A-Yong Yu

Efficacy Comparison of 16 Interventions for Myopia Control in Children: A Network Meta-analysis

PURPOSE To determine the effectiveness of different interventions to slow down the progression of myopia in children. METHODS We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov from inception to August 2014. We selected randomized controlled trials (RCTs) involving interventions for controlling the progression of myopia in children with a treatment duration of at least 1 year for analysis. MAIN OUTCOME MEASURES The primary outcomes were mean annual change in refraction (diopters/year) and mean annual change in axial length (millimeters/year). RESULTS Thirty RCTs (involving 5422 eyes) were identified. Network meta-analysis showed that in comparison with placebo or single vision spectacle lenses, high-dose atropine (refraction change: 0.68 [0.52-0.84]; axial length change: -0.21 [-0.28 to -0.16]), moderate-dose atropine (refraction change: 0.53 [0.28-0.77]; axial length change: -0.21 [-0.32 to -0.12]), and low-dose atropine (refraction change: 0.53 [0.21-0.85]; axial length change: -0.15 [-0.25 to -0.05]) markedly slowed myopia progression. Pirenzepine (refraction change: 0.29 [0.05-0.52]; axial length change: -0.09 [-0.17 to -0.01]), orthokeratology (axial length change: -0.15 [-0.22 to -0.08]), and peripheral defocus modifying contact lenses (axial length change: -0.11 [-0.20 to -0.03]) showed moderate effects. Progressive addition spectacle lenses (refraction change: 0.14 [0.02-0.26]; axial length change: -0.04 [-0.09 to -0.01]) showed slight effects. CONCLUSIONS This network analysis indicates that a range of interventions can significantly reduce myopia progression when compared with single vision spectacle lenses or placebo. In terms of refraction, atropine, pirenzepine, and progressive addition spectacle lenses were effective. In terms of axial length, atropine, orthokeratology, peripheral defocus modifying contact lenses, pirenzepine, and progressive addition spectacle lenses were effective. The most effective interventions were pharmacologic, that is, muscarinic antagonists such as atropine and pirenzepine. Certain specially designed contact lenses, including orthokeratology and peripheral defocus modifying contact lenses, had moderate effects, whereas specially designed spectacle lenses showed minimal effect.

A Comprehensive Comparison of Central Corneal Thickness Measurement

Purpose. To assess the repeatability and reproducibility of central corneal thickness (CCT) measurements by high-resolution rotating Scheimpflug imaging (Pentacam, Oculus) and Fourier-domain optical coherence tomography (RTvue-100, Optovue) after laser in situ keratomileusis (LASIK) and to compare the agreement with ultrasound pachymetry (USP). Methods. Forty-seven eyes of 47 patients after LASIK were included in the study. The first examiner took two successive Pentacam and RTvue CCT measurements, and this was repeated once again by the second examiner to assess intraobserver and interobserver repeatability and reproducibility. After performing non-contact examinations, the corneas were measured by USP to compare the level of agreement among the three devices. Results. All Pentacamcenter, Pentacamapex, Pentacamthinnest, and RTvue CCT measurements demonstrated high intraobserver repeatability, with respective precision (1.96 within-subject standard deviation) and intraclass correlation coefficients of 7.52, 7.43, 7.55, and 3.81 &mgr;m and 0.985, 0.986, 0.986, and 0.997; interobserver repeatability results were similar. All coefficients of variation were low: <1% for all measures. Compared with Pentacam and USP measurements, the RTvue measurement significantly underestimated CCT by a mean of 10.52 to 15.28 &mgr;m (p < 0.001) and 9.17 &mgr;m (p < 0.001), respectively. The agreement of USP with Pentacam and RTvue by Bland-Altman analysis spanned over 30 &mgr;m. The agreement of Pentacam with RTvue spanned approximate 20 &mgr;m. Conclusions. Both Pentacam imaging and RTvue Fourier-domain optical coherence tomography provide reliable and interchangeable measurement of CCT in post-LASIK corneas. However, they cannot be considered to be clinically interchangeable with USP.

Clinical investigation of off-flap epi-LASIK for moderate to high myopia.

PURPOSE To compare the clinical outcome of on-flap and off-flap epi-LASIK for moderate to high myopia. METHODS This prospective, observer-masked, randomized study included 62 eyes of 31 patients with myopia who underwent off-flap epi-LASIK (epikeratome; Moria, Antony, France) in one eye (off-flap group) and on-flap epi-LASIK in the contralateral eye (on-flap group). Corneal ablation was performed with a commercially available laser (Mel-80; Carl Zeiss Meditec, Oberkochen, Germany). Patients were seen at 3, 5, and 12 days and 1 and 3 months after surgery. Clinical outcomes were compared between groups. RESULTS No significant between-group differences in the mean preoperative spherical equivalent (-6.18 +/- 1.29 D vs. -6.47 +/- 1.70 D), the change in lines of best corrected visual acuity at 3 months after surgery, and postoperative pain were found. Compared with the on-flap group, outcomes of better uncorrected visual acuity at 3 and 5 days after surgery (P < 0.001), rapider reepithelialization (P < 0.001), and lower level of haze at 1 and 3 months after surgery (P = 0.04, 0.04) were found in the off-flap group. Three months after surgery, contrast sensitivity function (CSF), with and without glare, did not differ from before surgery in both groups (P > 0.05) except CSF at 18 cpd with glare increased significantly in the off-flap group 3 months after surgery (P = 0.04). Wavefront aberration increased significantly from baseline in both groups 3 months after surgery (P < 0.05). The on-flap group revealed greater but insignificant increasing amplitude in wavefront aberration compared with the off-flap group. CONCLUSIONS In comparison with on-flap epi-LASIK, off-flap epi-LASIK offers comparable postoperative pain, a lower level of haze formation, a rapider visual recovery, and better visual quality. Further investigations of a larger number of subjects and longer follow-up periods are warranted.

Evaluation of the relationship of corneal biomechanical metrics with physical intraocular pressure and central corneal thickness in ex vivo rabbit eye globes

The relationship of corneal biomechanical metrics provided by the Ocular Response Analyzer (ORA) and Corvis ST (CVS) with physical intraocular pressure (IOPp) and central corneal thickness (CCT) was evaluated. Thirty fresh enucleated eyes of 30 rabbits were used in ex vivo whole globe inflation experiments. IOPp was measured with a pressure transducer and increased from 7.5 to 37.5 mmHg in steps of 7.5 mmHg while biomechanical data was acquired using the ORA and CVS. At least 3 examinations were performed at each pressure level, where CCT and twelve biomechanical metrics were recorded and analyzed as a function of IOPp. The biomechanical metrics included corneal hysteresis (CH) and corneal resistance factor (CRF), obtained by the ORA. They also included the applanation times (A1T, A2T), lengths (A1L, A2L) and velocities (A1V, A2V), in addition to the highest concavity time (HCT), peak distance (PD), radius (HR) and deformation amplitude (DA), obtained by the CVS. The variation of CCT and the twelve biomechanical metrics for the 30 rabbit eyes tested across the 5 pressure stages considered (inter-pressure differences) were statistically significant (P = 0.00). IOPp was highly to moderately correlated with most biomechanical metrics, especially CRF, A1T, A1V, A2V, PD and DA, while the relationships with CH, A2T, A1L and HCT were poor. IOP has important influences on most corneal biomechanical metrics provided by CVS and ORA. Two biomechanical metrics A1V and HR were influenced by CCT after correcting for the effect of IOP in most pressure stages, while the correlation with others were weak. Comparisons of research groups based on ORA and CVS with different IOPs and CCTs may lead to possible misinterpretations if both or one of which are not considered in the analysis.

Correlation between corneal biomechanical properties, applanation tonometry and direct intracameral tonometry

Aim To investigate the correlation between corneal biomechanical properties, applanation tonometry and direct intracameral tonometry. Methods Patients scheduled for phacoemulsification were enrolled in this prospective observer-masked study. Central corneal thickness (CCT) was obtained with ultrasound pachymetry. Corneal biomechanical properties including corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with the ocular response analyser. Applanation intraocular pressure (IOP) (IOPappla) was measured in the supine position. Intracameral IOP (IOPintra) was measured with a pressure transducer connected to a cannula inserted into the anterior chamber. Results Fifty-eight eyes of 58 patients were included. There was a significant difference between IOPappla and IOPintra (17.3±4.1 vs 13.8±4.7 mm Hg, p<0.001). CCT was significantly correlated with CH and CRF (p<0.01). Univariate regression analysis revealed IOPappla was significantly correlated with CCT and CRF (p<0.05). IOPintra had no significant association with the corneal properties (p>0.05). Multivariate regression analysis revealed IOPappla=10.43+2.69CRF–1.99CH (p<0.001) and the difference between IOPappla and IOPintra (ΔIOP)=−1.57+0.55CRF (p=0.032). Conclusion The mean difference between IOPappla and IOPintra was 3.5 mm Hg. While IOPappla was correlated with the corneal biomechanical properties of CH and CRF, IOPintra was not. IOPappla was correlated more with the corneal biomechanical properties assessed by the ocular response analyser than with CCT alone.

Correlation Among Lens Opacities Classification System III Grading, Visual Function Index-14, Pentacam Nucleus Staging, and Objective Scatter Index for Cataract Assessment

PURPOSE To investigate the relationship among Lens Opacities Classification System III (LOCS III) grading score, Visual Function Index-14 (VF-14) score, average lens density by the Pentacam Nucleus Staging system, and the objective scatter index measured by the Optical Quality Analysis System in age-related cataract patients. DESIGN Prospective, single-center, cross-sectional study. METHODS Thirty-six subjects (60 eyes) with age-related cataract were recruited. Subjects with any corneal anomaly potentially affecting intraocular scatter were excluded. The best-corrected visual acuity (BCVA), LOCS III nuclear opalescence score and cortical cataract score, VF-14 score, average lens density, and objective scatter index were obtained. Correlations among these parameters were analyzed. RESULTS The LOCS III nuclear opalescence score was correlated with the BCVA (r = 0.438; P = .001), objective scatter index (r = 0.543; P < .001), and average lens density (r = 0.621; P < .001). The objective scatter index was also correlated with the BCVA (r = 0.779; P < .001) and the average lens density (r = 0.320; P = .013). The VF-14 score had the strongest correlation with the objective scatter index (r = -0.712; P < .001). The difference between groups with objective scatter index<3.0 and ≥3.0 was significant with regard to BCVA, average lens density, LOCS III nuclear opalescence score, and VF-14 score. CONCLUSIONS LOCS III grading remains an economical and effective method to assess lens opacities, especially in the formation of early cortex cataracts. The objective scatter index can be a useful parameter to objectively analyze the correlation between ocular examination findings and patient concerns. Furthermore, the objective scatter index scores ≥3.0 can be a possible objective cut-off for preoperative decision making.

Repeatability and Reproducibility of a Double-Pass Optical Quality Analysis Device

Purpose To evaluate the repeatability and reproducibility of a double-pass instrument (OQASII, Visiomereics SL, Spain), which objectively measures overall optical quality of the human eyes. Methods The right eye of 119 healthy subjects with best corrected visual acuity of 20/25 or better was included in this prospective, comparative, observational study. Two separate tests with OQASII were conducted sequentially on the same day by two different examiners. A week later, the first examiner conducted the third measurement. All subjects underwent three consecutive tests during each session. The repeatability and reproducibility of the modulation transfer function cut off frequency (MTF cutoff), the Strehl ratio, the OQAS values (OVs) at contrasts of 100%, 20% and 9%, and the objective scatter index (OSI) were analyzed. Results For MTF cutoff, Strehl ratio, OV100%, OV20%, OV9%, and OSI, the mean values were 39.32±9.75cpd, 0.22±0.06, 1.31±0.33, 1.33±0.39, 1.33±0.41, 0.60±0.42, respectively. Repeatability and reproducibility were good with a very low coefficient of variation and high interclass correlation coefficients (>0.88) for all parameters. Bland-Altman plots showed good correlation with 95% limits of agreement ranged from -6.04 to 6.78cpd, -0.05 to 0.05, -0.20 to 0.23, -0.29 to 0.32, -0.40 to 0.42, -0.23 to 0.21 in inter-observer, and -6.56 to 7.42cpd, -0.06 to 0.06, -0.22 to 0.24, -0.30 to 0.32, -0.35 to 0.34, -0.24 to 0.23 in inter-visit, respectively. Conclusion The OQASII system yields excellent repeatability and good reproducibility for objective measurements of overall optical quality in clinic.

Axial Length Measurement Failure Rates with the IOLMaster and Lenstar LS 900 in Eyes with Cataract

Purpose To evaluate axial length (AL) measurement failure rate with the IOLMaster (Carl Zeiss AG, Germany) and Lenstar LS 900 (Haag-Streit AG, Switzerland) in eyes with cataract. Methods Two hundred and ninety-six eyes of 170 patients with cataract were enrolled. Cataract type and severity were graded using the Lens Opacities Classification System III (LOCS III) and AL measurements were attempted with IOLMaster (version 5.4) and Lenstar LS 900 (version 1.1). Chi-squared analysis was used to assess if the difference in AL measurement acquisition rate was statistically significant between the two devices. The association of the different cataract types and severity with the AL measurement acquisition rate was evaluated with logistic regression analysis. Results AL measurements were obtained in 184 eyes (62.16%) using the IOLMaster and 191 eyes (64.53%) using the Lenstar, which corresponds to a failure rate of 37.84% and 35.47% respectively. Chi-square analysis indicated no significant difference between the Lenstar and IOLMaster for AL measurement failure rate (x2 = 0.356, P = 0.550). Logistic regression analysis indicated no association between acquisition rates and cortical or nuclear cataracts with either device. There was a statistically significant association between acquisition rates and increasing severity of posterior subcapsular cataracts with the IOLMaster (β = -1.491, P<0.001) and Lenstar LS 900 (β = -1.507, P<0.001). Conclusion The IOLMaster and Lenstar LS 900 have similar AL measurement failure rates (35–38%) for Chinese public hospital cataract patients. Increasing severity of posterior subcapsular cataracts was problematic for both devices.

Biometry of the Cornea in Myopic Chinese Patients

PURPOSE To develop a close-fit mathematical model of corneal anterior and posterior topography and investigate the variation of corneal topography with biometric parameters in a group of young adult myopic Chinese patients. METHODS Corneal topography data were acquired from 112 eyes of 61 myopic patients (mean age: 24.10±3.66 years). Videokeratoscopic images were recorded for anterior and posterior corneal surfaces using an Orbscan IIz topography system (Bausch & Lomb), and elevation data were fit to ellipsoid, hyperboloid, and paraboloid equations. Axial length, anterior chamber depth, refractive error, corneal curvature, central corneal thickness, and white-to-white distance were also measured and statistically analyzed. RESULTS The ellipsoid equation provided the best fit for the anterior and posterior corneal surfaces in all patients. Corneal asymmetry slightly improved the accuracy of the mathematical model and reduced errors of fit with the clinical data. Strong evidence of right and left corneal symmetry was obtained in the form of similar corneal curvature, shape factor, and thickness values. The refractive error showed strong correlation with axial length (r=-0.586, P<.001) but not with corneal curvature or anterior chamber depth, indicating that myopia may be related to scleral stretching and globe elongation rather than changes in corneal curvature or anterior chamber depth. CONCLUSIONS Axial length appears to be the main morphological parameter related to myopia. Myopic corneas took the form of a rotationally asymmetric prolate ellipsoid that gradually flattened towards the periphery. The study also provided evidence of symmetry between an individuals right and left corneas.

Preliminary clinical investigation of cataract surgery with a noncontact femtosecond laser system

Femtosecond laser‐assisted cataract surgery (FLACS) is rapidly gaining popularity due to the improved consistency and predictability for capsulorhexis. This study aimed to investigate the preliminary clinical outcomes of FLACS with a noncontact femtosecond laser system.