Prediction of accommodative optical response in prepresbyopic subjects using ultrasound biomicroscopy

Introducing Dynamic Stimulation Aberrometry: Binocular Objective Accommodation versus Subjective Measures

Purpose

The objective measurement of binocular accommodation remains a challenge. The dynamic stimulation aberrometry (DSA) system uses wavefront measurements to dynamically assess accommodation. In this study, we sought to introduce this method in a large number of patients of varying age and compared it with the subjective push-up method as well as the historical results of Duane.

Design

This study is an evaluation of diagnostic technology.

Subjects

Ninety-one patients aged 20 to 67 years (70 healthy, phakic eyes and 21 myopic eyes after phakic intraocular lens implantation) were enrolled at a tertiary eye hospital.

Methods

All patients underwent DSA measurements; the accommodative amplitude of 13 patients chosen at random was additionally examined using the subjective push-up method introduced by Duane. DSA measurements were also compared with Duane's historical results.

Main Outcome Measures

Accommodative amplitude, dynamic parameters of accommodation, and near pupil motility.

Results

Dynamic stimulation aberrometry allowed objective measurement of binocular accommodation, which decreased with age (e.g., 30-39 years vs. > 50 years; 3.8 ± 0.9 diopters [D] and 0.1 ± 0.4 D, respectively). Dynamic parameters, such as time delay of the commencement of accommodation after near target presentation, increased with age (0.26 ± 0.14 seconds for 20-30 years vs. 0.43 ± 0.15 seconds for 40-50 years, P = 0.0002). The objective accommodative amplitude was significantly smaller than Duane's historic results (P = 0.001) as well as the subjective push-up method. Dynamic stimulation aberrometry records pupil motility dynamically in parallel to wavefront measurements. Maximum pupil motility during accommodation significantly decreased with age (P = 0.0002). Maximum pupillary speed did not correlate significantly with age.

Conclusions

Dynamic stimulation aberrometry allows objective, dynamic, binocular measurement of accommodation and pupil motility with high time resolution in subjects with accommodative amplitudes up to 7 D. This article introduces the method in a large study population and may serve as a control for further studies.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Repeatability of the Accommodative Response Measured by the Grand Seiko Autorefractor in Children With and Without Amblyopia and Adults

PURPOSE

To assess test-retest repeatability of the accommodative response (AR) in children with and without amblyopia and adults using the Grand Seiko autorefractor.

DESIGN

Prospective reliability assessment.

METHODS

Test-retest of accommodation was obtained while participants viewed 20/150 sized letters at 33 cm using the Grand Seiko autorefractor in children 5 to <11 years with amblyopia (n=24) and without amblyopia (n=36), and adults 18 to <35 years (n=34). Bland-Altman 95% limits of agreement (LOA) and intraclass correlation coefficients (ICCs) were used to assess repeatability and reliability. The AR between the fellow and amblyopic eyes of children with amblyopia and eye 1 and eye 2 of the visually normal participants was assessed using group comparisons.

RESULTS

The 95% LOA of the AR was greatest in the amblyopic eyes (-1.25 diopters [D], 1.62 D) of children with amblyopia. The 95% LOA were similar between the fellow eyes (-0.88 D, 0.74 D) of children with amblyopia and both eyes of the children without amblyopia (eye 1: -0.68 D, 0.71 D; eye 2: -0.59 D, 0.70 D) and the adults (eye 1: 95% LOA = -0.49 D, 0.45 D; eye 2: LOA = -0.66 D, 0.67 D). ICCs revealed the Grand Seiko autorefractor as a reliable instrument for measuring AR.

CONCLUSIONS

The Grand Seiko autorefractor was more repeatable and reliable when measuring the AR in children and adults without amblyopia than in the amblyopic eye in children with amblyopia. It is recommended that multiple measures of the AR be obtained in amblyopic eyes to improve the precision of measures.

Biometric assessment of pseudophakic subjects during objective accommodative stimulation: a prospective observational study

Clinical relevance: Ultrasound biomicroscopy is an objective method for assessing changes in anterior segment biometry. There is a paucity of data on the reliability of this method. A reliable method for assessing anterior segment changes during physiologically driven accommodation can be a useful tool for clinicians, researchers, and industry.Background: To assess the test-retest reliability of ultrasound biomicroscopy for measurements of change in anterior chamber depth during a distance to near fixation task in pseudophakic subjects.Methods: Subjects were adults with monofocal intraocular lenses implanted in both eyes who completed a 6-month post-operative period and had monocular uncorrected distance visual acuity of 6/15 (0.4 logMAR) or better. The change in anterior chamber depth during a distance to near fixation task was measured with a 35-MHz VuMAX HD ultrasound biomicroscopy device (Sonomed Escalon, New Hyde Park, NY) during two separate visits. An asymmetrical vergence paradigm allowed evaluation of anterior segment biometry at 22-µm axial resolution in one eye, while the fellow eye fixated on the target. To assess the test-retest reliability, 2-sided 95% CI from a paired t test was calculated for the difference in anterior chamber depth change from distance to near between visits.Results: The mean (standard deviation) near-focused anterior chamber depth measured by ultrasound biomicroscopy was 4.331 (0.237) and 4.333 (0.241) mm at visits 1 and 2, respectively. In response to a change in fixation from distance (4 m) to near (40 cm), the mean anterior chamber depth change was -0.012 (0.038) and 0.003 (0.039) mm at visits 1 and 2, respectively. Analysis of the difference in the change in anterior chamber depth between visits was -0.015 mm (95% CI, -0.035 to 0.003).Conclusion: Ultrasound biomicroscopy is a repeatable, objective method for assessing change in anterior segment biometry during physiological changes in fixation from distance to near.

A systematic review of ultrasound biomicroscopy use in pediatric ophthalmology

Ultrasound biomicroscopy (UBM) is the only available option for noninvasive, high-resolution imaging of the intricate iridociliary complex, and for anterior segment imaging with corneal haze or opacity. While these unique features render UBM essential for specific types of trauma, congenital anomalies, and anterior segment tumors, UBM imaging has found clinical utility in a broad spectrum of diseases for structural assessments not limited to the anterior intraocular anatomy, but also for eyelid and orbit anatomy. This imaging tool has a very specific niche in the pediatric population where anterior segment disease can be accompanied by corneal opacity or clouding, and anomalies posterior to the iris may be present. Pediatric patients present additional diagnostic challenges. They are often unable to offer detailed histories or fully cooperate with examination, thus amplifying the need for high-resolution imaging. This purpose of this systematic review is to identify and synthesize the body of literature involving use of UBM to describe, evaluate, diagnose, or optimize treatment of pediatric ocular disease. The collated peer-reviewed research details the utility of this imaging modality, clarifies the structures and diseases most relevant for this tool, and describes quantitative and qualitative features of UBM imaging among pediatric subjects. This summary will include information about the specific applications available to enhance clinical care for pediatric eye disease.

Comparison of radius of anterior lens surface curvature measurements in vivo using the anterior segment optical coherence tomography and Scheimpflug imaging

Background

To assess the radius of anterior lens surface curvature (RAL) measurements with anterior segment optical coherence tomography (AS-OCT) in comparison with Scheimpflug imaging.

Methods

This prospective, cross-sectional study was carried out at Zhongshan Ophthalmic Center, Guangzhou, China. We enrolled 59 eyes, including 30 eyes from 30 cataractous volunteers (59 to 87 years) and 29 eyes from 29 young participants (19 to 49 years). After mydriasis, the RAL was measured automatically by the built-in software in the AS-OCT (CASIA 2). The Scheimpflug images were measured with the build-in caliper tool of the Scheimpflug camera (Pentacam), and RAL were further calculated with the principle of best-fitted circle. Intraobserver and interobserver reproducibility of RAL measurement using Scheimpflug camera were evaluated with limit of agreement (LoA) and intraclass correlation coefficient (ICC). Consistency between RAL measurement of Scheimpflug camera and AS-OCT were assessed with LoA, correlation analysis and linear regression.

Results

For all subjects, intraobserver (LoA: −0.25 to 0.23 mm, ICC: 0.996) and interobserver reproducibility (LoA: −0.85 to 0.92 mm, ICC: 0.947) of RAL were good using Scheimpflug imaging. Both AS-OCT and Scheimpflug imaging found that the age-related cataract participants had smaller RAL (P=0.010, P=0.001 respectively). LoA of RAL measurement between AS-OCT and Scheimpflug imaging was −3.83 to −0.79 mm, and the Pearson correlation efficient was 0.909 (P<0.001). The RAL values measured by AS-OCT were significantly greater than that by Scheimpflug camera with a mean difference of 2.31 mm for all participants (P<0.001). The RAL measurement could be converted using the equation: Y_{CASIA 2} =1.155 × X_Pentacam + 1.060.

Conclusions

Both Scheimpflug camera system with internal caliper tool and the AS-OCT are fast and non-contact tools that could measure RAL successfully. The two measurement results are highly correlated and interchangeable through linear regression equation.

Image registration of the human accommodating eye demonstrates equivalent increases in lens equatorial radius and central thickness

AIM

To compare the results of in vivo human high resolution image registration studies of the eye during accommodation to the predictions of mathematical and finite element models of accommodation.

METHODS

Data from published high quality image registration studies of pilocarpine induced accommodative changes of equatorial lens radius (ELR) and central lens thickness (CLT) were statistically analyzed.

RESULTS

The mean changes in ELR and CLT were 6.76 µm/diopter and 6.51 µm/diopter, respectively. The linear regressions, reflecting the association between ELR and accommodative amplitude (AAELR) was: slope=6.58 µm/diopter, r2 =0.98, P<0.0001 and between CLT and AACLT was: slope=6.75 µm/diopter, r2 =0.83, P<0.001. On the basis of these relationships, the CLT slope and the AAELR were used to predict the measured change in ELR (ELRpredicted). There was no statistical difference between ELRpredicted and the measured ELR as demonstrated by a Student's paired t-test: P=0.96 and linear regression analysis: slope=0.97, r2 =0.98, P<0.00001.

CONCLUSION

Image registration with invariant positional references demonstrates that ELR and CLT equivalently minimally increase ∼7.0 µm/diopter during accommodation. The small equivalent increases in ELR and CLT are associated with a large accommodative amplitude. These findings are consistent with the predictions of mathematical and finite element models that specified the stiffness of the lens nucleus is the same or greater than the lens cortex and that accommodation involves a small force (<5 g).

Comparison of 25 MHz and 50 MHz ultrasound biomicroscopy for imaging of the lens and its related diseases

AIM

To compare the results of 25 MHz and 50 MHz ultrasound biomicroscopy (UBM) regarding the image characteristics of the lens and its related diseases and to discuss the application value of 25 MHz UBM in ophthalmology.

METHODS

A total of 302 patients (455 eyes) were included in this study from November 2014 to May 2015. Patient ages ranged from 5 to 89y (mean±SD: 61.0±17.7y). Different cross-sectional images of the lens were collected to compare and analyze the image characteristics and anterior segment parameters using 25 MHz and 50 MHz UBM in axial and longitudinal scanning modes, respectively. SPSS 19.0 for Windows, paired t-tests and B&A plot analysis were used for data analysis, and a value of P<0.05 was considered statistically significant.

RESULTS

The 25 MHz UBM images displayed the lens shape more clearly than 50 MHz UBM images. Particularly for cataracts, the whole opacity of the lens was shown by 25 MHz UBM, but 50 MHz UBM only showed part of the lens. The means of the anterior segment parameters obtained using 25 MHz and 50 MHz UBM were as follows: central corneal thickness: 0.55±0.03 and 0.51±0.04 mm, respectively; central anterior chamber depth: 2.48±0.54 and 2.56±0.56 mm, respectively; and central lens thickness: 4.26±0.62 and 4.15±0.56 mm, respectively. A statistically significant difference was found between the results obtained with 25 MHz UBM and those obtained with 50 MHz UBM. The two devices had a good agreement in measuring the anterior segment parameters.

CONCLUSION

The 25 MHz UBM had an obvious advantage in showing the lens shape. It can provide reliable imaging of the lens and its related diseases and has a high application value for ophthalmology.

Ultrasound biomicroscopy image patterns in normal upper eyelid and congenital ptosis in the Indian population

Purpose

To study the features of upper eyelid in healthy individual and different types of congenital ptosis in the Indian population using ultrasound biomicroscopy (UBM).

Methods

This was a prospective observational study at a tertiary care center. Eyelid structure of healthy individuals with no eyelid abnormalities (n = 19); simple congenital ptosis (n = 33) cases; Marcus Gunn jaw-winking ptosis (MGJWP, n = 7) cases, and blepharophimosis-ptosis-epicanthus inversus syndrome (BPES, n = 20) cases were studied on a vertical UBM scan using 50-MHz probe. Lid-thickness, tarsal-thickness, orbicularis oculi and levator-Muller-orbital septum-conjunctival (LMSC) complex were measured in primary gaze. Comparison was made between four groups and results were statistically analyzed using ANOVA test. In normal individuals, LMSC measurements were repeated in down-gaze imaging.

Results

Skin with subcutaneous tissue, LMSC complex and pre-aponeurotic fat-pad appeared echodense while orbicularis oculi and tarsus appeared echolucent. In primary gaze, mean thickness (± standard deviation) of the eyelid, tarsus, orbicularis oculi and LMSC, respectively, were: 1.612 ± 0.205, 0.907 ± 0.098, 0.336 ± 0.083, and 0.785 ± 0.135 mm in normal individual. LMSC showed 46.64% increase in thickness on down-gaze. The mean eyelid thickness and LMSC were thicker in MGJWP and BPES as compared to normal. In different types of congenital ptosis cases, various patterns of UBM imaging were observed.

Conclusion

UBM allows noninvasive imaging of eyelid structures with good anatomical correspondence in normal eyelids and study the structural alterations of eyelids in different types of congenital ptosis. UBM can be used to highlight the anatomical difference in normal eyelids that may help modify the surgery for better cosmetic outcomes. Furthermore, it has the potential to be used in preoperative evaluation and operative planning in certain types of acquired ptosis, which needs to be evaluated.

Mechanism of accommodation assessed by change in precisely registered ocular images associated with concurrent change in auto-refraction

PURPOSE

Our purpose was to determine the changes in anterior chamber depth (ACD) and central lens thickness (CLT) during pharmacologically induced accommodation.

METHODS

Following pupillary dilation with phenylephrine 10%, baseline auto-refractions and swept-source optical coherence tomographic biometric images (Zeiss IOLMaster 700) were obtained from the right eyes of 25 subjects aged 19 to 24 years. Pilocarpine 4% and phenylephrine 10% were then instilled into these right eyes. One hour later, auto-refractions and biometric imaging were repeated. Only data from eight of 25 subjects met the following stringent criteria to be included in the study analysis: pre and post-pilocarpine biometric foveal images were registerable, the images of the corneal centers were shifted by ≤100 μm, pupils >5 mm and the pharmacologically induced refractive change was ≥ -7 diopters.

RESULTS

The mean auto-refractive accommodative change for the eight included subjects was -12.45 diopters (± 3.45 diopters). The mean change in CLT was 81 μm (± 54 μm) and the mean change in ACD was -145 μm (± 86 μm). Superimposition of the registered pre and post-pilocarpine biometric images of the sagittal sections of the whole eye from each subject demonstrated that the position of the whole lens did not shift either anteriorly, posteriorly or vertically during pharmacologically induced accommodation.

CONCLUSIONS

A small increase in lens thickness was associated with a large change in accommodative amplitude and no significant change in lens position as predicted by the Schachar theory.

Image registration reveals central lens thickness minimally increases during accommodation

Purpose

To evaluate anterior chamber depth, central crystalline lens thickness and lens curvature during accommodation.

Setting

California Retina Associates, El Centro, CA, USA.

Design

Healthy volunteer, prospective, clinical research swept-source optical coherence biometric image registration study of accommodation.

Methods

Ten subjects (4 females and 6 males) with an average age of 22.5 years (range: 20–26 years) participated in the study. A 45° beam splitter attached to a Zeiss IOLMaster 700 (Carl Zeiss Meditec Inc., Jena, Germany) biometer enabled simultaneous imaging of the cornea, anterior chamber, entire central crystalline lens and fovea in the dilated right eyes of subjects before, and during focus on a target 11 cm from the cornea. Images with superimposable foveal images, obtained before and during accommodation, that met all of the predetermined alignment criteria were selected for comparison. This registration requirement assured that changes in anterior chamber depth and central lens thickness could be accurately and reliably measured. The lens radii of curvatures were measured with a pixel stick circle.

Results

Images from only 3 of 10 subjects met the predetermined criteria for registration. Mean anterior chamber depth decreased, −67 μm (range: −0.40 to −110 μm), and mean central lens thickness increased, 117 μm (range: 100–130 μm). The lens surfaces steepened, anterior greater than posterior, while the lens, itself, did not move or shift its position as appeared from the lack of movement of the lens nucleus, during 7.8 diopters of accommodation, (range: 6.6–9.7 diopters).

Conclusion

Image registration, with stable invariant references for image correspondence, reveals that during accommodation a large increase in lens surface curvatures is associated with only a small increase in central lens thickness and no change in lens position.

Predicting Accommodative Response Using Paraxial Schematic Eye Models

PURPOSE

Previous ultrasound biomicroscopy (UBM) studies showed that accommodative optical response (AOR) can be predicted from accommodative biometric changes in a young and a pre-presbyopic population from linear relationships between accommodative optical and biometric changes, with a standard deviation of less than 0.55D. Here, paraxial schematic eyes (SE) were constructed from measured accommodative ocular biometry parameters to see if predictions are improved.

METHODS

Measured ocular biometry (OCT, A-scan, and UBM) parameters from 24 young and 24 pre-presbyopic subjects were used to construct paraxial SEs for each individual subject (individual SEs) for three different lens equivalent refractive index methods. Refraction and AOR calculated from the individual SEs were compared with Grand Seiko (GS) autorefractor measured refraction and AOR. Refraction and AOR were also calculated from individual SEs constructed using the average population accommodative change in UBM measured parameters (average SEs).

RESULTS

Schematic eye calculated and GS measured AOR were linearly related (young subjects: slope = 0.77, r = 0.86; pre-presbyopic subjects: slope = 0.64, r = 0.55). The mean difference in AOR (GS - individual SEs) for the young subjects was -0.27D and for the pre-presbyopic subjects was 0.33D. For individual SEs, the mean ± SD of the absolute differences in AOR between the GS and SEs was 0.50 ± 0.39D for the young subjects and 0.50 ± 0.37D for the pre-presbyopic subjects. For average SEs, the mean ± SD of the absolute differences in AOR between the GS and the SEs was 0.77 ± 0.88D for the young subjects and 0.51 ± 0.49D for the pre-presbyopic subjects.

CONCLUSIONS

Individual paraxial SEs predict AOR, on average, with a standard deviation of 0.50D in young and pre-presbyopic subject populations. Although this prediction is only marginally better than from individual linear regressions, it does consider all the ocular biometric parameters.

Distortion Correction of Visante Optical Coherence Tomography Cornea Images

PURPOSE

Quantitative biometry measurements from uncorrected anterior segment optical coherence tomography (AS-OCT) images are inaccurate because of spatial and optical distortions. Prior reported distortion correction equations for the Visante AS-OCT were not reproducible. The goal was to calculate the distortions and provide equations to correct corneal parameters for the Visante AS-OCT to get a central corneal radius of curvature from young and older subjects.

METHODS

Five contact lenses (CLs) of known front and back radii of curvature and central thickness were imaged using the Visante AS-OCT (Carl Zeiss, Dublin, CA). Contact lens surface coordinates from Visante images were identified and fitted with a circle using custom Matlab image analysis software. Spatial and optical distortions of the Visante image of the CL radii of curvature and thickness were calculated and corrected. Visante images were also captured from 24 younger (aged 21 to 36 years) and 30 older (aged 36 to 48 years) human subjects. Corneal radii of curvature and thickness measurements from these subjects were corrected, and intrasession and intersession repeatabilities of the corneal parameters were calculated.

RESULTS

Root mean square error of radius and power of the CL surfaces after distortion correction were 0.02 mm and 0.18D for the front and 0.011 mm and 0.11D for the back, respectively. Intraclass correlation coefficient for intrasession and intersession repeatability for all the corneal parameters from the human subjects was greater than 0.88 in both age groups.

CONCLUSIONS

A distortion correction algorithm was developed for the Visante AS-OCT and applied to extract human corneal radius of curvature measurements.