Relative peripheral refraction in school children with different refractive errors using a novel multispectral refraction topographer

AIM:To compare relative peripheral refraction(RPR)in Chinese school children with different refractive errors using multispectral refraction topography(MRT).METHODS:A total of 713 eyes of primary school children[172 emmetropia(E),429 low myopia(LM),80 moderate myopia(MM),and 32 low hypermetropia(LH)]aged 10 to 13y were analyzed.RPRs were measured using MRT without mydriasis.MRT results showed RPR at 0-15°(RPR 0-15),15°-30°(RPR 15-30),and 30°-45°(RPR 30-45)annular in the inferior(RPR-I),superior(RPR-S),nasal(RPR-N),and temporal(RPR-T)quadrants.Spherical equivalent(SE)was detected and calculated using an autorefractor.RESULTS:There were significant differences of RPR 15-30 between groups MM[0.02(-0.12;0.18)]and LH[-0.13(-0.36;0.12)](P<0.05),MM and E[-0.06(-0.20;0.10)](P<0.05),and LM[-0.02(-0.15;0.15)]and E(P<0.05).There were also significant differences of RPR 30-45 between groups MM[0.45(0.18;0.74)]and E[0.29(-0.09;0.67)](P<0.05),and LM[0.44(0.14;0.76)]and E(P<0.001).RPR values increased from the hyperopic to medium myopic group in each annular.There were significant differences of RPR-S between groups MM[-0.02(-0.60;0.30)]and E[-0.44(-0.89;-0.04)](P<0.001),and LM[-0.28(-0.71;0.12)]and E(P<0.05).There were also significant differences of RPR-T between groups MM[0.37(0.21;0.78)]and LH[0.14(-0.52;0.50)](P<0.05),LM[0.41(0.06;0.84)]and LH(P<0.05),and LM and E[0.29(-0.10;0.68),P<0.05].A Spearman’s correlation analysis showed a negative correlation between RPR and SE in the 15°-30°(P=0.005),30°-45°(P<0.05)annular(P=0.002),superior(P<0.001),and temporal(P=0.001)quadrants.CONCLUSION:Without pupil dilation,values for RPR 15-30,30-45,RPR-S,and T shows significant differences between myopic eyes and emmetropia,and the differences are negatively correlated with SE.

Reconfigurable mechanism-based metamaterials for ternary-coded elastic wave polarizers and programmable refraction control

Elastic metamaterials with unusual elastic properties offer unprecedented ways to modulate the polarization and propagation of elastic waves.However,most of them rely on the resonant structural components,and thus are frequency-dependent and unchangeable.Here,we present a reconfigurable 2D mechanism-based metamaterial which possesses transformable and frequency-independent elastic properties.Based on the proposed mechanism-based metamaterial,interesting functionalities,such as ternarycoded elastic wave polarizer and programmable refraction,are demonstrated.Particularly,unique ternary-coded polarizers,with 1-trit polarization filtering and 2-trit polarization separating of longitudinal and transverse waves,are first achieved.Then,the strong anisotropy of the proposed metamaterial is harnessed to realize positive-negative bi-refraction,only-positive refraction,and only-negative refraction.Finally,the wave functions with detailed microstructures are numerically verified.

A robust triaxial localization method of AE source using refraction path

Acoustic emission(AE)localization algorithms based on homogeneous media or single-velocity are less accurate when applied to the triaxial localization experiments.To the end,a robust triaxial localization method of AE source using refraction path is proposed.Firstly,the control equation of the refraction path is established according to the sensor coordinates and arrival times.Secondly,considering the influence of time-difference-of-arrival(TDOA)errors,the residual of the governing equation is calculated to estimate the equation weight.Thirdly,the refraction points in different directions are solved using Snell’s law and orthogonal constraints.Finally,the source coordinates are iteratively solved by weighted correction terms.The feasibility and accuracy of the proposed method are verified by pencil-lead breaking experiments.The simulation results show that the new method is almost unaffected by the refraction ratio,and always holds more stable and accurate positioning performance than the traditional method under different ratios and scales of TDOA outliers.

Prevalence and Factors Associated with Dry Eyes Syndrome in Glaucomatous Patients on Anti-Glaucoma Eye Drops Followed up at the Garoua Regional Hospital-Northern Cameroon

Background: Dry eye and glaucoma are two common pathologies in the elderly, and are very often associated. This association suggests a link between them and between their treatments. Our purpose for this study is to determine the prevalence of dry eye in our glaucoma patients treated with eye drops and deduce the factors associated with it. Patients and Methods: We conducted a cross-sectional, analytical study from October 2022 to September 2023 in the ophthalmology department of Garoua Regional Hospital in glaucoma patients aged over 15 years able to answer the Ocular Surface Disease Index (OSDI) questionnaires and treated with antiglaucoma eye drops for more than 3 months. These patients underwent a complete ophthalmological examination and a tear film break-up time test. Results: A total of 73 patients (146 eyes) were examined. The average age of the patients was 47.2 ± 16.5 years, with a male predominance of 54.8%. The prevalence of dry eye syndrome in our patients according to the OSDI score was 56.2% (95% CI) (44.8;67.6). The prevalence of dry eye syndrome on clinical examination of the BUT in the right eye was 83.7% (95% CI) (75.1;92.1) and 79.4% (70.2;88.7) in the left eye. The duration of antiglaucoma treatment was the factor associated with dry eye syndrome (p < 0.05) in glaucoma patients in our setting. Conclusion: Dry Eye Syndrome is common in glaucoma patients on drops in our setting. Treatment duration of more than 1 year seems to be associated with dry eyes.

Determination of the time of refractive stability after uneventful phacoemulsification in Indian eyes

BACKGROUND Knowledge about refractive stabilization and the accuracy of postoperative refractive error measurements are crucial for improved patient outcomes after phacoemulsification.Existing guidelines typically recommend waiting 4-6 wk before prescribing corrective lenses.Our research focused on identifying factors that influence refractive errors in the early stages of post-cataract surgery,thus contributing to the existing literature on this topic.AIM To investigate the time required for refraction stability after uneventful phacoemulsification surgery.METHODS We compared the variation and statistical significance of the difference in spherical,cylindrical components,and the spherical equivalent between the 1-and 6-wk follow-up period in a group of 257 eyes that underwent uneventful phacoemulsification with foldable intraocular lens implantation,all performed by a single experienced surgeon.The Wilcoxon-Signed Rank Test was utilized to assess the magnitude of the change and determine its statistical significance.The refractive stability was defined as the point at which the change in spherical equivalent was within±0.5 dioptres for two consecutive visits.RESULTS The average age of the patients was 64.9±8.9 yr.The differences observed in both the visits in spherical power(0.1±0.2),cylinder power(0.3±0.4),and spherical equivalent(0.2±0.2)were minimal and not statistically significant.The majority of eyes(93.4%)achieved refractive stability within 6 wk after the surgery.The cylindrical power differed between age groups at the 6th wk post-operative and the difference was statistically significant(P value 0.013).There were no significant differences in refractive stability when considering sex and axial length.CONCLUSION Phacoemulsification with foldable intraocular lens implantation results in no significant changes in refraction for the majority of cases during the 6-wk follow-up period.Therefore,a spectacle prescription can be given at the completion of 1 wk.

Effectiveness of intravitreal ranibizumab for diabetic macular edema in vitrectomized versus non-vitrectomized eyes:a Meta-analysis

AIM:To evaluate the effectiveness and safety of intravitreal ranibizumab(IVR)for diabetic macular edema(DME)in vitrectomized versus non-vitrectomized eyes.METHODS:The PubMed,EMBASE,Web of Science,Cochrane,EBSCO were comprehensively searched for studies comparing vitrectomized and non-vitrectomized eyes with DME.Clinical outcomes of best-corrected visual acuity(BCVA),central macular thickness(CMT),the mean number of intravitreal injection and adverse events were extracted and analyzed.RESULTS:Six studies involving 641 eyes were included.Final visual gain significantly improved and CMT significantly reduced in vitrectomized eyes at 6mo and 12mo visits(P<0.05).Although the mean reduction in CMT among non-vitrectomized eyes was significantly greater than in vitrectomized eyes at the 6mo[mean difference(MD)=53.57,95%confidence interval(CI):28.03 to 78.72,P<0.0001]and 12mo(MD=49.65,95%CI:19.58 to 79.72,P=0.01),no significant difference was detected in improvement in BCVA at either 6mo(MD=0.05,95%CI:-0.02 to 0.13,P=0.14)or 12mo(MD=0.03,95%CI:-0.04 to 0.09,P=0.43).Injection number of ranibizumab in non-vitrectomized eyes was significantly less than that in vitrectomized eyes during 6-month period(MD=0.60,95%CI:0.16 to 1.04,P=0.008),while there was no statistically significant difference between the two groups during 12mo of follow-up.CONCLUSION:Evidence from current study suggests that IVR was useful for both vitrectomized group and nonvitrectomized group with DME.Although less reduction in macular thickness is found in vitrectomized group,visual improvement between two groups is similar.

Insight into small eyes: a practical description from phenotypes presentations to the management

This narrative review aimed to have an algorithmic approach to microphthalmos by a systematic search.The definition can be related to a number of special phenotypes.In the more challenging cases of complex microphthalmos,relative anterior microphthalmos,and nanophthalmos,the surgeon can approach these cases more safely if they have a deep understanding of the anatomical variations and ideal formulae for intraocular lens computation and knows how to avoid intra-and post-operative complications.In this article,we review the criteria by which we recognize and describe pre-,intra-,and post-operative considerations,as well as discuss the ideal intraocular lenses for microphthalmos,given the intricate varieties of small eye phenotypes.

Intraocular pressure before and after capsulorhexis using two viscoelastic substances and two surgical approaches in enucleated porcine eyes

AIM:To investigate the influence of ophthalmic viscoelastic devices(OVDs)and different surgical approaches on the intraocular pressure(IOP)before and after creation of the curvilinear circular capsulorhexis(CCC)as a measure for anterior chamber stability during this maneuver.METHODS:Prospective experimental WetLab study carried out on enucleated porcine eyes.IOP was measured before and after CCC with the iCare Rebound tonometer(iCare ic200;iCare Finland Oy,Vantaa,Finland).The OVDs used were a cohesive one[Z-Hyalin,Carl Zeiss Meditec AG,Germany;hyaluronic acid(HA)]and a dispersive[Z-Celcoat,Carl Zeiss Meditec AG,Germany;hydroxy propylmethylcellulosis(HPMC)].The CCC was created using Utrata forceps or 23 g microforceps in different combinations with the OVDs.RESULTS:Using the Utrata forceps the IOP dropped from 63.65±6.44 to 11.25±3.63 mm Hg during the CCC.The use of different OVDs made no difference.Using the 23 g microforceps the IOP dropped from 65.35±8.15 to 36.55±6.09 mm Hg.The difference between IOP drop using either Utrata forceps or 23 g microforceps was highly significant regardless of the OVD used.CONCLUSION:Using the sideport for the creation of the capsulorhexis leads to a lesser drop in IOP during this maneuver compared to the main incision in enucleated porcine eyes.The use of different OVD has no significant influence on IOP drop.

Efficacy of Online Learning and Influence on Skin and Eyes Among College Students

To evaluate the efficacy of online learning and explore the impact of long-term use of electronic products on facial skin as well as eyes.A cross-sectional survey was conducted to 180 sophomores in Xi′an Jiaotong University by cluster random sampling from September to October 2021.The questionnaire covering study condition,skin lesion and Ocular Surface Disease Index.χ_(2) test was used to compare the facial skin condition among different groups,and spearman correlation test was used to test the correlation of rank data.During online education,students′learning pressure is reduced,their autonomy is improved,and the learning efficiency is reduced.There were differences in the incidence of facial itching and papules among different groups.Duration of use of electronic products was positively correlated with the facial itching,with an r value of 0.231(P<0.05);the proportion of pigmentation in non-blue light protection groups(12.8%)was higher than that in blue light protection groups(1.7%),the difference was statistically significant(χ_(2)=8.384,P<0.05).The prevalence of dry eye among college students is 66.7%,and the proportion of moderate to severe dry eye is 34.5%.The study autonomy has been improved during online teaching.Long-term use of electronic products and no blue light protection have an impact on facial skin.Students should enhance the knowledge of skin-care and eye-care and develop better habits.

Non-cycloplegic spherical equivalent refraction in adults:comparison of the double-pass system,retinoscopy,subjective refraction and a table-mounted autorefractor

AIM:To evaluate the accuracy of spherical equivalent(SE) estimates of a double-pass system and to compare it with retinoscopy,subjective refraction and a table mounted autorefractor.METHODS:Non-cycloplegic refraction was performed on 125 eyes of 65 healthy adults(age 23.5±3.0 years) from October 2010 to January 2011 using retinoscopy,subjective refraction,autorefraction(Auto kerato refractometer TOPCON KR-8100,Japan) and a double pass system(Optical Quality Analysis System,OQAS,Visiometrics S.L.,Spain).Nine consecutive measurements with the double-pass system were performed on a subgroup of 22 eyes to assess repeatability.To evaluate the trueness of the OQAS instrument,the SE laboratory bias between the double pass system and the other techniques was calculated.RESULTS:The SE mean coefficient of repeatability obtained was 0.22D.Significant correlations could be established between the OQAS and the SE obtained with retinoscopy(r=0.956,P【0.001),subjective refraction(r=0.955,P【0.001) and autorefraction(r=0.957,P【0.001).The differences in SE between the double-pass system and the other techniques were significant(P【0.001),but lacked clinical relevance except for retinoscopy;Retinoscopy gave more hyperopic values than the double-pass system-0.51±0.50D as well as the subjective refraction-0.23±0.50D;More myopic values were achieved by means of autorefraction 0.24±0.49D. CONCLUSION:The double-pass system provides accurate and reliable estimates of the SE that can be used for clinical studies.This technique can determine the correct focus position to assess the ocular optical quality.However,it has a relatively small measuring range in comparison with autorefractors(-8.00 to +5.00D),and requires prior information on the refractive state of the patient.

Comparison of non-cycloplegic photorefraction,cycloplegic photorefraction and cycloplegic retinoscopy in children

AIM: To compare the results of noncycloplegic photorefraction, cycloplegic photorefraction and cycloplegic refraction in preschool and non-verbal children.METHODS: One hundred and ninety-six eyes of 98children(50 females, 48 males) were included in the study. Firstly, non-cycloplegic photorefraction was achieved with Plusoptix A09; secondly, cycloplegic photorefraction was carried out with Plusoptix A09 after10 min cyclopentolate. Finally, 30 min after instillation of twice cyclopentolate, cycloplegic refraction was obtained with autorefraction and/or standard retinoscopy. Spheric equivalent, spheric power, cylindric power and cylindrical axis measurements were statistically compared.RESULTS: The mean age was 28.8±18.5mo(range12-72mo). The differences in spherical equivalent, spheric power and cylindrical power measured by the three methods were found statistically significant(P 【0.05).The spherical equivalent and spheric power measured by cycloplegic photorefraction were statistically higher than the measurements of the other methods(P 【0.05). The cylindrical power measured by cycloplegic refraction was statistically lower than the measurements of the photorefraction methods(P 【0.05). There was no significant difference in cylindrical axis measurements between three methods(P 】0.05).CONCLUSION: For the determination of refractive errors in children, the Plusoptix A09 measurements give incorrect results after instillation of cyclopentolate.Additionally, the cylindrical power measured by Plusoptix A09 with or without cycloplegia is higher. However, the non-cycloplegic Plusoptix A09 measures spheric equivalent and spheric power similar to cycloplegic refraction measurements in preschool and non-verbal children.

Excited state refraction of C_(70)/toluene studied by using 4f coherent imaging system with phase object

Dynamic nonlinearities of C70/toluene solution are measured and analysed by an improved picosecond timeresolved pump-probe system based on a nonlinear imaging technique with phase object. The photophysical parameters are determined by the five-level model, which is adopted to interpret the experimental data. The change of refraction index per unit density of the excited state obtained by a numerically simulation is a critical factor to determine the nonlinear behaviour of C70 in picosecond time regime.

Auto-refraction versus subjective refraction in different phakic and pseudophakic conditions:the Tehran Geriatric Eye Study(TGES)

AIM:To compare the subjective refraction data with non-cycloplegic auto-refraction findings in the geriatric population above 60 years of age according to the different crystalline lens conditions.METHODS:This report is a part of the Tehran Geriatric Eye Study(TGES)that was conducted from January 2019 to January 2020 on elderly population 60 years of age and above in Tehran.The samples were selected by multistage stratified random cluster sampling.Of 3791 individual invitees,3310(response rate:87.3%)participated in this study.All study participants underwent non-cycloplegic autorefraction(auto-refractometer/keratometer Nidek ARK-510)and subjective refraction.RESULTS:Regarding the sphere,eyes with mixed cataract had the worst limits of agreement(LoA:-1.24 to 0.87)and the best agreement was related to the pseudophakic eyes(LoA:-0.83 to 0.54).The highest(0.27±0.31 D)and lowest(0.21±0.27 D)differences between the two methods regarding the cylinder power were observed in eyes with cortical cataract and normal eyes,respectively.The worst LoA between the two methods in measuring the cylinder power was related to the eyes with mixed cataract(LoA:-0.44 to 0.96).Regarding the J0(horizontal/vertical components of astigmatism),the mean values of J0 obtained by auto-refraction were tended more toward against the rule direction in all crystalline lens conditions,and the two methods had the greatest difference in cortical cataract cases(0.05±0.17 D).Regarding the J45(oblique components of astigmatism),the lowest(0±0.11 D)and highest(-0.01±0.12 D)differences were observed in normal eyes and eyes with cortical cataract,respectively.CONCLUSION:The auto-refractometer/keratometer Nidek ARK-510 results in the elderly with different phakic and pseudophakic conditions do not correspond well with subjective refraction findings.This discrepancy in spherical findings is more pronounced in individuals with mixed cataract than in other cases.

Refractive errors in high myopic eyes after phacovitrectomy for macular hole

AIM: To examine the refractive prediction error in high myopic eyes after phacovitrectomy.METHODS: This retrospective comparative case series included 91 eyes(18 high myopic eyes and 73 non-high myopic eyes) of 91 patients who underwent successful phacovitrectomy(phacoemulsification, intraocular lens implantation, and pars plana vitrectomy). The high myopic eyes were defined as the eye with more than 26.0mm of axial length. The postoperative prediction error of mean error and mean absolute error were evaluated at4 mo postoperatively. Axial length and keratometry measurement were performed preoperatively and 4mo postoperatively using the IOL Master.RESULTS: The refractive outcome after phacovitrectomy showed significantly greater myopic shift in the high myopic eyes [-1.08 ±0.87 diopters(D)] than that in the non-high myopic eyes(-0.43 ±0.63 D, P =0.004). Axial length and keratometric value in the high myopic eyes were significantly increased(P =0.043, 0.037 respectively),whereas those in the non-high myopic group were not significantly increased(P =0.135, 0.347 respectively). The change of the axial length in the myopic eye(0.46±0.28 mm)was greater than that in the non- high myopic eye(0.11 ± 0.34 mm; P 【0.001).CONCLUSION: High myopic eyes showed more myopic shift than non-high myopic eyes after phacovitrectomy.The cause of myopic shift in high myopic eyes seems tobe attributed to actual elongation of the axial length in high myopia.

Novel application of multispectral refraction topography in the observation of myopic control effect by orthokeratology lens in adolescents

BACKGROUND Myopia,as one of the common ocular diseases,often occurs in adolescence.In addition to the harm from itself,it may also lead to serious complications.Thus,prevention and control of myopia are attracting more and more attention.Previous research revealed that single-focal glasses and orthokeratology lenses(OK lenses)played an important part in slowing down myopia and preventing high myopia.AIM To compare the clinical effects of OK lenses and frame glasses against the increase of diopter in adolescent myopia and further explore the mechanism of the OK lens.METHODS Changes in diopter and axial length were collected among 70 adolescent myopia patients(124 eyes)wearing OK lenses for 1 year(group A)and 59 adolescent myopia patients(113 eyes)wearing frame glasses(group B).Refractive states of their retina were inspected through multispectral refraction topography.The obtained hyperopic defocus was analyzed for the mechanism of OK lenses on slowing down the increase of myopic diopter by delaying the increase of ocular axis length and reducing the near hyperopia defocus.RESULTS Teenagers in groups A and B were divided into low myopia(0 D--3.00 D)and moderate myopia(-3.25 D--6.00 D),without statistical differences among gender and age.After 1-year treatment,the increase of diopter and axis length and changes of retinal hyperopic defocus amount of group A were significantly less than those of group B.According to the multiple linear analysis,the retinal defocus in the upper,lower,nasal,and temporal directions had almost the same effect on the total defocus.The amount of peripheral retinal defocus(15°-53°)in group A was significantly lower than that in group B.CONCLUSION Multispectral refraction topography is progressive and instructive in clinical prevention and control of myopia.

A COMBINED REFRACTION-DIFFRACTION-DISSIPATION MODEL OF WAVE PROPAGATION

A numerical model based on the mild-slope equation of water wave propagation over complicated bathymetry,taking into account the combined effects of refraction,diffraction and dissipation due to wavebreaking is presented.Wave breaking is simulated by modifying the wave height probability density func-tion and the wave energy dissipation mechanism is parameterized according to that of the hydraulic jumpformulation.Solutions of the wave height,phase function,and the wave direction at every grid point areobtained by finite difference approximation of the governing equations,using Gauss-Seidel Iterative Method(GSIM)row by row.Its computational convenience allows it to be applied to large coast regions tostudy the wave transformation problem.Several case studies have been made and the results compare verywell with the experiment data and other model solutions.The capability and utility of the model forreal coast areas are illustrated by application to a shallow bay of northeast Australia.

Frequency bands of negative refraction in finite one-dimensional photonic crystals

We have discussed theoretically the negative refraction in finite one-dimensional （1D） photonic crystals （PCs） composed of alternative layers with high index contrast. The frequency bands of negative refraction are obtained with the help of the photonic band structure, the group velocity and the power transmittance, which are all obtained in analytical expression. There shows negative transverse position shift at the endface when negative refraction occurs, which is analysed in detail.

Refraction of extraordinary rays and ordinary rays in the Savart polariscope

The refraction of rays in the Savart polariscope is different from the isotropic medium. We have analysed and discussed the refraction of rays in the Savart polariscope on the basis of the Snell law. The refraction formulae of the extraordinary rays and ordinary rays were derived. Results obtained may provide theoretical and practical guide lines for studying, developing and engineering of polarization interference imaging spectrometer.

Dynamic profile of ocular refraction in pediatric cataract patients after lens surgeries

AIM: To study the change in ocular refraction in patients with pediatric cataracts(PCs) after lens extraction. METHODS: A total of 1258 patients who were undergoing cataract extraction with/without intraocular lens(IOL)implantation were recruited during preoperative examinations between Jan 2010 and Oct 2013. Patient ages ranged from 1.5 mo to 14y. Follow-ups were conducted at1 wk, 1, and 3 mo postoperatively and every 3 mo in the first year, then 6 mo thereafter. Ocular refraction [evaluated as spherical equivalent(SE)] and yearly myopic shift(YMS)were recorded and statistically analyzed among patients with age at surgery, baseline ocular refraction, gender,postoperative time and laterality(bilateral vs unilateral). RESULTS: By Dec 31st 2015, 1172 participants had been followed for more than 2y. The median follow-up period was 3y. The critical factors affecting the ocular refraction of PC patients were baseline ocular refraction, postoperative time for both aphakic and pseudophakic eyes. YMS grew most rapidly in young childhood and early adolescence. CONCLUSION: After lens surgeries, ocular refraction in PC patients shows an individual difference of change.Further concerns should be raising to monitor the rapid myopic shift at early adolescence of these patients.

Reflection and refraction of attenuated waves at boundary of elastic solid and porous solid saturated with two immiscible viscous fluids

The propagation of elastic waves is studied in a porous solid saturated with two immiscible viscous fluids. The propagation of three longitudinal waves is represented through three scalar potential functions. The lone transverse wave is presented by a vector potential function. The displacements of particles in different phases of the aggregate are defined in terms of these potential functions. It is shown that there exist three longitudinal waves and one transverse wave. The phenomena of reflection and refraction due to longitudinal and transverse waves at a plane interface between an elastic solid half-space and a porous solid half-space saturated with two immiscible viscous fluids are investigated. For the presence of viscosity in pore-fluids, the waves refracted to the porous medium attenuate in the direction normal to the interface. The ratios of the amplitudes of the reflected and refracted waves to that of the incident wave are calculated as a non- singular system of linear algebraic equations. These amplitude ratios are used to further calculate the shares of different scattered waves in the energy of the incident wave. The modulus of the amplitude and the energy ratios with the angle of incidence are computed for a particular numerical model. The conservation of the energy across the interface is verified. The effects of variations in non-wet saturation of pores and frequencies on the energy partition are depicted graphically and discussed,