Hyperopic Small Incision Lenticule Extraction Research Articles

Corneal Epithelial Remodeling After Hyperopic SMILE: A 4-Year Study.

The purpose of this study was to investigate dynamic changes in corneal epithelial thickness (ET) after hyperopic small incision lenticule extraction (SMILE). This observational study included 18 eyes of 16 patients who were scheduled for hyperopic SMILE. High-resolution spectral-domain optical coherence tomography and a custom image segmentation algorithm were applied to measure corneal dynamic ET over a central 6 mm area. ET was analyzed among different corneal sectors (central, pericentral, and peripheral) at baseline and multiple postoperative time points (1 day, 1 month, 6 months, 2 years, and 4 years). Correlation analysis was performed between ET changes and preoperative and intraoperative parameters. The mean spherical equivalent of hyperopia correction was +2.64 ± 1.00 D, and the average age of enrolled 16 patients was 32.4 ± 10.8 years. At the last follow-up, 72% of eyes kept or improved corrected distance visual acuity, with 2 eyes that lost 2 lines. 72% of eyes were within ±1.0 D of target refraction, and 56% were within ±0.5 D. Average ET decreased by 11.0% (5.9 ± 2.3 μm) from 53.2 ± 3.5 μm to 47.4 ± 4.2 μm 4 years postoperatively (P<0.001). The ET at center 2 mm decreased most significantly by 14.5% (7.9 ± 2.9 μm), followed by the pericentral area by 10.5% (5.6 ± 2.3 μm). ET and front corneal curvature stabilized 1 month after surgery. No correlation was found between refraction regression and ET changes. Hyperopic SMILE induced significant central ET thinning. ET remodeling in the 6 mm area stabilized after 1 month and did not underlie refractive changes.

Feasibility study of treatment of mixed astigmatism with small-incision lenticule extraction (SMILE) by using research software.

To report the preliminary experience and initial clinical results following SMILE for the treatment of mixed astigmatism. Thirteen eyes of nine patients with a mean age of 27 ± 4.36 years were included in the series. In 8/13 eyes, myopic SMILE license and in 4/13 eyes, hyperopic SMILE license (available as part of an open/research software) was used for the treatment. The mean follow-up was 9.5 ± 8.7 (0.5-24) months, and the median follow-up was 6 months. Nethradhama Superspeciality Eye Hospital, Bangalore, India. Exploratory study. The mean preoperative sphere, cylinder, and spherical equivalent (SE) were 1.44 ± 1.63, -2.70 ± 2.30, and -0.24 ± 1.14 D, which changed to -0.03 ± 0.30, -0.28 ± 0.48, and -0.18 ± 0.49 D, respectively, 6 months postoperatively. Furthermore, 85% (11/13) eyes were within ± 0.50 D, 92% (12/13) eyes were within ± 1.00 D, while all eyes were within ± 1.50 D of SE correction. All eyes were within ± 1.00 D of cylinder correction. In addition, 92% (12/13) eyes had UDVA better than 20/32, with 54% (7/13) eyes having UDVA 20/20 or better. Safety and efficacy indices were 1.08 and 0.92, respectively. No eyes lost more than 1 line of CDVA. The mean corneal higher order aberrations (HOA) increased from 0.111 ± 0.048 to 0.209 ± 0.056 (P < 0.001). The mean objective scatter index (OSI) did not show a significant change (pre = 0.71 ± 0.69, 6 months = 0.89 ± 0.20; P = 0.35). Early experience showed that SMILE was feasible for the management of eyes with mixed astigmatism, without any intraoperative complications, unique to the procedure.

Effective optical zone following small incision lenticule extraction: a review.

Small incision lenticule extraction (SMILE) is a "flapless" keratorefractive surgery with excellent safety, efficacy, stability, and predictability for myopia correction. A recent global multicenter study also reported good refractive outcomes for hyperopic SMILE. SMILE has shown advantages including improved biomechanical strength, fewer dry eye symptoms, less corneal denervation, and fewer surgery-induced higher-order aberrations over laser in situ keratomileusis (LASIK). However, night vision complaints, including glare, halos, and starbursts, could still occur after SMILE. These symptoms have been proven to be closely related to the effective optical zone (EOZ), which is defined as the achieved area of corneal ablation. A larger postoperative EOZ may indicate better visual quality, making EOZ an important safety parameter for keratorefractive surgeries. As SMILE has gained wider application globally, the EOZ following SMILE has also been increasingly studied in the field of refractive surgery. This review provides an update on topics related to the EOZ after SMILE, including its measurement and influencing factors, aiming to benefit the personalization of the surgical algorithm and ultimately improve the visual quality after the SMILE procedure.

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

PurposeTo investigate the morphologic and histopathologic changes in allogeneic endokeratophakia using hyperopic lenticules derived from small-incision lenticule extraction (SMILE).MethodsSix 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.ResultsNo 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).ConclusionsThis pilot study showed that allogeneic hyperopic SMILE lenticule endokeratophakia seems to be safe and feasible.Translational RelevanceAllogeneic hyperopic SMILE lenticule endokeratophakia may be applicable for the correction of corneal regression, ectasia, ultra-high myopia, or keratoconus.

Scheimpflug analysis of corneal power changes after hyperopic small incision lenticule extraction

PurposeTo assess the ability of the Pentacam in predicting the corneal power after hyperopic small-incision lenticule extraction (SMILE).MethodsTwenty-five eyes of 22 patients underwent hyperopic SMILE were prospectively followed. All patients finished at least 6 months visit. Cornea power was obtained by Pentacam HR, in the format of mean keratometry (Km), equivalent keratometry (EKR) and total cornea refractive power (TCRP). Calculation of TCRP were centered on either the corneal apex or the pupil center within a ring or zone, giving a total of four different subtypes naming AR、AZ、PR、PZ. Clinical history method (CHM) was regarded as a gold standard and was compared with other cornea power parameters.ResultsCenter difference had no impact on the TCRP values (PR vs AR and PZ vs AZ, P > 0.05). Compared with CHM, no difference was found in Km, EKR 4.0 mm, EKR 4.5 mm, PR 3.0 mm, PR 4.0 mm, AR 3.0 mm and AR 4.0 mm. PR 4.0 mm showed the least difference with CHM (− 0.14 ± 1.03D, P > 0.05). The 95% limit of agreement (LOA) of the TCRPs and CHM was not close. The top two were PR 3.0 mm and PR 4.0 mm, LOA of which were − 2.20 to 1.84 D and − 2.18 to 1.68 D respectively. Central cornea thickness was correlated with error (TCRP – CHM) of PR 4.0 mm (r = 0.58, P = 0.003).ConclusionsThe Pentacam topographer is an alternative method of measuring corneal power in eyes after hyperopic SMILE. The optimal options seem to be the TCRP (PR 4.0 mm). The agreement needs more verifications.

A pilot study: lenticule quality of hyperopic small incision lenticule extraction (SMILE) in rabbits

BackgroundTo evaluate lenticule surface characteristics of small incision lenticule extraction (SMILE) for hyperopia correction in rabbits.MethodsThe left and right eyes of 8 rabbits were divided into two groups. The right eyes were assigned to a myopia group, and the left eyes to a hyperopia group. The rabbits received SMILE procedures with + 3.00 D and − 3.00 D correction for the hyperopia and myopia groups, respectively. Extracted lenticules were examined via scanning electron microscopy. Lenticules from odd-numbered rabbits were accessed with the anterior surface, and lenticules from even-numbered rabbits were observed with the posterior surface. A previously established scoring system was used to evaluate lenticule surface characteristics. Statistical analysis was conducted to compare the scores between the two groups.ResultsAll procedures were performed successfully, and the lenticules were extracted smoothly. One myopia lenticule that was facing downward was handled failed in preparation for imaging, thus 15 lenticules were ultimately graded. Twelve lenticules exhibited smooth surfaces, and regularly arranged tissue bridges were observed in almost all regions. Three lenticules exhibited a partially rough surface and irregularities affecting more than 10% of the lenticules (2 in the hyperopia group and 1 in the myopia group). Rough lenticules occurred in twice as many lenticules in the hyperopia group compared to the myopia group.ConclusionsScan quality of lenticules after SMILE for hyperopia correction is comparable to that of myopia lenticules. The shape of hyperopic lenticule may increase the difficulty of surgical manipulation and result in surface roughness.

Intraocular pressure changes and corneal biomechanics after hyperopic small-incision lenticule extraction

BackgroundWe aimed to compare the intraocular pressure (IOP) measurements by a dynamic Scheimpflug analyzer (Corvis ST), a non-contact tonometer, and an ocular response analyzer after hyperopic small-incision lenticule extraction (SMILE).MethodsThirteen patients who underwent hyperopic SMILE in one eye were enrolled prospectively. IOP and corneal biomechanical parameters were measured preoperatively and at 1 week, 1 month, and 3 months postoperatively with a non-contact tonometer (IOPNCT), Corvis ST (biomechanical corrected IOP [bIOP]), and ocular response analyzer (Goldmann-correlated intraocular pressure [IOPg] and cornea compensated IOP [IOPcc]). A linear mixed model was used to compare the IOPs and biomechanical values among methods at each time point.ResultsIOPNCT, IOPg, and IOPcc dropped significantly after surgery, with the amplitude being 3.15 ± 0.48 mmHg, 5.49 ± 0.94 mmHg, and 4.34 ± 0.97 mmHg, respectively, at the last follow-up visit. IOPNCT decreased by 0.11 ± 0.06 mmHg per μm of excised central corneal thickness. bIOP did not change significantly after surgery. Preoperatively, no difference was found among the four measurements (P > 0.05). Postoperatively, IOPNCT and bIOP were higher than IOPg and IOPcc. bIOP was independent of cornea thickness at last follow-up visit, whereas it correlated significantly with corneal biomechanics similar to the other three IOP values.ConclusionbIOP is a relative accurate measure of IOP after hyperopic SMILE.

Small Incision Lenticule Extraction (SMILE) for Hyperopia: 12-Month Refractive and Visual Outcomes.

To evaluate visual and refractive outcomes of small incision lenticule extraction (SMILE) for hyperopia. This was a prospective study of vertex-centered hyperopic SMILE using the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany). Inclusion criteria were maximum attempted hyperopic meridian of between +1.00 and +7.00 diopters (D). Lenticule parameters were 6.3- to 6.7-mm diameter, 2-mm transition zone, 30-µm minimum thickness, and 120-µm cap thickness. A standard outcomes and stability analysis was performed for the 12-month data, including contrast sensitivity using the Functional Vision Analyzer. For the 93 eyes treated, last follow-up was 12 months for 72 eyes (77%) and 3 months for 11 eyes (12%), with 10 eyes (11%) lost to follow-up. Attempted spherical equivalent refraction (SEQ) was +5.61 ± 1.21 D (range: +1.00 to +6.90 D) and cylinder was -1.01 ± 0.64 D (range: 0.00 to -3.50 D). For eyes targeted for emmetropia (n = 37), uncorrected distance visual acuity was 20/40 or better in 95% of eyes. SEQ relative to target was -0.17 ± 0.85 D (range: -2.20 to +3.00 D) at 3 months and -0.19 ± 0.90 D (range: -2.07 to +3.50 D) at 12 months with 53% within ±0.50 D. For 70 eyes with data at 3 and 12 months, the mean change in SEQ was -0.06 ± 0.53 D (range: -2.00 to +1.75 D) and the mean change in keratometry was -0.22 ± 0.48 D (range: -1.00 to +1.00 D). There was one line loss of corrected distance visual acuity (CDVA) in 16% of eyes and no loss of two or more lines. There was no clinically significant change in contrast sensitivity. Refractive and visual outcomes 12 months after SMILE for hyperopia were promising, given the high degree of hyperopia corrected and relatively reduced CDVA in this population. There was good refractive and topographic stability between 3 and 12 months. [J Refract Surg. 2019;35(7):442-450.].

Small Incision Lenticule Extraction for Hyperopia: 3-Month Refractive and Visual Outcomes.

To evaluate visual and refractive outcomes of small incision lenticule extraction (SMILE) for hyperopia. This prospective study of vertex-centered hyperopic SMILE used the VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany). Inclusion criteria were maximum attempted hyperopic meridian of between +1.00 and +7.00 diopters (D) and corrected distance visual acuity (CDVA) of 20/40 or better. Lenticule parameters were 6.3- to 6.7-mm diameter, 2-mm transition zone, 30-µm minimum thickness, and 120-µm cap thickness. Standard outcomes analysis was performed for the 3-month data, including contrast sensitivity using the Functional Vision Analyzer. For 93 eyes treated, 3-month data were available for 82 (88%). Attempted spherical equivalent refraction was +5.62 ± 1.20 D (range: +1.00 to +6.90 D) and cylinder was -0.91 ± 0.68 D (range: 0.00 to -3.50 D). For eyes targeted for emmetropia (n = 36), uncorrected distance visual acuity was 20/40 or better in 89%. Spherical equivalent refraction relative to target was -0.17 ± 0.85 D (range: -2.20 to +3.00 D), with 59% within ±0.50 D and 76% within ±1.00 D. There was one line loss of CDVA in 17% of eyes, and one eye lost three lines (1.2%) but recovered to one line lost at 9 months. There was no clinically significant change in contrast sensitivity. Refractive and visual outcomes 3 months after SMILE for hyperopia were promising, given the high degree of hyperopia corrected and relatively reduced CDVA in this population. Undercorrection of more than 1.00 D in 5 eyes might be partly explained by latent hyperopia in these young patients. [J Refract Surg. 2019;35(1):24-30.].

Higher-Order-Aberrations Following Hyperopia Treatment: Small Incision Lenticule Extraction, Laser-Assisted In Situ Keratomileusis and Lenticule Implantation

PurposeTo compare the postoperative higher-order-aberrations (HOAs) after hyperopic small incision lenticule extraction (SMILE), hyperopic laser-assisted in situ keratomileusis (LASIK), and lenticule implantation for correction of hyperopia.MethodsEighteen monkeys were divided to six groups: +2.00 D and +4.00 D hyperopic SMILE, +2.00 D and +4.00 D hyperopic LASIK (n = 6 eyes for each), and lenticule implantation with a −2.00 D and −4.00 D lenticule (n = 3 eyes for each). The corneal HOAs were evaluated preoperatively and 3-month postoperatively.ResultsAt 3-month postoperatively, the spherical aberrations significantly increased toward negative direction in all +4.00 D groups (all P < 0.05). There was a significant change toward more negative values in the third-order vertical coma in the SMILE +4.00 D and LASIK +4.00 D groups (P = 0.026 and P = 0.036, respectively). There were also significant changes in the third-order horizontal trefoil (P = 0.034) and oblique secondary astigmatism (P = 0.012) in the LASIK +4.00 D group. In the eyes that underwent +4.00 D lenticule implantation, the fourth-order horizontal quatrefoil significantly increased (P = 0.029). In low hyperopia correction (+2.00 D), treatment with lenticule implantation tended to have less changes in HOAs, compared to the other two groups.ConclusionsIn hyperopic SMILE, hyperopic LASIK or lenticule implantation surgery, significant induction of third- and fourth-order HOAs were seen in moderate hyperopia correction but not in low hyperopia correction. In low hyperopia treatment, lenticule implantation might offer a favorable trend in the aspect of HOAs.Translational RelevanceThe results provided the knowledge of surgically induced HOAs and understanding of the effects of surgery in different types of hyperopic correction.

Small Incision Lenticule Extraction (SMILE) for Hyperopia: Optical Zone Centration.

To evaluate optical zone centration of hyperopic small incision lenticule extraction (SMILE). This prospective study of 60 consecutive hyperopic SMILE procedures used the VisuMax femtosecond laser and matched LASIK procedures with the VisuMax and MEL 80 excimer lasers (Carl Zeiss Meditec AG, Jena, Germany). Inclusion criteria were maximum attempted hyperopic meridian of between +1.00 and +7.00 diopters (D) and astigmatism up to 6.00 D. For SMILE, the optical zone was between 6.3 and 6.7 mm, with a 2-mm transition zone. Two LASIK control groups (6.5- and 7-mm optical zone) were generated matched for spherical equivalent treated. In SMILE, the corneal vertex of the coaxially fixating eye was aligned with the vertex of the curved contact glass. In LASIK, the treatment was centered on the coaxially sighted corneal light reflex (first Purkinje image) with the contralateral eye (Seiler method). A tangential (instantaneous) curvature preoperative to 3 months postoperative difference map was generated for each eye. A fixed grid and set of concentric circles were superimposed on the difference map to measure the offset between the optical zone center and corneal vertex (0,0), and vector analysis was used for comparative analysis. Mean attempted spherical equivalent was +5.61 ± 0.96 D (range: +3.20 to +6.50 D) and mean cylinder was -0.96 ± 0.62 D (range: 0.00 to -2.75 D) in the SMILE group. Mean age was 29 ± 7 years (range: 19 to 52 years) in the SMILE group. Mean centration offset was 0.23 ± 0.15 mm (range: 0 to 0.61 mm) for the SMILE group, 0.33 ± 0.14 mm (range: 0.14 to 0.85 mm) for the 6.5-mm LASIK group, and 0.31 ± 0.19 mm (range: 0.05 to 0.85 mm) for the 7-mm LASIK group. The mean centration offset for SMILE was less than that of both LASIK groups (P < .05). Optical zone centration of hyperopic SMILE was found to be similar to eye-tracker-centered hyperopic LASIK with the MEL 80 laser. [J Refract Surg. 2017;33(3):150-156.].