Faculty Bibliography

PURPOSE: To investigate, by high-precision digital analysis of data provided by Scheimpflug imaging, changes in pupil size and shape and anterior chamber (AC) parameters following cataract surgery. PATIENTS AND METHODS: The study group (86 eyes, patient age 70.58+/-10.33 years) was subjected to cataract removal surgery with in-the-bag intraocular lens implantation (pseudophakic). A control group of 75 healthy eyes (patient age 51.14+/-16.27 years) was employed for comparison. Scheimpflug imaging (preoperatively and 3 months postoperatively) was employed to investigate central corneal thickness, AC depth, and AC volume. In addition, by digitally analyzing the black-and-white dotted line pupil edge marking in the Scheimpflug "large maps," the horizontal and vertical pupil diameters were individually measured and the pupil eccentricity was calculated. The correlations between AC depth and pupil shape parameters versus patient age, as well as the postoperative AC and pupil size and shape changes, were investigated. RESULTS: Compared to preoperative measurements, AC depth and AC volume of the pseudophakic eyes increased by 0.99+/-0.46 mm (39%; P<0.001) and 43.57+/-24.59 mm(3) (36%; P<0.001), respectively. Pupil size analysis showed that the horizontal pupil diameter was reduced by -0.27+/-0.22 mm (-9.7%; P=0.001) and the vertical pupil diameter was reduced by -0.32+/-0.24 mm (-11%; P<0.001). Pupil eccentricity was reduced by -39.56%; P<0.001. CONCLUSION: Cataract extraction surgery appears to affect pupil size and shape, possibly in correlation to AC depth increase. This novel investigation based on digital analysis of Scheimpflug imaging data suggests that the cataract postoperative photopic pupil is reduced and more circular. These changes appear to be more significant with increasing patient age.

PURPOSE: The aim of this study was to investigate the corneal thickness asymmetry indices in a large pool of patients with keratoconus derived using anterior segment optical coherence tomography (AS-OCT) in comparison with established Scheimpflug imaging-derived keratoconus classification indices. METHODS: Six specific indices were comparatively investigated in this study encompassing 2 groups: keratoconic group A (175 eyes) and age- and gender-matched control group B (175 eyes). AS-OCT was used for corneal focal thinning and irregularity indices, namely the superior nasal minus inferior temporal (SN-IT), superior minus inferior (S-I), minimum minus median (Min-Med) focal thinning, and thickness range, defined as the minimum minus maximum (Min-Max). Scheimpflug imaging was used for keratoconus grading and for investigating anterior surface irregularity index of height decentration (IHD) and index of surface variance (ISV). RESULTS: In study group A, SN-IT was 74.6 +/- 38.9 mum; S-I, 77.3 +/- 42.3 mum; Min-Med, -60.1 +/- 36.8 mum; and Min-Max, -117.7 +/- 55.4 mum. In control group B, SN-IT was 23.32 +/- 11.47 mum; S-I, 22.55 +/- 12.56 mum; Min-Med, -19.69 +/- 5.20 mum; and Min-Max, -55.24 +/- 12.96 mum. In group A, IHD was 0.077 +/- 0.055 and ISV was 84.24 +/- 48.61. In group B, IHD was 0.031 +/- 0.038 and ISV was 31.82 +/- 29.72. A statistically significant relationship was identified between SN-IT, S-I, Min-Med, and Min-Max indices with IHD and ISV (P < 0.01 in all pairs; coefficients of determination 0.649, 0.663, 0.481 and 0.483 versus IHD, and 0.690, 0.722, 0.551, and 0.562 versus ISV, respectively). CONCLUSIONS: This study presents a novel and comprehensive investigation of corneal asymmetry and focal thinning indices for keratoconus by AS-OCT. These indices correlate with established Scheimpflug-derived anterior surface irregularity indices, particularly in the early and milder stages. AS-OCT may hold promise as a helpful screening and diagnostic tool for suspect, early, and clinical keratoconus.

PURPOSE: To determine 3-dimensional corneal pachymetry distribution characteristics in a large pool of healthy normal patients. SETTING: Private practice, Athens, Greece. DESIGN: Prospective case series. METHODS: Spectral-domain anterior segment optical coherence tomography (AS-OCT) was used for measurements of central (CCT) and minimum corneal thickness, thickness asymmetry indices for superonasal-inferotemporal (SN-IT) and superior-inferior (S-I), and focal thinning indices (Min-Med focal thinning, Min-Max thickness range). RESULTS: The study enrolled 561 eyes. The mean values were CCT, 537.17 mum +/- 30.99 (SD) (range 447.0 to 654.0 mum); minimum corneal thickness, 529.01 +/- 30.02 mum (range 435.0 to 644.0 mum); SN-IT, 26.32 +/- 15.06 mum (range -23.0 to 97.0 mum); S-I, 25.34 +/- 15.06 mum (range -36.0 to 93.0 mum); Min-Med, -20.70 +/- 5.99 mum (range -7.0 to -50.0 mum); Min-Max, -59.79 +/- 16.55 mum (range -156.0 to -23.0 mum). There were significant age-related differences; the mean SN-IT was 22.19 +/- 12.40 mum (range -6.0 to 63.0 mum) in the younger group and 30.44 +/- 15.07 mum (range -4.0 to 97.0 mum) in the older group (P=.002). The mean S-I was 21.47 +/- 12.92 mum (range -5.0 to 70.0 mum) and 29.76 +/- 16.27 mum (range -8.0 to 93.0 mum), respectively (P=.001). CONCLUSIONS: Corneal-thickness asymmetry distribution in a healthy eye population obtained by Fourier-domain AS-OCT showed increased asymmetry in the older group; the asymmetry was not sex dependent. These findings may provide a benchmark for future comparative studies. FINANCIAL DISCLOSURES: Dr. Kanellopoulos is a consultant to Alcon Laboratories, Inc., Allergan, Inc., Avedro, Inc., Keramed, Inc., and i-Optics. No other author has a financial or proprietary interest in any material or method mentioned.

PURPOSE: To compare epithelial remodeling in keratoconic eyes that had photorefractive keratectomy and corneal collagen crosslinking (Athens protocol) with that in untreated keratoconic eyes and healthy eyes. SETTING: Private clinical practice, Athens, Greece. DESIGN: Comparative case series. METHODS: Fourier-domain anterior segment optical coherence tomography (AS-OCT) was used to obtain in vivo 3-dimensional epithelial thickness maps and center, superior, inferior, maximum, minimum, mean, midperipheral, and variability data. RESULTS: Group A comprised 175 treated keratoconic eyes (Athens protocol); Group B, 193 untreated keratoconic eyes; and Group C, 160 healthy eyes. The 1-year mean center epithelial thickness in Group A was 47.78 mum +/- 7.36 (SD) (range 33 to 64 mum). At the first clinical visit, it was 52.09 +/- 6.80 mum (range 36 to 72 mum) in Group B and 52.54 +/- 3.23 mum (range 45 to 59 mum) in Group C. The mean thickness range in Group A at 1 year was -19.94 +/- 7.21 mum (range -6 to -34 mum). It was -21.83 +/- 12.07 mum (range -4 to -66 mum) in Group B and -6.86 +/- 3.33 mum (range -3 to -29 mum) in Group C. The mean topographic thickness variability in Group A at 1 year was 4.64 +/- 1.63 mum (range 1.6 to 8.1 mum) (P<.05). It was 5.77 +/- 3.39 mum (range 1.3 to 17.8 mum) in Group B and 1.59 +/- 0.79 mum (range 0.6 to 5.6 mum) in Group C. CONCLUSION: Anterior segment OCT indicated a thinner and more homogeneous remodeled epithelium in the keratoconic eyes treated using the Athens protocol. FINANCIAL DISCLOSURE: Dr. Kanellopoulos is a consultant to Alcon Surgical, Inc.; Wavelight Laser Technologie AG; Avedro, Inc.; and i-Optics Optikgerate GmbH. Dr. Asimellis has no financial or proprietary interest in any material or method mentioned.

PURPOSE: The aim of this study was to evaluate the safety and efficacy of very high-fluence collagen crosslinking (CXL) as a means of achieving increased corneal rigidity and reduced enzymatic digestion in the vehicle cornea of Boston keratoprosthesis (KPro) type 1. METHODS: Eleven consecutive patients fitted with a KPro (5 with a previous repeat cornea graft failure, 4 with ocular cicatricial pemphigoid, and 2 with chemical burn) underwent donor vehicle cornea pretreatment with very high-fluence prophylactic CXL in a 2-step procedure. First, the donor cornea was crosslinked with an intrastromal riboflavin instillation through a femtosecond laser-created pocket. This was followed up with a superficial CXL treatment. On the completion of the CXL pretreatment, the cornea center was trephined with the femtosecond laser, and the KPro was fitted onto the crosslinked donor cornea. Visual acuity, corneal surface, and donor vehicle cornea stability were evaluated. Follow-up evaluations were conducted over the next 9 years with a mean of 7.5 years. RESULTS: Mean uncorrected visual acuity improved from light perception to 20/60. One patient required a follow-up surgery, because of significant melt in the host cornea. None of the eyes developed melts and/or infection, especially on the vehicle cornea on which the KPro was fitted. CONCLUSIONS: Pretreatment with intrastromal and superficial very high-fluence CXL in conjunction with Boston type 1 KPro seems to be a safe and effective adjunctive treatment for achieving increased vehicle donor cornea rigidity. Additionally, there is an increased resistance to enzymatic degradation. This application may serve to enhance the biomechanical stability and external disease resistance of the donor vehicle cornea in patients with advanced external disease.

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: 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: 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 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.

BACKGROUND:The purpose of this study was to determine flap parameter accuracy, extent of the opaque bubble layer, and incidence of skip lines in femtosecond laser-assisted stromal in situ keratomileusis (LASIK) using the WaveLight(®) FS200 laser and optoelectronic clinical measurements. METHODS:Images from 101 flaps were automatically recorded during consecutive routine LASIK procedures performed using the WaveLight FS200 femtosecond laser and the EX500 excimer laser. Digital processing of these images was used to evaluate objectively the diameter of FS200-created flaps, by comparing planned versus achieved procedures and to evaluate the incidence and extent (area) of the opaque bubble layer. RESULTS:The intended flap diameters were between 8.00 mm and 9.50 mm. The achieved flap diameters showed extremely high precision, and were on average -0.16 ± 0.04 mm smaller for a 8.00 mm intended flap diameter, -0.12 ± 0.03 mm smaller for a 8.50 mm flap, and up +0.06 ± 0.06 mm wider for a 9.50 mm flap. With an average flap area of 72.4 mm(2), the mean area of the opaque bubble layer (4.1 ± 4.3 [range 0-14.34] mm(2)) corresponded to a 6% opaque bubble layer-to-flap area. Specifically, 80% of the femtosecond-created flaps had an essentially zero opaque bubble layer (<2.7% of the flap area). CONCLUSION/CONCLUSIONS:In our clinical experience, flaps created using FS200 and this novel highly objective assessment technique demonstrate both precision and reproducibility. The incidence of opaque bubble layer was minimal.