Axial Length Research Articles

Prediction of Axial Length From Macular Optical Coherence Tomography Using Deep Learning Model.

The purpose of this study was to develop a deep learning model for predicting the axial length (AL) of eyes using optical coherence tomography (OCT) images. We retrospectively included patients with AL measurements and OCT images taken within 3months. We utilized a 5-fold cross-validation with the ResNet-152 architecture, incorporating horizontal OCT images, vertical OCT images, and dual-input images. The mean absolute error (MAE), R-squared (R2), and the percentages of eyes within error ranges of ±1.0, ±2.0, and ±3.0mm were calculated. A total of 9064 eyes of 5349 patients (total image number of 18,128) were included. The average AL of the eyes was 24.35 ± 2.03 (range = 20.53-37.07). Utilizing horizontal and vertical OCT images as dual inputs, deep learning models predicted AL with MAE and R2 of 0.592mm and 0.847mm, respectively, in the internal test set (1824 eyes of 1070 patients). In the external test set (171 eyes of 123 patients), the deep learning models predicted AL with MAE and R2 of 0.556mm and 0.663mm, respectively. Regarding error margins of ±1.0, ±2.0, and ±3.0mm, the dual-input models showed accuracies of 83.50%, 98.14%, and 99.45%, respectively, in the internal test set, and 85.38%, 99.42%, and 100.00%, respectively, in the external test set. A deep learning-based model accurately predicts AL from OCT images. The dual-input model showed the best performance, demonstrating the potential of macular OCT images in AL prediction. The study provides new insights into the relationship between retinal and choroidal structures and AL elongation using artificial intelligence models.

Late Bedtime and Altered Diurnal Axial Length Rhythms of the Eye

Purpose Affecting one-third of the population worldwide and increasing, the sight-threatening condition myopia is causing a significant socio-economic burden. To better understand its etiology, recent studies investigated the role of ocular and systemic rhythms, yet results are conflicting. Here we profiled 24-h variations of axial length of the eye and salivary melatonin concentration in young adults with and without myopia and explored the potential impacts of bedtime on these rhythms. Methods A total of 25 healthy young adults (age 25.0 ± 4.8 years, 13 females) completed this study, including 13 myopes (mean spherical equivalent refractive error −2.93 ± 1.46 diopters) and 12 non-myopes (0.14 ± 0.42 diopters). Saliva sample collection and axial length measurements were repeated for seven times over 24 h starting from 8 am. Information on sleep and chronotype was collected at first visit with the Pittsburgh Sleep Quality Index and the Morningness-Eveningness Questionnaire. Results Significant diurnal rhythms of axial length and salivary melatonin concentration were identified in both refractive groups (both p < 0.001), with no myopia-related rhythm difference (interaction of measurement time-point × myopia, p = 0.9). Late bedtime was associated with altered rhythms (p = 0.009) and smaller diurnal change (p = 0.01) in axial length. Elevated melatonin levels were observed in myopes (p = 0.006) and in late sleepers (p = 0.017). Conclusions These findings suggest that sleep/wake cycles may be involved in the regulation of axial length rhythms. Further research is needed to determine if there exists a causal relationship between the two.

Lens Power and Associated Factors in Nonhuman Primate Subjects: A Cross-sectional Study.

We aimed to examine the normative profile of crystalline lens power (LP) and its associations with ocular biometric parameters including age, axial length (AL), spherical equivalent refraction (SE), corneal radius (CR), lens thickness, anterior chamber depth, and AL/CR ratio among a cynomolgus monkey colony. This population-based cross-sectional Non-human Primate Eye Study recruited middle-aged subjects in South China. All included macaques underwent a detailed ophthalmic examination. LP was calculated using the modified Bennett's formula, with biometry data from an autorefractometer and A-scan. SPSS version 25.0 was used for statistical analysis. A total of 301 macaques with an average age of 18.75 ± 2.95years were collected in this study. The mean LP was 25.40 ± 2.96 D. Greater LP was independently associated with younger age, longer AL, and lower SE (P = 0.028, P = 0.025, and P = 0.034, respectively). LP showed a positive correlation with age, SE, CR, AL, lens thickness, and anterior chamber depth, whereas no correlation was observed between LP and AL/CR ratio. Our results suggested the LP distribution in the nonhuman primate colony and indicated that AL and SE strongly influenced the rate of LP. Therefore, this study contributed to a deeper understanding of the relative significance of the LP on the optics of the crystalline lens study.

Thiel cadaver eye as a training model for sub-Tenon’s blocks: a feasibility study

BackgroundRegional anaesthesia education, especially for ocular procedures, necessitates reliable surgical training models. While cadaveric models offer anatomical fidelity, conventional embalming methods may compromise tissue integrity. We aimed to assess the effectiveness of Thiel cadavers for training in sub-Tenon’s blocks by evaluating ocular tissues and measuring insertion forces.MethodsExperimental design, using twenty eyes from ten Thiel cadaver heads. These cadavers were specifically prepared to test the administration of sub-Tenon’s blocks. The research was conducted in a controlled laboratory setting appropriate for handling cadaveric materials and conducting precise measurements. Each cadaver eye underwent an initial ultrasound examination, and its axial length was noted. An intravitreal injection of heptastarch solution followed, to re-establish the eye’s sphericity. After this volume injection, the axial length and intraocular pressure were measured again. Mock sub-Tenon’s blocks were administered in 2 separate quadrants of the eye, with insertion forces measured using a pressure gauge. These were compared to a data set of insertion forces measured in a series of isolated pig’s eyes on which STBs had been performed. Main outcome measurements were macroscopic assessment of the ocular tissue layers and the insertion forces required for the sub-Tenon’s blocks. In a second set of 10 Thiel cadaver heads, 5 ml of sodium chloride were injected as sub-Tenon’s blocks and the emergence of a periocular “T-sign” ascertained and measured by ultrasound.ResultsFour of twenty eyes (20%) retained near-natural sphericity, with the remaining requiring volume injection to approximate physiological shape and pressure. The conjunctiva and Tenon’s layer were intact, and correct cannula placement was achieved in all cases. In 16 of 20 eyes where T-signs could be measured, the median thickness of the T-sign amounted to 2.72 mm (range 1.34 mm–5.28 mm). The average maximum cannula insertion force was 2.92 Newtons. Insertion forces in intact Thiel cadaver heads were consistently higher than in isolated pig’s eyes (3.6 N vs 2.0 N).ConclusionThese findings suggest that Thiel cadavers are a promising model for training in sub-Tenon’sblocks, despite the challenge of often desiccated and involuted eyes.

VEGFA may be a potential marker of myopic choroidal thickness and vascular density changes

To evaluate the changes of choroidal thickness (CT) and blood flow related to myopia, and its effects of vascular endothelial growth factor (VEGFA) on choroidal vessels in myopia. Subjects were included and divided into emmetropia (EM), non-high myopia (Non-HM) and high myopia (HM) groups. we measured choroidal thickness (CT), choriocapillaris vessel density (VD), and VEGFA content in tears in humans (137 subjects for CT, VD and 84 for tear) and detected the role of VEGFA in the choroid in form-deprivation myopia (FDM) in guinea pigs. Twenty-four guinea pigs were divided into control and FDM groups, and the expression changes of choroidal vessels and VEGFA were observed and compared using immunohistochemistry and Western blotting. Twenty-one guinea pigs were divided into control, FDM + Vehicle and FDM + Conbercept groups. The changes of diopter, axis length and choroidal vessels after intravitreal injection of Conbercept were observed. There were significant differences in CT and VD among the three groups (p < 0.05). VEGFA levels in tears were significantly lower in the myopic groups, with a decreasing trend from EM to Non-HM to HM. The choroidal vascular area fraction of FDM decreased compared to the control group. FDM guinea pigs exhibited reduced choroidal vasculature and significant downregulation of VEGFA expression. Following intravitreal injection of conbercept, the FDM + Conbercept group showed greater myopia, longer axial length, and lower choroidal vascular area fraction compared to the control group. VEGFA may participate in the regulation of choroidal blood vessels and blood flow in the progression of myopia. The reduction in VEGFA may accelerates the progression of myopia.

Efficacy of orthokeratology lens with the modified small treatment zone on myopia progression and visual quality: a randomized clinical trial

BackgroundTo evaluate the long-term effectiveness of orthokeratology (ortho-K) lenses with small treatment zone (STZ) or conventional treatment zone (CTZ) in controlling axial elongation in children with myopia as well as the impact on visual quality. We also sought to determine the effect of retinal visual signal quality on axial elongation.MethodsThis is a prospective randomized controlled study. A total of 140 participants (age ranging from 8 to 12 years) were randomly assigned to wear either STZ or CTZ ortho-K lenses. STZ ortho-K lenses design was achieved by changing the depth of reverse zone and the sagitta height of the optical zone. Using the IOL-Master 500, axial length (AL) was measured at baseline and after 6, 12 and 18 months of ortho-K treatment. Spherical aberration (SA) and corneal topographic parameters were obtained by the Pentacam anterior segment analyzer at baseline and the 1-month follow-up visit, and optical qualities were assessed by optical quality analysis system-II (OQAS-II) at baseline and after 1 month of lens wearing. Optical quality parameters mainly included the modulation transfer function (MTF) cutoff, Strehl ratio (SR), objective scattering index (OSI), and predicted visual acuity (PVA).ResultsA total of 131 participants completed the study, including 68 in the STZ group and 63 in the CTZ group. The STZ group had significantly reduced AL elongation compared to the CTZ group after treatment (12 months: 0.07 ± 0.11 mm vs. 0.14 ± 0.12 mm, P = 0.002; 18 months: 0.17 ± 0.15 mm vs. 0.26 ± 0.16 mm, P = 0.002). The topography in the STZ group showed a smaller treatment zone (TZ) diameter (2.50 ± 0.23 mm vs. 2.77 ± 0.18 mm, P < 0.001), a wider defocus ring width (2.45 ± 0.28 mm vs. 2.30 ± 0.30 mm, P = 0.006), and larger values of total amount of defocus (119.38 ± 63.71 D·mm2 vs. 91.40 ± 40.83 D·mm2, P = 0.003) and total SA (0.37 ± 0.25 μm vs. 0.25 ± 0.29 μm, P = 0.015), compared with the CTZ group. Objective visual quality decreased in both groups (P < 0.001). This was evidenced by a greater decrease in MTF cutoff (− 14.24 ± 10.48 vs. − 10.74 ± 9.46, P = 0.047) and SR values (− 0.09 ± 0.07 vs. − 0.06 ± 0.07, P = 0.026), and an increase in OSI value (0.84 ± 0.72 vs. 0.58 ± 0.53, P = 0.019). PVA9% decreased significantly in the STZ group but not the CTZ group. A statistically significant negative correlation was found between the changes in total SA and MTF cutoff values (r = − 0.202, P = 0.025). AL changes were associated with sex, change of MTF cutoff value, increment of total SA and TZ area.ConclusionsCompared with CTZ ortho-K lenses, STZ ortho-K lenses significantly inhibited axial elongation in children with myopia while moderately reducing their objective visual quality. Axial elongation was affected by retinal visual quality, and it may be a possible mechanism for ortho-K slowing myopia progression.Trial registration This trial is registered at Chinese Clinical Trial Registry on November 5, 2019 with trial registration number: ChiCTR1900027218. https://www.chictr.org.cn/showproj.html?proj=45380

Ocular biometry parameters in mobile cataract surgery camp: a large-scale report from Nigeria

Background: Humanitarian missions and mobile camp surgeries have pivotal roles in cataract surgery in areas with limited resources. Ocular biometry is an important preoperative evaluation tool for cataract surgery candidates. Herein, we report the distributions of ocular biometric values among cataract surgery candidates in camp settings in southern Nigeria. Methods: In this cross-sectional study, we retrieved data from consecutive patients scheduled for cataract surgery. All patients underwent a full ophthalmic examination using a slit-lamp biomicroscope. Age, sex, and preoperative biometric values, including anterior chamber depth (ACD), lens thickness (LT), vitreous chamber depth (VCD), and axial length (AL), together with intraocular lens (IOL) power, were documented. Biometric values were obtained using A-mode ultrasonography. Results: Records of 567 patients with a mean (standard deviation) age of 66.0 (13.4) years revealed a male-to-female sex ratio of 1:1.24. Most participants were in the 66–70-year age group. Mean IOL power was significantly different between males and females (P &lt; 0.001). However, the biometric values were comparable between sexes (all P &gt; 0.05). There were significant differences in the mean IOL power (P &lt; 0.001) and ACD (P &lt; 0.05) between the age groups, indicating a decrease in ACD with age. However, the other biometric parameters were comparable between the age groups (all P &gt; 0.05). ACD had a significant weak negative correlation with LT (r = - 0.16; P &lt; 0.001) and IOL power (r = - 0.22; P &lt; 0.001) and a positive correlation with AL (r = + 0.24; P &lt; 0.001). LT had a significant weak negative correlation with VCD (r = - 0.16; P &lt; 0.001) and a positive correlation with AL (r = + 0.09; P &lt; 0.05). VCD had significant moderate positive and negative correlations with AL (r = + 0.39; P &lt; 0.001) and IOL power (r = - 0.34; P &lt; 0.001), respectively. AL had a significant strong negative correlation with IOL power (r = - 0.78; P &lt; 0.001). Conclusions: This study presents the mean distributions of ocular biometric parameters among cataract surgery candidates in camp settings in southern Nigeria. Age and sex were important determinants of IOL power and should be considered when planning eye camp supplies. AL had a strong inverse correlation with IOL power. Further multicenter national studies are required to verify these preliminary findings.

Influence of Capsular Tension Rings on the IOL-Capsule Complex in Patients With Long Axial Length: A Clinical Observation Based on SS-OCT.

To evaluate the influence of a capsular tension ring (CTR) on the intraocular lens (IOL)-capsule complex after cataract surgery in patients with long axial length. This was a prospective study. Patients underwent phacoemulsification and IOL implantation, with or without CTR implantation. Swept-source optical coherence tomography was performed at 1 day, 1 week, 1 month, and 3 months postoperatively to determine the postoperative aqueous depth (PAD), capsular bend index (CBI), and IOL tilt and decentration. Spherical equivalent values were obtained through subjective refraction and autorefraction. Root mean square was adopted to evaluate the indices listed above. Forty-three patients (56 eyes) were included in the study. Generalized estimating equation analysis of PAD showed a statistical difference between groups (P = .031). The RMS of the change in PAD was smaller in the CTR group than in the non-CTR group during the 3 months after surgery (P = .015). CBI in the CTR group increased more from 1 to 3 months after surgery than that in the non-CTR group (P = .025). The RMS of the change in vertical decentration was smaller in the CTR group than in the non-CTR group during the 3-month follow-up (P = .009). CTR implantation can stabilize the axial position of the IOL within the capsular bag after cataract surgery in patients with long axial length without affecting the refractive stability. The formation of capsular bend may be slightly delayed in the early stage after CTR implantation, but it accelerates from 1 to 3 months after surgery. [J Refract Surg. 2024;40(9):e654-e661.].

Anisomyopia and orthokeratology for myopia control - Axial elongation and relative peripheral refraction.

To investigate axial elongation (AE) and changes in relative peripheral refraction (RPR) in anisomyopic children undergoing orthokeratology (ortho-k). Bilateral anisomyopic children, 7-12 years of age, were treated with ortho-k. Axial length (AL) and RPR, from 30° nasal (N30°) to 30° temporal (T30°), were measured at baseline and every 6 months over the study period. AE, changes in RPR and changes in the interocular AL difference were determined over time. Twenty-six of the 33 subjects completed the 2-year study. The AE of the higher myopic (HM)eyes (at least 1.50 D more myopia than the other eye) (0.26 ± 0.29 mm) was significantly smaller than for the less myopic (LM)eyes (0.50 ± 0.27 mm; p = 0.003), leading to a reduction in the interocular difference in AL (p = 0.001). Baseline RPR measurements in the HM eyes were relatively more hyperopic at T30°, N20° and N30° (p ≤ 0.02) and greater myopic shifts were observed at T20° (p < 0.001), T30° (p < 0.001), N20° (p = 0.02) and N30° (p = 0.01) after lens wear. After 2 years of ortho-k lens wear, temporal-nasal asymmetry increased significantly, being more myopic at the temporal locations in both eyes (p < 0.001), while AE was associated with the change in RPR at N20° (β = 0.134, p = 0.01). The interocular difference in AE was also positively associated with the interocular difference in RPR change at N30° (β = 0.111, p = 0.02). Ortho-k slowed AE in bilateral anisomyopia, with slower growth in the HM eyes leading to a reduction in interocular AL differences. After ortho-k, RPR changed from hyperopia to myopia, with greater changes induced in the HM eyes, and slower AE was associated with a more myopic shift in RPR, especially in the nasal field of both eyes.

Unveiling the Mysteries of the Chinese lens zonule balance tension: A statistical analysis

BackgroundThis study aims to provide an estimated dataset of lens zonule balance tension (LZBT) measurements in cataractous lenses among Chinese patients and to conduct a statistical analysis of anterior segment parameters. MethodsThis is a cross-sectional study. We included a total of 833 eyes from 833 Chinese participants aged 23–91 years who underwent cataract surgery. Anterior segment parameters were measured using swept-source anterior segment optical coherence tomography (SS-AS OCT) to calculate lens gravity (LG) and crystalline lens volume (VOL). Axial length (AL) was measured using IOL-Master 700. LZBT was calculated using force decomposition and synthesis methods. ResultsThe mean LZBT in the horizontal direction was 8.48E-05 ± 3.23E-05 N across all eyes. The LZBT in the subtemporal-supraspinal and supraspinal-temporal directions was 2 times greater than in the vertical direction. The balanced force on the suspensory ligament in the horizontal direction was twice as strong as in the vertical direction. Additionally, anterior segment parameters such as lens equivalent diameter (LE-dia), radius of the anterior lens surface curvature (RAL), radius of the posterior lens surface curvature (RPL), anterior chamber depth (ACD), iris area, iris volume, and iris thickness showed positive correlations with AL. ConclusionsAccounting for gravitational effects, we concluded that zonule force is asymmetrically distributed. Importantly, this study establishes the normal range of LZBT across different meridians using force synthesis and decomposition, offering new insights and feasibility for studying suspensory ligament biomechanics.

The efficacy of orthokeratology lenses with smaller back optic zone diameter in myopia control. A meta-analysis.

This study was conducted to determine whether orthokeratology (OK) lenses with a smaller back optic zone diameter (BOZD) could exhibit stronger myopia control effects. A meta-analysis was registered in PROSPERO (CRD42023408184). A comprehensive systematic database search was conducted, encompassing PubMed, Cochrane Library, EMBASE, MEDLINE, Web of Science, Ovid, CNKI and CBM, to identify relevant studies up to 25 March 2023. The primary inclusion criteria for this meta-analysis were studies that investigated the myopia control effect of OK lenses with a small optical treatment area (≤5 mm). To assess the quality of the retrieved articles, two researchers evaluated them using the Cochrane bias risk assessment criteria. The primary outcome measures were the changes in axial length (AL) and refractive error, using the weighted mean differences (WMD) and 95% confidence intervals (CI) to assess differences between small and traditional back optical treatment zone groups in terms of these outcomes. The analysis encompassed five eligible studies, with a 1 year duration. The average difference in AL between the groups was 0.12 mm (WMD = -0.12, 95% CI [-0.16, -0.09], p < 0.00001). Likewise, the average difference in refractive error between the two groups was 0.44 D (WMD = 0.44, 95% CI [0.30, 0.57], p < 0.00001). None of the studies reported severe adverse events. Current evidence suggests that OK lenses with smaller back optical treatment zone are more effective in preventing myopia progression than traditional lenses. However, a longer-term evaluation is warranted.

The effect of individualized ocular refraction customized spectacle lenses on myopia control in schoolchildren: A 1-year randomised clinical trial.

The aim of this study was to investigate the effect of individualized ocular refraction customized (IORC) spectacle lenses with different actual amounts of peripheral myopic defocus (MD) on myopia control over 1 year. These lenses compensate for the original peripheral refraction via the free-form surface on the back of the lens. This 1-year, double-masked randomised clinical trial included 184 myopic schoolchildren aged 8-12 years. Participants were randomised to receive IORC lenses with high (IORC-H group, +4.50 D), medium (IORC-M group, +3.50 D) or low (IORC-L group, +2.50 D) MD or single-vision (SV) lenses. The spherical equivalent refractive error (SER) and axial length (AL) were measured at baseline and 6-monthly intervals. After 1 year, the mean (SD) changes in SER were -0.18 (0.37), -0.36 (0.37), -0.52 (0.39) and -0.60 (0.42) D for the IORC-H, IORC-M, IORC-L and SV groups, respectively. Compared with the SV group, the effects of slowing myopia progression were 70%, 40% and 13% for the IORC-H (difference of 0.47 D, p < 0.001), IORC-M (difference of 0.32 D, p = 0.001) and IORC-L (difference of 0.15 D, p > 0.05) groups, respectively. The mean (SD) changes in AL were 0.12 (0.16), 0.23 (0.17), 0.29 (0.17) and 0.36 (0.17) mm for the IORC-H, IORC-M, IORC-L and SV groups, respectively. The axial elongation was 67%, 36% and 19% lower in the IORC-H (difference of 0.25 mm, p < 0.001), IORC-M (difference of 0.15 mm, p < 0.001) and IORC-L (difference of 0.10 mm, p = 0.04) groups, respectively, compared with the SV group. The IORC-H group exhibited significantly less axial elongation than the IORC-M and IORC-L groups (p = 0.01 and p < 0.001, respectively). Compared with the IORC-M and IORC-L lenses, the IORC-H lens was found to have superior efficacy in inhibiting myopic progression and slowing eye growth in schoolchildren, with better myopia control efficacy in younger children.

Effects of Insufficient Sleep on Myopia in Children: A Systematic Review and Meta-Analysis.

Myopia is increasingly prevalent in children. Its association with insufficient sleep has been studied, yielding inconsistent findings. This review aims to assess the association of insufficient sleep with myopia and myopia-related refractive parameters in children. A total of 657 articles were identified, of which 40 were included in the systematic review and 33 were included in the meta-analysis. Results showed that insufficient sleep was significantly associated with an increased prevalence of myopia (odds ratio [OR] = 1.59; 95% confidence interval [CI] = 1.31, 1.95; I 2 = 99%), and an increased prevalence of high myopia (OR = 3.36; 95% CI = 1.26, 9.00; I 2 = 96%). Shorter sleep duration was significantly linked to faster changes in axial length (AL) (β = 0.05; 95% CI = 0.02, 0.08; I 2 = 0%). However, correlation between insufficient sleep and the incidence of myopia, spherical equivalent refraction, corneal curvature radius (CR) and AL/CR were insignificant. Moreover, the effect of insufficient sleep on premyopia and astigmatism was not well-studied. The results of this study suggest that insufficient sleep may be an important risk factor for the development of myopia in school-aged children. Therefore, in addition to ensuring sufficient outdoor activities and reducing near work, it is necessary to inform children and parents about the importance of adequate sleep to mitigate the risk of myopia.

Implantable continuous-flow total artificial heart for newborns and small pediatric patients: First report of working model

ObjectiveThe need for safe and reliable mechanical circulatory support (MCS) for smaller children with severe heart failure (HF) is well defined. More specifically, in pediatric patients with advanced congenital HF, there is no implantable total artificial heart (TAH) device available for small patients. Herein, we report the development of the infant continuous-flow total artificial heart (I-CFTAH), a fully implantable in infants and newborns. MethodsAfter extensive engineering analysis, we performed an unprecedented effort: reducing the I-CFTAH's displacement volume to be 14% of the adult CFTAH pump while simultaneously decreasing pump diameter (6.2 cm to 2.6 cm) and axial length (9.8 cm to 4.8 cm). Facilitated by these proportional reductions, for the first time, a durable total artificial heart device was successfully fit in the chest of infants and newborns (height of ≥50 cm). ResultsThe functional I-CFTAH prototype demonstrated capability to support stable hemodynamics and desired device performance. The pump flow range (0.5-1.5 L/min) was confirmed in a mock circulatory testing loop. Within the tested flow range, the I-CFTAH can support small patients that could benefit from the intended cardiac output. ConclusionsThis successful effort demonstrated the feasibility of the miniature continuous-flow total artificial heart, intended for very small patient populations. I-CFTAH showed stable hemodynamics and could, therefore, become one of the few therapeutic options as a bridge to transplantation, aiming to enhance both the quality and duration of life for pediatric patients with advanced HF.

Effect of lighting conditions on implantable collamer lens vault: Influence of anterior chamber and lens parameters

PurposeTo investigate the change in the vault of the implantable collamer lens (ICL) under dark-to-light conditions and its association with anterior chamber and lens parameters in patients undergoing ICL surgery. MethodsIn 76 eyes from 40 patients, preoperative anterior chamber volume (ACV), pupil diameter (PD), anterior chamber angle, central corneal thickness (CCT), white-to-white (WTW), lens thickness (LT), axial length (AL), spherical equivalent (SE) and patient's age were collected. Postoperative vault, PD and LT were measured under dark and light conditions using anterior segment optical coherence tomography (CASIA2; TOMEY, Japan), and changes and lens displacement under dark-to-light conditions were calculated. Mixed-effects models were used to analyze the correlation between the vault change and the anterior chamber and lens parameters of all subjects and the high-vault subgroup. ResultsThe vault under light condition (648.36 ± 304.47 μm) was significantly smaller compared to the vault under dark condition (708.89 ± 316.15 μm). In all patients, vault change increased with the increase of age, lens displacement and PD change; and increased with the decrease of ACV, LT change and baseline vault (under dark condition). In the high-vault subgroup, vault change increased with the increase of CCT, lens displacement and PD change; and increased with the decrease of ACV. ConclusionsICL vault changes significantly from dark to light, influenced by age, ACV, PD change, LT change, lens displacement, and baseline vault. A higher baseline vault is correlated with a larger LT change, affecting the levels of accommodation under dark-to-light transition.

Effects of transducer’s Parameters on the Amplitude Response of Spirally Propagating Circumferential Lamb Wave and Their Application in Defect Detection

Abstract The commonly used traditional cylindroid guided wave modes are not sensitive to a crack with limited circumferential extent within a pipe. The circumferential guide wave will not be affected by the limited circumferential extent of a crack, which can be make up the limitation of the commonly used traditional cylindroid guided wave modes in crack detecting within a pipe. This article studied the spirally propagating circumferential Lamb wave within a pipe, which can determine the axial position of a crack only if the axial extent of the crack is large enough regardless the limited circumferential extent of the crack. To efficiently trigger the spirally propagating circumferential Lamb wave, the effect of the frequency, the circumferential coverage and the axial length of the transducer on the spirally propagating circumferential Lamb wave signals were investigated based on the theoretical model and experiments. Then, the comparison experiments presented the superiority of the proposed spirally propagating circumferential Lamb wave in detecting a crack with limited circumferential extent over the commonly used cylindroid guided wave mode. Finally, the angular interval of two cracks that in the same axial position can be determined through the angular interval of the triggering positions of the spirally propagating circumferential guided wave, which cannot be evaluated through the commonly used traditional cylindroid guided wave modes.

Posterior scleral reinforcement surgery effectively slows the rate of high myopic progression in children

To investigate the rate of axial length elongation and high myopia progression in operated eyes before and after posterior scleral reinforcement (PSR) surgery. This was a retrospective study. Children with pathological myopia treated with PSR at Beijing Tongren Hospital between May 2013 and May 2020 were recruited into the PSR surgery group. Children matched for age and myopia were recruited into the control group. All children underwent comprehensive ophthalmologic examinations. The presurgical and postsurgical rates of axial length elongation and myopic (spherical equivalent) progression were calculated. A total of 35 PSR patients were included in the study. The mean age was 6.5±3.0years (range 2 to 14years). Mean follow-up was 544days (range 216 to 1657days). The rate of axial length elongation was significantly less after posterior scleral reinforcement surgery (0.505±0.048mm per year prior to surgery; 0.382±0.045mm per year after surgery, P<0.001). The rate of myopic progression decreased after posterior scleral reinforcement surgery (1.162±0.118D per year prior to surgery; 0.153±0.437D per year after surgery, P=0.0239). There was no statistically significant difference in axial length elongation or myopic progression between pre-inclusion and post-inclusion in the control group. Moreover, the children's best-corrected visual acuity was significantly improved after posterior scleral reinforcement surgery (P<0.001). Posterior scleral reinforcement surgery effectively decreased the rate of high myopic progression and axial length elongation in children.

Experimental study and infrared detector application research of micro miniature refrigerators

The MMR（Micro Miniature Refrigerator）is a novel Joule-Thomson cryocooler manufactured by micro-machining technologies, its axial length is significantly shorter than traditional Joule-Thomson cryocoolers commonly employed in infrared detectors. MMRs can greatly reduce the size of infrared detectors upon successful implementation. However, contemporary MMR products encounter challenges such as relatively low cool-down rates, cooling power, and structural strength. To address these issues and enhance the cool-down performance of the MMR for effective application in infrared detectors, a calculation model describing flow and heat transfer besides working characteristics of the MMR is proposed and verified. MMR prototypes are fabricated and experimentally studied. Building upon theoretical analysis and experimental findings cooling performance enhancement methods including transitioning the MMR material from glass to metal and modifying the structure and channel patterns of the MMR are introduced, the cooling performance of the MMR is thus greatly improved. Furthermore, an integrated design incorporating an MMR into an infrared detector is proposed, the axial length of this infrared detector is reduced by 65.3 % compared to conventional infrared detectors. And the MMR is further enhanced to adapt the working conditions in infrared detectors, 60.9 MPa working pressure and 38 s cool-down time is achieved, the cool-down requirements of infrared detectors is satisfied. Notably, the proposed MMR and infrared detector design in this paper exhibit technical advantages over similar products reported in the literature.

Does blepharospasm effect biometric parameters and intraocular lens power calculations?

To investigate the effect of botulinum toxin-A (BTX-A) treatment on corneal topography, ocular biometry and keratometry in patients with benign essential blepharospasm (BEB) and hemifacial spasm (HFS). This study comprised 66 eyes of 33 patients with BEB and 5 eyes of 5 patients with HFS who underwent BTX-A injections consecutively. Refractive error values, tear break-up time (TBUT), corneal topography [corneal power of flat axis (K1) and steep axis (K2), mean corneal power (Km), corneal astigmatism (K2-K1)] and ocular optical biometry [axial length (AL), anterior chamber depth (ACD)] were recorded before BTX-A treatment and 1 month after BTX-A treatment. The researchers calculated the expected emmetropic intraocular lens power (emm-IOL) using the SRK-T, Holladay, Hoffer-Q and Haigis formulas at each examination. K1 (43.48 ± 2.02 vs. 43.57 ± 2.08, p = 0.036), Km (43.91 ± 1.99 vs. 43.99 ± 2.06, p = 0.024) and ACD (3.22 (2.77-3.76) vs. 3.41 (2.99-4.02), p < 0.001) values were found to be significantly higher. The expected emm-IOL according to the SRK-T (21.04 ± 1.6 vs. 20.93 ± 1.6, p = 0.048), Holladay (21.05 ± 1.6 vs. 20.91 ± 1.62, p = 0.037) and Hoffer-Q (21.08 ± 1.65 vs. 20.94 ± 1.68, p = 0.038) decreased significantly. The expected emm-IOL according to the Haigis formula slightly decreased, but it was not significant (p = 0.386). Additionally, TBUT was found to be significantly lower (p < 0.001) after BTX-A injection. Other parameters were not statistically significant (p > 0.05). Our study is the first in the literature to compare optic biometry data and intraocular lens power calculation formulas before and after BTX-A injection in eyes with BEB and HFS. BTX-A injection could play an important role in changing the keratometric and ACD values. It should be considered that IOL power calculations that might be unpredictable due to blepharospasm, so repeated measurements and especially measurements after releasing the spasm with BTX-A injections, are necessary in BEB and HFS.

Comparative Analysis of Refractive Outcomes Following Cataract Surgery Using IOL Master 500 and IOL Master 700 Biometry Devices: A Retrospective Analysis.

Background: This study aims to compare the refractive outcomes of cataract surgery using two different biometry devices, the IOL Master 500 and IOL Master 700, and to investigate the influence of patient-related factors on these outcomes. Methods: In this retrospective study, we analyzed data from 2994 eyes that underwent cataract surgery. Multiple linear regression analyses were performed to examine the impact of the biometry device (IOL Master 500 or IOL Master 700), patient age, time elapsed between biometry and surgery, gender, and insurance status, as well as biometric parameters (anterior chamber depth, axial length, and corneal curvature), on postoperative refractive outcomes, specifically the deviation from target refraction. Results: The choice of the IOL Master device did not result in a statistically significant difference between the two devices (p = 0.205). Age (p = 0.006) and gender (p = 0.001) were identified as significant predictors of refractive outcomes, with older patients and males experiencing slightly more hyperopic outcomes compared to younger patients and females, respectively. The time elapsed between biometry and surgery and insurance status did not significantly influence the refractive outcomes. Conclusions: Our study, supported by a large cohort and a diverse group of patients representing typical anatomical variants seen in cataract surgery, supports the thesis that the IOL Master 500 and IOL Master 700 can be regarded as equivalent and effective for biometry in cataract surgery. The differences between the devices were negligible. Therefore, switching between the devices is safe for bilateral patients.