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.].

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.

[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.

Effect of preoperative pupil offset on corneal higher-order aberrations after femtosecond laser-assisted in situ keratomileusis.

BACKGROUND: This study aimed to investigate the relationship between multiple higher-order aberrations (HOAs) subgroups and pupil offset, as well as to analyze the factors affecting postoperative corneal HOAs in patients with different degrees of refractive errors. METHODS: We enrolled 160 patients (316 eyes) aged ≥ 18 years who had undergone femtosecond laser-assisted in situ keratomileusis (FS-LASIK) treatment. Based on the relationship between the preoperative pupil offset and the postoperative ΔHOAs, all patients were divided into two groups: group I (pupil offset ≤ 0.20 mm) and group II (pupil offset > 0.20 mm). All of the eyes had low to high myopia with or without astigmatism (manifest refraction spherical equivalent (MRSE) < -10.00 D). Uncorrected distance visual acuity, corrected distance visual acuity, MRSE, pupil offset, central corneal thickness, corneal HOAs, vertical coma (Z3-1), horizontal coma (Z31), spherical aberration (Z40), trefoil 0° (Z33), and trefoil 30° (Z3-3) over a 6 mm diameter central corneal zone diameter were evaluated preoperatively and at 1 and 3 months postoperatively. RESULTS: Our result revealed significant differences in postoperative corneal total root mean square (RMS) HOAs, RMS vertical coma, RMS horizontal coma, RMS spherical aberration, and RMS trefoil 30° between group I and group II. ΔMRSE was found to be an effective factor for ΔRMS HOAs (R2 = 0.383), ΔRMS horizontal coma (R2 = 0.205), and ΔRMS spherical aberration (R2 = 0.397). In group II, multiple linear regression analysis revealed a significant correlation between preoperative pupillary offset and Δtotal RMS HOAs (R2 = 0.461), ΔRMS horizontal coma (R2 = 0.040), and ΔRMS trefoil 30°(R2 = 0.089). The ΔRMS vertical coma effect factor is the Y-component, and the factor influencing ΔRMS spherical aberration was ΔMRSE (R2 = 0.256). CONCLUSION: A small pupil offset was associated with a lower induction of postoperative corneal HOAs. Efforts to optimize centration are critical for improving surgical outcomes in patients with FS-LASIK.

Corneal higher-order aberrations in corneal endothelial decompensation secondary to obstetric forceps injury.

Forceps corneal injuries during infant delivery cause Descemet membrane (DM) breaks, that cause corneal astigmatism and corneal endothelial decompensation. The aim of this study is to characterise corneal higher-order aberrations (HOAs) and corneal topographic patterns in corneal endothelial decompensation due to obstetric forceps injury. This retrospective study included 23 eyes of 21 patients (54.0 ± 9.0 years old) with forceps corneal injury, and 18 healthy controls. HOAs and coma aberrations were significantly larger in forceps injury (1.05 [0.76-1.98] µm, and 0.83 [0.58-1.69], respectively) than in healthy controls (0.10 [0.08-0.11], and 0.06 [0.05-0.07], respectively, both P < 0.0001). Patient visual acuity was positively correlated with coma aberration (rs = 0.482, P = 0.023). The most common topographic patterns were those of protrusion and regular astigmatism (both, six eyes, 26.1%), followed by asymmetric (five eyes, 21.7%), and flattening (four eyes, 17.4%). These results indicate that increased corneal HOAs are associated with decreased visual acuity in corneal endothelial decompensation with DM breaks and corneal topography exhibits various patterns in forceps injury.

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

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

Wavefront aberrations caused by biomechanical effects after Small Incision Lenticule Extraction (SMILE) based on finite element analysis.

To examine wavefront aberrations induced by biomechanical effects after Small Incision Lenticule Extraction (SMILE) surgery. The three-dimensional (3D) finite element models of the human eye were established. By loading the intraocular pressure (IOP), the displacement of the anterior and posterior surface of the cornea was calculated. Then the displacement was converted into the wavefront aberrations by wave-surface fitting. The results showed that the induced wavefront aberrations were noticeable from biomechanical effects after SMILE surgery. The induced higher-order aberrations from the anterior corneal surface included spherical aberration, y-Trefoil, and x-Tetrafoil. Spherical aberration was positively correlated with corrected diopter (D), but x-Tetrafoil and y-Trefoil remained stable. The induced wavefront aberrations from the posterior corneal surface were smaller than those from the anterior corneal surface, and some of the aberrations compensated each other. With IOP increased, defocus and x-Tetrafoil from the anterior corneal surface increased, while y-Trefoil and spherical aberration decreased. The IOP only affected defocus from the posterior corneal surface. In addition, the incision size also had a distinct impact on primary x-astigmatism and x-Trefoil from the anterior corneal surface, and it had a smaller effect on the aberrations from the posterior corneal surface. Therefore, the biomechanical effects increased residual wavefront aberrations after SMILE refractive surgery.

Analysis of Corneal Scheimpflug Densitometry and Ocular Wavefront Aberrations Post Descemet Stripping Automated Endothelial Keratoplasty.

PURPOSE: To assess the role of corneal densitometry and wavefront aberrations post Descemet stripping automated endothelial keratoplasty (DSAEK) and their correlation with visual acuity. METHODS: Twenty-seven eyes of 25 patients with nonresolving corneal edema for more than 3 months as a result of Fuchs endothelial corneal dystrophy, pseudophakic bullous keratopathy, or secondary endothelial dysfunction were enrolled in a prospective interventional study and underwent DSAEK. Postoperative evaluation for corneal aberrations, including Higher order aberrations (HOAs) and corneal densitometry (CD), was performed using anterior-segment optical coherence tomography (Avanti RTvue XR; Optovue) and Scheimpflug imaging (Pentacam, Oculus Optikgeräte GmbH, Wetzlar, Germany) at 6 months. A correlation analysis of corneal aberrations, including HOAs and CD, with postoperative best-corrected visual acuity at 6 months was performed. RESULTS: Mean best-corrected visual acuity (BCVA) improved from 1.67±0.53 log of minimum angle of resolution (logMAR) to 0.2±0.22 logMAR post DSAEK at 6 months (P≤0.0001). At 6 months, mean root-mean-square (RMS) total corneal aberrations (includes HOA and low-order aberration [LOA]), RMS total HOA, and RMS LOA of the central 6-mm zone were 4.99±2.64, 1.80±0.9, and 4.55±2.64, respectively. The mean corneal densitometry from anterior, central, and posterior zones were 39.12±12.77, 23.9±7.2, and 13.54±2.04 gray scale units, respectively. Total anterior aberrations (r=0.051; P=0.006), anterior LOA (r=0.049; P=0.009), total corneal aberrations (r=0.051; P=0.001), total HOAs (r=0.095; P=0.057) and LOAs (r=0.050; P=0.002), and total CD from 0 to 2 mm (r=0.010; P=0.038) and 2 to 6 mm (r=0.014; P=0.018) showed a significant inverse correlation with postoperative BCVA. CONCLUSION: There was an inverse relationship between post DSAEK BCVA and total corneal HOAs and full-thickness densitometry at 6 months. Scheimpflug imaging with added tools for corneal aberration and densitometry analysis gives further insight into the suboptimal vision achieved despite transparent corneas post DSAEK.

Effect of Wavefront Aberrations on Night Vision Problems and Mesopic Contrast Threshold After SMILE.

PURPOSE: To investigate the effect of wavefront aberrations on night vision problems and mesopic contrast threshold after small incision lenticule extraction (SMILE). METHODS: Forty-two participants (84 eyes) who underwent SMILE were included in this prospective observational study. Visual outcomes including uncorrected distance visual acuity (UDVA), subjective manifest refraction, mesopic contrast threshold (Binoptometer 4P; Oculus Optikgeräte GmbH), and higher order aberrations (HOAs) were analyzed before and 3 months after surgery. The patient's night vision satisfaction was assessed using a questionnaire. RESULTS: The mean spherical equivalent was -5.30 ± 1.38 diopters (D) preoperatively and -0.06 ± 0.15 D postoperatively. UDVA was better than 20/20 in 98.81% of the patients and better than 20/25 in all patients. Scores of night vision satisfaction and glare changed significantly in the postoperative period (F = 8.463, P = .001; F = 69.518, P < .001, respectively). Preoperative spherical diopters (lower order aberrations) were positively correlated with night vision satisfaction (r = -0.329, P = .041) and glare score (r =-0.332, P = .039). Age (odds ratio [OR] = 1.272, 95% CI = 1.019 to 1.589) and preoperative spherical diopter (OR = 0.437, 95% CI = 0.199 to 0.975) were correlated with night vision satisfaction scores by analysis of binary regression. The root mean square value of total HOAs increased 3 months after surgery (t = -6.873, P < .001) with an increase in horizontal coma (Z31) and spherical aberration (Z40) (P < .001). No correlation was observed between glare score and HOAs; however, patients with higher preoperative myopia demonstrated continuously decreasing contrast under mesopic conditions and higher postoperative horizontal coma. CONCLUSIONS: Myopic patients with higher preoperative spherical errors experienced more glare at night after SMILE surgery. Postoperative horizontal coma was associated with worse mesopic contrast thresholds. [J Refract Surg. 2021;37(7):446-452.].

Long-term changes in contrast-sensitivity, corneal topography and higher-order aberrations after upper eyelid blepharoplasty: A prospective interventional study.

PURPOSE: The aim of this study was to analyze the long-term changes in visual parameters, that is, contrast sensitivity (CS) and higher-order aberrations (HOAs), and corneal topography in the patients undergoing upper eyelid blepharoplasty (UEB) for dermatochalasis. METHODS: This was a prospective, single surgeon, intervention study including patients (≥40 years age) having severe dermatochalasis with a minimum post-UEB follow-up of 12 months. The preoperative readings of CS (using Pelli-Robson chart), HOAs (using WaveLight ALLEGRO analyzer), and corneal topography (using topographic modeling system-4, Tomey corporation) were noted and compared at 3, 6, and 12 postoperative months. RESULTS: We studied 30 patients (60 eyes) who underwent bilateral UEB. The majority of patients were females (n = 21,70%), and the mean age of patients was 56.53 ± 9.06 years. The preoperative and postoperative values of LogMAR visual acuity, log CS value, corneal topography measurements (K1, K2, cylinder value, and the axis), optical aberrations (total HOAs; third-order--trefoil & coma; four-order--spherical aberrations and secondary astigmatism, and tetrafoil) were compared. At 12 months, the mean CS value, the majority of HOAs, and corneal topography (only cylinder values) showed a stable, statistically significant difference in the postoperative period. CONCLUSION: The UEB may produce long-term, visually-beneficial, optical, and corneal changes. The patients undergoing cataract surgery aiming for spectacle independence may gain additional visual benefits with UEB.

Short and long term outcomes after small-incision lenticule extraction: A tertiary referral centre experience.

PURPOSE: The objective of this study is to evaluate the preoperative and short- and long-term postoperative results in terms of visual acuity, refractive error, and corneal wavefront aberrations in patients with myopia and myopic astigmatism undergoing small incision lenticule extraction (SMILE). METHODS: Seventy-nine eyes of 52 myopes with or without astigmatism (41 right and 38 left) were enrolled in this retrospective study. The measurements included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SE) and wavefront aberrations. All the measurements before and after SMILE surgery were systematically recorded. RESULTS: Mean preoperative UDVA was 1.19±0.24 logMAR and improved to 0.06±0.17 logMAR at the 3-year postoperative follow-up. At the conclusion of the 3-year follow-up, UDVA was better than or equal to 20/20 and 20/25 in 73% and 84% of eyes, respectively. At 1 month postoperatively, CDVA was 0.05±0.23 logMAR and significantly lower than the preoperative CDVA, 0.02±0.04 log MAR (P>0.05). However, at 1 year and 3 years after surgery, CDVA showed a significant increase compared to preoperative CDVA. At the conclusion of the 3-year follow-up, SE was -0.47 D, and 69.6% and 83.5% of the eyes were within±0.50 D and±1.00 D, respectively, of the intended correction. HOA's, coma, and spherical aberration increased significantly. No significant change in trefoil was detected. CONCLUSION: This study showed that SMILE produces a stable, safe outcome for surgical treatment of myopia and myopic astigmatism.

Theoretical Analysis of Wave-Front Aberrations Induced from Conventional Laser Refractive Surgery in a Biomechanical Finite Element Model.

Purpose: To examine the biomechanical effects-induced wave-front aberrations after conventional laser refractive surgery. Methods: A finite element model of the human eye was established to simulate conventional laser refractive surgery with corrected refraction from -1 to -15 diopters (D). The deformation of the anterior and posterior corneal surfaces was obtained under the intraocular pressure (IOP). Then, the surface displacement was converted to wave-front aberrations. Results: Following conventional refractive surgery, significant deformation of the anterior and posterior corneal surfaces occurred because of the corneal biomechanical effects, resulting in increased residual wave-front aberrations. Deformation of the anterior surface resulted in a hyperopic shift, which was significantly increased with the increasing refractive correction. The residual high-order aberrations consisted of spherical aberration, vertical coma, and y-trefoil. Spherical aberration was significantly positively correlated to enhanced refraction correction. The effect of posterior corneal surface on induced wave-front aberration was less than the anterior corneal surface. The IOP slightly affects the postoperative defocus, coma, and spherical aberration. When treatment decentration occurred during the procedure, the hyperopic shift decreased as the eccentricity increased. Treatment decentration had a significant impact on the spherical aberration and the coma. In addition, the ocular tissue elasticity played a key role in hyperopic shift, whereas it had little effect on the other aberrations. Conclusions: Among the many factors that affect high-order aberrations after conventional laser refractive surgery, the alterations in corneal morphology caused by biomechanical effects must be considered, as they can lead to an increase in postoperative residual wave-front aberrations.

Corneal wavefront aberrations and subjective quality of vision after small incision lenticule extraction.

PURPOSE: To analyse in depth the associations between objectively measured corneal higher-order aberrations (HOAs) and subjectively perceived visual quality after small incision lenticule extraction (SMILE) as quantified with the standardized and clinically validated quality of vision (QOV) questionnaire. METHODS: This cross-sectional study included patients after bilateral simultaneous SMILE for the treatment of myopia and/or myopic astigmatism with plano target refraction. Scheimpflug imaging (Pentacam HR; Oculus Optikgeräte GmbH, Wetzlar, Germany) was used to objectively quantify corneal HOAs. The standardized and validated QOV questionnaire was employed to gauge patients' subjectively perceived visual quality regarding frequency, severity and bothering effect of visual disturbances. RESULTS: A total of 394 eyes of 197 patients with a mean age of 32.4 ± 7.7 years and a mean postoperative follow-up of 24.3 ± 14.1 months were included. SMILE induced a statistically significant (p < 0.001) increase in spherical aberration (0.074 ± 0.131 µm), coma (0.142 ± 0.179 µm), trefoil (0.018 ± 0.067 µm) as well as in total HOAs (0.191 ± 0.176 µm). Surgically induced and postoperative levels of HOA showed no correlation with the three QOV scores representative of overall visual symptom frequency, severity and bothering effect (all R2 values ≤ 0.016). In addition, the associations between specific visual symptoms (e.g. starburst) and singular HOA terms (e.g. haloes) were very weak (all Rho values ≤ 0.164). CONCLUSIONS: Small incision lenticule extraction induced significant amounts of corneal HOAs that, however, showed no clear relationships to patient-reported QOV or specific long-term visual symptoms.

Factors predicting successful customized excimer laser treatment in irregular corneas.

PURPOSE: To identify factors associated with a successful wavefront-guided customized treatment (WG-CT) with an excimer laser in highly aberrated corneas. SETTING: VISSUM Alicante Spain. DESIGN: Retrospective consecutive noncomparative case series. METHODS: Treatment was performed with the WG-CT Amaris excimer laser using the ORK-CAM software for the calculation of the ablation profile. Eyes of patients with significantly aberrated corneas, including postrefractive and keratoplasty procedures or high irregular astigmatism with significant higher-order aberrations (HOAs) that had WG-CT were included. Refractive outcomes, HOAs, and visual outcomes were recorded. Statistical analysis was performed to identify factors associated with technical (based on HOAs) or refractive outcome success. RESULTS: The study included 55 treatments of 51 eyes (35 patients). The postoperative uncorrected distance visual acuity was 0.2 logarithm of the minimum angle of resolution or better in 72% of the eyes, and the postoperative residual manifest refraction spherical equivalent was ±0.50 diopter in 56% of the eyes, whereas 11% of the eyes lost 1 line or more in corrected distance visual acuity. Successful reduction in the total root mean square (RMS) of HOAs occurred in 36 eyes (65%), and these eyes had a significantly higher preoperative RMS of HOAs (1.45 ± 0.93 µ vs 0.91 ± 0.34 µ, P = .003) and preoperative coma-like aberrations (1.09 ± 0.83 µ vs 0.55 ± 0.28 µ, P = .001). In multivariate analysis, posthyperopic treatment eyes were less likely to achieve refractive outcome success (odds ratio = 0.09, P = .02). CONCLUSIONS: WG-CT in highly aberrated corneas had a limited refractive predictability. Eyes with preoperative coma-like aberrations are more likely to benefit from a reduction in HOAs. Posthyperopic treatment is associated with a higher rate of refractive surprises.

Comparison of Higher-Order Aberrations after LASEK between Two Different Laser Platforms for Low-to-Moderate Myopia.

PURPOSE: To compare the differences in higher-order aberrations (HOAs) after laser subepithelial keratomileusis (LASEK) between two different laser platforms. METHODS: One hundred and seven eyes of 107 patients were included in this study. Fifty-six eyes underwent LASEK with the Triple-A profile (an ablation profile of the MEL 90 excimer laser) and 51 eyes underwent LASEK with the aspheric (Aberration Smart Ablation [ASA]) profile. Uncorrected distance visual acuity, corrected distance visual acuity (CDVA), corneal topography, and ocular aberrations were measured before and 6 months postoperatively. RESULTS: In the ASA group, the values of horizontal trefoil, vertical coma, horizontal coma, spherical aberrations, and total HOAs increased significantly after surgery (all P < 0.05). There were no significant differences in the vertical trefoil between the preoperative and 6-month postoperative periods. In the Triple-A group, there were no differences in vertical trefoil and horizontal trefoil values between the preoperative and 6-month postoperative periods. Compared with the preoperative values, vertical coma, horizontal coma, spherical aberrations, and total HOAs were significantly increased at 6 months after surgery (all P < 0.05). Compared to the Triple-A group, higher horizontal trefoil and horizontal coma were introduced in the ASA group at 6 months postoperatively. CONCLUSION: The Triple-A ablation profile of the MEL 90 excimer laser at a 500-Hz pulse rate was an efficient method to correct myopia, especially for mild-to-moderate myopia, compared with the aspheric ablation model, fewer horizontal trefoil and horizontal coma were induced at 6 months after LASEK. ABBREVIATIONS: HOAs, Higher-Order Aberrations; LASEK, laser subepithelial keratomileusis; ASA, Aberration Smart Ablation; UDVA, uncorrected distance visual acuity; CDVA, corrected distance visual acuity.

HIGHER-ORDER ABERRATIONS IN EYES WITH SILICONE OIL TAMPONADE.

PURPOSE: To investigate the changes in higher-order aberrations (HOAs) after silicone oil removal and to evaluate their associations with visual acuity. METHODS: Fifty-nine eyes of 58 patients who underwent SO removal were included. Total, corneal, and internal optic HOAs, and best-corrected visual acuity were measured before and 1 month after SO removal, and changes were compared between phakic and pseudophakic eyes. RESULTS: Total ocular and internal optic HOAs decreased significantly after SO removal both in pseudophakic (n = 40, all P < 0.001) and phakic eyes (n = 19, P = 0.017, P = 0.004). Preoperative HOAs (P < 0.001) and changes in HOAs (P = 0.006) were greater in pseudophakic eyes than in phakic eyes. Best-corrected visual acuity was significantly improved after SO removal, from 20/105 to 20/78 (P < 0.001) in pseudophakic eyes, whereas there was no difference in phakic eyes (P = 0.714). Preoperative HOAs and the reduction in HOAs after SO removal were greater in best-corrected visual acuity-improved eyes than best-corrected visual acuity-unchanged eyes (P < 0.001). CONCLUSION: Silicone oil tamponade induced an increase in HOAs, and these increases were greater in pseudophakic eyes than in phakic eyes. Silicone oil may cause additional visual impairments because of HOAs, beyond those caused by retinal diseases, particularly in pseudophakic eyes.

Two-year observation of posterior corneal elevations after small incision lenticule extraction (SMILE) for myopia higher than -10 dioptres.

AIM: To investigate the change in posterior corneal elevations (PCEs) of eyes with extremely high myopia 2 years after small incision lenticule extraction (SMILE). METHODS: We evaluated 39 eyes of 39 patients with spherical equivalent higher than -10.00 dioptres (D). Using a Scheimpflug camera (Pentacam), we measured change in PCEs at 1 day, 3 months, 6 months and 2 years after SMILE. Another 34 eyes of 34 patients who underwent femtosecond laser-assisted in situ keratomileusis (FS-LASIK) were examined before, at 1 day and long-term after surgery as the control group. For each eye, elevations at central, thinnest, maximal points and 24 other predetermined points were measured. RESULTS: No significant forward displacements of PCEs were observed in both surgeries. The maximal but not significant forward displacement occurred around 3-6 months following SMILE, and all returned to original levels 6 months postoperatively except superior area. The peripheral area tended to displace backward, while the central area tended forwardly. In both procedures, elevations along horizontal meridians, inferior and temporal hemispheres were significantly higher than those along vertical meridians, superior and nasal hemispheres, respectively (p<0.05). Elevation on the 4 mm, 6 mm diameters at 1 day and on the 6 mm diameter and temporal hemisphere at long-term follow-up postoperatively were significantly higher in FS-LASIK than SMILE (p<0.05). Change in elevations on the 6 mm diameter circle correlated with residual bed thickness (p=0.047). CONCLUSIONS: SMILE is a safe way to correct for myopia higher than -10 D, with PCEs remaining stable 2 years after surgery.

Accommodation response and spherical aberration during orthokeratology.

PURPOSE: To evaluate the changes in the accommodative response and in the corneal and internal spherical aberration during 3 months of wear of orthokeratology lenses from the baseline. METHODS: Fifty children aged 8 to 17 were recruited for a prospective study and were fitted with orthokeratology lenses. Refraction without cycloplegia, high and low uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), accommodation lag, horizontal near phoria without correction, corneal topography, corneal, and total wavefront aberration were performed at baseline, 1 day, 1 week, 1 month, and 3 months. Data were analyzed by Student's t test for related samples, repeated measures ANOVA test, and Pearson correlation test. RESULTS: The spherical equivalent (SE) before and after 3 months was - 3.33 ± 1.60 D and - 0.30 ± 0.46 D, respectively. Accommodation lag was 0.53 ± 0.38 D and 0.20 ± 0.33 D at baseline and at 3 months, respectively. A moderate correlation between lag at the baseline and its change between baseline and the 3-month visit was found (P < 0.05; R = 0.748). The spherical aberration (SA) increased for anterior corneal and total measurement, being statistically significant for all visits (P < 0.05). The internal SA decreased: - 0.105 ± 0.006 at baseline and - 0.196 ± 0.203 at 1 week (P < 0.05). No difference between baseline and the follow-up visits in posterior corneal SA was found (P > 0.05) CONCLUSION: The negative SA of the lens increases during OK treatment compensated for the increase of the anterior corneal surface positive SA, in addition to increasing the accommodative response.

Prospective, randomized, eye-to-eye comparison of a new silicone corneal shield versus conventional bandage contact lens after photorefractive keratectomy.

PURPOSE: To compare uncorrected distance visual acuity (UDVA) and patient-reported outcomes with a new silicone corneal shield and a conventional bandage contact lens (BCL) after photorefractive keratectomy (PRK). SETTING: Stanford Eye Laser Center (Palo Alto, California) and Slade & Baker Vision (Houston, Texas). DESIGN: Prospective randomized cohort study. METHODS: Standardized bilateral wavefront-guided or wavefront-optimized PRK was performed in 25 patients with myopia. Each patient's dominant eye was randomized to either a silicone corneal shield or a conventional BCL, which was placed at the conclusion of surgery. The contralateral eye was assigned the other intervention. The UDVA and patient-reported outcomes were measured preoperatively, 1 hour after surgery, and at 1, 2, 3, 4, and 7 days postoperatively. RESULTS: At 1 day postoperatively, the mean logarithm of the minimum angle of resolution (logMAR) UDVA was 0.04 ± 0.16 (SD) in the silicone corneal shield group and 0.29 ± 0.22 in the BCL group (P < 0.01). At 7 days postoperatively, the mean logMAR UDVA was 0.09 ± 0.17 in the silicone corneal shield group and 0.23 ± 0.24 in the BCL group (P = .01). At 1 day through 3 days postoperatively, the patients reported greater pain, discomfort, foreign body sensation, and heavy eyelid in the eye with the silicone corneal shield. There was no statistically significant difference in the survey outcomes between the two groups at 4 days and 7 days postoperatively. CONCLUSIONS: The new silicone corneal shield was safe and effective, with faster visual recovery and a trend toward quicker epithelialization; however, it might be less comfortable than a conventional BCL.

One-year follow-up of changes in refraction and aberrations induced by corneal incision.

PURPOSE: To evaluate the surgically induced changes in refraction (sphere and astigmatism) and higher order aberrations by corneal incision for one year. SETTING: University Hospital "Virgen de la Arrixaca", Murcia, Spain. DESIGN: Retrospective interventional case series. METHODS: Corneal power, astigmatism and higher order aberrations (HOA) were calculated from corneal topography measured in 27 eyes prior to surgery and at 2 weeks, 1, 2, 3 and 6 months and 1 year following cataract surgery with 3.2-mm corneal incision. At every stage, optical changes were calculated as the difference between pre- and post-surgery data (in each follow-up) using the formulas of obliquely crossed cylinders for the refraction and Zernikes coefficients for HOA. RESULTS: At 2 weeks after surgery the mean corneal values of induced sphere, cylinder and the root mean square (RMS) of HOA were +0.54±0.27 D, -0.77±0.32 D and 0.15 microns respectively. These parameters decreased significantly (p-values between 0 and 0.01) at 3 months to +0.33±0.27 D sphere, -0.50±0.24 D cylinder and 0.10±0.05 microns HOA and were stable at the next follow-ups. Induced spherical equivalent was around zero at all visits. The changes in HOA were mainly due to trefoil aberration. CONCLUSIONS: Linear corneal incisions do not change the spherical power but can induce significant values of astigmatism and trefoil aberration in the cornea. However, these changes revert fully or partially to preoperative values by the third month after surgery and remain stable with time.