Correlations between refractive error and biometric parameters in human eyes using the LenStar 900

Relationship between the main components of the crystalline lens and the anterior chamber depth after cataract formation

PURPOSE

To assess the relationship between anterior chamber depth (ACD) and lens thickness (LT), as well as its three main components (anterior and posterior cortex and nucleus thickness), in cataractous and non-cataractous eyes, depending on the axial length (AxL).

METHODS

Anterior and posterior cortex and nucleus thickness of the crystalline lens, ACD, and AxL were measured using optical low-coherence reflectometry in cataractous and non-cataractous eyes. They were also classified into hyperopia, emmetropia, myopia, and high myopia, depending on AxL; thus, eight subgroups were created. A minimum sample size of 44 eyes (of 44 patients) for each group was recruited. Linear models were fitted for the whole sample and each AxL subgroup to assess if there were differences in the relationships between the crystalline lens variables and ACD, including age as a covariate.

RESULTS

Three hundred seventy cataract patients (237 females, 133 males) and 250 non-cataract controls (180 females, 70 males), aged 70.5 ± 9.4 and 41.9 ± 15.5 years, respectively, were recruited. The mean AxL, ACD, and LT for the cataractous and non-cataractous eyes were 23.90 ± 2.05, 24.11 ± 2.11, 2.64 ± 0.45, and 2.91 ± 0.49, 4.51 ± 0.38, 3.93 ± 0.44 mm, respectively. The inverse relationship of LT, anterior and posterior cortex, and nucleus thickness with ACD was not significantly (p ≥ 0.26) different between cataractous and non-cataractous eyes. Further subclassification of the sample depending on AxL showed that the inverse relationship between the posterior cortex and ACD was no longer significant (p > 0.05) for any non-cataractous AxL group. LT, anterior and posterior cortex, and nucleus thickness was not significantly (p ≥ 0.43) different between cataractous and non-cataractous eyes for the whole sample, and all AxL groups after adjusting for age.

CONCLUSIONS

The presence of cataracts does not modify the inverse relationship of the LT, anterior and posterior cortex, and nucleus with ACD. And this relationship does not seem to depend importantly on AxL. Besides, the possible differences in LT, anterior and posterior cortex, and nucleus between cataractous and non-cataractous eyes may not be caused by lens opacification, but possibly by the progressive lens growth due to aging.

Lenstar LS900 vs EchoScan US-800: comparison between optical and ultrasound biometry with and without contact lenses and its relationship with other biometric parameters

BACKGROUND

Due to the increasing use of contact lenses (CL) and the interest in ocular and body size relationships, this study aimed to compare measurements from two biometers (contact ultrasonic EchoScan US-800 and non-contact optical Lenstar LS900) with and without CL and to explore the relationship between ocular and body biometric parameters.

DESIGN AND METHODS

This cross-sectional study measured ocular biometry using two biometers along with their body height and right foot length in 50 participants. Differences between biometry data from the two devices were compared and correlations between ocular and body biometric values were analyzed.

RESULTS

All parameters showed interbiometric differences (p ≤ 0.030), except crystalline lens thickness during CL wear (p = 0.159). Comparing measurements with and without CL, differences were observed in axial length (p < 0.001), vitreous length measured by optical biometer (p = 0.016), and anterior chamber depth by ultrasonic biometer (p < 0.016). Lens thickness remained unaffected (p ≥ 0.190). Body height and foot length were correlated with anterior chamber depth, vitreous length, and axial length (p ≤ 0.019, r ≥ 0.330). Most biometric parameters were correlated among them using both devices (p ≤ 0.037, r ≥ 0.296).

CONCLUSIONS

These biometers are not interchangeable and CL affects measurements. Body height and foot length correlate with ocular dimensions, and most ocular biometric values correlate positively.

Corneal Curvature, Anterior Chamber Depth, Lens Thickness, And Vitreous Chamber Depth: Their Intercorrelations With Refractive Error In Saudi Adults

Background:

Ocular biometrics, such as corneal curvature, axial length, anterior chamber depth, and lens thickness, play a significant role in the development of refractive error and are essential in many clinical and research applications.

Objective:

To determine means and ranges for corneal curvature, axial length, anterior chamber depth, lens thickness, vitreous chamber depth, and their intercorrelations with refractive error in Saudi adults.

Methods:

A total of 120 eyes of 60 hyperopic and 60 myopic subjects aged 19-26 years old were enrolled in this comparative cross-sectional study. Axial Length (AL), Anterior Chamber Depth (ACD), Lens Thickness (LT), and Vitreous Chamber Depth (VCD) were measured by the SONOMED ultrasound E-Z SCAN AB5500+, A-scan, with a contact technique. An ophthalmometer measured the refractive status objectively by auto-refraction and the corneal radius of curvature.

Results:

The findings showed that the myopic eyes had a deeper ACD(3.70±0.27mm) than hyperopic eyes (3.28±0.32mm), P=0.0001. However, the hyperopic eyes had a thicker LT (3.84±0.24mm) than the myopic eyes (3.81±0.19mm), P=0.640. The mean of the corneal radius of curvature for the myopic eyes was slightly more curved (7.87±0.23mm) than for the hyperopic eyes (7.95±0.27mm), P=0.602. The myopic eyes had a higher axial length/corneal radius AL/CR ratio (3.12±0.11) than hyperopic eyes (2.89±0.06), with P=0.0001. Myopic spherical equivalent (SPH) positively correlated with VCD and AL/CR ratio, P=0.0001. Vitreous chamber depth/Axial length ratio (VCD/AL) in the myopic eyes was higher (0.693±0.041) than in the hyperopic eyes (0.677±0.018), P=0.000. Hyperopic SPH was positively associated with the VCD/AL ratio, P=0.0001.

Conclusion:

Myopic eyes had a deeper VCD than hyperopic eyes; there was a strong positive correlation between VCD and myopic SPH. There was a strong positive correlation between the AL/CR ratio and myopic SPH and a VCD/AL ratio and the hyperopic SPH. Thus, the study suggests the possible utility of the AL/CR ratio while assessing the development of myopic refractive error and the VCD/AL ratio when evaluating hyperopic eyes and their associated complications.

Ocular biometry characteristics and its relationship with age, gender, spherical equivalent in Turkish children

Background

Studying ocular biometric parameters in different populations and determining the relationship with personal characteristics can provide valuable information about ocular growth and help provide a better understanding of refractive errors.

Aims

To describe distributions of ocular biometry and to evaluate its associations with age, gender, spheric equivalent in Turkish children.

Patients and Methods

In this prospective study 344 children aged 3-14 years were evaluated. Parameters studied included axial length (AL), anterior chamber depth (ACD), and mean corneal radius (CR) measured with optical biometry. Cycloplegic refraction values were obtained using autorefractometer. The change of biometric parameters according to age and gender were evaluated. The relationship between ocular biometry parameters with refraction and age was analyzed by linear regression.

Results

Mean spherical equivalent (SE), AL, ACD and AL/CR observed to be lowest in the preschooler group (P < 0.001). SE reduced with age, and a weak correlation observed between SE and age (r = -0.333). AL and ACD had moderate and weak positive correlations with age respectively (r = 0.511; r = 0.304). There were negative correlations between SE with AL, ACD and AL/CR (r = -0.826; r = -0.540; r = -0.886). The strongest correlation with SE among these parameters was identified for AL/CR. AL and ACD were higher in boys, while the CR was lower in girls (p < 0.001).

Conclusion

While AL in children in late schooler group is higher than European countries, it shows similar characteristics in early schooler group. In addition AL is lower in all age groups than Asian population sexcept preschooler group. With age AL increases, SE decreases and AL plays a key role in refractive development.

Impact of age, sex and refractive error on conjunctival and Tenon's capsule thickness dimensions by swept-source optical coherence tomography in a large population

PURPOSE

To evaluate conjunctival and Tenon's capsule thickness (CTT) in a large healthy population using swept-source optical coherence tomography (SS-OCT), investigating the impact of age, sex and refractive error.

METHODS

630 healthy participants underwent a complete ophthalmological examination. CTT was manually measured in the temporal and nasal quadrants at 0, 1, 2 and 3 mm from the scleral spur using SS-OCT (CTT0, CTT1, CTT2 and CTT3, respectively). These dimensions were then assessed for associations in a multivariate regression model with age, sex, refractive error and anterior scleral thickness (AST). The reproducibility of the CTT measurements was determined in 30 individuals.

RESULTS

CTT dimensions could be measured in 596 cases (94.6%); mean age was 42.6 ± 17.2 years (range 5-86). Mean CTT0 was 199.2 ± 33.8 and 192.9 ± 33.9 µm, mean CTT1 195.4 ± 38.0 µm and 199.9 ± 50.9 µm, mean CTT2 187.0 ± 38.4 and 194.8 ± 48.9 µm, and CTT3 180.5 ± 35.6 µm and 191.8 ± 43.7 µm, for the temporal and nasal quadrants, respectively. No difference in CTT was observed in the nasal versus temporal quadrant (p ≥ 0.106) except for the CTT0 and CTT3 (p = 0.001). Moderate correlation was observed between nasal and temporal CTT (R = 0.472, p < 0.001). In the multivariate model, no influence was observed by sex, refractive error and AST on CTT measurements (p ≥ 0.065). Negative association was observed between age and CTT (p < 0.005). The reproducibility was excellent (intraclass correlation coefficient ≥ 0.908).

CONCLUSIONS

SS-OCT allows for in vivo CTT evaluation. Our data document a wide range of measurements, showing negative association between CTT and age.

Effect of axial length and anterior chamber depth on the peripheral refraction profile

AIM

To evaluate the effect of axial length (AL) and anterior chamber depth (ACD) on peripheral refractive profile in myopic patients compared to emmetropic participants.

METHODS

This cross-sectional study was conducted in right eyes of 58 participants of whom 38 were emmetropic and 20 were myopic. Central and peripheral refraction were measured at 10°, 20°, and 30° eccentricities in nasal and temporal fields using an open-field autorefractor. The Lenstar LS900 was used to measure ACD and AL. The participants were divided into three groups of short (<22.5 mm), normal (22.5-24.5 mm), and long eye (>24.5 mm) according to AL and three groups of low ACD (<3.00 mm), normal ACD (3.00-3.60 mm), and high ACD (>3.60 mm) according to ACD.

RESULTS

The mean age of the participants was 22.26±3.09y (range 18-30y). The peripheral mean spherical refractive error showed a hypermetropic shift in myopic and emmetropic groups although this shift was more pronounced in the myopic group. The results showed significant changes in the spherical equivalent, J0, and J45 astigmatism in all gazes with an increase in eccentricity (P<0.001). The pattern of refractive error changes was more noticeable in long and short eyes versus normal AL eyes. Moreover, the pattern of peripheral refractive changes was much more prominent in the high ACD group versus the normal ACD group and in the normal ACD group versus the low ACD group.

CONCLUSION

Peripheral refraction changes are greater in participants with AL values outside the normal range and deeper ACD values compared to participants with normal AL and ACD.

The Iris Thickness in a Healthy Saudi Population

Purpose

Iris thickness (IT), a known risk factor for angle closure glaucoma, has not been evaluated in the normal Saudi population.

Methods

Quantitative information on IT was evaluated in healthy Saudi eyes using anterior segment optical coherence tomography (ASOCT). IT and iris volume was measured with the room ‘light on’ (LON) and ‘light off’ (LOFF) using Image J software. IT in the nasal and temporal iris was measured at 500 µm (IT500) and 750 µm (IT750) from the scleral spur (SS). Differences in IT measurements by age, gender and type of refractive error were evaluated.

Results

We included 100 eyes of 50 healthy adult Saudis without ocular disease other than refractive errors. The mean age of 56 males and 44 females in the study group was 41.7 ± 14.5 years. The refractive status was as follows: emmetropia (35 eyes), mild/moderate myopia (33 eyes), high myopia (17 eyes) and hyperopia (15 eyes). The IT750 with LON was significantly more than IT500 both nasally (P = 0.03) and temporally (P < 0.001). The difference in IT750 and IT500 with LOFF was significantly more nasally (P = 0.03), temporally (P = 0.02), and with LON nasally (P = 0.005). IT was thicker in males when compared to females and variation of IT by refractive error was significant but not by age. The mean pupil diameter and anterior chamber depth decreased with age (P < 0.001). Anterior chamber width was not affected by age or illumination.

Conclusion

The baseline iris thickness in the Saudi eyes could be used to compare iris thickness in eyes with angle closure glaucoma among the Arab population.

Preoperative biometric measurements with anterior segment optical coherence tomography and prediction of postoperative intraocular lens position

The purpose of this study is to evaluate the biometric parameters of crystalline lens components and to find effective factors for predicting postoperative intraocular lens (IOL) position. This retrospective study included 97 eyes from 97 patients with a mean age of 63.00 ± 12.38 (SD) years. The biometric measurements were performed by means of a 3-dimensional optical coherence tomography (3D-OCT) device. Specifically, anterior chamber depth (ACD), aqueous depth (AD), lens thickness (LT), lens meridian parameter (LMP), white-to-white diameters (WTW), anterior segment length (ASL), the anterior part of lens (aLT), and the posterior part of lens (pLT) were measured. Additionally, axial length (AL) and corneal radius (CR) were measured by the partial coherence interferometry. Ninety-seven eyes were divided into thin lens group (LT < 4.5 mm) and thick lens group (LT ≥ 4.5 mm). The differences between the above two groups were also analyzed. Postoperative IOL position was measured by 3D-OCT at 3 months postoperatively and regression formulas for predicting postoperative IOL position were developed by various combinations of preoperative factors. As lens thickened, ACD and AD became shallow (all P < .001). AD, ACD, ASL, aLT, and pLT showed statistically significant differences between two subgroups classified on the basis of LT (all P < .001). Meanwhile, the value obtained by subtracting aLT from pLT did not show any association with the other biometric measurements. The combination of ACD, aLT, pLT, AL, CR, and WTW showed the highest correlation with postoperative IOL position (R = 0.536, P < .001). In conclusion, pLT-aLT was an independent factor not affected by any other variables and did not show significant difference between thin lens group and thick lens group. The subdivision of the lens structure using 3D-OCT helps to predict postoperative IOL position.

Correlations between ocular biometrics and refractive error: A systematic review and meta-analysis

The understanding of correlations between different biometric parameters is essential for personalized eye care in the field of cataract and refractive surgery. This systematic review offers a clear overview of the previous literature assessing these correlations including a meta-analysis. The review is focused on the following five correlations: (1) axial length and refractive error; (2) anterior chamber depth and refractive error; (3) axial length and anterior chamber depth; (4) corneal power and refractive error; (5) corneal power and axial length. An expected strong correlation between axial length and refractive error was found. Correlations including corneal power were weak and might be clinically insignificant.

Correlation analysis and multiple regression formulas of refractive errors and ocular components

The multiple regression formulas and correlation of ocular components with refractive errors are presented by Gaussian optics. The refractive error changing rate for the cornea and lens power, the axial length, anterior chamber depth (ACD) and vitreous chamber depth (VCD) are calculated, including nonlinear terms for more accurate rate functions than the linear theory. Our theory, consistent with the empirical data, shows that the Pearson correlation coefficients for spherical equivalent (SE) and ocular components are highest for SE with axial length, ACD and VCD and weakest for corneal power, lens power and lens thickness. Moreover, our regression formulas show the asymmetric feature of the correlation that the axial length, ACD and VCD are more strongly correlated (with higher negative regression constants) with refractive errors in eyes with hyperopia than in eyes with myopia, particularly for severe hyperopia.

Comparison of anterior segment parameters and axial lengths of myopic, emmetropic, and hyperopic children

PURPOSE

To compare the anterior segment parameters of myopic, hyperopic, and emmetropic children by using optical biometry.

METHODS

This prospective cross-sectional study included 150 eyes of 150 children between 6 and 16 years old. The eyes were divided into three groups according to their spherical equivalent (SE) refractive error values as myopic [between - 1.0 and - 6.0 diopter (D)], emmetropic (between + 0.50 and - 0.50 D), and hyperopic (between + 1. 0 and + 3.0 D). Axial length (AL), central corneal thickness, anterior chamber depth (ACD), lens thickness (LT), and mean keratometry (K mean) measurements were obtained by an optical biometry (LenStar LS 900, Haag Streit Diagnostics) were compared between the groups.

RESULTS

There were no statistically significant differences regarding the ages and genders of the participants between the groups (p > 0.05). The mean SE refractive error values were - 2.20 ± 0.71 D in myopic, - 0.08 ± 0.49 D in emmetropic, and + 2.06 ± 0.53 D in hyperopic eyes. The mean AL values were 24.50 ± 0.69, 23.41 ± 0.61, and 22.33 ± 0.61 mm, respectively, in myopic, emmetropic, and hyperopic eyes (p < 0.001). The mean ACD values were 3.94 ± 0.22, 3.78 ± 0.23, and 3.45 ± 0.20 mm, respectively, in myopic, emmetropic, and hyperopic eyes (p < 0.001). The mean LT values were 3.56 ± 0.20, 3.43 ± 0.17, and 3.31 ± 0.12 mm, respectively, in myopic, emmetropic, and hyperopic eyes (p < 0.001). There were no significant differences in the other parameters between the groups.

CONCLUSIONS

Refractive errors are the main factors those affect anterior segment parameters and AL in children and the most severely affected parameters were found to be the AL, ACD, and LT values.

Axial length, anterior chamber depth and lens thickness: Their intercorrelations in black South Africans

Purpose: To determine means and ranges for axial length, anterior chamber depth, lens thickness values and their intercorrelations in an African population.Methods: Six hundred participants (N = 600) were selected through stratified random cluster sampling from geographically contiguous areas of Durban, South Africa. All participants underwent height measurements and standard vision testing. Repeated measures of axial length, anterior chamber depth and lens thickness were taken with the Nidek US-500 Echoscan.Results: Participants’ ages ranged from 10 to 66 years with a mean age of 28.15 ± 13.09 years (95% confidence interval, 27.09–29.19). Of all the subjects, 295 (49.17%) were females and 305 (50.83%) were males. Axial length ranged from 20.42 mm to 27.28 mm with a mean of 23.05 mm ± 0.98 mm (95% confidence interval, 22.97–23.14), anterior chamber depth ranged from 2.38 mm to 4.13 mm with a mean of 3.21 mm ± 0.37 mm (95% confidence interval, 3.18–3.24) and crystalline lens thicknesses ranged from 2.24 mm to 4.66 mm with a mean of 3.69 mm ± 0.25 mm (95% confidence interval, 3.66–3.71). All three biometric indices were significantly higher in men than in women (all p-values < 0.05). A multivariate linear regression model indicated that axial length and anterior chamber depth decreased with age, while lens thickness increased with age. All biometric indices directly correlated with the male gender and height (all p-values < 0.001). Pearson correlation coefficient tests showed that axial length was significantly positively correlated with anterior chamber (r = 0.66, p < 0.001) and negatively correlated with lens thickness (r = -0.52, p < 0.001). A significant negative correlation was found between lens thickness and anterior chamber depth values (r = -0.68, p < 0.001).Conclusion: Normative values for axial length, anterior chamber depth and lens thickness are determined for the first time in a black South African sample, aged 10–66 years. Age, gender and height were associated with biometric indices. While there was a positive correlation between axial length and anterior chamber depth, there was a negative correlation between lens thickness and both axial length and anterior chamber depth. These biometric data and their intercorrelations may provide some insights into the pathophysiological mechanisms of angle-closure glaucoma in this population.

Evaluation of the repeatability of a swept-source ocular biometer for measuring ocular biometric parameters

PURPOSE

The purpose was to evaluate the repeatability of a new swept-source optical biometer for measuring ocular biometric parameters.

METHODS

Thirty subjects with healthy and phakic eyes were included in this study, and only one eye per participant was analysed. Each eye was measured five times with the IOLMaster 700 swept-source optical biometer (Carl Zeiss Meditec, Jena, Germany). Axial length (AL), anterior chamber depth (ACD), central corneal thickness (CCT), lens thickness (LT), white-to-white (WTW), and K1 and K2 keratometric readings were evaluated. The repeatability of swept-source biometry was evaluated on the basis of five measurements captured for each patient.

RESULTS

The repeatability limits for the axial measurements AL, ACD, CCT, and LT were 0.03, 0.07, 0.004, and 0.11 mm, respectively. For the WTW distance and both keratometry readings, the repeatability limits were 0.20, 0.06, and 0.05 mm, respectively. The AL resulted in the lowest coefficient of variation, and the LT had the highest one. The spherical equivalent showed statistically significant negative correlations with the AL and ACD.

CONCLUSION

Swept-source optical biometry showed high repeatability performance for all biometric parameters in healthy eyes, where the correlation between the spherical equivalent and AL showed the strongest value.

Determinants of anterior chamber depth in a large Caucasian population and agreement between intra-ocular lens Master and Pentacam measurements of this variable

PURPOSE

To establish the main determinants of anterior chamber depth (ACD) in Caucasian subjects and examine agreement between IOL Master(®) (Carl Zeiss, Meditec) and Pentacam(®) (Oculus Inc.) ACD measurements.

METHODS

In a cross-sectional study, 1006 right eyes of 1006 healthy subjects were subjected to a general ophthalmologic examination using the Pentacam(®) , IOLMaster(®) and OCT RTVue(®) (Optovue Inc.). The variables recorded were age, sex, intra-ocular pressure, spherical refractive error, axial length (AL), central corneal thickness, corneal diameter, iris thickness, and anterior chamber depth, volume and angle (ACA). The effects of these variables on ACD were analysed by multivariate linear regression.

RESULTS

Mean age was 49.1 years (range 18-84); 61% were women. In 98.3% of the eyes, ACD could be measured using the IOL Master and in 98% the Pentacam was used to give mean depths of 3.30 ± 0.42 mm and 3.35 ± 0.43 mm, respectively, for the two instruments. Agreement between these devices was high. In men, ACD was 0.13 mm on average deeper than in women (p < 0.001). ACD was correlated with ACA, AL, corneal diameter, spherical refractive error and age (p < 0.001). Five variables - age, sex, spherical error, corneal diameter and ACA - were able to explain 74.1% of the variation produced in ACD (R(2) = 0.741; p < 0.001), among which age emerged as the main determinant (partial R(2) = 0.279; p < 0.001).

CONCLUSIONS

Age, sex, spherical error, corneal diameter and ACA correlate highly with ACD and together serve to explain much of its variation. When used to measure ACD, the IOLMaster and Pentacam show excellent agreement.

Association between Refractive Errors and Ocular Biometry in Iranian Adults

Purpose:

To investigate the association between ocular biometrics such as axial length (AL), anterior chamber depth (ACD), lens thickness (LT), vitreous chamber depth (VCD) and corneal power (CP) with different refractive errors.

Methods:

In a cross-sectional study on the 40 to 64-year-old population of Shahroud, random cluster sampling was performed. Ocular biometrics were measured using the Allegro Biograph (WaveLight AG, Erlangen, Germany) for all participants. Refractive errors were determined using cycloplegic refraction.

Results:

In the first model, the strongest correlations were found between spherical equivalent with axial length and corneal power. Spherical equivalent was strongly correlated with axial length in high myopic and high hyperopic cases, and with corneal power in high hyperopic cases; 69.5% of variability in spherical equivalent was attributed to changes in these variables. In the second model, the correlations between vitreous chamber depth and corneal power with spherical equivalent were stronger in myopes than hyperopes, while the correlations between lens thickness and anterior chamber depth with spherical equivalent were stronger in hyperopic cases than myopic ones. In the third model, anterior chamber depth + lens thickness correlated with spherical equivalent only in moderate and severe cases of hyperopia, and this index was not correlated with spherical equivalent in moderate to severe myopia.

Conclusion:

In individuals aged 40-64 years, corneal power and axial length make the greatest contribution to spherical equivalent in high hyperopia and high myopia. Anterior segment biometric components have a more important role in hyperopia than myopia.

Baseline peripheral refractive error and changes in axial refraction during one year in a young adult population

PURPOSE

To determine whether the initial characteristics of individual patterns of peripheral refraction relate to subsequent changes in refraction over a one-year period.

METHODS

54 myopic and emmetropic subjects (mean age: 24.9±5.1 years; median 24 years) with normal vision were recruited and underwent conventional non-cycloplegic subjective refraction. Peripheral refraction was also measured at 5° intervals over the central 60° of horizontal visual field, together with axial length. After one year, measurements of subjective refraction and axial length were repeated on the 43 subjects who were still available for examination.

RESULTS

In agreement with earlier studies, higher myopes tended to show greater relative peripheral hyperopia. There was, however, considerable inter-subject variation in the pattern of relative peripheral refractive error (RPRE) at any level of axial refraction. Across the group, mean one-year changes in axial refraction and axial length did not differ significantly from zero. There was no correlation between changes in these parameters for individual subjects and any characteristic of their RPRE.

CONCLUSION

No evidence was found to support the hypothesis that the pattern of RPRE is predictive of subsequent refractive change in this age group.

Axial Length Measurement Failure Rates with the IOLMaster and Lenstar LS 900 in Eyes with Cataract

PURPOSE

To evaluate axial length (AL) measurement failure rate with the IOLMaster (Carl Zeiss AG, Germany) and Lenstar LS 900 (Haag-Streit AG, Switzerland) in eyes with cataract.

METHODS

Two hundred and ninety-six eyes of 170 patients with cataract were enrolled. Cataract type and severity were graded using the Lens Opacities Classification System III (LOCS III) and AL measurements were attempted with IOLMaster (version 5.4) and Lenstar LS 900 (version 1.1). Chi-squared analysis was used to assess if the difference in AL measurement acquisition rate was statistically significant between the two devices. The association of the different cataract types and severity with the AL measurement acquisition rate was evaluated with logistic regression analysis.

RESULTS

AL measurements were obtained in 184 eyes (62.16%) using the IOLMaster and 191 eyes (64.53%) using the Lenstar, which corresponds to a failure rate of 37.84% and 35.47% respectively. Chi-square analysis indicated no significant difference between the Lenstar and IOLMaster for AL measurement failure rate (x2 = 0.356, P = 0.550). Logistic regression analysis indicated no association between acquisition rates and cortical or nuclear cataracts with either device. There was a statistically significant association between acquisition rates and increasing severity of posterior subcapsular cataracts with the IOLMaster (β = -1.491, P<0.001) and Lenstar LS 900 (β = -1.507, P<0.001).

CONCLUSION

The IOLMaster and Lenstar LS 900 have similar AL measurement failure rates (35-38%) for Chinese public hospital cataract patients. Increasing severity of posterior subcapsular cataracts was problematic for both devices.

Binocular saccades in myopes and emmetropes

PURPOSE

To compare saccadic eye movements in groups of myopes and emmetropes, as eye movements could have an influence on refractive error development. Individual saccadic eye movement parameters were also compared with subjective refraction and axial length data.

METHODS

Horizontal eye movements of 28 participants (14 myopes and 14 emmetropes; mean age [SD], 27.0 [4.7] years) were recorded using a head-mounted eye tracker. To reduce the influence of head movements, a chin rest was used. Two fixation stimuli lying symmetrically at ±10 degrees on either side of the median line were presented on a computer monitor and were alternately displayed for durations of 2 seconds each. The participants alternated their fixation between the target positions immediately after they became aware that the target had changed. Only right eye data were considered for analysis.

RESULTS

Durations, amplitudes, and peak velocities of the main saccades and the numbers of overshoots, undershoots, and exact fixations were analyzed. For all analyzed parameters, no significant differences were found between myopes and emmetropes. When analyzing the whole study population or the emmetropic group alone, none of the saccadic eye movement parameters were correlated with axial length or refractive error. In myopes, only the peak velocity showed a weak correlation with refractive error and axial length, but this failed to reach statistical significance when allowance was made for multiple testing.

CONCLUSIONS

Because saccadic eye movements seem to be similar in myopes and emmetropes, there is no evidence that saccadic eye movements are involved in myopia development.

The effect of pupil dilation on biometric parameters of the Lenstar 900

PURPOSE

To evaluate the effect of pupil dilation on the biometric parameters of the Lenstar LS 900 (Haag Streit AG, Koeniz, Switzerland).

METHODS

In this cross-sectional study of 33 eyes with cataracts, axial length (AL), anterior chamber depth, intraocular lens (IOL) power, keratometry, and pupil diameter measurements were performed using Lenstar biometry before and after pupil dilatation. Intraobserver repeatability was assessed by taking 2 consecutive recordings of biometric parameters using Lenstar biometry in the undilated pupils of 30 eyes with cataracts.

RESULTS

The mean difference in AL measurements from intraobserver readings was -0.001 ± 0.01 mm. The study group showed a statistically significant change in the first keratometry reading and anterior chamber depth values (P < 0.05); however, the mean difference in AL and IOL power was statistically insignificant between the undilated and dilated pupil Lenstar biometry readings. Three cases in the study group (9.1%) and 1 case in the control group (3.3%) demonstrated changes in IOL power >0.50 diopter.

CONCLUSIONS

Dilated and undilated pupil size did not affect the measurement of IOL using the Lenstar biometry.

Analysis of age-dependence of the anterior and posterior cornea with scheimpflug imaging

PURPOSE

To assess keratometric and higher-order aberrations of the anterior and posterior cornea and their age-related changes.

METHODS

This study investigated one healthy eye of 227 patients (mean age: 55.15 ± 21.2 years; range: 16 to 90 years; 135 right eyes, 92 left eyes). Images were captured from each eye with Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) using automatic mode. Keratometric, astigmatism data, and corneal higher-order aberrations were analyzed.

RESULTS

With respect to laterality, no deviance was found in any of the parameters (P > .05). Mean refractive error was 0.52 ± 0.23 diopters. The level of astigmatism decreased significantly with advancing age for both the anterior and posterior corneal surfaces (P < .05). The overall root mean square of the higher-order aberration increased continuously with age (r = 0.517; P < .01), which can be explained by the combined effect of the increased in both the anterior and posterior corneal root mean square higher-order aberrations. Of the higher-order aberrations, the constant increase of the primary and secondary spherical aberration with aging (P < .01) is caused by the spherical aberration growth of the anterior surface. Apart from these, only the vertical coma aberration of the posterior surface and the vertical trefoil aberrations of both the anterior and posterior surfaces showed a significantly positive correlation with aging (P < .05).

CONCLUSIONS

Corneal astigmatism showed a significant decrease with aging. Of the higher-order aberrations, primary and secondary spherical aberrations, vertical coma, and vertical trefoil significantly increase with age, whereas other higher-order aberrations show no correlation with aging.

Correlation Between Axial Length and Anterior Chamber Depth in Normal Eyes, Long Eyes, and Extremely Long Eyes

PURPOSE

The objective of this study was to investigate the correlation between axial length (AL) and anterior chamber depth (ACD) in normal to long eyes and in extremely long eyes.

DESIGN

This was an observational cross-sectional study in a single-center, private hospital.

METHODS

Axial length and ACD data were retrieved from the intraocular lens (IOL) Master database of patients who presented for IOL or phakic lens implantation. Only left eyes were included. The correlation between AL and ACD was tested with Pearson correlation coefficient in all eyes, normal to long eyes (AL < 27.5 mm), and extremely long eyes (AL ≥ 27.5 mm). P < 0.01 was statistically significant.

RESULTS

The cohort was composed of 1184 eyes of 1184 Chinese patients. The mean age was 65.8 ± 13.3 years (range, 19-98 years). The mean AL and ACD were 24.73 ± 2.48 mm (range, 20.51-36.20 mm) and 3.09 ± 0.44 mm (range, 1.95-4.68 mm), respectively. Pearson correlation coefficients in all eyes, normal to long eyes (1026 eyes, 87%), and extremely long eyes (158 eyes, 13%) were 0.56 (P < 0.001), 0.59 (P < 0.001), and -0.15 (P = 0.67), respectively.

CONCLUSIONS

There was a statistically significant positive correlation between AL and ACD in normal and long eyes but not in extremely long eyes. No correlation between AL and ACD in extremely long eyes requires newer-generation IOL formulas (ACD included) to increase the accuracy of IOL implantation.