Higher-order Aberrations Research Articles

Corneal higher-order aberrations and their relationship with choroid in myopic patients.

To investigate corneal higher-order aberrations (HOAs) and choroidal characteristics in myopic individuals and explore the association between HOAs and choroidal parameters. Myopic participants were categorized into three groups based on axial lengths (ALs). We compared corneal HOAs, including spherical (Z40), comatic (Z3 - 1 and Z31), and trefoil (Z3 - 3 and Z33) aberrations, as well as choroidal vascularity index (CVI) and choroidal thickness (CT). Linear regression analysis was used to assess the relationships among corneal HOAs, CVI, CT, spherical equivalent, and AL. Groups 1, 2, and 3 included 105, 98, and 118 eyes, respectively. Group 3 exhibited lower spherical HOA root mean square and Z40 values than group 1(p < 0.05). Group 1 showed lower Z31 levels than other groups (p < 0.001). Groups 1 and 2 had higher mean, central, and I2 vertical CVIs than group 3 (p < 0.05). Group 1 had a larger vertical S1 CVI than group 3 (p < 0.05). Group 3 had smaller horizontal CVI values in all regions except N2 (p < 0.05). Both the mean and CT in all regions decreased as AL increased (p < 0.001). The comatic (Z31) and trefoil (Z33) components were predictors of mean horizontal CVI, and the comatic (Z31) component was correlated with both mean vertical and horizontal CT. Longer AL myopic patients exhibited lower absolute values of spherical aberration and horizontal coma. Alterations in choroid in myopic patients correlated with corneal HOAs. Our results suggest a potential connection between the optical quality and ocular perfusion in myopia.

Comparison of 3-month clinical outcomes between two enhanced monofocal intraocular lenses: A single-center prospective study.

This study aims to compare the 3-month clinical outcomes between two enhanced monofocal intraocular lenses (IOLs) following cataract surgery.Setting: Eye Clinic of Careggi University Hospital, Florence, Italy. Single-center prospective study. We included patients with cataract and corneal astigmatism less than 0.75 D, with no ocular comorbidities, who underwent unilateral cataract surgery with implantation of either the Tecnis Eyhance ICB00 (N = 25) or Evolux (N = 25) IOLs. Standard cataract procedures were performed without complications. The main outcome measures included uncorrected and corrected visual acuity at distance (4 m), intermediate (60 cm) and near (40 cm) at 3-month follow-up. Additionally, monocular defocus curves, aberrometric profiles, and perceptions of halo and glare were evaluated. The study involved 50 patients (26 male, 24 female) with a mean age of 68 ± 8 years. Preoperative characteristics were similar between the groups, and no intraoperative or postoperative complications were reported. Statistically significant differences were observed between the groups, with the Evolux IOL showing superior results (p < 0.05) in terms of uncorrected and corrected visual acuity at near, intermediate, and distance, as well as in aberrometric profiles (lower-order aberration root-mean-square [RMS], higher-order aberration RMS, spherical equivalent RMS, and point spread function) and defocus curves. Based on our experience, while both IOLs offer substantial visual performance for intermediate and distance vision, the Evolux IOL demonstrated superior mean visual outcomes and objective parameters at the 3-month follow-up compared to the Tecnis Eyhance IOL. This indicates a potential advantage of the Evolux IOL in providing better visual performance.

Comparison of refractive outcomes in patients following scleral fixated intraocular lens implantation with Yamane and Z-suture techniques.

To compare visual and refractive outcomes in aphakic patients who underwent scleral fixated intraocular lens (SF-IOL) implantation with Yamane and Z-suture techniques. Retrospective study. Patients who underwent SF-IOL implantation with Yamane and Z-suture techniques due to aphakia between 2021 and 2023 were analyzed. Preoperative and postoperative 6. month best corrected visual acuity (BCVA-LogMAR), preoperative and postoperative spherical error, cylindrical error and postoperative mean absolute error (MAE), corneal endothelial and topographic parameters, 3 mm-6 mm pupil diameter corneal higher-order aberrations (HOAs) were evaluated. Seventy-seven eyes of 77 patients who underwent SF-IOL implantation with Yamane and Z-suture techniques were included in the study. Yamane technique was performed in 38 (49.4%) and Z-suture technique in 39 (50.6%) patients. Postoperative BCVA was 0.44 ± 0.40 in Yamane technique and 0.47 ± 0.44 in Z-suture technique (p = 0.73). Postoperative MAE was 0.84 ± 0.70 D in Yamane technique, 1.02 ± 0.88D in Z-suture technique (p = 0.33). Postoperative CCT-preoperative CCT (ΔCCT) was 3.76 ± 27.62 µm in Yamane technique and 3.02 ± 15.58 µm in Z-suture technique (p = 0.88). A significant difference was found between Yamane and Z-suture techniques only in the ΔTrefoil value at 6-mm pupil diameter in corneal HOAs. ΔTrefoil was significantly lower in Yamane technique (p = 0.04). Except ΔTrefoil value at 6-mm pupil diameter, although no significant difference was found, corneal endothelial and topographic parameters were less affected in Yamane technique compared to Z-suture technique.

Corneal Higher-Order Aberrations and Visual Acuity After Anterior Lamellar Keratoplasty in Treating Limbal Dermoid

Corneal Higher-Order Aberrations and Visual Acuity After Anterior Lamellar Keratoplasty in Treating Limbal Dermoid

Corneal Refractive Surgery Considerations in Patients With History of Orthokeratology.

To review the current literature describing corneal changes observed with orthokeratology (ortho-k) use and to formulate preliminary recommendations for these patients seeking corneal refractive surgery. The literature search was conducted through the PubMed, Scopus, and Ovid databases through June 4, 2024, for articles regarding corneal physiological, tomographic, and biomechanical changes secondary to ortho-k use. Forty-one articles were found describing several changes associated with ortho-k use, including higher corneal staining, central corneal epithelial thinning and midperipheral thickening, increased higher-order aberrations, decreased contrast sensitivity, reduced corneal hysteresis and corneal resistance factor, and alterations in the tear proteome. The majority of these parameters returned to baseline after ortho-k lens discontinuation, with timing potentially dependent on the amount of myopic correction, duration of ortho-k use, and age of lens fitting. Despite the paucity of articles describing prior ortho-k patients undergoing corneal refractive surgery, it is evident that ortho-k use may potentially cause various corneal physiological, tomographic, and biomechanical changes in patients. Therefore, clinicians are advised to serially monitor ortho-k patients' refraction, tomography, pachymetry, and corneal biomechanics until stability is achieved before considering surgery.

Effects of clear corneal incision location and morphology on corneal surgically induced astigmatism and higher-order aberrations after ICL V4c implantation

PurposeTo evaluate the effects of clear corneal incision (CCI) location and morphology on corneal surgically induced astigmatism (SIA) and higher-order aberrations (HOAs) in patients receiving implantable collamer lens (ICL V4c) implantation.MethodsThis retrospective study classified right eyes that underwent ICL implantation into two groups based on temporal or superior CCI. The Pentacam HR analyzer was used to measure the corneal astigmatism and HOAs. Analysis of the clear corneal incision (CCI) morphology, including incision width (Angle-W), incision length (IL), incision angles (Angle-En/Ex), and distance from the incision to corneal apex (Dis-En/Ex), was conducted using anterior segment optical coherence tomography (AS-OCT).ResultsThere were 75 eyes in the temporal CCI group and 47 eyes in the superior CCI group. Both groups showed satisfactory safety and efficacy postoperatively. In the temporal CCI group, Dis-En and Dis-Ex were considerably longer, whereas the superior CCI group displayed a significantly wider Angle-W. The anterior and posterior corneal SIA were comparable in both groups. Anterior corneal SIA was significantly correlated to Dis-En and Dis-Ex in the superior CCI group. Superior CCI caused a notable rise in corneal Z (3, 3), while temporal CCI led to increased Z (3, 1). CCI morphology was correlated to corneal Z (4, −4) and Z (4, 4) in the superior CCI group.ConclusionCCI locations caused slight variations in postoperative corneal SIA and HOAs following ICL implantation. Optimal postoperative visual outcomes may be better achieved with a CCI design featuring an increased distance from the corneal centroid and a decreased Angle-W.

Keratoconus Detection in High-Astigmatism Pediatric Patients: Optimal Pentacam Indices and Cutoff Points.

To assess the accuracy of various Pentacam indices in distinguishing keratoconus (KC) in pediatric patients with high astigmatism and to establish appropriate cutoff values. This prospective multicenter cross-sectional study included 312 eyes from 167 patients aged 6 to 18 years (mean age, 13.1 ± 3.2 years) evaluated with Oculus Pentacam HR. Patients were categorized into 4 groups: KC, forme fruste keratoconus, astigmatism greater than 2 diopters (Cyl2D), and control. A subgroup of Cyl2D comprised patients with astigmatism greater than 4 diopters (Cyl4D). Twenty-three Pentacam indices were analyzed, and receiver operating characteristic curves determined optimal cutoff points, sensitivity, and specificity. The best indices for distinguishing KC from Cyl2D were high-order aberration root mean square of the anterior corneal surface (area under the receiver operating characteristic curve 0.987), Belin/Ambrosio enhanced ectasia total derivation (0.971), index of vertical asymmetry (0.971), average pachymetric progression index (0.962), maximum Ambrosio relational thickness (0.960), posterior elevation (0.952), and anterior elevation (0.948). The accuracy of these indices was highest in the control group and lowest in the Cyl4D group. Area under the receiver operating characteristic curve was significantly lower for fruste keratoconus than KC. Optimal cutoff values were higher for astigmatic patients than for those with no refractive error. Most indices effectively distinguished between KC and normal pediatric patients. For individuals with high astigmatism, we suggest focusing on specific indices such as high-order aberration root mean square, Belin/Ambrosio enhanced ectasia total derivation value, maximum Ambrosio relational thickness, average pachymetric progression index, and index of vertical asymmetry. Optimal cutoff points for these patients were higher than those for nonastigmatic children and differed from adult populations.

Case Report: Front surface eccentricity of scleral lens: Its impact on visual quality in eyes with higher-order aberrations induced by refractive surgery

Purpose To report the impact of front surface eccentricity (FSE) of scleral lenses (SCLs) on the visual performance of eyes exhibiting refractive surgery-induced higher-order aberrations (HOAs) Method A female teenager presented to the clinic with blurring of vision and dependency on spectacles even after undergoing Small Incision Lenticule Extraction (SMILE) in both eyes (BE). Her presenting uncorrected high contrast distance visual acuity (HCDVA) was 20/60 in the right eye (RE) and 20/40 in the left eye (LE). On examination, the cornea showed a ring-shaped area of ablation with faint scarring and a well-apposed lenticule-extraction site. Subjective refraction improved the HCDVA to 20/20p in RE and 20/25 in LE but the patient was not happy with the quality of vision. Ocular aberrometry revealed an increase in total HOAs as the underlying cause of unsatisfactory vision. Result A contact lens trial was recommended for BE to enhance visual quality. Rigid corneal lenses (RCLs) were tried, but the patient was intolerant to them. Large diameter SCLs of different FSEs (0, 0.6, and 0.8) were tried to reduce these aberrations. SCL with FSE 0 yielded the most favourable visual outcome, which was confirmed subjectively on ocular aberrometry. Conclusion With this case report, we hypothesize that the eccentricity of SCL can be selected according to the asphericity (at 6 mm) of the posterior corneal surface. This case also re-emphasizes the impact of SCL with varying FSEs on reducing HOAs and enhancing visual quality in eyes where conventional RCLs yield suboptimal results.

Changes in Corneal Higher Order Aberrations Following Cataract Surgery With Different Incision Sites: A Prospective, Randomized Study.

To compare the effect of superior and temporal clear corneal incisions, regardless of the steep axis, on postoperative changes in corneal higher order aberrations (HOAs) in patients with healthy corneas and mild preoperative corneal astigmatism. In this prospective cohort study, the right eyes of study participants were randomly assigned to one of two groups prior to cataract surgery: temporal incision (TI) and superior incision (SI). Preoperatively and 6 weeks after surgery, measurements were taken of corneal HOAs over a 6-mm optical zone. The study included 102 eyes (50 eyes in the TI group and 52 eyes in the SI group) that underwent routine phacoemulsification using a 2.4-mm clear corneal incision. Significant changes in vertical coma (P = .019), horizontal coma (P = .042), and vertical trefoil (P = .001) were observed in the SI group. In the subgroup analysis of the SI group, significant changes in vertical coma (P = .025) and vertical trefoil (P = .047) were observed in the eyes with preoperative with-the-rule corneal astigmatism, and significant changes in horizontal coma (P = .038) were observed in eyes with preoperative against-the-rule corneal astigmatism. The TI group showed no significant difference between the preoperative and postoperative periods. The SI induced vertical and horizontal coma in accordance with the preoperative axis of the steep meridian. These alterations in corneal HOAs may affect the quality of vision after surgery. TI may potentially provide an advantage over SI in terms of corneal HOAs. [J Refract Surg. 2024;40(11):e792-e796.].

Intrastromal Corneal Ring Segments and Keratoconus Progression: A Case Series Study.

To assess keratoconus (KC) progression following the implant of intrastromal corneal ring segments (ICRSs) in young patients. Retrospective, longitudinal, observational, controlled nonrandomized case series study. Keratoconus patients aged 25 years or younger who underwent uneventful ICRS surgery and completed at least 3 years of follow-up were enrolled. Controls were of similar age and treatment-naive patients with KC. The following Pentacam imaging (Oculus, Wetzlar, Germany) data were analyzed: keratometric (maximum, in-flattest meridian, in-steepest meridian, and mean), aberrometric (higher-order aberrations and coma), pachymetric (thinnest corneal thickness), and elevation (maximum posterior elevation). The main outcome measure was KC progression. The study sample comprised 20 eyes of 18 cases (age 20.20 ± 3.70 years, nine right eyes, 14 male patients) and 30 eyes of 24 controls (age 20.80 ± 3.20 years, 15 right eyes, 21 male patients). The mean follow-up duration was 4.90 ± 1.70 years (range 3-8 years) for cases and 4.50 ± 1.40 years (range 3-8 years) for controls. Four cases and two controls met criteria for KC progression. Intrastromal corneal ring segments did not have significant impact on KC progression in the cohort.

Visual quality following FS-LASIK with Q-value-guided optimized monovision in patients with myopia and presbyopia: Custom-Q in treating myopia and presbyopia

PurposeTo evaluate the objective and subjective visual quality 3 months after femtosecond laser‐assisted laser in situ keratomileusis (FS-LASIK) performed with Q-value–guided optimized monovision scheme (Custom-Q) for correction of myopia with or without astigmatism and compensate for age-related accommodation deficiency. DesignProspective before-and-after study. MethodsPatients who had Custom-Q FS-LASIK for myopia with age-related accommodation deficiency were included in this prospective study. Distance, intermediate, and near visual acuities; refraction; Q value; corneal higher-order aberrations (HOAs); accommodative and binocular function measurements; defocus curve; contrast sensitivity and a subjective questionnaire assessing near visual ability and visual discomforts were evaluated before and after surgery. ResultsClinical data of 48 cases were analyzed. The mean age was 42.73 ± 2.67 years (40 to 50 years). At the 3-month follow-up, there were 100% (48/48), 92% (44/48), and 56% (27/48) patients who achieved a binocular uncorrected distance, intermediate and near visual acuity (UDVA, UIVA, UNVA) not less than 20/20 separately. Defocus curves revealed better results postoperatively at – 1.00 D and – 1.50 D. The Q value in the dominant eyes was more positive postoperatively (P<0.001), and in the non-dominant eyes, the Q value and corneal spherical aberration (SA) became more negative (P<0.05). The accommodative amplitude (AA) and relative accommodation improved binocularly (P<0.001). The questionnaire demonstrated high patient satisfaction with near vision, and patients’ perceptions of visual discomforts had no significantly difference compare with preoperative. ConclusionFor myopic patients with age-related accommodation deficiency, the Custom-Q ablation could improve near vision without compromising distance vision. It also led to minimal changes in objective optical quality, coordination of accommodative and binocular functions, contrast sensitivity, and subjective visual discomforts perceptions.

Comparative visual performance of ultraviolet light-filtering and violet light-filtering monofocal intraocular lenses of the same material and basic design

We compared the visual performance of ZCB00 ultraviolet light-filtering and ZCB00V violet light-filtering monofocal intraocular lenses (IOLs) (both Johnson & Johnson Surgical Vision) with the same materials and basic design in cataract patients treated from 2011 to 2020. The evaluations were performed 10 weeks after the last surgery for implantation of bilateral lenses ≤ 3 months apart. The ZCB00 and ZCB00V groups included 904 eyes from 452 patients (age 72.3 ± 6.8 y; women/men, 268/184) and 1374 eyes from 687 patients (age 73.0 ± 7.4 y; women/men, 415/272), respectively. Statistical validity was confirmed using a linear mixed-effects model with binocular data and adjustments for age, sex, subjective refraction cylinder, subjective refraction spherical equivalent, corneal astigmatism, axial length, pupil diameter, and corneal higher-order aberrations. ZCB00 showed slightly but significantly better results (p < 0.05, Wald) for uncorrected intermediate/near visual acuity, corrected near visual acuity, and components of the 25-item Visual Function Questionnaire (VFQ-25) (Role_Limitation, Mental_Health, Social_Function, Distance_Vision, Color_Vision). Additionally, ZCB00V showed significantly better contrast sensitivity with glare (visual angle of target: 6.3°/4.0°/0.7°; p < 0.00068, Wald); slightly but significantly better contrast sensitivity without glare (4.0°/2.5°/1.6°) and with glare (2.5°/1.6°/1.0°), VFQ-25 General_Health scores, and near spectacle independence; and slightly but significantly smaller higher-order aberrations (internal, scaled to a 6-mm pupil; Wavefront_6_post_I_Trefoil) (p < 0.05, Wald).

Effect of Nd:YAG laser posterior capsulotomy on higher order aberrations in different types of posterior capsule opacification: A prospective study.

To evaluate higher order aberrations (HOA) in different types of posterior capsule opacification (PCO) and analyze its changes fosllowing Nd:YAG laser posterior capsulotomy (LPC). Tertiary care ophthalmic hospital. Prospective, comparative, observational study. One hundred ninety-three pseudophakic eyes with PCO were evaluated over 3 months. PCO was classified into pearly, fibrous, and mixed types. Their uncorrected visual acuity (UCVA), corrected distance visual acuity (CDVA), intraocular pressure (IOP), evaluation of posterior capsule opacification (EPCO) scoring and root mean square values of HOA (total, coma, spherical, and trefoil) were measured using a wavefront aberrometer before and after LPC. Pearly, fibrous, and mixed PCO were observed in 89 (46.1%), 47 (24.4%), and 57 (29.5%) eyes respectively. The UCVA and CDVA showed improvement in all types of PCO post-procedure. The total HOA was 0.48 ± 0.47, 0.43 ± 0.42, 0.37 ± 0.34, and 0.76 ± 0.53, the coma aberrations were 0.18 ± 0.15, 0.18 ± 0.14, and 0.19 ± 0.19, spherical aberrations were 0.07 ± 0.12, 0.09 ± 0.12, and 0.05 ± 0.06, whereas the trefoil aberrations were 0.35 ± 0.44, 0.24 ± 0.26, and 0.21 ± 0.20, 15-day post-Nd:YAG LPC in pearly, fibrous, and mixed PCO respectively, all of which showed a significant reduction. The EPCO score showed no significant difference between different subtypes of PCO and had no correlation with the HOA. Post Nd:YAG LPC showed improvement in visual acuity with significant reduction in HOA in all types of PCO.

The visual outcomes and corneal biomechanical properties after PRK and SMILE in low to moderate myopia.

To compare the corneal biomechanical parameters, visual outcome, and epithelial remodeling after small-incision lenticule extraction (SMILE) and photorefractive keratectomy (PRK) for low to moderate myopia. Prospective, interventional, randomized, comparative study. Eighty eyes of 40 patients undergoing bilateral SMILE or PRK for low to moderate myopia (<-5 D SE) were included. They were divided into two groups based on the planned refractive surgery. Visual acuity, corneal biomechanics using Corvis-ST, epithelial mapping via anterior segment optical coherence tomography, and higher-order aberrations were recorded both preoperatively and postoperatively at 6 months and compared. At 6 months follow-up, the corrected distance visual acuity as well as the postoperative spherical equivalent of both the groups were comparable (P = 0.13 and P = 0.32, respectively). The biomechanical parameters like deformation amplitude ratio (P < 0.01), inverse concave radius (P = 0.006), integrated ratio (P < 0.01), stress-strain index (P < 0.01), Ambrosio's relational thickness (ArTH) (P < 0.01), and corneal biomechanical index-laser vision correction (P = 0.02) were altered more in the SMILE group than in the PRK group, while the biomechanically corrected intraocular pressure (P = 0.16) was comparable. Epithelial remodeling (P = 0.59), higher-order aberrations (P = 0.53), and stromal keratocyte loss (P = 0.16) in both the groups were comparable. Both SMILE and PRK are comparably effective procedures for correction of low to moderate myopia in terms of visual outcomes; however, the corneal biomechanical stability in PRK is superior than that in SMILE.

Effects of Rebamipide for Dry Eye on Optical Quality and Efficacy: A Systematic Review and Meta-Analysis.

Purpose: To evaluate the effects of rebamipide ophthalmic suspension on optical quality and efficacy of patients with dry eye under different conditions. Methods: A comprehensive search across five databases (PubMed, Cochrane Library, Web of Science, China National Knowledge Infrastructure, and Wan Fang) was conducted for studies published through May 13, 2024, focusing on rebamipide for dry eye treatment. Results: A total of 11 studies including 334 patients with dry eye were included. Tear breakup time (TBUT) values of patients with dry eye increased significantly after 2 weeks (standardized mean difference [SMD] =1.07, 95% confidence interval [CI] = [0.05, 2.09]), 4 weeks (SMD = 1.26, 95% CI = [0.77, 1.75]), and 12 weeks (SMD = 1.04, 95% CI = [0.37, 1.71]) of rebamipide treatment. Subgroup analysis revealed that patients with dry eye wearing soft contact lens (SCL) exhibited higher TBUT values after 4 weeks of rebamipide treatment compared with those who received rebamipide alone. In addition, rebamipide significantly improved fluorescein staining score of patients with dry eye after 4 weeks of treatment (SMD = -0.34, 95% CI = [-0.63, -0.06]). However, 4 weeks of rebamipide treatment showed no significant effect on Schirmer I test values (SMD = -0.04, 95%, CI = [-0.43, 0.35]) and higher-order aberrations (SMD = -0.73, 95% CI = [-1.77, 0.30]). Conclusions: These results indicate a significant improvement in the efficacy of rebamipide treatment for patients with dry eye, particularly for those wearing SCL. The effect of rebamipide on visual quality was found to correlate with the underlying dry eye status.

Impact of Keratoconus on Contrast Sensitivity

Objective: Keratoconus (KC) disrupts corneal shape, leading to irregular astigmatism and increased higher-order aberrations (HOA), ultimately affecting visual quality. While visual acuity (VA) remains the standard, its limitations in early KC diagnosis are recognized. This study aimed to evaluate the impact of KC on contrast sensitivity function (CSF), a potentially more sensitive measure of visual performance.Material and Methods: A case-control design compared CSF in KC patients (n=7) to healthy controls (n=16). All subjects achieved the best-corrected visual acuity (BCVA) of 6/9 or better (logMAR ≤0.10). Corneal topography was measured using Tomey TMS-5 to confirm KC diagnosis. CSF was assessed with the Functional Acuity Contrast Test (FACT).Results: KC eyes exhibited significantly reduced CSF across all spatial frequencies compared to controls (p-value&lt;0.05). Row A of the FACT chart (representing the lowest spatial frequency, 1.5 cpd) demonstrated the most prominent difference (t (21)=-3.073, p-value=0.003).Conclusion: Our findings reveal that KC patients, despite achieving good BCVA, demonstrate measurable deficits in CSF. This suggests CSF measurement with FACT may be a valuable tool for the early diagnosis and monitoring of KC, potentially offering a more sensitive and comprehensive assessment of visual function compared to BCVA alone.

Comment on: Optimum pinhole size determination in pinhole pupilloplasty for higher-order aberrations.

Comment on: Optimum pinhole size determination in pinhole pupilloplasty for higher-order aberrations.

Impact of Scleral Lenses on Visual Acuity and Ocular Aberrations in Corneal Ectasia: A Comprehensive Review.

Corneal ectasias, including keratoconus (KC), pellucid marginal degeneration (PMD), and post-LASIK ectasia, poses significant visual rehabilitation challenges due to the resultant irregular astigmatism, myopia, and higher-order aberrations (HOAs). These conditions often resist traditional corrective methods, necessitating advanced optical solutions. Scleral lenses (SLs) have emerged as a primary non-surgical option for managing these complex corneal irregularities. SLs form a smooth optical interface by forming a tear-filled chamber between the lens and the cornea, effectively mitigating HOAs and improving both high-contrast and low-contrast visual acuity (VA). This review evaluates the efficacy of SLs in enhancing VA and reducing aberrations in patients with corneal ectasia. It also explores the technological advancements in SLs, such as profilometry and wavefront-guided systems, which enable more precise and customized lens fittings by accurately mapping the eye's surface and addressing specific visual aberrations. The current body of evidence demonstrates that custom SLs significantly improve visual outcomes across various ectatic conditions, offering superior performance compared to conventional correction methods. However, challenges such as the complexity of fitting and the need for precise alignment remain. Ongoing innovations in SL technology and customization are likely to further enhance their clinical utility, solidifying their role as an indispensable tool in the management of corneal ectasias.

High-Order Aberrations: A Key Factor in Accommodative Dysfunctions

This study investigated the relationship between high-order aberrations (HOAs) and accommodative dysfunctions by analyzing their changes with accommodation. Understanding this relationship is important for understanding the mechanisms underlying these conditions. Sixty-three subjects were divided into five groups: control, infacility of accommodation (INFA), excess of accommodation (EA), insufficiency of accommodation (INSA), and symptomatic without dysfunction (SWD). Variations in root-mean-square (RMS) of the 3rd, 4th, 5th, and 6th orders and HOAs, and fluctuations of RMS HOAs, were measured using a Shack–Hartmann aberrometer at different accommodative stimuli and during residual accommodation after their removal, in the following order: 0.00 D, 1.00 D, 0.00 D, 2.45 D, 0.00 D, 4.73 D and 0.00 D. The SWD group showed a significant increase in RMS HOAs during accommodation and residual accommodation. In contrast, the EA group showed an improvement in the ocular optical quality at higher stimuli. Different patterns of changes in the 3rd, 4th, 5th, and 6th orders were observed across all groups, and fluctuations of RMS HOAs increased significantly in the SWD group during accommodation and residual accommodation. These distinct patterns of aberration changes in different accommodative dysfunctions suggest a potential link between their underlying mechanisms, providing insights that may aid their earlier diagnosis and improved management.

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.