Mean Spherical Aberration Research Articles

Comparison of optimized surface ablation and combined customized plus optimized surface ablation in myopic eyes

Background Proscan treats errors of refraction without affecting asphericity, while customized treatment treats correction with high-order aberration (HOA). Recently, Zyoptix HD has been used in the treatment of preoperative HOA and lower-order aberrations without inducing spherical aberrations. Aim To compare the visual outcomes and HOAs after optimized surface ablation versus Zyoptix HD surface ablation for myopia. Patients and methods A prospective comparative clinically controlled study was conducted on patients who have myopia, 40 eyes of 20 patients divided into two groups. Group I: 20 eyes underwent optimized surface ablation. Group II: 20 eyes underwent customized plus optimized surface ablation. The selection of treatment was according to root mean square and spherical aberration corneal topography. All participants were examined by a slit lamp just after the operation, on the first, third, seventh postoperative day, weekly for 1 month, then biweekly for 3 months. The patients had full follow-up by best corrected visual acuity, slit lamp, Orbscan IIZ, and wavefront aberrometry using Zywave after 3 months of procedure. Results The comparison between preoperative uncorrected visual acuity and 3 months postoperative uncorrected visual acuity improved significantly in both groups but better in group II. The comparison between preoperative and 3 months postoperative root mean square in group I increased significantly, and in group II improved significantly, which is better in group II. Conclusion Zyoptix HD is superior to optimized surface ablation in the correction of low-order and high-order eye aberrations, correcting myopia and visual acuity.

Corneal High-Order Aberrations in Fuchs Endothelial Corneal Dystrophy and Subclinical Corneal Edema.

High-order aberrations (HOAs) are known to be increased in corneas with Fuchs endothelial dystrophy (FECD) and are associated with visual impairment. This case series aimed to analyze whether tomographic changes in FECD affect the HOA in the early period of the disease. In this retrospective single-center case series, 144 eyes of 85 patients were included, of which 78 eyes of 47 patients with FECD with slit-lamp biomicroscopically visible guttae but no visible corneal edema served as the study-cohort. According to Sun et al, included eyes were divided into 2 groups: group 0 (n = 28; no subclinical corneal edema) and group 1 (n = 50; subclinical corneal edema). A total of 66 healthy eyes of 38 patients served as control group. Mean values and standard deviations were calculated for the root mean square (RMS), coma, trefoil and spherical aberrations (SA) of the cornea (C), the anterior surface (CF), and the posterior surface (CB). Statistically significant differences (P < 0.001) in the RMS HOA (group 0: 0.209 ± 0.044 μm, group 1: 0.372 ± 0.122 μm) and in coma (group 0: 0.082 ± 0.054 μm, group 1: 0.214 ± 0.101 μm) and SA (group 0: -0.130 ± 0.038 μm, group 1: -0.176 ± 0.074 μm) of the CB were found in eyes in group 1 versus those in group 0. There were no statistically significant differences in HOA between the control group and eyes in group 0. FECD eyes with subclinical corneal edema demonstrated significant increase in RMS, coma, and SA of the CB. Tomographic analysis, therefore, helps in visual impairment assessment, disease progression, and decision-making for early endothelial keratoplasty in patients with FECD.

Comparison of visual outcomes and optical aberrations after SMILE with intraoperative Kappa angle adjustments between small and large Kappa angles

This study compares postoperative visual outcomes and optical aberrations after Small Incision Lenticule Extraction (SMILE) in patients with both small (S-Kappa: Kappa angle < 0.2 mm) and large Kappa (L-Kappa: Kappa angle ≥ 0.2 mm) angles. The evaluated aberrations include total higher-order aberrations (HOAs), horizontal coma (HC), vertical coma (VC), and spherical aberrations (SA), with procedures incorporating intraoperative Kappa angle adjustments. We retrospectively analyzed patient records undergoing SMILE utilizing linear mixed models (LMM). We assessed adjusted mean uncorrected distance visual acuity (UDVA), Strehl ratio (SR), total HOAs, VC, and SA at pupils of 3 mm and 6 mm for both S-Kappa and L-Kappa. The disparities between S-Kappa and L-Kappa were evaluated by LMM's adjusted mean differences. The differences in optical metrics were also assessed in eyes grouped by myopia levels: low, moderate, and high. A sensitivity analysis was conducted on a threshold of Kappa angle at 0.3 mm. Eight-five patients (169 eyes) were analyzed, and no significant pre-operative difference was found in UDVA (p = .222) or spherical equivalent (p = .433). Post-operative differences were found in SR at 3 mm pupil size (−0.06, p = .022), total HOA 3 mm (0.15, p = .022), HC 3 mm (0.04, p = .042), VC 3 mm and 6 mm (−0.08, p = .041; 0.04, p = .041). The stratified analysis for high myopia revealed significant differences in UDVA (−0.04, p = .037), HC 3 mm (0.07, p = .03), VC 6 mm (−0.21, p = .001), and SA 3 mm and 6 mm (0.07, p = .037; −0.09, p = .037). Sensitivity analysis showed no significant difference using a 0.3 mm Kappa threshold. While some optical aberrations exhibited statistical differences between S-Kappa and L-Kappa, their clinical significance is limited. Thus, a large Kappa angle might not substantially influence post-operative optical aberrations when intraoperative Kappa angle adjustments are implemented.

Patient-Reported Outcomes and Higher Order Aberrations Following Topography-Guided Femtosecond Laser-Assisted In Situ Keratomileusis.

To examine patient-reported outcomes and higher order aberrations following topography-guided laser-assisted in situ keratomileusis (LASIK). This was a prospective, nonrandomized observational study at a single academic center. Sixty eyes from 30 patients underwent bilateral topography-guided femtosecond LASIK for correction of myopia using the VisuMax 500 femtosecond laser (Zeiss; Oberkochen, Germany) and Allegretto Wave Eye-Q 400 Hz Excimer Laser (Alcon/Wavelight; Erlangen, Germany) with the Contoura topography system (Alcon; Geneva, Switzerland) for topography-modified refraction. The main outcomes of this study were higher order aberrations (HOAs) and results from the Patient-Reported Outcomes with LASIK questionnaire. There was a small, significant increase in HOA root mean square, spherical aberration, and coma at 1, 3, 6, and 12 months following topography-guided LASIK (all P < 0.05), but no change in trefoil. In addition, self-reported worry related to vision (P < 0.001) and ability to perform activities (P < 0.001) significantly improved after surgery. The prevalence of double images, glare, halos, or starbursts decreased from 73% preoperatively to 56%, and no participants reported "very" or "extremely" bothersome visual symptoms after 12 months. Dry eye symptoms per Ocular Surface Disease Index score decreased significantly at 6 (P = 0.01) and 12 (P = 0.002) months after surgery. There was a 100% satisfaction rate with visual outcomes and duration of time to improvement in vision following the procedure. Although there was an increase in HOAs following topography-guided LASIK, there were significant improvements in the presence of double images, glare, halos, and starbursts and vision-related quality-of-life metrics. Overall satisfaction rates in this study were high.

Comparative Study of Primary SMILE, SMILE Enhancement, and Femtosecond Laser-Assisted LASIK on Higher Order Aberrations and Corneal Densitometry.

To compare differences in corneal densitometry (CD) and higher order aberrations (HOAs) in eyes that underwent small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for the treatment of myopia and myopic astigmatism at postoperative months 3, 6, and 12, and to evaluate their changes in a separate cohort of eyes after SMILE enhancement. In this prospective, randomized, paired-eye clinical trial, consecutive eligible participants were randomized to undergo SMILE or FS-LASIK in either eye. Main outcome measures were CD and HOAs preoperatively and at 3, 6, and 12 months postoperatively. A separate cohort of consecutive patients who had SMILE and underwent enhancement were also included for comparison. For CD, no significant differences were found between SMILE and FS-LASIK up to month 12. For HOA measured by wavefront aberrometry, both SMILE and FS-LASIK had an increase in total root mean square (RMS) HOAs, spherical aberration (SA), and vertical coma up to month 12. SMILE had an additional increase in vertical quatrefoil, and FS-LASIK had an increase in horizontal coma at month 12. FS-LASIK had higher SA than SMILE, whereas SMILE had higher vertical quatrefoil than FS-LASIK at month 12. Central and posterior zone CD had significantly decreased after SMILE enhancement compared to after primary SMILE up to 2 years after enhancement. RMS HOAs, lower order aberrations, and SA were all increased after SMILE enhancement compared to after primary SMILE. SMILE induced lower SA but higher vertical quatrefoil than FS-LASIK at 1 year. Both SMILE and FS-LASIK had similar increases in RMS HOAs and vertical coma up to 1 year. There were no differences in CD between both groups. SMILE enhancement additionally had decreased central and posterior CD but greater RMS HOAs and SA compared to primary SMILE. [J Refract Surg. 2024;40(5):e291-e303.].

Comparative visual outcomes of the first versus second eye following small-incision lenticule extraction (SMILE)

BackgroundThis study aimed to compare the visual outcomes of the first operated eyes with those of the second operated eyes following small-incision lenticule extraction (SMILE).MethodsA total of 202 patients (404 eyes) underwent SMILE using the tear film mark centration method for myopia and myopic astigmatism correction. Baseline characteristics, objective optical quality, decentered displacement, induced corneal aberrations, and modulation transfer function (MTF) values were assessed. Linear regression analyzed the relationship between decentration and visual quality parameters, including corneal aberrations and MTF values.ResultsNo significant difference was observed in objective visual quality, efficacy, and safety indexes between the two groups (all P > 0.05). The average decentered displacement for the first and second surgical eyes was 0.278 ± 0.17 mm and 0.315 ± 0.15 mm, respectively (P = 0.002). The horizontal coma in the first surgical eyes were notably lower than in the second (P = 0.000). MTF values at spatial frequencies of 5, 10, 15, and 20 cycles/degree (c/d) were higher in the first surgical eyes compared to the second (all P < 0.05). Linear regression indicated that high-order aberrations (HOAs), root mean square (RMS) coma, spherical aberration, horizontal coma, vertical coma, and eccentric displacement were all linearly correlated. Furthermore, MTF values exhibited a linear relationship with eccentric displacement across these spatial frequencies.ConclusionsThere was no discernible difference in visual acuity, efficacy, or safety between the two operated eyes. Nonetheless, the first operated eyes exhibited reduced decentered displacement and demonstrated superior outcomes in terms of horizontal coma and MTF values compared to the second operated eyes following SMILE. The variations in visual quality parameters were linearly correlated with decentered displacement.

Visual function assessment of Chinese cataract patients after individual aspheric intraocular lens implantation according to preoperative cornea spherical aberration.

Aspheric intraocular lens (IOLs) implantation has been widely applied in cataract surgery. However, there is no consensus on the optimal guidance for the operations in IOLs implantation. This study evaluated the visual function of Chinese cataract patients six months after cataract surgery with two different guiding ideologies. We evaluated 50 patients (61 eyes) with implantation of different aspheric IOLs (SN60WF IOLs, ZCB00 IOLs, PY-60AD IOLs, AO IOLs) 6 months after cataract surgery. Twenty-four patients (30 eyes) under individual implantation were ascribed to group 1 and 26 patients (31 eyes) with randomized implantation were ascribed to the control group (group 2). Postoperatively parameters included monocular best-corrected visual acuity (BCVA), contrast sensitivity (CS), total spherical aberration Z (4, 0) at 5 mm pupil size, and patient satisfaction. The quality of life after operation was assessed through the National Eye Institute Visual Function Questionnaire-25 (NEI VFQ-25). Six months after cataract operation, the contrast sensitivity with glare of group 1 at 2.5∘ was 0.697 ± 0.027, and 0.532 ± 0.049 in group 2. Besides, there was no significant difference at any other special frequency. The mean spherical aberration Z (4, 0) at 5 mm pupil size in group 1 was 0.015 ± 0.028 um, and in group 2 was 0.043 ± 0.109 um, with a significant difference (p< 0.01). The mean scores obtained from NEI VFQ-25 were not significantly different. It is effective to implant aspheric IOLs individually according to preoperative corneal spherical aberration. Patients obtained better contrast sensitivity with glare at 2.5∘, but there was no significant difference in BCVA, contrast sensitivity at other special frequency, and subjective visual function.

Evaluation of Postoperative Total Ocular Aberrations After Bilateral Implantation of Monofocal IOL with Extended Depth of Focus in Phacoemulsification.

To evaluate postoperative visual performance and total ocular aberration in cataract patients after implantation of the TECNIS Eyhance™ intraocular lens (IOL). Our study is a prospective interventional non-comparative study that was conducted on 34 eyes of 17 patients who underwent phacoemulsification and Eyhance IOL implantation. Postoperative corrected and uncorrected near and far visual acuity and total ocular aberration were assessed 3 months after surgery. Our study included 34 eyes of 17 patients. At the third postoperative month, the mean spherical equivalent (SE) was -0.32 diopters (D) (SD ±0.62), and the mean distance-corrected near visual acuity (DCNVA) was 0.33 (SD ±0.15) and 0.42 (SD ±0.17) decimal notation (DN) monocular and binocular, respectively. The mean near distance with maximum visual acuity was 79.47 cm (SD ±7.70) and 74.76 cm (SD ±7.90) monocular and binocular, respectively. The mean postoperative minimum reading addition (add) was 1.6 D (SD ±0.47). The mean spherical aberration (SA) was 0.13 µm (SD ±0.09). The correlation of amount of spherical aberration with power of minimum reading add at 40 cm was not statistically significant (p=0.324). The TECNIS Eyhance IOL provides good intermediate visual acuity and decreases the power of the reading add needed after phacoemulsification.

Femtosecond laser-assisted in situ keratomileusis with topography-guided or asphericity-adjusted derived data: a comparative contralateral eye study

BackgroundWavefront-optimized laser-assisted in situ keratomileusis (LASIK) ablation is the most commonly performed procedure in refractive surgery, but new technologies have become available. Our goal was to compare topography-guided (Contoura) and asphericity-guided (Custom-Q) customized ablation treatments for the correction of myopia with or without astigmatism.MethodsThis prospective, randomized, double-blind, contralateral eye study included 60 eyes of 30 patients with myopia or myopic astigmatism requiring femtosecond LASIK (FemtoLASIK) treatment. For each patient, one eye was randomized to undergo Contoura treatment, and the other underwent Custom-Q abaltion. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refractive spherical equivalent (MRSE), sphere (SPH), cylinder (CYL), 6.0-mm total corneal aberration root mean square (RMS), coma (COMA), trefoil (TREF), and spherical aberration (SA) were measured and analysed after a 1-year follow-up.ResultsThe UDVA was − 0.08 ± 0.06 logMAR in Contoura eyes and − 0.08 ± 0.05 logMAR in Custom-Q eyes (p = 0.309) after 12 months. Twenty-five eyes (83%) in the Contoura group and twenty-six eyes (87%) in the Custom-Q group had a UDVA of 20/16 at the end of 12 months, and 100% of eyes in both groups reached a UDVA of 20/25 or better. Ninety and 100% of eyes in the Contoura and Custom-Q groups, respectively, achieved a residual CYL ≤0.50 D (p = 0.237). No statistically significant difference was observed between the surgical techniques in the preoperative to 1-year postoperative changes for any of the parameters evaluated (MRSE, CYL, RMS, DEF, COMA, TREF, and SA).ConclusionsThe Contoura and Custom-Q techniques yielded excellent visual and refractive results, but the evidence did not reveal any clear differences between these two methods after 1 year of follow-up.Trial registrationReBEC - Registro Brasileiro de Ensaios Clínicos [Internet]: Rio de Janeiro (RJ): Instituto de Informação Científica e Tecnológica em Saúde (Brazil); 2010 -. Identifier RBR-8rs5kt Myopia and Astigmatism Topography-guided Refractive Surgery by Contoura Method Versus Customized by Asphericity in Contralateral Eyes: A prospective Double blind Randomized Study. Available from https://ensaiosclinicos.gov.br/rg/RBR-8rs5ktDate of registration: 02/03/2020 (dd/mm/yyyy).CAAE:96778718.9.0000.5192.Issuing authority: Plataforma Brasil.CEP:2.979.279.Issuing authority: HUOC.

Corneal Asphericity Variations in Korean Myopic Children

Purpose: Corneal asphericity (Q-value) represents the difference in curvature from center to periphery of the cornea. This study evaluated horizontal and vertical asymmetry in corneal asphericity in myopic children and its relationship with various ocular parameters.Methods: This retrospective study included 47 eyes in 24 myopic Korean children. Corneal parameters, such as corneal asphericity and thickness, apical radius of curvature, and high order aberrations including total root mean square (RMS), spherical aberration, coma, and trefoil were analyzed by Pentacam. Axial lengths (ALs) and anterior chamber depths (ACDs) were measured by IOL master. From these values, characteristics of corneal asphericity differences between nasal-temporal and superior-inferior quadrants in myopic children and their relationship with other ocular parameters were evaluated.Results: The mean Q-value (8 mm) was -0.34 ± 0.10, representing a prolate corneal shape. The mean superior-inferior Q-value differences (8 mm) was 0.23 ± 0.17, which was greater than the mean nasal-temporal Q-value differences (8 mm) measured as 0.15 ± 0.13. The mean Q-value (8 mm) was not significantly related to AL or ACD, and Q-values in each quadrant (8 mm) also showed no significant relationship with corneal thickness in each corresponding quadrant. The nasal-temporal Q-value differences (8 mm) had a positive relationship with total RMS (p = 0.001) and a negative relationship with oblique trefoil (p = 0.045) and spherical aberration (p = 0.007). The superior-inferior Q-value differences (8 mm) showed a negative relationship with vertical trefoil (p = 0.003).Conclusions: The results of the study showed a variation of nasal-temporal and superior-inferior Q-value differences, and the relationship between corneal shape and other ocular dimensions in myopic Korean children. Further study with large data set is merited to ascertain the epidemiologic data of Asian ethnicity.

36-Month Outcomes of Mechanical and Transepithelial PTK Epithelium Removal Techniques Prior to Accelerated CXL for Progressive Keratoconus.

To compare the 36-month visual, refractive, and topographic results and the optical quality of the cornea between mechanical and transepithelial phototherapeutic keratectomy (PTK) epithelium removal techniques prior to the accelerated corneal cross-linking (CXL) procedure in patients with progressive keratoconus. Keratoconic eyes that received either mechanical epithelium removal or transepithelial PTK epithelium removal prior to accelerated CXL with 36 months of follow-up were included. The uncorrected (UDVA) and corrected (CDVA) distance visual acuity, spherical equivalent (SE), manifest astigmatism, flat keratometry (K1), steep keratometry (K2), maximum keratometry (Kmax) readings, thinnest corneal thickness (TCT), topographic astigmatism, point spread function (PSF), and aberrometric parameters including root mean square higher order aberrations (RMS HOAs), vertical coma, and spherical aberration (SA) were assessed preoperatively and 12, 24, and 36 months postoperatively. One hundred ten eyes of 110 patients with keratoconus were included (mechanical epithelium removal group: 69 eyes, transepithelial PTK epithelium removal group: 41 eyes). After the CXL procedure, the mean UDVA, CDVA, manifest astigmatism, RMS HOAs, SA, vertical coma, and PSF improved significantly throughout the follow-up visits in both groups (P < .05 for all variables). The improvement in the mean UDVA, CDVA, manifest astigmatism, K1, K2, Kmax, RMS HOAs, SA, vertical coma, and PSF were significantly better in eyes that underwent transepithelial PTK epithelium removal when compared to eyes that underwent mechanical epithelium removal during the follow-up period (P < .05 for all variables). Transepithelial PTK-assisted accelerated CXL seems to be more efficient in improving the visual acuity and the optical quality while stabilizing the cornea compared to the accelerated CXL with mechanical epithelium removal in patients with progressive keratoconus. [J Refract Surg. 2022;38(3):191-200.].

Repeatability and reproducibility of corneal higher-order aberrations measurements after small incision lenticule extraction using the Scheimpflug-Placido topographer

BackgroundTo evaluate the precision of corneal higher-order aberrations measurements after small incision lenticule extraction (SMILE) using the Sirius Scheimpflug-Placido topographer (CSO, Italy).MethodsSeventy-five eyes from 75 postoperative subjects were included in this prospective study. Three consecutive corneal aberrometric measurements were obtained with the Scheimpflug-Placido topographer by two experienced operators to assess intra- and inter-observer reproducibility. The within-subject standard deviation (Sw), test-retest repeatability (TRT) and the intraclass correlation coefficient (ICC) were calculated.ResultsFor intraobserver repeatability of anterior and total corneal aberrations, all ICCs were more than 0.922, except for trefoil (0.722 to 0.768). The ICCs of total root mean square (RMS), coma Z (3, ± 1), and spherical aberration Z (4, 0) were over 0.810 while higher-order RMS, trefoil Z (3, ± 3), and astigmatism II Z (4, ± 2) were below 0.634 for posterior corneal surface aberrations. All Sw values for all types of aberrations were equal to or below 0.07 μm. Regarding interobserver reproducibility, all TRT values were no more than 0.12 μm, 0.05 μm, and 0.11 μm for anterior, posterior, and total corneal aberrations, respectively. The ICC values ranged from 0.875 to 0.989, from 0.686 to 0.976 and over 0.834 for anterior, posterior, and total corneal aberrations, respectively.ConclusionsThe repeatability of measurements of anterior and total corneal aberrations with the Sirius system in corneas after SMILE surgery was high, except for trefoil. There was some variability in posterior corneal aberrometric measurements. High reproducibility of corneal aberrometric measurements was observed between measurements of both examiners, except for trefoil, with poor to moderate reproducibility.

Fluid reservoir thickness and aberration relationship in keratoconic eyes with scleral lenses.

To investigate the effect of varying the fluid reservoir (FR) thickness of scleral lenses (SL) on corrected distance visual acuity (CDVA), contrast sensitivity (CS) and higher-order aberrations (HOAs) in keratoconic eyes. Forty eyes with keratoconus were fitted with a diagnostic Boston Sight SL having three different FR thicknesses. CDVA, CS and HOAs were measured before and after 30min of lens wear. An i-Trace aberrometer and anterior segment optical coherence tomography (AS-OCT) were used to measure HOAs and FR thickness, respectively. Statistically significant improvements in CDVA and CS were seen with different FR thickness lenses (p<0.01). Baseline CDVA (0.22±0.15) improved to 0.03±0.06, 0.04±0.07 and 0.07±0.08 with low, standard and high FR lenses, respectively. Post-hoc testing showed better CDVA with low (p=0.006) and standard FR (p=0.009) lenses compared to high FR lenses. Before lens wear, CS was 1.27±0.27, which improved to 1.67±0.11, 1.73±0.12 and 1.66±0.89 with low, standard and high FR lenses, respectively. Lenses with standard FR showed better CS compared with those having low (p=0.009) and high FRs (p<0.001). A statistically significant reduction of higher order-root mean square aberrations (HO-RMS), coma, spherical aberration, secondary astigmatism and trefoil were found with all FR thickness lenses compared to baseline (p<0.01). No significant difference was noted between lenses (p=0.01). All three lenses corrected almost equal amount of HOAs. A moderate positive correlation was observed between CDVA and HO-RMS (r=0.61, p<0.001) for low FR lenses. BostonSight SCLERALs were found to be very effective in improving vision, CS and reducing HOAs in keratoconus. Lenses with varying FR thickness showed equal effectiveness in visual performance and reducing HOAs. FR thickness should be considered an important factor to provide better vision and CS by minimising HOAs, as well as to maintain the normal physiology of eyes with keratoconus.

Effect of intracorneal ring segment implantation on high order aberrations comparing patients with eccentric versus central keratoconus.

To assess potential differences between central and eccentric cones in the aberrometric corneal profile and in visual and keratometric outcomes 6 months after intracorneal ring segment (ICRS) implantation for keratoconus. This study compared two groups consisting of 12 patients each, with central or eccentric keratoconus who were treated with femtosecond laser-assisted Keraring implantation. Uncorrected (UDVA) and corrected (CDVA) distance visual acuity, keratometric readings and higher order aberrations (HOAs) including high order aberrations root mean square (HOARMS), coma, spherical aberration and trefoil were measured preoperatively and 6 months after ICRS implantation. Trefoil and spherical aberration were significantly reduced after ICRS implantation compared to preoperative values in eccentric keratoconus (Trefoil, p = 0.0049; Spherical aberration, p < 0.0001). In central keratoconus spherical aberration was reduced not significantly after ICRS implantation compared to preoperative values (p = 0.087). Coma showed a significant reduction in central (p = 0.0001) and in eccentric keratoconus (p = 0.0001). The reduction of spherical aberration in central keratoconus was significantly positively correlated to improvement in UDVA (Pearson's correlation coefficient, r = -0.66; p = 0.02). In eccentric keratoconus there was a significant positive correlation between reduction of trefoil and improvement in UDVA (Spearmans R, r = -0.69; p = 0.01). Patients both with central and eccentric keratoconus benefit from ICRS implantation. Specifically, our data provide a slightly higher gain in visual performance for eccentric cones 6 month after ICRS implantation, which is accentuated by a greater reduction in spherical aberration and trefoil. Improvements in UDVA are positively correlated with reductions in HOAs.

Greater higher order aberrations induced by toric orthokeratology versus soft toric multifocal contact lens wear.

Spherical orthokeratology and soft multifocal contact lenses are commonly used for myopia control and correction, but have been shown to increase spherical aberration, coma and total higher order root mean square (HORMS) aberrations. There are limited myopia control contact lens options for patients with moderate to high astigmatism. The purpose of this study was to quantify changes in higher order aberrations (HOA) in myopic astigmatic eyes fitted with toric orthokeratology (TOK) and soft toric multifocal (STM) contact lenses. Ocular wavefront aberrations were measured in both eyes of 30 adult subjects and are reported through the 6th radial order over a 5mm, dilated pupil. All eyes met refractive criteria of myopia (-5.00 D to plano) and cylinder (-3.50 to -1.25 D). Three measurements were taken at baseline and after 10±2days of lens wear (TOK, STM). Sixteen subjects achieved logMAR high contrast visual acuity of 0.30 or better in both eyes and were included in this analysis. Repeated measures analysis of variance and post-hoc paired t-tests were used, as appropriate, with Benjamini-Hochberg correction. Higher order root mean square, spherical aberration (C12), and coma RMS (C7, C8) increased with TOK (0.641 [0.222], 0.409 [0.157], 0.426 [0.187] µm, respectively) and STM (0.481 [0.107], 0.223 [0.139], 0.320 [0.130] µm, respectively) from baseline (all p<0.001). TOK was elevated compared to STM for HORMS (p=0.03), spherical aberration (p=0.001) and coma RMS (p=0.04). Toric orthokeratology induced more HORMS, spherical aberration and coma RMS than STM in myopic astigmats; however, both lens types showed an increase in HOA compared to baseline, which placed patients outside the age and pupil size matched normative ranges. While the optical changes that accompany these modalities are helpful for myopia management, the induction of HOAs may have unintended consequences on visual performance.

The Effect of Chalazion Excision on Corneal Aberrometric and Densitometric Values.

Objectives:The aim of this study was to investigate the effect of chalazion excision on corneal aberrations and corneal densitometry.Methods:Thirty-six patients with a chalazion in 1 eyelid and 40 healthy subjects were included in the study. Corneal aberration parameters of total root mean square (RMS), RMS high-order aberration (HOA), horizontal trefoil, oblique trefoil, horizontal coma, vertical coma, and spherical aberration values were measured using Scheimpflug corneal topography (Pentacam HR; Oculus Optikgeräte GmbH, Wetzler, Germany). Corneal densitometry values measured from 4 regions of the cornea (0–2, 2–6, 6–10, and 10–12 mm) and 4 corneal depths (anterior, central, posterior, and total) were recorded. Preoperative measurements of the patients (Group 1), postoperative first-month measurements (Group 2), and control group (Group 3) measurements were compared.Results:The total RMS measurement was 1.64±0.48 μm in Group 1, 1.35±0.32 μm in Group 2, and 1.17±0.38 μm in Group 3 (Group 1–2: p=0.007, Group 1–3: p<0.001, Group 2-3: p=0.173). The mean spherical aberration value was 0.183±0.057 μm in Group 1, 0.157±0.048 μm in Group 2, and 0.144±0.050 μm in Group 3 (Group 1–2: p=0.104, Group 1-3: p=0.004, Group 2–3: p=0.781). The total corneal densitometric measurement was 15.95±1.80 gray scale units (GSU) in Group 1, 14.76±1.76 GSU in Group 2, and 14.33±1.49 GSU in Group 3 (Group 1–2: p=0.01, Group 1–3: p<0.001, Group 2–3: p=0.804).Conclusion:It was observed that some corneal aberration and corneal densitometry values were higher in patients with a chalazion compared with those of healthy individuals, and there was a decrease in corneal aberration and densitometry values after surgical excision.

The Effect of Cone Localization on Higher Order Aberrations After Corneal Crosslinking for Keratoconus.

Objectives:This study was designed to evaluate the effects of corneal collagen cross-linking (CXL) on topographic parameters, visual acuity, and corneal high-order aberrations according to the preoperative cone location in keratoconus.Methods:This retrospective study assessed patients with keratoconus who underwent CXL between March 2016 and February 2019. Patients with a history of corneal surgery, corneal hydrops, corneal scar tissue, delayed epithelial healing, and a corneal thickness of <400 μm were excluded. The included eyes were divided into 2 groups according to the preoperative cone location: maximum K in the central 3-mm optical zone (group 1) or the central 3-mm to 5-mm optical zone (group 2). The preoperative and postoperative 24-month, best-corrected visual acuity (BCVA), intraocular pressure, K max, symmetry index front, corneal thickness, and high order aberration findings were recorded.Results:The study included 67 eyes of 67 patients with keratoconus: 39 in group 1, and 28 in group 2. There were statistically significant differences between the groups in the preoperative BCVA values (p=0.04). There was no significant difference between the preoperative and postoperative mean K max between the 2 groups (p=0.08). The mean difference in corneal thickness between preoperative and postoperative measurements was significantly lower in group 2 than in group 1 (p=0.03). The preoperative and postoperative mean spherical aberration was significantly higher in group 1 than in group 2 (p=0.001 and p=0.005, respectively).Conclusion:The preoperative cone location in keratoconus may affect CXL outcomes. At the end of the second year, CXL was found to have a similar efficacy on visual acuity and keratometry parameters in the central and paracentral cone groups, and the recovery in terms of a spherical aberration among high-order aberrations after CXL in the central cone group was better than that of the paracentral cone group.

The short term effect of trehalose and different doses of sodium hyaluronate on anterior corneal aberrations in dry eye patients

Aim To evaluate the short-term effect of 0.15% sodium hyaluronate (SH), 0.20% SH, and Trehalose + 0.15% SH on anterior corneal aberrations in dry eye patients. Methods 76 eyes of 76 dry eye patients were divided into three groups. Non-preserved 1.5 mg/mL SH was administered in group 1, non-preserved 2.0 mg/mL SH was administered in group 2, and non-preserved trehalose 30 mg/mL and 1.5 mg/mL SH was administered in group 3. Aberrometry measurements were performed before and 10 min after application of the artificial tear drop. Using the Pentacam Scheimpflug imaging system, total root mean square (RMS), lower-order aberration (LOA), higher-order aberrations (HOAs), spherical aberration (SA), trefoil, and coma aberrations were investigated. Results In each group; the RMS of total, LOA, HOAs, and spherical aberration were significantly decreased after the artificial drop instillation, compared with those of them at baseline; and in groups 1 and 2, vertical trefoil term was also significantly increased, compared with those of them at baseline. According to intergroup analyzes, there was no significant outcome. Conclusions It was observed that three artificial tears reduced the anterior corneal aberrations, in a 10-min period. The short-term effect of three artificial tears on the anterior corneal aberration was similar.

Repeatability and Interchangeability of Topometric, Anterior Chamber and Corneal Wavefront Data Between Two Scheimpflug Camera Devices.

PurposeThis study aims to assess the intra-operator repeatability and correlation of the Pentacam HR (device 1) and Sirius (device 2) in measuring anterior segment parameters and to evaluate the agreement of their readings and therefore their interchangeability in a clinical setting.MethodsThis is a prospective non-randomized study was conducted on the right eyes of 102 subjects coming to Eye World Hospital, Giza, Egypt. With each machine, four scans were taken by a single examiner. Each device was used to measure keratometric indices, corneal thickness, anterior chamber depth, anterior chamber angle, corneal diameter and corneal optical aberrations.ResultsBoth devices show high repeatability for corneal thickness, corneal diameter, anterior chamber depth and keratometric indices (except for maximum keratometry, where device 1 shows high repeatability and device 2 shows low repeatability). On the other hand, both devices show poor repeatability for anterior chamber angle, Q-values, root mean square, spherical, coma and trefoil aberrations. The readings of the two devices are strongly correlated as regards only keratometric indices, corneal thickness and anterior chamber depth. In addition, the readings of the devices are in good agreement as regards only keratometric indices (except maximum keratometry), corneal thickness, anterior chamber depth, anterior chamber angle, root mean square, spherical and trefoil aberrations.ConclusionBoth devices showed variable intra-observer repeatability, with the device 1 showing slightly higher repeatability. Despite the similarity between some of the readings of the two devices, caution is advised before considering them interchangeable. We therefore do not recommend using them in alternation in refractive surgery.

Repeatability and reliability of measurements obtained by the combined Scheimpflug and Placido-disk tomography in different stages of keratoconus.

The objective of this study is to evaluate the repeatability and reliability of corneal parameters in different stages of keratoconus patients using a combined Scheimpflug-Placido disc analysis system. In this prospective study, three consecutive measurements were performed by the same observer using Scheimpflug-Placido disc anterior segment analysis device in keratoconus patients. Flattest and steepest simulated keratometry and corneal volume, corneal aberrations, thinnest corneal thickness, symmetry index, keratoconus vertex and Baiocchi-Calossi-Versaci index were recorded. Keratoconic eyes were divided into four stages using the Amsler-Krumeich classification. Repeatability was evaluated using within the subject standard deviation, repeatability index (Ri) and coefficient of variation; reliability was evaluated by intraclass correlation coefficient (ICC). Pearson correlation coefficients were used to assess the correlation between the parameters evaluated. Two hundred sixty-one eyes of 261 keratoconus patients were included in the study. The repeatability for all corneal curvature parameters decreased as the keratoconus severity increased, and there is a positive correlation between keratometry of the apex and corneal curvature parameters (p < 0.05) except mean simulated keratometry. The corneal aberrations were repeatable in all keratoconus subgroups (Ri < 0.34 μm). There are also positive correlations between keratometry of apex and corneal aberrations (p < 0.05) except total high-order root mean square and spherical aberration. The reliability was excellent (ICC > 0.90) for all indices except keratoconus vertex back. The parameters used in the diagnosis and follow-up of keratoconus in the Sirius corneal tomography system may differ more than expected at stages 3 and 4 of the disease. Awareness of this situation may be helpful in planning follow-up and treatment.