Peripheral refraction of myopic eyes with spectacle lenses correction and lens free emmetropes during accommodation

Purpose To measure axial and off-axis refraction patterns in myopic eyes with spectacle lenses correction and lens free emmetropes in young healthy subjects at different target distances from 2.00 m (0.50 D) to 0.20 m (5.00 D) in terms of sphere, astigmatism, and spherical equivalent refraction. Methods Refraction was measured at the center, 20 and 40 degrees from the line of sight both nasally and temporally in 15 emmetropic and 25 myopic young healthy subjects with an open field, binocular, infrared autorefractor (Grand Seiko WAM-5500, Hiroshima, Japan). Fixation target was a Maltese cross set at 2.00, 0.50, 0.33 and 0.20 m from the corneal plane. Changes in off-axis refraction with accommodation level were normalized with respect to distance axial values and compared between myopic eyes with spectacle lenses correction and lens free emmetropes. Results Off-axis refraction in myopic eyes with spectacle lenses correction was significantly more myopic in the temporal retina compared to lens free emmetropes except for the closest target distance. Relative off-axis refractive error changed significantly with accommodation when compared to axial refraction particularly in the myopic group. This change in the negative direction was due to changes in the spherical component of refraction that became more myopic relative to the center at the 0.20 m distance as the J0 component of astigmatism was significantly reduced in both emmetropes and myopes for the closest target. Conclusion Accommodation to very near targets (up to 0.20 m) makes the off-axis refraction of myopes wearing their spectacle correction similar to that of lens free emmetropes. A significant reduction in off-axis astigmatism was also observed for the 0.20 m distance.

Intrastromal keratoplasty with intracorneal ring segments implantation as an independent method of visual rehabilitation in patients with keratoconus

Purpose. To assess the possibility of using intrastromal keratoplasty with intracorneal ring segments implantation as an independent technique to achieve visual rehabilitation in patients with keratoconus of the stages I and II. Material and methods. There were examined and operated 14 eyes (10 patients) with keratoconus of the stages I and II (classification by Izmailova SB, 2014). Patients were divided into two groups depending on the keratoconus stage. All patients underwent intrastromal keratoplasty with intracorneal ring segments implantation using the femtosecond technology. The on average follow-up was 5.7 months. Results. In the first group: the average UCVA value increased with from 0.31±0.21 to 0.81±0.31 (p<0.05); the BCVA increased from 0.89±0.08 to 0.94±0.10 (p>0.05); the spherical component of refraction decreased from 0.96±1.25 to 0.08±0.20 (p<0.05); the cylindrical component of refraction decreased from 4.25±1.73 to 0.50±1.22 (p<0.05). In the second group: UCVA increased from 0.51±0.40 to 0.61±0.28 (p<0.05); the BCVA increased from 0.70±0.17 to 0.81±0.26 (p>0.05); the spherical component of refraction decreased from 4.88±2,61±0.53±0.63 (p<0.05); the cylindrical component of refraction decreased from 2.69±1.65 to 1.41±1.02 (p<0.05). Conclusion. 1. After implantation of intracorneal ring segments, both in patients with I and in patients with the II stage of keratoconus, there was an increase in the UCVA and BCVA, as well as a significant reduction in maximal keratometry and coma, which provides the improving of the quality of vision. 2. In all cases the UCVA and BCVA that were obtained after the treatment reached a sufficiently high level to ensure the possibility of performing their professional functions, without resorting to additional surgical treatment techniques. That characterizes this method as an independent and sufficient to achieve high visual acuity in patients with I and II stages of keratoconus. Key words: keratoconus, corneal intrastromal segments, femtosecond laser, visual rehabilitation.

Treating intrasurgical complications of corneal refractive operation with customized ablation. A clinical case

Purpose: to evaluate the prospects of customized Finalfit based ablation for optical rehabilitation of a patient with corneal surface errors caused by intrasurgical microtome-induced damage of a corneal flap during a LASIK excimer laser correction of vision.Material and methods. In Helmholtz Center, a patient with such damage was given a phototherapeutic keratectomy (PTK) combined with topographyguided photorefractive keratectomy.Results. In two months after the surgery, the patient’s uncorrected visual acuity rose from 0.15 to 1.0; the spherical component of refraction changed from -3.5 to +1.0 D, the cylindrical component of refraction fell from 1.75 to 0.25 D. Aberrometry demonstrated a decrease of RMS from 2.19 to 0.61 D, Total HOAs from 2.281 to 0.829; Tilt from 0.406 to 0.313; HOA from 1.152 to 0.247, Coma from 0.298 to 0.124, Trefoil from 1.088 to 0.094, SA from 0,127 to 0,021.Conclusion. The clinical case demonstrates the expediency and efficiency of corneal remodeling for the rehabilitation of induced errors of the corneal surface by excimer laser correction of vision based on PTK (Flex scan) + FinalFit after corneal refractive surgery.

Aerosol optical properties derived from POLDER-3/PARASOL (2005–2013) over the Western Mediterranean Sea – Part 2: Spatial distribution and temporal variability

The Mediterranean atmosphere is impacted by a variety of natural and anthropogenic aerosols which exert a complex and variable pressure on the regional climate and air quality. This study focuses on the Western Mediterranean Sea (west of longitude 20∘ E) using the full POLarization and Directionality of the Earth's Reflectances version 3 (POLDER-3)/Polarization &amp; Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL) aerosol data record derived from the operational clear-sky ocean algorithm (collection 3) available from March 2005 to October 2013. This 8.5-year satellite data set includes retrievals at 865 nm of the total, fine-, and coarse-mode aerosol optical depth (AOD, AODF, and AODC, respectively), Ångström exponent (AE), and the spherical/non-spherical partition of the coarse-mode AOD (AODCS and AODCNS, respectively), that have been carefully validated over the study region (Formenti et al., 2018). Here, we analyze the spatial distribution, the seasonal cycle, and interannual variability of this ensemble of advanced aerosol products in three latitude bands (34–38, 38–42, and > 42∘ N) and for three sites (Ersa, Barcelona, Lampedusa) distributed on the western basin. POLDER-3 retrieves the high influence of north African desert dust over the region, which largely controls the spatial distributions (south-to-north decreasing gradient) and seasonal cycles (spring/summer maximum) of both AOD and coarse AOD, including its non-spherical component. In contrast, the coarse spherical component of AOD remains relatively homogenously low all year long over the region, whereas fine-mode AODs are generally more elevated in the eastern part of the region of study, especially north of the Adriatic Sea. From 2005 to 2013, annual POLDER-3 AOD evolution shows a decreasing trend of 0.0030 yr−1 in absolute value at 865 nm (0.0060 yr−1 at 550 nm). Such a downward evolution is much more pronounced and spatially extended for AODF (−0.0020 yr−1 at 865 nm) than for AODC. Our analysis also suggests that the North Atlantic Oscillation (NAO) index explains a significant part of the interannual variability of POLDER-3 AODC, reflecting its role on the frequency of Saharan dust transport over the region. Finally, the POLDER-3 data set highlights an improvement of air quality related to the fine aerosol component, with a marked evolution toward more frequent occurrence of clean conditions (≥ 75 % of daily AODF-865 nm<0.05) at the end of the period of study (2010–2013) over most of the Western Mediterranean Sea, and much less evidence of such a large-scale evolution for the coarse fraction. Therefore, despite the high and variable influence of mostly natural north African dust over the region, the POLDER-3 advanced aerosol data set appears sufficiently accurate to successfully resolve the concurrent downward trend of fine, primarily anthropogenic particles, most likely related to reduced emissions in the surrounding European countries.

Induced Astigmatism and Concomitant High Myopia Correction with Femtosecond Laser-assisted Intrastromal MyoRing Implantation

Purpose. Analysis of the results of astigmatism correction after penetrating keratoplasty and concomitant high myopia using the MyoRing ring implantation, clinical case as an example. Material and methods. Patient G., 51 years old, underwent surgery to correct astigmatism and concomitant high myopia. MyoRing was implanted in the right eye within corneal transplant limits using femtosecond laser-assisted intrastromal MyoRing implantation. Before the surgery uncorrected visual acuity at the operated eye was 0.01; corrected visual acuity 0.06; spherical component of refraction was (–)6.0 D, cylindrical component was (–)8.0 D. Mean keratometry in the right eye was 43.96 D. Corneal hysteresis was 6.5 mm Hg, corneal resistance factor was 5.5 mm Hg, cornea thickness in center was 529 mkm. The patient was followed up for one year. Results. In 12 months after the surgery visual acuity of the right eye without correction was 0.7 and 0.8 with correction. Spherical component was (–)1.0 D, cylindrical component was (–)2.0 D. Mean keratometry in the right eye was 35.10 D. Corneal hysteresis was 7.2 mm Hg, corneal resistance factor was 6.3 mm Hg, cornea thickness in center was 533 mkm. The patient was satisfied with the result of operation. Conclusion. Femtosecond laser-assisted intrastromal MyoRing implantation for correction induced astigmatism after penetrating keratoplasty and concomitant high myopia is efficient, safe and provides strengthening of biomechanical properties of the cornea besides refractive and visual effect. Key words: postkeratoplastic astigmatism, high myopia, MyoRing, femtosecond laser

Corneal topography in keratoconus evaluated more than 30 years after penetrating keratoplasty: a Fourier harmonic analysis

The aim of this observational study was to examine the characteristics of anterior and posterior corneal topography in keratoconic eyes more than 30 years after penetrating keratoplasty (PK). Patients who maintained clear grafts for more than 30 years after PK were included and divided into the keratoconus (KC) group or other diseases (Others) group, based on the primary indication. Twenty-six eyes of 26 patients were included. The KC group and the Others group included 14 eyes and 12 eyes, respectively. The KC group participants were younger at the time of surgery (P = 0.03). No differences were found in best-spectacle-corrected visual acuity, keratometric power, and central-corneal-thickness. Based on corneal topography using Fourier harmonic analyses, regular astigmatism in the anterior cornea was significantly larger (P = 0.047) and the spherical component in the posterior cornea was significantly lower (P = 0.01) in the KC group. The area under the receiver operating characteristic curve of the spherical component, regular astigmatism, asymmetry component, and higher-order irregularity were 66.07%, 63.10%, 57.14%, and 59.23%, respectively, in the anterior cornea and 80.65%, 52.98%, 63.10%, and 63.99%, respectively, in the posterior cornea. Our results suggested that Fourier harmonic analysis of corneal topography could be useful for patients with KC long after PK.

Keratorefractive Surgery for Residual Refractive Error Correction in Pseudophakic Patients

Purpose. Evaluation of the visual and refractive results of additional correction using LASIK and PRK methods in patients with residual refractive error after previous cataract surgery. Patients and methods. The prospective open study included 57 patients (79 eyes) who previously underwent cataract phacoemulsification (n = 37) or refractive lensectomy (n = 42) with various IOL models implantation (2012–2017). The average age of patients was 50.8 ± 13.9 (19–79) years. Operations LASIK (91.1 %) and PRK (8.9 %) were carried out according to standard methods. In 6 cases, femtosecond laser supported by laser correction. The target refraction ranged from –0.25 to 0.25 D in most (97.5 %) cases. The follow-up period ranged from 6 to 9 months. Results. The patients were divided into groups according to the type of residual refractive error (Group 1 — myopia, group II — emmetropia and group III — hyperopia). Statistically significant differences were determined for the species of previously implanted IOLs — in group II, the frequency of monofocal IOLs was significantly higher (p < 0.05). In group II, the values of the cylindrical component of refraction were significantly higher compared with groups I and III (p < 0.05). In group I, a significant (p < 0.05) decrease in the spherical component of refraction from –1.36 ± 0.92 to –0.2 ± 0.8 D was observed. In patients of group II, there was a slight increase in the spherical component of refraction from 0 ± 0.20 to 0.25 ± 0.29 D (p > 0.05). In group III, a significant (p < 0.05) decrease was observed in the spherical component of refraction from 1.27 ± 0.69 to 0.43 ± 0.49 D. When analyzing the cylindrical component of refraction in group I, its decline was noted from –0.69 ± 0.5 to –0.38 ± 0.46 D (p > 0.05). In group II, the largest decrease in the cylindrical component was observed from –1.6 ± 1.0 to 0.03 ± 1.10 Dptr (p < 0.01). In all the studied groups, a statistically significant (p < 0.05) increase in UCFVA was revealed in the postoperative period. Indicators K1 and K2 did not significantly change. Conclusion. The high efficiency of the correction using the LASIK, PRK and femtoLASIK methods on pseudophakic eyes with the achievement of the target refraction in most of the studied cases was shown. This method can be used as an alternative to spectacle and contact correction in patients with residual refractive error after cataract phacoemulsification and refractive lensectomy with IOL implantation.

Dynamic response characteristics of 93W alloy with a spherical structure

To study the dynamic response characteristics of 93W alloy spherical component under high overload, the deformation patterns of the 93W spherical component under different overloads are obtained by the sphereistic impact test, and the microscopic response characteristics are studied by the metallographic analysis experiments. Finally, the response characteristics are analyzed by the finite element method and the stress wave theory. The results show that with the change of impact overload, the axial direction of the 93W spherical component changes linearly with the radial deformation, and the axial strain increases with the increase of the impact overload. At the same time, along the radial direction from the center of the sphere, the micrograin distribution of 93W appears densely packed and sparsely separated, and the grain density is uniformly changed between dense area and sparse area, showing a ring-shaped “bright band” phenomenon between light and dark, and the width of the “bright band” is related to the size of the dense area of the grain; with the increase of the impact overload, the 93W alloy component first breaks at the central axis and the radial maximum position, and the fracture mode changes from the crystal fracture to the transgranular fracture tendency, and the two fracture forms eventually coexist.

Strategy for correcting congenital progressive high myopia with astigmatism

The article presents a strategy for optical correction of congenital progressive high myopia with astigmatism, including bioptic correction with a combination of soft contact lenses and glasses. First, monofocal soft contact lenses are selected in accordance with the spherical component, and then the residual astigmatism is determined and correct with additional cylindrical glasses with perifocal refractive gain. This allows correcting both the central and peripheral defocus simultaneously.

Accuracy of GRK-2200T Auto-refkeratometer in Subjective Acceptance for Refractive Errors

Introduction: Globally, the most common cause for diminution of vision is refractive errors and the number of patients with refractive errors is increasing day by day. The Auto-refraction (AR) is quick and patient friendly procedure as compared to retinoscopy and subjective refraction in finding out refractive errors. Hence, the accuracy of Auto-refractometer in terms of subjective acceptance (SA) should be taken into account before prescribing optical correction based on findings of that particular model of Auto-refractometer. So, this study is directed towards analysis of the accuracy of GRK-2200T Auto-retieratometer in terms of acceptance by comparing findings of AR with that of SC. Objectives: The aim of this study was to assess the refractive status of patient's eyes using auto refractometer (GRK-2200T auto-retierato meter) and to estimate the agreement of it in terms of accuracy in acceptance of subjective correction by the patient. Methodology: A hospital based prospective comparative study conducted on 226 eyes of 113 patients who visited out-patient department (OPD) of Ophthalmology at Nobel Medical College and Teaching Hospital (NoMCTH), Biratnagar diagnosed with Myopia, Hyperopia and Astigmatism. Duration of study was 4 months from 2nd October, 2018 to 2nd February, 2019. All data thus collected was subjected to statistical analysis by using SPSS version 22. Result The mean age of the study subjects was 26.91±7.79 years with male to female ratio of 0.47. When spherical power, cylindrical power and the axis are taken into consideration together, only 13.3% of the total tested eyes subjectively accepted the AR values unchanged. On subjective correction, 32.7% of the tested eyes accepted spherical power while 46.5% accepted cylindrical power and 50.9% accepted axis of AR unchanged. About 52.2% of the total eyes examined fall within the deviation of spherical equivalent (SE) of ±o.25D and up to 67.3% of them fall within the deviation of ±o.50D. Conclusion The auto refraction by GRK-2200T auto-retieratometer was found to be satisfactory for a preliminary refraction but not satisfactory as substitutes for conventional subjective refraction. However, auto refraction values obtained by GRK-2200T auto-retieratometer could be important in order to accurately prescribe the cylindrical power as well as its axis than the spherical component.