Effect of topographic cone location on outcomes of corneal collagen cross-linking for keratoconus and corneal ectasia.

PURPOSE: To assess the effect of preoperative topographic cone location on 1-year outcomes of corneal collagen cross-linking (CXL). METHODS: In this prospective, randomized, controlled clinical trial, 99 eyes (66 keratoconus, 33 ectasia) from 76 patients underwent CXL. Cone location was defined by the coordinates of preoperative maximum keratometry (maximum K) using the anterior sagittal curvature topography map (Pentacam, Oculus Optikgeräte GmbH). Patients were divided into three groups: those with a maximum K located within the central 3-mm (central cone group), 3- to 5-mm (paracentral cone group), and outside the 5-mm (peripheral cone group) optical zones. Topography and visual acuity data were obtained preoperatively and at 1 year. RESULTS: In the combined cohort, maximum K and uncorrected and corrected distance visual acuity significantly improved by -1.60±3.40 diopters (D) (P<.001), -0.08±0.25 logMAR (P=.001), and -0.10±0.18 log-MAR (P<.001), respectively. Comparing cone groups, maximum K decreased by 2.60±4.50 D (P<.001) in the central cone group, 1.10±2.50 D (P=.02) in the paracentral cone group, and 0.40±1.20 D (P=.08) in the peripheral cone group. Differences among groups were statistically significant (P<.001). Uncorrected distance visual acuity improved by -0.07±0.3 logMAR (P=.1) (central cone group), -0.1±0.17 logMAR (P=.004) (paracentral cone group), and -0.1±0.25 logMAR (P=.04) (peripheral cone group). Corrected distance visual acuity improved by -0.14±0.21 logMAR (P<.001) (central cone group), -0.08±0.17 logMAR (P=.01) (paracentral cone group), and -0.08±0.12 logMAR (P=.002) (peripheral cone group). For both UDVA and CDVA outcomes, these differences among groups were not statistically significant. CONCLUSIONS: After CXL, more topographic flattening occurs in eyes with centrally located cones and the least flattening effect occurs when the cone is located peripherally. This cone-location effect is found in eyes with both keratoconus and ectasia.

Higher-order aberrations after corneal collagen crosslinking for keratoconus and corneal ectasia.

PURPOSE: To determine changes in higher-order aberrations (HOAs) after corneal collagen crosslinking (CXL). SETTING: Cornea and refractive surgery practice. DESIGN: Prospective randomized controlled clinical trial. METHODS: Corneal and ocular HOAs were measured and analyzed using the Pentacam device and Ladarwave aberrometer, respectively, at baseline and 12 months after CXL. RESULTS: Ninety-six eyes (64 keratoconus, 32 ectasia) of 73 patients had CXL. A fellow-eye control group comprised 42 eyes. The mean preoperative total anterior corneal HOAs, total coma, 3rd-order coma, and vertical coma were 4.68 µm ± 2.33 (SD), 4.40 ± 2.32 µm, 4.36 ± 2.30 µm, and 4.04 ± 2.27 µm, respectively. At 1 year, the mean values decreased significantly to 4.27 ± 2.25 µm, 4.01 ± 2.29 µm, 3.96 ± 2.27 µm, and 3.66 ± 2.22 µm, respectively (all P<.001). There were no significant changes in posterior corneal HOAs. The mean preoperative total ocular HOAs, total coma, 3rd-order coma, trefoil, and spherical aberration were 2.80 ± 1.0 µm, 2.60 ± 1.03 µm, 2.57 ± 1.03 µm, 0.98 ± 0.46 µm, and 0.90 ± 0.42 µm, respectively. At 1 year, the mean values decreased significantly to 2.59 ± 1.06 µm, 2.42 ± 1.07 µm, 2.39 ± 1.07 µm, 0.88 ± 0.49 µm, and 0.83 ± 0.38 µm, respectively (all P=.01). After CXL, HOAs were significantly improved compared with the control group. Changes in HOAs were not statistically associated with an improvement in visual acuity or most subjective visual symptoms, however. CONCLUSION: Corneal and ocular HOAs decreased after CXL, suggesting an improvement in corneal shape.

In vivo biomechanical changes after corneal collagen cross-linking for keratoconus and corneal ectasia: 1-year analysis of a randomized, controlled, clinical trial.

PURPOSE: To investigate the in vivo, corneal, biomechanical changes after corneal collagen cross-linking (CXL) using the Ocular Response Analyzer (ORA) in patients with keratoconus and post-laser in situ keratomileusis (LASIK) ectasia. METHODS: Single-center, prospective, randomized, controlled, clinical trial. After CXL (69 eyes, 46 keratoconus and 23 post-LASIK), corneal hysteresis (CH) and corneal resistance factor (CRF) were measured using the ORA and analyzed in a treatment, sham control, and fellow eye control group at baseline and 1, 3, 6, and 12 months. RESULTS: There were no significant changes in CH (change = 0.05 ± 1.5; P = 0.78) or CRF (change = 0.29 ± 1.4; P = 0.1) at 1 year compared with preoperative values. Changes in CH and CRF were not correlated with changes in clinical outcomes of uncorrected visual acuity, best spectacle-corrected visual acuity, and maximum keratometry. There were no significant changes in CH in the sham or fellow eye control groups (P(sham) = 0.7; P(FE) = 0.3) or CRF (P(sham) = 0.6; P(FE) = 0.72). CONCLUSIONS: Despite an increase in CRF at one month, there were no statistically significant changes in CH and CRF measurements 1 year after CXL. Development of other in vivo biomechanical metrics would aid in evaluating the corneal response to CXL.

Corneal topography indices after corneal collagen crosslinking for keratoconus and corneal ectasia: one-year results.

PURPOSE: To evaluate changes in corneal topography indices after corneal collagen crosslinking (CXL) in patients with keratoconus and corneal ectasia and analyze associations of these changes with visual acuity. SETTING: Cornea and refractive surgery subspecialty practice. DESIGN: Prospective randomized controlled clinical trial. METHODS: Corneal collagen crosslinking was performed in eyes with keratoconus or ectasia. Quantitative descriptors of corneal topography were measured with the Pentacam topographer and included 7 indices: index of surface variance, index of vertical asymmetry, keratoconus index, central keratoconus index, minimum radius of curvature, index of height asymmetry, and index of height decentration. Follow-up was 1 year. RESULTS: The study comprised 71 eyes, 49 with keratoconus and 22 with post-LASIK ectasia. In the entire patient cohort, there were significant improvements in the index of surface variance, index of vertical asymmetry, keratoconus index, and minimum radius of curvature at 1 year compared with baseline (all P < .001). There were no significant differences between the keratoconus and ectasia subgroups. Improvements in postoperative indices were not correlated with changes in corrected or uncorrected distance visual acuity. CONCLUSIONS: There were improvements in 4 of 7 topography indices 1 year after CXL, suggesting an overall improvement in corneal shape. However, no significant correlation was found between the changes in individual topography indices and changes in visual acuity after CXL.

Corneal thickness changes after corneal collagen crosslinking for keratoconus and corneal ectasia: one-year results.

PURPOSE: To determine the changes in corneal thickness over time after corneal collagen crosslinking (CXL) for keratoconus and corneal ectasia. SETTING: Cornea and refractive surgery subspecialty practice. DESIGN: Prospective randomized controlled clinical trial. METHODS: Corneal thickness at the apex, thinnest point, and pupil center were measured using Scheimpflug imaging (Pentacam) at baseline and 1, 3, 6, and 12 months after CXL. The treatment group was compared with both a sham-procedure control group and a fellow-eye control group. Associations with clinical outcomes (uncorrected and corrected distance visual acuities and maximum keratometry) were analyzed. RESULTS: The study comprised 82 eyes, 54 with keratoconus and 28 with ectasia after laser in situ keratomileusis. The mean preoperative thinnest pachymetry was 440.7 µm ± 52.9 (SD). After CXL, the cornea thinned at 1 month (mean change -23.8 ± 28.7 µm; P<.001) and from 1 to 3 months (mean change -7.2 ± 20.1 µm, P=.002), followed by a recovery of the corneal thickness between 3 months and 6 months (mean +20.5 ± 20.4 µm; P<.001). At 1 year, apex and pupil-center thicknesses returned to baseline (P=.11 and P=.06, respectively); however, the thinnest pachymetry remained slightly decreased from baseline to 12 months (mean change -6.6 ± 22.4 µm; P=.01). The recovery of corneal thickness was more rapid in ectasia than in keratoconus. There was no association between the degree of corneal thinning at 3 months and clinical outcomes after CXL. CONCLUSIONS: After CXL, the cornea thins and then recovers toward baseline thickness. The cause and implications of corneal thickness changes after CXL remain to be elucidated. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned. Additional disclosure is found in the footnotes.

Corneal collagen crosslinking for keratoconus and corneal ectasia: One-year results.

PURPOSE: To evaluate 1-year outcomes of corneal collagen crosslinking (CXL) for treatment of keratoconus and corneal ectasia. SETTING: Cornea and refractive surgery subspecialty practice. DESIGN: Prospective randomized controlled clinical trial. METHODS: Collagen crosslinking was performed in eyes with keratoconus or ectasia. The treatment group received standard CXL and the sham control group received riboflavin alone. Principal outcomes included uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, astigmatism, and topography-derived outcomes of maximum and average keratometry (K) value. RESULTS: The UDVA improved significantly from 0.84 logMAR ± 0.34 (SD) (20/137) to 0.77 ± 0.37 logMAR (20/117) (P = .04) and the CDVA, from 0.35 ± 0.24 logMAR (20/45) to 0.23 ± 0.21 logMAR (20/34) (P<.001). Fifteen patients (21.1%) gained and 1 patient lost (1.4%) 2 or more Snellen lines of CDVA. The maximum K value decreased from baseline by 1.7 ± 3.9 diopters (D) (P<.001), 2.0 ± 4.4 D (P = .002), and 1.0 ± 2.5 D (P = .08) in the entire cohort, keratoconus subgroup, and ectasia subgroup, respectively. The maximum K value decreased by 2.0 D or more in 22 patients (31.0%) and increased by 2.0 D or more in 3 patients (4.2%). CONCLUSIONS: Collagen crosslinking was effective in improving UDVA, CDVA, the maximum K value, and the average K value. Keratoconus patients had more improvement in topographic measurements than patients with ectasia. Both CDVA and maximum K value worsened between baseline and 1 month, followed by improvement between 1, 3, and 6 months and stabilization thereafter. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned. Additional disclosure is found in the footnotes.

Natural history of corneal haze after collagen crosslinking for keratoconus and corneal ectasia: Scheimpflug and biomicroscopic analysis.

PURPOSE: To determine the natural history of collagen crosslinking (CXL)-associated corneal haze measured by Scheimpflug imagery and slitlamp biomicroscopy in patients with keratoconus or ectasia after laser in situ keratomileusis. SETTING: Cornea and refractive surgery subpecialty practice, United States. DESIGN: Prospective randomized controlled clinical trial. METHODS: The treatment group received ultraviolet-A/riboflavin CXL therapy. The control group received riboflavin alone without epithelial debridement. To objectively measure CXL-associated corneal haze, corneal densitometry using Scheimpflug imagery was measured and the changes in haze were analyzed over time. A similar analysis was performed using clinician-determined slitlamp haze. Correlation of CXL-associated corneal haze with postoperative outcomes was analyzed. RESULTS: The mean preoperative corneal densitometry was 14.9 ± 1.93 (SD) (Pentacam Scheimpflug densitometry units). Densitometry peaked at 1 month (mean 23.4 ± 4.40; P<.001), with little change at 3 months (mean 22.4 ± 4.79; P = .06) and decreased between 3 months and 6 months (19.4 ± 4.48; P<.001) and between 6 months and 12 months. By 12 months, densitometry had not completely returned to baseline in the entire cohort (mean 17.0 ± 3.82; P<.001) and the keratoconus subgroup; however, it returned to baseline in the ectasia group (16.1 ± 2.41; P = .15). The postoperative course of slitlamp haze was similar to objective densitometry measurements. Increased haze, measured by densitometry, did not correlate with postoperative clinical outcomes. CONCLUSIONS: The time course of corneal haze after CXL was objectively quantified; it was greatest at 1 month, plateaued at 3 months, and was significantly decreased between 3 months and 12 months. Changes in haze did not correlate with postoperative clinical outcomes.

Conductive keratoplasty to treat complications of LASIK and photorefractive keratectomy.

PURPOSE: To assess the outcomes of conductive keratoplasty (CK) for patients with complications related to LASIK or photorefractive keratectomy (PRK). DESIGN: Retrospective, noncomparative, interventional case series. PARTICIPANTS: Sixteen eyes of 15 patients were treated using CK after complications of initial LASIK or PRK surgeries. Five cases are described in detail. INTERVENTION: Rehabilitative CK was performed. MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA), refractive error, keratometry, topography analysis, and a subjective assessment of visual quality. RESULTS: After CK treatment, there was a mean improvement in UCVA of 2 lines; 1 eye lost >1 line of UCVA. Best-corrected visual acuity improved or remained the same in 12 of 15 eyes; no eyes lost >1 line of BSCVA. There was a mean reduction in astigmatism of 54%. Videokeratography generally demonstrated improved quality of the corneal optical surface, and patients reported a reduction in optical symptoms such as glare and halo. CONCLUSIONS: Conductive keratoplasty may give improved corneal optics and vision in patients with complications of LASIK or PRK. This application of CK offers an alternative in cases in which further flap manipulation or laser treatments are contraindicated.

Incidence and associations of retreatment after LASIK.

PURPOSE: To determine the incidence and risk factors for laser in situ keratomileusis (LASIK) retreatment and to present a novel retreatment technique. DESIGN: Retrospective noncomparative consecutive case series. PARTICIPANTS: Two thousand four hundred eighty-five eyes (1306 patients) underwent LASIK surgery for myopia, hyperopia, or astigmatism using either the Summit Apex Plus or the Alcon LADARVision excimer laser systems. Only retreatments for residual refractive error were included. MAIN OUTCOME MEASURES: Prevalence and incidence of retreatments were determined. Potential risk factors for retreatment, including age, gender, and attempted correction, were assessed. Refractive error and a ratio of residual sphere to cylinder in retreated eyes were also analyzed. RESULTS: Of the total cohort studied, 288 eyes of 233 patients underwent one retreatment, and 3 eyes of 3 patients required two retreatment procedures. The overall 1-year incidence of retreatment was 10.5%. The average length of time between initial treatment and enhancement was 7.3 +/- 6.4 months; 85% of retreatments took place within 1 year. Two hundred eighty-five of the 288 retreatments were accomplished using a manual flap lift approach; 3 eyes required a repeat microkeratome cut. Higher initial corrections and residual astigmatism were associated with a significantly higher rate of retreatment. Patients older than 40 years were at greater risk for retreatment. There was no gender difference. CONCLUSIONS: Higher initial corrections, astigmatism, and older age are risk factors for LASIK retreatment. Most LASIK flaps can be lifted using the manual technique described up to 3 years after initial surgery.