Vertical Coma Aberration Research Articles

Analysis of third and fourth corneal high-order aberrations before and after small incision lenticule extraction (SMILE) in myopic and myopic astigmatic eyes using ray tracing aberrometry

BackgroundAim is to analyze alterations in third and fourth corneal higher-order aberrations using a ray tracing aberrometer (iTrace) induced by SMILE (small incision lenticule extraction) refractive surgery on Algerian patients; and also to investigate how corneal aberrations vary with spherical equivalent (SE), corneal central thickness (CCT), and age. Design Prospective, non-randomized case series that were carried out at the Chiali Smile Center, Algiers, Algeria.ParticipantsA total of 219 eyes from 110 myopic patients, with and without astigmatism, successfully concluded the ultimate follow-up. Participants exhibited an average age of 32.48 years, with preoperative mean corneal high-order aberrations (CHOA) measuring 0.005 ± 0.036 μm.MethodsA tracking trend analysis of high-order aberrations (HOAs) was conducted on the three groups of patients, assessing total corneal high-order aberrations after SMILE over periods of two, six, and twelve months.ResultsA substantial increase in total corneal high-order aberrations following SMILE, with a P value < 0.05. Conversely, there was a noteworthy and significant decrease in vertical trefoil for all groups (P value = 0.000). Interestingly, the corneal higher-order aberrations were more pronounced after two months compared to the six and twelve-month intervals. Spherical aberration demonstrated a significant increase with the extent of preoperative myopia and preoperative spherical equivalent both before and after SMILE surgery (P < 0.05), particularly in cases of high myopia. Moreover, there were significant reductions in preoperative and postoperative vertical coma (P = 0.047, P = 0.004, respectively) corresponding to the degree of preoperative myopia, with a more substantial decrease in vertical coma observed in cases of low myopia.ConclusionIn the post-SMILE period, a notable increase in vertical coma and spherical aberrations was observed, accompanied by a significant decrease in vertical trefoil across all eyes. These aberration changes were identified to be closely associated with the spherical equivalent.

Comparison of objective visual quality between SMILE and FS-LASIK in moderate-to-high myopia.

This study aims to compare the changes in the corneal wavefront aberrations and the objective visual quality resulting from two types of eye surgery-small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK)-in patients with moderate-to-high myopia. A prospective analysis was performed on 98 eyes of 51 patients who underwent SMILE. Additionally, 88 eyes of 45 patients who underwent FS-LASIK were analyzed. All patients underwent ocular examination preoperatively and at 1 day, 1 week, 1 month, and 3 months postoperatively. Corneal aberrations and objective visual quality were measured using the Optical Quality Analysis System II (OQAS II) and Optical Path Difference Scan III (OPD-Scan III). At postoperative 1 day and 1 week, there was a statistically significant difference in uncorrected distance visual acuity (UDVA) between SMILE and FS-LASIK (P < 0.05). Postoperative spherical (S), cylinder (C) and spherical equivalent refraction (SE) were similar between the two groups (P > 0.05). In both groups, the absolute magnitude of total higher-aberrations (tHOA), piston, vertical tilt, vertical coma, and spherical aberration (SA) increased after surgery compared to preoperative values (P < 0.05). There was no significant difference in Δhorizontal tHOA, Δhorizontal tilt, Δhorizontal coma, and Δhorizontal trefoil between the two groups (P > 0.05), and the FS-LASIK had higher Δvertical trefoil and ΔSA (P < 0.05) but lower Δpiston, Δvertical tilt, and Δvertical coma than the SMILE group (P < 0.05). There was a rise in objective scattering index (OSI) and a decline in both modulation transfer function (MTF) cutoff and Strehl ratio (SR) after surgery compared to preoperative values in both groups (P < 0.05). There was a statistically significant difference in the OSI at 1 day and 3 months between the two groups (P < 0.05). Postoperative MTF cutoff and SR were similar between the two groups (P > 0.05). Postoperative OSI was positively correlated with corneal tHOA (0.261 ≤ R ≤ 0.483, P < 0.05) and was negatively correlated with vertical tilt and vertical coma (-0.315 ≤ R ≤ -0.209, P < 0.05) in both groups. While both SMILE and FS-LASIK can effectively correct moderate-to-high myopia, there is an increase in corneal aberrations and a postoperative delay in objective visual quality. The cornea may require a longer recovery period in the SMILE. OPD-Scan III combined with OQAS II is a useful supplementary inspection for assessing the optical quality following refractive surgery.

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.

Wavefront Changes during a Sustained Reading Task in Presbyopic Eyes.

The objective of this study was to assess the effect of sustained reading on the temporal changes in the wavefront error in the presbyopic eye. The wavefront aberration of the eyes was measured using an IRX3 Shack-Hartmann aberrometer before and after (immediately, 5 min, and 10 min after) a reading task. Temporal changes in C20, C40, and C3-1 coefficient values of the eyes were plotted, showing a predominant number of V-shaped patterns (for C40 and C3-1) and inverse V-shaped patterns (for C20) among the study group, and the percentages (between 27 and 73%) were reported. The median of the total RMS of aberrations and the RMS of HOA (higher-order aberrations), which included comatic (3rd order) and spherical-like aberrations (4th and 6th order), increased immediately after finishing the near-vision reading task and then decreased. The median of RMS of comatic aberrations had a similar pattern of variations, while the median of RMS of spherical-like aberrations displayed an opposite pattern. Simulating the aberration changes due to lens decentration caused by relaxed zonules during 4 D accommodation in an eye model demonstrated that the expected range of changes for the vertical coma and spherical aberrations are in the order of 0.001 and 0.01 μm, respectively, which could justify why the observed changes were not statistically significant. The observed dynamic changes in HOA might be linked to the biomechanical characteristics and alterations in the displacement of the crystalline lens following prolonged near-vision tasks in presbyopic people. Although some predominant patterns under some conditions were shown, they exhibit considerable inter-subject and inter-ocular variability. This might be due to slight misalignments while fixating on the internal extended object in the aberrometer.

Comparative Analysis of Corneal Higher-Order Aberrations after Laser-Assisted In Situ Keratomileusis, Photorefractive Keratectomy, and Small Incision Lenticule Extraction with Correlations to Change in Myopic Q-Value and Spherical Equivalent with and without Astigmatism.

Background: This retrospective chart review compared the higher-order aberrations (HOAs) among photorefractive keratectomy (PRK), laser-assisted in situ keratomileusis (LASIK), and small incision lenticule extraction (SMILE) alongside changes in spherical equivalent (SEQ) and corneal shape (Q-value). Methods: Analyzing 371 myopic eyes, including 154 LASIK, 173 PRK, and 44 SMILE cases, Pentacam imaging was utilized pre-operatively and at one-year post-operative visits. Results: All procedures resulted in 100% of patients achieving an uncorrected distance visual acuity (UDVA) of 20/40 or better, with 87% of LASIK and PRK, and 91% of SMILE patients having 20/20 or better. Significant increases in HOAs were observed across all procedures (p < 0.05), correlating positively with SEQ and Q-value changes (LASIK (0.686, p < 0.05), followed by PRK (0.4503, p < 0.05), and SMILE (0.386, p < 0.05)). Vertical coma and spherical aberration (SA) were the primary factors for heightened aberration magnitude among the procedures (p < 0.05), with the largest contribution in SMILE, which is likely attributed to the centration at the corneal apex. Notably, PRK showed insignificant changes in vertical coma (-0.197 µm ± 0.0168 to -0.192 µm ± 0.0198, p = 0.78), with an increase in oblique trefoil (p < 0.05). Conclusions: These findings underscore differences in HOAs among PRK, LASIK, and SMILE, helping to guide clinicians.

Incidence and factors for pseudoaccommodation after monofocal lens implantation: the Monofocal Extended Range of Vision study.

To screen patients with a monofocal intraocular lens (IOL) for incidence of unaided 20/40 and 0.3 LogMAR for distance and near (pseudoaccommodation) and to find factors for pseudoaccommodation. University Hospitals Sussex NHS Foundation Trust, Brighton, United Kingdom. Prospective study. This was a single-eye study ( ClinicalTrials.gov : NCT04011696). At 3 to 9 months, refraction, uncorrected and corrected distance and uncorrected near visual acuity (logMAR), spherical equivalent (SEQ), mesopic pupil size (PS), total eye spherical (Z 40 ), vertical coma (Z 3-1 ) aberrations, reading speed and smallest print size were assessed. Refractive astigmatism (RA) was classified as against-the-rule, with-the-rule, oblique and no astigmatism. Data on preoperative axial length (AL) and anterior chamber depth (ACD) were collected. 29 patients (9.6%, 95% CI, 6.5-13.5) had pseudoaccommodation. In cases vs controls, median SEQ, PS, total Z 40 , Z 3-1 , reading speed, smallest print size, preoperative ACD, preoperative AL were: -0.39 vs 0.0 diopters; 3.62 vs 4.10 mm; 0.01 vs 0.02 μm; 0.018 vs 0.022 μm; 106 vs 133 words per minute; 0.30 vs 0.50 logMAR; 2.94 vs 3.13 mm, 23.4 vs 23.7 mm, respectively. RA was not different between the groups. Univariate analysis revealed preoperative ACD (odds ratio [OR], 0.38, 95% CI, 0.16-0.94, P = .04), SEQ (OR, 0.61, 95% CI, 0.42-0.88, P = .01), total Z 40 (OR, 0.0003, 95% CI, 0.00-0.39, P = .03) and PS (OR, 0.39, 95% CI, 0.22-0.69, P < .041) to be significant. Whereas multivariable logistic regression identified: preoperative AL (OR, 0.62, 95% CI, 0.42-0.91, P = .02), SEQ (OR, 0.49, 95% CI, 0.31-0.78, P = .01), Z 40 (OR, 0.00, 95% CI, 0.0-0.01, P = .01) and PS (OR, 0.41, 95% CI, 0.23-0.75, P = .01) to be significant. A combination of low myopic SEQ, lower Z 40 , shorter preoperative AL, and smaller PS increases the chances of pseudoaccommodation.

Evaluation of corneal topography and higher order aberrations of the fellow eye in unilateral keratoconus

Purpose To assess parameters of corneal topography and higher order aberrations (HOAs) data in the apparently normal contralateral eyes of unilateral keratoconus (KC) cases in comparison with normal eyes of healthy individuals. Patients and methods This observational case-control study included 70 eyes divided into two equal groups; group A was the fellow eyes of unilateral keratoconus patients and group B included the normal control eyes. They were examined by Schimpflug camera to extract the study parameters (keratometry indices, the inferior-superior(I-S) difference at 4 mm, posterior elevation (PE), front and back difference, thickness progression index, corneal pachymetry, multimetric D index (D index), topometric indices and Zernike analysis). Results In comparing the study data between Groups A and B, we demonstrated that ISV, IVA, and CKI had no difference between the two groups. But other topometric parameters showed statistically significant differences between the two groups. Assessment of corneal aberrations revealed that the RMS HOA, vertical coma, and spherical aberrations were associated with significant increases in the apparently normal eyes of unilateral KC cases in comparison with healthy individual eyes (P&lt;0.001). Conclusion Fellow eyes of unilateral KC cases seem not to be totally normal. And so, it is recommended to regularly examine these eyes at close intervals to catch up any abnormality and to avoid KC progression.

Asymmetric intracorneal ring segments in the treatment of snowman phenotype keratoconus

To evaluate refractive, aberrometric, topographic, and topometric outcomes of asymmetric intracorneal ring segment (ICRS) implantation in snowman phenotype (asymmetric bow-tie) keratoconus. This retrospective, interventional study included eyes with snowman phenotype keratoconus. Two asymmetric ICRSs (Keraring AS) were implanted after femtosecond laser-assisted tunnel formation. Visual, refractive, aberrometric, topographic, and topometric changes after asymmetric ICRS implantation were evaluated with a mean follow-up of 11 months (6-24 months). Seventy-one eyes were analyzed in the study. Keraring AS implantation corrected refractive errors significantly. The mean spherical error decreased from -5.06±4.23 D to -1.62±3.45 D (P=0.001), and the mean cylindrical error decreased from -5.43±2.48 D to -2.44±1.49 D (P=0.001). Uncorrected distance visual acuity improved from 0.98±0.80 to 0.46±0.46 Log MAR (P=0.001), and corrected distance visual acuity improved from 0.58±0.56 to 0.17±0.39 Log MAR (P=0.001). Keratometry (K) maximum, K1, K2, K mean, astigmatism, and corneal asphericity (Q-value) showed a significant decrease (P=0.001). Vertical coma aberration decreased significantly from -3.31±2.12μm to -2.56±1.94μm (P=0.001). All topometric indices of corneal irregularities were significantly reduced postoperatively (P=0.001). Keraring AS implantation in snowman phenotype keratoconus demonstrated good efficacy and safety. Clinical, topographic, topometric, and aberrometric parameters improved significantly after Keraring AS implantation.

Intraocular composition of higher order aberrations in non-myopic children.

This study examined anterior corneal, internal ocular, and total ocular higher order aberrations (HOA's), and retinal image quality in a non-myopic, paediatric cohort. Anterior corneal aberrations were derived from corneal topography data captured using a Placido disk videokeratoscope (E300, Medmont International), and whole eye HOA's were measured using a Hartmann-Shack wavefront sensor (COAS-HD, Wavefront Sciences). The associations between HOA's and age, sex, refractive error, and axial length were explored using correlation analyses. Data for 84 children aged between 5 and 12 years (mean ± standard deviation spherical equivalent refraction (SER), +0.63 ± 0.35 D; range 0.00 to +1.75 D) were included, and an eighth order Zernike polynomial was fit for 4 and 6 mm pupil diameters for both the anterior corneal and total ocular HOA's, from which internal ocular HOA's were calculated via subtraction following alignment to a common reference axis (pupil centre). Internal ocular HOA's were of greater magnitude than previous studies of adolescents and adults, however partial internal "compensation" of HOA's was observed, which resulted in reduced levels of HOA's and excellent retinal image quality. Few significant associations were observed between HOA's and age, SER, and axial length (all correlations, p > 0.001), and there were minimal sex-based differences (all comparisons, p > 0.005). Coefficients for vertical coma ( and ) and spherical aberration ( and ), were most strongly associated with the visual Strehl ratio based on the optical transfer function (VSOTF), which indicated that the absolute magnitudes of these Zernike coefficients have the greatest impact on retinal image quality in this paediatric cohort. These findings provide an improved understanding of the optics and retinal image quality of children's eyes.

The Impact of Corneal Epithelial Thickening and Inhomogeneity on Corneal Aberrations After Small Incision Lenticule Extraction.

To investigate the corneal epithelial remodeling profile after small incision lenticule extraction (SMILE), the correlated explanatory variables, and its potential impact on corneal higher order aberrations (HOAs). This single-center study prospectively evaluated 75 right eyes of 75 patients scheduled for SMILE. An anterior segment optical coherence tomography device was used to automatically obtain central 6-mm corneal epithelial thickness (ET), total corneal HOAs, and individual Zernike components before and after surgery. The ET inhomogeneity over the central 3- and 6-mm cornea was quantified with coefficient of variance (CV). Both ET and CV significantly increased 1 month postoperatively (all P < .05). The stepwise multiple regression analysis showed that ET and CV were significantly correlated with preoperative ET and CV, respectively (all P < .01). The corrected spherical equivalent also significantly influenced ET and CV (all P < .01). Over the central 6-mm zone, the alterations of total corneal HOAs and individual Zernike components such as vertical coma (Z7) and spherical aberration (Z12, Z24) were significantly correlated with ET and CV (all P < .05). The SMILE-induced epithelial remodeling involved both ET and ET inhomogeneity. The modulation was associated with preoperative and treatment parameters, and exerted a significant impact on corneal HOA alterations especially over the central 6-mm cornea. Together with the amount of correction and corneal curvature gradient change, preoperative assessment of ET and ET inhomogeneity might help predict postoperative epithelial remodeling. [J Refract Surg. 2023;39(1):23-32.].

Assessment of central and peripheral accommodative lag by aberrometry

Accommodation lag is important factor for normal vision. Higher lag of accommodation may cause various ocular symptoms particularly during near tasks. In this study, the lag of accommodation was assessed in the peripheral retina and it was compared with the central accommodative lag with aberrometer. In this cross-sectional study, fifty-three young subjects with normal visual acuity and without any active ocular disease or past ocular surgery were included. Aberrations in the central and peripheral field of view up to 30° off axis from the centre in horizontal and vertical meridian in 10° steps were measured with Hartmann-Shack aberrometer with stimulation of accommodation by -2.50D lens. Accommodative stimulus and accommodative response were calculated with defocus and hence accommodative lag was obtained. Accommodative lag in the centre and periphery was compared. Repeated measure of ANOVA showed that there were significant differences in lag of accommodation in various eccentricities (F(8.912, 454.514) = 2.372, p = 0.013). Pairwise test showed that lag in the centre was similar with lag on other peripheral field of view (p > 0.05). However, accommodative lag at 10° nasal field was significantly lower than the lag at 20° temporal, 20° nasal, 30° temporaland 30° nasal (p < 0.05). Similarly, lag at 10° superior fixation was lower than lag at 20° temporal, 20° nasal, 30° temporal and 30° nasal fixations (p < 0.05). We found higher lag of accommodation in horizontal off-axis fixations in comparison to that of vertical off-axis fixations (p < 0.05). Lag of accommodation was positive correlated with vertical coma and primary spherical aberrations but negative correlated with secondary spherical aberrations (p < 0.05). Thus, Hartmann-Shack aberrometer was successfully used to assess accommodative lag in the peripheral field of view up to 60° visual field. Peripheral lag of accommodation depends up on eccentricity. Lag was found higher in horizontal off-axis fixation than at vertical fixations. Coma and spherical aberration had association with lag.

One-Year Visual Outcomes and Corneal Higher-Order Aberration Assessment of Small-Incision Lenticule Extraction for the Treatment of Myopia and Myopic Astigmatism.

We present a retrospective, single-center report of one-year visual outcomes for Small Incision Lenticule Extraction (SMILE) to treat myopia and myopic astigmatism, as well as to compare outcomes with other published literature, including results from the United States Food and Drug Administration (US FDA). A total of 405 eyes with a mean preoperative spherical equivalent of -5.54 diopters (D) underwent SMILE between April 2017 and April 2022. The outcomes measured included visual acuity, manifest refraction, vector analysis, and wavefront aberrometry at various time points, specifically pre-operative and twelve months post-operatively. Results were compared to other similar published studies of SMILE outcomes between 2012 and 2021. A total of 308 and 213 eyes were evaluated at three and twelve months, respectively. At twelve months, 79% of eyes achieved UDVA ≥ 20/20, and 99% had ≥20/40, with no patients losing ≥2 lines of vision. For accuracy, 84% of eyes were within 0.5 D of target SEQ, and 97% were within 1 D. Total corneal higher order aberrations (HOA) increased from 0.33 to 0.61 um. Significant change was found in vertical coma and spherical aberration at twelve months. SMILE remains a safe and effective treatment for myopia and myopic astigmatism. Clinical outcomes are likely to improve with increased surgeon experience and refinement of technology and nomograms.

SMILE after DALK to reduce residual refraction: two-year results.

To determine the two-year results of small incision lenticule extraction (SMILE) for correcting post-keratoplasty myopia and myopic astigmatism. In this case-series study, 10 eyes of 10 patients with a 6- to 10-year history of successful deep lamellar keratoplasty (DALK) underwent SMILE using the VisuMax laser platform. Ophthalmologic examinations and visual acuity and refraction measurement were taken pre- and 1, 3, 6, 12, and 24months postoperatively. The Pentacam and Sirius imaging were done in the first and last follow-up sessions. The mean age of the patients was 39.60 ± 7.86years. Six subjects were male. Two years after SMILE, the mean improvement in UDVA and CDVA was 3.60 ± 1.84 (P < 0.001) and 1.60 ± 2.91 (P = 0.231) LogMAR, respectively. The mean decrease in spherical equivalent, spherical error, and cylinder power was 1.92 ± 1.96 diopter (D) (P = 0.013), 0.70 ± 3.05D (P = 0.213), and 2.42 ± 2.91D (P = 0.024), respectively. The vector mean target-induced astigmatism, surgical-induced astigmatism, and difference vector were 1.30D@44˚, 1.11D@24˚, and 0.86D@73˚, respectively. Two years after SMILE, vertical coma, horizontal coma, and spherical aberration increased by 0.44 ± 0.51, 0.23 ± 0.32, and 0.02 ± 0.16µm, respectively, (all P > 0.05) while trefoil reduced by 0.29 ± 0.75µm (P = 0.428). SMILE can be an effective procedure for reducing refraction and astigmatism after DALK in patients with moderate myopia and moderate to severe astigmatism and improves the visual acuity in these patients. Axis rotation during surgery may result in under-correction of astigmatism. Refinement of SMILE treatment nomogram for post-DALK cases seems necessary.

Evaluation of Ocular Higher-Order Aberrations in First-Degree Relatives of Patients With Keratoconus.

The aim of this study was to evaluate the corneal higher-order aberrations (HOAs) in first-degree relatives of patients with keratoconus (KCN) and compare with the normal population. In this prospective comparative study, 210 eyes from 105 family members of 28 patients with KCN and 210 normal eyes of 105 controls were enrolled. In each eye, corneal topography, tomography, and aberrometry were performed and compared between the 2 groups. This study included 61 female (58.1%) and 44 male participants (41.9%) and 105 age-matched and sex-matched controls with normal topographic cornea. In 14 of 105 first-degree relatives (13.33%) of patients with KCN, KCN was diagnosed with a male preponderance (71.5% male, 28.5% female). Tomographic indices and irregularity indices in 3 and 5 mm zone in Orbscan were significantly higher in the relative group. In addition, other irregularity indices of TMS-4 topography including surface regularity index, surface asymmetry index, difference sector index, SDP, and irregular astigmatism index were significantly higher in family members of patients with KCN. The most prevalent topographic pattern in the control group was the symmetric bowtie (57.1%) and in the relative group was the asymmetric bowtie (39.5%). In addition, significantly thinnest corneal pachymetry was detected in the relative group. Root mean square of all HOAs including vertical trefoil, vertical coma, horizontal coma, horizontal trefoil, quadrifoil, and fourth-order spherical aberrations were significantly greater in the relative group than controls. Owing to the high prevalence of undiagnosed KCN susceptibility in family members with KCN, keratorefractive surgery should be considered cautiously in these individuals. In addition, comprehensive preoperative examination should be considered to detect subtle topographic and HOAs in these individuals.

Comparative study of objective visual quality between FS-LASIK and SMART in myopia.

To compare the changes in the objective visual quality of patients with low and moderate myopia postoperatively after transepithelial photorefractive keratectomy using the smart pulse technology (SMART) and femtosecond laser in situ keratomileusis (FS-LASIK). Corneal higher-order aberrations (HOAs), horizontal coma, vertical coma and spherical aberration were measured using Pentacam, and cutoff for modulation transfer function (MTF cutoff), objective scatter index (OSI) and Strehl ratio (SR) was measured using an optical quality analysis system (OQAS-II), before and after operation at 1, 3, and 6mo, and data were analyzed by repeated measurement two-way analysis of variance. The difference in uncorrected distance visual acuity between SMART and FS-LASIK was statistically significant only 1wk postoperatively. Approximately 86.36% and 80.69% of patients with spherical equivalent (SE) in ±0.50 D were observed in the SMART and FS-LASIK groups, respectively. No significant difference was observed in SE between the two groups (P=0.509). The HOAs increased postoperatively compared with those before surgery in both groups (P<0.05). No significant difference in HOA, corneal horizontal coma, spherical aberration, ΔHOA, Δhorizontal coma, and Δspherical aberration were observed between the two group (P>0.05). Corneal vertical coma and Δcorneal vertical coma in the FS-LASIK group were higher than those in the SMART group (P<0.05). The OSI of both groups at 1mo after surgery was higher than that before surgery (P<0.05). At 3 and 6mo postoperatively, the OSI in the FS-LASIK group was slightly higher than that in the SMART group (P=0.040 and 0.047, respectively). At 6mo after surgery, the MTF cutoff was statistically significant different between the two groups (P=0.026). No significant difference in SR between the FS-LASIK and SMART groups was observed at 1, 3, and 6mo postoperatively (P>0.05). The HOAs increase and visual quality is delayed in both groups postoperatively, and the long-term objective visual quality after SMART is slightly better than that after FS-LASIK.

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.].

Influence of Aberrations on Modal Decomposition for LMA Fiber Laser Systems

Understanding the mode components is of great importance to manipulate the optical modes and to improve the optical system performance. However, various forms of aberrations, stemming from misalignment and imperfect optical components and system design, degrade the performance of the modal decomposition (MD) system. Here we analyze the influence of various Zernike aberrations on MD performance in large-mode-area fiber laser systems. Using computer-generated optical correlation filter together with angular multiplexing technique, we can simultaneously measure multi-modal contents. Among the common aberrations, we find that the MD results are least sensitive to vertical astigmatism aberration. However, the vertical coma aberration and horizontal coma aberration have a large impact on MD results under the same aberration strength, which show a rather large change in modal weight and intermodal phase. Our analysis is useful to construct a precise MD system applicable for high-power optical fiber modal analysis and mode control.

Visual Acuity, Wavefront Aberrations, and Defocus Curves With an Enhanced Monofocal and a Monofocal Intraocular Lens: A Prospective, Randomized Study.

To compare uniocular and binocular visual acuity, wavefront aberrations, and defocus curves using the TECNIS Eyhance (Johnson & Johnson) and RayOne (Rayner) intraocular lenses (IOLs). In this prospective, randomized, comparative study, 50 patients (100 eyes) were randomized to receive the same IOL bilaterally (ClinicalTrials.gov Identifier: NCT04175951). Follow-up visits were at 1 and 3 to 9 months postoperatively. Primary outcome measures were uncorrected distance (UDVA) and uncorrected intermediate (UIVA) visual acuity (logMAR) at 66 cm. Secondary outcome measures were corrected distance (CDVA) and distance-corrected intermediate (DCIVA) visual acuity at 66 cm, manifest refraction, spherical (Z40) and vertical coma (Z3-1) aberrations (total, internal eye, and corneal) at normal pupil size, defocus curves, and Catquest 9SF and Glare and Halos questionnaire on Likert scale (1 = no glare and halos and 4 = continuous). Uniocular UDVA (P = .02), UIVA (P = .02), and binocular UIVA (P < .01) and uniocular (P = .01) and binocular (P < .01) DCIVA were better with the TECNIS Eyhance IOL at 3 to 9 months. At 3 to 9 months, both uniocular and binocular defocus curves were significantly broader with the TECNIS Eyhance IOL between -0.50 and -3.00 diopters (D). For total and internal eye, there was a statistically but clinically insignificant difference in Z40 with the TECNIS Eyhance IOL. Rasch scores improved (TECNIS Eyhance: 2.04 ± 1.34 to 2.91 ± 0.81 and RayOne:1.61 ± 1.35 to 2.97 ± 0.16) at 3 to 9 months. Refraction, Z3-1, glare, and halos were not different. The TECNIS Eyhance IOL provided better DCIVA and broader defocus curves than the RayOne IOL. There was no difference in CDVA or patient-reported outcomes. Although there were some differences in aberrations when measured with normal pupil size, they were not clinically significant. [J Refract Surg. 2022;38(1):10-20.].

Corneal Asphericity and Higher-Order Aberrations after FS-LASIK and Trans-PRK for Myopia.

Objective To compare the corneal asphericity and higher-order aberrations (HOAs) of femtosecond laser-assisted in situ keratomileusis (FS-LASIK) with Smart Pulse Technology (SPT) assisted transepithelial photorefractive keratectomy (Trans-PRK) for myopia and myopic astigmatism correction. Methods This prospective study analyzed 88 eyes of 44 patients treated with FS-LASIK and 64 eyes of 32 patients treated with Trans-PRK. All eyes had low to moderate myopia with or without astigmatism (spherical equivalent (SE) <−6.00 diopters). The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), SE, asphericity (Q value) of the anterior corneal surface, index of surface variance (ISV), corneal higher-order aberrations (HOAs), vertical coma (Z3−1), horizontal coma (Z31), and spherical aberration (Z40) over a 6 mm diameter central corneal zone diameter were evaluated preoperatively and 1, 3, and 6 months postoperatively. Results At 6 months, the UDVA and SE were −0.14 ± 0.06 and 0.33 ± 0.33D in FS-LASIK and −0.15 ± 0.06 and 0.35 ± 0.37D in Trans-PRK. There was no difference between the two groups in the postoperative UDVA and SE (P > 0.05). After FS-LASIK and Trans-PRK, the Q values in the 6, 7, 8, and 9 mm zones and ISV of the anterior corneal surface significantly increased (P < 0.001). At 1, 3, and 6 months after surgery, corneal HOA, Z3−1, Z31, and Z40 in both groups were significantly increased compared with those before surgery, with statistically significant differences (P < 0.001). At 1, 3, and 6 months after surgery, the Z3−1 of the Trans-PRK group was significantly lower than that of the FS-LASIK group (P < 0.001). ΔHOA and ΔZ40 were dramatically correlated with the ΔQ value for both FS-LASIK and Trans-PRK procedures. The ΔQ was significantly correlated with the preoperative SE, AD, and AD/CCT after both two procedures (all P < 0.001). Conclusions Both FS-LASIK and Trans-PRK caused the anterior corneal surface to become flatter, and the morphology of the corneal surface was irregular. Corneal HOAs were significantly increased after the two procedures. Trans-PRK using SPT introduced less corneal vertical coma than FS-LASIK. Corneal asphericity changes contributed to the corneal aberrations changes following FS-LASIK and Trans-PRK.

Factors Influencing Higher-order Aberrations in Young Myopes

Purpose : To investigate the effects of age, refractive errors, corneal refractive power, pupil diameter, and pupil center shift on high-order aberrations (HOAs) in young myopic eyes. Methods : The myopic eyes of aged 20 to 39 years who had no ophthalmologic diseases and refractive surgery were recruited. I-Profilerplus (Zeiss, Berlin, Germany) was used to measure HOAs and refractive errors, corneal refractive power, pupil diameter, and pupil shift, and factors affecting HOA were analyzed. Results : In young myopes, as the age increased, the total HOA was increased in the positive (+) direction (p<0.001), and the horizontal coma, vertical coma, and spherical aberration (SA) were increased in the negative (-) direction (all, p<0.001). As the equivalent spherical refractive errors increased in the negative (-) direction, the total HOA was increased in the negative (-) direction (p<0.001), and the SA was increased in the positive (+) direction (p=0.004). As the mean corneal refractive power increased, the total HOA and SA were increased in the negative (-) direction (p<0.001, p=0.025), and the horizontal coma and vertical coma aberration were increased in the positive (+) direction (p=0.001, p<0.001). As the pupil diameter increased, vertical trefoil and SA were increased in the positive (+) direction (all, p<0.001). As the pupil center shift increased toward the lateral, the horizontal coma aberration increased in the positive (+) direction (p=0.003), and as the pupil center shift increased toward the superior, the vertical coma aberration increased positive (+) direction (p<0.001). Conclusion : The ocular HOAs of the young myopes changes according to age, refractive error, corneal refractive power, pupil size, and pupil center shift and the results in this study would be cornerstones in designing lenses for spectacle and contact lens.