Ultrasonographic Assessment and Ocular Biometry of Brown Hawk Owls (Ninox scutulata).

Determinants of Anterior Chamber Depth: The Singapore Chinese Eye Study

PurposeTo understand the ocular biometric parameters characteristics and refractive errors in 3-to 6-year-old preschool children in Chengdu, China, and to investigate the prevalence of refractive errors.MethodA school-based cross-sectional study was conducted in Chengdu from 2020 to2022 with a total of 666 kindergartens. All children were measured by non-cycloplegic autorefraction and uncorrected visual acuity (UCVA) and ocular biometric parameters. Finally, univariate linear regression models were used to analyze the relationship between ocular biometric parameters and refraction.ResultsA total of 108,578 preschool children aged 3–6 underwent examinations, revealing a myopia prevalence of 6.1%. The mean axial length (AL), keratometry (K), corneal radius (CR), axial length/corneal radius (AL/CR) Ratio, central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), and vitreous chamber depth (VCD) were 22.35 ± 0.69 mm, 43.35 ± 1.58 D, 7.80 ± 0.28 mm, 2.87 ± 0.08, 533.31 ± 32.51 μm, 2.70 ± 0.28 mm, 3.91 ± 0.27 mm, and 15.20 ± 0.68 mm, respectively. With increasing age, AL, CR, AL/CR ratio, CCT, ACD, LT, and VCD also increased. Regardless of age, males consistently exhibited longer AL, flatter corneal curvature, shallower ACD, thicker CCT, thinner LT, and longer VCD compared to females. AL, K, CR, LT, and VCD all showed significant linear relationships with SE (all P < 0.001) in univariate linear regression analysis after adjusting for gender and age.ConclusionThe prevalence of myopia among preschool children aged 3–6 in Chengdu is relatively low. Ocular biometric parameters affecting refractive errors include AL, K, CR, LT, and VCD. The preschool period serves as a critical phase for myopia prevention and control.

To investigate the distribution of ocular biometric parameters and its association to refraction in university students in central China. Ocular biometric parameters including axial length (AL), central corneal thickness (CCT), keratometry power (K), anterior chamber depth (AQD) and lens thickness (LT) were measured by an optical biometry in a cohort of university students. Corneal radius of curvature (CR), lens position (LP), lens power (PBennett ), vitreous chamber depth (VCD) and AL to corneal radius ratio (AL/CR) were calculated. Cycloplegic refraction was measured using an autorefractor. A total of 7650 undergraduate students participated in this study, with a mean age of 20.0±1.4years. The following ocular biometric parameters were measured: AL (24.78±1.21mm), CCT (539.83±33.03μm), AQD (3.23±0.25mm), LT (3.47±0.18mm), CR (7.79±0.27mm), LP (4.97±0.23mm), VCD (17.55±1.15mm), PBennett (25.00±1.07 dioptres) and AL/CR (3.18±0.15). Male subjects were found to have longer AL, thicker CCT, flatter CR, thinner lens, deeper AQD and VCD than female ones. Myopic subjects were found to have longer AL, thinner CCT, steeper CR, thinner and posterior lens, deeper AQD and VCD, lower PBennett and larger AL/CR than emmetropes and hyperopes. Spherical equivalent (SE) showed a negative correlation with AL/CR (r=-0.914), AL (r=-0.755) and VCD (r=-0.751). This study provided a range of reference values for the main ocular biometric parameters in young adults and reported their distributions based on gender and refractive status. Our study indicates that SE has a strong correlation with AL/CR ratio, AL and VCD.

Macular pigment and ocular biometry

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.

Accurate measurement of axial length (AL), anterior chamber depth (ACD) and corneal curvature (CC) is essential for the calculation of IOL power according to different formulas. Assessing ACD is important to determine whether there is enough room for the PC-IOLs. It is evident that a shallow ACD and/or narrow angle may increase the risk of iris pigment chaffing, particularly when posterior chamber hyperopic PC-IOLs are implanted. Overestimation of ACD may result in corneal endothelial cell damage. Cyclopentolate is a synthetic antimuscarinic cycloplegic agent available in 0.5% and 1% solutions. It is widely accepted drug for patients of all ages providing excellent short-term cycloplegia. This study aims to compare the effect of cyclopentolate 1% on ocular biometric parameters – Anterior chamber depth (ACD), Lens thickness (LT) and Axial length (AL) before and after dilatation.In this observational study, 25 eyes of patients aged 45-75 years with significant cataract with nuclear sclerosis grading up to NO5NC5 C4 P4 (according to LOCS III) were included. The study was conducted for a duration of 3 months. Ocular biometric parameters ACD, LT and AL were measured using A-scan by immersion technique and compared before and after dilatation using 1% cyclopentolate and the data was analysed using paired T-test.Statistically significant difference (p value &amp;#60; 0.05) was observed in LT and ACD, while no significant difference was noted in AL post-cycloplegia.: Cycloplegia can significantly affect the ocular biometric parameters – deeper ACD and thinner LT. These changes in ocular biometric parameters should be considered in calculating IOL power to prevent refractive surprises after cataract surgery.

Assessment of the variability and correlation of biometric measurements in eyes with cataracts.

To evaluate the repeatability of a fully automated swept-source optical coherence tomography (SS-OCT) biometer to measure healthy crystalline lens decentration and tilt and their correlation with other biometric parameters. In this prospective study, 135 eyes of 135 patients were included. Ocular biometric parameters including crystalline decentration and tilt were measured three times with the Eyestar 900 SS-OCT (Haag-Streit AG). The repeatability was analyzed with the within-subject standard deviation (Sw), coefficient of variability, and coefficient of repeatability. Other biometric parameters such as keratometry (K1 flat and K2 steep), anterior chamber depth (ACD), lens thickness (LT), and axial length (AL) were also analyzed to explore possible relationships. For K1, K2, ACD, LT, and AL, Sw values were 0.07 diopters (D), 0.14 D, 0.01 mm, 0.02 mm, and 0.01 mm, respectively. For X and Y decentration and tilt, Sw values were 0.01, 0.02, and 0.39 mm, respectively. The correlation coefficient (r) between the crystalline lens tilt was low (r < -0.300) for all ocular biometric parameters, and was only associated with the AL (P < .001, r = -0.295). The r value between the decentration along the X and Y direction and the ocular biometric parameters was in all cases lower than 0.300. There was only a correlation between the decentration (Y direction) and K2 and ACD parameters (P < .001, P = .007, respectively). The linear regression parameters resulted in a slope value lower than -0.15 between any direction of the decentration and the other ocular biometric parameters. The Eyestar 900 provides repeatable measurements for crystalline lens decentration and tilt. AL was the only biometric parameter correlated with the crystalline lens tilt, and keratometry, ACD, and LT were correlated with the crystalline lens decentration along the Y direction. [J Refract Surg. 2025;41(2):e155-e163.].

Purpose:To find the effect of thalassemia major on ocular biometric parameters including axial length (AL), anterior chamber depth (ACD), vitreous chamber depth (VCD), and lens thickness (LT).Methods:A systematic search was carried out on PubMed, Cochrane, and Embase using a combination of keywords. The identified records undergone primary and secondary screening. The meta-analysis was done for comparing AL, ACD, VCD, and LT between thalassemia major cases and controls using pooled effect size, confidence intervals (CIs), quality assessment, and publication bias. This review was registered in the international prospective register of systematic reviews bearing code CRD42024542894.Results:This meta-analysis included 7 studies with a total sample of 1676 individuals (cases = 851, controls = 825). The cases were having reduced AL, ACD, and VCD while increased LT compared to controls. The estimated average effect size for AL = 1.07 (95%CI: 0.47–1.68, z = 3.471, P < 0.001), ACD = 0.81 (95%CI: 0.30–1.32, z = 3.109, P = 0.002), LT = 0.82 (95%CI: 0.45–1.19, z = 4.321, P < 0.001), and VCD = 1.08 (95%CI: 0.46–1.71, z = 3.392, P < 0.001).Conclusion:This study concludes that AL, ACD, and VCD were significantly less while LT was significantly greater in cases than in controls.

Ocular Biometric Parameters Associated With Intraocular Pressure Reduction After Cataract Surgery in Normal Eyes

Objective This study aimed to analyze the distribution of lens thickness (LT) and its associations in age-related cataract patients based on swept-source optical coherence tomography (SS-OCT). Methods This cross-sectional study included 59,726 Chinese age-related cataract patients. Only right-eye data were included in the study. Repeated measures of ocular parameters were performed using an IOL Master 700 device. The distributions of ocular biometric data including anterior chamber depth (ACD), LT, axial length (AL), central corneal thickness (CCT), white-to-white (WTW), and mean keratometry (MK) and their associations with age were assessed. The anterior segment (AS) was measured as the sum of CCT, ACD, and LT, while the vitreous chamber depth (VCD) was calculated as the difference between AL and AS. The values of LT : AL, AS : AL, and VCD : AL in different AL groups and their changes are the main outcome measures used to observe the proportion of the anterior and posterior segments of the eye. Results Biometric data were available for 59,726 individuals. The mean age was 68.81 years (range = 40–100); 40.62% were male and 59.38% were female. Mean anterior chamber depth (ACD) was 3.02 ± 0.44 mm, mean LT was 4.51 ± 0.44 mm, mean axial length (AL) was 23.89 ± 1.92 mm, mean central corneal thickness (CCT) was 0.53 ± 0.03 mm, mean white-to-white (WTW) was 11.64 ± 0.44 mm, and mean keratometry (MK) was 44.27 ± 1.65 diopter. Female patients had shorter AL, shallower ACD, smaller CCT and WTW, decreased LT, and steeper corneas (p < 0.005). ACD revealed the strongest negative correlation (p ≤ 0.001, r = –0.682) with LT. Age (p ≤ 0.001, r = 0.348) showed a moderate positive correlation, whereas MK (p ＜ 0.05, r = 0.011), CCT (p ≤ 0.001, r = 0.041) had a weak positive correlation and WTW (p ≤ 0.001, r = –0.034) had a weak negative correlation with LT. A nonlinear correlation was found between LT and AL. LT increased with age in both males and females. LT changed variably in eyes with AL less than 27 mm, LT decreased as AL increased, then LT gradually increased as AL increased in extremely long and extra-long eyes (p ≤ 0.001). LT : AL and AS : AL decreased as AL increased, VCD : AL gradually increased as AL increased in highly myopic eyes, and VCD : AL increased by about 0.01 for every 1 mm increase in AL. Conclusions Among Chinese age-related cataract patients, we found LT to have the strongest relation with ACD. The lens was thicker in elderly patients and women. The correlation between LT and AL is not a simple negative correlation; with the increase of age, LT decreases first and then increases. The proportion of VCD is constantly rising with the elongation of AL.

To evaluate the differences in ocular biometric parameters between eyes with primary angle closure (PAC) with and without visible ciliary body processes (CBP) (PAC+CBP and PAC-CBP) and normal open-angle controls. Cross-sectional study. Eyes with PAC and normal open-angle controls underwent detailed ocular examinations and gonioscopy to determine the visibility of the CBP. The following ocular biometric parameters were determined using A-scan ultrasound biometry: axial length (AL), anterior chamber depth (ACD), lens thickness (LT), and vitreous length (VL). The lens-axial length factor (LAF) and relative lens position (RLP) were also calculated. Continuous variables were assessed by analysis of variance with Bonferroni correction. Multiple linear regression analysis was performed to adjust for confounding factors. Area under the receiver operating characteristic curves were calculated to determine the diagnostic capability of biometric parameters. 84 PAC+CBP eyes, 57 PAC-CBP eyes, and 32 normal open angle control eyes were evaluated. The means of the ocular biometric values were significantly different among the three groups. AL, ACD, LT, VL, LAF, and RLP were also significantly different among the three groups in the multivariate regression analysis. AL, ACD, and VL were lower in the PAC+CBP group and LT, RLP, and LAF were greater in the PAC+CBP group than in the PAC-CBP and control groups. LAF ≥ 2.4 is the cutting point with the highest sensitivity and specificity to differentiate PAC+CBP from PAC-CBP. The ocular biometric parameters in the PAC+CBP group were more strongly associated with a crowded anterior segment than in the other groups. Visibility of CBP in PAC-affected eyes may serve as a surrogate for an anterior segment crowding mechanism and help to select the most appropriate treatment in individual cases.

PurposeTo evaluate the association of body stature with ocular biometrics and refraction in preschool children.MethodsA cross-sectional, school-based study was conducted in Shenzhen, China. Preschool children aged 3 to 6 from 10 randomly-selected kindergartens were recruited. Ocular biometric parameters, including axial length (AL), anterior chamber depth (ACD), vitreous chamber depth (VCD), corneal radius curvature (CR), axial length to corneal radius ratio (AL-to-CR ratio) and lens thickness (LT) were measured using non-contact partial-coherence laser interferometry. Cycloplegic refractions were obtained by a desktop autorefractor. Body height and weight were measured using standard procedures. The association between body stature and ocular biometrics were analyzed with univariable and multivariable regression model.ResultsA total of 373 preschoolers were included. AL, ACD, VCD, CR, and AL-to-CR ratio, were positively associated with height and weight (p < 0.05), whereas LT was negatively associated with height and weight (p < 0.01). No association was observed between stature and central cornea thickness and refraction. After adjusted for age and gender in a multivariable regression model, AL had positive associations with height (p < 0.01) and weight (p < 0.01). However, refraction had no significant association with stature parameters.ConclusionTaller and heavier preschoolers had eyes with longer AL, deeper vitreous chamber, and flatter cornea. The significant associations between body stature and ocular biometric parameters reveal the driving influence of body development on the growth of eyeballs in preschoolers.

Purpose:The mechanism of ocular growth eludes us and research on vitreous chamber depth (VCD) is lacking. The purpose of this study was to evaluate the role of VCD and its ratio to axial length (AL) in relation to ocular biometry.Methods:This retrospective study of patients planned for cataract surgery was performed at a tertiary center. Data regarding AL, anterior chamber depth (ACD), lens thickness (LT), and central corneal thickness (CCT) of 640 eyes was noted. Anterior segment (AS) was measured as sum of CCT, ACD, and LT, while VCD was calculated as the difference between AL and AS. Correlation of VCD and VCD: AL with ocular biometry was the primary outcome measure. Three groups were formed on the basis of AL and Pearson correlation coefficient (R) was applied.Results:Mean VCD was 15.38+/−1.14 mm. Mean VCD: AL was 0.66+/−0.02. VCD had a very strong relation with AL (R = 0.9, P < 0.001) only, whereas VCD: AL had a good-- strong relation with AL (R = 0.5, P < 0.001), AS (R = 0.7, P < 0.001), ACD (R = 0.3, P < 0.001), and LT (R = 0.5, P < 0.001). The relation of VCD: AL with AS was very strong across all groups (R ≤ - 0.8, P < 0.001 in all groups). 85% of eyes in group with AL <22 mm had VCD: AL <0.67, conversely 85% of eyes with AL >24.5 mm had VCD: AL >0.67.Conclusion:We found VCD to have the strongest relation with AL. VCD: AL was more consistent and showed a strong relation to ocular biometry across all ALs. This suggests the possible utility of the ratio VCD: AL while evaluating ocular growth, refractive status, and myopia-related complications.

BackgroundOcular biometric parameters can be influenced by race, ethnicity, and genetics; their differences across different populations can probably explain differences in refractive errors in these populations. The aim of this study is to determine the normal range of axial length, anterior chamber depth, lens thickness, and vitreous chamber depth in the population of Shahroud in the north of Iran.MethodsIn the first phase of Shahroud Eye Cohort Study, the 40–64 year old population were sampled cross-sectionally; 6311 were invited and 5190 (82.2%) participated in the study. Biometric examinations were done using the LENSTAR/BioGraph (WaveLight AG, Erlangen, Germany) after vision tests and before cycloplegic refraction tests. Any type of eye surgery, extensive pterygium, and lack of cooperation were used as exclusion criteria, and analyses were done with data from 4869 eyes.ResultsWe found a mean axial length of 23.14 mm (95% confidence interval [CI], 23.11-23.17), mean anterior chamber depth of 2.62 mm (95% CI, 2.60-2.63), mean lens thickness of 4.28 mm (95% CI, 4.27-4.29), and the mean vitreous chamber depth was 15.72 mm (95% CI, 15.70-15.75).Kolmogorov-Smirnov tests showed that the distribution of axial length, anterior chamber depth, lens thickness, and vitreous chamber depth significantly differed from normal; axial length and vitreous chamber depth demonstrated a leptokurtic distribution as well.Axial length, anterior chamber depth, and vitreous chamber depth significantly decreased with age, and lens thickness significantly increased with age (p < 0.001). All indices were significantly higher in men.ConclusionsThe distributions of axial length, vitreous chamber depth, and lens thickness are reported for the first time in an Iranian adult population. Compared to other studies, axial length was in the mid range, nonetheless, studying axial length components showed that the Iranian population had smaller anterior chamber depth and lens thickness. Age and gender were significantly associated with all indices assessed in this study.