Evaluation of refractive correction for standard automated perimetry in eyes wearing multifocal contact lenses

AIM：To evaluate the refractive correction for standard automated perimetry（SAP）in eyes with refractive multifocal contact lenses（CL）in healthy young participants.METHODS：Twenty-nine eyes of 29 participants were included.Accommodation was paralyzed in all participants with 1%cyclopentolate hydrochloride.SAP was performed using the Humphrey SITA-standard 24-2 and 10-2 protocol under three refractive conditions：monofocal CL corrected for near distance（baseline）;multifocal CL corrected for distance（m CL-D）;and m CL-D corrected for near vision using a spectacle lens（m CL-N）.Primary outcome measures were the foveal threshold,mean deviation（MD）,and pattern standard deviation（PSD）.RESULTS：The foveal threshold of m CL-N with both the24-2 and 10-2 protocols significantly decreased by 2.2-2.5 d B（P〈0.001）,while that of m CL-D with the 24-2 protocol significantly decreased by 1.5 d B（P=0.0427）,as compared with that of baseline.Although there was no significant difference between the MD of baseline and m CL-D with the24-2 and 10-2 protocols,the MD of m CL-N was significantly decreased by 1.0-1.3 d B（P〈0.001）as compared with that of both baseline and m CL-D,with both 24-2 and 10-2 protocols.There was no significant difference in the PSD among the three refractive conditions with both the 24-2 and 10-2 protocols.CONCLUSION：Despite the induced mydriasis and the optical design of the multifocal lens used in this study,our results indicated that,when the dome-shaped visual field test is performed with eyes with large pupils and wearing refractive multifocal CLs,distance correction without additional near correction is to be recommended.

Collagen cross-linking for pediatric refractive correction

Corneal collagen-crosslinking(CXL)has been widely investigated in the adult population.There is still little available in the literature,however,on the effects of CXL in children.A review of the literature on CXL in the pediatric population is presented here,with a particular emphasis on the refractive effects.Although several studies demonstrate promising results,most studies have small sample sizes with relatively short follow-up periods.Further investigation on the effects of CXL in the pediatric population is required to better understand long-term effects.

Human eye ocular component analysis for refractive state and refractive surgery

AIM： To analyze the clinical factors influencing the human vision corrections via the changing of ocular components of human eye in various applications; and to analyze refractive state via a new effective axial length.METHODS： An effective eye model was introduced by the ocular components of human eye including refractive indexes, surface radius（r1, r2, R1, R2） and thickness（t, T） of the cornea and lens, the anterior chamber depth（S1） and the vitreous length（S2）. Gaussian optics was used to calculate the change rate of refractive error per unit amount of ocular components of a human eye（the rate function M）. A new criterion of myopia was presented via an effective axial length.RESULTS： For typical corneal and lens power of 42 and 21.9 diopters, the rate function Mj（j=1 to 6） were calculated for a 1% change of r1, r2, R1, R2, t, T（in diopters） M1=＋0.485, M2=-0.063, M3=＋0.053, M4=＋0.091, M5=＋0.012, and M6=-0.021 diopters. For 1.0 mm increase of S1 and S2, the rate functions were M7=＋1.35, and M8=-2.67 diopter/mm, respectively. These rate functions were used to analyze the clinical outcomes in various applications including laser in situ keratomileusis surgery, corneal cross linking procedure, femtosecond laser surgery and scleral ablation for accommodation.CONCLUSION： Using Gaussian optics, analytic formulas are presented for the change of refractive power due to various ocular parameter changes. These formulas provide useful clinical guidance in refractive surgery and other related procedures.

Epidemiology, genetics and treatments for myopia

Myopia is a significant public health problem and its prevalence is increasing over time and genetic factors in disease development are important. The prevalence and incidence of myopia within sampled population often varies with age, country, sec race, ethnicity, occupation, environment, and other factors. Myopia growth is under a combination of genes and their products in time and space to complete the coordination role of the guidance. Myopia-related genes include about 70 genetic loci to which primary myopias have been mapped, although the number is constantly increasing and depends to some extent on definition. Of these, several are associated with additional abnormalities, mostly as part of developmental syndromes. These tend to result from mutations in genes encoding transcriptional activators, and most of these have been identified by sequencing candidate genes in patients with developmental anomalies. Currently, collagen alpha-1 chain of type I(COL1A1), collagen alpha-1 chain of type II(COL2A1), actin, alpha, cardiac muscle 1 (ACTC1), paired box gene 6 (PAX6) and NIPBL (nipped-B homolog), and so on have been mapped. Myopia is most commonly treated with spectacles or glasses. The most common surgical procedure performed to correct myopia is laser keratomileusis (LASIK). This review of the recent advances on epidemiology, genetic locations and treatments of myopia are summarized.

Presbyopic correction on the cornea

Purpose:The aim of this systematic review was to synthesize and appraise the evidence of the benefits of presbyopic correction on the cornea for visual function.Summary:Comprehensive search was conducted in MEDLINE using keywords like“presbylasik”,“presbyopic refractive surgery”,“corneal pseudoaccommodation”and“corneal multifocality”.We reviewed corrected and uncorrected visual acuities for distance and near(uncorrected distance visual acuity(UDVA),uncorrected near visual acuity(UNVA),corrected distance visual acuity(CDVA),distance corrected near visual acuity(DCNVA),corrected near visual acuity(CNVA)),along with the refractive outcomes in spherical equivalent(SE)and astigmatism comparing the differences observed between preoperative myopic and hyperopic patients,as well as among techniques.Thirty-one studies met the inclusion and quality criteria.Monovision provides excellent distance and near uncorrected acuities,but with a 17%retreatment and a 5%reversal rate.Initial multifocal ablations result in 12%loss of 2 or more lines of CDVA,and a 21%retreatment rate.Laser Blended Vision provides excellent UDVA,but with a 19%retreatment rate.Initial experiences with Supracor show moderate predictability and a 22%retreatment rate.Intracor results in 9%loss of 2 or more lines of CDVA.KAMRA provides excellent UDVA,with only a 1%retreatment rate,but a 6%reversal rate.Initial experiences with PresbyMAX provided excellent UNVA and DCNVA,showing excellent predictability and a 1%reversal rate.Conclusions:The findings have implications for clinicians and policymakers in the health-care industry and emphasize the need for additional trials examining this important and widely performed clinical procedure.

Role of refractive index in sum frequency generation intensity of salt solution interfaces

Sum frequency generation spectroscopy（SFG） has been widely used to study the interfacial chemistry of aqueous salt solutions of biological or environmental importance. Most of the SFG data analysis used the same bulk refractive index for different salt concentrations despite of the variations of the refractive indices. Here we systematically investigate the influence of the refractive index on the SFG intensities at various experimental conditions. It is discovered that the SFG intensities are the most sensitive to the refractive index at solid/liquid interfaces nearby the total internal reflection geometries. At air/liquid interfaces, the effect of the refractive indices is also nonegligible. Consequently some important SFG results, such as the response of water structures to the ionic strength at the SiO2/aqueous interfaces, are necessary to be reevaluated. These conclusions on the effect of the small variations of the refractive index are generally useful for the common practice of SFG data analysis.

Imaging of echo data of submarine sedimentary beds layer-by-layer with acoustic wave equation refraction correction method

Wide-angle echo data of submarine sedimentary beds are collected by a system composed of a seismic profiler and a hydrophone streamer towed behind the profiler. Usually the wide-angle echo data are processed with common-depth-point stack method to obtain the stacked section for gcological interpretation. When the acoustic velocity of the sedimentary layers has a lateral variation, the stacked section does not represent the real structure of sedimentary layers. Based on this stacked section, we would probably draw a false conclusion.In case of knowing the acoustic velocity of sedimentary beds, we may remove the distortions caused by acoustic velocity lateral variations from the stacked section with acoustie wave equation Kirchhoff integration which continues the wave fields in downgoing and upgoing directions respectively. Thus the accurate image of the structure of submarine sedimentary layers is obtained.