Karolinne Maia Rocha

Central and peripheral corneal thickness measured with optical coherence tomography, Scheimpflug imaging, and ultrasound pachymetry in normal, keratoconus-suspect, and post-laser in situ keratomileusis eyes

PURPOSE: To compare central (CCT) and peripheral corneal thickness (PCT) using Scheimpflug imaging (Pentacam), high‐speed optical coherence tomography (Visante OCT), and ultrasound (US) pachymetry (Sonogage Corneo‐Gage Plus) in normal, keratoconus‐suspect, and post–laser in situ keratomileusis (LASIK) eyes. SETTING: Department of Refractive Surgery, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA. METHODS: The CCT and PCT were retrospectively measured using US pachymetry, Scheimpflug imaging, and high‐speed OCT from January 2006 to March 2008. The influence of age and absolute magnitude of corneal thickness were also analyzed. Analysis was by multivariate generalized estimating equations, multivariate linear regression, and linear regression plots. RESULTS: One hundred sixty‐three eyes were analyzed. Ultrasound pachymetry CCT measurements were consistently higher than Scheimpflug and OCT measurements (mean difference 6.5 μm ± 1.8 [SD] and 7.5 ± 1.4 μm, respectively) (both P<.0005) in normal eyes; the difference was statistically similar and not greater with keratoconus suspicion, age, or absolute magnitude of corneal thickness (P>.05). Scheimpflug measurements were significantly lower than US pachymetry in post‐LASIK eyes (P<.0005). There was no statistically significant difference (mean 0.9 ± 1.4 μm) in Scheimpflug and OCT CCT measurements (P>.5), although Scheimpflug measurements were significantly lower in post‐LASIK eyes (P<.0005). Scheimpflug PCT measurements were higher than OCT measurements, showing more agreement with increasing age (P = .017). CONCLUSIONS: Scheimpflug and OCT CCT measurements were reproducible but always thinner than US pachymetry in normal and keratoconus‐suspect eyes. In post‐LASIK eyes, OCT pachymetry maps were more accurate than Scheimpflug maps. The influence of age on PCT requires further study.

SD-OCT analysis of regional epithelial thickness profiles in keratoconus, postoperative corneal ectasia, and normal eyes.

PURPOSE To assess corneal microarchitecture and regional epithelial thickness profile in eyes with keratoconus, postoperative corneal ectasia (ectasia), and normal unoperated eyes (controls) using spectral-domain optical coherence tomography (SD-OCT). METHODS Regional corneal epithelial thickness profiles were measured with anterior segment SD-OCT (Optovue RTVue-100, Optovue Inc., Fremont, CA). Epithelial thickness was assessed at 21 points, 0.5 mm apart, across the central 6-mm of the corneal apex in the horizontal and vertical meridians. RESULTS One hundred twenty eyes were evaluated, including 49 eyes from 29 patients with keratoconus, 32 eyes from 16 patients with ectasia, and 39 eyes from 21 control patients. Average epithelial thickness at the corneal apex was 41.18 ± 6.47 μm (range: 30 to 51 μm) for keratoconus, 46.5 ± 6.72 μm for ectasia (range: 34 to 60 μm), and 50.45 ± 3.92 μm for controls (range: 42 to 55 μm). Apical epithelial thickness was significantly thinner in eyes with keratoconus (P < .0001) and ectasia (P = .0007) than in controls. Epithelial thickness ranges in all other areas varied widely for keratoconus (range: 21 to 101 μm) and ectasia (range: 30 to 82 μm) compared to controls (range: 43 to 64) (P = .0063). CONCLUSION SD-OCT demonstrated significant central and regional epithelial thickness profile differences between keratoconus, ectasia, and control eyes, with significant variability and unpredictability in ectatic eyes. This regional irregularity may necessitate direct epithelial thickness measurement for treatments where underlying stromal variations may be clinically relevant, including corneal collagen cross-linking or topography-guided ablations.

Expanding depth of focus by modifying higher-order aberrations induced by an adaptive optics visual simulator

PURPOSE: To evaluate the impact of higher‐order aberrations on depth of focus using an adaptive optics visual simulator. SETTING: Refractive Surgery Department, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA. METHODS: An adaptive optics simulator was used to optically introduce individual aberrations in eyes of subjects with a 6.0 mm pupil under cycloplegia (coma and trefoil, magnitudes ±0.3 μm; spherical aberration, magnitudes ±0.3, ±0.6, ±0.9 μm). A through‐focus response curve was assessed by recording the percentage of Sloan letters at a fixed size identified at various target distances. The subjects ocular depth of focus and center of focus were computed as the half‐maximum width and the midpoint of the through‐focus response curve. RESULTS: The dominant eyes of 10 subjects were evaluated. The simulation of positive or negative spherical aberration had the effect of enhancing depth of focus and resulted in linearly shifting of the center of focus by 2.6 diopters (D)/μm of error. This increase in depth of focus reached a maximum of approximately 2.0 D with 0.6 μm of spherical aberration and became smaller when the aberration was increased to 0.9 μm. Trefoil and coma appeared to neither shift the center of focus nor significantly modify the depth of focus. CONCLUSION: The introduction of both positive and negative spherical aberration using adaptive optics technology significantly shifted and expanded the subjects overall depth of focus; simulating coma or trefoil did not produce such effects.

Postoperative wavefront analysis and contrast sensitivity of a multifocal apodized diffractive IOL (ReSTOR) and three monofocal IOLs.

PURPOSE To compare visual acuity, total and high order wavefront aberrations (coma, spherical aberration, and other terms of high order aberration), and contrast sensitivity in 105 eyes implanted with 4 different types of intraocular lenses (IOLs) (1 multifocal apodized diffractive IOL and 3 monofocal IOLs). METHODS A prospective study comparing four types of IOLs (Alcon ReSTOR [50 eyes], Alcon Acrysof MA30AC [20 eyes], Alcon Acrysof SA60AT [20 eyes], and Mediphacos Acqua IOL [15 eyes]) was carried out. All eyes were targeted for emmetropia. Complete ophthalmological examination, including uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), contrast sensitivity (Pelli-Robson chart), and wavefront analysis, was performed 2 months postoperatively. RESULTS All eyes in all groups had BSCVA > or = 20/32 postoperatively. Mean total aberration root-mean-square (RMS) values were: 0.72 +/- 0.25 microm (ReSTOR), 0.94 +/- 0.26 microm (MA30), 0.84 +/- 0.23 microm (SA60), and 2.04 +/- 0.77 microm (Acqua). Mean higher order aberration values were: 0.35 +/- 0.15 microm (ReSTOR), 0.41+/- 0.12 microm (MA30), 0.43 +/- 0.13 microm (SA60), and 0.85 +/- 0.50 microm (Acqua). The Acqua IOL showed statistically significant more total and higher order aberrations when compared with the other IOLs (P < .05). The ReSTOR IOL showed statistically significant less induction of spherical aberration when compared to the monofocal IOLs (P < .05). Mean contrast sensitivity values were: 1.64 +/- 0.08 (ReSTOR), 1.72 +/- 0.08 (MA30), 1.70 +/- 0.07 (SA60), and 1.65 +/- 0.11 (Acqua). CONCLUSIONS Different types of IOLs resulted in measurably different postoperative higher order aberration patterns. The multifocal apodized diffractive IOL (ReSTOR) induced significantly less spherical aberration compared to the monofocal IOLs. Contrast sensitivity revealed better values with MA30 and SA60 IOLs when compared to ReSTOR. The integration of wavefront technology in evaluating pseudophakic patients represents a step towards better understanding and analyzing postoperative visual quality.

Higher-order aberrations of age-related cataract

PURPOSE: To analyze higher‐order aberrations induced by different types of lenticular opacities. SETTING: Federal University of São Paulo, São Paulo, Brazil. METHODS: One hundred thirty‐eyes of 65 patients with bilateral cataract, classified according to the Lens Opacities Classification System III (LOCS III), had complete ophthalmic examinations, corneal topography (EyeSys Technologies), and wavefront analysis (LADARWave, Alcon Laboratories). Patients with cataracts that could not be measured by a Hartmann‐Shack sensor or those with coexisting ocular disease were excluded. Higher‐order aberrations were compared between the nuclear, cortical, and posterior subcapsular groups for statistical significance. RESULTS: One hundred five eyes of 65 patients were assessed. Twenty‐eight eyes (23.33%) had predominantly nuclear opacification (NO1‐NO6 and C1‐2), and 13 (10.83%) had mainly cortical opacification (C1‐4). Sixty‐four eyes (65.83%) had a mixed pattern of LOCS III classification, which hindered the establishment of a correlation between the aberrometry and cataract type. Eighteen eyes that presented with dense posterior subcapsular cataract (P4‐5) and 7 eyes with cortical C5 LOCS III classification were excluded. In eyes with nuclear opacification, the mean spherical aberration with a 6.0 mm pupil was 0.45 μm ± 0.17 (SD) and the mean coma was 0.29 ± 0.13 μm. In eyes with predominantly cortical cataract, the mean spherical aberration was 0.12 ± 0.10 μm and the mean coma was 0.49 ± 0.23 μm. The cortical cataract group had statistically significantly higher coma than the other groups (P<.001). The nuclear cataract group had statistically significantly higher spherical aberrations than the other groups (P<.001). CONCLUSIONS: Different types of early lenticular opacities induced different wavefront aberration profiles. Coma predominated in the cortical cataract group, and spherical aberration predominated in the nuclear cataract group.

Analysis of Microkeratome Thin Flap Architecture Using Fourier-domain Optical Coherence Tomography

PURPOSE To assess the corneal architecture and reproducibility of LASIK flap thickness created by the Amadeus II mechanical microkeratome (Ziemer Ophthalmic Systems AG) using Fourier-domain optical coherence tomography (OCT; Optovue Inc). METHODS Anterior segment Fourier-domain OCT was used to analyze the morphology of 58 LASIK flaps from 30 patients created with the Amadeus II microkeratome 140-μm head and ML7090CLB blades (Med-Logics Inc) at 2 weeks postoperatively. Flap thickness was assessed at 10 points across the central 6 mm of the cornea (horizontal and vertical meridians). Postoperative central corneal flap thickness measured by Fourier-domain OCT was compared with intraoperative ultrasound pachymetry measurements. RESULTS No significant difference was noted between central flap thickness measured by intraoperative pachymetry (107.2 ± 14 μm) and postoperative OCT (111.7 ± 11 μm; P=.07, correlation coefficient=0.86). Fourier-domain OCT measurements demonstrated functionally planar flap architecture (standard deviation [SD] of thickness across the flap=4.9 μm, SD range across the flap=2 to 9 μm) for the microkeratome flaps. CONCLUSIONS The Amadeus II microkeratome with Med-Logics blades created thin, reproducible, functionally planar flaps as measured by Fourier-domain OCT. Central flap thickness measured by intraoperative ultrasound pachymetry was equivalent to that measured 2 weeks postoperatively by OCT.

Epithelial and Stromal Remodeling After Corneal Collagen Cross-linking Evaluated by Spectral-Domain OCT

PURPOSE To evaluate changes in corneal epithelial and stromal thickness after corneal collagen cross-linking (CXL) in eyes with keratoconus and postoperative corneal ectasia using spectral-domain optical coherence tomography (SD-OCT). METHODS Anterior segment SD-OCT (RTVue-100; Optovue, Inc., Fremont, CA) was used to compare regional corneal epithelial and stromal thickness in eyes with keratoconus and ectasia before CXL and 1 and 3 months after CXL. The anterior surface of the cornea, epithelium-Bowmans layer interface, and posterior reflective surface were used as anatomical landmarks to measure epithelial and stromal thickness, respectively. Regional thickness was assessed centrally and at 21 points 0.5 mm apart across the central 6 mm of the corneal vertex in the horizontal and vertical meridians. RESULTS Thirty-one eyes from 30 patients were evaluated, including 17 eyes (17 patients) with keratoconus and 14 eyes (13 patients) with ectasia. Preoperatively, a highly irregular epithelial thickness profile and distribution was observed in both groups. After CXL, epithelial thickness was significantly thinner 2.5 and 2 mm below and 1.5 mm above the corneal apex (49.26 ± 5.69 μm; range: 43 to 62 μm), and 2.5 and 1 mm nasal and 2 mm temporal to the corneal apex (46.66 ± 4.53 μm; range: 39 to 57 μm) compared to preoperative values (P < .05 for all measurements). Epithelial thickness standard deviations were significantly lower (by 3 to 6 μm) 3 months after CXL, compared to ranges before CXL in both the vertical and horizontal meridians for keratoconus and ectasia (P = .048). No significant differences were found between epithelial remodeling in keratoconus and corneal ectasia (P = .98). No significant or consistent stromal changes were found for either group. CONCLUSIONS Significant epithelial remodeling occurs after CXL in eyes with keratoconus and corneal ectasia, creating a similar, more regularized thickness profile in all meridians in the early postoperative period. This pattern of remodeling may facilitate interpretation of corneal curvature and thickness changes after CXL and may be related to visual acuity after CXL.

Enhanced visual acuity and image perception following correction of highly aberrated eyes using an adaptive optics visual simulator.

PURPOSE To evaluate the changes in visual acuity and visual perception generated by correcting higher order aberrations in highly aberrated eyes using a large-stroke adaptive optics visual simulator. METHODS A crx1 Adaptive Optics Visual Simulator (Imagine Eyes) was used to correct and modify the wavefront aberrations in 12 keratoconic eyes and 8 symptomatic postoperative refractive surgery (LASIK) eyes. After measuring ocular aberrations, the device was programmed to compensate for the eyes wavefront error from the second order to the fifth order (6-mm pupil). Visual acuity was assessed through the adaptive optics system using computer-generated ETDRS opto-types and the Freiburg Visual Acuity and Contrast Test. RESULTS Mean higher order aberration root-mean-square (RMS) errors in the keratoconus and symptomatic LASIK eyes were 1.88+/-0.99 microm and 1.62+/-0.79 microm (6-mm pupil), respectively. The visual simulator correction of the higher order aberrations present in the keratoconus eyes improved their visual acuity by a mean of 2 lines when compared to their best spherocylinder correction (mean decimal visual acuity with spherocylindrical correction was 0.31+/-0.18 and improved to 0.44+/-0.23 with higher order aberration correction). In the symptomatic LASIK eyes, the mean decimal visual acuity with spherocylindrical correction improved from 0.54+/-0.16 to 0.71+/-0.13 with higher order aberration correction. The visual perception of ETDRS letters was improved when correcting higher order aberrations. CONCLUSIONS The adaptive optics visual simulator can effectively measure and compensate for higher order aberrations (second to fifth order), which are associated with diminished visual acuity and perception in highly aberrated eyes. The adaptive optics technology may be of clinical benefit when counseling patients with highly aberrated eyes regarding their maximum subjective potential for vision correction.

Calculation of intraocular lens power using Orbscan II quantitative area topography after corneal refractive surgery.

PURPOSE To present the prospective application of the Orbscan II central 2-mm total-mean corneal power obtained by quantitative area topography in intraocular lens (IOL) calculation after refractive surgery. METHODS Calculated and achieved refraction and the difference between them were studied in 77 eyes of 61 patients with previous radial keratotomy (RK), RK and additional surgeries, myopic LASIK, myopic photorefractive keratectomy (PRK), or hyperopic LASIK who underwent phacoemulsification without complications in 3 eye centers. All IOL calculations used the average from the central 2-mm Orbscan II total-mean power of maps centered on the pupil without the use of previous refractive data. Six IOL styles implanted within the bag were used. RESULTS Using the SRK-T formula, the overall calculated refraction was -0.64+/-0.93 diopters (D). The overall achieved spherical equivalent refraction (-0.52+/-0.79 D; range: -3.12 to 1.25 D; 95% confidence interval [CI]: -0.70/-0.34 D) was +/-0.50 D in 53% of eyes, +/-1.00 D in 78% of eyes, and +/-2.00 D in 99% of eyes. The overall difference between the calculated and achieved refraction (0.12+/-0.93 D, P=.27; range: -2.18 to 2.62 D; 95% CI: 0.09/0.33 D) was +/-0.50 D in 39% of eyes, +/-1.00 D in 77% of eyes, and +/-2.00 D in 96% of eyes. This difference was +/-1.00 D in 77% of eyes with RK (P=.70), 82% of eyes with myopic LASIK (P=.34), and 90% of eyes with myopic PRK (P=.96). In eyes with RK followed by LASIK, a trend toward undercorrection was noted (P=.03). In eyes with hyperopic LASIK, a trend toward overcorrection was noted (P=.005). CONCLUSIONS In eyes with previous corneal refractive surgery, IOL power calculation can be performed with reasonable accuracy using the Orbscan II central 2-mm total-mean power. This method had better outcomes in eyes with previous RK, myopic LASIK, and myopic PRK than in eyes with hyperopic LASIK or RK with LASIK.

Comparison of optical aberrations and contrast sensitivity between aspheric and spherical intraocular lenses.

PURPOSE To compare visual acuity, aberrometry, and contrast sensitivity in patients who had a spherical intraocular lens (IOL) (SoFlex SE, Bausch & Lomb) implanted in one eye and an aspheric IOL (SofPort AO, Bausch & Lomb) implanted in the fellow eye during uncomplicated cataract surgery. METHODS A prospective, multicenter, double-blind study was performed. Forty patients (80 eyes) underwent bilateral phacoemulsification with implantation of a spherical IOL in one eye and an aspheric IOL in the fellow eye. Postoperatively, visual acuity, aberrometry, and contrast sensitivity tests were performed. Statistical analyses were performed using Student t and Wilcoxon tests, and mixed effects were used for each contrast condition situation. RESULTS Thirty-nine patients (30 women, 9 men; 78 eyes) with a mean age of 69.3±6.17 years (range: 51 to 82 years) completed the study. No statistical differences were found regarding visual acuity among eyes. Lower levels of higher order aberrations were achieved in the aspheric group. No statistical difference between groups under photopic conditions was noted. In low spatial frequencies, better performance was observed with the aspheric IOL under mesopic conditions. In high spatial frequencies, the spherical IOL produced better quality of vision. Comparing mesopic conditions with glare, visual performance was statistically better using the aspheric IOL. CONCLUSIONS Cataract surgery results cannot be measured by means of visual acuity alone. Quality of vision must be considered, and implantation of IOLs with low levels of spherical aberrations and better contrast sensitivity are preferred. In this study, the aspheric IOL demonstrated better visual function, especially at night, when compared with spherical IOLs.