A new triboelectric nanogenerator based on a multi-material stacking structure achieves efficient power conversion from discrete mechanical movement.

Due to its invaluable potential in discrete mechanical energy collection, TENG (triboelectric nanogenerator) is considered to satisfy the power requirements of intelligent electronic devices and drive the development of the Internet of Things (IoT). Nowadays, the promotion of TENGs has been hindered due to the limitation of their output performance and service life. Herein, a brand new triboelectric nanogenerator based on a multi-material stacking structure is proposed. By stacking various triboelectric materials in a specific order, a special charge balance state could be achieved inside the system such that the conductive layer generates more induced charges, and the output performance is significantly enhanced. Besides, due to the usage of the electropositive elastomer PU (polyurethane sponge), the design also effectively alleviates abrasion on the contact surface and adjusts its own output according to different compression environments. The experimental results show that the stacked PTFE/FKM/PU TENG (PFP-TENG) presents a more than 50% increase in transferred charge and almost 5 times the current output compared with the general contact-separation type TENG. When connected to the application circuit, the maximum output power reached 10.2 W m-2 and 145.2 W m-3, and more than 1400 LEDs could be easily lit. Finally, the PFP-TENG was also used to collect mechanical energy from simple motion and realize considerable power generation. This study not only provides new ideas for the design of TENGs by reasoning the theoretical model but also presents improved output performance, thus exemplifying the strong potential of this design in developing a power-generation device that can collect discrete mechanical energy.

A Stacked FKM/PU Triboelectric Nanogenerator for Discrete Mechanical Energy Harvesting.

To combine the advantages of elastic and nonelastic triboelectric materials, this work proposes a new type of triboelectric nanogenerator (TENG) based on stacking -the stacked FKM/PU TENG. By stacking the elastomer polyurethane (PU) and the nonelastomer fluororubber (FKM), the FKM/PU TENG combines the inherent triboelectric characteristics of both materials and the unique elasticity of PU to achieve an output performance that is much higher than that of the FKM-TENG or the PU-TENG. The maximum instantaneous open-circuit voltage and short-circuit current of the FKM/PU TENG reach 661 V and 71.2 µA, respectively. Under the limiting conditions of 3 Hz and maximum compression, this device can attain a maximum power density of 49.63 W/m3 and light more than 500 LEDs. Therefore, stacking materials with different properties gives the FKM/PU TENG high output performance and great application potential, which can contribute to future development of discrete mechanical energy harvesting.

Causal Relationships Between Glycemic Traits and Myopia.

Purpose: Little is known about whether sugar intake is a risk factor for myopia, and the influence of glycemic control remains unclear, with inconsistent results reported. This study aimed to clarify this uncertainty by evaluating the link between multiple glycemic traits and myopia. Methods: We employed a two-sample Mendelian randomization (MR) design using summary statistics from independent genome-wide association studies. A total of six glycemic traits, including adiponectin, body mass index, fasting blood glucose, fasting insulin, hemoglobin A1c (HbA1c), and proinsulin levels, were used as exposures, and myopia was used as the outcome. The inverse-variance-weighted (IVW) method was the main applied analytic tool and was complemented with comprehensive sensitivity analyses. Results: Out of the six glycemic traits studied, we found that adiponectin was significantly associated with myopia. The genetically predicted level of adiponectin was consistently negatively associated with myopia incidence: IVW (odds ratio [OR] = 0.990; P = 2.66 × 10-3), MR Egger (OR = 0.983; P = 3.47 × 10-3), weighted median method (OR = 0.989; P = 0.01), and weighted mode method (OR = 0.987; P = 0.01). Evidence from all sensitivity analyses further supported these associations. In addition, a higher HbA1c level was associated with a greater risk of myopia: IVW (OR = 1.022; P = 3.06 × 10-5). Conclusions: Genetic evidence shows that low adiponectin levels and high HbA1c are associated with an increased risk of myopia. Given that physical activity and sugar intake are controllable variables in blood glycemia treatment, these findings provide new insights into potential strategies to delay myopia onset.

CMS-NET: deep learning algorithm to segment and quantify the ciliary muscle in swept-source optical coherence tomography images.

Background: The ciliary muscle plays a role in changing the shape of the crystalline lens to maintain the clear retinal image during near work. Studying the dynamic changes of the ciliary muscle during accommodation is necessary for understanding the mechanism of presbyopia. Optical coherence tomography (OCT) has been frequently used to image the ciliary muscle and its changes during accommodation in vivo. However, the segmentation process is cumbersome and time-consuming due to the large image data sets and the impact of low imaging quality. Objectives: This study aimed to establish a fully automatic method for segmenting and quantifying the ciliary muscle on the basis of optical coherence tomography (OCT) images. Design: A perspective cross-sectional study. Methods: In this study, 3500 signed images were used to develop a deep learning system. A novel deep learning algorithm was created from the widely used U-net and a full-resolution residual network to realize automatic segmentation and quantification of the ciliary muscle. Finally, the algorithm-predicted results and manual annotation were compared. Results: For segmentation performed by the system, the total mean pixel value difference (PVD) was 1.12, and the Dice coefficient, intersection over union (IoU), and sensitivity values were 93.8%, 88.7%, and 93.9%, respectively. The performance of the system was comparable with that of experienced specialists. The system could also successfully segment ciliary muscle images and quantify ciliary muscle thickness changes during accommodation. Conclusion: We developed an automatic segmentation framework for the ciliary muscle that can be used to analyze the morphological parameters of the ciliary muscle and its dynamic changes during accommodation.

Time-Serial Evaluation of the Development and Treatment of Myopia in Mice Eyes Using OCT and ZEMAX.

Myopia is a significant cause of visual impairment which may lead to many complications. However, the understanding of the mechanisms of myopia is still limited. In this paper, in order to investigate the development and the treatment of myopia, we analyzed the biological structure parameters of mice eyes, obtained from optical coherence tomography (OCT), and the optical performance of mice eyes calculated using ZEMAX software (ZEMAX Development Corporation, Kirkland, WA, USA) in which the optical model was built on the segment-by-segment optically corrected OCT 3D-images. Time-serial evaluation of three groups of mice eyes (form-deprivation myopia mice eyes, normal mice eyes, and atropine-treated myopia mice eyes) was performed. In addition to the biological structure parameters, imaging performance with the development of root-mean-square wavefront aberration at six filed angles was compared and analyzed. Results show that the biological structure parameters of the eye are closely related to the development of myopia. The peripheral defocus of the retina has a significant impact on inducing myopia, which verifies the new theory of myopia development. The delaying effect of atropine solution on myopia development is shown to verify the therapeutic effect of the medicine. This study provides technical support for the investigation of the myopia mechanism.

Vascular Changes of the Choroid and Their Correlations With Visual Acuity in Pathological Myopia.

Purpose: Photoreceptor loss plays a role in visual impairment in pathological myopia. As the nutrition and oxygen demands of photoreceptors are mainly supported by the choroidal vessels, we aimed to investigate changes in the choroidal vasculature and their correlations with visual acuity in pathological myopia. Methods: The cohort was composed of 136 eyes from 80 participants, including 42 eyes from 21 participants with emmetropia/low myopia, 48 eyes from 26 participants with simple high myopia, and 46 eyes from 33 participants with pathological myopia. Swept-source optical coherence tomography (OCT) was used to image the eyes with a 12-mm radial line scan protocol. The parameters for 6-mm diameters of macula area centered on the fovea were analyzed. A custom deep learning algorithm based on a modified residual U-Net architecture was used to segment the choroidal boundaries. Then, the distance between the two boundaries was determined and choroidal thickness (CT), luminal area (LA), and stromal area (SA) were demarcated based on Niblack's auto-local threshold algorithm after binarization of the OCT images. Finally, the ratio of LA and total choroidal area was defined as the choroidal vascularity index (CVI). The choroidal parameters in three groups were compared, and correlations of the choroidal parameters with age, gender, axial length, and best-corrected visual acuity (BCVA) were analyzed. Results: The CVI, CT, LA, and SA values were lower in pathological myopia than in emmetropia/low myopia and simple high myopia (P < 0.05). The CT, LA, and SA values were lower in simple high myopia than in emmetropia/low myopia (P < 0.05), whereas there was no difference between the CVIs in the emmetropia/low myopia and high myopia groups (P > 0.05). The CVI was nonlinear with increases in axial length (AL), and there was a critical AL flexion point, approximately 27.26 mm; however, the CT, LA, and SA were negatively correlated with AL. Further analysis showed that only younger subjects (40 years old or less) showed significant AL flexion points. Simple and multiple regression models showed that the CVI was correlated with BCVA (P < 0.05). Conclusions: Choroidal vascular alterations, especially decreased CVI, occurred in patients with pathological myopia. The CVI decreased with axial elongation beyond the flexion point and was correlated with visual impairment, indicating that the CVI might be a reliable imaging biomarker to monitor the progression of pathological myopia.

Reduced Radial Peripapillary Capillary in Pathological Myopia Is Correlated With Visual Acuity.

Purpose: To quantify the radial peripapillary capillary (RPC) density and the peripapillary retinal nerve fiber layer (pRNFL) thickness in pathological myopia and examine associations among these factors and best-corrected visual acuity (BCVA). Methods: The cohort was composed of 41 eyes as control and 79 eyes with high myopia (59 simple high myopia, 20 pathological myopia). Optical coherence tomography angiography was done to obtain RPC density and pRNFL thickness, superficial retinal capillary plexus (SRCP), and deep retinal capillary plexus (DRCP) density. The axial length (AL) was measured. Correlations among BCVA, RPC density, pRNFL thickness, AL, and other parameters were determined. Results: For pathological myopia, the densities of RPC, SRCP, and DRCP were significantly less than those of the control and simple high myopia groups (p ≤ 0.005). There was no statistical difference in pRNFL thickness between pathological myopia and simple high myopia (p = 0.063), whereas there was significant difference in global pRNFL thickness between pathological myopia and control (p = 0.008). The global RPC density showed the greatest area under the curve (AUC = 0.962, sensitivity = 94.74%, specificity = 90.00%, cutoff value = 47.8%) for pathological myopia, whereas the AUC of pRNFL thickness, SRCP, and DRCP were only 0.675, 0.824, and 0.865, respectively. The univariate and multiple linear regression models showed that RPC density, SRCP density, and AL were correlated with BCVA (All p < 0.05). In the final BCVA model with multiple generalized estimating equation analysis, AL, RPC density and interaction between RPC and AL were shown (all p < 0.03). For an eye with AL ≥ 27.94 mm, global RPC density was predicted to be less than 48.77% with a high risk of visual impairment. Conclusion: Peripapillary alterations, both the decreasing RPC density and pRNFL thickness, occurred in pathological myopia compared with the control. The RPC density was associated with BCVA, and this relationship was affected by AL.

Visual acuity is correlated with ischemia and neurodegeneration in patients with early stages of diabetic retinopathy.

PURPOSE: We investigated the effects of retinal ischemia, neurodegeneration, and subclinical edema on best-corrected visual acuity (BCVA) in the early stages of diabetic retinopathy (DR). METHODS: Ischemia was evaluated by the microvascular parameters measured by optical coherence tomography angiography. Neurodegeneration and subclinical edema were identified by the intraretinal layer thickness obtained by optical coherence tomography. Eyes with nonproliferative diabetic retinopathy (n = 132) from 89 patients were analyzed. Eyes were classified as having normal BCVA (n = 88 [66.7%], Snellen equivalent ≥ 20/20) or decreased BCVA (n = 44 [33.3%], Snellen equivalent < 20/20). The prevalence of ischemia, neurodegeneration, and subclinical edema was explored in patients with and without decreased BCVA, and correlations between BCVA and these pathological pathways were determined. RESULTS: Vessel density in the deep retinal capillary plexus (DRCP) and thickness of ganglion cell layer plus inner plexiform layer (GCL-IPL) were significantly lower in eyes with decreased BCVA compared with eyes with normal BCVA (both P < 0.05). In the final multiple regression predictive model, age, DRCP vessel density, and GCL-IPL thickness (all P ≤ 0.044) were predictors of BCVA. DRCP vessel density and GCL-IPL thickness have an interactive effect on visual acuity. The proportions of ischemia and neurodegeneration were significantly higher in eyes with decreased BCVA than in eyes with normal BCVA (P = 0.001 and P = 0.004, respectively). CONCLUSION: During the natural course of the early stages of DR, ischemia and neurodegeneration were the main disease pathways associated with visual acuity, and the mechanisms varied among patients.

Impact of Temporal Visual Flicker on Spatial Contrast Sensitivity in Myopia.

PURPOSE: To investigate whether short-term exposure to high temporal frequency full-field flicker has an impact on spatial visual acuity in individuals with varying degrees of myopia. METHODS: Thirty subjects (evenly divided between control and experimental groups) underwent a 5-min exposure to full-field flicker. The flicker rate was lower than critical flicker frequency (CFF) for the experimental group (12.5 Hz) and significantly higher than CFF for the controls (60 Hz). Spatial contrast sensitivity function (CSF) was measured before and immediately after flicker exposure. We examined whether the post flicker CSF parameters were different from the pre-exposure CSF values in either of the subject groups. Additionally, we examined the relationship between the amount of CSF change from pre to post timepoints and the degree of subjects' myopia. The CSF parameters included peak frequency, peak sensitivity, bandwidth, truncation, and area under log CSF (AULCSF). RESULTS: There was no significant difference of all five pre-exposure CSF parameters between the two groups at baseline (P = 0.333 ∼ 0.424). Experimental group subjects exhibited significant (P < 0.005) increases in peak sensitivity and AULCSF, when comparing post-exposure results to pre-exposure ones. Controls showed no such enhancements. Furthermore, the extent of these changes in the experimental group was correlated significantly with the participants' refractive error (P = 0.005 and 0.018, respectively). CONCLUSION: Our data suggest that exposure to perceivable high-frequency flicker (but, not to supra-CFF frequencies) enhances important aspects of spatial contrast sensitivity, and these enhancements are correlated to the degree of myopia. This finding has implications for potential interventions for cases of modest myopia.

Deep Retinal Capillary Plexus Decreasing Correlated With the Outer Retinal Layer Alteration and Visual Acuity Impairment in Pathological Myopia.

Purpose: The purpose of this study was to measure alterations of inner retinal microvascular density and outer retinal sublayer thicknesses in pathological myopia, and to correlate the measured parameters with best corrected visual acuity (BCVA). Methods: Optical coherence tomography (OCT) and OCT angiography (OCTA) images of 21 control, 48 simple high myopia, and 22 pathological myopia eyes were analyzed to quantify the thicknesses of the outer retinal sublayers and the density of the inner retinal microvascular network that includes the superficial retinal capillary plexus (SRCP) and deep retinal capillary plexus (DRCP). Retinal sublayer thicknesses and microvascular densities were compared among the three groups, and correlations of sublayer thicknesses and microvascular densities with BCVA were determined. Results: In pathological myopia, density of the DRCP, thicknesses of myoid and ellipsoid zone (MEZ), interdigitation zone and retinal pigment epithelium/Bruch complex (IZ + RPE), and choroid were lower than in simple high myopia (P < 0.05). The decreased DRCP density was correlated with thinner MEZ and IZ+RPE in pathological myopia (P < 0.05), but not in simple high myopia (P > 0.05). Simple linear regression showed that axial length, female, thicknesses of outer plexiform layer (OPL), MEZ, IZ + RPE, choroid, and density of the SRCP and DRCP were correlated with BCVA. In multiple regression analysis, worse BCVA was associated only with thinner MEZ, thinner choroid, and decreased DRCP (P < 0.05). Conclusions: Alteration of inner retinal microvascular density and outer retinal sublayer thicknesses occurred in pathological myopia, especially decreased DRCP and thinner MEZ, which were significantly associated with worse BCVA.

Relationship Between Cone Loss and Microvasculature Change in Retinitis Pigmentosa.

Purpose: To objectively quantify cone density (CD) and microvascular density (MVD) in normal subjects and patients with moderate or severe retinitis pigmentosa (RP) by adaptive optics (AO) and optical coherence tomography angiography (OCTA) and to evaluate the changes in the parafoveal regions. Method: Thirty-seven eyes from 20 RP patients and 54 eyes from 29 age-matched healthy participants underwent AO fundus and OCTA imaging. AO images covering a 3-mm-diameter area centered on the fovea were subdivided into 5 equidistant concentric rings (C1-C5). An automated algorithm was used to quantify the mean cone density (mCD; cells/mm2). Macular MVDs (%) in the superficial capillary plexus (SCP) and deep capillary plexus (DCP) were assessed by OCTA. Results: In the moderate RP group, CDs in C2 and C3 were each significantly lower than in the normal group (both P < 0.05). In the severe RP group, CDs were significantly lower than in normal eyes in each concentric ring (all P < 0.001; C1-C5). In both RP groups, MVDs were significantly lower than in normal eyes for both the SCP and DCP (both P < 0.05). The mean CD was significantly correlated with the MVD in the DCP (r = 0.43; P = 0.028) but not in the SCP (r = -0.19, P = 0.323). Conclusions: Decreased CD was present in the moderate and severe RP groups. This was accompanied by a decreased MVD in the DCP. Direct assessment of photoreceptors in RP patients by high-resolution imaging technologies is crucial for the future development of RP therapeutics.

Photoreceptor Degeneration is Correlated With the Deterioration of Macular Retinal Sensitivity in High Myopia.

Purpose: To investigate structural changes in the retinal outer layers and choroid using adaptive optics (AO) and optical coherence tomography (OCT) in eyes with myopia, and to correlate the changes with decreased macular light sensitivity (MLS). Methods: This prospective study included 27 subjects with emmetropia and low myopia (EM/LM), 25 with moderate myopia (MM), and 25 with high myopia (HM). Microperimetry was used to quantify MLS in each subject, while AO and OCT images of fundus were analyzed to quantify cone density and regularity and thickness of outer retinal sublayers and choroid. Differences of MLS, cone distribution, and chorioretinal thicknesses were compared among the three groups, and the associations among photoreceptor morphological alterations, MLS, and other parameters were analyzed. Results: In HM, the MLS, cone density and regularity, and thicknesses of the myoid and ellipsoid zone (MEZ), Henle fiber layer and outer nuclear layer, interdigitation zone and RPE/Bruch complex, and choroid were lower than in EM/LM. Decreased MLS was correlated with lower cone density and regularity, and thinner MEZ and choroid in the inner region, and with lower cone density, thinner MEZ and choroid, and longer axial length in the outer region. Multivariate regression showed that better MLS was correlated with thicker MEZ in the inner region and with higher cone density in the outer region. Conclusions: Altered cone distribution and outer retinal thickness, especially cone density and MEZ thickness, were significantly correlated with decline of MLS in HM, which may help to evaluate and monitor visual impairment in HM.

Visual Acuity in Pathological Myopia Is Correlated With the Photoreceptor Myoid and Ellipsoid Zone Thickness and Affected by Choroid Thickness.

Purpose: To quantify the thickness of the outer retinal sublayers and choroid in pathological myopia and examine associations between these factors and best-corrected visual acuity (BCVA). Methods: The cohort was composed of 21 eyes with emmetropia and 70 eyes with high myopia (49 simple high myopia; 21 pathological myopia). Optical coherence tomography images were segmented to determine macular thicknesses of the choroid and the following outer retinal sublayers: outer plexiform layer (OPL), Henle fiber layer and outer nuclear layer (HFL + ONL), myoid and ellipsoid zone (MEZ), outer segment of photoreceptors (OS), and interdigitation zone and RPE/Bruch complex (IZ + RPE). Correlations between BCVA and thickness of the outer retinal sublayers and choroid were determined. Results: In pathological myopia, the choroid, HFL + ONL, MEZ, and IZ + RPE were thinner than in emmetropia and simple high myopia (P < 0.05). Simple and multiple regression models showed that MEZ thickness was correlated with BCVA (both P < 0.001). The relationship between MEZ thickness and BCVA varied with choroidal thickness (P = 0.006). For a constant MEZ thickness, thinner choroids were associated with worse vision. In the final multiple regression predictive model, MEZ thickness, choroidal thickness, and interaction between MEZ and choroidal thickness (all P < 0.001) were predictors of BCVA. Conclusions: Outer retinal alterations, especially thinning of the MEZ, occurred in pathological myopia. The MEZ thickness was associated with BCVA, and this relationship was affected by choroidal thickness.

Long scan depth optical coherence tomography on imaging accommodation: impact of enhanced axial resolution, signal-to-noise ratio and speed.

BACKGROUND: Spectral domain optical coherence tomography (SD-OCT) was a useful tool to study accommodation in human eye, but the maximum image depth is limited due to the decreased signal-to-noise ratio (SNR). In this study, improving optical resolutions, speeds and the SNR were achieved by custom built SD-OCT, and the evaluation of the impact of the improvement during accommodation was investigated. METHODS: Three systems with different spectrometer designs, including two Charge Coupled Device (CCD) cameras and one Complementary Metal-Oxide-Semiconductor Transistor (CMOS) camera, were tested. We measured the point spread functions of a mirror at different positions to obtain the axial resolution and the SNR of three OCT systems powered with a light source with a 50 nm bandwidth, centered at a wavelength of 840 nm. Two normal subjects, aged 26 and 47, respectively, and one 75-year-old patient with an intraocular lens implanted were imaged. RESULTS: The results indicated that spectrometers using cameras with 4096 camera pixels optimized the axial resolutions, due to the use of the full spectrum provided by the light source. The CCD camera system with 4096 pixels had the highest SNR and the best image quality. The system with the CMOS camera with 4096 pixels had the highest speed but had a compromised SNR compared to the CCD camera with 4096 pixels. CONCLUSIONS: Using these three OCT systems, we imaged the anterior segment of the human eye before and after accommodation, which showed similar results among the different systems. The system using the CMOS camera with an ultra-long scan depth, high resolution and high scan speed exhibited the best overall performance and therefore was recommended for imaging real-time accommodation.

Axial elongation measured by long scan depth optical coherence tomography during pilocarpine-induced accommodation in intraocular lens-implanted eyes.

We used an ultra-long scan depth optical coherence tomography (UL-OCT) system to investigate changes in axial biometry of pseudophakic eyes during pilocarpine- induced accommodation. The right eyes from 25 healthy subjects (age range 49 to 84 years) with an intraocular lens (IOL) were imaged twice in the non-accommodative and the accommodative states. A custom-built UL-OCT instrument imaged the whole eye. Then accommodation was induced by two drops of 0.5% pilocarpine hydrochloride separated by a 5-minute interval. Following the same protocol, images were acquired again 30 minutes after the first drop. The central corneal thickness (CCT), anterior chamber depth (ACD), IOL thickness (IOLT), and vitreous length (VL) were obtained using custom automated software. The axial length (AL) was calculated by summing the CCT, ACD, IOLT, and VL. With accommodation, ACD increased by +0.08 ± 0.09 mm, while the VL decreased by -0.04 ± 0.09 mm (paired t-test each, P<0.05). CCT and IOLT remained constant during accommodation (P > 0.05). The non-accommodative AL was 23.47 ± 0.93 mm, and it increased by +0.04 ± 0.04 mm after accommodation (P<0.01). The AL increased and the IOL moved backward during pilocarpine-induced accommodation in pseudophakic eyes.

Real-Time Measurement of Dynamic Changes of Anterior Segment Biometry and Wavefront Aberrations During Accommodation.

OBJECTIVES: To analyze the dynamic relationship between ocular geometrical structure and high-order aberrations (HOAs) in teal-time during accommodation of human eye. METHODS: A custom-built spectral domain optical coherence tomography (OCT) system with high-speed and ultra-long scan depth was used to image the anterior segment, whereas a Shack-Hartmann wavefront sensor was used to detect the whole-eye aberration. A Badal optometer with switched visual targets was integrated with this system to induce 0 and 3.00 D accommodative stimuli. Three young adult subjects were measured and the structural parameters of anterior segment were measured from OCT images and accommodative response and HOAs were calculated and exponentially fitted in real time during the accommodation. RESULTS: The dynamic process from nonaccommodation to 3.00 D accommodation results in reduced pupil diameter, shallower anterior chamber depth, and increased crystalline lens thickness. After an accommodative active time, the RMS of the HOAs changes sharply when an accommodative stimulus is introduced and then tends to be stable. The accommodative response time and velocity are characterized by fitted parameters. The individual differences of changing in HOAs between subjects can be explained by the different sign and changing tendency of certain terms of aberration coefficients in form of Zernike polynomials during the accommodation. CONCLUSIONS: Based on the integrated ocular measurement platform including OCT system and wavefront sensor, our research demonstrated how the morphology of the human anterior segment affect the aberration in real time during accommodation. The dynamic relationship between them helps us to deeply understand the mechanism of accommodation.

Age-related changes in the anterior segment biometry during accommodation.

PURPOSE: We investigated the dynamic response of human accommodative elements as a function of age during accommodation using synchronized spectral domain optical coherence tomography devices (SD-OCT). METHODS: We enrolled 33 left eyes from 33 healthy subjects (age range, 20-39 years, 17 males and 16 females). Two SD-OCT devices were synchronized to simultaneously image the anterior segment through pupil and the ciliary muscle during 6.00 diopter (D) accommodation for approximately 3.7 seconds in two repeated measurements. The anterior segment parameters included the lens thickness (LT), radius of curvature of the lens anterior surface (LAC), maximum thickness of ciliary muscle (CMTMAX), and anterior length of the ciliary muscle (CMAL). A first-order exponential equation was used to fit the dynamic changes during accommodation. The age-related changes in the dynamic response and their relationship were calculated and compared. RESULTS: The amplitude (r = -0.40 and 0.53 for LT and LAC, respectively) and peak velocity (r = -0.65 and 0.71 for LT and LAC, respectively) of the changes in LT and LAC significantly decreased with age (P < 0.05), whereas the parameters of the ciliary muscle remained unchanged (P > 0.05), except for the peak velocity of the CMAL (r = 0.44, P = 0.01). The difference in the time constant between the lens reshaping (LT and LAC) and CMTMAX increased with age (r = 0.46 and 0.57 for LT and LAC, respectively, P < 0.01). The changes in LT and LAC per millimeter of CMTMAX change decreased with age (r = -0.52 and -0.34, respectively, P < 0.05). The ciliary muscle forward movement correlated with the lens deformation (r = -0.35 and 0.40 for amplitude, while r = 0.36 and 0.58 for time constant, respectively, P < 0.05). CONCLUSIONS: Age-related changes in the lens reshaping and ciliary muscle forward movement were found. Lens reshaping was much slower than the contraction of the ciliary muscle, especially in aging eyes, and this process required the ciliary muscle to contract more to reach a given response.

Automatic biometry of the anterior segment during accommodation imaged by optical coherence tomography.

OBJECTIVE: To test accuracy and repeatability of a software algorithm that performs automatic biometry of the anterior segment of the human eye imaged with long scan depth optical coherence tomography (OCT). METHODS: The ocular anterior segment imaging was performed with custom-built long scan depth OCT. An automatic software algorithm including boundary segmentation, image registration, and optical correction was developed for fast and reliable biometric measurements based on the OCT images. The boundary segmentation algorithm mainly used the gradient information of images and applied the shortest path search based on the dynamic programming to optimize the edge finding. The automatic algorithm was validated by comparison of the biometric dimensions between automatic and manual measurements and repeatability study. RESULTS: Biometric dimensions of the anterior segment, including central corneal thickness, anterior chamber depth, pupil diameter, crystalline lens thickness, and radii of curvature of the anterior and posterior surfaces of lens, were obtained by the automatic algorithm successfully. There were no significant differences between the automatic and manual measurements for all biometric dimensions. The intraclass correlation coefficients (ICC) of agreement between automatic and manual measurements ranged from 0.85 to 0.98. The coefficients of repeatability and ICC for all automatic dimensions were satisfactory (1.1%-6.1% and 0.663-0.990, respectively). CONCLUSIONS: The high accuracy, good repeatability, and fast execution speed for automatic measurement of the anterior segment dimensions on the OCT images were demonstrated. The application of this automatic biometry is promising for investigating dynamic changes of human anterior segment during accommodation in real time.

Whole eye axial biometry during accommodation using ultra-long scan depth optical coherence tomography.

PURPOSE: To investigate changes of whole eye axial biometry during accommodation using ultra-long scan depth optical coherence tomography (UL-OCT). DESIGN: Prospective, observational case series. METHODS: Twenty-one adult subjects were enrolled. Using UL-OCT, the left eye of each subject was imaged with relaxed diopters (0 D) and accommodative stimuli (+6 D). Full eye biometry included central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness, vitreous length, and axial length (AL). RESULTS: During accommodation (+6 D), the axial biometry of the whole eye changed significantly. Compared to the rest state, ACD at the accommodative state decreased significantly from 3.128 ± 0.305 mm to 2.961 ± 0.298 mm (paired t test, P < .001). The lens thickness increased significantly from 3.723 ± 0.237 mm to 3.963 ± 0.234 mm (P < .001). The vitreous length decreased significantly from 17.129 ± 0.864 mm to 17.057 ± 0.848 mm (P < .001). AL was 24.519 ± 0.917 mm at the rest state and increased to 24.545 ± 0.915 mm with +6 D accommodation stimulus. The elongated AL of 26.1 ± 13.4 µm between the rest and accommodative states was significant (P < .001). CONCLUSIONS: During accommodation, whole eye axial biometry changed, including a decrease in ACD and vitreous length and an increase in lens thickness and AL. UL-OCT provides an alternative method that is suitable for full eye biometry during accommodation.