean age ± SD, 25.0 ± 7.9 years; women, 30.6%) from 24 international sites with epithelium-off CXL for keratoconus had follow-up data at 1-year and met the inclusion criteria. Two hundred sixty-six eyes (228 patients) had undergone standard CXL, and 418 eyes (327 patients) had undergone accelerated CXL. The outcome measures included changes in visual acuity, keratometry, minimum corneal thickness, and frequency of adverse events. The outcomes were compared using mixed-effects regression models adjusted for age, sex, visual acuity, keratometry, pachymetry, doctor, practice, and eye laterality.

RESULTS

The adjusted mean changes (95% confidence interval) in outcomes were similar in standard and accelerated CXL in visual acuity [6.5 (2.0, 11.1) versus 5.5 (0.4, 10.6) logMAR letters, respectively], Kmax [-0.9 (-1.4, -0.3) D versus -1.2 (-1.9, -0.4) D, respectively], K2 [-0.4 (-0.9, 0.2) D versus -0.4 (-1.1, 0.3), D respectively], or minimum corneal thickness [-13.3 (-20.3, -6.3) μm versus -16.6 (-24.5, -8.6) μm, respectively] (all P > 0.05). The frequency of adverse events at the 12-month visit was also similar between the CXL groups (standard, 8.3% vs. accelerated, 5.5%; P = 0.21).

CONCLUSIONS

This real-world observational study found that both standard and accelerated CXL were similarly safe and effective in stabilizing keratoconus at 1-year postsurgery in the real-world setting. The findings support the adoption of accelerated CXL for time and convenience.

Optical Quality in Keratoconus Is Associated With Corneal Biomechanics

PURPOSE

To evaluate the correlations between corneal biomechanical indices from dynamic Scheimpflug assessment and optical quality assessed as higher-order aberrations (HOAs) using a Hartmann-Shack ocular wavefront sensor in patients with keratoconus (KC).

METHODS

In this prospective, observational case series, the eyes with KC or KC suspect (KCS) from Osaka University Hospital, Osaka, Japan, were analyzed. Corneal biomechanical assessment was performed using Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany), and ocular wavefront aberrations were measured using the KR-1W (Topcon Corp, Tokyo, Japan). Correlations between the biomechanical indices and ocular HOAs were assessed. Corneal biomechanical indices included the deformation amplitude ratio within 2 mm, integrated radius, stiffness parameter at the first applanation, and the linear Corvis Biomechanical Index. Wavefront data of the central 4-mm region were expanded up to the sixth order of Zernike polynomials. The magnitudes of trefoil, coma, tetrafoil, secondary astigmatism, and spherical aberration were calculated by Zernike vector analysis and then used as ocular HOA parameters along with total HOAs.

RESULTS

Thirty-four KC eyes and 37 KCS eyes were included. KC eyes showed significant correlations between ocular HOAs and biomechanics, whereas there were few significant correlations in KCS eyes. In KC eyes, deformation amplitude ratio within 2 mm, integrated radius, and Corvis Biomechanical Index beta showed stronger correlations with coma among the wavefront parameters.

CONCLUSIONS

Corneal biomechanical indices correlated with ocular HOAs in patients with KC. In particular, there was a strong association with the increase in coma caused by inferosuperior asymmetry of the shape of the cornea in patients with KC.

Comparison of Corneal Biomechanical Properties and Corneal Tomography Between Customized and Accelerated Corneal Crosslinking in Eyes with Keratoconus

PURPOSE

To compare the changes in corneal biomechanical properties and corneal tomography between transepithelial customized corneal crosslinking (C-CXL) and epithelium-off accelerated corneal crosslinking (A-CXL) in eyes with keratoconus.

METHODS

Twenty eyes in 20 consecutive patients who underwent C-CXL (C-CXL group) and 20 eyes in 20 patients who underwent A-CXL (A-CXL group) were included in this retrospective comparative study. The corneal biomechanical properties were analyzed using a Scheimpflug-based tonometer, and all corneas were examined by anterior segment optical coherence tomography (AS-OCT) before and 3 months after surgery. The corneal biomechanical parameters analyzed were the maximum inverse radius, deformation amplitude (DA) ratio max (2 mm), stiffness parameter at applanation 1, and integrated radius. The AS-OCT parameters analyzed included average keratometry, corneal astigmatism, maximum keratometry reading (Kmax), higher-order irregularity, and asymmetry.

RESULTS

In the C-CXL group, there were significant improvements in biomechanical parameters, including the maximum inverse radius, the DA ratio max (2 mm), and the integrated radius after surgery (P = 0.037, P = 0.002, and P = 0.003, respectively). In the C-CXL group, there was a significant decrease in the Kmax, higher-order irregularity, and asymmetry components (P = 0.014, P = 0.008, and P = 0.016, respectively). The biomechanical properties and AS-OCT parameters did not change significantly in the A-CXL group after surgery. According to multiple regression analyses, C-CXL had a greater effect than A-CXL in improving the maximum inverse radius, DA ratio max (2 mm), integrated radius, Kmax, asymmetry component, and higher-order irregularity component.

CONCLUSIONS

C-CXL might improve the biomechanical properties and irregular shape of the cornea from the early postoperative period to a greater extent than A-CXL.

Contrast sensitivity and higher-order aberrations in Keratoconus subjects

This study analyzes the relationship between contrast-sensitivity and higher-order aberrations (HOA) in mild and subclinical-keratoconus in subjects with good visual-acuity (VA). Keratoconus group (including subclinical-keratoconus) and controls underwent autokeratometry, corneal-tomography, autorefraction and HOA measurement. Contrast-sensitivity was tested using a psychophysical two-alternative forced-choice Gabor patches in three blocks (6, 9, 12 cycles/deg). Controls were compared to the keratoconus group and to a keratoconus subgroup with VA of 0.00 LogMar group ("keratoconus-0.00VA"). Spearman correlation tested association between HOA and contrast-sensitivity. Twenty-two keratoconus subjects (38 eyes: 28 keratoconus, 10 subclinical-keratoconus, 20 keratoconus-0.00VA) and 35 controls were included. There was a significant difference between control and keratoconus, and between control and keratoconus-0.00VA, for keratometry, cylinder, thinnest and central corneal thickness (p < 0.001). Controls showed lower HOA and higher contrast-sensitivity for all spatial-frequencies (p < 0.001). Most HOA were negatively correlated with contrast-sensitivity for all spatial-frequencies for keratoconus group and for 9 and 12 cycles/deg for keratoconus-0.00VA. Keratoconus subjects with good VA showed reduction in contrast-sensitivity and increased HOAs compared to controls. HOA and contrast-sensitivity are inversely correlated in subjects with mild keratoconus despite good VA. This suggests that the main mechanism underlying the decreased vision quality in keratoconus is the increase of HOA.

In Vivo Confocal Microscopy of Stromal Lenticule Addition Keratoplasty for Advanced Keratoconus

PURPOSE

To investigate the in vivo corneal microscopic changes after femtosecond laser-assisted stromal lenticule addition keratoplasty in keratoconus by means of in vivo confocal microscopy.

METHODS

Patients affected by advanced keratoconus were included in the study. Negative meniscus-shaped stromal lenticules, produced with a femtosecond laser (VisuMax; Carl Zeiss Meditec) from eye bank corneas were transplanted into a stromal pocket dissected in the recipient cornea at a depth of 120 µm. In vivo confocal microscopy was performed during the 12-month follow-up to investigate changes of the corneal and lenticule structure.

RESULTS

Ten patients were enrolled in the study. No changes of the dendritic cell population were documented during the follow-up period. Mild edema and stromal keratocyte activation gradually decreased during the first month. Subbasal nerve density returned to preoperative values after 6 months. Donor-recipient interfaces appeared hyperreflective but gradually improved over time with significantly reduced reflectivity after 3 months. No evidence of stromal inflammatory cell migration or matrix opacification was observed. Endothelial and keratocyte density remained stable over time. A variable degree of stromal radially distributed folds, not visible on biomicroscopy, was observed in the lenticule and in the posterior recipient stroma.

CONCLUSIONS

Stromal lenticule addition keratoplasty produces transitory nerve plexus density reduction and minor inflammatory reaction that rapidly decreases during the first month. Donor-recipient interface reflectivity is comparable to a femtosecond laser refractive procedure with no sign of stromal opacification or stromal rejection in 1 year of follow-up. [J Refract Surg. 2020;36(8):544-550.].

Bilateral Keratoconus Progression: Immediate Versus Delayed Sequential Bilateral Corneal Cross-linking

PURPOSE

To compare immediate sequential bilateral corneal cross-linking (CXL), wherein both eyes are treated on the same day, to delayed sequential bilateral CXL, where each eye is treated on different days for bilateral progressive keratoconus.

METHODS

This was a retrospective case note review of all patients who underwent sequential CXL or delayed CXL for keratoconus at Royal Liverpool University Hospital, United Kingdom. Parameters assessed were the change in maximum keratometry and minimum central corneal thickness on corneal tomography scan, corrected distance visual acuity, and cost estimates of treatment.

RESULTS

A total of 38 patients (31 men and 7 women) with keratoconus with a mean age of 25.3 ± 7.0 years were included. Twenty patients received sequential CXL and 18 received delayed CXL treatment. In both the sequential CXL and delayed CXL groups, the treated eye(s) showed no evidence of progression after the corneal CXL treatment at last follow-up visit after 358 ± 158 days for sequential CXL and 451 ± 205 days for delayed CXL. There were no complications from the treatment in either group. In the delayed CXL group, the mean time interval between the two CXL procedures was 146 ± 129 days. Five of 18 patients (27%) showed progression of keratoconus in their second eye during the waiting time. Economical evaluation showed that four visits were saved for each sequential CXL treatment compared to delayed CXL.

CONCLUSIONS

Delayed CXL carries a risk of progression in the second eye and is associated with a higher economic burden. [J Refract Surg. 2020;36(8):552-556.].

Corneal Stromal Regeneration Therapy for Advanced Keratoconus: Long-term Outcomes at 3 Years

PURPOSE

To report the 3-year clinical outcomes of corneal stromal cell therapy consisting of the intrastromal implantation with autologous adipose-derived adult stem cells (ADASCs), and decellularized or ADASC-recellularized human donor corneal laminas in advanced keratoconus.

METHODS

Fourteen patients were enrolled in 3 experimental groups. Group 1 (G-1) patients underwent implantation of ADASCs alone (3 × 10⁶ cells/1 mL) (n = 5). Group 2 (G-2) patients received a 120-μm decellularized corneal stroma lamina (n = 5). Group 3 (G-3) patients received a 120-μm lamina recellularized with ADASCs (1 × 10⁶ cells/1 mL) (n = 4). ADASCs were obtained by elective liposuction. Implantation was performed into a femtosecond pocket under topical anesthesia.

RESULTS

At 3 years, a significant improvement of 1 to 2 logMAR lines in uncorrected distance visual acuity was observed in all groups. A statistically significant decrease in corrected distance visual acuity was obtained in G-2 and G-3 (P < 0.001) when compared with that of G-1. Rigid contact lens distance visual acuity showed a statistically significant worsening in G-2 (P < 0.001) compared with that of G-1. A statistically significant increase in central corneal thickness was observed in G-2 (P = 0.012) and G-3 (P < 0.001); in the Scheimpflug corneal topography, the thinnest point was observed in G-2 (P = 0.007) and G-3 (P = 0.001) when compared with that of G-1.

CONCLUSIONS

Intrastromal implantation of ADASCs and decellularized or ADASC-recellularized human corneal stroma laminas did not have complications at 3 years. The technique showed a moderate improvement in (uncorrected distance visual acuity) and (corrected distance visual acuity) in advanced keratoconus.

Keratoplasty for Keratoconus in Young Patients: Demographics, Clinical Features, and Post-transplant Outcomes

PURPOSE

To examine pretransplant findings and outcomes of corneal transplants for keratoconus in children.

DESIGN

Retrospective cohort (national registry) study.

METHODS

Data on all patients aged 16 or younger (n = 170) who had a first transplant for keratoconus between 2003 and 2018 in all corneal transplant centers in the UK were compared to adult patients aged 17 and older (n = 7,191). The influence of demographic variables, pretransplant corneal findings, and transplant type on 2-year visual, rejection-free, and transplant survival outcomes was examined.

RESULTS

Children had poorer pretransplant visual acuity and higher rates of corneal vascularization and ocular surface disease than adults. However, 2-year post-transplant corrected visual acuity reached 20/20 or better in 35% of children compared to 28% of adults (P = .1). Transplant rejection and failure rates were 11% (P = .79) and 3% (P = .31), respectively, for children, which were comparable to rates for adults. Endothelial rejection was reported following penetrating keratoplasty (PK) in 13% of children (10% in adults). Irreversible rejection was not recorded for any transplant in a child. Despite a lack of difference in transplant outcomes, there was a significant age effect in the Cox regression model for transplant rejection, such that for every 5-year increase in age there was a 6% reduction in the hazard of rejection. Transplant survival following anterior lamellar keratoplasty and PK in children was similar.

CONCLUSIONS

Young keratoconus patients have excellent transplant outcomes and visual results comparable to adults. Overall, the hazard of rejection was found to decrease with advancing age. However, in this large cohort of young patients with keratoconus and poor vision, there is no evidence of outcome advantage in delaying transplant until adult years.

Penetrating Keratoplasty Versus Deep Anterior Lamellar Keratoplasty in Children and Adolescents With Keratoconus

PURPOSE

To compare the outcomes of penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) for pediatric keratoconus.

DESIGN

Retrospective comparative interventional case series.

METHODS

This study included consecutive pediatric keratoconus cases (≤18 years of age) who received PK (n=45) or DALK (n=54) in 2 different time periods. Postoperative best spectacle-corrected visual acuity (BSCVA), refraction, and complications were compared between the study groups.

RESULTS

The mean follow-up was 83.3±46.1 and 63.3±45.6 months in the PK and DALK groups, respectively (P = .10). Postoperatively, BSCVA was 0.20±0.19 logMAR in the PK group and 0.26±0.19 logMAR in the DALK group (P = .11), with a BSCVA of ≥20/40 in 91.1% and 83.3% of eyes, respectively (P = .25). Two groups were comparable regarding postoperative refractive outcomes. Graft epitheliopathy and suture-associated complications were more commonly encountered after DALK, which was attributable to the effect of low-quality grafts on the clinical outcomes of DALK. Ten PK eyes (22.2%) and 9 DALK eyes (16.7%) experienced at least 1 episode of graft rejection within 5 years of corneal transplantation (P = .49). Rejection was reversible in 93.1% and 100% of episodes in the PK and DALK groups, respectively (P = .63). At the postoperative year 5, 95.6% of grafts in the PK group and 98.2% in the DALK group remained clear (P = .45).

CONCLUSION

No significant difference was observed in the outcomes between PK and DALK in pediatric keratoconus. Low-quality donor tissues in DALK increased the incidence of graft epithelial problems and suture-related complications as compared to PK.

Between eye asymmetry in keratoconus in an Indian population

PURPOSE

The purpose of this study was to assess the clinical as well as topographic asymmetry between the eyes in keratoconus.

METHODS

Clinical examination including retinoscopy, distant direct ophthalmoscopy, manual keratometry (Bausch & Lomb), slitlamp biomicroscopy and topography (Nidek ARK10000) was carried out on 44 eyes of 22 subjects. At least four high quality topographical images, which were within 0.25 D of one another as measured by simulated keratometry (SimK), were obtained for each eye. Of these, the one with the best alignment and at least six digitised rings was selected for analysis.

RESULTS

The visual acuity (logMAR), and spherical and cylindrical errors showed marked asymmetry with means of 0.3 +/- 0.3 (SD),-5.2 +/- 6.2 D,-3.1 +/- 2.5 D in the better eyes and 0.5 +/- 0.3,-9.8 +/- 8.5 D,-5.0 +/- 2.5 D in the worse eyes (p = 0.01, 0.05, 0.01, respectively). Scissoring retinoscopy reflex, oil droplet sign, Munson's sign, Vogt's striae, scarring and keratometry readings were significantly greater in the more affected eyes. The inferior-superior steepening, central corneal power and apex power as deduced from topography were significantly greater in the more affected eyes with values of 20.3 +/- 15.7 D, 51.4 +/- 10.1 D, 56.7 +/- 11.0 D in the better eyes and 30.4 +/- 18.6 D, 60.1 +/- 10.9 D, 68.7 +/- 19.6 D in the worse eyes (p = 0.05, 0.01, 0.02).

CONCLUSION

Keratoconus is essentially a bilateral but asymmetric corneal degeneration. Seven of our patients had clinically unilateral keratoconus but on topography, based on KISA% index, six of the unaffected eyes were diagnosed as keratoconus though much milder than in the other eye.

Individualized Corneal Cross-linking With Riboflavin and UV-A in Ultrathin Corneas: The Sub400 Protocol

PURPOSE

To determine whether corneal cross-linking (CXL) with individualized fluence ("sub400 protocol") is able to stop keratoconus (KC) progression in ultrathin corneas with 12-month follow-up.

DESIGN

Retrospective, interventional case series.

METHODS

Thirty-nine eyes with progressive KC and corneal stromal thicknesses from 214 to 398 μm at the time of ultraviolet irradiation were enrolled. After epithelium removal, ultraviolet irradiation was performed at 3 mW/cm² with irradiation times individually adapted to stromal thickness. Pre- and postoperative examinations included corrected distance visual acuity (CDVA), refraction, Scheimpflug, and anterior segment optical coherence tomography imaging up to 12 months after CXL. Outcome measures were arrest of KC progression at 12 months postoperatively and stromal demarcation line (DL) depth.

RESULTS

Thirty-five eyes (90%) showed tomographical stability at 12 months after surgery. No eyes showed signs of endothelial decompensation. A significant correlation was found between DL depth and irradiation time (r = +0.448, P = .004) but not between DL depth and change in K_max (r = -0.215, P = .189). On average, there was a significant change (P < .05) in thinnest stromal thickness (-14.5 ± 21.7 μm), K_max (-2.06 ± 3.66 D) and densitometry (+2.00 ± 2.07 GSU). No significant changes were found in CDVA (P = .611), sphere (P = .077), or cylinder (P = .915).

CONCLUSIONS

The "sub400" individualized fluence CXL protocol standardizes the treatment in ultrathin corneas and halted KC progression with a success rate of 90% at 12 months. The sub400 protocol allows for the treatment of corneas as thin as 214 μm of corneal stroma, markedly extending the treatment range. The DL depth did not predict treatment outcome. Hence, the depth is unlikely related to the extent of CXL-induced corneal stiffening but rather to the extent of CXL-induced microstructural changes and wound healing.

Improvement In Visual Acuity Six Months After Penetrating Keratoplasty In Patients Of Keratoconus

BACKGROUND

Keratoconus (KC) is a bilateral, asymmetric, corneal disorder that is characterized by progressive thinning, steepening, and potential scarring. In the early stages of keratoconus treatment can be modulated with contact lenses but once it reaches to scarring, penetrating keratoplasty (PK) is the standard procedure of care. As there is not enough published data on penetrating keratoplasty in Pakistan and also early visual outcomes post keratoconus keratoplasty have not been established so this study would be beneficial for further research and opting keratoplasty as a procedure for management of advance keratoconus. To determine the frequency of improvement in the visual acuity six months after penetrating keratoplasty in patiens of Keratoconus.

METHODS

Sixty-five eyes of 65 patients fulfilling the inclusion criteria were taken from the Outdoor Clinic of Layton Rahmatulla Benevolent Trust Free Eye and Cancer Hospital. Informed consent was taken and socio-demographic data (name, age, gender, address and contact number) was also recorded. Examination included Visual Acuity with Snellen's Chart with assessment of light projection in patients with Visual Acuity hand movements or light perception. Slit lamp examination with Haag Streit BQ 900 Slit lamp for assessing the condition of cornea was done. Indirect ophthalmoscopy was performed using 90D lens for fundus examination. B-scan (ocular ultrasonography) with Alcon B-scan was done where fundus examination was not possible. Standard surgical procedure of Penetrating Keratoplasty was carried out on all patients. Visual Acuity was recorded on Day 7, 90 and 180 after the surgery.

RESULTS

Penetrating Keratoplasty is a safe and reliable procedure for improvement in visual acuity of patients with keratoconus and should be conducted on mass level to avoid blindness caused by keratoconus.

A Study On Efficacy Of Corneal Collagen Cross Linking In Progressive Keratoconus

BACKGROUND

Keratoconus is a progressive, noninflammatory, bilateral ectatic corneal disease, characterized by paraxial stromal thinning and weakening that leads to corneal surface distortion. The objective of this research was to determine the effectiveness and safety of collagen crosslinking in progressive keratoconus, with keratometry (Kmax) value of 50 diopters or above. It was a retrospective study, conducted at Bodla Eye Care (BEC) and Multan Medical and Dental College, Multan (MMDC) from May 2018 to November 2019.

METHODS

In this research 52 eyes were studied. The best-corrected visual acuity, uncorrected visual acuity, maximum keratometry, mean keratometry value, and thinnest corneal thickness before surgery and 12 months after Cross-linking were observed. A Galeili G6 by Zeimer ophthalmic system was used to measure the clinical parameters. Dresden protocol was followed in this study. A written ethical approval was obtained and research was conducted under the light of declaration of Helsinki.

RESULTS

The average logarithm of the minimum angle of resolution (logMAR) of the uncorrected visual acuity decreased from 0.66±0.41 D to 0.49±0.40 D (p=0.012), while the mean thinnest point thickness of the cornea decreased from 435.31 37.91 μm to 419.41±70.12 μm (p=0.004) after 12 months. The decreases in the mean logMAR of the BCVA, Kmax and Kmean values were not analytically important (p>0.05) at the 12-month follow-up 94.2% positive results were obtained.

CONCLUSION

Collagen cross-linking treatment was safe and maintained both the visual acuity and tomographic parameters at the one-year follow-up in eyes.

Iontophoresis Corneal Cross-linking With Enhanced Fluence and Pulsed UV-A Light: 3-Year Clinical Results

PURPOSE

To assess 3-year safety and efficacy of enhanced-fluence pulsed-light iontophoresis cross-linking (EF I-CXL) in patients with progressive keratoconus.

METHODS

This prospective interventional pilot study included 24 eyes of 20 patients, with a mean age of 23.9 years (range: 15 to 36 years). Iontophoresis with riboflavin solution was used for stromal imbibition. The treatment energy was optimized at 30% (7 J/cm²) and ultraviolet-A power set at 18 mW/cm² × 6.28 minutes of pulsed-light on-off exposure, with a total irradiation time of 12.56 minutes. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), corneal tomography, and corneal optical coherence tomography (OCT) at baseline and 1, 3, 6, 12, 24, and 3 years postoperatively were evaluated.

RESULTS

At 3 years, average UDVA decreased from 0.50 ± 0.10 to 0.36 ± 0.08 logMAR (P < .05), average maximum keratometry decreased from 52.94 ± 1.34 to 51.4 ± 1.49 diopters (D) (Delta: -1.40 ± 0.80 D; P < .05), average coma improved from 0.24 ± 0.05 to 0.12 ± 0.02 µm (P = .001), and symmetry index decreased from 4.22 ± 1.01 to 3.53 ± 0.90 D. Corneal OCT showed demarcation line detection at 285.8 ± 20.2 µm average depth in more than 80% at 1 month postoperatively.

CONCLUSIONS

The 3-year results of EF I-CXL showed satisfactory I-CXL functional outcomes, increasing the visibility and the depth of demarcation line closer to epithelium-off standard CXL. [J Refract Surg. 2020;36(5):286-292.].

Effect of penetration enhancer with novel corneal cross-linking using recombinant human decoron in porcine eyes

The aim of the study was to investigate the effectiveness of exogenous recombinant human decoron and an accompanying penetration-enhancing solution in stiffening ex-vivo porcine corneas both transepithelially and after de-epithelialization. Eight porcine paired eyes were treated transepithelially: one eye with a pre-treatment solution (Pre-Tx), penetration enhancing solution (PE), and decoron while the fellow eye was treated by the same protocol but without decoron. A second group included 4 de-epithelialized pairs treated identically. The final group included 4 de-epithelialized pairs with one eye treated with Pre-Tx, PE, and decoron while the fellow eye was treated without PE. Uniaxial tensile testing was used to compare the corneal stiffness between the different treatment conditions. Residual tissue underwent immunohistochemistry analysis to evaluate the depth of penetration of decoron into the corneal stroma. There was no stiffening effect exhibited among corneas treated transepithelially with decoron compared to control (P > 0.05) and poor stromal penetration was exhibited on tissue analysis. Among de-epithelialized corneas, there was a significant stiffening effect seen in those treated with decoron at 3%, 4%, 5%, & 6% strain (P < 0.05) compared to control. Among de-epithelialized corneas there was also a significant stiffening effect seen in those treated with the PE and decoron at 4%, 5%, & 6% strain (P < 0.05) with improved stromal penetration confirmed by immunohistochemistry, versus without PE. De-epithelialization is necessary for effective stromal penetration of decoron. Depth of penetration and subsequent corneal stiffening may be improved with a penetration enhancing solution. Compared to riboflavin, decoron requires shorter treatment time and spares UV light exposure.

Transient corneal ectasia after phacoemulsification in an eye with femtosecond intrastromal presbyopic treatment

We report a case of transient corneal ectasia developed after phacoemulsification in an eye previously treated with INTRACOR. There was a myopic refractive surprise after cataract surgery. Corneal tomography showed an increase in keratometry and elevation profile compared with preoperative examination. Soft contact lenses and intraocular pressure-lowering medications were prescribed as interim treatment. Clinical improvement was seen gradually, and the resolution of myopia and ectasia was achieved at 3 months. We believe that high intraocular pressure during phacoemulsification and the weakening effect of femtosecond intrastromal presbyopic treatment can be the culprits.

Cool Crosslinking: Riboflavin at 4°C for Pain Management After Crosslinking for Keratoconus Patients, A Randomized Clinical Trial

PURPOSE

To explore corneal cooling as a method of pain management in corneal-accelerated collagen cross-linking.

METHODS

This was a prospective and interventional randomized clinical trial registered in the National Institutes of Health Clinical Trials through the identifier NCT030760770. The research was conducted at the Institute of Ophthalmology "Conde de Valenciana." A total of 98 patients were randomly assigned to one of the following 2 groups: cold riboflavin (4°C) group or control group (riboflavin at room temperature). The inclusion criteria were patients of any sex, older than 18 years of age with keratoconus diagnosis who needed management with cross-linking in both eyes because of the evidence of progression. The exclusion criteria were patients who had cross-linking without epithelial debridement, unilateral cross-linking, or any other ocular pathologies besides keratoconus and any cognitive incapacity that would make the understanding of the pain test difficult. The main outcome measures were pain, tearing, photophobia, foreign body sensation, and irritation.

RESULTS

At 2 hours post-op, pain in the case and control groups was 3.80 ± 3.00 and 8.08 ± 2.21 (P < 0.05), tearing was 1.56 ± 1.96 and 8.29 ± 2.42 (P < 0.05), photophobia was 5.44 ± 3.57 and 7.83 ± 2.64 (P < 0.05), foreign body sensation was 2.20 ± 2.78 and 6.54 ± 2.73 (P < 0.05), and irritation was 3.48 ± 2.98 and 6.79 ± 3.00 (P < 0.05), respectively. A statistical significant difference was maintained in pain values on day 1 (2.79 ± 3.09 and 4.91 ± 3.27 [P < 0.05]), 2 (2.54 ± 2.41 and 4.00 ± 2.43 [P < 0.05]), and 4 (0.45 ± 0.76 and 1.22 ± 1.67 [P < 0.05]).

CONCLUSIONS

This study demonstrated that pain and associated symptoms decreased significantly in the riboflavin 4°C group.

Clinical guidelines for the management of keratoconus patients with gas permeable contact lenses based on expert consensus and available evidence

PURPOSE OF REVIEW

Fitting rigid gas permeable contact lenses (RGP CLs) in keratoconic patients is the most common visual rehabilitation option to improve patients' quality of life, but require long patient and practitioner chair time. The purpose of this review is to provide evidence-based clinical practice guidelines (CPG) in the management of patients with keratoconus with RGP CLs.

RECENT FINDINGS

An extensive literature review from 1990 to 2017 identified 354 potentially relevant publications. Fifty-two articles were reviewed and included in the CPG. An international expert panel of eight contact lens practitioners, with vast experience in keratoconus management reviewed and appraised the CPG following the Appraisal of Guidelines for Research and Evaluation II consortium requirements. The developed CPG clearly outlines a strategy for the successful fitting of RGP CLs in patients with keratoconus. This includes how to calculate parameters of the first diagnostic lens, criteria for assessing good fit and a standardized schedule of wear time and follow-up appointments.

SUMMARY

The current evidence and consensus-based CPG helps guide clinicians in a successful strategy for fitting RGP CLs in patients with keratoconus.

Experimental evaluation of stiffening effect induced by UVA/Riboflavin corneal cross-linking using intact porcine eye globes

UVA/riboflavin corneal cross-linking (CXL) is a common used approach to treat progressive keratoconus. This study aims to investigate the alteration of corneal stiffness following CXL by mimicking the inflation of the eye under the in vivo loading conditions. Seven paired porcine eye globes were involved in the inflation test to examine the corneal behaviour. Cornea-only model was constructed using the finite element method, without considering the deformation contribution from sclera and limbus. Inverse analysis was conducted to calibrate the non-linear material behaviours in order to reproduce the inflation test. The corneal stress and strain values were then extracted from the finite element models and tangent modulus was calculated under stress level at 0.03 MPa. UVA/riboflavin cross-linked corneas displayed a significant increase in the material stiffness. At the IOP of 27.25 mmHg, the average displacements of corneal apex were 307 ± 65 μm and 437 ± 63 μm (p = 0.02) in CXL and PBS corneas, respectively. Comparisons performed on tangent modulus ratios at a stress of 0.03 MPa, the tangent modulus measured in the corneas treated with the CXL was 2.48 ± 0.69, with a 43±24% increase comparing to its PBS control. The data supported that corneal material properties can be well-described using this inflation methods following CXL. The inflation test is valuable for investigating the mechanical response of the intact human cornea within physiological IOP ranges, providing benchmarks against which the numerical developments can be translated to clinic.

Repeatability and reproducibility of corneal deformation response parameters of dynamic ultra-high-speed Scheimpflug imaging in keratoconus

PURPOSE

To assess the repeatability and reproducibility of dynamic corneal response (DCR) parameters obtained by ultra-high-speed Scheimpflug imaging (Corvis ST); in keratoconic patients.

SETTING

Clinics in Germany, Italy, and Brazil.

DESIGN

Prospective, observational study.

METHODS

Patients were examined 3 times using 2 different dynamic Scheimpflug analyzers (Corvis ST) to obtain repeatability and reproducibility. The reliability of intraocular pressure (IOP), biomechanically corrected IOP (bIOP), pachymetry, and DCR parameters were assessed by the coefficient of repeatability, coefficient of variation (CoV), intraclass correlation coefficient (ICC), and within-subject standard deviation (sw).

RESULTS

Ninety-eight eyes from 98 KC patients were included. The sw of the IOP and bIOP did not exceed 1.1 mm Hg. A CoV less than 10% was found in all DCR parameters and had a good to excellent accordance regarding the ICC. The Corvis Biomechanical Index showed an excellent repeatability and interdevice reproducibility of 0.918 and 0.827, respectively. Also, the tomographic biomechanical index showed an excellent repeatability of 3 Corvis ST and Pentacam measurements (ICC = 0.997). With regard to keratoconic severity, a significant increase in the CoV was found between mild and moderate stages compared with the advanced stage. Nevertheless, it did not exceed 10% of the CoV in severe keratoconic eyes.

CONCLUSION

Corvis ST measurements in keratoconic eyes were highly repeatable and reproducible.

Accuracy of Intraocular Lens Power Formulas Modified for Patients with Keratoconus

PURPOSE

To assess the accuracy of intraocular lens (IOL) power formulas modified specifically for patients with keratoconus (Holladay 2 with keratoconus adjustment and Kane keratoconus formula) compared with normal IOL power formulas (Barrett Universal 2, Haigis, Hoffer Q, Holladay 1, Holladay 2, Kane, and SRK/T).

DESIGN

Retrospective consecutive case series.

PARTICIPANTS

A total of 147 eyes of 147 patients with keratoconus.

METHODS

Data from patients with keratoconus who had preoperative IOLMaster biometry were included. A single eye per qualifying patient was randomly selected. The predicted refraction was calculated for each of the formulas and compared with the actual refractive outcome to give the prediction error. Subgroup analysis based on the steepest corneal power measured by biometry (stage 1: ≤48 diopters [D], stage 2: >48 D and ≤53 D, and stage 3: >53 D) was performed.

MAIN OUTCOME MEASURE

Prediction error.

RESULTS

On the basis of the mean absolute prediction error (MAE), the formulas were ranked as follows: Kane keratoconus formula (0.81 D), SRK/T (1.00 D), Barrett Universal 2 (1.03 D), unmodified Kane (1.05 D), Holladay 1 (1.18 D), unmodified Holladay 2 (1.19 D), Haigis (1.22 D), Hoffer Q (1.30 D), and Holladay 2 with keratoconus adjustment (1.32 D). The Kane keratoconus formula had a statistically significant lower MAE compared with all formulas (P < 0.01). In stage 3 keratoconus, all nonmodified formulas had a hyperopic mean prediction error ranging from 1.72 to 3.02 D.

CONCLUSIONS

The Kane keratoconus formula was the most accurate formula in this series. The SRK/T was the most accurate of the traditional IOL formulas. All normal IOL formulas resulted in hyperopic refractive outcomes that worsened as the corneal power increased. Suggestions for target refractive aims in each stage of keratoconus are given.

Femtosecond Laser-Assisted Small Incision Sutureless Intrastromal Lamellar Keratoplasty (SILK) for Corneal Transplantation in Keratoconus

PURPOSE

To describe a femtosecond laser-assisted small incision sutureless intrastromal lamellar keratoplasty in an eye with severe keratoconus and report on the outcome with a 1-year follow-up.

METHODS

A 20-year-old man with a history of keratoconus presented for evaluation at the Tilganga Institute of Ophthalmology, Kathmandu, Nepal. The patient had previously undergone a deep anterior lamellar keratoplasty in the left eye. Examination of the right eye revealed an uncorrected distance visual acuity (UDVA) of counting fingers with a manifest refraction of -5.00 -3.50 × 170, giving a corrected distance visual acuity (CDVA) of 20/80. Thinnest pachymetry was 425 µm and progression of both anterior and posterior corneal elevation tomography and maximum keratometry was noted compared to examination 2 years prior. The VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany) was used to prepare the donor and recipient cornea. The donor graft was inserted into the recipient through the 3-mm small incision. No sutures were applied.

RESULTS

At 2 weeks postoperatively, UDVA was 20/50 with a manifest refraction of -1.00 -5.00 × 145 (20/32). One year postoperatively, UDVA was 20/80 with a manifest refraction of -2.50 -3.50 × 125 (20/40^-2), with the maximum keratometry decreasing from 64.08 to 56.74 diopters.

CONCLUSIONS

This femtosecond laser-assisted sutureless intrastromal corneal transplantation technique may provide an option to improve the quality of vision for some patients with keratoconus, affording a simpler postoperative follow-up course compared to traditional anterior lamellar or full-thickness corneal transplantation. [J Refract Surg. 2019;35(10):663-671.].

Intracorneal Ring Segments Implantation Outcomes Using Two Different Manufacturers' Nomograms for Keratoconus Surgery

PURPOSE

To compare the outcomes of intracorneal ring segments (ICRS) implantation in keratoconic eyes with a similar tomographic pattern, using two different manufacturers' nomograms for surgical planning.

METHODS

ICRS were implanted alternately in patients with the same tomographic pattern of keratoconus divided into two groups according to the surgical planning proposed by the ICRS manufacturers (Keraring, Mediphacos, Belo Horizonte, Brazil, and Ferrara Ring, AJL Ophthalmics, Vitoria, Spain). Visual, refractive, keratometric, corneal aberrometry, and optical quality changes were evaluated during a 6-month follow-up. Corneal and manifest refractive astigmatic changes were also analyzed using the double-angle polar plot and the Alpins vectorial method through the following components: target induced astigmatism, surgically induced astigmatism, difference vector, correction index, angle of error, index of success, flattening effect, and torque.

RESULTS

After ICRS implantation, both groups showed significant improvement (P < .05) in visual and keratometric data. Corneal aberrometric changes and optical quality improvement were also statistically significant in both groups, except for trefoil (P > .05 in all intervals). The Alpins method analysis showed a better performance in the Keraring group, but with no statistically significant difference between groups (P > .05). Comparison between groups showed a statistically significant difference only in tomographic astigmatism in double-angle polar plot analysis (P = .03), with more significant improvement in the Keraring group.

CONCLUSIONS

Both manufacturers' nomograms resulted in statistically significant improvement in most of the parameters analyzed, with greater correction of corneal tomographic astigmatism in the group operated on according to the spherical equivalent/tomographic astigmatism nomogram. [J Refract Surg. 2019;35(10):673-683.].

Ten-Year Outcomes of Progressive Keratoconus Management With the Athens Protocol (Topography-Guided Partial-Refraction PRK Combined With CXL)

PURPOSE

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 ± 4 months (range: 120 to 146 months). Mean UDVA markedly improved at 1 year (0.19 ± 0.17 to 0.53 ± 0.21 decimal) with further improvement to 0.55 ± 0.19 decimal at 10 years. CDVA increased from 0.59 ± 0.21 to 0.80 ± 0.17 decimal at 1 year and further to 0.81 ± 0.19 decimal at 10 years. Corneal thickness decreased from 468.74 ± 35.05 to 391.14 ± 40.07 μm at 1 year (P < .01) and up to 395.42 ± 32.21 μm at 10 years. Steep keratometry decreased from 50.57 ± 2.80 to 45.87 ± 2.70 diopters (D) (P < .01) at 1 year and to 44.00 ± 3.22 D at 10 years. Maximum keratometry decreased from 53.43 ± 2.97 to 46.17 ± 1.18 D at 1 year and 44.75 ± 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.].

Detection of Subclinical Corneal Ectasia Using Corneal Tomographic and Biomechanical Assessments in a Japanese Population

PURPOSE

To test the detection of subclinical corneal ectasia using integrated Scheimpflug tomography and biomechanical assessment in a Japanese population.

METHODS

This prospective, case-control study included 23 patients with very asymmetric ectasia (VAE) and 70 normal controls. Patients with VAE had defined clinical ectasia in one eye and a fellow eye with normal topography (VAE-NT). Objective topography for confirming normal topography in VAE-NT cases included having 0% similarity and 0% severity derived from Placido-disk based topography. Scheimpflug-based corneal tomography and corneal biomechanical assessment were performed. The Belin/Ambrósio Enhanced Ectasia Deviation index (BAD-D), Corvis Biomechanical Index (CBI), and Tomographic Biomechanical Index (TBI) were compared and their discriminating ability for detecting ectasia was assessed.

RESULTS

For differentiating normal and VAE-NT eyes, the areas under the receiver operating curve for the BAD-D, CBI, and TBI were 0.668, 0.660, and 0.751, respectively. The TBI cut-off of 0.259 provided 52.17% sensitivity and 88.57% specificity. Fourteen VAE-NT cases (60.9%) were abnormal in at least one of the criteria of the BAD-D > 1.60 (39.1%), CBI > 0.5 (26.1%), or TBI > 0.29 (43.5%). Conversely, nine VAE-NT cases (39.1%) exhibited normal values for the BAD-D, CBI, and TBI.

CONCLUSIONS

In the current study, 40% of VAE-NT eyes were classified as normal by the BAD-D, CBI, and TBI. Although some of these cases may truly represent unilateral ectasia, further advances are needed to enhance ectasia detection and characterize the susceptibility for ectasia progression. [J Refract Surg. 2019;35(6):383-390.].

Corneal Viscous Properties Cannot Be Determined From Air-Puff Applanation

PURPOSE

To assess whether corneal viscous properties are measureable with air-puff applanation in patients.

METHODS

The study had 312 normal eyes, 107 fellow eyes of patients with keratoconus, and 289 keratoconic eyes. The Corvis ST (Oculus Optikgeräte GmbH, Wetzlar, Germany) deformation data for all eyes were analyzed using two models. First, a standard linear solid model (SLM) assumed the cornea was an elastic material only. Second, a two-compartment Kelvin-Voigt model (KVM) assumed the cornea was a visco-elastic material. Corneal stiffness and viscosity were calculated. Further, the deflection amplitude was phase shifted virtually relative to the air-puff applanation force to assess whether the KVM was capable of detecting corneal viscous properties from air-puff applanation. This was similar in concept to measured viscoelastic deformations in other soft tissues. The hysteresis area was also calculated with deformation (cornea and whole globe) and deflection (cornea only) amplitude. The greater the magnitude of the hysteresis area, the greater was the magnitude of corneal viscosity (µc).

RESULTS

Both the SLM and KVM reported similar magnitudes of corneal stiffnesses (correlation coefficient > 0.99). However, for a given model, corneal stiffness was significantly different between normal, fellow, and keratoconic eyes (P = .001). From the KVM, the corneal viscosity was different between groups (P = .001) but was small in magnitude (order of 10^-9). The deflection hysteresis area was also small in magnitude (order of 10^-6). In contrast, the KVM detected significant corneal viscosity only when the deflection amplitude was virtually phase shifted with respect to the air-puff applanation force.

CONCLUSIONS

No significant corneal viscous response was detected in patients who had air-puff applanation. [J Refract Surg. 2019;35(11):730-736.].

Biomechanical Analysis of Subclinical Keratoconus With Normal Topographic, Topometric, and Tomographic Findings

PURPOSE

To investigate the corneal biomechanical responses of subclinical keratoconus with normal topographic, topometric, and tomographic findings.

METHODS

In this prospective observational study, the study group was selected from patients with clinically evident keratoconus in one eye and subclinical keratoconus with normal topographic, topometric, and tomographic findings in the fellow eye. The control group was selected from candidates for contact lens use. The biomechanical analyses were performed using the Corvis ST (Oculus Optikgeräte, Wetzlar, Germany). The following parameters were analyzed: A1 velocity, A2 velocity, A1 length, A2 length, deformation amplitude ratio, stiffness parameter at the first applanation, Corvis Biomechanical Index, and Tomographic and Biomechanical Index (TBI).

RESULTS

The study group consisted of 21 patients (10 men and 11 women; mean age: 27.7 ± 6.9 years), and the control group consisted of 35 patients (17 men and 18 women; mean age: 26.1 ± 5.8 years). No significant differences were found between the eyes with subclinical keratoconus and normal eyes in corrected distance visual acuity and the topographic, topometric, and tomographic parameters (P > .05). Significant differences were found in the values of A2 length, A1 velocity, A2 velocity, and TBI between the subclinical keratoconus group and the control group (P < .05). In distinguishing eyes with subclinical keratoconus from normal eyes, the TBI showed the highest area under the curve (0.790; cut-off: 0.29; sensitivity: 67%; specificity: 86%) in the receiver operating characteristic analysis.

CONCLUSIONS

Biomechanical analysis with the Corvis ST may be used as a complementary diagnostic method in detecting subclinical keratoconus. [J Refract Surg. 2019;35(4):247-252.].

One-Year Efficacy and Safety of Combined Photorefractive Keratectomy and Accelerated Corneal Collagen Cross-Linking after Intacs SK Intracorneal Ring Segment Implantation in Moderate Keratoconus

PURPOSE

To report one-year outcomes of a modified version of two-stage multimodal surgical protocol for moderate keratoconus which has been suggesting promising preliminary results.

MATERIALS AND METHODS

30 eyes of 25 patients with moderate keratoconus who exhibited visual complaints and/or disease progression were included for this retrospective case study. Approximately 3 months after implantation of intracorneal ring segment (Intacs SK™), a combination of corneal wavefront-guided transepithelial photorefractive keratectomy (CWG-transPRK, Schwind Amaris® 1050, and Schwind Sirius) and accelerated collagen cross-linking (accCXL, Avedro KXL™) was performed. Patients were examined for uncorrected and corrected distance visual acuity (UDVA; CDVA), keratometric power (K), corneal thickness, and corneal higher-order aberrations (HOAs) preoperatively and at postoperative 1, 3, 6, and 12 months.

RESULTS

The median UDVA and mean CDVA were enhanced from 6/38 to 6/12 and from 6/19 to 6/7.5, respectively, through 12 months after CWG-transPRK/accCXL. The 12-month CDVA of all patients was better than 6/12 Snellen, and no subject lost one or more lines of CDVA. The magnitudes of both myopia and corneal steepness were decreased in turn by Intacs SK implantation and also by CWG-transPRK/accCXL, but the reduction in HOA was largely the result of CWG-transPRK/accCXL. The magnitude of corneal thinning stabilized within 3 months after CWG-transPRK/accCXL.

CONCLUSION

This approach may allow patients with moderate keratoconus to obtain satisfactory vision without the need for contact lens wear. This surgery appeared to be effective and safe through 1 year of follow-up.

Assessment of the Association Between In Vivo Corneal Biomechanical Changes After Corneal Cross-linking and Depth of Demarcation Line

PURPOSE

To test for an association between stiffening following corneal cross-linking (CXL) and demarcation line depth.

METHODS

Sixty-six eyes of 66 patients treated with CXL for progressive keratoconus were included. Dynamic corneal response parameters (DCRs) were measured with the Corvis ST (Oculus Optikgeräte GmbH; Wetzlar, Germany) on the day of CXL and after 1 month. Demarcation line was measured 4 weeks after CXL. A multivariate general linear model was used to test for an association between the change in DCRs and the ratio between demarcation line depth and the postoperative pachymetry.

RESULTS

The authors found no significant associations between the change in inverse concave integrated radius (1/R) and the demarcation line ratio (P = .46), age (P = .33), sex (P = .11), preoperative maximum keratometry (P = .10), and laterality (P = .82). Similarly, there was no significant correlation between the change in 1/R and the demarcation line ratio (R² = .002 and P = .75). However, there was a significant association between the preoperative values of 1/R and the respective change in 1/R (P < .0001). The change in 1/R was inversely proportional to the patient's preoperative 1/R; stiffer corneas (lower values of 1/R) were less affected than less stiff corneas (R² = .23, P < .0001).

CONCLUSIONS

CXL is associated with changes in DCRs, suggesting a change in corneal biomechanics following CXL. These changes do not appear to be associated with the demarcation line depth. [J Refract Surg. 2019;35(3):202-206.].

Iontophoresis CXL With and Without Epithelial Debridement Versus Standard CXL: 2-Year Clinical Results of a Prospective Clinical Study

PURPOSE

To compare the 2-year follow-up outcomes of three groups of patients with keratoconus treated with transepithelial iontophoresis (I-CXL), iontophoresis with epithelial removal (I-SCXL), and standard epithelium-off (S-CXL) CXL for progressive keratoconus.

METHODS

Sixty eyes of 60 patients treated with CXL for progressive keratoconus were included in this comparative, prospective clinical study. Twenty patients were included in each group (I-CXL, I-SCXL, and S-CXL). Corrected distance visual acuity (CDVA), refraction, corneal topography, Scheimpflug tomography, and aberrometry were assessed at baseline and at 1, 3, 6, 12, and 24 months of follow-up. To assess the long-term safety and efficacy of these treatments, the preoperative values were compared with the values at 24 months of follow-up.

RESULTS

The main outcome of the study was the non-statistically significant difference between the three protocols in induced change in most of the parameters, including visual acuity (P = .665), topographic indexes (all P > .05), and maximum keratometry (P = .611) after 2 years of follow-up. There were no significant differences in the change in refractive error following CXL in all groups or between groups (all P > .05). Conversely, I-CXL induced significantly less corneal thinning (P = .0299 and .0121) and a significantly greater reduction of higher order aberrations and coma (all P < .0001) compared to S-CXL and I-SCXL. All protocols induced a significant increase in visual acuity (S-CXL P = .0004, I-SCXL P = .0045, and I-CXL P = .004).

CONCLUSIONS

The 2-year results of this comparative, prospective clinical study demonstrate the efficacy and safety of I-CXL to treat progressive keratoconus and overcome the limitations of CXL with epithelial debridement. [J Refract Surg. 2019;35(3):184-190.].

Long-term Outcomes of a New Surgical Technique for Corneal Remodeling in Corneal Ectasia

PURPOSE

To analyze the outcomes of a new technique (corneal remodeling) to treat corneal ectasia.

METHODS

Sixty-nine cases that underwent corneal remodeling were analyzed. Anesthetic drops were instilled and a femtosecond laser platform was used to perform an 8-mm diameter keratectomy (180°, 270°, or 360°). Once ablation was completed, the edges of the resection were sutured with 8 to 12 interrupted stitches.

RESULTS

Three-year follow-up data are presented. The age of the population was 30.83 ± 12.65 years (range: 16 to 48 years). At 36 months postoperatively, 57.2% presented with uncorrected distance visual acuity (UDVA) of 20/100 or worse and 42.8% achieved between 20/80 and 20/40. After performing photorefractive keratectomy in 3 cases, 14.3% presented with UDVA of 20/100 or worse, 57.2% achieved between 20/80 and 20/40, and 28.5% achieved 20/30 or better in 180° arc length keratectomy. Most parameters compared were moderately to statistically significant (P < .05 to < .0000001).

CONCLUSIONS

Corneal remodeling is a safe technique that produces corneal flattening, reduction of anterior chamber depth, and decreased optical aberrations. It also offers a possibility to perform complementary refractive procedures. [J Refract Surg. 2019;35(4):261-267.].

Tomographic and Biomechanical Scheimpflug Imaging for Keratoconus Characterization: A Validation of Current Indices

PURPOSE

To analyze the potential benefit of the newly developed Tomography and Biomechanical Index (TBI) for early keratoconus screening.

METHODS

In this retrospective study, the discriminatory power of the corneal tomography Belin/Ambrósio Enhanced Ectasia Display (BAD-D) index and the newly developed Corvis Biomechanical Index (CBI) and TBI to differentiate between normal eyes, manifest keratoconus eyes (KCE), very asymmetric keratoconus eyes with ectasia (VAE-E), and their fellow eyes with either regular topography (VAE-NT) or regular topography and tomography (VAE-NTT) were analyzed by applying the t test (for normal distribution), Wilcoxon matched-pairs test (if not normally distributed), and receiver operating characteristic curve (ROC). The DeLong test was used to compare the area under the ROC (AUROC). Further, the cut-offs of the analyzed indices presented in a study by Ambrósio et al. from 2017 were applied in the study population to enable a cross-validation in an independent study population.

RESULTS

All indices demonstrated a high discriminative power when comparing normal and advanced keratoconus, which decreased when comparing normal and VAE-NT eyes and further when analyzing normal versus VAE-NTT eyes. The difference between the AUROCs reached a statistically significant level when comparing TBI versus BAD-D analyzing normal versus all included keratoconic eyes (P = .02). The TBI presented with the highest AUROCs throughout all conducted analyses when comparing different keratoconus stages, although not reaching a statistically significant level. Applying the cut-offs presented by Ambrósio et al. to differentiate between normal and VAE-NT in the study population, the accuracy was reproducible (accuracy in our study population with an optimized TBI cut-off: 0.72, with the cut-off defined by Ambrósio et al. 0.67).

CONCLUSIONS

The TBI enables karatoconus screening in topographical and tomographical regular keratoconic eyes. To further improve the screening accuray, prospective studies should be conducted. [J Refract Surg. 2018;34(12):840-847.].

Long-term Evaluation of Corneal Biomechanical Properties After Corneal Cross-linking for Keratoconus: A 4-Year Longitudinal Study

PURPOSE

To compare the long-term changes in corneal biomechanics, topography, and tomography before and 4 years after corneal cross-linking (CXL) with the Dresden protocol and correlate these changes with visual acuity.

METHODS

In this longitudinal study, 18 eyes of 18 patients with progressive keratoconus who were treated with CXL were included. All patients received a standard ophthalmological examination and were examined by Placido disc-based topography, Scheimpflug tomography, and biomechanical assessments with the Corvis ST (OCULUS Optikgeräte GmbH, Wetzlar, Germany) and Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, NY) before and 4 years after CXL. The main outcome measures were dynamic corneal response (DCR) parameters obtained from the Corvis ST, corneal hysteresis (CH), corneal resistance factor (CRF), visual acuity, refraction, corneal curvature, and corneal thickness.

RESULTS

There were no significant differences in mean visual acuity, refraction, intraocular pressure, corneal topography, corneal astigmatism in both corneal surfaces, maximum keratometry, corneal thickness at apical and thinnest points, thickness profile indices, corneal volume, and specular microscopy before and 4 years after CXL (P > .05). Significant changes were observed in many DCR parameters, including radius at highest concavity and integrated inverse radius, both of which were consistent with stiffening. The CH and CRF values after CXL were not statistically significant. The new parameters using the Corvis ST include integrated inverse concave radius, which showed a significant decrease 1.07 ± 0.93 mm^-1, consistent with stiffening. The corneal stiffness parameter at the first applanation, Ambrósio's Relational Thickness to the horizontal profile, deformation amplitude ratio, and Corvis Biomechanical Index as a combined biomechanical screening parameter did not show significant changes.

CONCLUSIONS

CXL is a minimally invasive treatment option to prevent keratoconus progression over 4 years. Pressure-derived biomechanical parameters obtained from the ORA did not show any change following CXL at 4 years of follow-up, whereas the Corvis ST DCR parameters detected changes in corneal biomechanical properties. [J Refract Surg. 2018;34(12):849-856.].