A total of 403 children were prescribed HAL (n = 296) or DIMS (n = 107) lenses within the study period. There were 193 of 296 (65%) children in the HAL group and 64 of 107 (60%) children in the DIMS group who met the inclusion criteria for the final analyses. There were missing values of axial length (AL) for some observations, leaving 102 in the HAL group and 33 in the DIMS group with complete data for the sensitivity analyses. The distributions of baseline prescription dates were comparable between the two groups. The peaks of starting dates were in October 2020 and January to February 2021 (Fig. 1).

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Lim, M. C., Gazzard, G., Sim, E. L., Tong, L. & Saw, S. M. Direct costs of myopia in Singapore. Eye (Lond) 23, 1086–1089. https://doi.org/10.1038/eye.2008.225 (2009).

First publicly proposed in 1959 by Jacques Fahrenfort from the Royal Dutch Shell laboratories in Amsterdam, ATR IR spectroscopy was described as a technique to effectively measure weakly absorbing condensed phase materials. In Fahrenfort's first article describing the technique, published in 1961, he used a hemicylindrical ATR crystal (see Experimental Conditions) to produce single-reflection ATR (Figure \(\PageIndex{5}\) ). ATR IR spectroscopy was slow to become accepted as a method of characterization due to concerns about its quantitative effectiveness and reproducibility. The main concern being the sample and ATR crystal contact necessary to achieve decent spectral contrast. In the late 1980’s FTIR spectrometers began improving due to an increased dynamic range, signal to noise ratio, and faster computers. As a result ATR-FTIR also started gaining traction as an efficient spectroscopic technique. These days ATR accessories are often manufactured to work in conjunction with most FTIR spectrometers.

The two types of lenses both produce myopic defocus in the peripheral retina while maintaining a clear central vision. The two separate studies showed comparable effects of spectacles lenses with HAL or DIMS for preventing myopia progression. Since there are notable differences in the design of the lenses, we aimed to compare the myopia control efficacy between these two types of lenses.

Holden, B. A. et al. Global prevalence of myopia and high myopia and temporal trends from 2000 through 2050. Ophthalmology 123, 1036–1042. https://doi.org/10.1016/j.ophtha.2016.01.006 (2016).

Generally, dispersive spectrometers have a double-beam design with two equivalent beams from the same source passing through the sample and reference chambers as independent beams. These reference and sample beams are alternately focused on the detector by making use of an optical chopper, such as, a sector mirror. One beam will proceed, traveling through the sample, while the other beam will pass through a reference species for analytical comparison of transmitted photon wavefront information.

Lam, C. S. Y. et al. Defocus incorporated multiple segments (DIMS) spectacle lenses slow myopia progression: a 2-year randomised clinical trial. Br. J. Ophthalmol. 104, 363–368. https://doi.org/10.1136/bjophthalmol-2018-313739 (2020).

The MiDAR transmitter emits coded narrowband structured illumination to generate high-frame-rate multispectral video, perform real-time radiometric calibration, ...

Traditionally, UV film photography has been carried out with UV-pass filters consisting of one of several types of ionic glass. This includes, for instance, the ...

In contrast, when OPD is the half wavelength or half wavelength add multiples of wavelength, destructive interference occurs because crests overlap with troughs. Consequently, a minimum intensity signal is observed by the detector. This situation can be described by the following equation:

Typically an ATR attachment can be used with a traditional FTIR where the beam of incident IR light enters a horizontally positioned crystal with a high refractive index in the range of 1.5 to 4, as can be seen in Table \(\PageIndex{2}\) will consist of organic compounds, inorganic compounds, and polymers which have refractive indices below 2 and can readily be found on a database. The most commonly used crystal is zinc selenide.

To compare spectacle lenses with highly aspherical lenslets (HAL) versus defocus incorporated multiple segments (DIMS) on myopia progression control in 1 year. This retrospective cohort study involved data from children prescribed HAL or DIMS spectacle lenses in Guangzhou Aier Eye Hospital, China. To address the discrepancy that some children followed up at less than or more than 1 year, the standardized 1-year spherical equivalent refraction (SER) and axial length (AL) changes from baseline were calculated. The mean differences in the changes between the two groups were compared with linear multivariate regression models. Age, sex, baseline SER/AL, and treatment were included in the models. A total of 257 children who qualified for the inclusion criteria were included for the analyses (193 in the HAL group and 64 in the DIMS group). After controlling baseline variates, the adjusted mean (standard error, SE) of the standardized 1-year changes in SER for HAL and DIMS spectacle lens users were − 0.34 (0.04) D and − 0.63 (0.07) D, respectively. HAL spectacle lenses reduced myopia progression by 0.29 D (95% confidence interval [CI] 0.13 to 0.44 D) at 1 year compared to DIMS lenses. Accordingly, the adjusted mean (SE) ALs increased by 0.17 (0.02) and 0.28 (0.04) mm for children wearing HAL lenses and DIMS lenses, respectively. HAL users had 0.11 mm less AL elongation (95% CI − 0.20 to − 0.02 mm) than DIMS users. Age at baseline was significantly associated with AL elongation. Chinese children wearing spectacle lenses designed with HAL had less myopia progression and axial elongation than those wearing spectacle lenses designed with DIMS.

When preparing a liquid, a drop of neat sample is pressed between two disks. A thin film of solid can be prepared by placing a drop of concentrated solution of the compound in the center of a disk and then allowing the solvent to evaporate. Since all materials have some sort of vibration associated with them pellets and thin-film cells must be considered carefully. If the sample holder has an optical window made of something that absorbs near where your sample does, the sample might not be distinguishable from the optical window of the sample holder. The range that is not blocked by a strong absorbance is known as a window (not to be confused with the optical materials of the cell). Windows are an important factor to consider when choosing the method to perform an analysis, as seen in Table \(\PageIndex{1}\) there are a number of different materials each with their own characteristic absorption spectra and chemical properties. Keep these factors in mind when performing analyses and precious sample will be saved. For most organic compounds NaCl works well though it is susceptible to attack from moisture.

Dong, L., Kang, Y. K., Li, Y., Wei, W. B. & Jonas, J. B. Prevalence and time trends of myopia in children and adolescents in China: A systemic review and meta-analysis. Retina 40, 399–411. https://doi.org/10.1097/IAE.0000000000002590 (2020).

Zhong, Y., Chen, Z., Xue, F., Miao, H. & Zhou, X. Central and peripheral corneal power change in myopic orthokeratology and its relationship with 2-year axial length change. Invest. Ophthalmol. Vis. Sci. 56, 4514–4519. https://doi.org/10.1167/iovs.14-13935 (2015).

IR spectra can be obtained from solid, liquid, or gas samples. Nujol mulls and pressed pellets are typically used for collecting spectra of solids, while thin-film cells are used for solution-phase IR spectroscopy. In these methods, infrared radiation is passed through the pellet or thin-film cells. A newer method for obtaining IR spectra uses attenuated total reflectance (ATR), which is discussed below. Gas samples require a special cell for sampling, but are not often used in organic chemistry, so will not be discussed further here.

ATR-FTIR is a physical method of compositional analysis that builds upon traditional transmission FTIR spectroscopy to minimize sample preparation and optimize reproducibility. Sample accessories make obtaining IR spectra of solids and liquids easier and it is not necessary to prepare Nujol mulls or disks. With ATR, infrared radiation is passed through an infrared transmitting crystal with a high refractive index. This allows the radiation to reflect within the crystal. This should be a material that is fully transparent to the incident infrared radiation to give a real value for the refractive index, \(\PageIndex{6}\).

Asphericallenses

Distributions of baseline prescription dates in the two groups. DIMS defocus incorporated multiple segments, HAL highly aspherical lenslets.

Because the path length of the evanescent wave is confined to the interface between the ATR crystal and sample, the sample should make firm contact with the ATR crystal. The sample sits atop the crystal and intimate contact can be ensured by applying pressure above the sample. However, one must be mindful of the ATR crystal hardness. Too much pressure may distort the crystal and affect the reproducibility of the resulting spectrum.

This page titled 4.3: Instrumentation is shared under a CC BY license and was authored, remixed, and/or curated by Lauren Reutenauer (OpenStax CNX) .

Carla, M. M. et al. Overview on defocus incorporated multiple segments lenses: A novel perspective in myopia progression management. Vision (Basel) 6. https://doi.org/10.3390/vision6020020(2022).

In an infrared spectrometer (Figure \(\PageIndex{4}\) ) the sample to be analyzed is held in front of an infrared laser beam, in order to do this, the sample must be contained in something, consequently this means that the very container the sample is in will absorb some of the infrared beam.

Nov 23, 2020 — IR will pass through many plastics but there are two factors that could impact your printing. First, pigmented plastics vs dye based color - the ...

There are some limitations in this study. Since this is a retrospective study, some confounders could not be identified, such as time spent outdoors, near-work time, myopia in parents, and duration of wearing spectacle lenses. The average follow-up was approximately nine months, and we used a standardized method to predict 1-year outcomes, which might be slightly different from the actual results for 1 year24. However, since the follow-up duration was similar between the two groups, this method should not affect the comparisons between the two types of lenses. Some children did not have cycloplegic refraction in the follow-up tests, and the results might overestimate the progression of myopia. However, we found a corresponding axial elongation associated with SER progression in children25. In addition, the data were from Chinese children in only one region. Thus, the results may not be applied to other ethnic children or other areas. Although the study had some limitations, we found a significant difference in myopia control between the two most effective spectacle lenses. Future studies with randomized designs or with locations in other regions are encouraged.

Several types of spectacles have been developed to slow myopia progression6,9,10. Among specifically designed lenses, recent research has shed light on two types of anti-myopic spectacle lenses11. In 2019, the effect on myopia control with defocus incorporated multiple segments (DIMS) spectacle lenses was published. The DIMS group delayed myopia progression by 52% compared to single-vision lenses in 2 years12. DIMS spectacle lenses have a 9-mm central single-vision zone surrounded by a honeycomb area consisting of multiple 1.03 mm width, + 3.5 D myopic defocus segments. Later, another 2-year clinical trial found that children wearing spectacle lenses comprising rings with highly aspherical lenslets (HAL) reduced myopia progression by 55% compared with those wearing single-vision lenses13. Outside the central normal refractive correction zone, the HAL lenses consist of 11 rings of continuous lenslets. The lenslet produces a volume of myopic defocus image with 0.7 mm depth and approximately 1.2 mm before the retina14.

In this study, older children had slower axial elongations but showed similar SER changes compared to younger children. It is possible that the process of emmetropization contributed to a significant AL increase without a comparable degree of SER change in young children22. In this study, neither sex nor baseline myopic indexes (SER and AL) were associated with myopia progression.

The primary outcome was the spherical equivalent refraction (SER) change from baseline. SER was calculated with spherical power plus half cylinder power. The secondary outcomes included the AL, spherical power, and cylinder power differences. The follow-up records within 12 ± 6 months were used to standardize the changes from baseline to 1 year according to the following calculation: changes in outcome values × (12/actual months between baseline and follow-up).

For the most part ATR crystals will have a trapezoidal shape as shown in Figure \(\PageIndex{6}\). This shape facilitates sample preparation and handling on the crystal surface by enabling the optical setup to be placed below the crystal. However, different crystal shapes (Figure \(\PageIndex{7}\) ) may be used for particular purposes, whether it is to achieve multiple reflections or reduce the spot size. For example, a hemispherical crystal may be used in a microsampling experiment in which the beam diameter can be reduced at no expense to the light intensity. This allows appropriate measurement of a small sample without compromising the quality of the resulting spectral features.

This study was supported in part by the Medical Science and Technology Research Grant in Guangdong Province (A2021368) and the Panyu Science and Technology Project (2020-Z04-046).

In this study, we observed that the unadjusted, standardized, 1-year mean myopia progression for HAL lens wearers was − 0.34 D with an AL increase of 0.17 mm. The outcomes are slightly higher than those of the previous 1-year 3-arm randomized control trial (RCT) comparing HAL, slightly aspherical lenslets (SAL), and single-vision lenses (− 0.27 D SER change and 0.13 mm AL increase in the HAL group)14. The raw mean SER and AL changes were − 0.63 D and 0.28 mm for the children wearing DIMS lenses in the present study. In contrast, a previous RCT comparing DIMS lenses and single-vision lenses showed less myopia progression as well as AL increase at the 1-year follow-up for DIMS users (− 0.17 D, 0.11 mm)12. Table 3 summarises the characteristics and outcomes of the present and previous studies.

Asphericalcamera vivo

Fan, Q. et al. Online learning-related visual function impairment during and after the COVID-19 pandemic. Front. Public Health 9, 645971. https://doi.org/10.3389/fpubh.2021.645971 (2021).

Bao, J. et al. One-year myopia control efficacy of spectacle lenses with aspherical lenslets. Br. J. Ophthalmol. https://doi.org/10.1136/bjophthalmol-2020-318367 (2021).

Asphericallens photography

It is the absorption of IR radiation by the sample, producing a change of IR radiation intensity, which gets detected as an off-null signal (e.g. different from reference signal). This change is translated into the recorder response through the actions of synchronous motors. Each frequency that passes through the sample is measured individually by the detector which consequently slows the process of scanning the entire IR region. A block diagram of a classic dispersive IR spectrometer is shown in Figure 4.3.1.

Detectors are devices that convert the analog spectral output into an electrical signal. These electrical signals are further processed by the computer using mathematical algorithm to arrive at the final spectrum. The detectors used in IR spectrometers can be classified as either photon/quantum detectors or thermal detectors.

Jul 15, 2023 — 1. Create a Class Implementing Comparator. One way to use the Comparator interface is by creating a separate class that implements the ...

May 20, 2011 — In the analog times, the resolution of film and/or lens was expressed in line pairs per millimeter (LP/mm). This unit expresses the amount of ...

Oct 22, 2024 — Causes of Fiber Cut and the Recommendation to Solve the Problem · 1) Arial or Overhead Installation. This form of installation required that ...

Lam, C. S. et al. Myopia control effect of defocus incorporated multiple segments (DIMS) spectacle lens in Chinese children: Results of a 3-year follow-up study. Br. J. Ophthalmol. 106, 1110–1114. https://doi.org/10.1136/bjophthalmol-2020-317664 (2022).

To understand the powerfulness and usefulness of FTIR spectrometer, it is essential to have some background information of dispersive IR Spectrometer. The basic components of a dispersive IR spectrometer include a radiation source, monochromator, and detector. The common IR radiation sources are inert solids that are heated electrically to promote thermal emission of radiation in the infrared region of the electromagnetic spectrum. The monochromator is a device used to disperse or separate a broad spectrum of IR radiation into individual narrow IR frequencies.

Cycloplegic autorefraction using Topcon KR 800 (Japan) followed by subjective refraction was performed at baseline. Noncycloplegic auto- and subjective refraction were examined during the follow-up visit. If the results were ambiguous, cycloplegic refraction was conducted. Cycloplegia was induced in each eye with three drops of 0.5% tropicamide administered 5 min apart. Refraction tests were performed 15 min after the last drop. The results from subjective refraction were used for the analyses. The axial length (AL) was measured at least three times with a ZEISS IOLMaster 500 (Germany), and the average was calculated.

Asphericalvs aspheric

Find your PAPCO SOCKET SET SCREWS ASSORTMENT, 15 SIZES, METAL CONTAINEER, 166 PIECES at Grainger Canada, formerly Acklands-Grainger.

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Handheld Video Magnifiers are ideal for spot reading and on-the-go use. Many fit perfectly into a purse or coat pocket. Equipped with LED lighting, ...

We assumed that the study period and region are the two main factors that caused the notable discrepancy in the effect for DIMS lenses between the study of Lam et al. and ours. Between 2020 and 2021, because of the COVID-19 pandemic, web-based education was promoted and even required in affected regions, including China18. Several studies have shown a myopia surge during this period19,20,21. The DIMS study by Lam et al. was conducted from 2014 to 2017, which was before the COVID-19 pandemic, while the HAL studies of Bao et al. and the present study were conducted mainly during the pandemic. In addition, both the HAL RCT and the present study observed children in mainland China, which has numerous differences in its education system, living environment, and lifestyle compared with those of Hong Kong, China.

Liu, S. et al. Association between axial length elongation and spherical equivalent progression in Chinese children and adolescents. Ophthal. Physiol. Opt. 42, 1133–1140. https://doi.org/10.1111/opo.13023 (2022).

It was more common in earlier instruments to allow selection of the incident angle. In all cases for total internal reflection to hold, the angle of incidence must exceed the critical angle and ideally complement the angle of the crystal edge so that the light enters at a normal angle of incidence. These days 45° is the standard angle on most ATR-FTIR setups.

Brennan, N. A., Toubouti, Y. M., Cheng, X. & Bullimore, M. A. Efficacy in myopia control. Prog. Retin. Eye Res. 83, 100923. https://doi.org/10.1016/j.preteyeres.2020.100923 (2021).

DIMS lenses had been widely used before HAL lenses were introduced to the market. To control the lockdown effect on myopia progression, we chose the starting point when the first qualified HAL lens user was available and obtained a similar baseline date distribution between the two study lenses19,20. Additionally, we found that for the HAL lenses, the average annual change in SER was approximately − 0.34 D, with an increase in AL of 0.17 mm from the real-world data.

Asphericaldefinition

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A common FTIR spectrometer consists of a source, interferometer, sample compartment, detector, amplifier, A/D convertor, and a computer. The source generates radiation which passes the sample through the interferometer and reaches the detector. Then the signal is amplified and converted to digital signal by the amplifier and analog-to-digital converter, respectively. Eventually, the signal is transferred to a computer in which Fourier transform is carried out. Figure 4.3.2 is a block diagram of an FTIR spectrometer.

Asphericalmirror

Hyperopic defocus images captured by retinal neurons can trigger eye growth, while myopic defocus inhibits eye enlargement15,16. Although the density of neurons in the central retina is the greatest, the accumulated number of neurons in the peripheral retina is larger than that in the fovea16. The area of the functional zone that creates peripheral myopic defocus is larger in the HAL lens than in the DIMS lens, which might lead to better myopia control. In addition, peripheral myopic defocus power was negatively associated with axial growth, which has been confirmed by previous studies on spectacle lenses and orthokeratology contact lenses14,17. It is possible that the degree of myopic defocus is different between the two lenses. Overall, the whole myopic defocus volume is assumed to be higher in the HAL lens than in the DIMS lens, which leads to slower myopia progression and axial growth using HAL lenses.

Asphericallens vs spherical

We can consider the sample to be absorbing in the infrared. Electromagnetic energy will pass through the crystal/sample interface and propagate into the sample via the evanescent wave. This energy loss must be compensated with the incident IR light. Thus, total reflectance is no longer occurring and the reflection inside the crystal is attenuated. If a sample does not absorb, the reflectance at the interface shows no attenuation. Therefore if the IR light at a particular frequency does not reach the detector, the sample must have absorbed it.

Choi, K. Y. et al. Evaluation of an optical defocus treatment for myopia progression among schoolchildren during the COVID-19 Pandemic. JAMA Netw. Open 5, e2143781. https://doi.org/10.1001/jamanetworkopen.2021.43781 (2022).

Asphericallens glasses

The unadjusted, standardized, 1-year mean (SE) change in SER was − 0.34 (0.04) D for the HAL group and − 0.63 (0.08) D for the DIMS group. The 95% CI of the mean difference (0.29 D) between the two groups was 0.13 to 0.44 D (P < 0.001). After controlling for age, sex, and baseline SER, the adjusted SER change difference showed a similar result (Table 2). Accordingly, the adjusted mean (SE) difference in the spherical power change was 0.32 (0.08) D (95% CI 0.17 to 0.47 D; P < 0.001). In contrast, the changes in cylinder power were not significantly different between the two groups (95% CI − 0.15 to 0.06 D; P = 0.42). The unadjusted, standardized, 1-year mean (SE) axial elongations for children using the HAL lenses and DIMS lenses were 0.17 (0.02) mm and 0.27 (0.04) mm, respectively. The HAL group exhibited slower AL increase than the DIMS group, with a mean difference of − 0.10 mm (95% CI − 0.19 to − 0.01 mm; P = 0.03). The adjusted mean difference in AL change was − 0.11 mm (95% CI − 0.20 to − 0.02 mm; P = 0.02).

After the incident radiation travels through the sample species, the emitted wavefront of radiation is dispersed by a monochromator (gratings and slits) into its component frequencies. A combination of prisms or gratings with variable-slit mechanisms, mirrors, and filters comprise the dispersive system. Narrower slits gives better resolution by distinguishing more closely spaced frequencies of radiation and wider slits allow more light to reach the detector and provide better system sensitivity. The emitted wavefront beam (analog spectral output) hits the detector and generates an electrical signal as a response.

This was a retrospective cohort study. The ethics committee of Guangzhou Aier Eye Hospital approved the study protocol, including the waiver of informed consent (GZAIER2022IRB11). The study was performed while observing the tenants of the Declaration of Helsinki. Data were collected from the Guangzhou Aier Eye Hospital database between September 2020 and March 2022. The children were selected if they were prescribed either HAL or DIMS, were younger than 16 years, and were without strabismus, amblyopia, or other ocular or systematic abnormalities. In addition, only those who had a refraction test between 6 and 18 months after the baseline visit without changing the type of spectacles were included in the analyses.

Bao, J. et al. Spectacle lenses with aspherical lenslets for myopia control vs single-vision spectacle lenses: a randomized clinical trial. JAMA Ophthalmol. 140, 472–478. https://doi.org/10.1001/jamaophthalmol.2022.0401 (2022).

Walline, J. J. et al. Interventions to slow progression of myopia in children. Cochrane Database Syst. Rev. 1, CD004916. https://doi.org/10.1002/14651858.CD004916.pub4 (2020).

Only the results of the right eyes were reported as significant correlations were observed between the two eyes for the changes in SER (r = 0.58, P < 0.001), AL (r = 0.78, P < 0.001), spherical power (r = 0.75, P < 0.001), and cylinder power (r = 0.30, P < 0.001). To compare the baseline characteristics between the two groups, unpaired t-tests were used for continuous variables, and the chi-square test was used for the categorical variable. The differences in the outcomes between the two groups were analyzed with unpaired t-tests and linear multivariate regression models. The models included age, sex, baseline refractive values or AL, and treatment as covariates. Age, refractive values, and AL were treated as continuous variables, while sex and treatment were treated as categorical variables in the models. The linear regression models with the same covariates were repeated for the observations without any missing values as sensitivity analyses. The analyses were performed with SAS 9.4 software. Results with a two-sided P value ≤ 0.05 were considered statistically significant.

Multiple interventions have been shown to significantly slow myopia progression, including the use of some specifically designed spectacle lenses, orthokeratology lenses, multifocal soft contact lenses, etc6. With easy adaptation features, no ocular infection concern, and lower cost compared to contact lenses, spectacles are the most common choice for myopia control7,8.

Optometry and Strabismus Department, Guangzhou Aier Eye Hospital, Jinan University, 191 Huanshi Middle Road, Yuexiu District, Guangzhou, 51000, China

The penetration depth of the evanescent wave within the sample is on the order of 1µm. The expression of the penetration depth is given in \ref{8} and is dependent upon the wavelength and angle of incident light as well as the refractive indices of the ATR crystal and sample. The effective path length is the product of the depth of penetration of the evanescent wave and the number of points that the IR light reflects at the interface between the crystal and sample. This path length is equivalent to the path length of a sample in a traditional transmission FTIR setup.

Myopia prevalence has been increasing dramatically in recent decades worldwide, particularly in East Asian countries, such as China1. By 2020, the prevalence of myopia among teenagers reached approximately 70% in urban cities in China2,3. It is estimated that by 2050, 50% of the population will have myopia, and 10% will have high myopia worldwide4. In particular, the predicted prevalence of myopia in China is even higher, with 84% of Chinese people having myopia5.

A common method of preparing solid samples for IR analysis is mulling, which is not a true solution, but a fine dispersion of a solid compound in a viscous liquid. The principle here is by grinding the particles to below the wavelength of incident radiation that will be passing through there should be limited scattering. To suspend those tiny particles, an oil, often referred to as Nujol is used. IR-transparent salt plates are used to hold the sample in front of the beam in order to acquire data. To prepare a sample for IR analysis using a salt plate, first decide what segment of the frequency band should be studied, refer to Table \(\PageIndex{1}\) for the materials best suited for the sample.

If the distances travelled by two beams are the same which means the distances between two mirrors and the beamsplitter are the same, the situation is defined as zero path difference (ZPD). But imagine if the movable mirror moves away from the beamsplitter, the light beam which strikes the movable mirror will travel a longer distance than the light beam which strikes the stationary mirror. The distance which the movable mirror is away from the ZPD is defined as the mirror displacement and is represented by ∆. It is obvious that the extra distance travelled by the light which strikes the movable mirror is 2∆. The extra distance is defined as the optical path difference (OPD) and is represented by delta. Therefore,

Brown, N. P., Koretz, J. F. & Bron, A. J. The development and maintenance of emmetropia. Eye (Lond) 13(Pt 1), 83–92. https://doi.org/10.1038/eye.1999.16 (1999).

Wolffsohn, J. S. et al. Global trends in myopia management attitudes and strategies in clinical practice - 2019 Update. Cont. Lens Anterior Eye 43, 9–17. https://doi.org/10.1016/j.clae.2019.11.002 (2020).

Sankaridurg, P. et al. Spectacle lenses designed to reduce progression of myopia: 12-month results. Optom. Vis. Sci. 87, 631–641. https://doi.org/10.1097/OPX.0b013e3181ea19c7 (2010).

He, X. et al. Prevalence of myopia and high myopia, and the association with education: Shanghai Child and Adolescent Large-scale Eye Study (SCALE): A cross-sectional study. BMJ Open 11, e048450. https://doi.org/10.1136/bmjopen-2020-048450 (2021).

Children prescribed HAL lenses were younger than those offered DIMS lenses, with a mean (standard error, SE) age of 9.57 (0.16) years versus 10.29 (0.26) years (mean difference, − 0.72 years; 95% confidence interval, [CI], − 1.34 to − 0.09 years; P = 0.03). Sex, baseline refractive values, and AL were comparable between the two groups (Table 1). The mean (SE) follow-ups were 274.2 (5.5) days and 267.3 (9.3) days for the HAL and DIMS groups,respectively, and the difference was not statistically significant (mean difference, 6.9 days; 95% CI − 14.7 to 28.5 days; P = 0.53). Twenty-one (11%) children in the HAL group and 7 (11%) children in the DIMS group were prescribed the cycloplegic refraction at the follow-up visit.

Spectacle lenses with highly aspherical lenslets (HAL) were more effective in delaying myopia progression and axial elongation than defocus incorporated multiple segments (DIMS) lenses in Chinese children.

Diffraction gratings are widely used optical components featuring periodic structures that allow dispersion of light in a more compact, convenient format than a ...

Russo, A. et al. Myopia: Mechanisms and strategies to slow down its progression. J. Ophthalmol. 2022, 1004977. https://doi.org/10.1155/2022/1004977 (2022).

It is well established that when OPD is the multiples of the wavelength, constructive interference occurs because crests overlap with crests, troughs with troughs. As a result, a maximum intensity signal is observed by the detector. This situation can be described by the following equation:

Guo, L. et al. Prevalence and associated factors of myopia among primary and middle school-aged students: A school-based study in Guangzhou. Eye (Lond) 30, 796–804. https://doi.org/10.1038/eye.2016.39 (2016).

Limwattanayingyong, J., Amornpetchsathaporn, A., Chainakul, M., Grzybowski, A. & Ruamviboonsuk, P. The association between environmental and social factors and myopia: A review of evidence from COVID-19 pandemic. Front. Public Health 10, 918182. https://doi.org/10.3389/fpubh.2022.918182 (2022).

The Michelson interferometer, which is the core of FTIR spectrometers, is used to split one beam of light into two so that the paths of the two beams are different. Then the Michelson interferometer recombines the two beams and conducts them into the detector where the difference of the intensity of these two beams are measured as a function of the difference of the paths. Figure 4.3.3 is a schematic of the Michelson Interferometer.

Multiple reflection ATR was initially more popular than single reflection ATR because of the weak absorbances associated with single reflection ATR. More reflections increased the evanescent wave interaction with the sample, which was believed to increase the signal to noise ratio of the spectrum. When IR spectrometers developed better spectral contrast, single reflection ATR became more popular. The number of reflections and spectral contrast increases with the length of the crystal and decreases with the angle of incidence as well as thickness. Within multiple reflection crystals some of the light is transmitted and some is reflected as the light exits the crystal, resulting in some of the light going back through the crystal for a round trip. Therefore, light exiting the ATR crystal contains components that experienced different number of reflections at the crystal-sample interface.

These two situations are two extreme situations. If the OPD is neither n-fold wavelengths nor (n+1/2)-fold wavelengths, the interference should be between constructive and destructive. So the intensity of the signal should be between maximum and minimum. Since the mirror moves back and forth, the intensity of the signal increases and decreases which gives rise to a cosine wave. The plot is defined as an interferogram. When detecting the radiation of a broad band source rather than a single-wavelength source, a peak at ZPD is found in the interferogram. At the other distance scanned, the signal decays quickly since the mirror moves back and forth. Figure 4.3.1.44.3.1.4(a) shows an interferogram of a broad band source.

A typical Michelson interferometer consists of two perpendicular mirrors and a beamsplitter. One of the mirror is a stationary mirror and another one is a movable mirror. The beamsplitter is designed to transmit half of the light and reflect half of the light. Subsequently, the transmitted light and the reflected light strike the stationary mirror and the movable mirror, respectively. When reflected back by the mirrors, two beams of light recombine with each other at the beamsplitter.

In the sensitivity tests without missing records for SER or AL, the adjusted, standardized, 1-year mean (SE) changes in SER were − 0.31 (0.05) D and − 0.59 (0.09) D in the HAL (n = 102) and DIMS (n = 33) groups, respectively. The mean (SE) difference between the two groups was 0.27 (0.10) D (95% CI 0.08 to 0.47 D; P = 0.008). The adjusted, standardized, 1-year mean (SE) ALs increased by 0.17 (0.02) mm and 0.28 (0.04) mm for children wearing HAL and DIMS lenses, respectively. DIMS users had significantly greater AL increase with a mean (SE) difference of − 0.11 (0.05) mm (95% CI − 0.20 to 0.02 mm; P = 0.02).

Wallman, J. & Winawer, J. Homeostasis of eye growth and the question of myopia. Neuron 43, 447–468. https://doi.org/10.1016/j.neuron.2004.08.008 (2004).

All the authors in this study were involved in protocol preparation (H.G., X.X.Z., J.H.L.), data collection (H.G., X.F.L., X.X.Z., J.H.L.), data analysis (H.G., H.Z.W.), and manuscript editing (H.G., X.F.L., X.X.Z., H.Z.W., J.H.L.).

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There are two types of instruments used to measure IR absorption: Fourier transform (FT) spectrometers and dispersive spectrometers. FTIR spectrometers are the most commonly used instruments for obtaining IR spectra. FTIR spectrometers have several prominent advantages:

In this study, children using highly aspherical lenslets (HAL)-designed spectacle lenses reduced 0.29 D myopia progression and 0.11 mm axial length (AL) elongation compared to those wearing DIMS lenses over a standardized 1-year period after adjusting for age, sex, and baseline spherical equivalent refraction (SER) or AL. Significant differences in SER and AL changes were also detected in sensitivity tests including records without missing outcome values.

Guo, H., Li, X., Zhang, X. et al. Comparing the effects of highly aspherical lenslets versus defocus incorporated multiple segment spectacle lenses on myopia control. Sci Rep 13, 3048 (2023). https://doi.org/10.1038/s41598-023-30157-2

Jonas, J. B. et al. IMI prevention of myopia and its progression. Invest. Ophthalmol. Vis. Sci. 62, 6. https://doi.org/10.1167/iovs.62.5.6 (2021).

To the best of our knowledge, this was the first study comparing HAL and DIMS lenses, which are two of the most compelling spectacle lenses for myopia control compared with single-vision spectacle lenses6,11,14,23. We compared these two lenses in the same population and found that HAL-designed lenses had a more substantial effect than DIMS lenses for the prevention of myopia progression as well as AL elongation in Chinese children.

In the linear multivariate regression model, baseline age was negatively associated with axial lengthening. The standardized AL showed a 0.02 mm less increase with 1 year older at baseline (P = 0.03). In contrast, age was not significantly associated with SER change. Sex and baseline SER or AL values were not associated with SER or AL changes during the study period.