Astigmatism Influences Quantitative and Qualitative Analysis in Optical Coherence Tomography Angiography Imaging.

Purpose: The purpose of this paper was to study the influence of astigmatism in optical coherence tomography angiography (OCTA) images in a quantitative and qualitative analysis. Methods: This was a prospective, cross-sectional study. We included 110 eyes of 110 patients: 20 eyes without astigmatism and 90 eyes with astigmatism ≥0.5 diopters (D). We performed a macula centered OCTA as a reference image. In patients without astigmatism, registered follow-up scans were performed after induction of -1 and -2 D astigmatism. In patients with astigmatism, we performed the follow-up scan after astigmatism correction. We used a set of cylindrical lenses attached to the camera head of the SPECTRALIS (Heidelberg Engineering, Heidelberg, Germany). A quantitative and qualitative analysis of the superficial vascular complex (SVC) and deep vascular complex (DVC) was performed. The main outcome measures were vessel density (VD), image quality, and the presence of artifacts. Results: Mean VD of the SVC was significantly higher in the reference images compared with the images after induction of -2 D. Differences with -1 D were nonsignificant. Higher degrees of astigmatisms had higher VD dropout (0.012-0.02 per diopter in SVC). Astigmatism axis showed no relevance in our cohort. Image quality assessed by two independent observers was graded as higher in images without astigmatism. Defocus and attenuation were more prevalent in images with astigmatism. Conclusions: Astigmatism of -2 D affects quantification of VD in OCTA images, mainly affecting the SVC, as well as the subjective quality assessment. Correction of this refractive error might be necessary for an accurate quantitative assessment of OCTA images. Translational Relevance: Correcting astigmatism of 2 D or greater appears to be necessary when analyzing OCTA images.

Regular and irregular astigmatism of bullous keratopathy using Fourier harmonic analysis with anterior segment optical coherence tomography.

Bullous keratopathy (BK) is known to present with corneal edema and Descemet's folds, which can cause corneal astigmatism. However, no report quantitatively evaluated BK astigmatism by separating it into regular and irregular astigmatism. This study investigated the regular and irregular astigmatism of the anterior and posterior corneal surface with Fourier harmonic analysis and anterior segment optical coherence tomography. Preoperative data from 43 eyes of 41 BK patients who received corneal endothelial transplantation were compared with the data from 43 eyes of 43 subjects without corneal disease. Anterior and posterior cylinder power, central corneal thickness (CCT) and thinnest corneal thickness were significantly greater in BK. With Fourier harmonic analysis, BK eyes were found to have significantly larger anterior and posterior regular astigmatism, asymmetry component and higher-order irregularity. Asymmetry component and higher-order irregularity that accounted for the posterior irregular astigmatism increased as CCT increased in BK. Higher-order irregularity in the posterior cornea also positively correlated with worsening best corrected visual acuity. Subgroup analysis found significant correlations between CCT and posterior higher-order irregularity for intraocular surgery and laser iridotomy, but not Fuchs endothelial corneal dystrophy. This study has significance in that it revealed the characteristics of the corneal posterior irregular astigmatism of BK.

Development and Testing of a Compact Autorefractor Based on Double-Pass Imaging.

Autorefraction is an objective way to determine the refractive error of the eye, without the need for feedback by the patient or a well-educated practitioner. To make refractive measurements more accessible in the background of the growing prevalence of myopia, a compact autorefractor was built, containing only few optical components and relying on double-pass imaging and the physical properties of the point-spread function and digital image processing instead. A method was developed to analyze spherical defocus as well as the defocus and angle of astigmatism. The device was tested using calibrator eye models in a range of ± 15 D spherical defocus and -3 D astigmatic defocus. Reliable results could be achieved across the whole measurement range, with only a small increase in deviation toward high values of refractive errors, showing the feasibility of a PSF-based approach for a compact and low-cost solution for objective measurements of refractive error.

Keratoconus enlargement as a predictor of keratoconus progression.

Numerous approaches have been designated to document progression in keratoconus, nevertheless there is no consistent or clear definition of ectasia progression. In this present study, we aim to evaluate Keratoconus Enlargement (KCE) as a parameter to document ectasia progression. We define KCE as an increase of more than 1D in the anterior curvature of non-apical corneal areas. We have designed a longitudinal study in 113 keratoconic eyes to assess keratoconus progression. KCE was compared with variables commonly used for detection of keratoconus progression like Kmax, Km, K2, PachyMin, D-Index, Corneal Astigmatism and PRC of 3.0 mm centered on the thinnest point. The variations of keratometric readings, D-index and ELEBmax showed positive associations with KCE. Evaluating the performance of Kmax, D-index and KCE as isolated parameters to document keratoconus progression we found a sensitivity of 49%, 82% and 77% and a specificity of 100%, 95% and 66% to detect keratoconus progression (p < 0.001 for all). This difference in sensitivity can be explained by the changes in keratoconus outside the small area represented by Kmax. The inclusion of KCE should be considered in the evaluation of keratoconus progression in conjunction with other variables to increase the reliability of our clinical evaluation.

Central and mid-peripheral corneal astigmatism in an elderly population: a retrospective analysis of Scheimpflug topography results.

Implantation of toric intraocular lenses (IOLs) has become standard in the correction of corneal astigmatism. The IOL selection is based on keratometric measurements of the central cornea. However, mid-peripheral corneal changes may yield suboptimal correction in patients with larger pupils. This study retrospectively analyzed corneal topography data collected using a Scheimpflug device during routine clinical examinations. Of 11,953 patients, 641 met the inclusion criteria. Total corneal astigmatism was compared between five concentric zones (2-6 mm) using vector analysis. The absolute difference between astigmatism at 2 mm and 6 mm was 0.30 D (- 0.36 to 0.64), which decreased to 0.10 D (0 to 0.20) between the 5- and 6-mm zone. With-the-rule astigmatism was the most prevalent (53%), 34% had against-the-rule (ATR), and 13% had oblique. The decrease of the cylinder power with the diameter differed significantly between the three types, with ATR and oblique astigmatism being associated with the steepest change. Patients with high corneal astigmatism tend to demonstrate larger differences between the center and mid-periphery than those with low and moderate astigmatism. In conclusion, we demonstrated that central corneal astigmatism differs from that measured at the mid-periphery and that a larger difference was found in patients with ATR, oblique and high astigmatism.

A multicenter study of interocular symmetry of corneal biometrics in Chinese myopic patients.

It is essential to know the normal range of the interocular symmetry of the cornea (ISC) for keratoconus diagnosis and corneal substitutes design. In the present study we investigated the interocular symmetry of corneal biometrics in 6,644 Chinese myopic patients from multiple ophthalmic centers. Corneal biometrics of both eyes were exported from the Pentacam instrument. Interocular symmetry of the corneal biometrics was analyzed by Spearman's correlation test, intraclass correlation coefficient (ICC) analysis and Bland-Altman plot. Significantly strong interocular correlations were found in anterior and posterior corneal curvatures, corneal diameter, corneal thickness, corneal volume, corneal eccentricity, and corneal asphericity (r = 0.87-0.98, all P < 0.001). Moderate interocular correlations were observed in whole corneal astigmatism (r = 0.78) and posterior corneal astigmatism (r = 0.73). ICC between the right and left eyes was 0.94-0.98 for anterior and posterior corneal curvatures, corneal diameter, corneal thickness and corneal volume, 0.80-0.88 for corneal eccentricity and asphericity, and 0.73-0.79 for corneal astigmatism (all P < 0.001). Bland-Altman plot showed that the 95% limit of agreement between both eyes was narrow and symmetric in most of the corneal biometrics, suggesting strong interocular agreements in these corneal biometrics. In conclusion, significant interocular symmetry of corneal biometrics is observed in Chinese myopia patients. Extra attention should be paid to patients with interocular corneal asymmetry.

[Comparison of corneal refractive power and astigmatism measured by the new anterior segment optical coherence tomographic device and Scheimpflug imaging device in age-related cataract patients].

Objective: To compare the difference and agreement of corneal refractive power and astigmatism measured by the new swept-source anterior segment optical coherence tomography (SS-AS-OCT) device (CASIA2) and Scheimpflug imaging device (Pentacam) in age-related cataract patients. Methods: In this cross-sectional study, 112 eyes of 112 patients with age-related cataract were examined before phacoemulsification in the Tianjin Medical University Eye Hospital from April to May 2020. The steep keratometry (Ks), flat keratometry (Kf), mean keratometry (Km), degree and axis of astigmatism of the corneal anterior and posterior surfaces and the total cornea were recorded. The difference in astigmatism was analyzed by the arithmetic method and the vector method. The difference of data was evaluated using Paired t test or Wilcoxon test. The agreement of data was evaluated using Bland-Altman plots. Results: The patients were 44 males and 68 females with an average age of (67±10) years. There were no statistically differences in the Ks and Km values of the corneal anterior surface between the Pentacam and the CASIA2 (both P>0.05). There was significant difference in the Kf values of the corneal anterior surface between the Pentacam and the CASIA2 [(44.24±1.73) D vs. (44.14±1.64) D; t=2.278; P<0.05]. The Ks, Kf, and Km values of the posterior surface of the cornea measured by the Pentacam and the CASIA2 were (-6.60±0.29) D vs. (-6.45±0.28) D, (-6.34±0.27) D vs. (-6.17±0.25) D, and (-6.47±0.26) D vs. (-6.31±0.25) D, respectively. The Ks, Kf, and Km values of the total cornea measured by the two instruments were (45.08±1.84) D vs. (43.94±1.64) D, (44.18±1.85) D vs. (43.02±1.64) D, and (44.63±1.82) D vs. (43.48±1.60) D, respectively. There were significant differences in the Ks, Kf, and Km values of the posterior surface of the cornea and the total cornea (t=-14.440, -13.522, -17.186, 21.016, 21.819, 22.981; all P<0.01). The degree and axis of astigmatism of the corneal anterior and posterior surfaces and the total cornea showed no statistically significant difference (all P>0.05). Vector operation results showed that the astigmatism difference vector (DV) of the Pentacam and the CASIA2 on the anterior surface of the cornea was 0.06 D@57°±0.64 D,>0.50 D in 47 eyes (41.96%). The astigmatism DV on the posterior surface of the cornea was 0.07 D@174°±0.21 D, >0.50 D in 2 eyes (1.79%). The astigmatism DV on the total cornea was 0.13 D@3°±0.69 D,>0.50 D in 59 eyes (52.68%). The results of the two devices were positively correlated (r values of the Ks, Kf, Km, and astigmatism degree on the anterior surface of the cornea were 0.970, 0.968, 0.976, and 0.697, respectively, on the posterior surface of the cornea were 0.918, 0.875, 0.925, and 0.517, respectively, and on the total cornea were 0.951, 0.955, 0.959, and 0.622, respectively; all P<0.01). Bland-Altman analysis showed that the Ks, Kf, Km, and astigmatism degree of the corneal anterior and posterior surfaces measured by the two devices were consistent, with 2.68% to 8.04% of the measured values outside 95% limits of agreement (95%LoA). The 95%LoA of the total corneal Ks, Kf, and Km between the two devices was 0.01 to 2.28 D, 0.06 to 2.27 D, and 0.10 to 2.20 D, respectively, with a wide 95%LoA range and poor consistency. Conclusions: The corneal refractive power and astigmatism measured by the CASIA2 and the Pentacam shows little difference on the anterior surface of the cornea, with good agreement. However, the refractive power results of the posterior surface of the cornea and the total cornea show great difference, suggesting that these two instruments cannot be used interchangeably in clinical practice. (Chin J Ophthalmol, 2021, 57: 48-55).

The contribution of ocular residual astigmatism to anterior corneal astigmatism in refractive astigmatism eyes.

To determine the distribution of ocular residual astigmatism (ORA) in astigmatic eyes and the influence on the anterior corneal (ACA) and refractive astigmatism (RA). A total of 165 children met the inclusion criteria. Right eyes' data were analyzed. Using Thibos vector analysis to calculate ORA. Spearman correlation analysis was used to obtain the correlation between the magnitude of ORA, ACA and RA. The median magnitude of ORA in astigmatic eyes was 0.57 D, with interquartile range was 0.42 D. And they were main against-the-rule (57.6-75.8%) and oblique astigmatism (13.9-34.5%) ORA. The ORA in 140 eyes (84.8%) acted as an offset to ACA, meanwhile, 25 eyes (15.2%) superimposed it. About 98% (97.9-98.4%) against-the-rule and 75% (73.9-82.5%) oblique ORA counteracted ACA, nevertheless, all with-the-rule ORA had a superimposed effect on ACA. For with-the-rule ACA, about 86% (85.4-85.9%) ORA worked to offset it. There was statistically correlations between ORA and ACA (r = 0.17, P = 0.03), ORA and RA (r = - 0.27, P = 0.001). The magnitude of ocular residual astigmatism was relatively small in children's astigmatic eyes. Both against-the-rule and oblique ORA can counteract with-the-rule ACA.

[Comparison of sterile donor tomography in the eye bank and graft tomography after penetrating keratoplasty]. / Vergleich der sterilen Spendertomographie in der Hornhautbank mit der Tomographie des Transplantates nach perforierender Keratoplastik.

BACKGROUND: Since 2018 we routinely use sterile donor tomography in the eye bank to avoid refractive surprises after keratoplasty. The purpose of this study was to compare donor tomography parameters measured with anterior segment optical coherence tomography (AS-OCT) with tomography parameters of the graft after penetrating keratoplasty (PKP). METHODS: This study enrolled 193 eye bank donor corneal tissues used for PKP (graft diameter 8.2 ± 0.7 mm). Preoperative measurements were taken using the AS-OCT Casia 2 (Tomey, Nagoya, Japan). The measurements were repeated postoperatively after 5 ± 4 months with all sutures in place and after 22 ± 4 months after removal of all sutures. Preoperative and postoperative values were compared using a Wilcoxon signed-rank test. RESULTS: Postoperatively, with all sutures in place (or without sutures), the dioptric power (P) at the anterior surface (a) of the cornea remained unchanged (-0.2 D, p = 0.78) (2.7 D bigger, p < 0.01) in the steep meridian (S) (PaS) and 4.5 D (2.8 D, p < 0.01) smaller in the flat meridian (F) (PaF) in comparison with the donor tomography values. The astigmatism (a) was 4.3 D (5.4 D, p < 0.01) bigger. At the posterior surface (p) the PpS was 0.9 D (0.9 D, p < 0.01) and PpF 0.3 D (p < 0.01) (0.1 D, p = 0.42) smaller, while the astigmatism (p) was 0.7 D (0.9 D) bigger (p < 0.01). The central corneal thickness was 55.7 µm (p < 0.01) (27.5 µm, p = 0.01) smaller. The total power of the transplant after removal of all sutures did not change significantly in comparison with the eye bank measurements. CONCLUSION: Central corneal thickness, dioptric power (P) and astigmatism all changed postoperatively compared to donor tomography values, except P at the steep meridian of the anterior corneal surface with all sutures in place and P at the flat meridian of the posterior corneal surface after removal of all sutures; however, the total power of the transplant after removal of all sutures did not change significantly. This information may be of value for IOL power calculation in the classical triple procedure.

Distorted optical input affects human perception.

Collinear facilitation, the mechanism for grouping contour elements, is a process involving lateral interactions that improve the detectability of a target by the presence of collinear flankers. It was shown that the development of collinear facilitation is experience dependent and that it may be impaired when the visual input is distorted in one meridian (meridional amblyopia). In oblique astigmatism, the blurring is on the opposite oblique meridian in both eyes, resulting in two conflicting images, which may affect the development of binocular vision. We hypothesized that the collinear facilitation of adults with oblique astigmatism is reminiscent of the abnormal development of the lateral facilitation of meridional amblyopia. We explored the perception of binocular vision and collinear facilitation in cases of both distorted and non-distorted vision. Fully corrected participants that tested for the target contrast detection of Gabor patches and two collinear flankers, presented for 80 ms, were positioned at different orientations (0° (180°), 45°, 90°, and 135°) and for different eyes (monocular, binocular). The results show a significant anisotropy for monocular collinear facilitation between the blured and the clear meridians, being lower in the blurriest meridian than in the clearest meridian, resembling the meridional amblyopia results. Collinear facilitation results in poor binocular summation between the monocular channels. Our results indicate that the perceptual behavior was similar to that of meridional amblyopic subjects having an anisotropy of collinear facilitation between cardinal meridians in oblique astigmatic subjects.

Three-Dimensional Single-Molecule Localization Microscopy in Whole-Cell and Tissue Specimens.

Super-resolution microscopy techniques are versatile and powerful tools for visualizing organelle structures, interactions, and protein functions in biomedical research. However, whole-cell and tissue specimens challenge the achievable resolution and depth of nanoscopy methods. We focus on three-dimensional single-molecule localization microscopy and review some of the major roadblocks and developing solutions to resolving thick volumes of cells and tissues at the nanoscale in three dimensions. These challenges include background fluorescence, system- and sample-induced aberrations, and information carried by photons, as well as drift correction, volume reconstruction, and photobleaching mitigation. We also highlight examples of innovations that have demonstrated significant breakthroughs in addressing the abovementioned challenges together with their core concepts as well as their trade-offs.

Comparison of eye-rubbing effect in keratoconic eyes and healthy eyes using Scheimpflug analysis and a dynamic bidirectional applanation device.

PURPOSE: To compare the effect of eye rubbing on Scheimpflug imaging parameters and corneal biomechanics in eyes with keratoconus and healthy eyes. SETTING: Oftalmosalud Instituto de Ojos, Lima, Peru. DESIGN: Prospective cohort study. METHODS: The study included healthy and keratoconus patients who attended the institution between January 2017 and July 2017. Eye rubbing was performed for 1 minute followed by a 5-second break, followed by further rubbing for 1 minute. Baseline tests were performed before rubbing; post-rubbing tests were performed immediately after (0 minutes), and then again at 7 minutes and 14 minutes. Parameters related to anterior and posterior curvature and elevation, pachymetry, and corneal biomechanics obtained from tomography with a rotating Scheimpflug camera (Pentacam HR) and a dynamic bidirectional applanation device (Ocular Response Analyzer) were measured and compared between healthy and keratoconic eyes. RESULTS: The study included 30 healthy eyes and 31 keratoconic eyes. In the healthy group, the immediate mean changes in steeper anterior keratometry, posterior astigmatism, anterior chamber volume (ACV), flattest posterior keratometry, and Goldmann-correlated intraocular pressure (IOPg) after eye rubbing were 0.07 diopters (D) ± 0.15 (SD), -0.01 ± 0.08 D, 0.03 ± 7.06 mm3, -0.001 ± 0.04 mm, and -1.21 ± 1.99 mm Hg, respectively, whereas the mean changes in the keratoconus group were -0.03 ± 0.32 D, 0.14 ± 0.50 D, -5.09 ± 8.45 mm3, 0.03 ± 0.06 mm, and -1.61 ± 1.41 mm Hg, respectively. There were statistically significant differences between the preoperative and postoperative eye-rubbing values of posterior astigmatism, ACV, and IOPg in the keratoconus group (P = .03, P = .0003, and P = .001, respectively) but not in the healthy group (P = .65, P = .85, and P = .23, respectively). CONCLUSIONS: Unlike the healthy eyes group, the keratoconus group experienced significant changes in ACV, IOP, and corneal posterior astigmatism after eye rubbing.

Predictability of the vault after posterior chamber phakic intraocular lens implantation using anterior segment optical coherence tomography.

PURPOSE: To determine whether vault measurements after placement of a hole implantable collamer lens (hole ICL) (KS-AquaPORT) can be predicted by angle-to-angle (ATA) and white-to-white (WTW) measurements obtained with anterior segment optical coherence tomography (AS-OCT). SETTING: Sanno Hospital, Tokyo, Japan. DESIGN: Retrospective case series. METHODS: Eyes were observed for 3 months after hole ICL implantation for myopia or myopic astigmatism. Central vault, ATA, and WTW measurements were obtained before and after surgery using the swept-source AS-OCT CASIA2 system. RESULTS: The study included 44 eyes (23 patients). The mean patient age and preoperative spherical equivalent, ATA, and WTW values were 36.2 years ± 8.8 (SD), -6.23 ± 3.41 diopters (D), 12.03 ± 0.40 mm, and 11.72 ± 0.40 mm, respectively. The safety index and efficacy index 3 months postoperatively were 1.13 ± 0.21 and 0.91 ± 0.30, respectively. Regarding predictability, 93.2% of eyes were within ±0.50 D of the attempted correction and all eyes were within ±1.00 D. The reproducibility coefficients for the ATA distance and WTW distance were 0.998 and 0.960, respectively. The mean postoperative central vault was 491.6 ± 189.5 µm. There was a significant correlation between postoperative vault and the ICL size and ATA distance (Spearman rank correlation coefficient r = 0.59, P < .001) but not between the ICL size and WTW distance (r = 0.27, P = .08). CONCLUSION: The ATA measurements had higher reproducibility than the WTW measurements on AS-OCT, making it is a more important predictor of postoperative vault.

Características del astigmatismo en niños / Characteristics of astigmatism in children

RESUMEN Objetivo: Identificar las características del astigmatismo en los niños. Métodos: Se realizó un estudio descriptivo y transversal en pacientes atendidos en el Servicio de Oftalmología Pediátrica del Instituto Cubano de Oftalmología Ramón Pando Ferrer en el período de junio del año 2016 a diciembre de 2017. La muestra estuvo conformada por 61 niños (122 ojos) con astigmatismo, quienes cumplieron los criterios de inclusión y exclusión. Las variables del estudio fueron la edad, el sexo, el tipo de astigmatismo, los síntomas, la agudeza visual sin y con corrección, el cilindro refractivo, el cilindro topográfico y el equivalente esférico. Resultados: El astigmatismo mixto fue el más relevante en todas las edades, y el sexo no fue significativo. El síntoma más referido fue la dificultad para ver de cerca (33 pacientes) para un 54,9 por ciento y en edades de 6 a 9 años. La media más baja de la agudeza visual fue 0,22 para el astigmatismo miópico compuesto y la mejor agudeza visual corregida fue para el astigmatismo miópico simple (0,94). La media del cilindro refractivo y topográfico fue de 2,71 y 2,45 dioptrías respectivamente. Los valores topográficos y refractivos mostraron diferencias significativas en los astigmatismos miópico compuesto y mixto (p= 0,002). Los equivalentes esféricos más cercanos a la emetropía (-0,5 a 0,5) presentaron la media más alta de agudeza visual sin corrección. Conclusión: El astigmatismo miópico compuesto afecta más la agudeza visual sin corrección y presenta diferencias entre el cilindro refractivo y topográfico, al igual que el astigmatismo mixto(AU)

ABSTRACT Objective: Describe the characteristics of astigmatism in children. Methods: A descriptive cross-sectional study was conducted of patients cared for at the Pediatric Ophthalmology Service of Ramón Pando Ferrer Cuban Institute of Ophthalmology from June 2016 to December 2017. The sample was 61 children (122 eyes) with astigmatism who met the inclusion and exclusion criteria. The study variables were age, sex, type of astigmatism, symptoms, visual acuity with and without correction, refractive cylinder, topographic cylinder and spherical equivalent. Results: Mixed astigmatism was the most relevant type in all age groups, whereas sex was not significant. The symptom most frequently reported was difficulty to see up close: 33 patients (54.9 percent) in the 6-9 years age group. The lowest visual acuity mean was 0.22 for compound myopic astigmatism, whereas the best corrected visual acuity corresponded to simple myopic astigmatism (0.94). Mean refractive and topographic cylinder was 2.71 and 2.45 diopters, respectively. Topographic and refractive values were significantly different in compound myopic and mixed astigmatism (p= 0.002). The spherical equivalents closest to emmetropia (-0.5 to 0.5) exhibited the highest mean visual acuity without correction. Conclusions: Compound myopic astigmatism affects uncorrected visual acuity more markedly and presents differences between the refractive and the topographic cylinder just like mixed astigmatism(AU)

Evaluation of Corneal Morphology in Patients With Hemifacial Spasm.

PURPOSE: To determine whether the corneal topographic parameter values, individual corneal layer thicknesses, and its endothelial layer morphology are different in patients with hemifacial spasm (HFS) than in the control contralateral eye. METHODS: This study was designed as a prospective study. Among patients who applied to our hospital within the past 3-year period, those with HFS in one eye (study eyes) and a completely normal contralateral eye (control eyes) were included in this study. In addition to a complete ophthalmologic examination, all patients were scanned by the Pentacam Scheimpflug camera, and a corneal endothelium cell count was taken using a Topcon Specular Microscope. Also, the thickness of the corneal sublayers was measured on the central cornea with anterior segment module of spectral domain optical coherence tomography. Data entered using SPSS software were then evaluated by paired t test; P<0.05 value was considered statistically significant. RESULTS: Twenty-eight patients (16 women and 12 men) were evaluated. Steep K, Kmax, and astigmatism values were significantly higher in the study eyes of patients with HFS than in the control eyes (P<0.05, for all). In addition, the total corneal thickness and corneal stromal thickness measurements in the study eyes were statistically significantly thinner than the control eyes (P=0.04 and P<0.001, respectively). Specular microscopy parameters were not statistically significant between the study eyes and control eyes (P>0.05, for all). CONCLUSION: Corneal stromal thinning suggests that chronic exposure to hypoxia may induce this effect through extracellular matrix remodeling and losses in collagen framework content in patients with HFS.

A Multicenter Study on Early Outcomes of Small-Incision Lenticule Extraction for Myopia.

This study was aimed to investigate the early clinical outcomes of small-incision lenticule extraction (SMILE) to correct both myopia and myopic astigmatism at major clinical centers in Japan. This case series consisted of two hundred fifty-two eyes of 130 consecutive patients who underwent SMILE surgery (29.5 ± 6.3 years, mean age ± standard deviation), with spherical equivalents of -4.33 ± 1.61 D. We determined the safety, efficacy, predictability, stability, and adverse events of this procedure. Corrected distance visual acuity significantly improved, from -0.18 ± 0.04 preoperatively to -0.19 ± 0.07 logMAR postoperatively (paired t-test, p < 0.001). Uncorrected distance visual acuity also significantly improved, from 1.05 ± 0.26 preoperatively to -0.15 ± 0.11 logMAR postoperatively (p < 0.001). 88% and 98% of eyes were within ± 0.5 and 1.0 D of the targeted correction, respectively. Changes in manifest spherical equivalent from 1 week postoperatively were 0.02 ± 0.35 D (p = 0.127). No vision-threatening complications were observed in any of the cases. SMILE performed well in the correction of myopic refractive errors, and we experienced no severe complications in this series, indicating its feasibility as a surgical option for the treatment of these eyes.

Effects of aging on corneal parameters measured with Pentacam in healthy subjects.

Our purpose was to prospectively analyze the age-related changes of corneal Scheimpflug parameters in healthy subjects. Thirty-five eyes of 35 volunteers (age 14-67 years) were investigated with an average interval of 3.6 years. Changes of corneal parameters (flattest keratometric reading at anterior (K1F) and posterior surface (K1B), steepest keratometric reading at anterior (K2F) and posterior surface, anterior astigmatism, posterior astigmatism (AstigB), flat axis of anterior and posterior astigmatism (AxisB), thinnest pachymetric value (PachyMin), corneal volume (CV10-mm)) were analyzed. K1F and K2F decreased significantly during observation and showed stronger decrease in younger than in older individuals. Higher values proved to be more stable. K1B decreased significantly and the degree of decrease was dependent on its baseline value and age: in young subjects low values increased, high values decreased. AstigB decreased significantly and showed a baseline-dependent significant increase from lower and a significant decrease from higher initial values. Over time, the mean AxisB shifted significantly. PachyMin and CV decreased significantly with age, especially from higher baseline values in younger subjects. The results of this longitudinal study suggest that both corneal surfaces change significantly with age. We demonstrate for the first time that age and baseline values influence age-related changes of corneal parameters.

Unilateral corneal ectasia after small-incision lenticule extraction in a 43-year-old patient.

Unilateral corneal ectasia developed after small-incision lenticule extraction for mild myopia in a 43-year-old man with preoperative asymmetric astigmatism. The ectasia was diagnosed 4 years postoperatively. Preoperative data showed asymmetric astigmatism with no signs of forme fruste keratoconus. Inferior anterior curvature steepening exceeded 2.00 diopters without bulging of the posterior curvature, and pachymetric thickness exceeded 515 µm. Corneal ectasia can occur after small-incision lenticule extraction in patients older than 40 years with preoperative asymmetric astigmatism.

Toric lens implantation in cataract surgery: Automated versus manual horizontal axis marking, analysis of 50 cases.

SUBJECT: The main objective of our study was to evaluate the contribution of automated conjunctival registration in the alignment of toric intraocular lenses by comparing automated registration optimized with Callisto® to manual marking of the horizontal axis. MATERIALS AND METHODS: We performed a prospective, descriptive, monocentric study on patients undergoing cataract surgery with a toric intraocular lens (Asphina 709 Zeiss), performed by a surgeon with good experience in toric implants, between September 2016 and March 2017. We analyzed the agreement between the manual marking of the 0-180° axis versus the one automatically generated by the Callisto™, as well as the alignment of the IOL and the refractive results at 1 month. RESULTS: We included 50 eyes of 38 patients. The mean corrected astigmatism was 1,9 D. The mean difference between the 2 axes was 4,7° [0-12.3°]. Only 50 % of the preoperative manual markings were consistent with the automated measurement (<5°). At one month, the mean rotation recorded was 4,3° [0-29°]. The alignment was identical for 70 % (n=35) of the IOLs (≤5°). As for residual subjective astigmatism, the mean was 0.58 D. The mean visual acuity without correction was 8/10 and 55 % saw 10/10 without correction. DISCUSSION: Refractive performance depends on preoperative measurement, correct alignment of the IOL and its stability in the bag. Our study shows the value of automated conjunctival registration in the determination of the intraoperative axis of alignment, even with an experienced surgeon. This precision is essential for a good refractive result, especially since residual astigmatism in the case of misalignment will increase with the power of the implant. CONCLUSION: Our study shows excellent refractive results, regardless of the initial astigmatism, using automated alignment. Precision of toric implantation opens the way to toric multifocal implantation under the best conditions.

Association of birth weight with corneal power in early adolescence: Results from the National Health and Nutrition Examination Survey (NHANES) 1999-2008.

PURPOSE: To analyze the effect of birth weight on ocular morphology, refraction and visual function in early adolescents aged 12-15 years. MATERIAL AND METHODS: We conducted a secondary data analysis using the public use files from the National Health and Nutrition Examination Survey of the period from 1999 to 2008. Study participants aged 12 to 15 years were included with data on birth weight and ophthalmic parameters including presenting distance visual acuity, objective refraction and keratometry. Visual acuity, sphere, astigmatism in power vectors J0 and J45, corneal power and corneal astigmatism were evaluated for an association with birth weight. Linear and logistic regression with adjustment for age, sex, ethnicity, survey cycle and birth weight as independent variable were calculated. RESULTS: Linear regression analysis revealed an association between corneal power and birth weight (per 100g: beta = -0.04, p<0.001) in the univariate analysis, and in the model adjusted for age, sex, ethnicity and NHANES survey cycle (per 100g: beta = -0.04, p<0.001). A lower birth weight was associated with higher corneal power. We found no evidence for an association of visual acuity, sphere, spherical equivalent, J0-vector and J45-vector of astigmatism, corneal J0- or corneal J45-vector with birth weight. CONCLUSION: Our data demonstrate that low BW is linked to alterations in keratometric power even in early adolescents aged 12-15 years whereas visual acuity and refractive error showed no association.