Fabrication of UV-Curing Linalool-Polysiloxane Hybrid Films with High Refractive Index and Transparency

In this article,a series of high refractive indices(1.50-1.53)thiol phenyl polysiloxane(TPS)were synthesized via hydrolytic sol-gel reaction.The Fourier transform infrared spectra(FT-IR)and nuclear magnetic resonance spectra(NMR)results showed that TPS conformed to the predicted structures.Natural terpene linalool was exploited as photocrosslinker to fabricate UV-curing linalool-polysiloxane hybrid films(LPH)with TPS via photoinitiated thiol-ene reaction.LPH rapidly cured under UV irradiation at the intensity of 80 mW/cm2 in 30 s,exhibiting good UV-curing properties.The optical transmittance of LPH in the wavelength of 300-800 nm was over 90%,exhibiting good optical transparency.The water contact angle and water vapor permeability results showed that the introduction of phenyl groups enhance the hydrophobicity and water vapor barrier properties of LPH.The results indicated the potential of LPHs in the applications of optical functional coatings.

A 3-month comparison study of subjective and objective visual quality of small incision lenticule extraction and transepithelial photorefractive keratectomy in patients with low and moderate myopia

AIM:To compare the subjective and objective visual quality between small incision lenticule extraction(SMILE)and transepithelial photorefractive keratectomy(t PRK)in patients with low and moderate myopia.METHODS:Patients undertaking SMILE or t PRK for the correction of low and moderate myopia were consecutively recruited in this prospective cohort study with a 3-month follow-up period.Objective evaluation[visual acuity test,manifest refraction,wavefront aberrations,the total cut-off value of the total modulation transfer function(MTFcut-off),and Strehl ratio(SR)]and subjective evaluation of visual quality(quality-of-life questionnaire)were conducted before surgery and at days 1,7,30,and 90 after surgery.RESULTS:A total of 47 patients(94 eyes)with SMILE and 22 patients(22 eyes)with t PRK were enrolled.The uncorrected visual acuity(UCVA)was better in SMILE patients on day 7 after surgery(1.13±0.13 vs 0.99±0.17,t=4.85,P<0.001)but was comparable at days 30 and 90.At day 90,the SMILE group had a lower spherical equivalent(SE)than the t PRK group(0.04±0.31 vs 0.19±0.43,t=2.08,P=0.042).Total higher order aberrations(HOAs)were induced in both surgical types,which were more evident in the t PRK group with 3-mm pupil diameter(0.16±0.07 vs0.11±0.05,t=4.27,P<0.001)and 5-mm pupil diameter(0.39±0.17 vs 0.36±0.11,t=2.33,P=0.022).The MTFcut-offand SR showed a trend of improvement in both SMILE and t PRK patients but were statistically better in the SMILE group with both pupil diameters.There was a significant improvement of contrast sensitivity(CS)over baseline levels at the spatial frequency of 18 cycles/degree(c/d)in the SMILE group(F=2.72,P=0.033)and at 3 c/d(F=3.03,P=0.031),12 c/d(F=3.72,P=0.013),and 18 c/d(F=4.62,P=0.004)in the t PRK group.The subjective quality of life questionnaire showed a steady improvement in the SMILE group(F=8.31,P<0.001)but not the t PRK group.CONCLUSION:SMILE and t PRK are both safe and effective ways to correct low and moderate myopia.A generally better and quicker recovery of visual quality favors the application of SMILE in qualified patients.

Uncorrected refractive errors are important causes of avoidable visual impairment in Hungary: re-evaluation of two existing national data sets

·AIM: To review existing data for the prevalence of corrected, uncorrected, and inadequately corrected refractive errors and spectacle wear in Hungary.·METHODS: Data from two nationwide cross-sectional studies were analysed. The Rapid Assessment of Avoidable Blindness study collected population-based representative national data on the prevalence of visual impairment due to uncorrected refractive errors and spectacle coverage in 3523 people aged ≥50y(Group I). The Comprehensive Health Test Program of Hungary provided data on the use of spectacles in 80 290 people aged ≥18y(Group Ⅱ).·RESULTS: In Group I, almost half of the survey population showed refractive errors for distant vision, about 10% of which were uncorrected(3.2% of all male participants and 5.0% of females). The distance spectacle coverage was 90.7%(91.9% in males;90.2% in females). The proportion of inadequate distance spectacles was found to be 33.1%. Uncorrected presbyopia was found in 15.7% of participants. In all age groups(Group Ⅱ), 65.4% of females and 56.0% of males used distance spectacles,and approximately 28.9% of these spectacles were found to be inappropriate for dioptric power(with 0.5 dioptres or more). The prevalence of inaccurate distance spectacles was significantly higher in older age groups(71y and above) in both sexes.·CONCLUSION: According to this population-based data, uncorrected refractive errors are not rare in Hungary. Despite recent national initiatives, fur ther steps are required to reduce uncorrected refractive errors and associated negative effects on vision, such as avoidable visual impairment.

Predictive methods for density and refractive index of naphthenic lubricating oils during solvent extraction process

Lubricating oils are usually produced by solvent extraction to separate aromatics in order to achieve the desired specifications and better quality products.Among the different properties of lubricating oils,density and refractive index are some of the most important properties which can both be used for petroleum fluid characterization.Predictions of density and refractive index for naphthenic oils during solvent extraction by DMSO obtained by the pseudo-component approach and the quadratic correlation were both examined.The pseudo-component approach is a method to predict density and refractive index from composition while the latter merely relates density to refractive index.Results indicated that the predictions yielded by the pseudo-component method were in good agreement with experimental data for naphthenic oils.And the use of a function of refractive index(FRI_(20))as a pseudo-component property remarkably improved n_(20)predictions for the naphthenic mixtures.However,the density and refractive index predictions obtained by the quadratic correlation exhibited significantly higher de-viations for naphthenic oils than those for paraffinic oils.Thus a new modified correlation of the same functional form was proposed for naphthenic oils.The modification significantly improved predictions for naphthenic oils,which presented similar accuracy as the pseudo-component approach.And the previous correlation was still used for paraffinic oils.Additionally,effect of temperature on density and refractive index of naphthenic oils was examined.Results showed that the modified quadratic correlation was accurate for describing the relationship between density and refractive index of naphthenic oils at 20-90℃.The temperature dependence of density and refractive index for the raffinates and the extracts could be accurately described by the thermal coefficients for saturates and aromatics,respectively.Regarding the refractive index variation of the extracts with temperature,the empirical equation was proved to be a better option compared with the method using the thermal coefficient for aromatics.

Prevalence of refractive errors in children of Puerto Rico

AIM:To determine the prevalence of refractive error in 5-to 17-year-old schoolchildren in Puerto Rico.METHODS:A quantitative descriptive study of 2867 children aged 5 to 17y from all seven educational regions of Puerto Rico was conducted from 2016–2019.Refractive error was determined via static and subjective refraction.Children with distance acuity≤20/40 or near visual acuity≤20/32 had a cycloplegic refraction.Data analysis included descriptive statistics,correlation coefficient,Kruskal-Wallis,Chi-square,and t test calculations.RESULTS:Twenty percent of the children had a spherical equivalent refractive error≤-0.50 D,3.2%had a spherical equivalent≥+2.00 D,and 10.4%had astigmatism≥1 D.There was a statistically(but non-clinically)significant myopic change in spherical equivalent refractive error with age(P<0.001).The prevalence of myopia increased with age(P<0.001)but not hyperopia(P=0.59)or astigmatism(P=0.51).Males had a significantly higher hyperopic spherical equivalent than females(P<0.001).Females had a higher prevalence of myopia(P<0.001)than males,but there was no difference in the hyperopia(P=0.74)or astigmatism prevalence(P=0.87).CONCLUSION:The prevalence of a spherical equivalent equal to or less than-0.50 D(myopia,20.7%)is one of the highest among similar-aged children worldwide.Further studies should explore the rate of myopia progression in children in Puerto Rico.Individual children must be monitored to examine the need for treatment of myopia progression.

Axial length,vitreoretinal pathology,and anterior chamber depth can predict postoperative refractive outcomes in phacovitrectomy/silicone oil removal

AIM:To evaluate the postoperative refractive prediction error(PE)and determine the factors that af fect the refractive outcomes of combined pars plana vitrectomy(PPV)or silicone oil removal(SOR)with cataract surgery.METHODS:The study is a retrospective,case-series study.Totally 301 eyes of 301 patients undergoing combined PPV/SOR with cataract surgery were enrolled.Eligible individuals were separated into four groups according to their preoperative diagnoses:silicone oil-filled eyes after PPV(group 1),epiretinal membrane(group 2),macular hole(group 3),and primary retinal detachment(RD;group 4).The variables af fecting postoperative refractive outcomes were analyzed,including age,gender,preoperative best-corrected visual acuity(BCVA),axial length(AL),keratometry average,anterior chamber depth(ACD),intraocular tamponade,and vitreoretinal pathology.The outcome measurements include the mean refractive PE and the proportions of eyes with a PE within±0.50 diopter(D)and±1.00 D.RESULTS:For all patients,the mean PE was-0.04±1.17 D,and 50.17%of patients(eyes)had a PE within±0.50 D.There was a significant difference in refractive outcomes among the four groups(P=0.028),with RD(group 4)showing the least favorable refractive outcome.In multivariate regression analysis,only AL,vitreoretinal pathology,and ACD were strongly associated with PE(all P<0.01).Univariate analysis revealed that longer eyes(AL>26 mm)and a deeper ACD were correlated with hyperopic PE,and shorter eyes(AL<26 mm)and a shallower ACD were correlated with myopic PE.CONCLUSION:RD patients have the least favorable refractive outcome.AL,vitreoretinal pathology,and ACD are strongly associated with PE in the combined surgery.These three factors affect refractive outcomes and thus can be used to predict a better postoperative refractive outcome in clinical practice.

Design of a coated thinly clad chalcogenide long-period fiber grating refractive index sensor based on dual-peak resonance near the phase matching turning point

A novel method for designing chalcogenide long-period fiber grating(LPFG) sensors based on the dual-peak resonance effect of the LPFG near the phase matching turning point(PMTP) is presented. Refractive index sensing in a high-refractive-index chalcogenide fiber is achieved with a coated thinly clad film. The dual-peak resonant characteristics near the PMTP and the refractive index sensing properties of the LPFG are analyzed first by the phase-matching condition of the LPFG. The effects of film parameters and cladding radius on the sensitivity of refractive index sensing are further discussed. The sensor is optimized by selecting the appropriate film parameters and cladding radius. Simulation results show that the ambient refractive index sensitivity of a dual-peak coated thinly clad chalcogenide LPFG at the PMTP can be 2400 nm/RIU, which is significantly higher than that of non-optimized gratings. It has great application potential in the field of chemical sensing and biosensors.

Residual refractive errors in pseudophakic eyes and related factors:a population-based study

AIM: To determine residual refractive error after cataract surgery in pseudophakic eyes and its relationship with age, sex, and axial length(AL).METHODS: In this population-based cross-sectional study, the sampling was performed on individuals aged 60y and above in Tehran, Iran using a multi-stage stratified random cluster sampling method. Pseudophakic eyes with a best-corrected visual acuity of 20/32 or better were analyzed and their refractive results were reported.RESULTS: The mean spherical equivalent(SE) refraction was-0.34±0.97 diopters(D) and the mean absolute SE was 0.72±0.74 D with a median of 0.5 D. Moreover, 32.68%(n=546, 95%CI: 30.27%-35.08%), 53.67%(n=900, 95%CI: 51.23%-56.1%), 68.99%(n=1157, 95%CI: 66.96%-71.02%), and 79.73%(n=1337, 95%CI: 77.69%-81.76%) of the eyes had a residual SE within ±0.25, ±0.50, ±0.75, and ±1.00 D of emmetropia, respectively. According to the multiple logistic regression model, increasing age was associated with a statistically significant decrease in predictability for all cut points. Moreover, the predictability based on all cut points was significantly lower in individuals with an AL longer than 24.5 mm than in those with an AL between 22 to 24.5 mm.CONCLUSION: Based on the results, the accuracy of intraocular lens(IOL) power calculation is lower for those who underwent cataract surgery during the last 5y in Tehran, Iran. Among the most important influential factors, the choice of IOL or it's power disproportionate to eye conditions and age can be mentioned.

Bibliometric analysis of research relating to refractive cataract surgery over a 20-year period:from 2003 to 2022

AIM:To investigate the research trend on refractive cataract surgery,compare the contributions of different countries,institutions,journals,and authors in the past 20y,and explore its potential research hotspots.METHODS:All publications were extracted relating to refractive cataract surgery from 2003 to 2022 from Web of Science.Document types were limited to original articles and reviews,and the language was limited to English.Quantitatively and qualitatively of the publications were analyzed through Microsoft Excel and GraphPad Prism.VOSviewer and CiteSpace were used for bibliometric and visualized analysis.RESULTS:A total of 2090 publications were enrolled.The United States contributed the most publications(434,20.8%),followed by China(345,16.5%)and England(163,7.80%).Publications from the United States were cited more frequently(9552 citations)with the highest H-index of 48.China ranked second in the total number of publications,the papers were not cited that frequently(3237 citations),and the H-index ranked sixth(H-index=29).Journal of Cataract and Refractive Surgery published the most papers(333,15.9%),and the University of London had the highest number of publications(75,3.59%).Dick HB from Germany published the most papers.Corneal astigmatism-related research,cataract surgery methodrelated research,postoperative visual-quality relate to research,and postoperative complications-relate research are the hotspots in this field.The most significant limitation was that the database was updated frequently and the latest publications were not included.CONCLUSION:The bibliometric analysis shows a brief summarization of the contribution of the authors,institutions,countries,and journals.Corneal astigmatism,cataract surgery method,postoperative visual-quality and postoperative complications related researches have become the emerging hotspots,which can give a direction in the future researches.

Refractive State and Macular Abnormalities at Oct in Albino at Chu Iota

Introduction: A rare genetic disease, albinism is globally characterized by specific deficits of the visual system associated with a variable hypopigmentation phenotype depending on the disruption of melanin production [1]. It is linked to a hereditary defect in the biosynthesis of melanin. Disease results in a generalized decrease in the pigmentation of the appendages, skin and eyes [2]. The aim of this study is to determine the different refractive errors and the different macular anomalies during the OCT examination in oculocutaneous albinism at the CHU-IOTA. Patients and Method: We conducted a prospective study in patients over 10 years of age with oculocutaneous or ocular albinism who consulted at the CHU-IOTA between July 1, 2020, and September 30, 2021. Results: Over the period, 105 cases of oculocutaneous albinism were collected out of a total of 42,024 consultations, which corresponds to a frequency of 0.2%. The average age was 26.2 years, (11 years to 48 years). The sex ratio was 1.6. Astigmatism was the most found refractive error in 50.48% of cases, followed by myopia in 29.52% of cases and farsightedness in 20% of cases. The macular thickness between 251 - 350 was the most commonly found in both eyes, i.e. 47.25% on the right and 53.55% on the left. The bulging macula was the most frequent pathology on the OCT at the level of the two eyes, i.e. 41.42% on the right and 50.6% on the left. Conclusion: Following the visual impairments linked to albinism, early optical care and access to OCT are necessary. Thus the accompaniment of a subject with albinism and associations of albinism must be global and meet specific needs, in order to prevent or avoid ocular complications.

The Refractive Effect of k-Factor on Radio Propagation over Lokoja, Nigeria

The effective earth radius factor(k-factor)has a refractive propagation effect on transmitted radio signals thus making its study necessary for the proper planning of terrestrial radio links and power budget.This study was carried out over the city of Lokoja,Nigeria,using ten years(2011 to 2020)atmospheric data of temperature,pressure and humidity both at the surface(12 m)and at 100 m AGL.The data were retrieved from European Centre for Medium-Range Weather Forecasts(ECMWF)ERA5.The k-factor yearly variation follows the same trend with minimum and maximum values obtained during dry and wet season months respectively.In addition,the highest mean value of 1.00042 was recorded in the month of August while the lowest value of 1.00040 was recorded in the month of January with an overall mean value of 1.0003.This value is less than the recommended standard of 1.33 by ITU-R.The propagation effect corresponding to k<1.33 is sub-refractive.The implication of this on radio wave propagation,especially terrestrial communications is that transmitted wireless signal is prone to losses.This can be mitigated through an effective power budget:Choice of transmitting antenna’s height and gain,so as to improve the Quality of Service over the study area.

Corneal re-innervation following refractive surgery treatments

Laser refractive surgery is one of the most performed surgical procedures in the world. Although regarded safe and efficient, it has side effects. All of the laser based refractive surgical procedures invoke corneal nerve injury to some degree. The impact of this denervation can range from mild discomfort to neurotrophic corneas. Currently, three techniques are widely used for laser vision correction: small incision lenticule extraction, laser-assisted keratomileusis in situ and photorefractive keratotomy. Each of these techniques affects corneal innervation differently and has a different pattern of nerve regeneration. The purpose of this review is to summarize the different underlying mechanisms for corneal nerve injury and compare the different patterns of corneal reinnervation.

Refractive surgery: the most cost-saving technique in refractive errors correction

AIM: To compare the lifetime and annual economic burden of spectacles, contact lenses, and refractive surgery in correction of refractive errors.METHODS: This is a cross-sectional study with convenience sampling which 120 patients were interviewed in a tertiary referral hospital in the Iranian health care system. The bottom-up based cost of illness approach was estimated using a face-to-face interview to assess the direct and indirect cost of different refractive errors correction of any correction technologies.RESULTS: Correction with spectacle imposes a total direct cost of US dollar(US$) 342.5(±8.41) per year and US$9373.5(±230.1) per lifetime to each patient. These figures for the contact lenses were obtained US$198.3(±0.12) and US$5203.1(±256.3) and for refractive surgery were obtained US$19.1(±1.2) and US$568.1(±64.6),respectively. Overall, based on age-adjusted prevalence rates, astigmatism had the highest share of refractive errors economic burden with a lifetime direct cost of slightly less than US$5.49 billion, while hyperopia and myopia imposed less than US$5.24 and 4.2 billion on patients, respectively. The annually imposed cost on each individual Iranian patient with refractive errors is US$308.5.CONCLUSION: Based on 18 mo post refractive surgery course observation, which is generalized to whole life,refractive surgery significantly imposed much less cost compared with spectacles and contact lenses. Refractive errors among Iranians result in considerable economic burden. Using the refractive surgery instead of other two correction methods has the ability to reduce this economic loss in the future.

Transepithelial photorefractive keratectomy for myopia:effect of age and keratometric values

AIM:To investigate demographic and preoperative factors increasing the risk of ametropia following transepithelial photorefractive keratectomy(trans PRK)in myopia and myopic astigmatism.METHODS:This retrospective cohort study included myopic eyes(-0.50 to-8.75 D)with or without astigmatism(up to 3.50 D)enrolled at Dr.Yap Eye Hospital Yogyakarta.Trans PRK was performed using Technolaz 217 z100 excimer laser.Subjects were clustered into ametropia and emmetropia group based on uncorrected distance visual acuities(UDVA)3 mo post-operatively.Multiple preoperative and intraoperative parameters were analyzed using Logistic regression to obtain their effect on ametropia risk following trans PRK.RESULTS:A total of 140 eyes of 87 consecutive subjects were studied.Prevalence of ametropia following trans PRK was 20(14.29%)eyes.Subjects in ametropia group were significantly older than the emmetropia group(31.80±14.23 vs 18.88±2.41,respectively;P<0.001).Bivariate Logistic regression analysis showed that older age(OR=1.23),higher preoperative spherical equivalent(>-6 D;OR=12.78),steeper anterior keratometric readings(Kmax>45 D and mean K>44 D;OR=4.28 and 4.35,respectively)increased the risk of ametropia following trans PRK.Adjusted multivariate Logistic regression analysis showed that age was the strongest predictor for the incidence of ametropia following trans PRK.Complications of trans PRK were overcorrection,suspected posterior keratoectasia and accommodation insuffiency.CONCLUSION:Older age can be the strongest factor for increasing ametropia risk following trans PRK.Cut-off points of Kmax and mean K at 45 and 44 D respectively are proposed as the predictors for ametropia following trans PRK.

Factors affecting single-step transepithelial photorefractive keratectomy outcome in the treatment of mild,moderate,and high myopia:a cohort study

AIM:To investigate the effect of preoperative factors on visual acuity,higher-order aberrations(HOAs),and index of success for spherical change(S.IOS)after transepithelial photorefractive keratectomy(t-PRK)for treating different grades of myopia.METHODS:This was a retrospective one-armed cohort study where patients with high,moderate,or mild myopia treated with single-step t-PRK using Amaris 500 Hz excimer laser were evaluated for visual acuity,refractive status,corneal topography,HOAs,S.IOS,and mean efficiency and safety index before and 6 mo after surgery.RESULTS:A total of 154 eyes of 77 patients with mild(n=59),moderate(n=83),and high(n=12)myopia were reviewed.The efficiency and safety indices for vision recovery by single-step t-PRK were 98%and 100%,respectively.The achieved spherical equivalent(SE)was within 1 diopter(D)in 151(98%)eyes.The median of the S.IOS was 1.18[interquartile range(IQR)1.0,1.4].The change in S.IOS was significantly correlated with age(P=0.007),6.5 mm ablation zone(Mann-Whitney U test,P<0.01),and mild and moderate grade of myopia(Kruskal–Wallis test,P<0.001).Trefoil aberration,spherical aberration,and aberration coefficient types of HOA increased significantly(Wilcoxon test,P<0.001)6 mo post-surgery.There was a significant correlation between spherical aberration and aberration coefficient HOAs by myopia grades(P<0.05).CONCLUSION:Single-step t-PRK has promising short-term outcomes for refractive corrections and vision improvement to treat all three grades of myopia.

Refractive surgical corrective options after cataract surgery

Cataract surgery is one of the most commonly performed surgeries among the elderly today.The volume of cataract surgeries has dramatically increased in the past few decades due to technological advancements leading to decreased morbidity,better overall outcomes,and increased expectation for correction of refractive error and spectacle independence after cataract surgery.The number of cataract surgeries is expected to continue to rise with the increase of the elderly population.Thus,accurate predictions of intraocular lens(IOL)power and the ability to correct for any postoperative refractive errors are critical.Despite the improved ability of cataract surgeons to accurately calculate IOL power,postoperative refractive errors still do occur due to various reasons such as imperfect preoperative measurements,toric-lens misalignment,and existing or surgically-induced astigmatism.The aim of this article is to review the various surgical options,including intraocular and corneal refractive surgical approaches,to correct post-operative refractive errors after cataract surgery.

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.

The prevalence of vision impairment and refractive error in 3654 first year students at Tianjin Medical University

AIM:To determine the prevalence of vision impairment(VI)and refractive error in first year university students at the Tianjin Medical University.METHODS:This is a cross-sectional observational cohort study of VI and refractive error among first year university students at the Tianjin Medical University.The first year university students were involved in this study and were given a detailed questionnaire including age,birth date,and spectacle wearing history.A standardized ophthalmologic examination including visual acuity(VA),slit-lamp examination,non-cycloplegic auto-refraction,objective refraction,fundus photography,and examination of their spectacles were recorded.RESULTS:A total of 3654 participants were included in this study.Totally 3436(94.03%) individuals had VI in this population.Totally 150(4.10%) individuals had VI due to ocular disease,including amblyopia,congenital cataract,retinal atrophy or degeneration,strabismus,congenital nystagmus,refractive surgery orthokeratology.Totally 3286(89.93%) subjects had VI due to refractive error.Only 218(5.97%) students were emmetropia.Moreover,refractive error was the main cause for the VI(95.63%).Totally 3242(92.52%) students were myopia and the prevalence of mild,moderate,and high myopia subgroup was 27.05%,44.35%,and 21.26% respectively.Totally 44(1.29%) subjects were hyperopic.The rates of uncorrected visual acuity(UCVA),presenting visual acuity(PVA)and best corrected visual acuity(BCVA)which better than 20/20 in both eyes were 5.65%,22.32% and 82.13% respectively.The rates of correction,under correction and well correction in myopia subjects were 82.73%,84.39% and 15.61%,respectively. CONCLUSION:We present a high prevalence of refractive errors and high rates of under correction refractive error among first year university students.These results may help to promote vision protection work in young adults.

Axial length/corneal radius of curvature ratio and refractive development evaluation in 3-to 4-year-old children: the Shanghai Pudong Eye Study

AIM: To measure and analysis axial length(AL)/corneal radius of curvature(CRC) ratio and other refractive parameters, provide a medical reference range for refractive development evaluation and earlier visual impairment screening of 3 to 4 y kindergarten students.METHODS: Between April and June 2017, a total of 4350 participants aged 3-to 4-year-old(8700 eyes) from 10 cluster random sampling kindergartens in Shanghai, Pudong District were involved. According to the measurement and analysis of the unaided visual acuity(VA), AL, CRC, AL/CRC ratio, astigmatism and other refractive parameters, the data distribution and reference range were obtained.RESULTS: Uncorrected VA of examined children was 0.23±0.08(logMAR, mean±SD) [95% confidence interval(CI) range ≤0.36];AL was 22.10±0.79 mm(95%CI 20.55-23.65);CRC was 7.86±0.26 mm(95%CI, 7.35-8.37);AL/CRC ratio was 2.81±0.12(95%CI, 2.57-3.05). The median of astigmatism was-0.5 D, a total of 56.3% had astigmatism <-0.50 D, 85.3%<-1.00 D, 6.7%>-1.50 D;71% were astigmatism with the rule. Eye-specific analyses were conducted. Statistical difference of VA was in right and left eyes. There were no significant differences between two eyes of AL, CRC, AL/CRC ratio and astigmatism(P>0.05).CONCLUSION: VA and AL/CRC ratio reference could be used to assess refractive development in children and screening uncorrected refractive errors or amblyopia. Astigmatism needs to be considered in the diagnosis.

Analysis of changes in crystalline lens thickness and its refractive power after laser in situ keratomileusis

AIM:To evaluate changes in the anterior chamber depth (ACD),crystalline lens thickness (LT) and its refractive power after laser in situ keratomileusis (LASIK).· METHODS:In all cases,the preoperative and postoperative central ACD which were measured with Pentacam,Orbscan,IOL-Master and A-scan ultrasonography,central corneal true net power which was measured with the Pentacam,Orbscan and IOL-Master,axial length (AL) which was measured with IOL-Master and LT which was measured with the A-scan ultrasonography were compared using the paired sample t test.Ocular refractive errors and lens refractive power at corneal plane were calculated and their correlations were also evaluated before and after LASIK. RESULTS:At 1 week after LASIK,LT and crystalline lens refractive power at corneal plane (Dlens) which were associated with the IOL-Master and Pentacam increased significantly (P ≤0.005),ACD decreased significantly(P ≤0.001),but no significant increase was observed in the Dlens which was associated with the Orbscan(P =0.261).Significant correlations between the changes in the ocular refractive errors and Dlens which were associated with the Pentacam were observed at 1 week and 6 months after LASIK (P=0.028;P =0.001).CONCLUSION:LT increased significantly after LASIK,and this might partially lead to ACD decrease,Dlens increase and a small quantity of myopic regression.