Effect of astigmatism and spherical equivalent correction on contrast sensitivity

AIM:To investigate the effect of astigmatism and spherical equivalent(SE)correction on contrast sensitivity(CS).METHODS:In this cross-sectional study,103 visually normal subjects aged 18 to 36y with bilateral regular astigmatism in range of 1.00 diopter cylinder(DC)to 4.00 DC and normal best-corrected visual acuity(20/20)were recruited.Binocular CS was assessed by linear sine-wave gratings at 1.5,3,6,12,and 18 cycles per degree(cpd),before correction of astigmatism,after full correction of astigmatism by cylindrical spectacle lenses,and after SE of refractive error.The repeated measures ANOVA and Bonferroni test were used to compare the effects of astigmatism correction on logCS.RESULTS:Totally 39 patients were male and 64 patients were female with the mean age of 28.25±5.38y.The average degree of astigmatism in right and left eye was 2.03±0.83 and 2.10±0.78,respectively.Increases in uncorrected astigmatic power correlated with decreases in the logCS,especially at high spatial frequencies.A statistically significant difference in logCS was found between these three cases:before correction of astigmatism,after SE of refractive error,and after full correction of astigmatism by cylindrical spectacle lenses at all frequencies(P<0.001),except at 18 cpd.At 18 cpd,there was no statistically significant difference between logCS before and after SE of refractive error(P=1.0).Also,there was no statistically significant difference in mean CS between with-the-rule(WTR)and against-the-rule(ATR)astigmatism,before correction of astigmatism,after correction of astigmatism with cylindrical lenses,and after SE of refractive error.CONCLUSION:Binocular astigmatism defocus decreases CS depending on the degree of astigmatism power;correction of this will improve patent’s quality of vision.Although high astigmatism refractive error(more than 2.00 DC)that is fully corrected by cylindrical spectacle lenses doesn’t increase the CS to the maximum value,especially at higher spatial frequencies(12 and 18).Also SE refractive error effects on improving CS in low astigmatism power(less than 2.00 DC),especially at lower spatial frequencies.

Lag of accommodation predicts clinically significant change of spherical equivalents after cycloplegia

AIM: To evaluate related factors with the change of spherical equivalents(ΔSE) and determine the suitable predictor of clinically significant ΔSE(≥0.50 D) with cyclopentolate hydrochloride on Chinese children. METHODS: A total of 145 right eyes of 145 children aged 4 to 15 y were enrolled. Intraocular pressure, axial length and lag of accommodation(LOA) were assessed before cycloplegia induced by 3 drops of 1% cyclopentolate at 5-minute intervals. SE was measured before and 1 h after the first drop of cyclopentolate. ΔSE was compared between different gender groups and among refractive groups. Multivariate linear regression analysis was performed to find related factors with ΔSE. ROC analysis was used to figure out the suitable predictor of clinically significant ΔSE.RESULTS: For the total 145 eyes, the mean SE reached up to-0.70±1.86 D from-1.30±1.62 D, with the mean ΔSE of 0.60±0.55 D. The mean ΔSE were 0.63±0.55 D and 0.57±0.56 D respectively in the male and female group(P=0.40). The mean ΔSE was significantly different among different refractive groups(P<0.0001), with the ΔSE of hyperopia group(1.12±0.64 D) larger than that of the emmetropia(0.56±0.43 D, P=0.001) and myopia group(0.32±0.28 D, P<0.0001). The ΔSE was correlated with LOA(B=-0.54, P<0.0001), cycloplegic SE(B=0.10, P<0.0001) and age(B=-0.04, P=0.015). ROC curve indicated that LOA predicted clinically significant ΔSE by 82% [area under the curve(AUC)=0.82] alone, while the value was slightly improved to 85%(AUC=0.85) in combination with axial length and 86%(AUC=0.86) in association with axial length as well as age.CONCLUSION: After cycloplegia with cyclopentolate, the ΔSE decreases with larger LOA, longer axial length and older age. Specifically, LOA plays a more vital role in predicting clinically significant ΔSE.

Distribution and correlation of refractive parameters in children with different corneal curvatures in southeast China

AIM:To analyze the distribution of refractive status in school-age children with different corneal curvatures(CC)and the correlation between CC and refractive status.METHODS:A total of 2214 school-aged children of grade 4 in Hangzhou who were screened for school myopia were included.Uncorrected distance visual acuity(UCDVA),non-cycloplegic refraction,axial length(AL),horizontal and vertical corneal curvature(K1,K2)were measured and spherical equivalent(SE),corneal curvature radius(CCR)and axial length/corneal radius of curvature ratio(AL/CR)were calculated.UCDVA<5.0 and SE≤-0.50 D were classified as school-screening myopia.According to the different CCRs,the patients were divided into the lower corneal curvature(LCC)group(CCR≥7.92)and the higher corneal curvature(HCC)group(CCR<7.92).Each group was further divided into the normal AL subgroup and the long AL subgroup.The refractive parameters were compared to identify any differences between the two groups.RESULTS:Both SE and AL were greater in the LCC group(P=0.013,P<0.001).The prevalence of myopia was 38% in the LCC group and 44% in the HCC group(P<0.001).The proportion of children without screening myopia was higher in the LCC group(62%)than in the HCC group(56%).Among these children without screening myopia,the proportion of long AL in the LCC group(24%)was significantly higher than that in the HCC group(0.012%;P<0.001).The change of SE in the LCC group was less affected by the increase of AL than that in the HCC group.CONCLUSION:School-aged children in the LCC group have a lower incidence of screening myopia and longer AL.Low CC can mask SE reduction and AL growth to some extent,and the change of AL growth change more in children with low CC than high CC.Before the onset of myopia,its growth rate is even faster than that after the onset of myopia.

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.

Quantitative analysis of optic disc changes in school-age children with ametropia based on artificial intelligence

AIM:To explore changes in the optic disc and peripapillary atrophy(PPA)in school-age children with ametropia using color fundus photography combined with artificial intelligence(AI)technology.METHODS:Based on the retrospective case-controlled study,226 eyes of 113 children aged aged 6–12y were enrolled from October 2021 to May 2022.According to the results of spherical equivalent(SE),the children were divided into four groups:low myopia group(66 eyes),moderate myopia group(60 eyes),high myopia group(50 eyes)and emmetropia control group(50 eyes).All subjects underwent un-aided visual acuity,dilated pupil optometry,best-corrected visual acuity(BCVA),intraocular pressure,ocular axis measurement and color fundus photography.RESULTS:The width of PPA,horizontal diameter ratio of PPA to the optic disc and area ratio of PPA to the optic disc were significantly different among the four groups(P<0.05).The width of the nasal and temporal neuroretinal rim,the roundness of the optic disc,the height of PPA,the vertical diameter ratio of PPA to the optic disc,and the average density of PPA in the high myopia group were significantly different compared with the other three groups(P<0.05).There were strong negative correlations between SE and area ratio of PPA to the optic disc(r=-0.812,P<0.001)and strong positive correlation between axial length(AL)and area ratio of PPA to the optic disc(r=0.736,P<0.001).CONCLUSION:In school-age children with high myopia,the nasal and temporal neuroretinal rims are narrowed and even lost,which have high sensitivity.The area ratio of the PPA to the optic disc could be used as an early predictor of myopia progression,which is of great significance for the development prevention and management of myopia.

Comparative study of functional optical zone:small incision lenticule extraction versus femtosecond laser assisted excimer laser keratomileusis

AIM:To investigate the size of functional optical zone(FOZ)after small incision lenticule extraction(SMILE)versus femtosecond laser assisted excimer laser keratomileusis(FS-LASIK)for myopia correction and potential associated factors for FOZ.METHODS:A total of 133 patients who received corneal refractive surgery in our hospital between November 2018 and July 2021 were retrospectively enrolled.There were 63 patients(123 eyes)in SMILE group and 70patients(139 eyes)in FS-LASIK group.The size of FOZ was measured using Pentacam 3-dementional anterior segment analyzer before and 3mo after surgery,so as to analyze postoperative achieved functional optical zone(AFOZ)and its contributing parameters.RESULTS:When planned functional optical zone(PFOZ)was 6.5 mm for both groups,AFOZ was 1.45±0.27 and 1.67±0.25 mm smaller than preoperative FOZ in SMILE group and FS-LASIK group 3mo after surgery.AFOZ in SMILE group was significantly larger than that in FS-LASIK group(P<0.001).Variation of FOZ was negatively correlated with preoperative spherical equivalent(SE)and positively correlated with variation of mean keratometry value(△Km),variation of spherical aberration(△SA),and variation of Q-value(△Q,all P<0.001)in both groups.Multiple variable linear regression equations were△FOZ=1.354-0.1×pre-SE+0.336×△Q+1.462×△SA in SMILE group and△FOZ=1.512+0.137×△Q+0.468×△SA in FS-LASIK group.CONCLUSION:AFOZ is significantly smaller than preoperative FOZ in both SMILE and FS-LASIK groups.With the same PFOZ,larger AFOZ is achieved in SMILE group than in FS-LASIK group.

0.05% atropine on control of myopia progression in Chinese school children: a randomized 3-year clinical trial

·AIM:To evaluate the effect of 0.05%atropine on the control of myopia for 2y(phase I)and on spherical equivalent refraction(SER)progression for 1y(phase II)after its withdrawal in Chinese myopic children.·METHODS:Totally 142 children with myopia were randomly assigned to the 0.05%atropine group or to the placebo group.In phase I,children received 1 treatment for each eye daily.In phase II,the patients received no treatment.Axial length(AL),SER,intraocular pressure(IOP)and atropine-related side effects were assessed at 6 months’intervals.·RESULTS:During phase I,the mean change of SER was-0.46±0.30 D in the atropine group,compared to-1.72±1.12 D in the placebo group(P<0.001).The mean change of AL in the atropine group(0.26±0.30 mm)was significantly shorter than that in the placebo group(0.76±0.62 mm,P=0.002).In addition,in phase II(12mo after the withdrawal of atropine),there was no significant difference in AL change from the atropine group,when compared with that from the placebo group(0.31±0.25 mm vs 0.28±0.26 mm,P>0.05).Furthermore,the change in SER from the atropine group was 0.50±0.41 D,which was significantly lower than 0.72±0.60 D from placebo group,(P<0.05).Finally,there were no statistically significant differences in IOP between the treatment and control groups at any stages(all P>0.05).·CONCLUSION:The use of 0.05%atropine for two consecutive years may effectively control elongation of AL and thus progression of myopia,without significant SER progression 1y after atropine withdrawal.Therefore,treatment with 0.05%atropine daily for 2y is effective and safe.

The evolution of refractive status in Chinese infants during the first year of life and its affected factors

AIM： To study the evolution of the refractive status and examine the affected factors in infants during the first year of life in a large sample size in China. METHODS： A total of 1258 babies （2516 eyes） aged 32wk gestational age to ty participated in the study, including 766 premature and 492 full-term infants. First, each baby received an orthoptic examination, slit-lamp checking and fundus imaging. Patients with diseases which might affect refractive status were excluded from the cohort. The cycloplegia retinoscopy was performed. Their neonatal histories were reviewed. Each measurement contained the refractive status and calculation of the spherical equivalent （SE）. RESULTS： Refractive state showed an average hyperopia of ＋0.94_＋1.63 D at early ages, followed by a trend toward more hyperopia. The refractive state reached the top （＋2.431.46 D） at the age of one to two months. Then gliding till one year old when the refractive state reached ＋0.59：1.41 D. The prevalence of astigmatism was 42.17% in the study, being 2.82% myopic astigmatism and 39.35% hyperopic astigmatism. The 94.1% of hyperopic astigmatism was with-the-rule astigmatism and 71.83% of myopic astigmatism was with-the-rule astigmatism. Refractive state between boys and girls was different. The mean SE of boys was ＋1.97＋1.57 D, while that of girls was ＋1.79＋1.46 D, and the difference was significant. CONCLUSION： Before one year old, the change of refractive status is associated with checking age and sex. At the age of one to two months, the degree of hyperopia reaches the top. Boys have more hyperopic degree than girls, and with- the-rule astigmatism is predominant. Excluding premature infants with advanced retinopathy of prematurity, premature and full-term children have same refraction status.

Comparison between two autorefractor performances in large scale vision screening in Chinese school age children

AIM:To evaluate the effectiveness of Grand Seiko Ref/Keratometer WAM-5500 compared to Topcon KR800 autorefractor in detecting refractive error in large scale vision screening for Chinese school age children with the WHO criteria.METHODS:A total of 886 participants were enrolled with mean age of 9.49±1.88 y from Tianjin,China.Spherical equivalent(SE)was obtained from un-cycloplegic autorefraction and cycloplegic autorefraction.Topcon KR 800(Topcon)and Grand Seiko WAM-5500(WAM)autorefractors were used.Bland-Altman Plot and regression were generated to compare their performance.The overall effectiveness of detecting early stage refractive error was analyzed with receiver operating characteristic(ROC)curves.RESULTS:The mean SE was-0.98±1.81 diopter(D)and the prevalence of myopia was 48.9%defined by WHO criteria according to the result of cycloplegic autorefraction.The mean SE of un-cycloplegic autorefraction with Topcon and WAM were-1.21±1.65 and-1.20±1.68 D respectively.There was a strong linear agreement between result obtained from WAM and cycloplegic autorefraction with an R2 of 0.8318.Bland-Altman plot indicated a moderate agreement of cylinder values between the two methods.The sensitivity and specificity for detecting hyperopia were 90.52%and 83.51%;for detecting myopia were 95.60%and 90.24%;for detecting astigmatism were 79.40%and 90.21%;for detecting high myopia were 98.16%and 98.91%respectively.CONCLUSION:These findings suggest that both Grand Seiko and Topcon autorefractor can be used in large-scale vision screening for detecting refractive error in Chinese population.Grand Seiko gives relatively better performance in detecting myopia,hyperopia,and high myopia for school age children.

Short-term effect of 0.01% atropine sulphate eye gel on myopia progression in children

AIM: To investigate the effect of 0.01% atropine sulphate eye gel on myopia progression and axial elongation in a 6-month treatment in children.METHODS: Totally 185 children aged 6-12 y with binocular myopia of 3.0 D or less in both eyes were enrolled in this prospective cohort study. The atropine group(n=125) received one drop of 0.01% atropine sulphate eye gel in each eye before bedtime daily. The control group included 60 matched children without drug intervention during the same period. The spherical equivalent and axial length was recorded at baseline and the sixth month of treatment. The efficacy was evaluated by the change of the spherical equivalent and axial length. Adverse events were also recorded.RESULTS: The average spherical equivalent and axial length at baseline were not statistically significant between the atropine group(-1.64±0.80 D, 24.13±0.76 mm) and the control group(-1.59±0.94 D, 24.06±0.77 mm, P>0.05). After 6 mo, there was significantly difference in the spherical equivalent progression between the atropine and the control group(-0.27±0.33 vs-0.60±0.35 D, P<0.001),with a relative reduction of 55.0% in myopia progression. The increase in axial elongation in the atropine group was significantly less than control group(0.19±0.14 vs 0.26±0.14 mm, P<0.001), with a relative reduction of 26.9% in axial length. The 84.4% and 38.4% of the eyes progressed by less than 0.50 D and remained stable in the atropine group, compared with 51.7% and 4.2% in the control group. No adverse events were observed.CONCLUSION: Atropine sulphate eye gel 0.01% can slow down myopia progression and axial elongation in children with a 6-month treatment.

WHU-Grace01s:A new temporal gravity field model recovered from GRACE KBRR data alone

A new temporal gravity field model called WHU-Grace01s solely recovered from Gravity Recovery and Climate Experiment （GRACE） K-Band Range Rate （KBRR） data based on dynamic integral approach is presented in this paper. After meticulously preprocessing of the GRACE KBRR data, the root mean square of its post residuals is about 0.2 micrometers per second, and seventy-two monthly temporal solutions truncated to degree and order 60 are computed for the period from January 2003 to December 2008. After applying the combi- nation filter in WHU-Grace01s, the global temporal signals show obvious periodical change rules in the large-scale fiver basins. In terms of the degree variance, our solution is smaller at high degrees, and shows a good consistency at the rest of degrees with the Release 05 models from Center for Space Research （CSR）, GeoForschungsZentrum Potsdam （GFZ） and Jet Pro- pulsion Laboratory 0PL）. Compared with other published models in terms of equivalent water height distribution, our solution is consistent with those published by CSR, GFZ, JPL, Delft institute of Earth Observation and Space system （DEOS）, Tongji University （Tongji）, Institute of Theoretical Geodesy （ITG）, Astronomical Institute in University of Bern （AIUB） and Groupe de Recherche de Geodesie Spatiale （GRGS}, which indicates that the accuracy of WHU-Grace01s has a good consistency with the previously published GRACE solutions.

Correcting magnification error in foveal avascular zone area measurements of optical coherence tomography angiography images with estimated axial length

Background:To generate and validate a method to estimate axial length estimated(AL_(est))from spherical equivalent(SE)and corneal curvature[keratometry(K)],and to determine if this AL_(est)can replace actual axial length(AL_(act))for correcting transverse magnification error in optical coherence tomography angiography(OCTA)images using the Littmann-Bennett formula.Methods:Data from 1301 participants of the Raine Study Gen2-20 year follow-up were divided into two datasets to generate(n=650)and validate(n=651)a relationship between AL,SE,and K.The developed formula was then applied to a separate dataset of 46 participants with AL,SE,and K measurements and OCTA images to estimate and compare the performance of AL_(est)against AL_(act)in correcting transverse magnification error in OCTA images when measuring the foveal avascular zone area(FAZA).Results:The formula for AL_(est)yielded the equation:AL_(est)=2.102K−0.4125SE+7.268,R^(2)=0.794.There was good agreement between AL_(est)and AL_(act)for both study cohorts.The mean difference[standard deviation(SD)]between FAZA corrected with AL_(est)and AL_(act)was 0.002(0.015)mm^(2)with the 95%limits of agreement(LoA)of−0.027 to 0.031 mm^(2).In comparison,mean difference(SD)between FAZA uncorrected and corrected with AL_(act)was−0.005(0.030)mm^(2),with 95%LoA of−0.064 to 0.054 mm^(2).Conclusions:AL_(act)is more accurate than AL_(est)and hence should be used preferentially in magnification error correction in the clinical setting.FAZA corrected with AL_(est)is comparable to FAZA corrected with AL_(act),while FAZA measurements using images corrected with AL_(est)have a greater accuracy than measurements on uncorrected images.Hence,in the absence of AL_(act),clinicians should use AL_(est)to correct for magnification error as this provides for more accurate measurements of fundus parameters than uncorrected images.

Retinal structural-vascular-functional relationship using optical coherence tomography and optical coherence tomography -angiography in myopia

Background:To examine the retinal structure–vascular-function relationship using optical coherence tomography(OCT)and optical coherence tomography angiography(OCTA)in myopia.Methods:This was a prospective cross-sectional study comprising 86 eyes of 45 individuals with varying axial lengths and spherical equivalents and no posterior segment abnormalities.All eyes underwent optical coherence tomography with the Spectralis SD-OCT and OCTA with RTVue-XR Avanti;Optovue.Individual macular retinal layer thicknesses and flow areas and vessel densities were measured on OCT and OCTA,respectively.Linear correlations were made between the macular layer thicknesses,flow areas and vessel densities with axial length,spherical equivalent and visual acuity.Results:The participants’mean ages were 33.34±14.45 years,mean spherical equivalent refractions were−7.17±5.71 D and axial lengths were 25.95±2.41 mm.There were significant positive correlations of foveal angle(r=0.757,p=0.001),inner retinal(r=0.764,p=0.001)and outer plexiform layer(r=0.771,p=0.001)thickness on OCT and vessel densities in deep capillary plexus(r=0.313,p=0.003)on OCTA with axial length and negative correlations with spherical equivalents and visual acuity.Significant negative correlations of outer nuclear layer(r=−0.560,p=0.03)and photoreceptor outer segment layer thickness(r=−0.856,p<0.001)were noted on OCT with axial length and positive correlations with spherical equivalents and visual acuity.Conclusion:The lateral retinal stretching in myopia could possibly explain the correlation between retinal layer thickness,vascular density and visual acuity in these eyes.Further research is required to investigate this.