Faculty Bibliography

Purpose: The development of digital, quantitative and accurate analysis of LASIK flap diameter and OBL occurrence.
Method(s): Flaps from 100 consecutive myopic and hyperopic LASIK patients, treated with the Alcon-WaveLight FS200 femtosecond and EX500 excimer lasers were digitally recorded and processed. Flap dimensions and OBL extent was evaluated utilizing a newly-developed digital procedure with a commercially available image processing software. Specifically, the flap creation report image provided by the FS200 internal system was analyzed digitally and calibrated on a scale converting pixels to measurable length in mm. In a similar fashion, the OBL occurrence was measured as a percentage of the actual flap surface area.
Result(s): For the myopic cases, with planned flap diameter 8.00 (n = 20) and 8.50 mm (n = 60), a small negative bias was discovered (- 0.15 mm and -0.12 mm, respectively) with very small size fluctuation (diameter stdev = +/- 0.04 and +/- 0.03 mm, respectively). For the hyperopic cases, with planned flap diameter 9.50 mm (n = 20), a small positive bias was discovered (+ 0.06 mm), again with very small size variation (diameter stdev < 0.009 mm). Of the flaps studied, the majority (> 50%) had negligible or no OBL, and 20% less than 10% of the total flap area. The remaining had OBL to up of 20% of the total flap area. In all cases the flap was 'delayed', that is developing in areas already processed by the femtosecond laser, thus not interfering with the flap creation.
Conclusion(s): this highly accurate, novel validation digital technique confirms the high reproducibility in flap dimensions and small occurrence of OBL in both myopic and hyperopic LASIK cases with the FS200 femtosecond laser

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

BACKGROUND/AIMS: This case report aims to evaluate safety, efficacy and applicability of anterior surface imaging in a patient with forme fruste keratoconus (FFKC) based on a novel multi-spot, multicolor light-emitting-diode (LED) tear film-reflection imaging technology. CASE DESCRIPTION: A 45-year-old male patient, clinically diagnosed with FFKC, with highly asymmetric manifestation between his eyes, was subjected to the multicolor-spot reflection topography. We investigated elevation and sagittal curvature maps comparatively with the multicolor-spot reflection topographer, a Placido topographer and a Scheimpflug imaging system. For the right eye, steep and flat keratometry values were 41.92 and 41.05 D with the multicolor spot-reflection topographer, 42.30 and 42.08 D with the Placido, and 41.95 and 41.19 D with the Scheimpflug system. For the left eye, steep and flat keratometry values were 41.86 and 41.19 D with the multicolor spot-reflection topographer, 42.06 and 41.66 D with the Placido topographer, and 41.96 and 41.66 D with the Scheimpflug camera. Average repeatability of the keratometry measurements was +/-0.35 D for the multicolor spot-reflection topographer, +/-0.30 D for the Placido, and +/-0.25 D for the Scheimpflug camera. Very good agreement between the instruments was demonstrated on the elevation and curvature maps. CONCLUSION: The ease of use and the comparable results offered by the multicolor spot-reflection topographer, in comparison to established Placido and Scheimpflug imaging, as well as the increased predictability that may be offered by the multicolor spot-reflection topographer, may hold promise for wider clinical application, such as screening of young adults for early keratoconus and, in a much wider perspective, potential candidates for laser corneal refractive surgery.

BACKGROUND: The purpose of this study was to compare and correlate central corneal thickness in healthy, nonoperated eyes with three advanced anterior-segment imaging systems: a high-resolution Scheimpflug tomography camera (Oculyzer II), a spectral-domain anterior-segment optical coherence tomography (AS-OCT) system, and a high-frequency ultrasound biomicroscopy (HF-UBM) system. METHODS: Fifty eyes randomly selected from 50 patients were included in the study. Inclusion criteria were healthy, nonoperated eyes examined consecutively by the same examiner. Corneal imaging was performed by three different methods, ie, Oculyzer II, spectral-domain AS-OCT, and FH-UBM. Central corneal thickness measurements were compared using scatter diagrams, Bland-Altman plots (with bias and 95% confidence intervals), and two-paired analysis. RESULTS: The coefficient of determination (r (2)) between the Oculyzer II and AS-OCT measurements was 0.895. Likewise, the coefficient was 0.893 between the Oculyzer II and HF-UBM and 0.830 between the AS-OCT and HF-UBM. The trend line coefficients of linearity were 0.925 between the Oculyzer II and the AS-OCT, 1.006 between the Oculyzer II and HF-UBM, and 0.841 between the AS-OCT and HF-UBM. The differences in average corneal thickness between the three pairs of CCT measurements were -6.86 mum between the Oculyzer II and HF-UBM, -12.20 mum between the AS-OCT and Oculyzer II, and +19.06 mum between the HF-UBM and AS-OCT. CONCLUSION: The three methods used for corneal thickness measurement are highly correlated. Compared with the Scheimplug and ultrasound devices, the AS-OCT appears to report a more accurate, but overally thinner corneal pachymetry.

PURPOSE: To evaluate the potential influence of corneal cross-linking (CXL) with ultraviolet-A light and riboflavin in keratoconic eyes on several objective parameters of dry eye syndrome. METHODS: This prospective single center study included 30 consecutive eyes of 16 patients that underwent CXL with riboflavin and ultraviolet-A treatment (epithelial removal, 30 minutes soaking with riboflavin, 30 minutes of illumination with 365 nm, 3 mW/cm(2), 5 cm distance). Several dry eye syndrome parameters were evaluated preoperatively and 3 and 6 months after the procedure: intra-individual comparison of fluorescein and Rose bengal staining, height of tear film meniscus, and tear film break-up time. RESULTS: Pathologic staining (more than 10 point-shaped areas or diffuse staining) with fluorescein was evident before CXL in 1 eye, 3 months after CXL in 1 eye, and 6 months after CXL in 1 eye. Rose bengal staining 3 and 6 months postoperatively was comparable to preoperative staining. Tear film height was reduced in 2 eyes before CXL and in 4 eyes 3 months postoperatively, and was normal in all eyes after 6 months. The number of eyes with reduced tear film break-up time was not significantly changed. CONCLUSIONS: CXL had no significant impact on several parameters of dry eye syndrome 3 and 6 months postoperatively.

PURPOSE: To evaluate the safety and efficacy of real-time measurement of corneal epithelial thickness and investigate the distribution characteristics in a large normal-eye population using a clinically available spectral-domain anterior-segment optical coherence tomography (AS OCT) system. METHODS: Corneal epithelial thickness distribution and topographic thickness variability were clinically investigated using AS OCT imaging in 373 patients with normal, healthy eyes. Descriptive statistics investigated 3 sets of subgroups, male (n = 171) and female (n = 202), younger (n = 194) and older (n = 179), right eyes (n = 195) and left eyes (n = 197). RESULTS: Pupil center epithelial thickness repeatability was an average 0.88 +/- 0.71 mum; a similar repeatability was noted for the superior, inferior, maximum, and minimum epithelial thickness. On average, the pupil center epithelial thickness was 53.28 +/- 3.34 mum, superior 51.86 +/- 3.78 mum, inferior 53.81 +/- 3.44 mum, minimum 48.65 +/- 4.54 mum, maximum 56.35 +/- 3.80 mum, and topographic variability was 1.78 +/- 0.78 mum. Small differences were noted between male (average center 54.10 +/- 3.34 mum) and female (52.58 +/- 3.19 mum) subjects. The topographic thickness variability seems to increase with age: younger group, 1.65 +/- 0.83 mum; older group, 1.93 +/- 0.90 mum (P = 0.173). CONCLUSIONS: We present a comprehensive investigation of corneal epithelial thickness distribution characteristics in a healthy, untreated human eye population by using in vivo, clinically available Fourier-domain AS OCT. The 3-dimensional epithelial maps reveal epithelial nonuniformity and provide a novel benchmark for future and comparative studies.

PURPOSE: To report the safety and efficacy of a novel surgical technique using two lasers in cataract surgery. METHODS: In this contralateral eye report, a 57-year-old female underwent cataract extraction. Two laser devices and a standard phacoemulsification, platform were used to conduct the procedures. First, a femtosecond laser was used to perform the corneal incision, capsulorhexis, and initial lens fragmentation in each eye. Following this, a nanosecond laser was used to enter the 2.8 mm incision, uni-axially, and complete the viscoelastic-divided nucleus fragment emulsification and removal in one eye. Standard phacoemulsification was used in the completion of the other eye. Posterior chamber foldable acrylic intraocular lenses were implanted in both cases. We evaluated perioperative acuity, refraction, keratometry, Scheimpflug tomography, intraocular pressure, endothelial cell counts, and total energy used with each laser in each case. RESULTS: Corrected distance visual acuity improved from preoperative 20/60 and 20/70 to postoperative 20/20 in both eyes, with 6-month follow-up. In the right eye, the total intraocular energy used was 2 J by the femtosecond laser and 6 J by the phacoemulsification device. In the left eye, the nanosecond laser utilized the same energy of 2 J and the nanosecond laser 2.4 J (80 pulses of 30 mJ each). There were no other differences noted in intraocular pressure or endothelial cell counts. CONCLUSION: In this report, we introduce a bladeless all-laser cataract surgery extraction alternative technique, with several potential novel advantages: enhanced incision and capsulorhexis reproducibility, reduction in intraocular energy used, and elimination of the potential of thermal corneal injury.

PURPOSE: To survey the standard keratoconus grading scale (Pentacam(R)-derived Amsler-Krumeich stages) compared to corneal irregularity indices and best spectacle-corrected distance visual acuity (CDVA). PATIENTS AND METHODS: Two-hundred and twelve keratoconus cases were evaluated for keratoconus grading, anterior surface irregularity indices (measured by Pentacam imaging), and subjective refraction (measured by CDVA). The correlations between CDVA, keratometry, and the Scheimpflug keratoconus grading and the seven anterior surface Pentacam-derived topometric indices - index of surface variance, index of vertical asymmetry, keratoconus index, central keratoconus index, index of height asymmetry, index of height decentration, and index of minimum radius of curvature - were analyzed using paired two-tailed t-tests, coefficient of determination (r(2)), and trendline linearity. RESULTS: The average +/- standard deviation CDVA (expressed decimally) was 0.626 +/- 0.244 for all eyes (range 0.10-1.00). The average flat meridian keratometry was (K1) 46.7 +/- 5.89 D; the average steep keratometry (K2) was 51.05 +/- 6.59 D. The index of surface variance and the index of height decentration had the strongest correlation with topographic keratoconus grading (P < 0.001). CDVA and keratometry correlated poorly with keratoconus severity. CONCLUSION: It is reported here for the first time that the index of surface variance and the index of height decentration may be the most sensitive and specific criteria in the diagnosis, progression, and surgical follow-up of keratoconus. The classification proposed herein may present a novel benchmark in clinical work and future studies.

BACKGROUND: The purpose of this study was to compare the safety and efficacy of two alternative corneal topography data sources used in topography-guided excimer laser normalization, combined with corneal collagen cross-linking in the management of keratoconus using the Athens protocol, ie, a Placido disc imaging device and a Scheimpflug imaging device. METHODS: A total of 181 consecutive patients with keratoconus who underwent the Athens protocol between 2008 and 2011 were studied preoperatively and at months 1, 3, 6, and 12 postoperatively for visual acuity, keratometry, and anterior surface corneal irregularity indices. Two groups were formed, depending on the primary source used for topoguided photoablation, ie, group A (Placido disc) and group B (Scheimpflug rotating camera). One-year changes in visual acuity, keratometry, and seven anterior surface corneal irregularity indices were studied in each group. RESULTS: Changes in visual acuity, expressed as the difference between postoperative and preoperative corrected distance visual acuity were +0.12 +/- 0.20 (range +0.60 to -0.45) for group A and +0.19 +/- 0.20 (range +0.75 to -0.30) for group B. In group A, K1 (flat keratometry) changed from 45.202 +/- 3.782 D to 43.022 +/- 3.819 D, indicating a flattening of -2.18 D, and K2 (steep keratometry) changed from 48.670 +/- 4.066 D to 45.865 +/- 4.794 D, indicating a flattening of -2.805 D. In group B, K1 (flat keratometry) changed from 46.213 +/- 4.082 D to 43.190 +/- 4.398 D, indicating a flattening of -3.023 D, and K2 (steep keratometry) changed from 50.774 +/- 5.210 D to 46.380 +/- 5.006 D, indicating a flattening of -4.394 D. For group A, the index of surface variance decreased to -5.07% and the index of height decentration to -26.81%. In group B, the index of surface variance decreased to -18.35% and the index of height decentration to -39.03%. These reductions indicate that the corneal surface became less irregular (index of surface variance) and the "cone" flatter and more central (index of height decentration) postoperatively. CONCLUSION: Of the two sources of primary corneal data, the Scheimpflug rotating camera (Oculyzer) for topography-guided normalization treatment with the WaveLight excimer laser platform appeared to provide more statistically significant improvement than the Placido disc topographer (Topolyzer). Overall, the Athens protocol, aiming both to halt progression of keratoconic ectasia and to improve corneal topometry and visual performance, produced safe and satisfactory refractive, keratometric, and topometric results. The observed changes in visual acuity, along with keratometric flattening and topometric improvement, are suggestive of overall postoperative improvement.