Comparison of 2 modern swept-source optical biometers-IOLMaster 700 and Anterion.

PURPOSE: To compare biometric measures from 2 modern swept-source OCT biometers (IOLMaster700 (Z, Carl-Zeiss-Meditec) and Anterion (H, Heidelberg Engineering)) and evaluate the effect of measurement differences on the resulting lens power (IOLP). METHODS: Biometric measurements were made on a large study population with both instruments. We compared axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT) and corneal front and back surface curvature measurements. Corneal curvature was converted to power vectors and total power derived using the Gullstrand formula. A paraxial lens power calculation formula and a prediction for the IOL axial position according to the Castrop formula were used to estimate differences in IOLP targeting for emmetropia. RESULTS: There were no systematic differences between measurements of AL (- 0.0146 ± 0.0286 mm) and LT (0.0383 ± 0.0595 mm), whereas CCT yielded lower (7.8 ± 6.6 µm) and ACD higher (0.1200 ± 0.0531 mm) values with H. With H, CCT was lower for thicker corneas. The mean corneal front surface radius did not differ (- 0.4 ± 41.6 µm), but the corneal back surface yielded a steeper radius (- 397.0 ± 74.6 µm) with H, giving lower mean total power (- 0.3469 ± 0.2689 dpt). The astigmatic vector components in 0°/90° and 45°/135° were the same between both instruments for the front/back surface or total power. CONCLUSION: The biometric measures used in standard formulae (AL, corneal front surface curvature/power) are consistent between instruments. However, modern formulae involving ACD, CCT or corneal back surface curvature may yield differences in IOLP, and therefore, formula constant optimisation customised to the biometer type is required.

Feasibility and repeatability of ocular biometry measured with IOLMaster 700 in a large population-based study.

PURPOSE: To evaluate the feasibility and repeatability of IOLMaster 700 biometry measurements in an adult population. Furthermore, to assess the value of the Quality Indicators (QIs) provided by the device. METHOD: As part of the large population-based Leipzig Research Centre for Civilization Diseases (LIFE) Adult-Study, randomly selected participants from Leipzig, Germany were evaluated with the ZEISS IOLMaster 700. Age range was 26-85 years, with 53% of participants above 70 years of age. Axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT) and keratometry (K) were assessed in 1767 right eyes. Measurements were repeated twice and in a subset of 1331 eyes, three times. Measurement feasibility was evaluated for three levels; successful, with warnings and failed, using the inbuilt QIs. Repeatability was assessed as within-subject standard deviation (SD) and repeatability limits were calculated. RESULTS: First measurement success rate for phakic eyes was over 99% for AL, CCT, ACD, over 98% for LT and over 97% for K. K had 16% eyes with warnings and the recommendation to repeat the measurement. Excluding the measurements with warnings resulted in a reduction of mean SD for AL from 48 to 4 µm and for mean K from 0.08 to 0.04 D. Repeatability for phakic eyes was 8 µm for AL, CCT, ACD and LT and 2.3 µm for CCT; 0.07 D and 0.12 D for mean K and delta K, respectively, for phakic cases without warnings (two measurements). CONCLUSIONS: In our population-based sample, the IOLMaster 700 collected data for AL, CCT, ACD, LT and K from the vast majority of eyes. Considering the built-in QIs improved the measurement variability substantially. Repeatability measurements indicate that clinically meaningful changes can be detected reliably with this instrument.

Comparison Between Ocular Biometric Parameters and Intraocular Pressure With and Without Contact Lenses.

OBJECTIVES: To compare the values of central corneal thickness, anterior chamber depth (ACD), lens thickness (LT), vitreous length (VL), axial length (AL), and corneal-compensated intraocular pressure performed with and without contact lenses (CL). METHODS: Forty volunteer participants (16 men and 24 women, 24.2±2.9 years) were recruited. In a single visit, participants underwent autorefraction, keratometry, biometry, topography, pachymetry, and tonometry with the naked eye (without CL). Then, biometry, pachymetry, and tonometry were repeated twice wearing two CL (somofilcon A and nesofilcon A) fitted in a random order. RESULTS: Many of the ocular biometric values were affected by the use of CL during measurements (paired t test; all P ≤0.003), except for LT and VL (Wilcoxon test; both P ≥0.272). Corneal-compensated intraocular pressure was also affected by contact lens wear during measurements, obtaining lower values when wearing them (Wilcoxon test; all P ≤0.001). CONCLUSIONS: Central corneal thickness, ACD, AL, and corneal-compensated intraocular pressure measurements cannot be performed while wearing CL. However, LT and VL measurements were not affected by any contact lens use. In addition, it was observed that ACD results from both devices are not interchangeable either when measured with the naked eye or using any contact lens.

Comparing low-coherence interferometry and A-scan ultrasonography in measuring ocular axial dimensions in young rhesus monkeys.

We investigated a commercial low-coherence interferometer (LenStar LS 900 optical biometer) in measuring young rhesus monkey ocular dimensions. Ocular biometry data obtained using a LenStar and an A-scan ultrasound instrument (OPT-scan 1000) from 163 rhesus monkeys during 20-348 days of age were compared by means of coefficients of concordance and 95% limits of agreement. Linear regression was employed to examine and analyze the inter-instrument discrepancies. In young rhesus monkeys, the test-retest reliability of the LenStar was equal to or exceeded that of A-scan ultrasound (intraclass correlation = 0.86 to 0.93). The inter-instrument agreement was strong for vitreous chamber depth and axial length (coefficient of concordance = 0.95 and 0.86, respectively) and moderate for anterior chamber depth and lens thickness (coefficient of concordance = 0.74 and 0.63, respectively). The LenStar systematically underestimated ocular dimensions when compared to A-scan ultrasound (mean magnitude of difference = 0.11-0.57 mm). This difference could be minimized using linear calibration functions to equate LenStar data with ultrasound data. When this method was applied, the values between instruments were in excellent absolute agreement (mean magnitude of difference = 0.004-0.01 mm). In conclusion, the LenStar reliably measured ocular dimensions in young monkeys. When an appropriate calibration function is applied, the LenStar can be used as a substitute for A-scan ultrasonography.

Biometry of the human cornea and globe: An evaluation by age, gender and population.

The purpose of this study was to examine the effects of age, gender and population origin on human globe and corneal dimensions and to explore the relationships between the dimensions. Human post-mortem eyes were obtained in Hyderabad (n = 223; range, 0-85 years) and Miami (n = 486; range, 6-103 years). The eyes were freed of extraneous tissues and globe antero-posterior length (GAPL), mean globe diameter (MGD) (average of horizontal and vertical), and corneal horizontal (HCD) and vertical (VCD) diameters were measured using digital calipers. The relationships of age, gender and population origin with globe and corneal dimensions and the relationships between the dimensions were assessed by bivalent and multiple regression analyses. Globe and cornea dimensions increase asymptotically with age until around the late teens but do not change thereafter. Bivariate and multivariate regression analyses of the >20-year-old eyes showed that population was significantly correlated with GAPL, MGD, HCD and VCD. Male globes and corneas were larger than those from females, but the difference did not appear to be statistically significant. All Hyderabad dimensions were significantly larger than those from the Miami. Neither GAPL nor MGD were correlated with the corneal dimensions. GAPL was significantly correlated with MGD as was HCD with VCD.

Repeatability of a new swept-source optical coherence tomographer and agreement with other three optical biometers.

PURPOSE: To investigate the repeatability of Anterion and compare the agreement of ocular biometric measurements and predicted intraocular lens (IOL) powers with other three optical biometers. METHODS: Flat keratometry (Kf), steep keratometry (Ks), J0 and 45 vectors, central cornea thickness (CCT), anterior chamber depth (ACD), and axial length (AL) from the Anterion, IOLMaster 700, Lenstar LS 900, and OA-2000 were recorded. The IOL powers were calculated with the Hoffer Q, Holladay 1, SRK/T, and Haigis formulas. The repeatability was evaluated using the within-subject standard deviation (Sw), repeatability coefficient (RC), coefficient of variation (COV), and intraclass correlation coefficient (ICC). Inter-device agreement between the four biometers was assessed with the 95% limits of agreement. RESULTS: In total, 101 right eyes of 101 participants were enrolled. The Anterion showed good repeatability for all the included biometric parameters with all the CoV ≤ 0.30% and ICC ≥ 0.930 except for J45 with moderate repeatability (ICC was 0.849). Good agreement was found among the four devices for Kf, Ks, J0, J45, ACD, and AL. Generally, wide 95% LoA was found for the predicted IOL powers with the four IOL calculation formulas between the four devices. CONCLUSIONS: The Anterion showed good repeatability of biometric measurements for most parameters. Good agreement among the four optical biometers was achieved for all the parameters except for CCT and the predicted IOL power. The AL values exhibited the best repeatability with Anterion and the best agreement among the biometers in our study.

Ocular biometry with swept-source optical coherence tomography-based optical biometer in Japanese patients with EYS-related retinitis pigmentosa: a retrospective study.

BACKGROUND: This study aimed to identify the features of ocular biometry in patients with EYS-related retinitis pigmentosa using IOLMaster 700. METHODS: We retrospectively reviewed the medical records of patients with retinitis pigmentosa. Patients with records of the following were included: (1) ocular biometry measurements using the IOLMaster 700 and (2) genetic diagnostic tests. Axial length, keratometry, anterior chamber depth, aqueous depth, lens thickness, central corneal thickness (CCT), and corneal diameter (white to white) measurements were extracted. Based on keratometry measurements, (1) standard keratometric astigmatism, (2) posterior corneal astigmatism, and (3) total corneal astigmatism were obtained. Demographics and biometric parameters were compared between patients with EYS-related retinitis pigmentosa and other patients with retinitis pigmentosa. RESULTS: A total of 86 eyes of 44 patients (23 females and 21 males; mean age: 47.7 years) with retinitis pigmentosa were included. Of these, 18 were identified as having EYS variants. CCT was significantly thinner (P < 0.001) and the posterior corneal curvature at the steepest meridian was significantly smaller (P = 0.024) in patients with EYS-related retinitis pigmentosa than in other patients with retinitis pigmentosa. The magnitudes of all corneal astigmatism measurements was higher in patients with EYS-related RP, although these differences were not statistically significant. CONCLUSION: Patients with EYS-related retinitis pigmentosa had unique features in ocular biometry, such as thinner central corneal thickness and smaller posterior corneal curvature radius at the steepest meridian compared with other patients with retinitis pigmentosa. The findings suggest that patients with retinitis pigmentosa have different ocular dimension features among the different causative genes.

Measuring axial length of the eye from magnetic resonance brain imaging.

BACKGROUND: Metrics derived from the human eye are increasingly used as biomarkers and endpoints in studies of cardiovascular, cerebrovascular and neurological disease. In this context, it is important to account for potential confounding that can arise from differences in ocular dimensions between individuals, for example, differences in globe size. METHODS: We measured axial length, a geometric parameter describing eye size from T2-weighted brain MRI scans using three different image analysis software packages (Mango, ITK and Carestream) and compared results to biometry measurements from a specialized ophthalmic instrument (IOLMaster 500) as the reference standard. RESULTS: Ninety-three healthy research participants of mean age 51.0 ± SD 5.4 years were analyzed. The level of agreement between the MRI-derived measurements and the reference standard was described by mean differences as follows, Mango - 0.8 mm; ITK - 0.5 mm; and Carestream - 0.1 mm (upper/lower 95% limits of agreement across the three tools ranged from 0.9 mm to - 2.6 mm). Inter-rater reproducibility was between - 0.03 mm and 0.45 mm (ICC 0.65 to 0.93). Intra-rater repeatability was between 0.0 mm and - 0.2 mm (ICC 0.90 to 0.95). CONCLUSIONS: We demonstrate that axial measurements of the eye derived from brain MRI are within 3.5% of the reference standard globe length of 24.1 mm. However, the limits of agreement could be considered clinically significant. Axial length of the eye obtained from MRI is not a replacement for the precision of biometry, but in the absence of biometry it could provide sufficient accuracy to act as a proxy. We recommend measuring eye axial length from MRI in studies that do not have biometry but use retinal imaging to study neurodegenerative changes so as to control for differing eye size across individuals.

An evaluation of the IOLMaster 700 and its agreement with the IOLMaster v3 in children.

PURPOSE: To evaluate the repeatability and reproducibility of the swept-source optical coherence tomographer Zeiss IOLMaster 700 and compare its outputs with those obtained using partial coherence interferometry (Zeiss IOLMaster v3) in a healthy, paediatric population. METHODS: This is a cross-sectional, observational study. Examiner 1 took two sets of biometric measurements (axial length [AL], mean corneal radius of curvature [Kmean ], anterior chamber depth [ACD] and lens thickness [LT]) using the IOLMaster 700, and one set of measurements (AL, Kmean and ACD) using the IOLMaster v3. Examiner 2 took one full set of measurements using the IOLMaster 700. Mean differences and 95% limits of agreement (LOA) were calculated, and Bland and Altman plots used to explore repeatability and reproducibility of the IOLMaster 700 alongside establishing its agreement with the IOLMaster v3. RESULTS: Mean participant age was 7.52 ± 0.58 years. Repeatability analyses demonstrated small mean differences and narrow 95% LOA for AL (0.001, -0.013 to 0.015 mm), Kmean (0.002, -0.020 to 0.024 mm), ACD (-0.003, -0.031 to 0.024 mm) and LT (0.001, -0.024 to 0.026 mm), respectively. Similarly, small mean differences and narrow 95% LOA established excellent reproducibility (AL 0.001, -0.016 to 0.018 mm; Kmean -0.001, -0.027 to 0.025 mm; ACD -0.010, -0.041 to 0.021 mm; LT 0.002, -0.016 to 0.020 mm). The IOLMaster 700 and IOLMaster v3 demonstrated good agreement with small mean differences and narrow 95% LOA (AL 0.009, -0.034 to 0.052 mm; Kmean 0.016, -0.013 to 0.044 mm; ACD 0.134, 0.055 to 0.212 mm). CONCLUSIONS: When used within a paediatric population, these data demonstrate the IOLMaster 700 to be highly repeatable and reproducible for measures of AL, Kmean , ACD and LT. There is excellent inter-instrument agreement between the IOLMaster 700 and IOLMaster v3 for measures of AL and Kmean . ACD measurements show weaker agreement. These data will be useful when considering reports from population-based studies of refractive error and clinical myopia research.

Normal range of ocular biometry in healthy children: A systemic review and meta-analysis of 33,559 individuals under seven years of age.

PURPOSE: To conduct a systemic review and meta-analysis on the normative range of ocular biometry in healthy children under seven years of age. METHODS: A literature search was performed using the PubMed (MEDLINE) database. The main outcomes were normative values of axial length (AL), central corneal thickness (CCT), cornea curvature (CC), anterior chamber depth (ACD), lens thickness (LT) and vitreous chamber depth (VCD). Pooled estimates were obtained with a random-effects meta-analysis. Multivariate meta-regressions ascertained the moderator-related trends. RESULTS: We included 47 studies for a total of 33,559 subjects. The pooled ALs for 0.0-1.9 years, 2.0-3.9 years and 4.0-6.9 years were 18.33 mm (95% confidence interval [CI] 17.57-19.09), 21.71 mm (21.49-21.93) and 22.37 mm (22.29-22.45), respectively. Children aged 0.0-1.9 years had a greater CCT (576.70 µm, 567.20-586.21), steeper cornea (7.41 mm, 7.16-7.65) and shallower ACD (2.46 mm, 2.23-2.69). LT ranged from 3.65 to 3.74 mm for 0-6 years, and VCD increased from 11.94 mm at birth to 15.36 mm at 4.0-6.9 years. Differences in AL between East Asian and non-East Asian children were found below two years of age (17.30 mm vs. 18.40 mm, p = 0.008) and for CC at 4.0-6.9 years of age (7.82 mm vs. 7.79 mm, p = 0.004). In a multivariate meta-regression, AL, CC, ACD and VCD increased with age (p < 0.05 for all), while CCT decreased with age (p = 0.0007). CONCLUSIONS: This study reports normative data for ocular biometry in children. Few differences were found with ethnicity in the ocular biometry of infants and pre-schoolers.

Comparison of A-Scan ultrasonography and the Lenstar optical biometer in Guinea pig eyes.

OBJECTIVE: To compare the biometric parameters provided by A-scan ultrasonography and the Lenstar optical biometer in guinea pig eyes, including anterior segment depth (ASD), lens thickness (LT), vitreous chamber depth (VCD), and axial length (AL), and differences of them between treated form deprivation (FD) eyes and untreated fellow eyes after 4 weeks of FD. METHODS: Three-week-old guinea pigs (N = 41) were subjected to biometric measurements before monocular FD (baseline) and after a 4-week FD. Statistical analyses including within-subject standard deviation (SDwithin), coefficient of variation (CV), and intraclass correlation coefficient (ICC), used to evaluate repeatability for both the A-scan ultrasonography and the Lenstar individually, and correlation and Bland-Altman analyses were used to assess agreement between the two methods. The absolute values of ASD, LT, VCD and AL as measured by the two devices were compared, and the differences of them between treated (T) and untreated fellow (F) eyes (ΔASD, ΔLT, ΔVCD and ΔAL) (Δ = T-F) were compared between the two devices after 4 weeks of FD. RESULTS: Measurements by the Lenstar (ICC: 0.923-0.994) were more repeatable than A-scan ultrasonography (ICC: 0.825-0.870). There was a high correlation for AL (r = 0.851, P < 0.001), a moderate correlation for VCD (r = 0.571, P < 0.001) and LT (r = 0.423, P < 0.001), and a low correlation for ASD (r = 0.230, P < 0.01) between the two devices. The values for ASD, VCD and AL measured by A-scan ultrasonography were larger than those measured by the Lenstar (all, P < 0.001), while LT provided by A-scan ultrasonography was much smaller than that of the Lenstar (P < 0.001). Bland-Altman plots showed poor agreement of absolute values of the four parameters between the two devices. Moreover, there was a high correlation between both methods for ΔAL (r = 0.704, P < 0.001), a moderate correlation for ΔVCD (r = 0.534, P < 0.001) and ΔASD (r = 0.574, P < 0.001), and no correlation for ΔLT (r = 0.303, P = 0.054). The ΔASD, ΔLT, and ΔAL measurements obtained by A-scan ultrasonography were greater than those obtained by the Lenstar (all, P < 0.001), while ΔVCD was mildly smaller using A-scan ultrasonography (P < 0.05). Bland-Altman plots illustrated there is good agreement of ΔAL, ΔVCD, ΔASD, and ΔLT between the two devices. CONCLUSIONS: The Lenstar exhibited better repeatability and provided smaller measurements for AL, VCD and ASD than A-scan ultrasonography. Furthermore, a high correlation and a good agreement for the ΔAL was observed between the two devices after a period of FD. In summary, the two devices cannot replace each other directly to obtain absolute values of ASD, LT, VCD and AL, but the Lenstar still can serve as an option in measuring ΔAL between eyes in guinea pig myopia model.

Comparison of ocular biometric measurements in patients with cataract using three swept-source optical coherence tomography devices.

BACKGROUND: Precise measurement of ocular biometry is critical for determining intraocular lens power. Newly developed swept-source optical coherence tomography (SS-OCT) - based ocular biometric devices, ANTERION and CASIA2 provide ocular biometric measurements as IOLMaster 700. This study aimed to assess agreement between three devices. METHODS: This retrospective comparative study includes patients with cataract who underwent ocular biometric measurements with three devices, ANTERION, CASIA2, and IOLMaster 700, at Seoul National University Hospital, in April 2020. Anterior keratometry, total keratometry, central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), and axial length (AL) were the main parameters for the comparison. To assess the agreement between the devices, intraclass coefficient (ICC) and Bland-Altman analysis with 95% limits of agreement (LoA) were used. RESULTS: A total of 47 eyes of 29 patients were measured with three devices. Average anterior keratometry showed excellent agreement (ICC ≥ 0.989), and the mean difference was less than 0.1 D. However, the ICC of the total average keratometry ranged from 0.808 to 0.952, and the difference was more than 0.43 D. The AL measured by ANTERION and IOLMaster 700 showed excellent agreement (ICC = 0.999), and the mean difference was 0.005 mm. The ANTERION and IOLMaster 700 did not obtain AL in six (12.8%) and three (6.4%) cases, respectively (P = 0.001 by Fisher's exact test). The CCT, ACD, and LT also showed excellent agreement (ICC > 0.9). CONCLUSIONS: The new SS-OCT-based devices, ANTERION, and CASIA2 showed a good agreement with IOLMaster 700 in measuring ocular biometry except for the total keratometry. The AL of ANTERION and IOLMaster 700 showed excellent agreement.

Distribution of ocular biometric parameters and optimal model of anterior chamber depth regression in 28,709 adult cataract patients in China using swept-source optical biometry.

BACKGROUND: The purpose of this study was to evaluate the ocular biometric parameters in adult cataract patients from China and create an anterior chamber depth (ACD) regression model. METHODS: The ocular biometric records of 28,709 right eyes of cataract surgery candidates who were treated at Aier Eye Hospitals in nine cities from 2018 to 2019 were retrospectively analyzed. All measurements were taken with IOLMaster 700. We included patients who were at least 40 years old and were diagnosed with cataract. RESULTS: The mean age of the patients was 68.6 ± 11.0 years. The mean values recorded were as follows: axial length (AL), 24.17 ± 2.47 mm; mean keratometry (Km) value, 44.26 ± 1.70 D; corneal astigmatism (CA), 1.06 ± 0.96 D; ACD, 3.02 ± 0.45 mm; lens thickness (LT), 4.52 ± 0.45 mm; central corneal thickness (CCT), 0.534 ± 0.04 mm; and white to white (WTW) corneal diameter, 11.64 ± 0.46 mm. ACD correlated positively with AL (Spearman coefficient, 0.544) and WTW (0.300), but negatively with LT (-0.660) and age (-0.285) (all P < 0.01). In the multivariate regression analysis of ACD, which included LT, AL, WTW, sex, Km, CCT, and age, there was a reasonable prediction with adjusted R2 = 0.641. CONCLUSIONS: Cataract patients with longer AL and wider WTW have deeper ACD. With increasing age and lens thickening ACD becomes shallower. Based on the standardized coefficients of ACD multivariate regression analysis from the study, LT is the main factor that affects ACD, and is followed by AL.

Age-related axial length changes in adults: a review.

PURPOSE: To investigate the origins of age-related decreases in axial length in the literature. METHODS: A literature review was performed, including all articles regarding axial length changes with age. These data were combined with mean body length and education level for the countries of each study to assess their influence in a multivariate analysis. Furthermore, analyses were performed of how optical path length, used by optical biometers to measure axial length, is affected by the known age-related changes in the crystalline lens. The influence of other factors mentioned in the literature was also investigated. RESULTS: Seventeen cross-sectional studies were found that met the search criteria. The decrease in axial length over time was consistent across most of these studies. However, when plotted as a function of year of birth, mean body length and number of years in school, the data indicated an increase in length. Multivariate analysis confirmed the influence of body length (P = 0.005) and birth year (P = 0.017), but not age (P = 0.50). Meanwhile, the lenticular changes due to aging and cataract formation cause a minor bias in the form of increased axial length measurements. Finally, a gradual thinning of the choroidal arteries was reported to cause an increase in axial length. CONCLUSION: The age-related decrease in axial length is mainly associated with gradual changes in increased body length and education level, while attenuated by minor biases in measurement procedure and thinning of the choroidal arteries.

Changes in ocular biometry during short-term accommodation in children.

PURPOSE: Near work has been linked with myopia development; however, the underlying mechanism remains unclear. Small increases in axial length during accommodation have previously been reported in adults, and therefore, this study aimed to examine if accommodation-induced changes in ocular biometry also occur in school-aged children. METHODS: A range of ocular biometric measurements were captured during brief accommodation tasks at four demands (0, 3, 6, and 9 D), in a group of 87 non-myopic, school-aged children using a Badal optometer mounted to a non-contact optical biometer (Zeiss IOLMaster 700, https://www.zeiss.com/meditec/int/product-portfolio/optical-biometers/iolmaster-700.html). Reliable biometry measurements and active accommodation were observed for 76 participants who were included in the analysis. The average central corneal thickness (CCT), anterior chamber depth (ACD), crystalline lens thickness (LT), anterior segment length (ASL), vitreous chamber depth (VCD), and axial length (AL) were determined for each accommodation demand. Raw measurements of AL and VCD were corrected to account for the effect of LT changes during accommodation. RESULTS: On average, AL increased with increasing levels of accommodation (p = 0.005). The mean (SEM, standard error of the mean) AL increase from 0 D to the 3, 6, and 9 D demands was 4 (1), 8 (1), and 15 (2) µm, respectively. All other biometric parameters, except CCT, changed significantly during accommodation. LT and ASL increased, and ACD and VCD decreased significantly with increasing accommodation (all p ≤ 0.02). A longer baseline AL was associated with greater levels of accommodation-induced axial elongation at the 9 D demand (p < 0.0001). CONCLUSIONS: AL increased significantly during accommodation in children, consistent with previous findings in adults up to a 6 D demand. AL continued to increase for higher levels of accommodation (9 D demand), which children may experience during near tasks. These findings provide further insights into potential mechanisms linking near work, axial elongation, and myopia development. However, no myopic children participated in this experiment; therefore, further research is required.

Assessment of Macular Microvasculature in Healthy Eyes of Infants and Children Using OCT Angiography.

PURPOSE: To assess macular vasculature in healthy infants and children using OCT angiography (OCTA). DESIGN: Prospective cross-sectional study. PARTICIPANTS: One hundred thirty-five normal maculae of 89 healthy infants and children (mean age, 8.5±5.3 years; range, 9 weeks-17 years) treated at the Duke University Eye Center. METHODS: We imaged 135 maculae of 89 pediatric patients using the standard Spectralis tabletop and investigational Spectralis with Flex module devices, both equipped with investigational OCTA software (Heidelberg Engineering, Heidelberg, Germany). OCT angiography images of the superficial vascular complex (SVC) and deep vascular complex (DVC) were analyzed for foveal avascular zone (FAZ) area and superficial and deep vessel density. We assessed effects of age, gender, race, axial length (AL), and central subfield thickness on FAZ and vessel density. Patients with both eyes imaged were assessed for agreement between the FAZ and vessel densities of the left and right eyes. MAIN OUTCOME MEASURES: The FAZ area, as well as vessel area density (VAD) and vessel length density (VLD) in the SVC and DVC. RESULTS: The FAZ varied significantly with race; white patients showed a significantly smaller FAZ than black patients (mean difference, 0.11 mm2; P = 0.004). The FAZ did not vary with age, gender, or AL (P > 0.05). In the SVC, VAD and VLD varied significantly with age (P < 0.001) and AL (R2 = 0.46; P < 0.001) but not gender (P > 0.05). The SVC VLD was significantly different between races and ethnicities (P = 0.037), but VAD was not (P < 0.05). In the DVC, VAD and VLD also varied significantly with age (P < 0.001) and AL (R2 = 0.46; P < 0.001) but not gender or race (P > 0.05). There was excellent agreement between the right and left eyes for FAZ (intraclass correlation [ICC], 0.97), SVC VLD (ICC, 1.00), and DVC VLD (ICC, 1.00). CONCLUSIONS: Quantitative studies of pediatric perifoveal vasculature should consider age, race, and AL. In eyes with unilateral disease, the perifoveal vasculature in the unaffected eye may be used as a control comparison because there is excellent agreement between eyes.

Matching the LenStar optical biometer to A-Scan ultrasonography for use in small animal eyes with application to tree shrews.

We describe an analysis strategy to obtain ultrasonography-matched axial dimensions of small animal eyes using the LenStar biometer. The LenStar optical low-coherence reflectometer is an attractive device for animal research due to its high precision, non-invasiveness, and the ability to measure the axial dimensions of cornea, anterior chamber, lens, vitreous chamber, and axial length. However, this optical biometer was designed for clinical applications in human eyes and its internal analysis provides inaccurate values when used on small eyes due to species-dependent differences in refractive indices and relative axial dimensions. The LenStar uses a near infrared light source to measure optical path lengths (OPLs) that are converted by the LenStar's EyeSuite software into geometrical lengths (GLs) based on the refractive indices and axial dimensions of the human eye. We present a strategy that extracts the OPLs, determines refractive indices specific for the small animal eye of interest and then calculates corrected GLs. The refractive indices are obtained by matching the LenStar values to ultrasonography values in the same eyes. As compared to ultrasounography, we found that the internal calculations of the LenStar underestimate the axial dimensions of all ocular compartments of the tree shrew eye: anterior segment depth by 6.17±4.50%, lens thickness by 1.37±3.06%, vitreous chamber depth by 29.23±2.35%, and axial length by 10.62±1.75%. Using tree shrew-specific refractive indices, the axial dimensions closely matched those measured by ultrasonography for each compartment. Our analysis strategy can be easily translated to other species by obtaining a similar paired data set using ultrasonography and LenStar, and applying our step by step procedures.

In vivo imaging of the fibrillar architecture of the posterior vitreous and its relationship to the premacular bursa, Cloquet's canal, prevascular vitreous fissures, and cisterns.

PURPOSE: To describe the fibrillar architecture of the posterior cortical vitreous and identify variations across eyes of different axial lengths in vivo. METHODS: Sixty-four eyes of 32 subjects were examined with swept-source optical coherence tomography (SS-OCT). Grading of vitreous degeneration, presence of vitreous cisterns/lacunae, posterior hyaloid status, directionality of vitreous fibers and their relations to vitreous spaces, and lamellar reflectivity of the posterior vitreous were assessed. RESULTS: A consistent pattern of fibrillar organization was discovered. Eyewall parallel fibers formed a dense meshwork over the retinal surface and fibers oriented in a perpendicular fashion to this meshwork were found to envelop the various vitreous spaces, intersecting at variable angles of insertion to the eyewall parallel fibers. Lamellar reflectivity suggestive of splitting of the cortical fibrillar meshwork was detected in 27 eyes (42%) with 56% of these eyes demonstrating perpendicularly oriented intersecting fibers. Fifty-six percent of eyes with lamellar reflectivity had an axial length > 25 mm. CONCLUSION: SS-OCT imaging revealed fibrillar organization of the posterior vitreous. Eye wall parallel hyperreflectivity of cortical vitreous was a universal finding. This pattern is suggestive of a splitting of cortical vitreous tissue and may represent a precursor to vitreoschisis. Perpendicular fibers appear to be important constituents of the walls of the various liquid vitreous spaces.

Growth in foetal life, infancy, and early childhood and the association with ocular biometry.

PURPOSE: Ocular biometry varies within groups of emmetropic, hyperopic or myopic children. The aim of this study was to quantify the effect of foetal and infant growth on ocular biometry in early childhood, to determine the most important period for this association, and to examine genetic overlap with height and birth weight. METHODS: 5931 children (50.1% girls) from a population-based prospective birth cohort study underwent intra-uterine and infant growth measurements at second and third trimester, and from birth to 72 months. An ophthalmic examination including axial length (mm) and corneal radius of curvature (mm) was performed at 6 years of age. The associations between prenatal and postnatal growth variables and axial length and corneal radius of curvature were assessed with conditional linear regression analyses. Weighted genetic risk scores for birth weight and height were calculated and causality was tested with Mendelian randomisation. RESULTS: Weight and length from mid-pregnancy to 2 years of age were most important prognostic factors for axial length and corneal radius of curvature at age 4.9-9 years (mean 6.2 years S.D. 0.5). For height (Standard deviation score), the association with axial length and corneal radius of curvature was highest for the measurement at 12 months (ß 0.171 p < 0.001 and 0.070 p < 0.001). The genetic height and birth weight risk scores were both significantly associated with ocular biometry. CONCLUSIONS: Larger neonates had longer axial length and greater corneal radius of curvature. Growth during pregnancy and 2 years postnatally is the most important period underlying this association and may be partly genetically determined by genes associated with height.

Refractive Error in Chinese Preschool Children: The Shanghai Study.

PURPOSE: To examine the prevalence of refractive error and some associated factors in Chinese preschool children. METHODS: The Jinshan District Eye Study was a school-based survey of eye health in a large sample of 4- to 6-year-olds attending kindergartens from May 2013 to December 2013 in Shanghai. Refractive error was measured using an autorefractor under noncycloplegic conditions. Axial length (AL) was measured with an ocular biometry system. In addition, body height and weight were also recorded. RESULTS: A total of 7,166 children successfully completed their refraction measurements. The median (interquartile range) of spherical equivalent (SE) for all the children was +0.25 D (-0.13 D to +0.62 D), and the range was -15.88 to +18.13 D. The mean AL for all the children was 22.35±0.70 mm, and the range was 18.20 to 27.71 mm. The overall prevalence of myopia (-1.00 D or less), hyperopia (+2.00 D or greater), and astigmatism (1.00 D or greater) were 5.9%, 1.0%, and 12.7%, respectively. After multivariate analysis, more myopic SE (or less hyperopic SE) was significantly associated with girls, longer AL, taller, and lighter. CONCLUSION: Shanghai has a high prevalence of refractive error in the world. However, longitudinal studies are needed to evaluate refractive changes over time in individual children and warranted to prevent the development of myopia.