Jens Bühren

Detection of Subclinical Keratoconus by Using Corneal Anterior and Posterior Surface Aberrations and Thickness Spatial Profiles

PURPOSE. To assess the suitability of corneal anterior and posterior surface aberrations and thickness profile data for discrimination between eyes with early keratoconus (KC), fellow eyes of eyes with early KC, and normal eyes. METHODS. Thirty-two eyes (group 1) of 25 patients were newly diagnosed with KC; 17 eyes of 17 patients (group 2) were asymptomatic fellow eyes without clinical signs of KC. One hundred twenty-three healthy eyes of 69 patients were negative control eyes (group 3). Zernike coefficients from anterior and posterior surfaces, data from corneal thickness spatial profiles, and output values of discriminant functions based on wavefront and pachymetry data were assessed by receiver operating characteristic (ROC) curve analysis for their usefulness in discriminating between KC (groups 1, 2) eyes and control eyes. RESULTS. Vertical coma (C(3)(-1)) from the anterior surface was the coefficient with the highest ability to discriminate between groups 2 and 3 (area under the ROC curve [A(z)ROC] = 0.980; cutoff, -0.2 microm). For posterior wavefront coefficients and pachymetry data, A(z)ROC values were lower. Constructing discriminant functions from Zernike coefficients increased A(z)ROC values. The function containing first-surface data reached an A(z)ROC of 0.993; the functions containing posterior surface or pachymetry data had lower A(z)ROC values (0.932 and 0.903, respectively). The function with anterior, posterior, and pachymetry data reached an A(z)ROC of 1.0. CONCLUSIONS. Corneal wavefront and pachymetry data enabled highly accurate distinction of eyes with subclinical keratoconus from normal eyes. Posterior aberrations and thickness spatial profile data did not markedly improve discriminative ability over that of anterior wavefront data alone.

Intraindividual comparison of higher-order aberrations after implantation of aspherical and spherical intraocular lenses as a function of pupil diameter

PURPOSE: To compare intraindividual higher‐order wavefront aberrations after implantation of aspherical and spherical intraocular lenses (IOLs) as function of pupil diameter. SETTING: Department of Ophthalmology, Johann Wolfgang Goethe‐University, Frankfurt am Main, Germany. METHODS: In this prospective study, wavefront measurements of 21 patients after implantation of a spherical IOL (AMO AR40e) in 1 eye and an aspherical IOL (AMO Tecnis) in the contralateral eye were analyzed. Third‐, 4th‐, 5th‐, total higher‐order aberration (HOA) root‐mean‐square (RMS), and primary spherical aberration (Z40) were compared at different virtual pupil diameters of 3 to 6 mm. RESULTS: For both IOLs and each higher order analyzed, values increased with increasing pupil diameter. Fourth‐order RMS and Z40 in the aspherical IOL group were significantly lower than with the spherical IOL at all analyzed pupil diameters. The total HOA RMS of the aspherical IOL was significantly lower than the spherical IOL only at 6 mm pupil diameter. For 3rd‐ and 5th‐order RMS, no significant difference was found between the tested IOLs at any pupil diameter. CONCLUSION: In comparison to a spherical IOL, the aspherical Tecnis IOL reduced Z40 and 4th‐order RMS significantly for pupil diameters of 3 to 6 mm, whereas total HOA RMS was only significantly reduced for a pupil diameter of 6 mm.

Visual performance of aspherical and spherical intraocular lenses: Intraindividual comparison of visual acuity, contrast sensitivity, and higher-order aberrations

PURPOSE: To intraindividually compare visual performance in terms of photopic high‐contrast visual acuity (HCVA), mesopic HCVA, mesopic low‐contrast visual acuity (LCVA), and contrast sensitivity (CS) in patients after implantation of either an aspherical or a spherical intraocular lens (IOL). SETTING: Department of Ophthalmology, Johann Wolfgang Goethe‐University, Frankfurt am Main, Germany. METHODS: Forty eyes of 20 patients were randomized to implantation of an aspherical IOL (Tecnis Z9000, AMO) in 1 eye and a spherical IOL (Sensar AR40e, AMO) in the other eye. Three to 4 months postoperatively, photopic HCVA (270 cd/m2) was measured with the observer‐independent Frankfurt‐Freiburg Contrast and Acuity Test System (FF‐CATS) and high‐mesopic HCVA and LCVA (8 cd/m2) were measured with Early Treatment Diabetic Retinopathy Study charts. CS was assessed with the FF‐CATS under photopic (167 cd/m2), high‐mesopic (1.67 cd/m2), and low‐mesopic (0.167 cd/m2) luminance conditions with and without glare. For each individual eye, higher‐order wavefront aberrations were reconstructed for a physiological mesopic pupil diameter. Intraindividual differences (Δi) in visual acuity, contrast sensitivity, and higher‐order aberrations (HOAs) were calculated, and the influence of age and Δi HOA on Δi contrast sensitivity (logCS) under high‐mesopic conditions was investigated using multiple regression analysis. RESULTS: There were no statistically significant differences between the Tecnis IOL and the Sensar IOL in visual acuity measurements or contrast sensitivity measurements. For physiological mesopic pupil diameter, primary spherical aberration (Z40) was significantly lower in the Tecnis group (P<.001). For all parameters studied except Z40, the Δi values were distributed around zero. Multiple regression analysis showed only a partial influence of Δi Z40 on Δi logCS (adjusted R2 = 0.49) but did not show any influence of age, coma‐like aberration, or residual HOA. CONCLUSIONS: Although Z40 was significantly lower in the eyes with the aspherical IOL, no statistically significant differences were found between aspherical and spherical IOLs in LCVA, HCVA, and contrast sensitivity. Statistical analysis of intraindividual contrast sensitivity differences showed that in most patients, this Z40 difference was too low to have an effect on contrast sensitivity.

In vivo and in vitro repeatability of Hartmann-Shack aberrometry

Purpose: To assess the in vivo and in vitro repeatability of objective refraction and higher‐order aberrations (HOAs) measured by a commercially available Hartmann‐Shack wavefront sensor. Setting: Department of Ophthalmology, Johann‐Wolfgang‐Goethe University, Frankfurt am Main, Germany. Methods: After pupil dilation of 40 myopic or myopic, astigmatic eyes of 20 patients, wavefront measurements were performed 6 times in each eye and in a test object provided by the manufacturer by 2 experienced examiners using a Hartmann‐Shack wavefront sensor (Zywave®, software version 3.21, Bausch & Lomb). The mean standard deviation (SD) and the coefficient of variation (CV) for sphere, cylinder, and each Zernike polynomial were computed for a 7.0 mm pupil diameter. Vector analysis was performed for the astigmatism. After the data were subdivided into 2 groups with 3 measurements in each, one measurement that best matched the subjective manifest refraction was chosen in each group and the difference between them was calculated. Results: The mean SD (CV) was 0.15 diopter (D) (7%) for the sphere value of the predicted phoropter refraction and 0.16 D (22%) for astigmatism. Thirty‐two eyes had an axis deviation of at least 10 degrees. Vector analysis revealed a mean SD of 0.24@109.8. Other results for mean SD and mean CV were as follows: total in vivo higher‐order RMS, 0.097 &mgr;m, 13.4%; sphere in myopic test device, 0.034 D, 0.65%; sphere in hyperopic test object, 0.035 D, 0.72%. The difference between the 2 best‐matched refractions was significantly different from zero (0.11 D, P<.001). The CV was significantly higher for HOAs than for the 2nd‐order aberrations (defocus and astigmatism). Conclusions: Repeatability of Hartmann‐Shack aberrometry by the Zywave wavefront sensor was not satisfactory, particularly for small amounts of HOAs. Under these conditions, aberrometry measurements should be repeated several times and outliers should be excluded in calculating the means.

Measuring Contrast Sensitivity Under Different Lighting Conditions: Comparison of Three Tests

Purpose. The purpose of this study was to evaluate three psychophysical tests for the measurement of contrast sensitivity (CS) and disability glare (DG) at different luminance levels. Methods. In 60 eyes of 60 individuals (group 1: 20 healthy eyes of young individuals; group 2: 20 healthy eyes of elderly subjects; group 3: 20 eyes with nuclear cataract), CS with best correction was measured twice with the Frankfurt-Freiburg Contrast and Acuity Test System (FF-CATS) and the Functional Acuity Contrast Test (FACT, 1.5 cycles per degree [cpd]) at 167 cd/m2 and 0.167 cd/m2, and with the Pelli-Robson Chart (PRC) at 100 cd/m2 with and without glare. Repeatability of test and retest, and discriminative ability between the different subgroups, were assessed for CS values. Results. Maximum CS values varied across tests. In all groups, highest CS values were obtained with the photopic FF-CATS. For FACT scores at 1.5 cpd, there was a ceiling effect for young subjects. CS scores obtained with the PRC were the lowest. The PRC had the best test–retest repeatability of all tests. Under mesopic conditions with glare, reliability was generally lower; the FF-CATS had the highest repeatability of the mesopic tests. The FF-CATS discriminated best between the different groups for all conditions. Conclusions. There are large discrepancies in the test results between CS testing methods, especially under different lighting conditions. Results from different CS tests are not interchangeable.

Comparison of a digital and a handheld infrared pupillometer for determining scotopic pupil diameter

Purpose: To compare a digital infrared pupillometer with a handheld infrared pupillometer for determining scotopic pupil size. Setting: Department of Ophthalmology, Johann Wolfgang Goethe‐University, Frankfurt am Main, Germany. Methods: In 100 eyes of 50 healthy individuals (mean age 38.8 years ± 10.7 [SD]), the scotopic pupil size was measured with a digital (Procyon) and a handheld (Colvard) infrared pupillometer. After dark adaptation of 1 minute, measurements were performed with both devices by 2 examiners (E1 and E2). Agreement and repeatability were analyzed using a comparison method described by Bland and Altman. Results: The mean scotopic pupil diameter was 5.90 ± 0.97 mm (range 3.24 to 7.91 mm) with the Procyon and 5.78 ± 0.98 mm (range 3.00 to 7.30 mm) with the Colvard pupillometer. The mean difference between the 2 devices was −0.01 mm (E1) and −0.24 mm (E2). The limits of agreement ranged from 2.84 (E1) to 3.24 (E2). The coefficients of repeatability were 0.64 (Procyon) and 1.16 (Colvard). The mean difference between E1 and E2 was −0.10 for the Procyon and 0.13 for the Colvard pupillometer. The limits of agreement ranged from 1.28 (Procyon) to 2.32 (Colvard). Conclusions: The digital infrared pupillometer (Procyon) demonstrated better repeatability and agreement in measuring scotopic pupil size than a handheld device (Colvard).

Effect of Intraocular Lens Asphericity on Quality of Vision after Cataract Removal: An Intraindividual Comparison

PURPOSE To determine the effect of intraocular lens (IOL) asphericity on quality of vision after cataract removal. DESIGN Intraindividual, prospective, randomized clinical trial. PARTICIPANTS Twenty-six cataract patients received 2, one-piece, blue-light-filtering hydrophobic acrylic IOLs each. METHODS One eye was implanted with a spherical (SN60AT, Alcon) and the contralateral eye with an aspheric (SN60WF, Alcon) IOL with -0.2 mum spherical aberration (SA). All trial-specific measurements (corneal topography, wavefront sensing, high-contrast visual acuity [HCVA], contrast sensitivity [CS]) were performed 6 months after surgery. A paired Student t-test or Wilcoxon test was used to check intergroup differences. MAIN OUTCOME MEASURES Absolute values and intraindividual differences (Delta(i)) of corneal and ocular higher order aberrations and best-corrected visual Strehl ratio based on the optical transfer function (BCVSOTF) values for virtual pupil diameters of 3, 4, 5, and 6 mm were computed. Photopic and mesopic HCVA, photopic, and high-mesopic CS as well as high-mesopic disability glare (DG) were measured using the Frankfurt-Freiburg Contrast and Acuity Test System. RESULTS No intergroup difference of demographic data, pupillometry, and corneal aberrations were observed. Coma and trefoil root mean square and SA were significantly lower in the aspheric group resulting in higher BCVSOTF, mesopic HCVA, and photopic and high mesopic CS. All Delta(i) values with exception of photopic HCVA and DG indicated significantly better performance of the aspheric IOL. CONCLUSIONS An aspheric IOL with -0.2 microm SA provide higher quality of vision than spherical IOL in terms of retinal image quality, mesopic HCVA and CS. FINANCIAL DISCLOSURE(S) Proprietary or commercial disclosures may be found after the references.

Prevalence of refractive errors in the European adult population: the Gutenberg Health Study (GHS)

Objective To study the distribution of refractive errors among adults of European descent. Design Population-based eye study in Germany with15 010 participants aged 35–74 years. Methods The study participants underwent a detailed ophthalmic examination according to a standardised protocol. Refractive error was determined by an automatic refraction device (Humphrey HARK 599) without cycloplegia. Definitions for the analysis were myopia <−0.5 dioptres (D), hyperopia >+0.5 D, astigmatism >0.5 cylinder D and anisometropia >1.0 D difference in the spherical equivalent between the eyes. Exclusion criterion was previous cataract or refractive surgery. Results 13 959 subjects were eligible. Refractive errors ranged from −21.5 to +13.88 D. Myopia was present in 35.1% of this study sample, hyperopia in 31.8%, astigmatism in 32.3% and anisometropia in 13.5%. The prevalence of myopia decreased, while the prevalence of hyperopia, astigmatism and anisometropia increased with age. 3.5% of the study sample had no refractive correction for their ametropia. Conclusions Refractive errors affect the majority of the population. The Gutenberg Health Study sample contains more myopes than other study cohorts in adult populations. Our findings do not support the hypothesis of a generally lower prevalence of myopia among adults in Europe as compared with East Asia.

Correlation of infrared pupillometers and CCD-camera imaging from aberrometry and videokeratography for determining scotopic pupil size

Purpose: To compare 2 infrared pupillometers with a videokeratographer and 2 aberrometers for the determination of scotopic pupil size. Setting: Department of Ophthalmology, Johann Wolfgang Goethe‐University, Frankfurt am Main, Germany. Methods: The pupil diameter was measured in 100 eyes of 51 patients after 2 minutes of dark adaptation using the following devices: digital infrared pupillometer (Procyon Instruments Ltd.), handheld infrared pupillometer (Colvard) (Oasis Medical), Zywave® aberrometer (Bausch & Lomb), Wasca aberrometer (Asclepion‐Meditec‐Zeiss), and Orbscan® II topography system (Bausch & Lomb Surgical). Measurements taken with the Procyon pupillometer were considered reference values for comparison with the other devices. Statistical evaluation was performed using the Bland‐Altmann method for comparison of measurement techniques. Results: The mean pupil size was 6.10 mm ± 0.86 (SD) with the Procyon pupil‐ lometer, 5.68 ± 1.07 mm with the Colvard pupillometer, 5.91 ± 1.01 mm with the Zywave aberrometer with the fixating target turned off, 5.09 ± 1.14 mm with the Zywave aberrometer with the fixating target turned on, 5.59 ± 0.99 mm with the Wasca aberrometer, and 3.75 ± 0.67 mm with the Orbscan topographer. The limits of agreement were smallest for measurements between Procyon and Colvard and largest for measurements between Procyon and Orbscan. The sign test revealed statistically significant differences for all devices compared with the Procyon pupillometer (P<.001 in all cases) except the Zywave aberrometer with the fixating target turned off (P = .13). Conclusions: The Zywave wavefront sensor with the fixating target turned off using the study settings and light conditions provided measurements of scotopic pupil diameter that were closest to the reference values (Procyon). With the other devices (Colvard pupillometer, Zywave aberrometer with the fixating target switched on, Wasca aberrometer, and Orbscan topographer), the difference was statistically significant.

Comparison of Endothelial Cell Count Using Confocal and Contact Specular Microscopy

Precise examination of the corneal endothelium has become increasingly important due to the growing number of intraocular and corneal procedures. The purpose of this study was to compare prospectively the corneal endothelial cell count in normal eyes obtained by confocal and specular microscopy. Central corneal endothelial cell densities of 42 eyes from 42 patients were measured by confocal and contact specular microscopy. Endothelial cells were analyzed with the same software in a manual, an automated and a semi-automated mode. The mean endothelial cell density obtained by confocal microscopy was (in the manual, automated and semi-automated modes) 3,069 ± 285, 2,791 ± 344 and 3,077 ± 286 cells/mm2, and obtained by specular microscopy 3,076 ± 298, 2,796 ± 271 and 3,082 ± 282 cells/m2, respectively. No statistically significant difference of endothelial cell density between confocal and specular microscopy was found. Endothelial cell count was significantly lower in the automated than in the semi-automated and manual analysis both with confocal and with specular microscopy. In conclusion, endothelial cell count measurements with confocal and contact specular microscopy are comparable.