Effect of preoperative keratometry on visual outcomes after small-incision lenticule extraction for myopia

PURPOSE

To investigate the relationship between preoperative keratometry (K) and postoperative refraction and compare the visual outcomes after small-incision lenticule extraction (SMILE) between preoperative flat and steep corneas.

METHODS

This study involved 814 consecutive eyes of 409 patients who underwent SMILE. A month later, a linear regression analysis of the relationship between preoperative K and the residual spherical equivalent (SE) along with eyes divided by a single standard deviation between flat and steep corneas (< 41.85 D, > 44.57 D, respectively) was conducted. Eyes were distinguished based on the degree of myopia.

RESULTS

One month after surgery, no significant correlation existed between mean preoperative K and residual SE (P = 0.459). Linear regression analysis showed a weak negative correlation between flat corneas (r2 = 0.042, P = 0.025) rather than steep corneas (P = 0.908). Eyes with preoperative low myopia (< 3.00 D) (r2 = 0.233, P = 0.001) had a weak correlation compared with moderate and high myopia (P = 0.272, P = 0.257, respectively). Twelve months later, the predictability, safety, and efficacy did not vary between preoperative flat and steep corneas (P > 0.05).

CONCLUSIONS

One month after SMILE for myopia, the corneas were flatter in the preoperative flat corneas or all the low myopic corneas, and they were more overcorrected. However, preoperative corneal curvature does not influence visual outcomes at 1 year after SMILE.

Small Incision Lenticule Extraction (SMILE) for the Correction of High Myopia With Astigmatism

PURPOSE

To report the outcomes of small incision lenticule extraction (SMILE) for high myopia between -9.00 and -14.00 diopters (D).

METHODS

This was a prospective study of SMILE for high myopia using the VisuMax femtosecond laser (Carl Zeiss Meditec). Inclusion criteria were attempted spherical equivalent refraction (SEQ) between -9.00 and -14.00 D, cylinder up to 7.00 D, corrected distance visual acuity (CDVA) of 20/40 or better, age 21 years or older, and suitable for SMILE. The sub-lenticule thickness was 220 µm or greater, and the total uncut stromal thickness was 300 µm or greater. Patients were to be followed up for 1 year. Standard outcomes analysis was performed using 12-month data where available or 3-month data otherwise.

RESULTS

Of 187 eyes treated, data were available at 12 months for 181 eyes (96.8%) and 3 months for 4 eyes (2.1%), and 2 eyes (1.1%) were lost to follow-up. Mean attempted SEQ was -10.55 ± 1.00 D (range: -9.00 to -12.99 D). Mean cylinder was -1.19 ± 0.83 D (range: 0.00 to -4.00 D). Preoperative CDVA was 20/20 or better in 73% of eyes. Postoperative uncorrected distance visual acuity was 20/20 or better in 57% and 20/25 or better in 82% of eyes. Mean SEQ relative to target was -0.22 ± 0.48 D (range: -1.63 to +1.38 D), 66% ± 0.50 D and 93% ±1.00 D. Mean SEQ 12-month change was -0.08 ± 0.34 D (range: -1.75 to +0.88 D). There was loss of one line of CDVA in 4% of eyes, and no eyes lost two or more lines. Contrast sensitivity was unchanged. Patient satisfaction was 8 or more out of 10 in 94% and 6 or more in 99% of patients.

CONCLUSIONS

Outcomes of SMILE for myopia greater than -9.00 D at 3 to 12 months showed excellent efficacy, safety, stability, and predictability, with high patient satisfaction. [J Refract Surg. 2022;38(5):262-271.].

Trifocal IOL Implantation in Eyes With Previous Laser Corneal Refractive Surgery: The Impact of Corneal Spherical Aberration on Postoperative Visual Outcomes

PURPOSE

To analyze corneal aberrations and factors affecting visual outcomes after implantation of a trifocal intraocular lens (IOL) in eyes previously treated with laser corneal refractive surgery.

METHODS

This retrospective case series included 222 consecutive eyes implanted with the trifocal FineVision Micro-F IOL (PhysIOL) after laser corneal refractive surgery. The series was divided into two groups according to safety outcomes after lensectomy: eyes with loss of one or more lines of corrected distance visual acuity (CDVA) [n = 59, 26.5%]) (failed eyes group) and eyes with no loss or gain in CDVA lines (n = 163, 73.4%]) (successful eyes group). Distribution of tomographic corneal aberrations (spherical aberration [Z⁴₀], comatic and root mean square of higher order aberrations [RMS-HOA]), laser corneal refractive surgery error, kappa angle, and CDVA after laser corneal refractive surgery were compared among both groups.

RESULTS

Mean CDVA after lensectomy was 0.15 ± 0.07 logMAR (range: 0.05 to 0.30 logMAR) versus 0.03 ± 0.04 logMAR (range: 0.00 to 0.15 logMAR) in the failed and successful eyes groups, respectively (P < .001). Comparison of both groups showed that failed eyes had a statistically significantly higher grade of hyperopic laser corneal refractive surgery than successful eyes measured as mean sphere (+0.71 ± 3.10 diopters [D] [range: -7.75 to +6.00 D] vs -0.46 ± 3.70 D [range: -10.75 to +6.00 D], P < .01), spherical equivalent (+0.27 ± 3.10 D [range: -8.00 to +5.50 D] vs -0.97 ± 3.60 D [range: -12.50 to +4.90 D], P < .05), and percentage of hyperopic laser corneal refractive surgery (64% vs 43.5%, P < .05). Corneal aberration analysis showed that mean Z⁴₀ values were significantly more negative in the failed eyes group than in the successful eyes group (+0.07 ± 0.40 mm [range: -0.82 to +0.65 mm] vs +0.18 ± 0.37 mm [range: -0.79 to +0.87 mm], P < .05). Laser corneal refractive surgery cylinder was distributed homogeneously between both groups, as well as coma and RMS-HOA, kappa angle, and CDVA after laser corneal refractive surgery that were not statistically significant.

CONCLUSIONS

Surgeons should consider tomographic corneal spherical aberration after implantation of a trifocal IOL in eyes after keratorefractive surgery, particularly in eyes previously treated with hyperopic laser corneal refractive surgery, to prevent loss of lines of visual acuity after lensectomy. [J Refract Surg. 2022:38(4):222-228.].

[Advances in the research of centration in small incision lenticule extraction]

Small incision lenticule extraction (SMILE) is a new technique that exhibits excellent efficacy, safety and predictability for the correction of myopia and myopic astigmatism. However, one potential limitation of this technique is that the centration during femtosecond laser cutting might be subject to the surgeon's experience and patient's cooperation. To achieve accurate centration in SMILE is the key to obtaining good postoperative visual outcomes. This review summarizes relevant research results and discusses the centration methods and the influencing factors in SMILE, so as to provide reference for clinical practice of SMILE.

Visual and Refractive Outcomes Following SMILE to Correct Myopia Performed by Surgeons in Training

PURPOSE

To assess visual outcomes and complications following small incision lenticule extraction (SMILE) performed by cornea fellows under the supervision of experienced surgeons.

METHODS

This retrospective, noncomparative case series was designed to assess outcomes following SMILE procedures performed at a large surgical center by cornea fellows between May 1, 2012 and March 30, 2015. Preoperative and postoperative uncorrected distance visual acuity (UDVA), preoperative and postoperative corrected distance visual acuity (CDVA), spherical equivalent (SE) up to -10.00 diopters (D), and complications were recorded.

RESULTS

A total of 114 patients (228 eyes) met the inclusion criteria. The mean preoperative SE was -5.79 ± 1.95 D (range: -1.75 to -10.00 D) and the mean cylinder was -2.21 ± 1.43 D (range: 0.00 to -5.50 D). At the last follow-up visit (average: 6.4 months), 94% of the patients achieved a UDVA of 20/30 or better and 96% of the patients achieved stability in their vision. Adverse events were encountered in 40 eyes (17.5%), with epithelial defect being the most common. Two patients required a second intervention to improve visual outcomes.

CONCLUSIONS

SMILE performed by cornea fellows under the supervision of an experienced surgeon is an effective and safe refractive procedure with a short learning curve and excellent visual outcomes. [J Refract Surg. 2022;38(1):28-34.].

Bilateral Lenticule Creation Followed by Bilateral Lenticule Separation Improves Visual Outcomes After SMILE

PURPOSE

To explore the impact of different surgical sequences on the visual and refractive outcomes of bilateral small incision lenticule extraction (SMILE) surgery using propensity score matching (PSM) analysis.

METHODS

Participants who underwent uneventful SMILE between March 2018 and September 2019 were retrospectively analyzed and were divided into two groups: Sequence A (laser scanning [LS] of the right eye, manual separation lenticule [MSL] of the right eye, and LS and MSL of the left eye) and Sequence B (LS of the right eye, LS of the left eye, MSL of the left eye, and MSL of the right eye). PSM was conducted to minimize the effect of confounding factors on postoperative visual outcomes at days 1 and 7 and months 1, 3, and 6. Safety, efficacy, predictability, and stability were compared between groups.

RESULTS

Overall, 1,854 eyes of 927 participants were included (Sequence A, n = 280; Sequence B, n = 647). After PSM, there were no significant differences in baseline characteristics, and 534 eyes (267 patients) in the Sequence A group were matched (1:1) to the Sequence B group. The postoperative corrected distance visual acuity significantly differed between groups at 3 months (adjusted P = .007). The uncorrected distance visual acuity significantly differed between groups at all follow-up visits (adjusted P < .01). The safety index (1.341 ± 0.265 and 1.413 ± 0.294) and efficacy index (1.173 ± 0.191 and 1.251 ± 0.269) were different in the Sequence A and Sequence B groups, respectively, at 3 months (adjusted P < .01). No difference in visual outcomes was found between right and left eyes.

CONCLUSIONS

Patients who had bilateral lenticule creation followed by bilateral lenticule separation had better postoperative visual outcomes than those who underwent complete SMILE surgery in each eye separately. Regardless of the surgical sequence chosen for the SMILE procedure, there was no impact on outcomes between the right and left eyes. Adjusting the sequence of the surgical procedure may be a way to improve the visual results. [J Refract Surg. 2021;37(11):726-733.].

CIRCLE Software for Management of Epithelial Ingrowth After SMILE

PURPOSE

To report a novel therapeutic use of CIRCLE software (Carl Zeiss Meditec) to manage visually significant epithelial ingrowth following small incision lenticule extraction surgery (SMILE).

METHODS

Case series.

RESULTS

In this case series, the authors describe three eyes with progressive and visually significant epithelial ingrowth following an uneventful SMILE procedure. The management of epithelial ingrowth following SMILE is challenging, given the small access incision to the interface and the risk of incomplete removal. All cases were successfully managed by converting the SMILE cap into a flap using the CIRCLE software, which provided the necessary access to the original SMILE interface. Once the flap was lifted, the epithelial in-growth was completely debrided from the underlying stroma and undersurface of the flap, followed by a thorough interface wash. Postoperative recovery was uneventful, with no recurrence noted in any of the eyes.

CONCLUSIONS

Use of CIRCLE software provides a novel and unique approach to successfully treating vision-threatening epithelial ingrowth after SMILE. [J Refract Surg. 2021;37(11):776-780.].

Monson small-incision lenticule extraction fixation device

Small-incision lenticule extraction (SMILE) is a stromal based, flapless, minimally invasive form of laser vision correction for the treatment of myopia and myopic astigmatism. SMILE surgery is a more technical procedure compared with other refractive surgeries and generally has a longer skill mastery acquisition period. Thus far, no new stabilization devices or techniques have been proposed. To rectify this, a new distal corneal countertraction device for SMILE surgery, the Monson SMILE Fixation Device, is introduced. This device provides reliable corneal and globe stabilization during delamination and lenticular dissection. It may minimize tissue distortion and manipulation, simplify lenticule dissection, and may decrease operation times and improve cosmesis. Countertraction can also easily be adjusted throughout the procedure.

Femtosecond Laser-Assisted Small Incision Allogeneic Endokeratophakia Using a Hyperopic Lenticule in Rabbits

Purpose

To investigate the morphologic and histopathologic changes in allogeneic endokeratophakia using hyperopic lenticules derived from small-incision lenticule extraction (SMILE).

Methods

Six New Zealand rabbits (12 eyes) were included in this experiment and randomly and evenly divided into donor and recipient groups. The donor group underwent bilateral hyperopic SMILE surgery, and the concave lenticules were implanted into eyes in the recipient group. Corneal topography and anterior segment optical coherence tomography (OCT) examinations were performed at 1 day, 1 week, 1 month, and 5 months after surgery. All eyes were enucleated 5 months after surgery. Hematoxylin and eosin (HE) staining and transmission electron microscopy (TEM) were used to observe the corneal morphology in the recipient group.

Results

No complications were observed, and the corneas remained transparent in the follow-up period. There was mild corneal edema within 1 week after surgery. Slit-lamp microscopy and OCT showed that the lenticules were gradually integrated with the surrounding corneal stroma. HE staining showed that the arrangement of corneal collagen was regular. The boundary between the lenticules and surrounding tissue could be identified with HE staining and TEM, and no inflammatory cells were found under TEM. The corneal Km values were significantly lower at 5 months postoperatively compared to preoperatively (P < 0.05).

Conclusions

This pilot study showed that allogeneic hyperopic SMILE lenticule endokeratophakia seems to be safe and feasible.

Translational Relevance

Allogeneic hyperopic SMILE lenticule endokeratophakia may be applicable for the correction of corneal regression, ectasia, ultra-high myopia, or keratoconus.

Risk Evaluation of Human Corneal Stromal Lenticules From SMILE for Reuse

PURPOSE

To investigate the pathogenicity and immunogenicity of human corneal stromal lenticules from small incision lenticule extraction (SMILE).

METHODS

Serological testing was completed prior to sample collection to rule out infectious diseases. Pathogens herpes simplex viruses (HSV) type 1 and type 2 were screened for by real-time fluorescent quantitative polymerase chain reaction, and bacteria, fungi, and Acanthamoeba from 128 lenticules of 64 patients were cultured. A total of 132 lenticules from 93 patients were randomly assigned to the fresh group, -78 °C anhydrous glycerol preservation group (glycerol group), and 0.1% sodium dodecyl sulfate decellularization group (SDS group) in pairs and detected by immunohistochemistry, Western blot, transmission electron microscopy, transmittance, and nanoindentation.

RESULTS

The fresh lenticules were all negative for HSV-1, HSV-2, bacteria, fungi, and Acanthamoeba. HLA-I A/B/C and HLA-II DR antigens were all expressed in fresh lenticules but were clearly reduced after preservation at -78 °C in anhydrous glycerol or decellularization in 0.1% SDS. The collagen fibers of the lenticules in the fresh group were regularly arranged, and the keratocytes were intact. The fibers in the glycerol group were regularly arranged, and the integrity of keratocytes was destroyed. The fibers in the SDS group were disordered and had no cellular structure. The transmittance and Young's modulus were highest in the fresh group, lower in the glycerol group, and lowest in the SDS group.

CONCLUSIONS

Risk of infection is low, but risk of rejection exists on the reuse of fresh human corneal stromal lenticules from SMILE. Anhydrous glycerol preservation at -78 °C is an ideal method for reducing antigens without damaging the structure and function of lenticules. [J Refract Surg. 2021;37(1):32-40.].

Tear Neuromediator and Corneal Denervation Following SMILE

PURPOSE

To investigate the changes in tear neuromediators and corneal subbasal nerve plexus following small incision lenticule extraction (SMILE) and to study its association with different refractive power of corrections.

METHODS

Thirty patients were included for tear neuromediator analysis (40 eyes) and corneal nerve analysis using in vivo confocal microscopy scans (20 eyes). Tear samples were collected preoperatively and 1 week and 1, 3, 6, and 12 months postoperatively and analyzed for the substance P, calcitonin gene-related peptide (CGRP), and nerve growth factor (NGF) concentrations using the enzyme-linked immunosor-bent assay (ELISA).

RESULTS

Corneal nerve fiber density (CNFD), corneal nerve fiber length (CNFL), and corneal nerve branch density (CNBD) decreased significantly postoperatively, then gradually increased from 3 months onward, but did not recover to the baseline levels at 12 months. Tear substance P and CGRP levels remained stable over 12 months. Tear NGF levels demonstrated a small peak at 1 week before decreasing significantly compared to preoperative levels at 6 months (P = .03) and 12 months (P = .007). The 1-month reduction in CNFL, tear substance P, and CGRP concentrations were significantly correlated with the corrected spherical equivalent (SE) (r = 0.71 for CNFL; r = -0.33 to -0.52 at different time points for substance P and CGRP, respectively, all P < .05). Compared to the low to moderate myopia group, the high myopia group (corrected SE greater than -6.00 diopters) had a significantly greater decrease in CNFD, significantly higher tear substance P concentrations at 1 week, 1 month, and 6 months, and significantly higher tear CGRP concentrations at 1 and 6 months.

CONCLUSIONS

These results provide new insight into the neurobiological responses and their potential implications in corneal nerve damage and recovery after SMILE. High myopia treatment was associated with greater corneal denervation and neuroinflammation. [J Refract Surg. 2021;37(8):516-523.].

Customized Stromal Lenticule Implantation for Keratoconus

PURPOSE

To investigate the potential benefit of keratoconus surgery using customized corneal stromal donor lenticules obtained from myopic small incision lenticule extraction (SMILE) surgery by femtosecond laser.

METHODS

In this prospective, consecutive, non-comparative series of cases, 22 lenticules were obtained from 22 myopic patients who had SMILE with a lenticule central thickness of greater than 110 µm. The lenticules were implanted in 22 eyes with advanced keratoconus. The lenticules were customized for the purpose of the implantation with either a simple necklace or necklace-with-ring shape (compound form) depending on the corneal thickness and corneal topography configuration of the implanted keratoconic eyes. The lenticules were implanted into a 9.5-mm corneal lamellar pocket created by the femtosecond laser. Changes in densitometry, thickness, confocal microscopy, corrected distance visual acuity (CDVA), and endothelial cell density were investigated.

RESULTS

Intrastromal lenticule implantation was successfully performed in all cases without any complication. Corneal thickness showed a mean enhancement of 100.4 µm at the thinnest point. On biomicroscopy, all corneas were clear at 1 year postoperatively and there was a significant improvement in corneal densitometry during the entire follow-up period. Confocal biomicroscopy showed collagen reactivation without any inflammatory features caused by the implanted fresh lenticules. CDVA improved from 0.70 to 0.49 logMAR (P = .001) and keratometry decreased from 54.68 ± 2.77 to 51.95 ± 2.21 diopters (P = .006).

CONCLUSIONS

Customized SMILE lenticule implantation by femtosecond laser proved to be feasible, resulting in an improvement in vision, topography, and refraction in the implanted eyes. [J Refract Surg. 2020;36(12):786-794.].

Feasibility, Safety, and Outcomes With Standard Versus Differential Spot Distance Protocols in Eyes Undergoing SMILE for Myopia and Myopic Astigmatism

PURPOSE

To study the feasibility, safety, comparison of intraoperative ease of dissection, and immediate visual outcomes with standard versus differential small incision lenticule extraction (SMILE) spot settings in eyes undergoing bilateral SMILE for myopia or myopic astigmatism.

METHODS

One hundred eyes of 50 patients (mean age: 25.4 years) were randomized to receive standard settings (4.5-µm spot and track spacing in cap and lenticule interface) in one eye and differential settings (4.5-µm spot and track spacing in cap interface and 4.2 µm in lenticule interface) in the contralateral eye. Opaque bubble layer (OBL) was graded using a new grading system and a surgeon questionnaire was obtained to grade the ease of dissection (from 0 to 5, with 5 being the easiest) at the end of each surgery. Visual results and optical quality were analyzed at 1 day, 2 weeks, and 3 months postoperatively.

RESULTS

The mean OBL score was significantly lower in the differential group (26.3%) compared to the standard group (35.3%) (P < .01). Consequently, the mean dissection score was significantly higher in the differential group (4.01) compared to the standard group (3.57) (P < .01). The uncorrected distance visual acuity, Objective Scatter Index, modulation transfer function cut-off, and higher order aberrations were comparable with no statistically significant difference between both groups at 1 day, 2 weeks, and 3 months postoperatively (P > .05 for all parameters). No eye in either group had any intraoperative or postoperative complication affecting visual recovery.

CONCLUSIONS

Differential spot settings resulted in less intraoperative OBL and easy separability. However, the visual results and optical quality were comparable between groups. [J Refract Surg. 2021;37(5):294-302.].

Corneal Epithelial Thickness Changes Following SMILE for Myopia With High Astigmatism

PURPOSE

To evaluate the corneal epithelial thickness (CET) profile changes after small incision lenticule extraction (SMILE) surgery for myopic astigmatism correction of greater than 2.00 diopters (D).

METHODS

This prospective observational study included 40 eyes (23 patients) treated with SMILE for myopia with cylinders of -2.25 to -4.50 D. Along with standard ophthalmic examinations, CET maps with a diameter of 9 mm were measured by high-resolution spectral-domain optical coherence tomography preoperatively and postoperatively. Correlations between the degree of residual astigmatism and the difference in CET values between preoperative flat and steep meridians were analyzed.

RESULTS

The CET showed significant changes in the central (2 mm), paracentral (2 to 5 mm), midperipheral (5 to 7 mm), and peripheral (7 to 9 mm) zones 6 months after SMILE (P < .001). Among the regions, the CET in the paracentral zones displayed the largest increase (9.75%) with the highest average thickness (57.29 µm). Moreover, symmetrical regional epithelial thickening at the preoperative astigmatism axis was observed in the midperipheral zones. The difference in CET between preoperative flat and steep meridians in the mid-peripheral zones continuously increased from postoperative 1 day to 6 months. This difference was positively correlated with the residual cylinder errors at 6 months postoperatively (r = -0.334, P = .035).

CONCLUSIONS

The 9-mm diameter CET in eyes with high astigmatism significantly increased 6 months after SMILE. Additionally, the difference in CET between preoperative flat and steep meridians in midperipheral zones may be related to astigmatic undercorrection in SMILE. [J Refract Surg. 2021;37(4):224-230.].

Comparison of Clinical Outcomes and Visual Quality Using a Medium Versus Small Contact Glass in Patients Undergoing SMILE With Large Corneal Diameters

PURPOSE

To compare the clinical outcomes and visual quality using a small (S) versus medium (M) size contact glass in eyes with large white-to-white (WTW) distance undergoing bilateral small incision lenticule extraction (SMILE) for myopia correction.

METHODS

This contralateral eye study involved 60 eyes of 30 patients (mean age: 27.20 years) undergoing bilateral SMILE for myopia/myopic astigmatism with a WTW distance of 12 mm or greater in both eyes, which were randomized to receive treatment with an S-contact glass in one eye and an M-contact glass in the fellow eye. Opaque bubble layer (OBL) was graded using a new grading system. On postoperative 1 day, 2 weeks, and 3 months, UDVA, CDVA, contrast sensitivity, Objective Scatter Index, and modulation transfer function cut-off values were compared between the two groups.

RESULTS

The mean OBL score was significantly lower in the S-contact glass group (28.18%) compared to the M-contact glass group (67.13%) (P < .01). At 1 day postoperatively, the UDVA, Objective Scatter Index score, and contrast sensitivity values for all spatial frequencies were significantly better in eyes treated with the S-contact glass compared to the M-contact glass (P ⩽ .05). At 3 months postoperatively, however, the UDVA, Objective Scatter Index score, modulation transfer function cut-off, and contrast sensitivity values were comparable for both groups. No eye in either group had intraoperative complications such as suction loss, incision/lenticule tears, or lenticule retention.

CONCLUSIONS

In corneas with a WTW distance of 12 mm or greater, docking with the S-contact glass resulted in significantly better immediate visual results due to less OBL formation and smoother tissue dissection compared to the M-contact glass. [J Refract Surg. 2021;37(3):150-157.].

[Relation between corneal biomechanical alteration after small incision lenticule extraction and intraoperative cutting thickness]

Objective: To explore the rule of corneal biomechanical alteration with residual stromal thickness (RST) and percent tissue altered (PTA) after small incision lenticule extraction (SMILE) and to determine the factors influencing postoperative corneal biomechanical properties. Methods: In this retrospective study, a total of 184 patients (184 right eyes) who underwent SMILE in Tianjin Eye Hospital Refractive Surgery Center from January 2019 to January 2020 were enrolled. There were 83 males and 101 females with age of (24.6±5.8) years. Corneal biomechanical parameters, including DA ratio, stiffness parameter at the first applanation (SPA1) and integrated radius (IR), were measured with Corvis ST preoperatively and at 3 months postoperatively. The association between PTA, RST and the changes of DA ratio, SPA1 and IR was assessed by linear and nonlinear regression analyses. Stepwise multivariate regression analyses were conducted to explore the factors associated with postoperative corneal biomechanical parameters with age, sex, anterior mean keratometry, spherical equivalent, postoperative central corneal thickness (CCT) and preoperative corneal biomechanical parameters as covariates. Preoperative and postoperative data were compared using the paired t test. Correlations were determined by the Pearson or Spearman analysis. Results: The alterations at 3 months postoperatively of DA ratio, SPA1 and IR were 1.33 (30.0%), 28.05 (26.0%) and 2.56 (34.0%), respectively. The changes before and after surgery were statistically significant (t=35.52, -28.00, 36.95, P<0.01). The best-fit curve showed that the changes of DA ratio, SPA1 and IR increased with the decrease of RST or increase of PTA. When the RST was<280 μm or the PTA was>28%, the slope of the change of DA ratio curve was significantly increased. Multivariate regression models showed that the factors with the greatest influence on postoperative DA ratio, SPA1 and IR were preoperative DA ratio (Sβ=0.489, P<0.01), preoperative SPA1 (Sβ=0.483, P<0.01) and preoperative IR (Sβ=0.471, P<0.01), respectively. The CCT was the second factor that influenced postoperative DA ratio and SPA1 (Sβ=-0.238, P<0.01; Sβ=0.326, P<0.01). Conclusions: The changes of DA ratio, SPA1 and IR following SMILE increased with the decrease of RST or increase of PTA. With the RST<280 μm or the PTA>28%, the alteration of DA ratio significantly accelerated. Preoperative corneal biomechanical properties and postoperative CCT were main factors influencing corneal biomechanical properties after SMILE. (Chin J Ophthalmol, 2021, 57: 104-112).

Transient corneal ectasia after phacoemulsification in an eye with femtosecond intrastromal presbyopic treatment

We report a case of transient corneal ectasia developed after phacoemulsification in an eye previously treated with INTRACOR. There was a myopic refractive surprise after cataract surgery. Corneal tomography showed an increase in keratometry and elevation profile compared with preoperative examination. Soft contact lenses and intraocular pressure-lowering medications were prescribed as interim treatment. Clinical improvement was seen gradually, and the resolution of myopia and ectasia was achieved at 3 months. We believe that high intraocular pressure during phacoemulsification and the weakening effect of femtosecond intrastromal presbyopic treatment can be the culprits.

Influence of Cap Thickness on Corneal Curvature and Corneal Biomechanics After SMILE: A Prospective, Contralateral Eye Study

PURPOSE

To evaluate the impact of cap thickness for small incision lenticule extraction (SMILE) on changes in corneal curvature and biomechanics.

METHODS

One hundred eyes (50 patients) were enrolled in this prospective contralateral eye study. The difference in manifest refraction spherical equivalent (MRSE) in the same patient was less than 0.50 diopters. SMILE was performed with a randomized cap thickness of 110 µm in one eye and 140 µm in the other eye. MRSE, uncorrected distance visual acuity (UDVA), and corneal curvature and biomechanics were evaluated. The anterior and posterior surfaces of the corneal curvature (mean keratometry [Km] values 2, 4, and 6 mm from the pupil center) were measured by Pentacam HR (Oculus Optikgeräte, Wetzlar, Germany) and changes in corneal biomechanics at 6 months postoperatively by Scheimpflug technology.

RESULTS

There was no significant between-group difference in UDVA or MRSE postoperatively. Postoperative changes in Km at the anterior surface (ΔKm-ant) in the 4-mm zone were significantly higher in the 110-µm group than in the 140-µm group at 1 day and 1, 3, and 6 months postoperatively (P = .043, .045, .003, and .049, respectively); at 3 months, the ΔKm-ant in the 6-mm zone was higher in the 110-µm group (P = .035). The changes in second appla-nation time, deformation amplitude, and integrated radius were significantly less in the 110-µm group (P = .031, .049, and < .001, respectively).

CONCLUSIONS

A thicker corneal cap caused less change in anterior surface curvature after SMILE for moderate or low myopia, with no significant difference in UDVA and MRSE. [J Refract Surg. 2020;36(2):82-88.].

Femtosecond Laser-Assisted Allogenic Lenticule Implantation for Corneal Ectasia After LASIK: A 3-Year In Vivo Confocal Microscopic Investigation

PURPOSE

To investigate morphological changes in the cornea and the implanted lenticule in patients with corneal ectasia after laser in situ keratomileusis (LASIK) and implantation using a lenticule from small incision lenticule extraction (SMILE).

METHODS

Eight eyes of 8 patients with ectasia after LASIK from 2015 to 2018 at the Eye and ENT Hospital of Fudan Unversity were analyzed. For recipient eyes, lenticules were transferred with a mean cryopreserved time of 20 ± 21 days extracted from SMILE donors to the exposed stromal bed after lifting the flaps and the flap was repositioned. Uncorrected and corrected distance visual acuity, manifest refraction, and corneal topography were performed. Patients were followed up for 3 years. Changes in lenticules and recipient corneas were analyzed using in vivo confocal microscopy.

RESULTS

Activated keratocytes in the anterior and posterior stroma were observed near the lenticule at the first 6 months. Elongated, deformed keratocyte nuclei were found in the implanted lenticules in postoperative year 1. The anterior and posterior interfaces showed an absence or decrease of keratocytes and the presence of small particles of varying brightness. Nerve fibers in the implanted lenticules were detected in one case. No obvious difference was detected between cryopreserved and fresh lenticules.

CONCLUSIONS

The preliminary findings suggest that recipient keratocytes repopulate the lenticules and the keratocytes in lenticules gradually return to their normal morphology. [J Refract Surg. 2020;36(11):714-722.].

Influence of Cap Thickness on Opaque Bubble Layer Formation in SMILE: 110 Versus 140 µm

PURPOSE

To investigate the impact of cap thickness on the formation of an opaque bubble layer (OBL) during small incision lenticule extraction procedures.

METHODS

In total, 100 eyes from 50 patients were prospectively examined. One of two corneal cap thicknesses was randomly assigned to each eye and differed in the contralateral eye: 110 µm in one eye and 140 µm in the other. OBL area and density were quantitatively assessed.

RESULTS

The proportion of OBL areas in the anterior lenticule plane was 11.70% ± 7.35% in the 110-µm group, which was significantly higher than the 140-µm group (6.64% ± 4.68%, P < .001). For OBL areas located in the posterior lenticule plane, mean areas for the 110-µm group were also higher than those for the 140-µm group (1.32% ± 1.20% and 0.94% ± 0.59%, respectively; P = .002). Mean gray values of the OBL in the posterior lenticule plane were slightly different between the two groups (P < .001), but no significant difference in OBL of the anterior lenticule plane was observed (P = .055). Eyes with a 110-µm cap thickness had more focal OBLs, revealed by cap scanning (chi-square = 10.256, P = .001).

CONCLUSIONS

Corneal cap thickness is predictive of opaque bubble layer during small incision lenticule extraction procedures. [J Refract Surg. 2020;36(9):592-596.].

Recent advances in the neurosurgical treatment of pediatric epilepsy: JNSPG 75th Anniversary Invited Review Article

The field of epilepsy surgery has seen tremendous growth in recent years. Innovative new devices have driven much of this growth, but some has been driven by revisions of existing products. Devices have also helped to rejuvenate existing procedures, as in the case of robotic assistance for electrode placement for stereo-electroencephalography, and these devices have brought significant attention along with their introduction. Other devices, such as responsive neurostimulators or laser interstitial thermal therapy systems, have introduced novel treatment modalities and broadened the surgical indications. Collectively, these advances are rapidly changing much of the landscape in the world of pediatric neurosurgery for medically refractory epilepsy. The foundations for indications for neurosurgical intervention are well supported in strong research data, which has also been expanded in recent years. In this article, the authors review advances in the neurosurgical treatment of pediatric epilepsy, beginning with trials that have repeatedly demonstrated the value of neurosurgical procedures for medically refractory epilepsy and following with several recent advances that are largely focused on less-invasive intervention. ABBREVIATIONS AED = antiepileptic drug; ANT = anterior nucleus of the thalamus; BOLD = blood oxygen level dependent; CCEP = cortico-cortical evoked potential; DBS = deep brain stimulation; ECoG = electrocorticography; ERSET = Early Randomized Surgical Epilepsy Trial; FCD = focal cortical dysplasia; HH = hypothalamic hamartoma; LITT = laser interstitial thermal therapy; RCT = randomized controlled trial; r-fMRI = resting-state functional MRI; RNS = responsive neurostimulation; SEEG = stereo-electroencephalography; VNS = vagus nerve stimulation.

Outcomes of Re-treatment by LASIK After SMILE

PURPOSE

To report the outcomes of LASIK re-treatments after small incision lenticule extraction (SMILE).

METHODS

Retrospective review of all eyes to have undergone a re-treatment by LASIK after primary SMILE between September 2013 and January 2016. Thin-flap LASIK was used in most cases as long as sufficient tissue was available for safe flap creation between the maximum epithelial thickness and minimum cap thickness. Otherwise, the SMILE interface was converted into a LASIK flap by the Circle technique or side cut only. The multivariate nomogram for LASIK re-treatments was used, including sphere, cylinder, age, and primary spherical equivalent (SEQ) as variables. Patients were observed for 1 year after surgery and standard outcomes analysis was performed.

RESULTS

A total of 116 LASIK re-treatments were performed in a population of 2,643 consecutive SMILE procedures, indicating a re-treatment rate of 4.39%. Mean attempted SEQ was -0.05 ± 0.99 diopters (D) (range: -1.88 to +1.50 D). Mean cylinder was -0.70 ± 0.55 D (range: 0.00 to -2.25 D). Postoperative uncorrected distance visual acuity was 20/20 or better in 81% of eyes, for a population with corrected distance visual acuity (CDVA) of 20/20 or better in 95% before re-treatment. Mean postoperative SEQ relative to the target was +0.19 ± 0.49 D (range: -0.88 to +2.13 D), with 74% within ±0.50 D. Mean postoperative cylinder was -0.29 ± 0.24 D (range: 0.00 to -1.25 D). There was one line loss of CDVA in 15% of eyes, but no eyes lost two or more lines. There was a small increase in contrast sensitivity (P < .05). Overcorrection was identified in myopic re-treatments (n = 20) of -1.00 D or more; mean postoperative SEQ was +0.59 ± 0.64 D (range: -0.63 to +2.13 D).

CONCLUSIONS

Re-treatment after SMILE by LASIK achieved excellent visual and refractive outcomes, although these results indicate that myopic LASIK retreatment after primary myopic SMILE requires a different nomogram than for myopic LASIK re-treatment after primary myopic LASIK. [J Refract Surg. 2018;34(9):578-588.].