Femtosecond LASIK Research Articles

Comparison of planned versus achieved central corneal stromal thickness reduction in SMILE versus FS-LASIK: a retrospective study

Accuracy of planned corneal stromal thickness (CST) reduction is essential to the safety of laser vision correction. This study was to compare the accuracy of the planned central CST reduction in small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK). A total of 77 patients (43 for SMILE, 34 for FS-LASIK using Custom-Q algorithm) were included in this retrospective study. At postoperative 6–18 months, the central CST reduction was overestimated by 18.49 ± 6.42 μm in the SMILE group (P < 0.001) and underestimated by 2.56 ± 7.79 μm in the FS-LASIK group (P = 0.064). The planned-achieved difference (PAD) of central CST reduction was positively correlated with preoperative manifest refraction spherical equivalent (MRSE) and with planned central CST reduction in both groups. When calculated by manifest refraction (MR) without nomogram adjustment, the central CST reduction was overestimated by 11.14 ± 6.53 μm in the SMILE group and underestimated by 2.83 ± 7.39 μm in the FS-LASIK group. The PAD of central CST reduction without nomogram was significantly narrowed in SMILE and maintained in FS-LASIK, suggesting estimation using MR without nomogram adjustment may be feasible for SMILE and FS-LASIK in clinical practice.

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

BackgroundThis 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.MethodsWe 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.ResultsOur 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).ConclusionA 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.

Binocular imbalance in patients after implantable collamer lens V4c implantation or femtosecond laser-assisted in situ keratomileusis for myopia with presbyopia.

To investigate the long-term safety, efficacy, and binocular balance of monovision surgery using Implantable Collamer Lens (ICL) V4c implantation and Femtosecond Laser-Assisted in situ Keratomileusis (FS-LASIK) for the treatment of myopic patients with presbyopia. This case series study involved 90 eyes of 45 patients (male/female = 19/26; average age:46.27 ± 5.54 years; average follow-up time:48.73 ± 14.65 months) who underwent the aforementioned surgery to treat myopic presbyopes. Data on manifest refraction, corrected distance visual acuity, dominant eye, presbyopic addition, intraocular pressure, and anterior segment biometric parameters were collected. The visual outcomes and binocular balance at 0.4 m, 0.8 m, and 5 m were documented. The safety index for the ICL V4c and FS-LASIK groups were 1.24 ± 0.27 and 1.04 ± 0.20 (p = 0.125), respectively. Binocular visual acuity (logmar) for 0.4 m, 0.8 m, and 5 m were -0.03 ± 0.05, -0.03 ± 0.02, and 0.10 ± 0.03 for the ICL V4c group, and -0.02 ± 0.09, -0.01 ± 0.02, and 0.06 ± 0.04 for the FS-LASIK group, respectively. The proportions of all patients with imbalanced vision at 0.4 m, 0.8 m, and 5 m distances were 68.89, 71.11, and 82.22%, respectively (all p > 0.05 between the two groups). There were significant differences in refraction between the balanced and imbalanced vision for patients at 0.4 m distance (for non-dominant eye spherical equivalent [SE]: -1.14 ± 0.17D and -1.47 ± 0.13D, p < 0.001), 0.8 m distance (for preoperative ADD:0.90 ± 0.17D and 1.05 ± 0.11D, p = 0.041), and 5 m distance (for non-dominant SE: -1.13 ± 0.33D and -1.42 ± 0.11D, p < 0.001). ICL V4c implantation and FS-LASIK monovision treatment demonstrated good long-term safety and binocular visual acuity at various distances. After the procedure, the imbalanced patients' vision is primarily related to the age-related presbyopia and anisometropia progression caused by the monovision design.

Comparison of Visual Outcomes and Higher-order Aberrations Between FS-LASIK and SMI-LIKE for Moderate to High Hyperopia: A 2-year Result.

The aim of the study was to evaluate and compare the long-term visual outcomes and higher-order aberrations (HOAs) between femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and small-incision lenticule intrastromal keratoplasty (SMI-LIKE) in the correction of moderate to high hyperopia. In this study, 16 subjects (20 eyes) underwent FS-LASIK and 7 subjects (10 eyes) underwent SMI-LIKE. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, mean keratometry (Km), anterior asphericity (Q), and HOAs preoperatively and 2 years postoperatively were obtained in both procedures. The efficacy indices of the FS-LASIK group and the SMI-LIKE group were 0.85 ± 0.14 and 0.87 ± 0.17, respectively. The safety indices of the FS-LASIK and SMI-LIKE groups were 0.99 ± 0.15 and 1.08 ± 0.24, respectively. No significant difference in safety index or efficacy index was found between the FS-LASIK and SMI-LIKE groups (all P > 0.05). The correlation coefficient of the attempted versus achieved spherical equivalent postoperatively was 0.69 (P < 0.01) and 0.89 (P < 0.01) in the FS-LASIK group and SMI-LIKE groups, respectively. The front Km, negative Q value, negative spherical aberrations (SAs), coma, and total HOAs significantly increased postoperatively in the 2 groups (P < 0.05). The FS-LASIK group had greater changes in Q value and SA postoperatively than the SMI-LIKE group (P < 0.01). SMI-LIKE had similar safety and efficacy to FS-LASIK in the correction of moderate to high hyperopia. However, SMI-LIKE may equip better visual quality postoperatively for its lower Q value and SA changes than FS-LASIK.

Combination therapy with 3% diquafosol tetrasodium ophthalmic solution and sodium hyaluronate: an effective therapy for patients with dry eye after femtosecond laser-assisted in situ keratomileusis.

To assess the effect of combination therapy with 3% diquafosol tetrasodium (DQS) and sodium hyaluronate (HA) for dry eye after femtosecond laser-assisted in situ keratomileusis (FS-LASIK). Prospective nonrandomized comparative trial. The prospective study included 80 eyes of 40 patients who underwent FS-LASIK with or without preoperative dry eye. Patients were divided into a combination group and a HA group according to their willingness and the doctor's advice. The combination group was treated with DQS six times a day and HA four times a day, and the HA group was treated with HA four times a day after FS-LASIK. Ocular surface disease index (OSDI), ocular symptom score, vision-related score, environmental score, tear meniscus height (TMH), first non-invasive tear breakup time (NIBUT-First), average non-invasive tear breakup time (NIBUT-Ave), tear breakup time (TBUT), Schirmer I test (SIT), corneal fluorescein staining score (CFS), bulbar redness score, limbal redness score, lipid layer grade (LLG), meiboscore, lid margin abnormality, corneal sensitivity, and corneal nerve parameters were examined before surgery and at 1 week and 1 month after surgery. Surface regularity index (SRI) was also examined before surgery and at 1 month postoperatively. OSDI score (p = 0.024) and vision-related score (p = 0.026) were significantly lower in the combination group than in the HA group at 1 month after FS-LASIK, especially in patients with preoperative dry eye symptoms. The increasements of CFS (p = 0.018), bulbar redness score (p = 0.021), and limbal redness score (p = 0.009) were significantly lower in the combination group than in the HA group at 1 week after FS-LASIK. But other ocular surface parameters showed no difference between both groups at 1 week and 1 month after FS-LASIK. LLG was significantly higher in the combination group than in the HA group at 1 week (p = 0.004) and 1 month (p < 0.001) after surgery, especially in patients with high meiboscore. Additional DQS significantly improved corneal sensitivity in patients without preoperative dry eye symptoms at 1 month after FS-LASIK (p = 0.041). The combination therapy with DQS and HA significantly relieved subjective symptoms, improved ocular surface status, and had the potential to promote corneal nerve growth in patients after FS-LASIK.

Role of tear vasoactive intestinal peptide on dry eyes after laser keratorefractive surgery

BackgroundTo explore the changes in vasoactive intestinal peptide (VIP) concentration in tears post laser-assisted sub-epithelial keratomileusis (LASEK) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK) surgeries and related factors, possible association between postoperative dry eye symptoms and VIP concentration in tears, and factors influencing dry eye symptoms after different periods post LASEK and FS-LASIK surgeries.MethodsIn this prospective, non-randomized, longitudinal cohort study, 23 and 22 subjects were recruited and underwent LASEK and FS-LASIK, respectively. After conducting an intact ophthalmic examination and collecting relevant surgical data, all subjects were examined for VIP concentration in their tears using ELISAs, tear-film breakup time, ocular staining and ocular surface disease index questionnaire before surgery and 1 day, 1 week, and 1 month post-surgery.ResultsTear VIP concentration increased significantly after both LASEK and FS-LASIK, with the highest concentration observed 1 week post-surgery (P ≤ 0.05). Tear VIP concentration correlated negatively with corneal ablation depth (AD). The extent of dry eyes was related to the operation method employed and postoperative recovery period. In FS-LASIK and LASEK subjects, dry eyes were mainly affected by the basic ocular surface status before surgery, and VIP concentration. Furthermore, in LASEK subjects, dry eyes were negatively correlated with AD.ConclusionVIP was stimulated and mobilized as an emergency protection post-refractive surgery and a trauma model affected by AD. It can indirectly indicate the inevitable relationship between postoperative dry eye and nerve injury. Elevated post-surgery tear VIP relieves dry eye symptoms, showing its neuroimmune role in regulating adverse injury stimulation. The present study provides a solution to the pathogenesis of postoperative dry eyes.Trial registrationThe trial registration number: 2021JS22. Date of registration: 10 May 2021.

Posterior corneal surface and anterior chamber changes after Small incision lenticule extraction and Femtosecond laser‐assisted laser in‐situ keratomileusis

AbstractWe aimed to evaluate the posterior corneal and anterior chamber changes following small incision lenticule extraction (SMILE) and femtosecond laser‐assisted laser in situ keratomileusis (FS‐LASIK). This retrospective study included 93 eyes for SMILE and 228 eyes for FS‐LASIK. Posterior corneal curvature, anterior chamber biometrics, and posterior corneal aberrations preoperatively and at 1 week and 3 months after surgery were evaluated. The correlation between surgical‐related factors and posterior corneal morphology changes, posterior corneal morphology changes, and posterior corneal aberration alterations were determined. There was an increase in mean posterior corneal radius (PCC R) and flat posterior corneal radius (PCC R1) and decrease in anterior chamber depth and anterior chamber volume in the SMILE and FS‐LASIK group (all p &lt; 0.05). A significant difference was observed in posterior corneal higher‐order aberrations before and after the FS‐LASIK (p = 0.006). A negative correlation was found between alterations of PCC R and changes of posterior corneal spherical aberrations in the SMILE (r = −0.289) and FS‐LASIK group (r = −0.383). In conclusion, posterior corneal and anterior chamber biometrics are changed after SMILE and FS‐LASIK. Innovatively, we find that changes in posterior corneal morphology are correlated with posterior corneal aberration alterations.

Corneal Biomechanics After SMILE, Femtosecond-Assisted LASIK, and Photorefractive Keratectomy: A Matched Comparison Study.

To evaluate the change in corneal stiffness after small incision lenticule extraction (SMILE), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), and photorefractive keratectomy (PRK). Age, gender, spherical equivalent, and central corneal thickness (CCT)-matched cases undergoing SMILE with a 120-µ cap, FS-LASIK with a 110-µ flap, and PRK were enrolled. One-year change in the stress-strain index, stiffness parameter at first applanation, integrated inverse radius, deformation amplitude ratio at 2mm, and deformation amplitude ratio at 1mm were compared between the surgical groups by linear mixed-effect models. Within each surgical group, 120 eyes completed 1year of follow-up. The residual stromal bed (RSB) thickness and (RSB/CCTpostop) were 348.1 ± 35.0 (0.74), 375.4 ± 31.0 (0.77) and 426.7 ± 2 µm (0.88) after SMILE, FS-LASIK, and PRK, respectively. The 1-year change in all biomechanical indices was significant, except the stress-strain index with PRK (P = 0.884). The change in all indices with SMILE were significantly greater than with FS-LASIK and with PRK (all P < 0.01), except the deformation amplitude ratio at 1mm change between SMILE and FS-LASIK (P = 0.075). The changes in all indices with FS-LASIK were significantly greater than with PRK (all P < 0.05). Although SMILE preserves the greatest amount of anterior cornea with a cap thickness of 120 µ, this also produces the smallest RSB and the greatest decrease in stiffness. Thus, the RSB is shown to be the predominant determinant of stiffness decreases, rather than the preserved anterior cornea. We recommend using a thinner cap to achieve a thicker RSB and a lesser decrease in the corneal stiffness in the SMILE procedure. After refractive surgery, RSB is predominant determinant of stiffness decreases, rather than the preserved anterior cornea.

The impact of different corneal refractive surgeries on binocular dynamic visual acuity.

To investigate the influence of different corneal refractive surgeries on dynamic visual acuity (DVA), and explore its potential influence factors. This was a prospective non-randomized study. Adult myopic patients undergoing bilateral laser-assisted sub-epithelial keratomileusis (LASEK), femtosecond laser-assisted in situ keratomileusis (FS-LASIK), or small incision lenticule extraction (SMILE) with Plano refraction target were enrolled. Uncorrected and corrected distance visual acuity (UDVA/CDVA), manifest refraction and binocular optotype-moving DVA of 40 and 80 degrees per second (dps) were evaluated pre-operatively and post-operatively up to 3 months. The study included 264 eyes of 132 subjects, with an average age of 27.0 ± 6.7 years, and females accounted for 59% of the participants. Significant improvement was observed at the 3-month visit for 40 dps (SMILE, P = 0.001; LASEK, P = 0.006; FS-LASIK, P = 0.010) and 80 dps (SMILE, P = 0.011; LASEK, P = 0.025; FS-LASIK, P = 0.012) DVA. Adjusting for pre-operative DVA, there was no significant difference in DVA among groups at 3 months post-operatively (P > 0.05 for multiple comparisons). Overall, multiple linear models demonstrated that post-operative DVA at 3 months was correlated with pre-operative DVA (40 dps, β = 0.349, P = 0.001; 80 dps, β = 0.447, P < 0.001), pre-operative spherical equivalent (40 dps, β = 0.311, P = 0.003; 80 dps, β = 0.261, P = 0.009) and post-operative UDVA (40 dps, β = -0.224, P = 0.024; 80 dps, β = -0.188, P = 0.05). Dynamic visual acuity at 3 months post-operatively of the three corneal refractive surgeries was better than that before the surgery in adult myopic patients, and there was no significant difference among different surgical techniques. Post-operative DVA at 3 months was found correlated with pre-operative DVA, pre-operative SE, and post-operative UDVA. With further improvement, DVA could be a promising functional visual indicator for myopic patients undergoing refractive surgeries.

Corneal Epithelial Remodeling in a 6-Month Follow-up Period in Myopic Corneal Refractive Surgeries

To investigate corneal epithelial thickness changes during a 6-month follow-up period after transepithelial photorefractive keratectomy (tPRK), femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK), and small incision lenticule extraction (SMILE). This prospective study included 76 eyes of 76 participants who underwent myopic refractive surgery (23 FS-LASIK, 22 SMILE, and 31 tPRK). Epithelial thickness and anterior curvature were averaged over 4 regions (subdivided into 25 areas) and measured by spectral-domain optical coherence tomography and Scheimpflug tomography before the operation (pre) and at 1 or 3 days (pos1-3d), 1 week (pos1w), and 1 month (pos1m), 3 months (pos3m), and 6 months (pos6m) postoperatively. The epithelial thickness of the three groups was similar in both the pre and pos6m (all P > .05), but the tPRK group fluctuated the most during the follow-up period. The largest increase was in the inferior-temporal paracentral area (7.25 ± 2.58 μm for FS-LASIK; 5.79 ± 2.41 μm for SMILE; 4.88 ± 5.84 μm for tPRK; all P < .001). Only the epithelial thickness of tPRK increased from pos3m to pos6m (P < .05), whereas all changes for FS-LASIK and SMILE were not significant (P > .05). A positive correlation of thickness changes with curvature gradient in the paracentral region of tPRK was found (r = 0.549, P = .018), but not in other regions in all groups. Epithelial remodeling followed different trends after different surgeries from the early postoperative stage onward, but exhibited similar values at pos6m. Although remodeling after FS-LASIK and SMILE stabilized by pos3m, it remained unstable at pos6m after tPRK. These changes may affect corneal profile and lead to deviation from the intended surgical outcome. [J Refract Surg. 2023;39(3):187-196.].

Anterior segment inflammation and its association with dry eye parameters following myopic SMILE and FS-LASIK

Purpose To evaluate dry eye and anterior segment inflammation after small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (FS-LASIK), and investigate their association. Methods This prospective and observational study included 96 eyes from 48 myopic patients. The evaluation was performed at baseline, postoperative day 1, week 1, month 1 and month 3. Outcome measures included anterior chamber flare, bulbar redness (BR), limbal redness (LR), ocular surface disease index (OSDI), tear meniscus height (TMH), the first and average noninvasive breakup time (NIBUT-1, NIBUT-a), fluorescein breakup time (FBUT), corneal fluorescein staining (CFS), and Schirmer I. Generalized estimating equations (GEEs) were applied to explore the correlation between flare and ocular surface parameters. Results Flare increased significantly in both groups at day 1 and week 1 and then returned to baseline at month 1. In both groups, BR decreased on day 1 and then gradually increased towards the baseline. In FS-LASIK, LR was lower than baseline at day 1 and month 3. An increase in OSDI was found in the SMILE group on day 1, and in the FS-LASIK group at day 1 to month 1. NIBUT-1 and NIBUT-a decreased significantly on day 1 in both groups. At month 3, NIBUT-a did not return to baseline in FS-LASIK. CFS increased significantly at week 1 in both groups. All parameters were comparable between SMILE and FS-LASIK except for OSDI and NIBUT-a. Time and spherical equivalent showed a correlation with flare. Conclusions Both SMILE and FS-LASIK induced elevated anterior chamber flare and dry eye. However, flare might not be considered a factor determining perioperative dry eye. Key Messages Dry eye disease is common after corneal refractive surgery. Signs and symptoms of dry eye disease persist longer after FS-LASIK compared with SMILE. Both FS-LASIK and SMILE transiently disrupted blood-aqueous barrier integrity, leading to anterior segment inflammation. Anterior chamber flare might not be considered a factor explaining perioperative dry eye, other biomarkers remain for future exploration.

Small incision lenticule extraction and femtosecond-assisted laser in situ keratomileusis in patients with deep corneal opacity: case series.

To report the safety, efficacy, and accuracy of small-incision lenticule extraction (SMILE) or femtosecond-assisted laser in situ keratomileusis (FS-LASIK) for the correction of myopia or myopic astigmatism in patients with deep corneal opacity denoted by anterior segment optical coherence tomography (AS-OCT). Four patients with monocular corneal opacity (3 due to mechanical injury, 1 due to a firecracker wound) were recruited and treated with refractive surgery (3 for SMILE, 1 for FS-LASIK combined with limbal relaxing incision (LRI). Preoperative ocular manifestations, surgical details, postoperative visual outcomes, corneal opacity parameters, and corneal topography were analyzed. Preoperatively, spherical diopter ranged from -3.0 D to -4.75 D with cylinder ranging from -0.75 to -5.0 D, and corrected distance visual acuity (CDVA) ranging from 20/25 to 20/20. One eye's corneal opacity was located in the central zone and three were in the mid-peripheral optical zone. Three patients underwent uneventful SMILE in both eyes, whilst one patient underwent FS-LASIK for high astigmatism in both eyes and LRI in the right eye. CDVA of the eye with corneal opacity ranged from 20/22 to 20/20 one to six weeks postoperatively. Two patients achieved better CDVA and no patients lost Snellen lines. The postoperative diopter was within ±0.75 D for all eyes. Significant edema existed above the corneal opacity in one eye and dissipated soon. No eccentric corneal topography or morphological anomaly of the corneal cap or flap was observed. The cases demonstrate that SMILE or FS-LASIK is safe and effective to treat myopic astigmatism combined with deep corneal opacity lesions after comprehensive preoperative evaluation and appropriate candidate selection. FS-LASIK combined with LRI is also sufficient for correcting high astigmatism due to corneal scarring.

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

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

Safety and Precision of Two Different Flap-morphologies Created During Low Energy Femtosecond Laser-assisted LASIK.

Currently, two major principles exist to create LASIK flaps: firstly, a strictly horizontal (2D) cut similar to the microkeratome-cut and secondly an angled cut with a "step-like" edge (3D). The strictly horizontal (2D) cut method can be performed using apparatus such as the low-energy FEMTO LDV Z8 laser and its predecessors which are specific to this type. Alternatively, the low-energy FEMTO LDV Z8 laser's 3D flap design creates an interlocking flap-interface surface which potentially contributes toward flap stability. In addition, the FEMTO LDV Z8 offers flap-position adjustments after docking (before flap-creation). The current study analyzed precision, safety, efficacy, as well as patient self-reported pain and comfort levels after applying two different types of LASIK flap morphologies which were created with a low-energy, high-frequency femtosecond (fs) laser device. A prospective, interventional, randomized, contralateral eye, single-center comparison study was conducted from November 2019 to March 2020 at the Hamburg vision clinic/ zentrumsehstärke, Hamburg, Germany. Eleven patients and 22 eyes received low-energy fs LASIK treatment for myopia or myopic astigmatism in both eyes. Before the treatment, the eyes were randomized (one eye was treated with the 2D, the other eye with the 3D method). The mean central flap thickness one month after surgery was 110.7 1.6 μm (2D) and 111.2 1.7 μm (3D); P = 0.365 (2D vs 3D). Flap thickness measured at 13 different points resulted in no statistically significant differences between any of the measurement points within/between both groups; demonstrating good planarity of the flap was achieved using both methods. Despite not being statistically significant, the surgeons recognized an increase in the presence of an opaque bubble layer in the 3D flap eyes during surgery and some patients reported higher, yet not statistically significant, pain scores in the 3D flap eyes during the first hours after the treatment. Overall, safety- and efficacy indices were 1.03 and 1.03, respectively. In this prospective, randomized, contralateral eye study, the low-energy fs laser yielded predictable lamellar flap thicknesses and geometry at one-month follow-up. Based on these results, efficacy and safety of the corresponding laser application, that is, 2D vs 3D, are equivalent.

Comparative study of Refractive and Visual Quality after Wavefront-Optimized FS-LASIK for Angle Kappa Adjustment in Dominant and Nondominant Eyes.

This study investigates the differences between dominant and nondominant eyes in FS-LASIK with 50% angle kappa compensation on diopter and visual quality. Setting: University hospital. Design: retrospective clinical study. Methods: A total of 109 patients (218 eyes,100%) with myopia who underwent femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) were randomly selected. The preoperative pupil size，center position and offset between the coaxially sighted corneal light reflex (P-Dist) of the patients was recorded. In preoperative and postoperative 6 months, an iTrace wavefront aberrometer (Tracey Technologies, Inc.) was used to measure the corneal, internal optics, and total aberrations. Results: The 6 months postoperatively for corneal coma of the dominant eyes were 0.141±0.055 μm and the nondominant eyes were 0.157 ±0.033 μm, which was significantly greater than the dominant eyes (P = 0.028). The postoperative corneal coma aberration changes were positively correlated with preoperative P-Dist, the dominant eyes (r = 0.221, P = 0.023), and the nondominant eyes (r = 0.251, P = 0.009). Conclusions: We suggest adjusting the angle kappa percentage in the nondominant eyes to be higher than that of the dominant eyes in individualized corneal refractive surgery to find the ablation center closest to the visual axis.

Transient change in the binocular visual function after femtosecond laser-assisted in situ keratomileusis for myopia patients.

The goal of this study was to compare the difference in binocular visual function for high and low-moderate myopes before and after femtosecond laser-assisted in situ keratomileusis (FS-LASIK). Thirty-three subjects (17 males and 16 females) were divided into two groups according to their preoperative refractive errors in spherical equivalent (SE): low-moderate myopia group (SE ≥-6.00 D) and high myopia group (SE <-6.00 D). The binocular visual function including accommodative amplitude (AA), accommodative facility (AF), positive and negative relative accommodation (PRA and NRA, respectively), horizontal phoria measurement, positive and negative fusion vergence, accommodative-convergence over accommodation (AC/A) ratio, and stereopsis were assessed with the best-corrected vision before patients received FS-LASIK and 7 and 30 days after the surgery. Repeated measures analysis of variance (ANOVA) was applied to study the change in binocular visual function. The AF values in both groups were significantly reduced after 7 days of FS-LASIK (baseline vs. day 7 (mean): high myopia group: 7.85 vs. 5.62 cpm, repeated ANOVA, P = 0.01; low-moderate myopia group: 5.95 vs. 4.40 cpm, repeated ANOVA, P = 0.04). This change returned to the baseline level 30 days after the operation. In addition, the horizontal phoria values in both groups were significantly reduced for both distant (P = 0.019 and P = 0.001, respectively) and near (P = 0.003 and P = 0.049, respectively) 7 days after the operation, but they rebound to preoperative state after 30 days. A transient change in binocular visual function was noticed after 7 days of FS-LASIK operation, which could cause symptoms of asthenopia. Our data showed all the binocular visual functions returned to baseline level after 30 days of operation.

Comparison of Vision Correction and Corneal Thickness at 180-Day Follow-Up After Femtosecond Laser-Assisted In-Situ Keratomileusis (FS-LASIK), Photorefractive Keratectomy (PRK), and Small Incision Lenticule Extraction (SMILE): A Study from a Single Center in Poland of 120 Patients with Myopia.

BACKGROUND This study from a single center in Poland included 120 patients with myopia, and the aim was to compare vision correction and corneal thickness at the 180-day follow-up after femtosecond laser-assisted in-situ keratomileusis (FS-LASIK), photorefractive keratectomy (PRK), or small incision lenticule extraction (SMILE). MATERIAL AND METHODS The effectiveness and safety of laser vision correction (LVC) procedures were evaluated by determining pre- and post-procedure uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) values on the Snell chart. Twenty patients with diagnosed mild myopia (sphere maximum -3.0 diopters D; cylinder maximum 0.5 D) were qualified for PRK surgery. Fifty patients with diagnosed intolerance (sphere maximum -6.0 D; cylinder maximum 5.0 D) were eligible for the FS-LASIK procedure. Fifty patients with diagnosed myopia (sphere maximum -6.0 D cylinder 3.5 D) were qualified for the SMILE procedure. RESULTS Regardless of which procedure was performed, both UDVA and CDVA improved significantly postoperatively (P<0.05). In addition, the UDVA and CDVA values were similar in the postoperative period (P>0.05). For each procedure, the EI was no less than 0.94. Regardless of which type of LVC procedure was performed, CET at the center and 1.5 mm from the center in 4 meridians thickened, and this change was not statistically significant over the observation period (P>0.05). CONCLUSIONS Our analysis demonstrated similar effectiveness of the 3 methods - PRK, FS-LASIK, and SMILE - in patients with mild and moderate myopia.

Comparison of Changes in Corneal Thickness and Curvature After Myopia Correction Between SMILE and FS-LASIK.

To comparatively investigate the changes in corneal thickness and curvature between small incision lenticule extraction (SMILE) and femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). Data were collected preoperatively and postoperatively at 1 week, 1 month, and 3 months, including central corneal thickness (CCT), midperipheral corneal thickness (MPCT), peripheral corneal thickness (PCT), central keratometry (CK), midperipheral keratometry (MPK), and peripheral keratometry (PK), using a dual rotating Scheimpflug analyzer. At 1 week postoperatively, changes in CCT, MPCT, PCT, and PK were significantly greater in the SMILE group than in the FS-LASIK group (P = .003 for CCT and < .001 for MPCT, PCT, and PK), but no significant inter-group differences were found between changes in CK and MPK (P = .883 and .513, respectively). CCT, MPCT, and PK values showed a similar increase in both groups, but significantly more increase in PCT and significantly less increase in CK and MPK was observed in the SMILE group from 1 week to 3 months after surgery. At 3 months postoperatively, CCT and MPCT were significantly thinner in the SMILE group than in the FSLASIK group (P = .018 and .022, respectively), and there was no significant difference in PCT, CK, MPK, and PK between the two groups. SMILE caused significantly more corneal thinning at the center, midperiphery, and periphery, and more corneal flattening at the periphery, compared to FS-LASIK. A different pattern of corneal remodeling was observed between the two surgeries during the 3-month follow-up period. [J Refract Surg. 2023;39(1):15-22.].

Changes in accommodation in children with hyperopic anisometropia and unilateral amblyopia after laser refractive surgery and pleoptic treatment

This study comparatively analyzes the state of accommodation in children with hyperopic anisometropia and amblyopia after femtosecond laser-assisted in situ keratomileusis (Femto-LASIK) combined with pleoptic treatment, and after conventional pleoptic treatment. The first group consisted of 30 children with medium and high hyperopia, high and medium amblyopia, and anisometropia greater than 3.0 diopters, who underwent Femto-LASIK in the amblyopic eye. The second group consisted of 28 children with similar local status, who were prescribed traditional correction and received conservative treatment. The follow-up period was 1.5 years. After 1.5 years, higher visual acuity (p<0.05) was achieved in the first group. A significant increase in the coefficient of accommodative response (CAR) was observed in the operated amblyopic eyes in group 1 - by 0.1±0.02 c.u. compared to the control group (p<0.05). In both groups there was an upwards trend for the coefficient of microfluctuations (CMF) in the amblyopic eye, but in the first group CMF increased more significantly (p<0.05). The objective accommodative response (OAR) and positive relative accommodation (PRA) of the amblyopic eye showed a double increase - by 1.0±0.23 and 0.9±0.38 diopters, respectively, at the end of treatment in the first group. The increase in similar indicators in the second group was insignificant (p<0.05). In children of the first group the difference in ciliary muscle thickness (CMT) of the amblyopic eye with disabled and enabled accommodation increased by 0.04±0.01 mm (p<0.05) in the anterior part of the ciliary muscle at the levels of CMTmax and CMT1. The data obtained in this study indicate the strong effect of refractive laser surgery in combination with pleoptic treatment on improving the visual acuity and the state of accommodation of the amblyopic and paired dominant eyes in children with hyperopic anisometropia, in contrast to conventional methods of treatment.

Two-Dimensional Peripheral Refraction and Image Quality for Four Types of Refractive Surgeries.

To provide a comprehensive investigation of the optical quality across the visual field for current mainstream types of refractive surgeries. Sixty eyes from 60 adults who received refractive surgery of either femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK), Q-value guided customized laser in situ keratomileusis (Q-LASIK), small incision lenticule extraction (SMILE), or Implantable Collamer Lens (ICL) (STAAR Surgical) implantation were included in this study. Refraction and optical aberrations from a visual field of horizontal 60° (from temporal 30° to nasal 30°) and vertical 36° (from superior 20° to inferior 16°) were measured using a custom-made Hartmann-Shack wavefront peripheral sensor. Refractive error, higher order aberrations, point spread function (PSF), and Strehl ratio were compared among these groups prior to and after the surgical procedures, respectively. All types of surgical procedures achieved an almost plano refraction in the central retina. This was also the case in the peripheral retina for the three types of laser refractive surgeries. However, residual peripheral relative hyperopic defocus was observed after ICL implantation. In all groups prior to the surgery, PSFs showed increasing distortion with eccentricity and arrow-like shape pointing toward the central fovea in the periphery in diagonals. Degradation of the PSFs was diminished by all three types of laser refractive surgeries, whereas ICL implantation made the peripheral distortion more prominent. Although ICL implantation produced a similar impact on refractive correction and objective optical quality in the central vision compared with other laser refractive surgeries, its outcome on the peripheral optics is different. The impact of this difference on visual performance deserves notice and warrants further investigation. [J Refract Surg. 2023;39(1):40-47.].