Postoperative Spherical Aberration Research Articles

The Influence of Axial Length on Visual Quality following SMILE Surgery in Patients with High Myopia.

This retrospective study aimed to investigate the subjective and objective visual outcomes following Small Incision Lenticule Extraction (SMILE) surgery in high myopic patients with varying axial lengths (AL). The study enrolled 113 highly myopic patients (202 eyes) who underwent SMILE surgery at Shanghai's Tenth People's Hospital from July 2021 to September 2023. Patients were classified into three groups based on the axial length before surgery: Group A (AL < 26mm, 62 eyes), Group B (26mm ≤ AL < 27mm, 88 eyes), and Group C (AL ≥ 27mm, 52 eyes). Preoperative and postoperative evaluations included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), equivalent spherical error, and ocular higher-order aberrations. Subjective visual quality was assessed using the Quality of Vision (QoV) questionnaire. One year postoperatively, there were no notable differences found in safety, efficacy, or stability among the groups (P>0.05). Postoperative spherical aberration, horizontal, and vertical coma increased compared to preoperative values and showed a positive association with axial length (P<0.05). Horizontal and vertical trefoil remained stable at all follow-up points without any significant inter-group variances (P>0.05). Postoperative QoV scores were obviously higher in Groups A (45.45±5.49) and B (46.34±3.25) compared to Group C (49.15±7.89). There was no correlation between QoV scores and axial length observed. The induced horizontal trefoil showed a positive correlation with changes in lens thickness (LT) one year after SMILE (r=0.22, p=0.03). SMILE surgery is a safe and effective approach for correcting high myopia, exhibiting a significant correlation observed between ocular high-order aberrations and axial length.

Comparison of Short-Term Clinical Outcomes After Implantation of Two Monofocal, Aspheric Intraocular Lenses.

This study compared the visual outcomes and optical quality of two monofocal, aspheric intraocular lenses (IOLs; CT LUCIA 621P, Carl Zeiss Meditec; Eyhance ICB00, Johnson & Johnson Vision) by evaluating visual acuity, contrast sensitivity, and higher-order aberrations 1 month post-cataract surgery. In this retrospective, comparative study, 120 eyes (72 patients) that underwent cataract surgery with either CT LUCIA 621P (Lucia group) or Eyhance ICB00 (Eyhance group) implantation (60 eyes/group) were retrospectively investigated. Visual acuity at various distances and defocus curves were measured 1 month postoperatively. Optical quality was assessed by comparing contrast sensitivity and internal coma, spherical, and total aberrations by using iTrace (Tracey Technology), a ray-tracing-type aberrometer. The visual acuity and defocus curves were similar between the two IOLs 1 month postoperatively. The Lucia group showed better contrast sensitivity at higher spatial frequencies: 12 cpd (p < 0.001, 1.32 LogCS vs. 1.02 LogCS) and 18 cpd (p = 0.009, 0.74 LogCS vs. 0.47 LogCS) unilaterally and 18 cpd (p = 0.044, 0.94 LogCS vs. 0.60 LogCS) bilaterally. Postoperative internal spherical aberration was significantly lower in the Lucia group (p < 0.001, -0.04 µm vs. -0.003 µm). Internal coma and total aberrations were similar. The visual acuity and defocus curves of the Lucia and Eyhance groups were comparable 1 month post-cataract surgery. The Lucia group's superior contrast sensitivity and lower postoperative internal spherical aberration were due to differences in IOL designs, particularly the power variation patterns.

Efficacy of small incision lenticule extraction combined with femtosecond laser-assisted in situ keratomileusis for optimized monovision correction in myopia patients with presbyopia

Objective: To evaluate the efficacy of optimized monovision correction using small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) in myopic patients with presbyopia and to assess the corneal epithelial remodeling following these procedures. Methods: A prospective study was conducted. Thirty-two patients (64 eyes) with myopia and presbyopia who underwent surgical correction at Chongqing Bai Ji Eye Clinic from August 2021 to April 2023 were continuously included. There were 9 males and 23 females, with an average age of (44.25±2.96) years. The dominant eyes (32 eyes) underwent SMILE, while the non-dominant eyes (32 eyes) underwent FS-LASIK with mild myopia and partial negative spherical aberration induction. Data on visual acuity and refraction were collected preoperatively and at 1 week, 1 month, 3 months, and 6 months postoperatively. Total ocular aberrations were measured using the iProfiler Plus, and the corneal epithelial thickness in different regions was assessed using anterior segment optical coherence tomography. Safety and efficacy indices were calculated based on visual acuity, the defocus and contrast sensitivity were measured using the Binoptometer 4P binocular vision tester, and a patient satisfaction survey was performed. Results: At 1 week postoperatively, the uncorrected distance visual acuity (UDVA) of dominant eyes significantly improved compared to preoperative values. At 3 months postoperatively, the uncorrected near visual acuity (UNVA) of non-dominant eyes showed significant improvement (P<0.05), 96.9% (31 eyes) of the dominant eyes achieved UDVA of 1.0 or better, and 93.8% (30 eyes) of the non-dominant eyes achieved UNVA of 0.8 or better. The safety index for distance vision was 1.15±0.09, and the efficacy index was 1.15±0.11. At 1 week, 1 month, 3 months, and 6 months postoperatively, the proportion of dominant eyes with a spherical equivalent (SE) deviation within ±0.50 D of the target was 90.6% (29 eyes), 90.6% (29 eyes), 93.8% (30 eyes), and 96.2% (31 eyes), respectively; for non-dominant eyes, the corresponding proportions were 81.3% (26 eyes), 87.5% (28 eyes), 93.8% (30 eyes), and 96.2% (31 eyes). The postoperative spherical aberration was (0.11±0.03) μm for dominant eyes and (-0.01±0.04) μm for non-dominant eyes, showing a statistically significant difference (P<0.05). At 1 week and 1 month postoperatively, the central corneal epithelial thickness of non-dominant eyes was significantly higher than that of dominant eyes [(71.34±21.69) μm vs. (51.97±6.33) μm at 1 week, and (61.34±15.85) μm vs. (52.72±6.32) μm at 1 month; P<0.05]. Patient satisfaction was high, with 96.9% (31 patients) rating their satisfaction as "satisfactory" or higher. Conclusions: The combined use of SMILE and FS-LASIK for optimized monovision correction in myopic patients with presbyopia is both safe and effective, achieving high postoperative satisfaction. The SMILE procedure reduces the extent of corneal epithelial remodeling compared to FS-LASIK.

Comparison of clinical outcomes of a corneal wavefront- and topography-guided platforms for laser in situ keratomileusis on virgin eyes: an expanded cohort study

PurposeTo compare the clinical outcomes of myopiacorrected with corneal-wavefront-guided (CWG) laser in situ keratomileusis (LASIK) with AMARIS 1050S (SCHWIND eye-tech-solutions GmbH & Co. KG) and corneal-topography-guided (CTG) LASIK with WaveLight EX500 (Alcon Laboratories, Fort Worth, TX).MethodsIn this prospective, pseudo-randomized expanded cohort study, a total of 266 patients were subjected to binocular LASIK surgery, either with WaveLight EX500 (WaveLight group) or Amaris 1050S (AMARIS group) platforms. Data related to right eyes were selected for analysis. Corneal higher-order aberration (HOA) was selected as the primary endpoint; while visual acuity and refraction were the secondary endpoints. All the endpoints were assessed at 3 months postoperatively.ResultsThere were 134 eyes in the AMARIS group and 132 eyes in the WaveLight group. After 3 months of postoperative follow-up, spherical and coma aberrations were significantly lower (P < 0.05) in the WaveLight group (spherical aberration: − 0.104 ± 0.199 µm; coma aberration: − 0.117 ± 0.202 µm) in comparison with the AMARIS group (spherical aberrations: 0.254 ± 0.146 µm; coma aberrations: 0.316 ± 0.297 µm). In the AMARIS group, 96.3% of the eyes achieved an uncorrected distance visual acuity (UDVA) of 20/20 while in the WaveLight group, 96.2% of the eyes achieved an UDVA of 20/20. Furthermore, the mean postoperative manifest refraction spherical equivalent (MRSE) was − 0.02 ± 0.28 in the AMARIS group and − 0.05 ± 0.21 in the WaveLight group (P = 0.34).ConclusionsBoth WaveLight EX500 and Amaris 1050S LASIK showed excellent refractive and visual outcomes. In addition, the WaveLight group showed minimal spherical and coma aberrations when compared to the AMARIS group.

Change in posterior astigmatism with degree of decentring graft in patients with descemet stripping automated endothelial keratoplasty

Aims/Purpose: Aligning the center of grafts in patients with Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) is difficult but important process. We investigated how the graft centring affected posterior astigmatism in patients.Methods: This study analysed 63 patients (63 eyes) who received DSAEK. Postoperative posterior astigmatism of patients was measured using pentacam, and the decentring of the graft was measured by using the distance between the patient's optic centre and the centre of the graft. Correlation analysis was performed on the relationship between graft decentring and posterior astigmatism. In addition, the spherical aberration of the cornea before and after surgery was analysed and investigated.Results: The average posterior astigmatism of the patients before surgery was 1.70 ± 2.25, and the average posterior astigmatism was 0.66D ± 0.43, confirming a decrease in posterior astigmatism after surgery (p &lt; 0.05). The mean decentring of graft was 0.45 ± 0.33 mm. Preoperative spherical aberration was 0.192 ± 0.53 and postoperative spherical aberration was 0.044 ± 0.37, and these differences were not statistically significant (p &gt; 0.05). Analysis of the relationship between graft decentring and postoperative posterior astigmatism showed no statistically significant correlation (p &gt; 0.05).Conclusions: In this study, no significant correlation was found between centring of the graft and posterior astigmatism after surgery. However, centring of the graft in DSAEK plays an important role in graft survival and postoperative prognosis, surgeons should pay attention to centring well during surgery.

The effect of different angle kappa on higher-order aberrations after small incision lenticule extraction

This study aimed to compare higher-order aberrations (HOAs) after small incision lenticule extraction (SMILE) in patients with different angle kappa. This is a retrospective report in which 341 right eyes of 341 patients who were subjected to SMILE, which used coaxially sighted corneal light reflex (CSCLR) as the treatment zone centered, treated by the same experienced surgeon (LHB) for correction of myopia and myopic astigmatism, preoperative and postoperative spherical equivalent (SE), angle kappa, total higher-order aberrations (total HOA), spherical aberration (SA), vertical coma (VC), horizontal coma (HC), oblique trefoil (OT), and horizontal trefoil (HT), were compared. SMILE showed outstanding performance in terms of safety, efficacy, and predictability. In addition, a comparison of preoperative and postoperative HOAs exhibited the difference of total HOA (P < 0.01), SA (P < 0.01), VC (P < 0.01), and HC (P < 0.01), which was statistically significant; however, for OT and HT with the longer follow-up time, the statistical difference gradually decreased. For stratification of angle kappa into groups based on decantation, angle kappa was divided into three major groups: r < 0.1 mm, 0.1 ≤ r < 0.2 mm, and r ≥ 0.2 mm; the changes of SA (F = 4.127, P = 0.021) and OT (F = 3.687, P = 0.031) exhibited significant difference after 1 year of SMILE. We performed a correlation analysis of all preoperative and postoperative parameters, and the results indicated that the preoperative total HOA was negatively correlated with preoperative cylindrical diopter (DC), and postoperative total HOA, SA, and coma were affected by spherical diopter (DS) and SE. Moreover, we also found a significant difference of SA and VC in the early postoperative with preoperative. SA was positively correlated with Y values and r of 1 year after SMILE. All of the analyzed parameters in the three groups, except for the trefoil, gradually increased over time; however, the trefoil could gradually stabilize over time. We also divided angle kappa into four groups by quadrants; the result showed that the effects of higher-order aberrations were markedly different from the various quadrants. Patients with large angle kappa were able to increase VC and SA postoperatively, and higher HOAs were more significant in patients with high myopia. The differences in quadrants exhibited a diversity of HOAs; this could be attributed to the corneal surface reestablishment and the alteration of angle kappa, but the trend was not apparent. Although all patients displayed increased HOAs after SMILE, the potential application of CSCLR as the treatment zone centered still showed excellent safety, efficacy, and predictability.

Visual Outcomes Early after Implantable Collamer Lens V4c Implantation in Different Preoperative Spectacle Correction: Full Correction vs. Under Correction

Purpose To investigate visual outcomes early after implantable collamer lens (ICL) V4c implantation between patients with fully corrected and under-corrected spectacles preoperatively. Methods Patients who implanted ICL V4c were divided into the full correction (46 eyes/23 patients) and under-correction groups (48 eyes/24 patients) based on preoperative differences between the spherical diopter of the spectacles and the actual spherical diopter. Refractive outcomes, scotopic pupil size, higher-order aberrations, and subjective visual outcomes as assessed using a validated questionnaire were compared between the two groups 3 months postoperatively. Moreover, the relationships between the severity of haloes and postoperative ocular or ICL parameters were analyzed. Results At the 3-month follow-up, the efficacy indices in the full correction and under-correction groups were 0.99 ± 0.12 and 1.00 ± 0.10, respectively; the safety indices were 1.15 ± 0.16 and 1.15 ± 0.15, respectively. Total-eye spherical aberration (p < 0.0001) and internal spherical aberration (p = 0.0005) were significantly different pre- and post-operatively in the under-correction group, while no differences were found in the full correction group. Total-eye spherical aberration (p = 0.002) and the severity of haloes (p = 0.03) were postoperatively different between the two groups. The severity of haloes was associated with postoperative spherical aberration (total-eye spherical aberration: r = −0.32, p = 0.002; internal spherical aberration: r = −0.24, p = 0.02). Conclusion Good efficacy, safety, predictability, and stability were obtained early after surgery regardless of preoperative spectacle correction. Patients in the under-correction group possessed a shift to negative spherical aberration and reported greater severity of haloes at the 3-month follow-up. Haloes were the most common visual symptoms after ICL V4c implantation and the severity of them was correlated with postoperative spherical aberration.

Effect of larger corneal spherical aberration in improving the near visual acuity of eyes implanted with the TECNIS Symfony.

To explore the effect of corneal spherical aberration on the visual acuity and visual quality of eyes implanted with the TECNIS Symfony intraocular lens (IOL). A total of 43 patients with age-related cataract (60 eyes) undergoing phacoemulsification and TECNIS Symfony IOL implantation were enrolled in this study. The uncorrected distance (UDVA), intermediate (UIVA), near visual acuity (UNVA), corrected distance visual acuity (CDVA), contrast sensitivity, and ocular spherical aberration were recorded 3 months after surgery. Preoperative and postoperative corneal spherical aberration were also measured using the iTrace device. Objective scattering index (OSI), modulation transfer function cut-off frequency (MTF cut-off), and Strehl ratio (SR) were measured by the Optical Quality Analyzing System. Catquest-9SF questionnaire were applied too. Spearman's correlation analysis was used to evaluate the relationship between spherical aberration and visual quality parameters. Patients were satisfied with their postoperatively visual quality. And the postoperative logMAR UDVA, UIVA, UNVA, and CDVA was 0.05 ± 0.07, 0.04 ± 0.06, 0.15 ± 0.07, and 0.03 ± 0.05, respectively. The mean preoperative corneal spherical aberration was 0.24 ± 0.10 μm, which is the only factor influencing postoperatively UNVA, and it was negatively correlated with UNVA and glare contrast sensitivity under 18 cpd (cycle/degree, cpd) spatial frequency (r = -0.403, -0.300, -0.360; all P < 0.05). Additionally, the greater the residual spherical aberration of the cornea, the better the near vision after operation. The mean postoperative ocular spherical aberration was -0.03 ± 0.07 μm, it was not correlated with visual acuity, contrast sensitivity, and visual quality (all P > 0.05). Preoperative positive spherical aberration can benefit near vision while decrease contrast sensitivities at high spatial frequencies when implanted with the TECNIS Symfony IOL.

Clinical outcomes of the immediate reapplication of small-incision lenticule extraction without adjusting the surgical parameters after suction loss

This study was to analyze the clinical outcomes of immediate reapplication of small-incision lenticule extraction (SMILE) without adjusting the surgical parameters after suction loss and to compare the outcomes with contralateral eyes that underwent uneventful SMILE. A total of 74 patients who underwent uneventful SMILE in one eye (Uneventful group) and immediate reapplication of SMILE without adjusting the surgical parameters after suction loss in the contralateral eye (Suction loss group) were included. Suction loss occurred during the posterior lenticule surface cut in 39 eyes (53%) and the cap cut in 35 eyes (47%). Surgical outcomes, including visual acuity, manifest refraction, keratometry, and corneal wavefront aberrations, were evaluated at 6 months postoperatively. The mean uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and spherical equivalent were − 0.02 ± 0.07, − 0.04 ± 0.04, and − 0.10 ± 0.46 diopters (D), respectively, in the Suction loss group and − 0.02 ± 0.07, − 0.04 ± 0.05, and − 0.19 ± 0.53 D, respectively (P = 0.965, 0.519, and 0.265, respectively), in the Uneventful group. Changes between the preoperative and 6-month postoperative total corneal aberrations, spherical aberrations, and horizontal and vertical coma did not significantly differ between the Suction loss and Uneventful groups. Immediate reapplication of SMILE without adjusting the surgical parameters after suction loss resulted in good surgical outcomes that were comparable with those of uneventful SMILE.

Corneal Epithelium Thickness and Refractive Changes After Myopic Laser Corneal Refractive Surgery

To evaluate the postoperative changes in corneal epithelium thickness and refractive power after femtosecond laser-assisted laser in situ keratomileusis (LASIK) and small incision lenticule extraction (SMILE) for myopia correction using anterior segment optical coherence tomography (OCT) with an integrated Placido disc topographer. The VisuMax 500-kHz femtosecond laser (Carl Zeiss Meditec AG) and Amaris 750 excimer laser (SCHWIND eye-tech-solutions) were used. Central, paracentral, and 6-mm epithelial thickness values were obtained, and the change in the value of epithelial thickness was calculated. Changes in the refractive power of the epithelium were also evaluated. The repeatability of this new measurement was also analyzed using the intraclass correlation (ICC). The total follow-up period was 6 months. A total of 77 LASIK eyes were matched with 77 SMILE eyes. Mean spherical equivalent was -3.92 ± 1.67 diopters (D) for LASIK versus -4.02 ± 1.63 D for SMILE (P = .356). Epithelial thickness parameters significantly and equally thickened in both types of surgery. The change in the value of epithelial thickness was positively correlated with spherical aberration. Analysis of the refractive power of the corneal epithelial layer (ICC > 0.70) showed a tendency for the postoperative myopization of the refractive component of this layer (-0.11 D for SMILE and -0.53 D for LASIK at 3 mm) and an increase in its cylinder and aberrometry. Increasing postoperative spherical aberration and epithelial thickness increased myopization of the epithelial refractive sphere (P < .05). Corneal epithelium thickens similarly after LASIK and SMILE, being slightly higher after SMILE. This correlates with the induced spherical aberration. Corneal epithelium thickening induces myopization of its refractive power, which accounts for a slight regression of the net refractive power change on the treated cornea. [J Refract Surg. 2022;38(9):602-608.].

Clinical results of topography-guided laser-assisted in situ keratomileusis using the anterior corneal astigmatism axis and manifest refractive astigmatism axis.

To evaluate the clinical results of primary topography-guided femtosecond laser-assisted in situ keratomileusis (TG-FS-LASIK) using the Pentacam-measured anterior corneal astigmatism axis (ACA) or manifest refractive astigmatism axis (MRA). In this prospective cohort study, all eyes were treated with primary TG-FS-LASIK using the manifest cylinder. Thirty-two right eyes were treated using ACA with axis disparity > 5° in the experimental group, and 32 right eyes were treated using MRA with axis disparity ≤ 5° in the control group. Visual, refractive outcomes, and corneal higher-order aberrations were evaluated. Vector analysis of astigmatism was performed using Alpins method with the ASSORT software. The mean logMAR UDVA in the experimental group was - 0.12 ± 0.06, - 0.05 ± 0.08, and - 0.08 ± 0.08 at 1-week, 1-month, and 3-month follow-up, whereas - 0.05 ± 0.06, - 0.12 ± 0.06, and - 0.14 ± 0.06 in the control group (p = 0.017, p < 0.001, and p = 0.003). At 3-month follow-up, 79% eyes achieved a UDVA of 20/16 or better, 9% gained one line of corrected distance visual acuity, the mean manifest cylinder was - 0.375 ± 0.254 D, 84% showed a manifest cylinder within ± 0.50 D, the mean magnitude of difference vector was 0.41 ± 0.35 D, the mean absolute angle of error (AE) was 7.36 ± 6.21°, and 41% exhibited an arithmetic AE within ± 5° in the experimental group, whereas 94%, 19%, - 0.203 ± 0.148 D, 100%, 0.21 ± 0.15 D, 3.39 ± 3.68°, and 69% in the control group (all p < 0.05). The postoperative and preoperative corneal spherical aberrations were comparable in both groups (p > 0.05). Primary topography-guided FS-LASIK using Pentacam-measured anterior corneal astigmatism axis exhibited slightly inferior clinical results to that using the manifest refractive astigmatism axis. Both methods achieved comparable postoperative and preoperative corneal spherical aberrations.

Functional Optical Zone and Visual Quality After Small-Incision Lenticule Extraction for High Myopic Astigmatism.

IntroductionThe aim of this study was to compare the functional optical zone (FOZ) after correction of high myopic astigmatism and low myopic astigmatism by small-incision lenticule extraction (SMILE).MethodsIn this prospective study, 30 patients who received SMILE for high myopic astigmatism correction (cylinderical diopters ≤ − 2.0D) were enrolled in the high astigmatism group (HA). The control group comprised 40 patients who underwent SMILE for low myopic astigmatism correction (LA; cylinderical diopters ≥ − 0.5D). FOZ was delineated as the area outlined by a change of 0.5D relative to the power at the corneal vertex on the total corneal refractive power map. An ellipse-fitting program (MatLab) was used to calculate some parameters of the FOZ. Visual quality evaluations were also conducted, including evaluations of wavefront aberrations, optical quality, and intraocular scattering, and completion of a quality of life questionnaire. All of the right eyes were analyzed in the study.ResultsThe preoperative average treatment spherical equivalent (− 5.77 ± 1.86D vs. − 6.49 ± 1.49D; P = 0.074), lenticule thickness (120.87 ± 23.27 μm vs. 118.53 ± 21.66 μm; P = 0.666), and programmed optical zone (6.58 ± 0.17 mm vs. 6.65 ± 0.18 mm; P = 0.104) were comparable between the HA and LA groups. The long axes (6.99 ± 1.14 mm vs. 5.32 ± 0.61 mm; P < 0.001), short axes (4.66 ± 0.96 mm vs. 4.23 ± 0.64 mm; P = 0.047), and area (25.90 ± 8.03 mm2 vs. 17.92 ± 4.36 mm2; P < 0.001) of the FOZ were significantly larger in the HA group than in the LA group. The centration of the FOZ were comparable between the two groups (0.62 ± 0.25 mm vs. 0.70 ± 0.25 mm; P = 0.194). Postoperative spherical aberration was lower in the HA group than in the LA group (0.07 ± 0.05 μm vs. 0.14 ± 0.10 μm; P = 0.001). There was no significant difference in the ocular scatter index (0.80 ± 0.46 vs. 0.73 ± 0.46; P = 0.447), modulated transfer function (MTF)cutoff (37.89 ± 9.79 cpd vs. 39.78 ± 7.45 cpd; P = 0.363), and Strehl in two dimensions (Strehl2D) ratio (0.20 ± 0.04 vs. 0.20 ± 0.04; P = 0.363) between the HA group and the LA group. There were no significant differences in the scores on quality of life between the HA and LA groups (45.88 ± 2.15 vs. 45.64 ± 1.84; P = 0.423). Correlation analysis revealed that increase in the spherical aberration was significantly correlated with the long axes, short axes and area in the FOZ in both groups.ConclusionWith a comparable optical design and attempted correction in SMILE, the eyes with higher myopic astigmatism correction achieved larger FOZ than the eyes with lower myopic astigmatism correction. Consequently, less spherical aberration induction was created after higher myopic astigmatism correction. This result may be associated with less corneal volume sculpted by laser for the higher astigmatism treatment, leading to fewer biochemical responses and les change in corneal aspherity. Good retinal image quality and satisfied quality of life were achieved at a comparable level in both study groups.

Clinical Analysis of Central Islands after Small Incision Lenticule Extraction (SMILE)

ABSTRACT Purpose To evaluate the incidence of central islands after 6-month follow-up of Small Incision Lenticule Extraction (SMILE) and to assess their role in safety and accuracy. Methods Analysis of the preoperative and postoperative corneal tomography, best spectacle refraction and corrected distance visual acuity of 82 subjects that underwent SMILE. Incidence of central islands was assessed through total corneal spherical aberration (SA) over 4 mm of central diameter and the SA was compared between two groups with and without safety loss (CDVA difference ≥0.1 logMAR from preoperative). The cut-off value for detecting the risk of postoperative central island development was calculated. The influence in accuracy was calculated through magnitude of error of the spherical equivalent and astigmatism, both for spectacle refraction at corneal plane (SE-Rx and AST-Rx) and for total corneal refractive power at 3 mm (SE-TCRP3 and AST-TCRP3). Results Five from 82 eyes resulted in a loss of safety, obtaining significant differences in SA, both preoperatively (p = .01) and postoperatively (p = .007) after stratification by safety loss. A preoperatively cut-off value ≤0.012 μm of SA predicted the appearance of central islands with sensitivity of 100% and specificity of 75%. Despite postoperative SA being related to the preoperative spherical equivalent, for both SE-Rx and SE-TCRP3, this tendency disappeared after readjusting results according to a nomogram. Conclusions Central islands in SMILE, despite being a rare adverse event, can affect the safety of the procedure and are related to preoperative central steepness, not corrected by the spherical lenticule, which is clearly visible postoperatively.

Small incision lenticule extraction versus photorefractive keratectomy: A comparative study

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

The Effect of Cone Localization on Higher Order Aberrations After Corneal Crosslinking for Keratoconus.

Objectives:This study was designed to evaluate the effects of corneal collagen cross-linking (CXL) on topographic parameters, visual acuity, and corneal high-order aberrations according to the preoperative cone location in keratoconus.Methods:This retrospective study assessed patients with keratoconus who underwent CXL between March 2016 and February 2019. Patients with a history of corneal surgery, corneal hydrops, corneal scar tissue, delayed epithelial healing, and a corneal thickness of <400 μm were excluded. The included eyes were divided into 2 groups according to the preoperative cone location: maximum K in the central 3-mm optical zone (group 1) or the central 3-mm to 5-mm optical zone (group 2). The preoperative and postoperative 24-month, best-corrected visual acuity (BCVA), intraocular pressure, K max, symmetry index front, corneal thickness, and high order aberration findings were recorded.Results:The study included 67 eyes of 67 patients with keratoconus: 39 in group 1, and 28 in group 2. There were statistically significant differences between the groups in the preoperative BCVA values (p=0.04). There was no significant difference between the preoperative and postoperative mean K max between the 2 groups (p=0.08). The mean difference in corneal thickness between preoperative and postoperative measurements was significantly lower in group 2 than in group 1 (p=0.03). The preoperative and postoperative mean spherical aberration was significantly higher in group 1 than in group 2 (p=0.001 and p=0.005, respectively).Conclusion:The preoperative cone location in keratoconus may affect CXL outcomes. At the end of the second year, CXL was found to have a similar efficacy on visual acuity and keratometry parameters in the central and paracentral cone groups, and the recovery in terms of a spherical aberration among high-order aberrations after CXL in the central cone group was better than that of the paracentral cone group.

Laser-assisted in situ keratomileusis long term outcomes in late adolescence.

Evaluate the long term outcomes of myopic-LASIK in a late adolescent population (age ⩾17 and <20 at the time of surgery). Monocentric retrospective case series study. Eyes with at least 3 years of follow-up time were included. Primary outcome measures were long term efficacy, safety and stability of the refractive error. Secondary outcome measure was the evaluation of the relation between the postoperative spherical aberration and the long term stability of the refractive error. Forty-seven eyes of 25 patients were included. Mean follow-up was 9.23 ± 3.16 years. Mean age at the time of surgery was 18.74 ± 0.44 years. With time, postoperative UDVA showed a mild but significant deterioration of 1-2 Snellen lines (p = 0.012), in connection with a mild but significant myopization of the SE (mean increase of -0.43 D; p < 0.001), sphere (mean increase of -0.29 D; p = 0.004) and cylinder (mean increase of -0.16 D; p = 0.013). CDVA remained stable over time (p > 0.05). Efficacy index decreased from 1.01 to 0.87 in the long term (77% UDVA ⩾ 20/32). Safety remained at 1.06. 66% and 74% of eyes presented a SE within ±0.50 D and ±1.00 D respectively. SE changed over 0.50D in 33% of eyes. No correlation could be detected between the SE and the postoperative spherical aberration. No cases of corneal ectasia were detected. Myopic-LASIK in late adolescence is safe and effective, but a mild myopic progression occurs. Despite presence of refractive stability is preferable, if necessary, myopic LASIK provides relatively good outcomes in the long term in this young population.

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

PurposeTo examine the biomechanical effects-induced wave-front aberrations after conventional laser refractive surgery.MethodsA 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.ResultsFollowing 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.ConclusionsAmong 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.

Comparison of corneal epithelial remodeling after small incision lenticule extraction and femtosecond laser-assisted LASIK

Objective: To investigate the corneal epithelial thickness changes between small incision lenticule extraction (SMILE) and femtosecond laser-assisted LASIK (FS-LASIK), study the related factors and analyze the relationship between the changes in corneal epithelial thickness and corneal aberration. Methods: This case control study included 59 patients (118 eyes), 27 males and 32 females, aged 25.64±5.57 years, who were scheduled for SMILE or FS-LASIK for treatment of myopia with or without myopic astigmatism at the First Affiliated Hospital of Soochow University between October 2016 and May 2017. All patients were divided into two groups according to the surgery. Epithelial thickness was obtained in nine zones with Fourier-domain optical coherence tomography across a 5-mm diameter centered by the pupil before surgery and at 1 week, 1 month, 3 months and 6 months postoperatively. The observed changes were analyzed by linear-regression analysis with the central corneal thickness decrement, ablation rate and corneal aberration. Comparison between two groups was analyzed by independent sample t-test, analysis of variance and Mann-Whitney U test. Results: There was no significant difference in corneal epithelial thickness of nine zones between SMILE and FS-LASIK for low to moderate myopia (manifest refraction sphere equivalent<-6.00 diopters) and high myopia (manifest refraction sphere equivalent ≥-6.00 to -10.00 diopters), respectively, before surgery (P>0.05). At 1 month, no significant difference existed in corneal epithelial thickness increment in nine zones between FS-LASIK and SMILE for low to moderate myopia (P>0.05), but a larger increase was observed in the superior (t=2.670, P=0.010), superonasal (t=2.506, P=0.015) and nasal (t=2.831, P=0.007) zones following FS-LASIK [(4.2±3.2), (3.4±2.7) and (3.7±2.5) μm] than SMILE [(2.2±2.2), (1.6±2.5) and (1.7±2.6) μm] for high myopia. At 3 months, a larger increase in corneal epithelial thickness was observed in the superior (t=2.703, P=0.009) zone following FS-LASIK than SMILE for low to moderate myopia, and the same increase was observed in the central (t=2.660, P=0.010), superior (t=3.229, P=0.002), nasal (t=2.420, P=0.019), inferonasal (t=2.651, P=0.011), inferotemporal (t=2.153, P=0.036) and superotemporal (t=2.281, P=0.027) zones after FS-LASIK [(6.7±2.6), (5.0±2.1), (3.9±1.9), (4.8±1.8), (7.5±2.5) and (6.4±2.7) μm] than SMILE [(4.7±2.9), (2.9±2.5), (2.4±2.4), (3.3±2.2), (6.0±2.4) and (4.8±2.4) μm] for high myopia. At 6 months, a larger increase in corneal epithelial thickness was observed in the superior (t=3.340, P=0.001) and nasal (t=1.952, P=0.055) zones following FS-LASIK than SMILE for low to moderate myopia, and the same increase was observed in the superior (t=2.332, P=0.024) and inferonasal (t=2.172, P=0.034) zones after FS-LASIK than SMILEfor high myopia. The central corneal thickness decrement after SMILE was much more than FS-LASIK both in the low to moderate myopia and high myopia groups (P<0.05). The average corneal epithelial thickness increment correlated positively with the central corneal thickness decrement and ablation rate at 1 month, 3 months and 6 months postoperatively (P<0.01). For SMILE, the total higher orders aberration (0.81±0.26, 0.79±0.28 and 0.81±0.31) and spherical aberration (0.50±0.21, 0.48±0.20 and 0.52±0.23) were less than FS-LASIK (0.97±0.34, 0.97±0.33 and 0.93±0.32; 0.72±0.25, 0.66±0.30 and 0.71±0.25) at 1 month, 3 months and 6 months postoperatively (P<0.05). Furthermore, the corneal aberration increment correlated positively with the average corneal epithelial thickness increment (P<0.05). Conclusions: The corneal epithelial thickness increment after SMILE was less than FS-LASIK. SMILE had better uniformity of the corneal epithelial thickness increment at the observed zones, which may explain the finding that the postoperative spherical aberration of SMILE was less than FS-LASIK. (Chin J Ophthalmol, 2020, 56:93-102).

Supracor LASIK treatment of hyperopic and myopic presbyopes: a comparative study

Background Supracor is a relatively new technique that has been approved for hyperopic presbyopia correction; however, till now, no published studies have evaluated the performance of supracor in myopic patients with presbyopia. Objective The aim of this study was to compare the results of supracor treatment of presbyopia between hyperopic and myopic patients. Patients and methods The study included two groups: hyperopic group and myopic group. Complete preoperative examination consisted of cycloplegic and manifest refraction, spherical equivalent (SE), binocular uncorrected and corrected distant visual acuity (UCDVA and CDVA), binocular uncorrected and corrected near visual acuity (UCNVA and CNVA), measurement of higher order aberrations, and the determination of the dominant eye using hole-in-the card test. Patients were examined at the first day, third day, 1 month, 3 months, and 6 months postoperatively. UCDVA, CDVA, UCNVA, CNVA, higher order aberrations, and SE were measured, and all complications were recorded. Furthermore, patient’s satisfaction was documented by a detailed questionnaire. All data were collected, analyzed, and compared between the two groups. Results The study included 20 hyperopic and 19 myopic patients. There were no statistically significant differences (P>0.05) between the two groups regarding postoperative UCDVA, CDVA, UCNVA, CNVA, SE, spherical aberrations, and complications. However, there was a statistically significant difference (P<0.05) between the studied groups regarding patient satisfaction at 1 month, 3 months, and 6 months postoperatively (which was higher in patients with hyperopia), with a significant increase in patient satisfaction in those with hyperopia over time. Conclusion Supracor was found to be effective, predictable, and stable technique in the management of presbyopia in both patients with myopia and those with hyperopia, with similar results in the two groups except for patient satisfaction, which was higher in those with hyperopia.

Pupillodynamics and corneal spherical aberrations in a set of Indian cataract patients and its implications for aberrometric customisation of intraocular lenses.

Purpose:Assessment of pupil diameter in various light conditions and the corresponding corneal spherical aberrations in a cohort of Indian eyes with bilateral senile cataracts and the possible use of this data in aberrometric customization of intraocular lenses (IOLs).Methods:In this prospective observational study done at a tertiary eye care centre in India, the selected patients were subjected to measurement of their pupil diameters in scotopic, mesopic, and photopic conditions as well as the corresponding corneal spherical aberrations, using the Sirius Topographer (Costruzione Strumenti Oftalmici, Florence, Italy). Shapiro–Wilk test, Independent t-test, ANOVA with Bonferroni correction on post-hoc testing were used for statistical analysis.Results:104 eyes of 52 patients were enrolled for the study. The mean age was 53 ± 11.88 years. The mean scotopic, mesopic, and photopic pupil sizes were 4.37 mm (4.11–4.63 mm), 3.92 mm (3.71 mm–4.15 mm), and 3.37 mm (3.18–3.67 mm), respectively. There was a statistically significant difference (P = <0.001) in the mean corneal spherical aberration measured at the 6 mm zone (0.23 ± 0.02 microns) and at the 4 mm zone (0.06 ± 0.01 microns).Conclusion:The mean corneal spherical aberration corresponding to the average mesopic pupil size of our patient population was substantially lower than that of the scotopic pupil size and also less than the amount corrected by most of the negative aspheric IOLs. This perhaps indicates the need for customising IOLs based on the spherical aberrations of cornea at the zone corresponding to the mesopic pupil diameter for optimal residual total postoperative spherical aberrations.