Jos J. Rozema

Refractive and topographic results of benzalkonium chloride–assisted transepithelial crosslinking

PURPOSE: To evaluate the effect of benzalkonium chloride–assisted (BAC) transepithelial collagen crosslinking (CXL) in eyes with progressive keratoconus and a minimum follow‐up of 6 months. SETTING: Department of Ophthalmology, Antwerp University Hospital, Antwerp, Belgium. DESIGN: Cohort study. METHODS: Eyes with progressive keratoconus had CXL treatment without epithelial debridement. The standard CXL irradiation was preceded by instillation of proparacaine drops 0.5% preserved with BAC 0.005% every 5 minutes for 30 minutes. Selected parameters of refraction assessed by Placido disk (Eyesys) and Scheimpflug (Pentacam) examinations were compared before CXL and after CXL at 6, 12, and 18 months. RESULTS: The study enrolled 53 eyes of 38 patients. Sphere, cylinder, as well as maximum keratometry (K max) simulated K values (steep, flat, astigmatism), and refractive power values (steep, flat, astigmatism) measured using the Placido disk device remained stable over the 18‐month follow‐up. Only corrected distance visual acuity showed a statistically significant improvement at 6 months and 12 months. The Scheimpflug device measurements of maximum K and pachymetry at the thinnest point showed statistically significant progression throughout the study. No patient developed corneal haze or other complications. CONCLUSION: Transepithelial CXL using proparacaine drops 0.5% preserved with BAC 0.005% was less effective than standard CXL in stabilizing progressive keratoconus. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Clinical comparison of 6 aberrometers. Part 1: Technical specifications

Purpose: To provide a detailed assessment of the techniques, technical features, and practical use of 6 aberrometers made available to our institution from September 2002 to January 2004. Setting: Department of Ophthalmology, University Hospital Antwerp, Antwerp, Belgium. Methods: A number of technical and practical parameters are listed for the Visual Function Analyzer (Tracey), the OPD‐scan (ARK 10000; Nidek), the Zywave (Bausch & Lomb), the WASCA (Carl Zeiss Meditec), the MultiSpot Hartmann‐Shack device, and the Allegretto Wave Analyzer including working principles, data acquisition, aberrometer alignment, wavefront calculation, and data analysis. Operator and patient comfort as well as practical advantages and disadvantages are discussed. Conclusion: All devices met at least half the following parameters: alignment, correction for source wavelength, data averaging, measurement quality check, and inhibition of accommodation.

Clinical comparison of 6 aberrometers Part 2: Statistical comparison in a test group

PURPOSE: To compare and mutually validate the measurements of 6 aberrometers: the Visual Function Analyzer (Tracey), the OPD‐Scan (ARK‐10000, Nidek), the Zywave (Bausch & Lomb), the WASCA (Carl Zeiss Meditec), the MultiSpot Hartmann‐Shack device, and the Allegretto Wave Analyzer. SETTING: University Hospital Antwerp, Antwerp, Belgium. METHODS: This prospective study was conducted on a group of 44 healthy eyes with refractions ranging from −5.25 diopters (D) to +5.25 D (cylinder 0 to −2 D). For each aberrometer and each eye, the averaged Zernike data were used to calculate various kinds of root‐mean‐square (RMS). These parameters, together with the refractive parameters, were then analyzed with a repeated‐measures analysis of variance (ANOVA) test, complemented by paired t tests. A similar analysis was done for the comparison of the variances of these parameters. RESULTS: The aberrometers gave comparable values for all studied parameters with the following exceptions: The OPD‐Scan underestimated the polynomials describing 4‐ and 5‐fold symmetries, and the Visual Function Analyzer slightly overestimated the astigmatism terms. The 3rd‐order radial RMS value was different for each device, as well as the RMS in the central 2.0 mm zone. The WASCA presented the lowest variance. CONCLUSION: These results suggest that in healthy eyes, all aberrometers produced globally similar results but they may vary in some details.

Refractive indices used by the Haag-Streit Lenstar to calculate axial biometric dimensions

To estimate refractive indices used by the Lenstar biometer to translate measured optical path lengths into geometrical path lengths within the eye.

Distribution of the Crystalline Lens Power In Vivo as a Function of Age

PURPOSEnTo observe the age-related changes in crystalline lens power in vivo in a noncataractous European population.nnnMETHODSnData were obtained though Project Gullstrand, a multicenter population study with data from healthy phakic subjects between 20 and 85 years old. One randomly selected eye per subject was used. Lens power was calculated using the modified Bennett-Rabbetts method, using biometry data from an autorefractometer, Oculus Pentacam, and Haag-Streit Lenstar.nnnRESULTSnThe study included 1069 Caucasian subjects (490 men, 579 women) with a mean age of 44.2 ± 14.2 years and mean lens power of 24.96 ± 2.18 diopters (D). The average lens power showed a statistically significant decrease as a function of age, with a steeper rate of decrease after the age of 55. The highest crystalline lens power was found in emmetropic eyes and eyes with a short axial length. The correlation of lens power with different refractive components was statistically significant for axial length (r = -0.523, P < 0.01) and anterior chamber depth (r = -0.161, P < 0.01), but not for spherical equivalent and corneal power (P > 0.05).nnnCONCLUSIONSnThis in vivo study showed a monotonous decrease in crystalline lens power with age, with a steeper decline after 55 years. While this finding fundamentally concurs with previous in vivo studies, it is at odds with studies performed on donor eyes that reported lens power increases after the age of 55.

Feasibility of multifocal intra-ocular lens exchange and conversion to the bag-in-the-lens implantation.

Purpose:u2002 Our purpose was to evaluate the surgical outcome after intra‐ocular lens exchange in patients who presented impairing visual complaints after primary multifocal intra‐ocular lens (MIOL) implantation. In particular, the study was undertaken to look at the number of eyes that could be equipped with the bag‐in‐the‐lens (BIL) IOL after MIOL exchange.

Eigencorneas: application of principal component analysis to corneal topography

To determine the minimum number of orthonormal basis functions needed to accurately represent the great majority of corneal topographies from a normal population.

Anterior Corneal, Posterior Corneal, and Lenticular Contributions to Ocular Aberrations.

PurposenTo determine the corneal surfaces and lens contributions to ocular aberrations.nnnMethodsnThere were 61 healthy participants with ages ranging from 20 to 55 years and refractions -8.25 diopters (D) to +3.25 D. Anterior and posterior corneal topographies were obtained with an Oculus Pentacam, and ocular aberrations were obtained with an iTrace aberrometer. Raytracing through models of corneas provided total corneal and surface component aberrations for 5-mm-diameter pupils. Lenticular contributions were given as differences between ocular and corneal aberrations. Theoretical raytracing investigated influence of object distance on aberrations.nnnResultsnApart from defocus, the highest aberration coefficients were horizontal astigmatism, horizontal coma, and spherical aberration. Most correlations between lenticular and ocular parameters were positive and significant, with compensation of total corneal aberrations by lenticular aberrations for 5/12 coefficients. Anterior corneal aberrations were approximately three times higher than posterior corneal aberrations and usually had opposite signs. Corneal topographic centers were displaced from aberrometer pupil centers by 0.32 ± 0.19 mm nasally and 0.02 ± 0.16 mm inferiorly; disregarding corneal decentration relative to pupil center was significant for oblique astigmatism, horizontal coma, and horizontal trefoil. An object at infinity, rather than at the image in the anterior cornea, gave incorrect aberration estimates of the posterior cornea.nnnConclusionsnCorneal and lenticular aberration magnitudes are similar, and aberrations of the anterior corneal surface are approximately three times those of the posterior surface. Corneal decentration relative to pupil center has significant effects on oblique astigmatism, horizontal coma, and horizontal trefoil. When estimating component aberrations, it is important to use correct object/image conjugates and heights at surfaces.

Biometry and visual function of a healthy cohort in Leipzig, Germany.

BackgroundCross-sectional survey of ocular biometry and visual function in healthy eyes across the life span of a German population aged 20 to 69xa0years (nu2009=u2009218). Subject number in percent per age category reflected the percentage within the respective age band of the population of Leipzig, Germany.MethodsMeasurements obtained: subjective and objective refraction, best-corrected visual acuity, accommodation, contrast sensitivity, topography and pachymetry with Scheimpflug camera, axial length with non-contact partial coherence interferometry, and spectral-domain optical coherence tomography of the retina. Pearson correlation coefficients with corresponding p-values were given to present interrelationships between stature, biometric and refractive parameters or their associations with age. Two-sample T-tests were used to calculate gender differences. The area under the logarithmic contrast sensitivity function (AULCSF) was calculated for the analysis of contrast sensitivity as a single figure across a range of spatial frequencies.ResultsThe results of axial length (AL), anterior chamber depth (ACD) and anterior chamber volume (ACV) differed as a function of the age of the participants (rho (p value): AL −0.19 (0.006), ACD −0.56 (<u20090.001), ACV-0.52 (<u20090.001)). Longer eyes had deeper ACD (AL:ACD 0.62 (<u20090.001), greater ACV (AL:ACV 0.65 (<u20090.001) and steeper corneal radii (AL:R1ant; R2ant; R1post; R2post 0.40; 0.35; 0.36; 0.36 (all with (<u20090.001)). Spherical equivalent was associated with age (towards hyperopia: 0.34 (<u20090.001)), AL (−0.66 (<u20090.001)), ACD (−0.52 (<u20090.001)) and ACV (−0.46 (<u20090.001)). Accommodation was found lower for older subjects (negative association with age, ru2009=u2009−0.82 (<u20090.001)) and contrast sensitivity presented with smaller values for older ages (AULCSF −0.38, (<u20090.001)), no change of retinal thickness with age. 58xa0% of the study cohort presented with a change of refractive correction above ±0.50xa0D in one or both eyes (64xa0% of these were habitual spectacle wearers), need for improvement was present in the young age-group and for older subjects with increasing age.ConclusionBiometrical data of healthy German eyes, stratified by age, gender and refractive status, enabled cross-comparison of all parameters, providing an important reference database for future patient-based research and specific in-depth investigations of biometric data in epidemiological research.Trial registrationClinicalTrials.gov # NCT01173614 July 28, 2010

Anterior eye surface changes following miniscleral contact lens wear

PURPOSEnTo quantify the effect of short-term miniscleral contact lens wear on the anterior eye surface of healthy eyes, including cornea, corneo-scleral junction and sclero-conjuctival area.nnnMETHODSnTwelve healthy subjects (29.9u202f±u202f5.7 years) wore a highly gas-permeable miniscleral contact lens of 16.5u202fmm diameter during a 5-hour period. Corneo-scleral height profilometry was captured before, immediately following lens removal and 3u202fh after lens removal. Topography based corneo-scleral limbal radius estimates were derived from height measurements. In addition, elevation differences in corneal and scleral region were calculated with custom-written software. Sclero-conjuctival flattening within different sectors was analysed.nnnRESULTSnShort-term miniscleral lens wear significantly modifies the anterior eye surface. Significant limbal radius increment (meanu202f±u202fstandard deviation) of 146u202f±u202f80u202fμm, (pu202f=u202f0.004) and flattening of -122u202f±u202f90u202fμm in the sclero-conjuctival area, (pu202f<<u202f0.001) were observed immediately following lens removal. These changes did not recede to baseline levels 3u202fh after lens removal. The greatest anterior eye surface flattening was observed in the superior sector. No statistically significant corneal shape change was observed immediately following lens removal or during the recovery period.nnnCONCLUSIONSnShort-term miniscleral contact lens wear in healthy eyes does not produce significant corneal shape changes measured with profilometry but alters sclero-conjuctival topography. In addition, sclero-conjuctival flattening was not uniformly distributed across the anterior eye.