Huamao Miao

Mild decentration measured by a Scheimpflug camera and its impact on visual quality following SMILE in the early learning curve.

PURPOSE To measure decentration following femtosecond laser small incision lenticule extraction (SMILE) for the correction of myopia and myopic astigmatism in the early learning curve, and to investigate its impact on visual quality. METHODS A total of 55 consecutive patients (100 eyes) who underwent the SMILE procedure were included. Decentration was measured using a Scheimpflug camera 6 months after surgery. Uncorrected and corrected distance visual acuity (UDVA, CDVA), manifest refraction, and wavefront errors were also measured. Associations between decentration and the preoperative spherical equivalent were analyzed, as well as the associations between decentration and wavefront aberrations. RESULTS Regarding efficacy and safety, 40 eyes (40%) had an unchanged CDVA; 32 eyes (32%) gained one line; and 11 eyes (11%) gained two lines. Fifteen eyes (15%) lost one line of CDVA, and two eyes (2%) lost two lines. Ninety-nine of the treated eyes (99%) had a postoperative UDVA better than 1.0, and 100 eyes (100%) had a UDVA better than 0.8. The mean decentered displacement was 0.17 ± 0.09 mm. The decentered displacement of all treated eyes (100%) was within 0.50 mm; 70 eyes (70%) were within 0.20 mm; and 90 eyes (90%) were within 0.30 mm. The vertical coma showed the greatest increase in magnitude. The magnitude of horizontal decentration was found to be associated with an induced horizontal coma. CONCLUSIONS This study suggests that, although mild decentration occurred in the early learning curve, good visual outcomes were achieved after the SMILE surgery. Special efforts to minimize induced vertical coma are necessary.

Diffuse lamellar keratitis after small-incision lenticule extraction

Purpose To determine the incidence and clinical features of diffuse lamellar keratitis (DLK) after small‐incision lenticule extraction (SMILE). Setting Department of Ophthalmology, Eye and ENT Hospital of Fudan University, Shanghai, China. Design Retrospective case control study. Methods Small‐incision lenticule extraction for myopia was performed from September 1, 2011, to October 31, 2013. Preoperative clinical characteristics; treatment parameters; and intraoperative and postoperative complications, including the incidence, severity, clinical outcome, and resolution of DLK, were recorded. The independent t test, chi‐square test, univariate repeated measures, and multivariate linear regression analysis were used to make statistical comparisons between eyes that developed DLK and those that did not. Results The study enrolled 1112 eyes (590 patients). Eighteen eyes (1.6%) (11 patients) developed DLK. These patients presented 1 to 3 days postoperatively with mild to moderate inflammation. Thirteen eyes (72.2%) had stage 1 DLK, 4 (22.2%) had stage 2, and 1 (5.6%) had stage 3. After intensive treatment with topical corticosteroids, the stage 1 and stage 2 cases resolved within 3 weeks and the stage 3 case resolved in 1 month. The postoperative corrected distance visual acuity was the same or better than preoperatively in all eyes. There was a statistically significant increase in the incidence of DLK with thinner lenticules (P = .02) and larger diameter lenticules (P = .01), although multifactorial analysis showed lenticule thickness to be the only factor (P = .03). Conclusions Diffuse lamellar keratitis is a potential complication after small‐incision lenticule extraction, although it had a low incidence. The risk factors for DLK must be further elucidated. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Changes in Corneal Deformation Parameters after Lenticule Creation and Extraction during Small Incision Lenticule Extraction (SMILE) Procedure

Purpose To investigate the effects of lenticule creation and subsequent corneal lenticule extraction on corneal deformation parameters during small incision lenticule extraction (SMILE) procedure. Materials and Methods In this prospective study, 18 eyes of 10 patients (27.90±7.11 years, −5.64±2.45 diopters) scheduled for SMILE procedure were enrolled. Changes in the corneal deformation parameters, including deformation amplitude (DA), applanation time(AT1 and AT2), applanation length(AL1 and AL2), corneal velocity(CV1 and CV2), peak distance(P.Dist.), radius and intraocular pressure values were measured preoperatively, immediately after lenticule creation and subsequent to corneal lenticule extraction in all eyes with the Corvis Scheimpflug Technology (Corvis ST, OCULUS, Wetzlar, Germany). Repeated measures analysis of variance (ANOVA) with bonferroni-adjusted post hoc comparisons was performed to investigate changes following each step of the procedure. Results All surgical procedures were uneventful. A significant difference was detected among the three time points (pre-operation, post-lenticule creation and post lenticule extraction) for AT1 (P<0.001), AT2 (P = 0.001), DA(P<0.001), and IOP(P = 0.002). Bonferroni-adjusted post hoc comparisons indicated that there was no significant change in AT1, AT2, DA, or IOP after lenticule creation (post hoc P>0.05), but there was a significant change in these parameters following subsequent corneal lenticule extraction (post hoc P<0.01), when compared to values obtained pre-operatively. The scheimpflug camera of the Corvis ST demonstrated the intralamellar small gas bubbles formed from the vaporisation of tissue after lenticule creation and a gray zone was observed between the cap and the residual stromal bed after lenticule extraction. Conclusions There is a significant change in corneal deformation parameters following SMILE procedure. The changes may be caused predominantly by stromal lenticule extraction, while lenticule creation with femtosecond laser may not have an obvious effect on corneal deformation properties.

Optical Quality and Intraocular Scattering After Femtosecond Laser Small Incision Lenticule Extraction

PURPOSE To investigate objective optical quality and changes in light scatter after femtosecond laser small incision lenticule extraction (SMILE) for moderate to high myopia correction. METHODS Prospective clinical study of 66 eyes of 66 patients (23 males, 43 females) with a mean age of 28.67 ± 6.62 years, mean spherical refraction of -6.06 ± 1.57 diopters, and mean cylindrical refraction of -0.68 ± 0.46 diopters. Every patient had a 3-month follow-up after a standard SMILE procedure. An optical quality analysis system was used to measure modulation transfer function cutoff frequency (MTFcutoff), Strehl2D ratio, and objective scatter index (OSI). RESULTS At 3 months postoperatively, mean spherical equivalent was 0.03 ± 0.24 diopters and corrected distance visual acuities of all patients were equal to or better than preoperative values, with a mean safety index of 1.12 ± 0.17 (range: 0.80 to 1.50) and mean efficacy index of 1.18 ± 0.21 (range: 0.80 to 1.50). Mean OSI increased from 0.75 preoperatively to 1.09 at 20 days postoperatively (P < .05), and gradually declined to 0.94 at 40 days and 0.82 at 3 months postoperatively (P > .05). MTFcutoff and Strehl2D ratio did not change significantly compared with preoperative values (P > .05). Multiple linear regression analysis revealed that preoperative OSI was significantly correlated with optical quality at 3 months. Patients with less preoperative OSI tended to acquire higher MTFcutoff (b = -8.61) and lower OSI (b = 0.65) (P < .05). CONCLUSIONS SMILE had little impact on retinal image quality after myopia correction. Postoperative OSI showed a temporary increase and then returned to normal.

Visual Outcomes and Optical Quality After Femtosecond Laser Small Incision Lenticule Extraction: An 18-Month Prospective Study

PURPOSE To investigate the long-term visual outcomes and optical quality after femtosecond laser small incision lenticule extraction (SMILE) for moderate to high myopia correction. METHODS Fifty-four patients (37 women, 17 men) who underwent SMILE were enrolled in this prospective clinical study. Patient ages ranged from 18 to 40 years, with a mean spherical equivalent of -6.50 ± 1.64 diopters. Data including refractive parameters, retinal image quality, intraocular scattering, and aberrations were collected at 6 and 18 months after surgery. Patient satisfaction was also evaluated. RESULTS At 18 months after surgery, both the mean safety index and the efficacy index were 1.23 ± 0.23 (range: 0.80 to 1.50); there was no significant difference with indices measured at 6 months (P > .05). No patient lost two or more lines of corrected distance visual acuity. Total higher-order aberrations (HOAs) and coma significantly increased after SMILE (P < .05), whereas total spherical aberrations and trefoil changed only slightly. The mean modulation transfer function cutoff frequency was 36.66 ± 8.54 cycles per degree (cpd) before surgery and 37.81 ± 6.89 cpd at 18 months postoperatively; the mean objective scatter index was 0.62 ± 0.33 before surgery and 0.71 ± 0.38 at 18 months postoperatively. No significant difference was found between the three time points (P > .05). Mean patient satisfaction was 9.31 ± 0.64 (with a maximum score of 10). CONCLUSIONS SMILE showed good safety, efficacy, and stability in correcting moderate to high myopia, and patients were highly satisfied. HOAs increased after SMILE, mainly due to the increase of coma, whereas retinal image quality and intraocular scattering barely changed.

Objective optical quality and intraocular scattering in myopic adults.

PURPOSE To evaluate objective optical quality and intraocular scattering in adults with myopia. METHODS This was a cross-sectional study. Patients between 18 and 40 years of age were recruited from those undergoing routine preoperative examinations prior to myopic refractive surgery. The spherical equivalent refraction (SE) ranged from -14.25 to -0.63 diopters (D). Right eyes of 274 subjects were included for factor analyses: 25 eyes were super-high myopia (SE < -9 D), 88 eyes were high myopia (-6 D > SE ≥ -9 D),133 eyes were moderate myopia (-3 D > SE ≥ -6 D), and 28 eyes were low myopia (SE ≥ -3 D). A double-pass system was used to measure the modulation transfer function cutoff frequency (MTFcutoff) and objective scatter index (OSI). RESULTS Mean MTFcutoff was 32.38 ± 9.73 and 27.61 ± 8.11 cycles per degree (cyc/deg) in the high and super-high myopia groups, significantly lower than 39.92 ± 10.53 and 37.39 ± 8.74 cyc/deg in the low and moderate groups (P < 0.01). Mean OSI was 0.89 ± 0.61 and 1.33 ± 0.65 in the high and super-high myopia groups, significantly higher than in the low and moderate groups, 0.50 ± 0.39 and 0.57 ± 0.44 (P < 0.01). No significant difference was found between the low myopia and the moderate myopia group in any of the parameters (P > 0.05). Other factors such as eye side, sex, and age did not significantly affect optical quality parameters or OSI in this study population (P > 0.05). CONCLUSIONS Optical quality and intraocular scattering varied among individuals with myopia. High myopia has more influence on retinal image quality and scattering than moderate and low myopia. Our study also helps to establish MTFcutoff and OSI standards for Chinese refractive surgery candidates.

Enhancement of femtosecond lenticule extraction for visual symptomatic eye after myopia correction

BackgroundThe novel Femtosecond lenticule extraction (FLEx) procedure has been considered safe, predictable, and effective in treating myopia and myopic astigmatism, with few complications. However, an enhancement procedure after FLEx may be required in some cases, but has not been reported in detail.Case presentationA 24-year-old woman who had undergone bilateral FLEx with the VisuMax femtosecond laser treatment for myopic astigmatism complained of double vision in her left eye after the operation. The manifest refraction was −0.50/-1.25 × 180°. The corneal topography showed a central-inferior steepened zone. The ocular wavefront measurements displayed a high value of total aberrations as well as coma. She was scheduled for an enhancement procedure and it was performed by relifting the primary FLEx flap in the left eye four months later. Ablation was made with the Mel-80 excimer laser. After retreatment, the corresponding aberrations were diminished and the corneal topography turned flattened. Her symptom resolved completely with good visual outcomes.ConclusionThis first detailed case report demonstrates the feasibility and efficacy of enhancement after FLEx for visual symptomatic eye after myopia correction. An analysis of more cases would be necessary to determine a more definite profile.

Central and Peripheral Corneal Power Change in Myopic Orthokeratology and Its Relationship With 2-Year Axial Length Change.

PURPOSE We assessed the relationship between axial length (AL) change and corneal refractive power change induced by orthokeratology (ortho-k) contact lens wear. METHODS A total of 88 myopic children aged 7 to 12 years were fitted with ortho-k lenses for overnight wear. Axial length was measured before enrollment and every 6 months after initiation of lens wear up to 24 months. Corneal apical refractive power and the mean power of each concentric ring from 0.5 to 7.2 mm in diameter at 0.1-mm intervals were measured using the Pentacam HR, and compared before and after 3 months of ortho-k lens wear. Summed corneal power change (SCPC) was defined as the sum of relative corneal power change within the central 7.2-mm diameter corneal region. Age, baseline spherical equivalent refractive error (SERE), and SCPC were tested against 2-year AL growth in a stepwise multiple linear regression model. RESULTS Of the 88 myopic children who were successfully fitted with ortho-k lenses, 64 completed the 2-year follow-up period. These completed test subjects experienced a mean axial growth of 0.37 ± 0.27 mm. Spherical equivalent refractive error and corneal apical refractive power decreased from baseline values of -2.88 ± 0.96 diopters (D) and 43.47 ± 1.03 D to -0.20 ± 0.85 D and 40.61 ± 1.23 D, respectively, after 3 months of lens wear. The mean SCPC was 10.84 ± 5.28 D · mm after 3 months. Axial elongation was significantly correlated with SCPC (standardized β = -0.573, P < 0.001) and baseline age (standardized β = -0.403, P < 0.001), but not with baseline SERE (β = 0.081, P = 0.396). The regression model using SCPC and baseline age to predict axial elongation was acceptable (adjusted R2 = 0.56) and statistically significant (F2,61 = 41.09, P < 0.001). CONCLUSIONS Axial elongation in children undergoing ortho-k therapy is negatively correlated with the age of the wearer and summed corneal power change from the central to the mid-peripheral cornea. We speculate that axial elongation is influenced by the extent to which the retinal defocus profile is altered with ortho-k lens wear. (http://www.chictr.org number, ChiCTR-TNRC-11001210.).

A Pilot Study of SMILE for Hyperopia: Corneal Morphology and Surface Characteristics of Concave Lenticules in Human Donor Eyes.

PURPOSE To evaluate the corneal morphology and surface characteristics of concave lenticules after small incision lenticule extraction (SMILE) for hyperopia. METHODS SMILE procedures were performed on two human autopsy corneas in vitro to correct +4.00 diopters of hyperopia. Slit-lamp microscopy and anterior optical coherence tomography (OCT) were performed after lenticule creation and extraction. The extracted lenticules and modified corneas were sent for transmission electron microscopy imaging. RESULTS Interlamellar gas bubbles were detected at 3 minutes and almost burst at 30 minutes after lenticule creation. A few interlamellar bubbles were detected after lenticule extraction. There was an obvious interlamellar concave gap under OCT. Transmission electron microscopy showed the front and back surfaces of the lenticules were smooth, with some tissue bridges, cavities, and grooves. CONCLUSIONS A good quality concave lenticule can be created via SMILE for hyperopia. The impact of interlamellar gap on visual quality needs further investigation. [J Refract Surg. 2016;32(10):713-716.].

Intra- and Intersession Repeatability of an Optical Quality and Intraocular Scattering Measurement System in Children

Purpose To evaluate intra- and intersession repeatability of objective optical quality and intraocular scattering measurements with a double-pass system in children. Methods Forty-two eyes of 42 children were included in the study. An optical quality analysis system (OQAS) was used to measure optical quality parameters, including modulation transfer function cutoff frequency (MTFcutoff), Strehl ratio (SR), OQAS values (OV) at 3 different contrasts and objective scatter index (OSI). Three measurement sessions with 10-min intervals were operated by the same technician, and in each session four consecutive measurements were obtained. Results Mean values for MTFcutoff, SR and OSI were 46.85 ± 7.45cpd, 0.27 ± 0.06 and 0.34 ± 0.22 respectively. 1) The intraclass correlation coefficients were ranged from 0.89 to 0.97 and coefficients of variation from 0.06 to 0.16 for all the parameters in the first session; the relative repeatability were 11.1% (MTFcutoff), 22.5% (SR), 10.9% (OV100%), 16.6% (OV2%), 22.4% (OV9%) and 56.3% (OSI). Similar results were found in the second and third sessions. 2) Bland-Altman analysis showed that narrow 95% confidence intervals (compared between the first and second sessions) ranged from -5.42 to 5.28 (MTFcutoff), -0.05 to 0.07 (SR), -0.18 to 0.18 (OV100%), -0.26 to 0.29 (OV20%), -0.33 to 0.39 (OV9%) and -0.11 to 0.09 (OSI); the comparison between any two of the three sessions showed similar results. Conclusion Measurements of optical quality and intraocular scattering in children by the double-pass system showed good intra- and intersession repeatability. Retinal image quality is high and intraocular scattering is low in children.