Changes In Spherical Aberration Research Articles

Fourier analysis of corneal irregular astigmatism after small-incision lenticule extraction and transepithelial photorefractive keratectomy: A comparative study.

To compare changes in the spherical component, regular astigmatism, and irregular astigmatism of the anterior surface of the cornea after small-incision lenticule extraction (SMILE) and transepithelial photorefractive keratectomy (TransPRK). Fifty-six patients underwent SMILE in 56 eyes, and 68 patients underwet TransPRK in 68 eyes. The right eye was chosen to enter the group. Six months after the procedure, Scheimpflug images were acquired, and Fourier analysis of the anterior surface of patients' corneas was performed using the Pentacam built-in software. Fourier parameters encompass various measurements such as the steepest radius of the curvature and average eccentricity of the spherical components (SphRmin and SphEcc), maximum decentration (MaxDec), central and peripheral regular astigmatism (regular astigmatism at the center [AstC] and regular astigmatism at the periphery [AstP]), and irregularity (Irr). At 6 months postoperatively, SphEcc decreased significantly (P < .001), MaxDec increased significantly (P < .001), and Irr increased insignificantly (P = .254) in the SMILE group. SphEcc decreased significantly (P < .001) and MaxDec and Irr increased significantly (P < .001) in the TransPRK group. TransPRK caused greater changes in SphEcc, MaxDec, and Irr on the anterior corneal surface than SMILE (P < .05). The amount of MaxDec-induced changes in SMILE and TransPRK was significantly correlated with the amount of higher-order aberrations and spherical aberration changes (P < .05). SMILE and TransPRK increase overall irregular astigmatism on the anterior surface of the cornea, more so with TransPRK, where changes in decentration are associated with with increased higher-order aberrations.

Using adaptive optics to optimize the spherical aberration of eyes implanted with EDOF and enhanced monofocal intraocular lenses.

To assess the effect of change in ocular spherical aberration (SA) with adaptive optics on visual acuity (VA) at different defocus after implantation of extended depth-of-focus (EDOF) and enhanced monofocal intraocular lenses (IOLs). Narayana Nethralaya Eye Hospital, Bangalore, India. Prospective, longitudinal, observational. 80 eyes (40 patients) that had cataract surgery were included in the study. 40 eyes were implanted with Eyhance EDOF IOLs and the remaining with Vivity EDOF IOLs. Baseline ocular aberrations were measured with a visual adaptive optics aberrometer, then the optimal SA was determined by increasing it in steps of -0.01 μm up to -0.1 μm until the maximum improvement in near distance VA was observed for a given eye. Then the defocus curve for each eye was measured after modifying the ocular SA by magnitude equal to optimal SA. Most of the eyes accepted a negative induced SA of -0.05 μm (Eyhance group: 67.6%; Vivity group, 45.2%). In the Eyhance group (dominant eyes), VA improved at -2 diopters (D) ( P < .02) only and degraded at 0 D, +0.5 D, and +1 D defocus ( P < .05). In the Vivity group, the VA remained unchanged at all defocus ( P > .05). In the Eyhance group (nondominant eyes), VA improved at -3.5 D defocus only and degraded at +1.5 D and +2 D defocus ( P < .05). In the Vivity group, VA improved at -2.5 D defocus ( P < .05) only. A negative induced SA of -0.05 μm in implanted eyes was optimal for a slight improvement in distance-corrected near and intermediate VA without any significant decrease in baseline distance-corrected VA.

Longitudinal changes in objective accommodative response, pupil size and spherical aberration: A case study

AbstractPurposePrevious transverse and a handful of longitudinal studies have shown that the slope of the static accommodation response/stimulus curve declines as complete presbyopia is approached. Changes in pupillary miosis and ocular spherical aberration (SA) are also evident. This study further investigated longitudinal changes in the relationships between the monocular static accommodative response, pupil diameter and SA of a single adult.MethodsA wavefront analysing system, the Complete Ophthalmic Analysis System, was used in conjunction with a Badal optometer to allow continuous recording of the aberration structure of the dominant eye in a low myope for a range of accommodative demands (−0.83 to 7.63 D) over a period of 17 years until the age of 50. Monocular accommodative response was calculated as the equivalent refraction minimising wavefront error. The associated longitudinal changes in pupil size and SA with accommodation were also recorded.ResultsA decrease in accommodation response with age was found at almost all target vergences, with the changes being greatest for higher vergences. In addition, although absolute pupil diameter decreased with age, the rate of change in pupil diameter with accommodative stimulus remained approximately constant with age. Pupil constriction occurred for near stimuli even in full presbyopia. SA changed linearly with the accommodation response at all ages.ConclusionsThe objective amplitude of accommodation declined linearly with age as complete presbyopia was approached, while the slope of the response/stimulus curve also fell. It was hypothesised that the retinal image blur associated with the larger lags of accommodation at higher accommodative stimuli was reduced by pupil constriction and the resulting lower levels of SA.

Effect of Upper Lid Blepharoplasty Surgery on Corneal Topography and Corneal High-Order Aberrations.

The objective of this study was to prospectively investigate the effect of upper eyelid blepharoplasty surgery for dermatochalasis on corneal topographic data and high-order aberrations (HOAs). Fifty eyelids of 50 patients with dermatochalasis who underwent upper lid blepharoplasty surgery were prospectively studied. A Pentacam (Scheimpflug camera, Oculus) device was used to measure corneal topographic values, astigmatism degree, and HOAs before and at 2 months after upper eyelid blepharoplasty. The mean age of the patients included in the study was 55.96 ± 12.4 years, 40 (80%) were female and 10 (20%) were male. We found no statistically significant difference in the pre-and postoperative values of corneal topographic parameters (p > 0.05 for all). In addition, we observed no significant postoperative change in the root mean square values of low, high, and total aberration values. In HOAs, we detected no significant change in spherical aberration, horizontal and vertical coma, and vertical trefoil; we only found a statistically significant increase in horizontal trefoil values after surgery (p < 0.05). In our study, we found that upper eyelid blepharoplasty did not cause significant changes in corneal topography, astigmatism, and ocular HOAs. However, studies are reporting different results in the literature. For this reason, it is important for patients considering upper eyelid surgery to be warned about visual changes that may occur after surgery.

Changes in aberrations and biomechanics after femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) in eyes with high astigmatism: a retrospective case control study

Background:To compare the 6-month changes in aberration and biomechanics after femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) for high astigmatism.Methods:In this retrospective case control study, 47 eyes with high astigmatism (≥ 2.5 D, HA group) and 47 eyes with low astigmatism (≤ 1.0 D, LA group) underwent FS-LASIK. Preoperative and follow-up examinations included visual outcomes, higher order aberrations (HOAs) and biomechanics. Biomechanical parameters include a deformation amplitude ratio of 2 mm (DA ratio 2 mm), integrated inverse radius (IIR), stiffness parameter at first applanation (SP-A1), and ambrosio relational thickness through the horizontal meridian (ARTh).Results:Six months postoperatively, there was no significant difference in the efficacy and safety index (both P > 0.05) between the two groups, but the cylinder was higher in the HA group. The HOAs increased significantly after surgery in both groups (all P < 0.05). Six months postoperatively, the changes in spherical aberration and HOAs were larger in the HA group (both P < 0.005), but there was no significant difference between the changes in coma (P > 0.05). Significant decreases in SP-A1 and ARTh and significant increases in the IIR and DA ratio of 2 mm (all P < 0.05) were observed after surgery in both groups. The changes in the DA ratio 2 mm, IIR, SP-A1, and ARTh were not significantly different between the groups.Conclusion:FS-LASIK had relative comparable efficacy and safety in correcting high and low myopic astigmatism, with higher astigmatic under-correction in eyes with high astigmatism. High astigmatism in eyes after FS-LASIK could introduce larger corneal aberrations, but the impact on corneal stiffness was the same as that in eyes with low astigmatism.

Evaluation of the Effects of Myopic Astigmatism Correction and Anterior Corneal Curvature on Functional Optical Zone After SMILE.

To evaluate the influence of different degrees of myopic astigmatism correction and preoperative anterior corneal curvature on the functional optical zone (FOZ) following small incision lenticule extraction (SMILE). In this retrospective study, 68 patients (106 eyes) treated with SMILE were grouped according to myopic astigmatism correction: control (0.00 diopters [D]), moderate astigmatism (-0.50 to -2.00 D), and high astigmatism (> -2.00 D). The FOZ was measured and compared between the three groups for 3 months. Correlations between attempted correction, anterior corneal curvature, corneal aberrations, and the FOZ were analyzed. The preoperative mean treatment spherical equivalent was comparable among the three groups. The average FOZ was 5.06 ± 0.24 mm in the control group, 5.19 ± 0.25 mm in the moderate astigmatism group, and 5.35 ± 0.20 mm in the high astigmatism group The FOZ showed statistically significant differences among the three groups (P < .001), particularly between the high astigmatism group and the other two groups (P < .001 and .018). Correlation analysis showed that the total higher order aberrations, coma, and spherical aberration change were correlated with the FOZ (P < .001). Preoperative steep keratometry, average keratometry, and corneal astigmatism were significantly correlated with the FOZ (P < .05). The correlation remained after excluding the influence of attempted correction on the FOZ (P < .05). After adjusting for other risk factors using multiple linear regression analysis, there was still a significant positive association between preoperative steep keratometry and the FOZ (P < .001). Patients with higher myopic astigmatism achieved a larger FOZ and less induced horizontal coma than the control and moderate astigmatism groups. A larger FOZ after SMILE can be achieved in eyes with steeper keratometry. [J Refract Surg. 2023;39(2):135-141.].

Evaluation of aberrometry changes following strabismus surgery in patients with horizontal strabismus.

The aim is to investigate the change in aberrations following strabismus surgery in patients with horizontal strabismus. This prospective study included patients who underwent surgery for horizontal strabismus. The patients were assessed preoperatively and 1 month and 3 months after the surgery, in terms of logMAR best-corrected visual acuity, eye deviation, spherical equivalent refractive error, tomographic and aberrometric corneal changes. Corneal tomography was performed using Orbscan II device. Wavefront analyses were performed using Bausch and Lomb Zywave II. A total of 25 patients (48 eyes) with exotropia or esotropia were entered in this study. Mean values of exotropia in the distance and near deviations were reported as 31.42 ± 7.13 and 28.82 ± 6.96 prism diopters (PD), respectively. Mean scores of esotropia in the distance and near deviations were 25.22 ± 5.41 and 30.45 ± 9.4 PD, respectively. Evaluation of irregularity in 5 mm zone, horizontal coma, spherical aberration changes, and root mean square of higher-order aberrations (HOAs) in 6 mm, and HOA w/o Z 400 changes showed that there was a significant difference before the intervention and 1 month after the surgery (P < 0.05). However, no difference was observed in the aforementioned variables before and 3 months after the intervention (P > 0.05). Results of the present study indicated a transient increase in HOAs and corneal irregularity following strabismus surgery on horizontal eye muscles that returned to the baseline after 3 months.

Accommodation through simulated multifocal optics.

We evaluated the interaction of multifocal patterns with eye's accommodation. Seven patterns were mapped on the spatial light modulator and the deformable mirror of an adaptive optics visual simulator, and projected onto the subjects' eyes, representing different contact lens designs: NoLens, Bifocal Center Distance (+2.50D), Bifocal Center Near (+2.50D) and Multifocal Center Near-MediumAdd (+1.75D) and Center Near HighAdd (+2.50D), positive and negative spherical aberration (±1µm). The change in spherical aberration and the accommodative response to accommodative demands were obtained from Hartmann-Shack measurements. Positive spherical aberration and Center Distance designs are consistent with a higher accommodative response (p=0.001 & p=0.003): steeper shift of SA towards negative values and lower accommodative lag.

Regional Changes in Posterior Corneal Surface During a 6-Month Follow-up Period After tPRK, FS-LASIK, and SMILE.

To investigate changes in corneal curvature in different zones of the posterior corneal surface during a 6-month follow-up period after transepithelial photorefractive keratectomy (tPRK), femtosecond laser-assisted excimer laser in situ keratomileusis (FS-LASIK), and small incision lenticule extraction (SMILE). The study included a total of 202 eyes, including 65, 77, and 60 that underwent tPRK, FS-LASIK, and SMILE, respectively. Elevation data for the posterior surface were obtained preoperatively (pre), as well as 1 week (pos1w), 1 month (pos1m), 3 months (pos3m), and 6 months (pos6m) postoperatively. Changes in posterior corneal curvature (M) were analyzed in the central (diameter: 0 to 3 mm), paracentral (diameter: 3 to 6 mm), and peripheral (diameter: 6 to 9 mm) regions. Over all follow-up periods, the central region of the posterior surface in all patients became flatter (P < .05), with FS-LASIK showing the largest change, whereas the paracentral and peripheral regions became steeper. The posterior curvature changes between pre and pos6m, determined before and after correction for ablated stromal depth, tended to follow similar trends in the three regions and after the three surgeries. There was also no significant correlation (P > .05) between the changes in the mean curvature (M, recorded between pre and pos6m) and each of the refractive error corrections, the changes in spherical aberration postoperatively, the optical zone diameter, ablated stromal depth, and residual stromal bed thickness in the central and peripheral regions, but the correlation was significant in the paracentral region. The postoperative changes in posterior corneal shape followed different trends in the central, paracentral, and peripheral regions. The FS-LASIK group exhibited the most notable changes in posterior corneal curvature, especially in the central region. These changes were statistically correlated with variations in spherical aberration, and ablated and residential stromal thickness in the paracentral region. [J Refract Surg. 2022;38(11):708-715.].

Change of Spherical Aberration in Early Presbyopia Wearing Center-Near Multifocal Soft Contact Lens

Change of Spherical Aberration in Early Presbyopia Wearing Center-Near Multifocal Soft Contact Lens

Changes in asphericity of anterior and posterior corneal surfaces for mild-moderate and high myopia after topography-guided FS-LASIK.

To compare changes in asphericity of anterior and posterior corneal surfaces for different myopia patients after corneal topography-guided femtosecond-assisted laser in situ keratomileuses (FS-LASIK), and to analyze correlations between asphericity of corneal surfaces and preoperative spherical equivalence (SEQ). In this prospective study, 59 patients who underwent corneal topography-guided FS-LASIK surgery were enrolled and divided into the mild-moderate myopia group (67 eyes) and the high myopia group (44 eyes). Postoperative follow-ups were performed at 1, 3, and 6months. Postoperative changes in aspherical coefficient (Q values), corneal higher-order aberrations (HOAs), and spherical aberrations (Z40) were compared between the two groups. Relevance between Q value changes and SEQ, HOAs, and Z40 as well as between SEQ and changes of HOAs and Z40 was analyzed. There was a significant increase in Q values of the anterior (each diameter) and posterior (6-8mm) corneal surface in both groups than before surgery (P < 0.001). Q values of corneal anterior (each diameter) and posterior (7-9mm) surface in the high group were considerably larger than the mild-moderate group (P < 0.05). Corneal anterior surface HOAs and Z40 values in the high group largely exceeded those of the mild-moderate group (P < 0.001). The preoperative SEQ was linearly correlated with postoperative anterior Q change (ΔQ), HOAs change (ΔHOAs), and spherical aberration change (ΔZ40). The changes of corneal asphericity in patients with high myopia were greater than mild-moderate myopia, with more corneal HOAs and Z40 introduced when corneal topography-guided FS-LASIK was conducted.

Comparison of visual outcomes between 120-µm and 140-µm cap thicknesses 12months after small incision lenticule extraction.

To compare visual and refractive outcomes as well as changes in high-order aberrations in patients with 120- versus 140-µm cap thicknesses 12months after small incision lenticule extraction. Ninety-four patients were randomized to receive small incision lenticule extraction with either a 120-µm cap thickness (n = 47) or a 140-µm cap thickness (n = 47) to treat myopia or myopic astigmatism, if not both. In an analysis of right eyes only during the 12-month follow-up period, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive outcomes, and high-order aberrations were evaluated. The distribution of patients by age and sex between the groups did not differ significantly (P = .803 and P = .680, respectively). CDVA, spherical and cylindrical refraction, and changes in total high-order aberration, spherical aberration, coma, and trefoil were similar between the groups at 6 and 12months, postoperatively. However, UDVA was statistically significantly higher in patients with 140-μm cap thicknesses than with 120-μm cap thicknesses at 6 and 12months postoperatively (P < .001 and P < .001, respectively). Patients with 140-µm cap thickness showed greater improvement in UDVA than ones with 120-µm cap thickness at 12-month follow-up (P = .005). Both 120- and 140-μm cap thicknesses in small incision lenticule extraction were safe and effective thicknesses for correcting myopia or myopic astigmatism. The patients with 140-μm cap thickness had better improvement in UDVA after 12-month follow-up compared to patients with 120-μm cap thickness.

Prospective, Randomized, Contralateral Eye Comparison of Functional Optical Zone, and Visual Quality After SMILE and FS-LASIK for High Myopia.

PurposeTo compare the functional optical zone (FOZ) and visual quality after small-incision lenticule extraction (SMILE) and femtosecond laser–assisted laser in situ keratomileusis (FS-LASIK) in correcting high myopia.MethodsNinety-two eyes of 46 high myopic patients with the same programmed optical zone (POZ) received SMILE in one eye and FS-LASIK in the contralateral eye. FOZ was calculated using a refractive power method. The decentration, visual outcomes, wavefront aberrations, contrast sensitivity, and quality of vision (QoV) questionnaire were analyzed at 6 months postoperatively.ResultsThe postoperative visual and refractive outcomes were comparable between SMILE and FS-LASIK. The FOZ for SMILE (5.62 ± 0.31 mm) was larger than for FS-LASIK (5.35 ± 0.28 mm; P < 0.001). Moreover, the total decentration for SMILE (0.29 ± 0.14 mm) was greater than in FS-LASIK (0.22 ± 0.11 mm; P < 0.001). The induced change in spherical aberration was less for SMILE than for FS-LASIK (P < 0.001). There was better contrast sensitivity under the mesopic condition with glare for SMILE than for FS-LASIK (P = 0.024). However, no significant difference was found in QoV scores between the two groups.ConclusionsSMILE created a larger FOZ and greater decentration than FS-LASIK when the same POZ was designed in high myopia. Objective and subjective visual symptoms were comparable between SMILE and FS-LASIK.Translational RelevanceThe differences in FOZ and decentration between SMILE and FS-LASIK have little effect on vision outcomes. Surgeons should consider the FOZ and decentration in surgical options in high myopia.

Two-Year Changes in Corneal Spherical Aberration After Laser-Assisted In Situ Keratomileusis and Photorefractive Keratectomy in Regular and Wavefront-Guided Ablations.

IntroductionThe aim of this study was to analyze the changes in corneal spherical aberration following regular ablation (RA) and wavefront-guided (WFG) ablations in photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK).MethodsA retrospective analysis was performed on the eyes that underwent femtosecond LASIK or PRK between January 2016 and December 2018. Changes in the corneal spherical aberration were measured preoperatively and postoperatively with a high-resolution Scheimpflug camera system, and they were correlated with the attempted correction and all other tomography parameters.ResultsOf the 3826 eyes that were reviewed, 484 eyes met the inclusion criteria and were enrolled in the study. Seventy-four eyes underwent PRK and 410 eyes underwent LASIK. The LASIK and PRK subgroups were similar in terms of the general demographics, preoperative higher-order aberrations, and manifest spherical equivalent. The changes in spherical aberration were significantly correlated with the attempted correction in both LASIK (y = –0.35x and R2 = 0.42 for myopic WFG; y = –0.18x and R2 = 0.19 for myopic RA; y = –0.44x and R2 = 0.49 for hyperopic WFG; y = –0.53x and R2 = 0.69 for hyperopic RA) and PRK (y = –0.20x and R2 = 0.25 for myopic WFG; y = –0.37x and R2 = 0.44 for myopic RA). No other preoperative parameters except corneal asphericity, axial length, and anterior chamber depth were significantly correlated with the changes in the spherical aberration.ConclusionsLASIK correction had a higher induction of spherical aberration compared with that of PRK, and the beneficial effect of the WFG treatment on spherical aberration was mainly visible in the PRK-treated eyes.

Effect of the Optical Zone Ablation Diameter on Higher Order Aberrations After Transepithelial Photorefractive Keratectomy: A Cohort Study.

Objectives: To study the effect of the optical zone diameter of ablation on higher order aberrations after transepithelial photorefractive keratectomy for myopia and myopic astigmatism.Methods: In this historical cohort study in 2019, patients were grouped into 7-mm (Gr-1) and 6.5-mm optical zones of ablation (Gr-2). Topographic and higher order aberrations at analysis diameters of 2, 4, and 6 mm were measured before and six months after transepithelial photorefractive keratectomy. The changes in the five types of higher order aberrations in the 6.5 mm and 7 mm groups were compared. The pupillary diameter was correlated with the change in the higher order aberrations.Results: We had 24 eyes of 12 patients in Gr-1 and 80 eyes of 40 patients in Gr-2. The trefoil type of higher order aberrations at 6 mm was significantly more prevalent in Gr-2 than in Gr-1 before surgery (p = 0.038). The change in spherical aberration six months after surgery compared with before was significantly more at 6 mm in the eyes of Gr-2 patients (p = 0.02). For the eyes managed by the 7-mm optical zone of ablation for transepithelial photorefractive keratectomy, the decline in the different types of higher order aberrations was significant. The pupillary diameter was positively correlated with the change in the third-order coma in Gr-2 (Spearman coefficient, p = 0.005). All the eyes had an uncorrected visual acuity of 0.0 LogMAR in Gr-1 and 95% in Gr-2 after surgery.Conclusions: The higher order aberrations six months after transepithelial photorefractive keratectomy were similar in eyes managed with 7-mm and 6.5-mm optical zone for ablation. But a lower aberration coefficient in eyes was managed by the 7-mm zone than the 6.5-mm zone of optical ablation at 6-mm analysis diameter.

Short-term effect of atropine on higher-order aberrations in myopic children.

This study aimed to investigate the short-term effect of cycloplegia on higher-order aberrations (HOAs) in school-age myopic children who received 0.25% atropine for cycloplegic refraction. We performed a retrospective chart review of 24 myopic children between the ages of 5 and 15 years, who had received one topical drop of 0.25% atropine for three consecutive nights before undergoing cycloplegic refraction. Auto-refraction, visual acuity, and HOAs measured with the iTrace aberrometer were compared before and after atropine use. To account for the effect of cycloplegia, the amount of HOAs under matching scanning sizes was compared. There were statistically significant differences in the spherical equivalent, with a hyperopic shift after atropine use (p < 0.001). Corrected visual acuity and spherical aberrations showed no significant change under the respective pupil and scanning sizes before and after atropine use. Under identical scanning sizes, there was a significant change in total spherical aberration (from 0.03 to 0.06 μm, p = 0.044) and internal spherical aberration (from -0.10 to -0.05 μm, p = 0.049) after atropine use. Differences in corneal spherical aberration were insignificant. The positive shift of spherical aberration induced by the inhibition of accommodation in myopic children may have a possible effect against myopic progression. Future studies can focus on the long-term effect on HOAs and impact on visual quality with lower concentrations of atropine.

Changes in corneal asphericity and spherical aberration after femtosecond laser in situ keratomileusis

Purpose The aim of this study was to evaluate the changes in corneal asphericity (Q value) and spherical aberration after femtosecond laser in situ keratomileusis using Scheimpflug imaging.Patients and methods This is a prospective nonrandomized study that included 170 myopic eyes and 30 hyperopic eyes. All patients had wave front-optimized femtosecond laser in situ keratomileusis using the EX-500 and FS200 machines (WaveLight, Alcon). Patients within ±0.50 diopter (D) of plano-refraction and with an uncorrected distance visual acuity of at least 20/20 were evaluated. The Q values and corneal spherical aberration Zernike values were obtained using Scheimpflug imaging (Oculyzer II) preoperatively and 1–3 months postoperatively.Results The mean preoperative Q value was −0.28±0.11 and −0.22±0.15 in myopic and hyperopic eyes, respectively, and became +0.35±0.44 and −0.64±0.31, respectively, postoperatively. The asphericity change was highly correlated with the preoperative spherical equivalent (r2=0.81, P≤0.001). The mean preoperative corneal spherical aberration was +0.21±0.08 µm in the myopic eyes, and +0.36±0.11 µm in the hyperopic eyes and became +0.36±0.17 and 0.00±0.29 µm, respectively, postoperatively. The corneal spherical aberration changes were correlated with the amount of preoperative refractive error (r2=0.34, P<0.001). There was a tendency for the Q values and spherical aberrations to become more positive after myopic ablation and more negative after hyperopic ablation.Conclusions Myopic and hyperopic corrections induced changes in the Q value and spherical aberrations in opposite directions (i.e. positive in myopic and negative in hyperopic eyes). The changes depend on the magnitude of the refractive correction.

Elliptical versus circular flap configuration in myopic eyes undergoing femtosecond laser in situ keratomileusis surgery: A contralateral eye study.

Purpose:To study whether a customized elliptical flap configuration offers any visual, refractive, or biomechanical advantage over the “conventional” circular flaps in patients undergoing myopic laser in situ keratomileusis (LASIK).Methods:A prospective interventional contralateral eye study was undertaken enrolling 290 eyes of 145 myopic patients (≤−6.0D) undergoing LASIK, wherein the corneal flap was created in one eye using a customized elliptical flap configuration versus a conventional circular flap configuration in the other eye. Postoperatively, we compared the visual outcome, change in higher-order aberrations, corneal asphericity, and corneal biomechanics.Results:The visual outcomes, including higher-order aberrations, were comparable between the two groups. Changes in spherical aberration (mean: 0.234–0.331 versus 0.234–0.42; P = 0.644), corneal asphericity (−0.32–0.34 versus − 0.34–0.45; P = 0.42), corneal hysteresis (9.35–7.33 versus 9.4–6.71, P = 0.489), corneal resistance factor (9.71–7.40 versus 10.38–6.9, P = 0.181) were comparable between the elliptical and circular groups, respectively.Conclusion:We evaluated the usefulness of a customized elliptical flap configuration for performing LASIK surgery. Our data suggests that elliptical flaps may be associated with superior visual and biomechanical performance compared to circular flaps. This is certainly relevant in eyes with “borderline” pre-LASIK profile to improve patient satisfaction and safety after surgery.

Small incision lenticule extraction versus photorefractive keratectomy: A comparative study

Purpose: The purpose of the study is to compare the objective and subjective quality of vision following small incision lenticule extraction (SMILE) and photorefractive keratectomy (PRK). We compared the postoperative safety, efficacy, predictability, refractive stability, contrast sensitivity, and spherical aberration changes in two groups over a 1-year follow-up period. Materials and Methods: This was a retrospective comparative study of 1-year duration. Fifty eyes of patients who underwent SMILE and 50 eyes of patients who underwent PRK were selected based on the inclusion and exclusion criteria. Methodology: Standard preoperative evaluation for all patients included corneal topography, refraction, anterior segment, retina evaluation, and intraocular pressure. Uncorrected visual acuity, best-corrected visual acuity, spherical aberration, and contrast sensitivity were measured preoperatively followed by 1, 3, 6, 9, and 12 months postoperatively. Results: Ninety-six percent of the eyes of patients who underwent SMILE and 92% of the eyes of patients who underwent PRK achieved postoperative refraction within ±0.5 D of the intended target refraction. No eyes in both the groups had any loss of visual acuity. Both procedures induced statistically significant spherical aberrations. However, the difference between the two groups was not statistically significant (P > 0.05). One hundred percent of eyes in SMILE and PRK group were noted to have a stable postoperative refraction till the last follow-up. Contrast sensitivity was better in eyes of patients who underwent SMILE comparing to PRK. Conclusion: Overall, both SMILE and PRK have shown excellent safety, efficacy, and predictability for correction of myopia and myopic astigmatism. SMILE is better in terms of refractive accuracy and quality of vision.

Comparison of early visual outcomes after low-energy SMILE, high-energy SMILE, and LASIK for myopia and myopic astigmatism in the United States.

To compare uncorrected distance visual acuities (UDVAs) and induced higher-order aberrations (HOAs) in the early postoperative period between low-energy (LE) small-incision lenticule extraction (SMILE), high-energy (HE) SMILE, and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) procedures. University based refractive surgery center. Retrospective cohort study. Records of patients who underwent SMILE or FS-LASIK were retrospectively reviewed. SMILE patients were separated into 2 groups: HE settings (125 nJ, 3.0 μm spot spacing) and LE settings (125-130 nJ, 4.5 μm spot spacing). UDVA was measured at postoperative day (POD) 1. Corneal HOAs and UDVA were measured at postoperative month (POM) 1. Induced spherical aberration, vertical coma, horizontal coma, total coma, and total HOAs were calculated. The study included 147 eyes of 106 patients, 49 in each group. For SMILE patients, the difference in mean UDVA at POD1 was highly statistically significant in favor of the LE group (-0.003 vs 0.141, P < .0001). No significant difference in mean UDVA at POD1 was noted between the LE group and FS-LASIK group (-0.003 vs -0.011, P = .498). Induced change in spherical aberration was less in LE SMILE than that in FS-LASIK (0.136 vs 0.186 μm, P = .02) at POM1. No significant differences in POM1 mean UDVA (-0.033 vs -0.036) or induced change in all other HOAs were noted between LE SMILE and FS-LASIK. LE settings were associated with significantly improved POD1 UDVA. POD1 and POM1 UDVA were comparable with those of FS-LASIK. Spherical aberration induction was less with LE SMILE than that with FS-LASIK, whereas all other induced HOAs were comparable with FS-LASIK.