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.

Associations Between Visual Functions and Severity Gradings, Corneal Scatter, or Higher-Order Aberrations in Fuchs Endothelial Corneal Dystrophy.

Purpose: The purpose of this study was to investigate the associations between visual function and severity grading, corneal scatter, or higher-order aberrations (HOAs) in patients with Fuchs endothelial corneal dystrophy (FECD). Methods: This observational case series study included 49 eyes of 27 patients with FECD and 10 eyes of 10 healthy individuals. We evaluated corrected distance visual acuity (CDVA) using Landolt-C and Early Treatment Diabetic Retinopathy Study charts and contrast sensitivity using the CSV-1000E chart and CSV-1000RN letter chart. We analyzed the associations between visual function and explanatory variables, including age, modified Krachmer grade, central corneal thickness (CCT), anterior segment optical coherence tomography (AS-OCT)-based grade, HOAs, intraocular straylight, and corneal densitometry. We additionally conducted receiver operating characteristic (ROC) analysis to identify the corneal densitometry thresholds for decreased visual function. Results: There were significant associations between visual function and the modified Krachmer grade, CCT, AS-OCT-based grade, HOAs, intraocular straylight, and corneal densitometry. A modified Krachmer grade ≥ 3 was identified as a threshold for decreased visual function. Multivariate analysis showed that corneal densitometry was significantly associated with all visual function parameters, and HOAs were significantly associated with CDVA but not with contrast sensitivity. ROC analysis revealed that corneal densitometry of the posterior layer at 0 to 2 mm ≥ 10 grayscale units (GSU), was identified as a threshold for decreased visual function. Conclusions: HOAs, forward and backward light scatter affected visual function, with backward light scatter being the most influential. In patients with FECD, modified Krachmer grade ≥ 3 and corneal densitometry ≥ 10 GSU were thresholds for visual disturbance.

Clinical Outcomes of a Toric Enhanced Depth-of-Focus Intraocular Lens Based on the Combination of 4th- and 6th-Order Spherical Aberration.

PURPOSE: To assess the visual and refractive outcomes of patients implanted with a toric extended depth-of-focus (EDOF) intraocular lens (IOL) following cataract surgery. METHODS: A total of 44 eyes implanted with the EDOF LuxSmart toric IOL were evaluated 4 to 6 months postoperatively. The main outcomes measurements evaluated were refractive error, rotational stability, distance, intermediate, and near visual acuities, defocus curve, photopic and mesopic contrast sensitivity, wavefront aberrations, and modulation transfer function, and the Catquest-9SF-questionnaire. RESULTS: The mean postoperative spherical equivalent and cylinder were -0.02 ± 0.26 and -0.17 ± 0.29 diopters (D), respectively. A total of 90.45% and 100% of the eyes had a postoperative spherical equivalent within ±0.50 and ±1.00 D, respectively (this being 93.18% and 100% for the refractive cylinder). The mean rotational stability was 0.61 ± 1.61 degrees. The mean binocular corrected distance visual acuity (CDVA), corrected distance intermediate visual acuity (CDIVA), and corrected distance near visual acuity (CDNVA) were -0.02 ± 0.06, 0.07 ± 0.08, and 0.26 ± 0.09 logMAR, respectively. The CDVA was 20/25 or better in 95.45% of patients, CDIVA was 20/25 or better in 72.73%, and CDNVA was 20/40 or better in 72.73%. The defocus curve showed good visual acuity at distance and intermediate vergences. The contrast sensitivity and optical quality outcomes were good with mean higher order, spherical, and coma aberration values of 0.161 ± 0.155, -0.019 ± 0.048, and 0.080 ± 0.065 µm, respectively. A total of 90.9% of patients were either fairly satisfied or very satisfied with their vision after the surgery, and 77.7% of patients reported no difficulties when reading text in newspapers. CONCLUSIONS: Implantation of the toric pure refractive EDOF technology IOL provides good refractive, optical, and visual quality at different distances, with high levels of patient satisfaction being reported. [J Refract Surg. 2024;40(6):e398-e406.].

The Long-term Visual Quality and Rotational Stability After ICL/TICL V4c Implantation in Individuals With High Myopia Older Than 40 Years.

PURPOSE: To investigate the long-term visual quality and rotational stability after the implantation of Implantable Collamer Lens (ICL) and toric ICL (TICL) (STAAR Surgical) in patients with myopia older than 40 years. METHODS: This study included 82 eyes of 41 patients older than 40 years with myopia who underwent ICL/TICL V4c implantation. The refraction sphere, refraction cylinder, spherical equivalent (SE), uncorrected and corrected distance visual acuity, and anterior segmental parameters were measured preoperatively and at the 1-month, 3-month, and last follow-up visits at 33 to 58 months postoperatively (mean follow-up: 42.56 ± 7.17 months). Wavefront aberrations and TICL rotation were measured using OPD-Scan III (Nidek Co Ltd) at the last follow-up visit. RESULTS: At the last follow-up visit, the overall safety and efficacy index were 1.22 ± 0.26 and 0.88 ± 0.34, respectively, without significant differences between the ICL and TICL groups. Postoperative refraction cylinder was -0.95 ± 0.64 and -0.71 ± 0.54 diopters in the ICL and TICL groups, respectively. The average vault was 467.44 ± 231.98 µm. The average TICL rotation was 5.45 ± 6.61 degrees, positively correlated with the preoperative anterior chamber volume (R2 = 0.1118, P = .026) and clockwise TICL alignment degree (R2 = 0.3110, P = .007) and negatively correlated with the 1-month vault (R2 = 0.1218, P = .008). There were no significant differences in the total, corneal, or internal aberrations and modulation transfer function AreaRatio between the ICL and TICL groups. CONCLUSIONS: Both ICL and TICL presented satisfactory long-term safety, efficacy, and visual quality in patients older than 40 years. Postoperative TICL spontaneous rotation was within the manageable range in the long term. [J Refract Surg. 2024;40(6):e381-e391.].

Risk Factors for Corneal Monochromatic Aberrations and Implications for Multifocal and Extended Depth-of-Focus Intraocular Lens Implantation.

PURPOSE: To discuss factors influencing corneal aberrations that might influence the optical quality after intraocular lens (IOL) implantation. METHODS: PubMed and Scopus were the main resources used to search the medical literature. An extensive search was performed to identify relevant articles concerning factors influencing the level of corneal aberrations as of August 27, 2023. The following keywords were used in various combinations: corneal, aberrations, defocus, astigmatism, spherical aberration, coma, trefoil, quadrafoil, intraocular lens, and IOL. RESULTS: Conclusive evidence is lacking regarding the correlation between age and changes in corneal aberrations. Patients with astigmatism have greater corneal higher-order aberrations than those with minimal astigmatism, particularly concerning trefoil and coma. Increased levels of corneal higher-order aberrations are noted following contact lens wear, in patients with dry eye disease, and with pterygium. Increased higher-order aberrations have been reported following corneal refractive surgery and for 3 months following trabeculectomy; regarding intraocular lens surgery, the results remain controversial. CONCLUSIONS: Several factors influence the level of corneal higher-order aberrations. Multifocal and extended depth-of-focus IOLs can share similarities in their optical properties, and the main difference arises in their design and performance with respect to spherical aberration. Preoperative evaluation is critical for proper IOL choice, particularly in corneas with risk of high levels of aberrations. [J Refract Surg. 2024;40(6):e420-e434.].

Statistical optimal parameters obtained by using clinical human ocular aberrations for high-precision aberration measurement.

PURPOSE: Compared to Shack-Hartmann wavefront sensor (SHWS), the parameters of virtual SHWS (vSHWS) can be easily adjusted to obtain the optimal performance of aberration measurement. Its current optimal parameters are obtained with only a set of statistical aberrations and not statistically significant. Whether the above parameters are consistent with the statistical results of the optimal parameters corresponding to each set of aberrations, and which performance is better if not? The purpose of this study was to answer these questions. METHODS: The optimal parameters to reconstruct 624 sets of clinical ocular aberrations in the highest accuracy, including the numbers of sub-apertures (NSAs) and the expansion ratios (ERs) of electric field zero-padding, were determined sequentially in this work. By using wavefront-reconstruction accuracy as an evaluation index, the statistical optimal parameter configuration was selected from some possible configurations determined by the optimal NSAs and ERs. RESULTS: The statistical optimal parameters are consistent for normal and abnormal eyes. They are different from the optimal parameters obtained with a set of statistical aberrations from the same 624 sets of aberrations, and the performance using the former is better than that using the latter. The performance using a fixed set of statistical optimal parameters is even close to that using the respective optimal parameters corresponding to each set of aberrations. CONCLUSION: The vSHWS configured with a fixed set of statistical optimal parameters can be used for high-precision aberration measurement of both normal and abnormal eyes. The statistical optimal parameters are more suitable for vSHWS than the parameters obtained with a set of statistical aberrations. These conclusions are significant for the designs of vSHWS and also SHWS.

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

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

Association of myopia and astigmatism with postoperative ocular high order aberration after small incision lenticule extraction.

OBJECTIVE: To investigate the correlation between higher-order aberrations (HOA) after small incision lenticule extraction (SMILE) and the severity of myopia and astigmatism, along with the relevant factors. These findings will provide valuable insights for decreasing the occurrence of HOA after SMILE and enhancing visual quality. METHODS: A total of 75 patients (150 eyes) with myopia and astigmatism who underwent SMILE were categorized into four groups based on the severity of myopia and astigmatism: Myopia Group 1 (Group M1, spherical diopter ranged from -1.00 D to -4.00 D), Myopia Group 2 (Group M2, spherical diopter ranged from -4.10 D to -10.00 D), Astigmatism Group 1 (Group A1, cylindrical diopter ranged from 0 D to -1.00 D), and Astigmatism Group 2 (Group A2, cylindrical diopter ranged from -1.10 D to -3.00 D). A comprehensive assessment was performed to examine the association between HOA and various relevant factors, including a detailed analysis of the subgroups. RESULTS: Group M1 had significantly lower levels of total eye coma aberration (CA), corneal total HOA (tHOA), internal tHOA, and vertical CA ( Z 3 - 1 ) after SMILE than Group M2 (P < 0.05). Similarly, Group A1 had significantly lower levels of total eye tHOA, CA, trefoil aberration (TA), corneal tHOA, TA, and vertical TA ( Z 3 - 3 ) after SMILE than Group A2 (P < 0.05). Pearson correlation analysis indicated a statistically significant positive relationship between the severity of myopia/astigmatism and most HOA (P < 0.05). Subgroup evaluations demonstrated a notable increase in postoperative HOA associated with myopia and astigmatism in Groups M2 and A2 compared with the control group. Lenticule thickness, postoperative central corneal thickness (CCT), postoperative uncorrected distance visual acuity (UDVA), and postoperative corneal Km and Cyl were strongly correlated with most HOA. Age, eyes, and postoperative intraocular pressure (IOP) were only associated with specific HOA. CONCLUSION: HOA positively correlated with the severity of myopia and astigmatism after SMILE. However, this relationship was not linear. HOA after SMILE was influenced by various factors, and additional specialized investigations are required to establish its clinical importance.

Uneven Corneal Epithelial Redistribution After Femtosecond Laser-Assisted Lenticule Intrastromal Keratoplasty in Correcting Moderate-to-High Hyperopia.

PURPOSE: To evaluate the characteristic of corrective epithelial thickness after femtosecond laser-assisted lenticule intrastromal keratoplasty (LIKE) to correct moderate-to-high hyperopia. METHODS: The prospective case series study of the LIKE procedure was performed to correct moderate-to-high hyperopia. The epithelial thickness map was generated by anterior segment optical coherence tomography (AS-OCT) in the corneal central 9-mm zone. Keratometry and corneal higher order aberrations were analyzed by Pentacam (Oculus Optikgeräte GmbH) preoperatively and postoperatively. RESULTS: In the 26 eyes of 13 participants who underwent the LIKE procedure for moderate-to-high hyperopia, the attempted spherical equivalence (SEQ) was +6.50 ± 1.09 diopters (D). Compared to the preoperative epithelial thickness maps, the postoperative epithelial thickness had become significantly thinner in the central 5-mm zone; the difference was 6 to 7 µm. The paracentral epithelium performed nonuniform remodeling; the thinnest epithelial thickness was located in the inferotemporal section, which has the greatest difference from the superonasal; the difference between these two was approximately 3 µm. Through correlation analysis, it was found that the sections with thinner epithelium were significantly related to corneal curvature and corneal vertical coma. CONCLUSIONS: The LIKE procedure can be used to correct moderate-to-high hyperopia. This study further indicated the epithelial remodeling characteristic after the LIKE procedure: the central and paracentral corneal epithelial thickness becomes thinner, and the epithelial thickness distributes non-uniformly, which may be the important factor of the postoperative curvature asymmetric distribution and induction of corneal vertical coma. [J Refract Surg. 2024;40(5):e321-e327.].

[Wavefront characteristics in amblyopia of different etiologies in children]. / Osobennosti volnovogo fronta pri ambliopii razlichnogo geneza u detei.

Purpose. The study investigates corneal and higher-order internal aberrations in patients with amblyopia of different etiologies and their relationship with visual acuity, refraction, axial length, and fixation parameters. MATERIAL AND METHODS: Forty-five patients (90 eyes) were examined. All patients were divided into five groups: 1 - with dysbinocular amblyopia; 2 - with refractive amblyopia; 3 - with anisometropic amblyopia; 4 - with relative amblyopia due to congenital myopia; 5 (control) - fellow eyes without amblyopia. Aberrometry was performed using the OPD-Scan III device (Nidek, Japan). Fixation parameters were studied on the MP-3 microperimeter (Nidek, Japan). Correlation analysis was performed using Pearson's linear correlation coefficient (r). RESULTS: In amblyopia associated with congenital myopia, a significant increase in corneal and internal aberrations RMS, Total HOA, astigmatism (V) (0.65±0.26; 1.01±0.31; 4.22±1.17; -2.17±0.72; 0.86±0.3, respectively; control group - 0.44±0.19; 0.58±0.27; 1.0±0.75; -0.94±0.89; 0.47±0.65) and internal spherical aberration (0.06±0.02; control group - 0.04±0.03) was found. In dysbinocular amblyopia, a significant increase in internal aberrations Trefoil (V) and Coma (H) (0.75±0.52 and 0.17±0.35, respectively; control group - 0.05±0.28 and -0.07±0.21) was found, which correlated with a decrease in fixation density in the 2° ring (r= -0.40, r= -0.41). CONCLUSIONS: The increased level of higher-order aberrations in amblyopia associated with congenital myopia is due to the anatomical and optical features of the eyes. The increase in internal aberrations Trefoil (V) and Coma (H) in dysbinocular amblyopia is associated with a mismatch of the optical elements of the eye due to impaired fixation, i.e., it is not the cause, but the consequence of amblyopia.

Comparative evaluation of biomechanical changes and aberration profile following accelerated collagen cross-linking using hypo-osmolar and iso-osmolar riboflavin: A prospective study.

PURPOSE: To compare the changes encountered in corneal biomechanics and aberration profile following accelerated corneal collagen cross-linking (CXL) using hypo-osmolar and iso-osmolar riboflavin in corneal thicknesses of <400 and >400 microns, respectively. METHODS: This is a prospective, interventional, comparative study involving 100 eyes of 75 patients with progressive keratoconus. Eyes were divided into two groups based on corneal thickness: group 1 included eyes with a corneal thickness of <400 microns who underwent hypo-osmolar CXL, and group 2 included eyes with a corneal thickness of >400 microns who underwent iso-osmolar CXL. Corneal biomechanical and aberration profiles were evaluated and compared between groups. RESULTS: In group 1, all higher-order aberrations (HOA) except secondary astigmatism significantly decreased from baseline; however, in group 2, only coma and trefoil decreased. The corneal resistance factor and corneal hysteresis significantly improved in both groups, which was significantly greater in group 2 than in group 1. The change in inverse radius, deformation amplitude, and tomographic biomechanical index was significantly improved in group 2 as compared to group 1. CONCLUSION: Improvement in corrected distance visual acuity and decrease in HOA were significantly better in the hypo-osmolar CXL group; however, the improvement in biomechanical strength of the cornea was significantly better in the iso-osmolar group.

Repeatability of pyramidal aberrometer measurements in keratoconus and normal eyes.

PURPOSE: To evaluate the intrasubject repeatability of pyramidal aberrometer measurements in a sample of keratoconus and normal eyes. SETTING: American University of Beirut Medical Center, Beirut, Lebanon. DESIGN: Prospective comparative repeatability analysis. METHODS: Study population: Keratoconus and normal eyes from adult patients. Observation procedures: Each eye was evaluated with 3 consecutive acquisitions using a pyramidal aberrometer. Main outcome measures: The repeatability of different ocular higher-order aberrations and lower-order aberrations (HOAs and LOAs, respectively), and Zernike coefficients down to the fifth order, was evaluated. Repeatability was assessed by within-subject SDs (Sw), repeatability limits ( r ), and intraclass correlation coefficients (ICCs), among other parameters. RESULTS: 72 keratoconus patients (72 eyes) and 76 normal patients (76 eyes) were included. In normal and keratoconus eyes, the ICC of total LOAs and HOAs, as well as each of the Zernike coefficients, was >0.9. The Sw for keratoconus eyes with mean maximal keratometry (Kmax) <50 diopters (D) was 0.1345 for total LOAs, 0.0619 for total HOAs, 0.0292 for horizontal coma, 0.0561 for vertical coma, and 0.0221 for spherical aberration as compared with 0.2696, 0.1486, 0.0972, 0.1497, and 0.0757 for keratoconus eyes with Kmax ≥50 D. Similar trend of better repeatability for grade 1 keratoconus and HOAs <2 D as compared with grades 2 and 3 keratoconus and eyes with HOAs >2 D were also noted. CONCLUSIONS: Ocular aberrometer measurements generated by high definition pyramidal aberrometers have high repeatability in both normal and mild keratoconus eyes and moderate repeatability, yet still clinically acceptable, in advanced keratoconus. This is of particular importance in ocular wavefront-guided treatments.

Accommodation response and spherical aberration during 1-Year of orthokeratology lens wear and after discontinuation.

BACKGROUND: To assess accommodation and spherical aberration changes during one year of orthokeratology lens wear and one month after lens cessation. METHODS: A prospective, randomized, longitudinal study was conducted on forty-seven young healthy subjects at the Optometry Clinic of the Complutense University of Madrid (Spain). Non-cycloplegic refraction, high and low uncorrected visual acuity, high and low best corrected visual acuity, accommodative lag, horizontal near phoria, corneal topography, and high-order aberrations were performed at baseline, 1-day, 1-week, 1-, 6- and 12-months of lens wear and after one month of wash out period. p < 0.05 was considered as statistically significant. RESULTS: Spherical equivalent refraction (SE) was -3.23 ± 1.57D at baseline and -0.36 ± 0.64D after 12-months of lens wear, while accommodative lag changed from 0.53 ± 0.39D to 0.15 ± 0.29D after one year of lens wear. No significant differences were found when comparing SE at baseline and after one month of lens cessation (p > 0.05). A high correlation was found between the accommodative lag at baseline and after 12 M of lens wear. 22 out of 25 subjects with exophoria at baseline showed a significant reduction in the deviation at 12-months (p < 0.05). Total spherical aberration increased during all visits due to the lens wear (p < 0.05) although internal spherical aberration showed a significant decrease for 1-week, 1-month and 12-month visits (p < 0,05). CONCLUSION: Orthokeratology lenses may change the accommodative response of the patient as a reduction on accommodative lag on exophoric patients and an overall increase on the internal spherical aberrations was found during treatment but return to nearly baseline values when cessation.

Aberration change after scleral lens wear in eyes with pellucid marginal degenerations.

PURPOSE: To investigate the impact of scleral lenses (SLs) on higher-order aberrations (HOAs), corrected distance visual acuity (CDVA), and contrast sensitivity (CS) in pellucid marginal degeneration (PMD) eyes. METHODS: SLs were fitted in 24 eyes diagnosed with PMD. CDVA, CS, and HOAs were measured at baseline and with the lens on the eye. The HOAs were measured using an i-Trace aberrometer. RESULTS: A statistically significant improvement was noted in CDVA ( P < 0.001) with BSS lenses (0.05 ± 0.04) compared to baseline (0.42 ± 0.06). Front surface eccentricity 1 (FSE1) lens provided the best CDVA in most of the eyes. The baseline CS of 1.24 ± 0.74 improved to 1.58 ± 0.48 with SL and reported a statistically significant improvement ( P < 0.001) and a gain of 6 letters. The baseline higher order-root mean square (HO-RMS) was 0.89 ± 0.53 µm, which reduced to 0.38 ± 0.24 µm ( P < 0.001), and RMS coma of 0.45 ± 0.29 µm improved to 0.20 ± 0.12 µm ( P < 0.001). Though there was a marginal reduction from 0.04 ± 0.14 to 0.03 ± 0.07, RMS spherical aberration did not show any statistically significant difference ( P = 0.37). RMS secondary astigmatism reduced from 0.17 ± 0.15 µm to 0.08 ± 0.12 µm ( P = 0.007), and RMS trefoil reduced to 0.13 ± 0.09 µm from 0.64 ± 0.36 µm ( P < 0.001) with SLs and showed statistically significant improvement. CONCLUSION: SLs can be considered an effective option that corrects a significant amount of HOAs and enhances visual performances in PMD eyes.

Allowable movement of wavefront-guided contact lens corrections in normal and keratoconic eyes.

PURPOSE: The goal was to use SyntEyes modelling to estimate the allowable alignment error of wavefront-guided rigid contact lens corrections for a range of normal and keratoconic eye aberration structures to keep objectively measured visual image quality at or above average levels of well-corrected normal eyes. Secondary purposes included determining the required radial order of correction, whether increased radial order of the corrections further constrained the allowable alignment error and how alignment constraints vary with keratoconus severity. METHODS: Building on previous work, 20 normal SyntEyes and 20 keratoconic SyntEyes were fitted with optimised wavefront-guided rigid contact lens corrections targeting between three and eight radial orders that drove visual image quality, as measured objectively by the visual Strehl ratio, to near 1 (best possible) over a 5-mm pupil for the aligned position. The resulting wavefront-guided contact lens was then allowed to translate up to ±1 mm in the x- and y-directions and rotate up ±15°. RESULTS: Allowable alignment error changed as a function of the magnitude of aberration structure to be corrected, which depends on keratoconus severity. This alignment error varied only slightly with the radial order of correction above the fourth radial order. To return the keratoconic SyntEyes to average levels of visual image quality depended on maximum anterior corneal curvature (Kmax). Acceptable tolerances for misalignment that returned keratoconic visual image quality to average normal levels varied between 0.29 and 0.63 mm for translation and approximately ±6.5° for rotation, depending on the magnitude of the aberration structure being corrected. CONCLUSIONS: Allowable alignment errors vary as a function of the aberration structure being corrected, the desired goal for visual image quality and as a function of keratoconus severity.

Analyzing Effect of Waterclefts on Visual Functions Via Optical Simulations.

Purpose: To investigate the impact of the size and location of waterclefts (WC), which are one of several cataract subtypes, on visual function by optical simulation analysis. Methods: An optical simulation software (CODE V) was used to develop a schematic eye model and several sizes of WC central and peripheral types that were located below the anterior and posterior subcapsules of the crystalline lens, and analyses of refraction, higher-order aberrations (HOA), and the modulation transfer function (MTF) were performed. Results: An increase in the WC size increased the refraction and HOA and decreased the MTF. The impact of the WC below the posterior subcapsule on the visual function was more enhanced than that below the anterior subcapsule. Large WC demonstrated a remarkable hyperopic shift in refractive power as well as an increase in HOA. The MTF decreased slightly with increasing WC size at a spatial frequency of 20 cycles/mm, and it decreased remarkably at 60 cycles/mm. Conclusions: The impact on the visual function increased with increasing WC size. It was revealed that eyes with WC below the posterior subcapsule are more hyperopic than those with WC below the anterior subcapsule, and the former have a higher HOA and lower MTF than the latter.

Clinical Outcomes of a New Type of Continuous Intrastromal Corneal Ring for Treatment of Keratoconus.

PURPOSE: The purpose of this study was to evaluate the efficacy and safety of implantation of a new continuous corneal ring in keratoconic corneas of an Iranian population. METHODS: This study was conducted on 95 contact lens-intolerant keratoconic eyes with clear central corneas. A continuous corneal ring, annular intrastromal corneal inlay (AICI), was inserted using femtosecond laser in all cases. Patients were followed up for 1, 3, and 12 months postsurgery. Visual and subjective refractive outcomes were evaluated in each examination. Besides, keratometry and aberrometric values were recorded before and 12 months after surgery. Finally, vector analysis of refractive astigmatism was performed using the Alpins method. RESULTS: The uncorrected and corrected distance visual acuities improved significantly 12 months after surgery from 0.91 ± 0.39 to 0.38 ± 0.22 (P < 0 0.001) and 0.33 ± 0.21 to 0.13 ± 0.11 logMAR (P < 0.001), respectively. Moreover, spherical and cylindrical refractive components reduced from -2.52 ± 2.62 to -0.76 ± 1.78 D (P < 0.001) and -4.14 ± 1.64 to -1.91 ± 1.18 D (P < 0.001), respectively. The mean anterior keratometry had a significant reduction 12 months after AICI insertion (P< 0.001). Primary coma and spherical aberration values showed a significant increase (both, P < 0.05). Our results showed 100% safety (safety index: 1.8) and 45% efficacy (efficacy index: 1). CONCLUSIONS: AICI implantation seemed to be a safe and effective procedure for improving visual acuity and refractive outcomes in subjects with keratoconus.