Faculty Bibliography

PURPOSE: The aim of this study was to evaluate the possible topographic epithelial profile thickness changes (remodeling) after high myopic femtosecond laser in situ keratomileusis (LASIK) with concurrent prophylactic high-fluence cross-linking (CXL) in comparison with standard femtosecond LASIK. METHODS: Preoperative and 6-month postoperative 3-dimensional epithelial thickness distribution maps were investigated through clinical spectral domain anterior-segment optical coherence tomography in 2 groups of femtosecond laser-assisted myopic LASIK cases. Group A represented 67 eyes treated additionally with concurrent prophylactic CXL (LASIK-Xtra); group B represented 72 eyes subjected to stand-alone femtosecond LASIK. Optical coherence tomography measurements of the epithelial thickness over the center 2-mm-diameter disk, mid-peripheral 5-mm rim, and overall (the entire 6-mm-diameter disc area) were investigated. RESULTS: The comparison of matched myopic correction subgroups indicated statistically significant differences in the epithelial thickness increase specifically between high myopia subgroups. For example, in group A (LASIK-Xtra), the mid-peripheral epithelial thickness increase was +3.79 and +3.95 mum for the "-8.00 to -9.00 diopter" and "-7.00 to -8.00 diopter" subgroups, which compare with increased thickness in group B (stand-alone LASIK), of +9.75 mum (P = 0.032) and +7.14 mum (P = 0.041), respectively, for the same subgroups. CONCLUSIONS: Application of prophylactic CXL concurrently with high myopic LASIK operation results in a statistically significant reduced epithelial increase in comparison with stand-alone LASIK. This comparison is observed between matched high myopic correction subgroups. This difference may correlate with higher regression rates and/or may depict increased biomechanical instability in stand-alone LASIK.

PURPOSE: To report a novel application of toric topographically customized transepithelial collagen cross-linking (CXL) aiming to achieve refractive astigmatic changes in a keratoconic cornea. METHODS: Specially formulated riboflavin transepithelial administration and delivery of high-fluence UVA in a topographically customized pattern was applied in an eye with progressive keratoconus. Visual acuity, cornea clarity, keratometry, topography, and pachymetry with a multitude of modalities, as well as endothelial cell counts were evaluated for >6 months. RESULTS: Uncorrected distance visual acuity changed from preoperative 20/40 to 20/25 at 6 months. A mean astigmatic reduction of 0.8 D, and significant cornea surface normalization was achieved 6 months postoperatively. There was some mild change in the epithelial distribution, with the treated area having a slight normalization in the average epithelial thickness. CONCLUSIONS: We introduce herein the novel application of a topographically customizable transepithelial CXL in progressive keratoconus in order to achieve an astigmatic refractive effect and ectasia stabilization. This novel technique offers a nonablative and nonincisional approach to treat irregular astigmatism in ectatic cornea with rapid visual rehabilitation.

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

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

PURPOSE: The aim of this study was to evaluate via Fourier-domain anterior-segment optical coherence tomography 3-dimensional corneal, epithelial, and graft thickness changes after Descemet stripping automated endothelial keratoplasty (DSAEK). METHODS: Sixteen eyes were investigated preoperatively and up to 6 months postoperatively for preoperative and postoperative central corneal thickness (CCT), minimum corneal thickness, central graft thickness (CGT), and for epithelial topographic thickness variability. An age-matched and gender-matched control group of 32 healthy eyes was used for comparison. RESULTS: In the DSAEK group, the preoperative CCT was 582.32 +/- 45.24 (550-615) mum. One-month postoperatively, the CCT was 736.26 +/- 34.52 (713-771) mum, and the CGT was 210.42 +/- 34.52 (145-243) mum. Three months postoperatively, the CCT was 641.39 +/- 38.75 (569-684) mum, and the CGT was 171.23 +/- 27.54 (119-185) mum. The preoperative center epithelial thickness was 55.74 +/- 9.29 (45-74) mum, the minimum was 32.53 +/- 14.30 (13-53) mum, the maximum was 76.00 +/- 11.32 (64-105) mum, and the topographic thickness variability was 10.84 +/- 4.09 (5.90-18.80) mum. Three months postoperatively, the center epithelial thickness was 47.21 +/- 5.45 (43-56) mum, the minimum was 35.11 +/- 4.70 (30-41) mum, the maximum was 58.11 +/- 6.51 (49-65) mum, and the topographic variability was 4.77 +/- 1.48 (2.90-6.50) mum. The average differences were -8.53, +4.53, and -17.89 mum for the center, minimum, and maximum (P < 0.001, <0.001, and <0.001). Similar results were obtained 3 and 6 months postoperatively. CONCLUSIONS: We present a near-term postoperative investigation of the corneal and epithelial thickness changes after DSAEK for bullous keratopathy, by in vivo, clinical anterior-segment optical coherence tomography. Epithelial thickness recovery and normalization and corneal deturgescence were noted as early as in the first postoperative month.

Purpose: To implement digital analysis of pupil imaging (shape and size) in relation to cornea apex position and compare preoperative and postoperative data to measure the possible pupil shape and centration changes following cataract surgery. Methods: 35 consecutive cataract patients (70 eyes) were digitally imaged pre- and post-operatively by Placido Topography (Vario Topolyzer, WaveLight, Erlagen, Germany) providing pupil imaging and cornea apex identification. Digital analysis implemented on the images investigated the Cartesian coordinates (nasal -temporal being the horizontal, and superior-inferior the vertical axis) of the corneal apex (approximating the intersection of line of sight with the cornea) to the pupil geometric center (approximating the visual axis). The Cartesian changes of the differences were associated with postoperative pupil centroid shift. Results: The photopic pupil measurements indicated a pre-operative temporal location of 0.24 +/- 0.15 (0.03 to 0.44) mm and a superior of 0.01+/-0.14 (-0.22 to +0.18) mm. Postoperatively, the pupil center appeared shifted temporally by 0.15 +/- 0.12 (0.27 to -0.01) mm and superiorly by +0.06 +/- 0.21 (-0.33 to 0.22) mm. The scotopic pupil measurements were preoperatively temporally by 0.28 +/- 0.15 (0.41 to 0.03) mm, and inferiorly by 0.02 +/- 0.20 (-0.24 to 0.29) mm. Postoperatively the pupil center was temporally by 0.20 +/- 0.10 (0.04 to 0.28) mm and superiorly by 0.04 +/- 0.19 (-0.26 to +0.27) mm. Conclusions: Cataract extraction surgery appears to affect pupil centration. Specifically a more nasal (+0.10 mm) and more superior (0.05 mm) shift was recorded. These data may have clinical reference in targeted intraoperative IOL centration

Purpose To evaluate applicability of spectral domain optical coherence tomography (AS-OCT) of epithelial thickness patterns in normal and in the diagnosis of keratoconus, and to compare with Scheimpflug imaging keratoconus severity. Methods 250 healthy (control group-A) and 155 untreated keratoconic (study group-B) eyes were subjected to anterior segment OCT three-dimensional epithelial thickness imaging. Comparative statistical analysis of patterns was performed, investigating central, minimum, inferior, posterior, and topographic variability of epithelial thickness. Epithelial thickness characteristics were correlated to established Scheimpflug imaging-derived keratoconus classification and anterior surface irregularity indices. Results Intra-individual repeatability of epithelial thickness was for group-A +/-1.13 mum, for group-B +/-1.78 mum for center and average +/-1.67 mum (center, superior, inferior, maximum and minimum). In group-A, center epithelial was 52.54+/-3.23 mum, maximum 55.33+/-3.27 mum and minimum 48.50+/-3.98 mum. In group B, center thickness was 51.75+/-7.02 mum, maximum and minimum were 63.54+/-8.85 mum and 40.73+/-8.51 mum. Topographic variability was 6.07+/-3.55 mum (range -22.81+/-12.55 mum) for the keratoconic group-B, while for the control group-A 1.59+/-0.79 mum (-6.86+/-3.33 mum). Epithelial thickness topographic variability and range correlated well with keratoconus severity in the study group-B. Conclusions AS-OCT may o er high predictability of 3 dimensional epithelial assessment in keratoconus. Overall epithelial thickness in keratoconic eyes appears significantly different to normal even in lower stages of keratoconus. Increased overall thickness correlated remarkably with keratoconus severity, as defined by established Scheimpflug imaging-derived anterior-surface irregularity indices

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

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

PURPOSE: To evaluate in vivo epithelial thickness in dry eye by anterior segment optical coherence tomography. DESIGN: Observational, retrospective case-control study. METHODS: Two age-matched groups of female subjects, 70 eyes each, age approximately 55 years, were studied in clinical practice setting: a control (unoperated, no ocular pathology) and a dry eye group (clinically confirmed dry eye, unoperated and no other ocular pathology). Corneal epithelium over the entire cornea was topographically imaged via a novel anterior segment optical coherence tomography (AS-OCT) system. Average, central, and peripheral epithelial thickness as well as topographic epithelial thickness variability were measured. RESULTS: For the control group, central epithelial thickness was 53.0 +/- 2.7 mum (45-59 mum). Average epithelium thickness was 53.3 +/- 2.7 mum (46.7-59.6 mum). Topographic thickness variability was 1.9 +/- 1.1 mum (0.7-6.1 mum). For the dry eye group, central epithelial thickness was 59.5 +/- 4.2 mum (50-72 mum) and average thickness was 59.3 +/- 3.4 mum (51.4-70.5 mum). Topographic thickness variability was 2.5 +/- 1.5 mum (0.9-6.9 mum). All pair tests of respective epithelium thickness metrics between the control and dry eye group show statistically significant difference (P < .05). CONCLUSIONS: This study, based on very user-friendly, novel AS-OCT imaging, indicates increased epithelial thickness in dry eyes. The ease of use and the improved predictability offered by AS-OCT epithelial imaging may be a significant clinical advantage. Augmented epithelial thickness in the suspect cases may be employed as an objective clinical indicator of dry eye.