Corneal Wavefront Aberrations Research Articles

Comparison of the efficacy of femtosecond laser small incision lenticule extraction and femtosecond laser assisted LASIK

Objective To compare the efficacy of femtosecond laser small incision lenticule extraction(SMILE) and femtosecond laser assisted LASIK(FS-LASIK). Methods This is a prospective nonrandom cohort study. There were 200 eyes of 200 cases in both SMILE group and FS-LASIK group respectively. Uncorrected visual acuity(UCVA), best corrected visual acuity(BCVA) and residual refraction (spherical equivalent, SE) were measured before surgery and 3 months after surgery. Vertex altitude of corneal posterior surface and corneal wavefront aberrations were measured by pentacam. Data were compared between two groups and between preoperation and postoperation in same group. Results Difference was not statistically significant in visual acuities, SE, safety, effectiveness and predictability between two groups (P>0.05). Pre-operative and postoperative vertex altitude of corneal posterior surface in SMILE group were(1.96±2.15) μm, and(2.08±1.87)μm, whereas those in FS-LASIK group were(1.96±2.15) μm, and(2.08±1.87)μm, and there were no statistically significant differences between preoperative and postoperative results in both groups (P>0.05). There was no statistically significant difference in postoperative outcome between two groups(t=2.527, P=0.16). Compared with pre-operative results, the corneal aberrations increased after surgeries, including root mean square of total (RMS TOTAL), root mean square of lower-order abberation (RMS LOA), root mean square of higher-order abberation (RMS HOA) and root mean square of spherical abberation (RMS Z4, 0) (P=0.000). Although corneal aberrations in SMILE group were bigger than those in FS-LASIK group, but there were no statistically significant differences between two groups (P>0.05). Conclusion Both SMILE group and FS-LASIK group have good safety, effectiveness and predictability, and corneal posterior surfaces of two groups all keep stable after surgery. Small incision without corneal flap is the most significant advantage of SMILE which can avoid potential risks, such as striation, shift and losing of corneal flap. Key words: Keratomileusis, laser in situ, femtosecond laser assisted(FS-LASIK); Small incision lenticule extraction (SMILE)

Changes in Keratocyte Density and Visual Function Five Years After Laser In Situ Keratomileusis: Femtosecond Laser Versus Mechanical Microkeratome

To determine the effects of keratocyte loss on optical properties and vision after laser in situ keratomileusis (LASIK) with the flap created with a femtosecond laser or a mechanical microkeratome. Randomized clinical paired-eye study. Both eyes of 21 patients received LASIK for myopia or myopic astigmatism. One eye of each patient was randomized by ocular dominance to flap creation with a femtosecond laser and the other eye to flap creation with a mechanical microkeratome. Before LASIK and at 1, 3, and 6 months and 1, 3, and 5 years after LASIK, keratocyte density was measured using confocal microscopy, and high-contrast visual acuity and anterior corneal wavefront aberrations were measured by standard methods. At each visit, all variables were compared between methods of creating the flap and to the same variable before treatment using paired tests with Bonferroni correction for multiple comparisons. Keratocyte density in the flap decreased by 20% during the first year after LASIK and remained low through 5 years (P < .001). High-order wavefront aberrations increased and uncorrected visual acuity improved immediately after surgery, but these variables did not change further to 5 years. There were no differences in any variables between treatments. A sustained reduction in keratocyte density does not affect vision or optical properties of the cornea through 5 years after LASIK. The method of creating a LASIK flap does not influence the changes in keratocyte density in the flap.

Change of higher order aberration after 2 mm micro-incision SMILE in myopia

Background Small incision lenticule extraction (SMILE) is increasingly used for myopia.However,the size of the incision varied in different operators.The influence of 2 mm micro-incision SMILE on postoperative diopter and aberrations is not clear yet. Objective The aim of the current study was to perform a clinical analysis of the efficacy,safety,stability and predictability of 2 mm micro-incision SMILE and investigate the influence of preoperative sphere and cylinder power on postoperative aberrations. Methods A serial cases observational study was carried out under the approval of Ethic Committee of Tianjin Eye Hospital and informed consent of each patient.Fifty-five eyes of 31 subjects with myopia and myopic astigmatism were enrolled in this study in Tianjin Eye Hospital from January to April 2013 and a 2 mm micro-incision SMILE was performed on the eyes.Follow-up visits were performed at 1 week,1 month and 6 months after operation.Uncorrected visual acuity (UCVA),best corrected visual acuity (BCVA),manifest and cycloplegic refraction were examined at each postoperative time points to evaluate the efficacy,safety,stability and predictability of 2 mm micro-incision SMILE.Wave-front aberrations were measured by WaveScan aberrometer.Repeated measurement analysis of variance was used for the comparison of the differences of aberrations before and after the surgery.And the differences between various follow-up visits were compared with LSD-t test.The relationship between preoperative sphere or cylinder power and aberrations postoperatively were analyzed by Spearman rank correlation. Results At 1 week,1 month and 6 months postoperatively,the effective index was 1.2,and the safety indexes were 1.2,1.2 and 1.5 respectively.The spherical equivalent remained 0.00 D at each postoperative time point.And 96.4% and 97.8% of eyes were within ±0.5 D of intend correction and 100% were within ±1.0 D of the intend correction at 1 month and 6 months postoperatively.Vertical coma (Z7) and spherical aberration (Z12) were significantly raised at 1 week,1 month and 6 months after surgery compared with the values preoperatively (Z7:t=9.668,10.607,9.772,all at P 0.05).Third-order to sixth-order aberrations and higher order abberration (HOA) showed significant increase at various time points after the surgery compared with the values before surgery (all at P 0.05).Positive correlations were found between preoperative sphere and S3,S4 and HOA at 1 week,1 month and 6 months postoperatively (P<0.05).Negative correlations were found between preoperative cylinder and S3,S4 and HOA at postoperatively various time points (all at P<0.05).In addition,significant positive correlations were seen between Z7 and preoperative cylinder as well as between Z12 and sphere preoperatively,and negative correlations also were observed between Z7 and preoperative sphere as well as between Z12 and cylinder preoperatively at each follow-up visits(all at P<0.05). Conclusions SMILE with 2 mm micro-incision is a safe, effective, stable and predictable procedure for myopic and myopic astigmatism eyes. The aberrations and Zernike terms remain stable after surgery until 6 months although these parameters present elevation to a certain extent. Preoperative SE and astigmatism power affect postoperative aberrations. Key words: Adult; Aberrometry; Myopia/surgery; Refraction, ocular; Corneal wavefront aberration; Femtosecond laser; Microsurgery; Small incision lenticule extraction

Intrasubject repeatability of corneal power, thickness, and wavefront aberrations with a new version of a dual rotating Scheimpflug–Placido system

To determine the intrasubject repeatability of a recently introduced dual-camera rotating Scheimpflug-Placido imaging system (Galilei G4) in determining corneal thickness, power, and wavefront aberrations in young healthy subjects. University of Valencia, Valencia, Spain. Prospective evaluation of diagnostic technology. The study comprised right eyes of 25 subjects aged 20 to 40 years with a spherical equivalent ranging from -4.25 to +1.00 diopters. The central corneal thickness, thinnest point value and location, anterior and posterior surface curvatures, total corneal power, and corneal wavefront aberrations were measured for distance vision using the dual Scheimpflug-Placido system. Three consecutive measurements were taken in each eye. Twenty-five eyes were evaluated. Repeated-measures analysis of variance showed the only statistically significant difference between the 3 repeated measures to be in trefoil aberration. Intraclass correlation coefficients (ICCs) were higher than 0.950 for all the parameters except the thinnest point chord distance to geometric corneal center (0.528) and chord angle (0.742), corneal astigmatism (0.811) and its vector components J0 (0.891) and J45 (0.724), and all wavefront aberrations. The new dual Scheimpflug-Placido system had high intraobserver repeatability for corneal power and thickness and moderate repeatability for corneal astigmatism and corneal wavefront aberrations in healthy corneas with low astigmatism. This iteration of the device performed better in young healthy corneas than preceding versions. No author has a financial or proprietary interest in any material or method mentioned.

Cone Location–Dependent Outcomes After Combined Topography-Guided Photorefractive Keratectomy and Collagen Cross-linking

To evaluate the effect of keratoconus cone location on the change in refractive outcomes, corneal aberrations, and biomechanics after combined topography-guided photorefractive keratectomy (PRK) and collagen cross-linking (CXL). Prospective, comparative case series. Topography-guided PRK was performed followed by accelerated CXL using riboflavin A and enhanced-intensity (30 mW/cm(2)) ultraviolet light. Outcome parameters including uncorrected distance visual acuity (UDVA) and best-corrected distance visual acuity (BDVA), corneal tomography and biomechanics (corneal hysteresis [CH] and corneal resistance factor [CRF]), and corneal wavefront aberrations were assessed before and a year after the procedure. Eyes were subdivided into 2 groups preoperatively for statistical analysis: Group 1, cone located within the central 2-mm zone; and Group 2, cone located outside the central 2-mm zone. UDVA, BDVA, sphere, cylinder, and simulated keratometry improved after treatment in both groups (P < .05). However, BDVA improved more in Group 1 than in Group 2 (P= .04) and the other variables were not affected by cone location. A few corneal wavefront Zernike aberrations changed after treatment (P < .05) but none were affected by cone location (P > .05). CH and CRF increased after treatment in both groups (P > .05). Interestingly, the increases in CH and CRF were greater in Group 2 than in Group 1 (P > .05). Cone location appeared to impact only visual acuity and biomechanics after the combined procedure. The greater increase in CH and CRF in Group 2 may indicate differences in the ablation profile and variability in CXL outcomes and requires further study.

Clinical study of customized aspherical intraocular lens implants.

To compare if there is an improvement in visual functions with age-related cataracts between patients receiving a aspherical intraocular lens (IOL) based on corneal wavefront aberration and patients randomly assigned lenses. A total of 124 eyes of 124 patients with age-related cataracts were placed in experimental group and a group receiving randomly assigned (RA) lenses. The experimental group was undergone Pentacam corneal spherical aberration measurement before surgery; the targeted range for residual total spherical aberration after surgery was set to 0-0.3 µm. Patients with a corneal spherical aberration <0.3 µm were implanted with a zero-spherical aberration advanced optics (AO) aspherical IOL and patients with an aberration ≥0.3 µm received a Tecnis Z9003 aspherical lens in experimental group. RA patients were randomly implanted with an AO lens or a Tecnis Z9003 lens. Three months after surgery total spherical aberration, photopic/mesopic contrast sensitivities, photopic/mesopic with glare contrast sensitivities, and logMAR vision were measured. Statistical analysis on logMAR vision showed no significant difference between two groups (P=0.413). The post-surgical total spherical aberration was 0.126±0.097 µm and 0.152±0.151 µm in the experimental and RA groups, respectively (P=0.12). The mesopic contrast sensitivities at spatial frequencies of 6, 12 and 18 c/d in the experimental group were significantly higher than of the RA group (P=0.00; P=0.04; P=0.02). The mesopic with glare contrast sensitivity in the experimental group at a spatial frequency of 18 c/d was also significantly higher vs the RA group (P=0.01). Pre-surgical corneal spherical aberration measurement in cataract patients followed by customized selection of aspherical IOL implants improved mesopic contrast sensitivities at high spatial frequencies, and thus is a superior strategy compared to the random selection of aspherical IOL implants.

Topography-guided Photorefractive Keratectomy for Irregular Astigmatism After Small Incision Lenticule Extraction

To report the outcome of topography-guided photorefractive keratectomy (PRK) after complicated small incision lenticule extraction (SMILE). Retrospective case series of 5 eyes with irregular topography and ghost images after complicated SMILE. All eyes received transepithelial topography-guided PRK. Two eyes were treated with 0.02% mitomycin C. Patients were examined after a minimum of 3 months with evaluation of uncorrected (UDVA) and corrected (CDVA) distance visual acuity, Pentacam tomography (Oculus Optikgeräte, Wetzlar, Germany), and whole-eye aberrometry. In 3 eyes, subjective symptoms were diminished and UDVA, CDVA, topography, and corneal wavefront aberrations were improved. The remaining 2 eyes developed significant haze with worsened topography and wavefront aberrations. One eye experienced a two-line reduction in CDVA. Eyes with haze development had not been treated with mitomycin C. Transepithelial topography-guided PRK may reduce visual symptoms after complicated SMILE if postoperative haze can be controlled. To reduce the risk of haze development, application of mitomycin C may be considered.

Investigation of the Efficacy of the Cone Location and Magnitude Index in the Diagnosis of Keratoconus

Purpose: The aim of this study was to investigate the sensitivity, specificity, and accuracy of The Cone Location and Magnitude Index (CLMI) in keratoconus diagnosis. Methods: 301 eyes of 159 keratoconus patients and 394 eyes of 265 refractive surgery candidates as a control group were enrolled in this retrospective clinical study. CLMI was compared with keratometric corneal topography parameters, wavefront aberrations, and pachymetry data derived from optical coherence tomography using independent sample t-tests and ROC curves. Logistic regression analysis was applied to determine the most accurate parameter in keratoconus diagnosis. Pearson’s correlation analysis was used to determine the correlation between CLMI and the other measurements. Results: Average axial CLMI (aCLMI) was 8.19 ± 6.15 D in the keratoconus group and 0.83 ± 0.62 D in the control group (p = 0.001). aCLMI had the greatest sensitivity (89%), specificity (94%), and accuracy (92%) for the keratoconus diagnosis at the best cut-off point of 1.82 according to the ROC curve. Logistic regression analysis selected aCLMI as the most accurate measurement among the other parameters (accuracy 92.8%). aCLMI showed strongest correlations with coma-like aberrations (r = 0.881), total high-order aberrations (r = 0.858), and vertical coma (r = −0.814), respectively. Conclusion: CLMI is a robust index for screening keratoconus with high sensitivity, specificity, and accuracy.

Preliminary investigation of corneal wavefront aberration following femtosecond laser clear corneal incision for cataract surgery.

To investigate the early changes of the anterior corneal wavefront aberration (WA) following femtosecond laser clear corneal incision (FS-CCI) for cataract surgery. Twenty consecutive patients (20 eyes) with cataract underwent phacoemulsification and were divided into 2 groups: the study group received a 2.75-mm FS-CCI using an iFS Intralase; the control group received a 2.75-mm manual CCI using disposable knives. High-order corneal WA was analyzed over 3.5- and 6.0-mm pupils and corneal astigmatism was evaluated using vector analysis preoperatively, 1 week postoperatively, and 1 month postoperatively. At 1 month postoperatively, the mean surgically induced astigmatism (D) of the anterior cornea was 1.22 ± 0.60 at 144° and 1.04 D ± 0.64 at 90° in the study and control groups (p&lt;0.05), respectively. Over 3.5-mm pupil, there were no changes of corneal high-order aberrations (p&gt;0.05) following FS-CCI. Trefoil increased significantly (p&lt;0.01) following manual CCI at 1 week postoperatively. Over 6.0-mm pupil, FS-CCI did not induce any statistically significant change in corneal WA during follow-up. One week after manual CCI, total root mean square-high order aberrations (p&lt;0.01), spherical aberration (p&lt;0.05), and trefoil (p&lt;0.001) were statistically significantly higher than preoperatively. The CCI method was shown to influence changes in corneal WA during the first month postoperatively. The different changes of corneal high-order WA between the study and control groups may depend on the different CCI geometry. These preliminary data are valuable to improve understanding of FS-CCI design.

Corneal Reshaping and Wavefront Aberrations During Overnight Orthokeratology

To investigate changes of corneal thickness at the vertical and horizontal meridians and of wavefront aberrations (WA) over a 30-day period of overnight myopia orthokeratology (OK) lens wear. Sixteen subjects (11 women, 5 men, 26.3±3.2 years) were enrolled and fitted for OK lenses. Long scan depth optical coherence tomography was used to measure corneal thickness profiles at both horizontal and vertical meridians at baseline and on days 1, 7, and 30 days. Corneal and ocular WA of a 6-mm pupil were measured and the root-mean-square (RMS) of the astigmatism, coma, spherical aberration (SA), and total higher-order aberrations (HOAs) were determined. During the 30-day period, the central cornea thinned in the horizontal and vertical meridians, whereas corneal thickening occurred in the temporal, nasal, and inferior mid-peripheries. In contrast, the cornea thinned in the mid-peripheral superior. There were significant increases in RMS for astigmatism, SA, coma, and positive horizontal coma during the study period. After OK, there were significant positive correlations between the midperipheral-central thickness change difference and the changes in corneal and ocular RMS of total HOAs and SA (r range: 0.281 to 0.492, P<0.05). Only the change of corneal coma RMS was correlated with midperipheral-central thickness change difference (r=0.270, P<0.05). The change in corneal horizontal coma was correlated with the temporal-nasal thickness change difference (r=-0.289, P<0.05). Overnight OK caused unique changes in corneal thickness profiles at the vertical and horizontal meridians and increased corneal and ocular HOAs related to corneal reshaping.

Corneal astigmatism change and wavefront aberration evaluation after cataract surgery: "Single" versus "paired opposite" clear corneal incisions

Background:Correcting the pre-existing astigmatism is an optimal goal in cataract surgery. The aim of this study is to compare the astigmatic correcting effect of a single regular 3.2 mm clear corneal incision (CCI) with paired opposite CCI in cataract patients and effect of these incisions on optical aberrations using the wavefront quantitative analysis.Materials and Methods:This was a randomized controlled trial study undertaken in an ophthalmology referral center on 50 patients planned for cataract surgery who were randomized to either single 3.2 mm CCI or paired opposite CCI group. Post-operative evaluation was performed at 12 weeks and included refraction, keratometery, corneal topography and wavefront analysis. Corneal astigmatism and post-operative values were compared in two groups.Results:The mean pre-operative corneal astigmatism was 2.58 ± 1.03 D in the single incision group and 2.70 ± 0.94 D in the paired opposite incisions group. After 12 weeks of surgery, the corneal astigmatism was reached to 2.15 ± 0.82 D in single incision group and 1.63 ± 1.21 in the paired opposite incisions group. There was a statistically significant difference in two arms of treatment regarding to surgically induced astigmatism after 3 months. The mean post-operative total and higher order aberrations and values were not significantly different in two groups.Conclusion:The results of our study showed that paired opposite incisions is an effective procedure for reducing pre-existing corneal astigmatism in cataract surgery. Paired incisions did not show any beneficial effect regarding wavefront aberrations compared with conventional single incision method.

Repeatability of aberrometric measurements in normal and keratoconus eyes using a new Scheimpflug–Placido topographer

To evaluate the repeatability of the anterior and posterior corneal wavefront aberrations using the Sirius Scheimpflug-Placido topographer in normal eyes and keratoconus eyes. Bozok University Faculty of Medicine, Yozgat, Turkey. Evaluation of diagnostic test. In eyes of healthy subjects and eyes of keratoconus patients, 3 repeated measurements were obtained using the Scheimpflug-Placido topographer. Repeatability of the corneal aberrometric data using a 7th-order Zernike expansion (6.0 mm pupil) and central corneal power (3.0 mm zone) in the anterior and posterior corneal surfaces were analyzed. The within-subject standard deviation (Sw) and the intraclass correlation coefficient (ICC) were calculated. For all modal pairs, the Sw was 0.08 μm or less for anterior and posterior corneal aberrations in both groups. The ICC of the anterior corneal surface ranged from 0.607 (pentafoil) to 0.988 (primary coma) in keratoconus eyes (n = 41) and from 0.568 (quadrifoil) to 0.856 (primary coma) in normal eyes (n = 30). The ICCs for posterior corneal surface aberrometry were 0.656 to 0.873 and 0.592 to 0.824, respectively. For anterior and posterior corneal curvatures, the Sw was 0.12 or lower and the ICC values were more than 0.93 in all cases except the posterior corneal surface reading at the 3.0 mm corneal area in keratoconus eyes (ICC 0.875). The intraexaminer repeatability of most anterior corneal aberrations with the Scheimpflug-Placido system was moderate to high in normal eyes and keratoconus eyes. The system showed moderate repeatability for the posterior corneal surface. No author has a financial or proprietary interest in any material or method mentioned.

Stability of corneal topography and wavefront aberrations in young Singaporeans

BackgroundThe aim was to investigate the differences between and variations across time in corneal topography and ocular wavefront aberrations in young Singaporean myopes and emmetropes.MethodsWe used a videokeratoscope and wavefront sensor to measure the ocular surface topography and wavefront aberrations of the total‐eye optics in the morning, midday and late afternoon on two separate days. Topographic data were used to derive the corneal surface wavefront aberrations. Both the corneal and total wavefronts were analysed up to the fourth radial order of the Zernike polynomial expansion and were centred on the entrance pupil (5.0 mm). The participants included 12 young progressing myopes, 13 young stable myopes and 15 young age‐matched emmetropes.ResultsFor all subjects considered together, there were significant changes in some of the aberrations across the day, such as spherical aberration () and vertical coma () (repeated measures analysis of variance, p < 0.05). The magnitude of positive spherical aberration () was significantly lower in the progressing myopic group than in the stable myopic (p = 0.04) and emmetropic (p = 0.02) groups. There were also significant interactions between refractive group and time of day for with and against‐the‐rule astigmatism (). Significantly lower fourth‐order root mean square of ocular wavefront aberrations were found in the progressing myopic group compared with the stable myopes and emmetropes (p < 0.01).ConclusionsThese differences and variations in the corneal and total aberrations may have significance for our understanding of refractive error development and for clinical applications requiring accurate wavefront measurements.

Evaluation of quality of vision in early stage after sub-bowman keratomileusis

To assess the quality of vision in the early stage after sub-bowman keratomileusis (SBK) for the correction of moderate and high myopia. Retrospective case series. Sixty eight myopic eyes of 35 consecutive patients in Chongqing Medal Eye Institute from May to November 2011 were enrolled in this study. All patients were evaluated at 2 weeks, 1 and 3 months postoperatively. The main measurements included visual acuity, corneal and total optical wavefront aberration, photopic and mesopic contrast sensitivity. The median values of preoperative uncorrected central visual acuity (UCVA) and best corrected visual acuity (BCVA) were 0.05 and 1.00, respectively. The median value of postoperative UCVA was 1.20. There was no significant difference between the preoperative and postoperative anterior corneal total aberration (F = 0.712, P > 0.05). Compared with preoperative value (0.47 ± 0.17)µm, the corneal high orders aberrations in 2 weeks after SBK (1.37 ± 0.72) µm increased by 3 times. The total optical aberrations in 2 weeks after SBK (0.99 ± 0.58) µm decreased to one-eighth of preoperative measurements (8.26 ± 2.93) µm. Compared with preoperative value (0.30 ± 0.12)µm, the total high order aberrations in 2 weeks after SBK (0.46 ± 0.19) µm increased by 1.5 times. Although photopic and mesopic contrast sensitivity fluctuated mildly after SBK, the measurements did not decline significantly. Compared with preoperative data, mesopic contrast sensitivity at 3 months increased 0.294 (F = 20.88,P < 0.01) and 0.296 (F = 13.64, P < 0.01) at 12 and 18 c/d, respectively. Patients could obtain good quality of vision at the early stage after SBK.

Tilt and decentration of an intraocular lens implanted in the ciliary sulcus after capsular bag defect during cataract surgery

To determine the impact of ciliary sulcus implantation after capsular bag defect on tilt and decentration of foldable intraocular lenses (IOL) measured by a novel device. This prospective noncomparative single-center investigation included patients (N = 10) older than age 60 who underwent cataract surgery with a posterior capsular bag defect and implantation of a threepiece hydrophilic aberration neutral IOL (OphthalmoPro AC 7013) in the ciliary sulcus. All eyes (N = 10) were examined using the OPD-Scan II (Nidek). Spherical aberration (Z4,0), vertical coma (Z3,-1), and horizontal coma (Z3,1) were calculated for a 5.0 mm pupil. Lens tilt and decentration was studied using a new Purkinjemeter. The mean horizontal optic tilt was 7.68° ± 5.16 (SD) and the mean vertical optic tilt was 3.01° ± 2.44 (SD). Horizontal decentration was 0.4 ± 0.33 mm (SD) and vertical decentration was 0.31 ± 0.21 mm (SD). Corneal aberrations were partially compensated by IOL- related aberrations. Both tilt and decentration of sulcus-fixated IOLs exceeded the tolerable amounts evaluated for aspheric IOLs in eye model experiments. However, these spheric IOLs showed mitigation rather than accentuation of corneal wavefront aberrations in the rare event of capsular bag defect during cataract surgery.

Subjective evaluation of intraocular lenses by visual acuity measurement using adaptive optics

We present a new method for subjectively evaluating intraocular lenses (IOLs) without implantation surgery. To illustrate the method, three types of single-piece IOL (equispherical monofocal, rotational symmetric aspheric monofocal, and diffractive bifocal) were assembled into a model eye and evaluated using an ocular adaptive optics system by a single subject. To separate the spherical aberration of the crystalline lens, the subject's corneal topography and wavefront aberrations were measured and modeled. Three levels of Zernike spherical aberration were generated and superposed on the IOLs and the subject's eye. The corrected distance visual acuity was measured by psychophysical visual procedure.

Two-Year Corneal Cross-Linking Results in Patients Younger Than 18 Years With Documented Progressive Keratoconus

To report refractive, topographic, aberrometric, and tomographic outcomes 24 months after corneal cross-linking (CXL) in patients up to 18 years of age with progressive keratoconus. Prospective, interventional case series. Forty eyes underwent riboflavin-ultraviolet A-induced CXL. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), sphere and cylinder, topography, aberrometry, tomography, and endothelial cell counts were evaluated at baseline and at 1, 3, 6, 12, and 24 months. Mean logarithm of the minimum angle of resolution baseline UCVA and BSCVA were 0.79 ± 0.21 and 0.39 ± 0.10, respectively. Mean UCVA and BSCVA at 2 years were 0.58 ± 0.18 and 0.20 ± 0.09, respectively. The improvement in UCVA and BSCVA was significant throughout the postoperative follow-up (P < .05). Mean spherical equivalent refraction showed a significant decrease of 1.57 diopters (D) at 24 months (P = .02). Mean baseline simulated keratometry was 46.32 D in the flattest meridian and 51.48 D in the steepest meridian; at 2 years, the values were 45.30 D (P = .04) and 50.21 D (P = .07), respectively. For a 3-mm pupil, there was a significant reduction (P < .05) in whole eye (total), corneal, higher-order, and astigmatic wavefront aberrations at 24 months. A significant difference (P < .05) in total coma and total spherical aberration 2 years after CXL also was observed. Mean baseline pupil center pachymetry decreased significantly (P = .04) at 6 months, but recovered by 12 months and remained stable thereafter through the 2-year follow-up. Endothelial cell counts did not change significantly (P = .32). CXL improved UCVA and BSCVA in the study patients, most likely by significantly reducing corneal asymmetry and corneal as well as total wavefront aberrations.

Tear Film Aberration Dynamics and Vision-Related Quality of Life in Patients with Dry Eye Disease

Corneal and ocular wavefront aberrations were recorded together with clinical examination results and patient-reported vision-related quality-of-life evaluation results to define the relevance of dynamic optical analysis of the eye in dry eye disease (DED). Prospective and comparative clinical study. Forty DED patients and 40 age- and gender-matched control subjects. Serial measurements of ocular and corneal higher-order aberrations (HOAs) after blink were performed for 10 seconds using the KR-1 aberrometer (Topcon, Clichy, France). Vision-related health-targeted quality of life was evaluated using the Ocular Surface Disease Index (OSDI) questionnaire. The clinical examination included tear film assessment (tear film break-up time and Schirmer I test), ocular surface damage assessment with the Oxford and van Bijsterveld indexes, and Meibomian dysfunction grading. Tear osmolarity also was measured. The time course of HOAs and modulation transfer function (MTF) was compared between groups and was analyzed in comparison with the OSDI and clinical data in DED patients. The root mean square of ocular and corneal total HOAs, particularly third-order aberrations, significantly increased over the 10-second period in DED patients, whereas no change occurred in controls. Analysis of MTF revealed progressive degradation of ocular optical quality resulting from loss of contrast at intermediate and high spatial frequencies in DED patients compared with controls. The progression index for corneal HOAs was correlated with the subjective index of patient-reported visual outcomes and with objective clinical findings of tear film and ocular surface damage. Objective measurement of the time course of HOAs may constitute a new single instrument to evaluate and manage patients with DED because it reliably reflects the completeness of the disease.

The Effect of Corneal Wavefront Aberrations on Corneal Pseudoaccommodation

To determine the effect on corneal pseudoaccommodation of anterior corneal wavefront aberrations in normal corneas and corneas with prior myopic or hyperopic photorefractive keratectomy (PRK) or laser-assisted in situ keratomileusis (LASIK). Theoretical study. In 220 normal eyes, 102 myopic-PRK eyes, and 106 hyperopic-LASIK/PRK eyes, anterior corneal higher-order aberrations (HOAs, third to sixth order, 6- and 4-mm pupils) were computed from the Atlas corneal elevation data using the VOL-CT program. Using the ZernikeTool, corneal optical image quality was evaluated by the polychromatic modulation transfer function with Stiles-Crawford effect. Defocus from -3.0 diopters (D) to +3.0 D was added to corneal HOAs, and depth of focus was defined as the ranges over which the polychromatic modulation transfer function maintains 80% of the peak value (DOF80) and 50% of the peak value (DOF50). The depth of focus values between groups were compared, stepwise multiple regression was used to assess if any Zernike terms significantly contributed to the depth of focus, and correlation analysis was performed to evaluate the correlation between depth of focus and corneal HOAs. The depth of focus varied widely between corneas, especially in corneas with prior hyperopic-LASIK/PRK. For 6-mm pupil, mean depth of focus values in myopic-PRK and hyperopic-LASIK/PRK corneas were significantly greater than those for normal corneas, and for 4-mm pupil, depth of focus values in hyperopic-LASIK/PRK corneas were greater than those in normal and myopic-PRK corneas. Zernike terms significantly contributing to both DOF80 and DOF50 were fourth- and sixth-order spherical aberration and fourth- and sixth-order astigmatism in normal corneas, third-order vertical coma and fourth-order tetrafoil in myopic-PRK corneas, and third-order vertical coma and fourth-order astigmatism in hyperopic-LASIK/PRK corneas. Depth of focus had weak to moderate positive correlation with HOAs (Pearson correlation coefficient r ranged from 0.300 to 0.583). These theoretical calculations suggest that certain corneal wavefront aberrations affect corneal pseudoaccommodation. To predict corneal pseudoaccommodation, the most important Zernike term is spherical aberration in normal eyes and coma in eyes with prior laser corneal surgery.

Corneal Wavefront Aberrations in Patients Wearing Multifocal Soft Contact Lenses for Myopia Control

Purpose: The purpose of this study was to evaluate the change in corneal wavefront aberrations in young adults who have been fit with multifocal soft contact lenses for myopia progression control. Findings have been analyzed for statistical significance and clinical relevance and compared to reportedly successful Orthokeratology outcomes. Methods: The dominant eye of 40 participants (27 women, 13 men; mean age 27.3 ± 3.2 years; range 23 to 39 years) was fit with Proclear Multifocal center distance lenses (Coopervision, Pleasanton, USA) having a variety of distance powers and reading additions. Refractive errors were limited to a range of –6.00 D up to +1.00 D of sphere, and no greater than –1.00 D of cylinder. Corneal wavefront measurements were performed over 6 mm diameters with a Zeiss Atlas 9000 corneal topographer (Zeiss Meditec, Dublin, USA) prior to, and following lens fitting. Data were converted into rectangular Fourier optics terms M, J0, J45 and RMS values for each reading addition were statistically analyzed. Following evaluation of statistical significance and clinical relevance, results were compared to published data from successful Orthokeratology treatments. Results: Statistically significant changes in higher order aberrations were detected for lenses of all reading additions. Lens groups with higher Add-powers demonstrated stronger changes with increased significance. Final RMS values relating to 2nd, 3rd and 4th Zernike Orders reached clinical significance with a wavefront error of 0.10 μm, the equivalent of 0.25D. Moreover, as Add-powers increased, 3rd and 4th order aberrations likewise showed an increase. Pre-fitting astigmatism values accounted for the highest recorded aberrations and remained predominantly unchanged. Conclusion: Proclear Multifocal center-distance contact lenses were found to increase higher order wavefront aberrations in a manner dependent on their Add-power. In comparison to successful Orthokeratology outcomes, the amounts of resulting aberrations are notably different.