Myopia Control Dose Delivered to Treated Eyes by a Dual-focus Myopia-control Contact Lens.

PURPOSE: This study examined the optical impact of a DF contact lens during near viewing in a sample of habitual DF lens wearing children. METHODS: Seventeen myopic children aged 14 to 18 years who had completed 3 or 6 years of treatment with a DF contact lens (MiSight 1 Day; CooperVision, Inc., San Ramon, CA) were recruited and fit bilaterally with the DF and a single-vision (Proclear 1 Day; CooperVision, Inc.) contact lens. Right eye wavefronts were measured using a pyramidal aberrometer (Osiris; CSO, Florence, Italy) while children accommodated binocularly to high-contrast letter stimuli at five target vergences. Wavefront error data were used to compute pupil maps of refractive state. RESULTS: During near viewing, children wearing single-vision lenses accommodated on average to achieve approximate focus in the pupil center but, because of combined accommodative lag and negative spherical aberration, experienced up to 2.00 D of hyperopic defocus in the pupil margins. With DF lenses, children accommodated similarly achieving approximate focus in the pupil center. When viewing three near distances (0.48, 0.31, and 0.23 m), the added +2.00 D within the DF lens treatment optics shifted the mean defocus from +0.75 to -1.00 D. The DF lens reduced the percentage of hyperopic defocus (≥+0.75 D) in the retinal image from 52 to 25% over these target distances, leading to an increase in myopic defocus (≤-0.50 D) from 17 to 42%. CONCLUSIONS: The DF contact lens did not alter the accommodative behavior of children. The treatment optics introduced myopic defocus and decreased the amount of hyperopically defocused light in the retinal image.

Accommodative Behavior, Hyperopic Defocus, and Retinal Image Quality in Children Viewing Electronic Displays.

SIGNIFICANCE: The prevalence of myopia and use of electronic displays by children has grown rapidly in recent years. We found that children viewing electronic displays, however, experience hyperopic defocus levels similar to those previously reported for other stimuli. PURPOSE: This study aimed to compare accommodative behavior of nonmyopic and myopic children viewing a computer screen or mobile phone. METHODS: Accommodative behavior was examined in 11 nonmyopic and 8 myopic children (11.32 ± 2.90 and 14.13 ± 2.30 years, respectively; P = .04; refractions, +0.51 ± 0.51 and -2.54 ± 1.29, respectively) using an open-field autorefractor (Grand Seiko) at target vergences from -0.25 to -5.00 D. Different size (scaled or nonscaled) and type (text or movie) stimuli were presented on an LCD monitor (distant) or an iPhone (near), with subjects viewing monocularly or binocularly in an illuminated or dark room. RESULTS: At the typical reading distances (20 and 33 cm), all 19 children exhibited some amount of accommodative lag. Stimulus type had little impact on accommodation. However, slightly but statistically significant lower slopes were observed (Bonferroni-corrected significance level of P ≤ .01) for low room lighting (0.96 vs. 0.91; t test, t = 3.88; P = .003), nonscaled targets (0.99 vs. 0.92; t test, t = 4.28; P = .001), and monocular viewing (0.99 vs. 0.90; t test, t = 4.0; P = .002) in the nonmyopic group only. When viewing nonscaled stimuli binocularly (natural viewing), the means and standard deviations of accommodative lags (averaged across room lights on and off, and text and movie) were generally larger for the nonmyopes at all distances and were largest at 33 cm (0.73 ± 0.18 D for the nonmyopes and 0.49 ± 0.23 for the myopes; t test, t = 2.62; P = .01). CONCLUSIONS: Generally small (≤0.50 D) amounts of hyperopic defocus are present in children binocularly viewing handheld electronic devices (nonmyopes slightly more than myopes). Modern electronic devices do not expose children to unusually high levels of hyperopic defocus.

Experimental Model of Far Temporal Field Negative Dysphotopsia Generated in Phakic Eyes.

Purpose: The axial separation between the iris and the intraocular lens (IOL) in pseudophakic eyes can cause rays originating from the far temporal field to miss the IOL, resulting in negative dysphotopsia (ND). We developed an experimental model to test the hypothesis that obstruction of rays from the far temporal field can generate ND and an accompanying loss of visual sensitivity in the far temporal field. Methods: The right eyes of 10 phakic subjects were fitted with soft contact lenses containing a 5.50-mm central clear zone and a 12-mm outer diameter opaque annulus. In three of the subjects, eyes were dilated with 1% tropicamide solution, and effective aperture diameters were determined optically (pupil camera) and psychophysically (narrow beam detection). Visual field extent (Goldmann bowl) and temporal and inferotemporal meridian sensitivities (Octopus perimeter) were measured. A wide-angle model was constructed to quantify the impact of the annular opacity on retinal illuminance. Results: All 10 subjects observed a dark crescent in the far temporal and inferotemporal fields. The opaque annulus reduced effective horizontal pupil diameters from 8 mm to 5.5 mm on-axis and from >2 mm to <1 mm at 90°. Perimetry revealed a 10° reduction in temporal and inferotemporal field extent and increasing loss of sensitivity beyond 70°. The wide-angle model confirmed significant vignetting (>50% beyond 70°), approaching zero retinal illuminance beyond 85°. Conclusions: Vignetting of rays originating from the far temporal field by axially separated apertures can create symptoms mirroring perceptual reports of negative dysphotopsia in symptomatic pseudophakic patients.

Validation of a Clinical Aberrometer Using Pyramidal Wavefront Sensing.

SIGNIFICANCE: Measurement of ocular aberrations is a critical component of many optical corrections. PURPOSE: This study examines the accuracy and repeatability of a newly available high-resolution pyramidal wavefront sensor-based aberrometer (Osiris by Costruzione Strumenti Oftalmici, Firenze, Italy). METHODS: An engineered model eye and a dilated presbyopic eye were used to assess accuracy and repeatability of aberration measurements after systematic introduction of lower- and higher-order aberrations with calibrated trial lenses (sphere +10.00 to -10.00 D, and astigmatic -4.00 and -2.00 D with axis 180, 90, and 45°) and phase plates (-0.57 to 0.60 µm of Seidel spherical aberration defined over a 6-mm pupil diameter). Osiris aberration measurements were compared with those acquired on a previously calibrated COAS-HD aberrometer for foveal and peripheral optics both with and without multizone dual-focus contact lenses. The impact of simulated axial and lateral misalignment was evaluated. RESULTS: Root-mean-square errors for paraxial sphere (corneal plane), cylinder, and axis were, respectively, 0.07, 0.11 D, and 1.8° for the engineered model and 0.15, 0.26 D, and 2.7° for the presbyopic eye. Repeatability estimates (i.e., standard deviation of 10 repeat measures) for the model and presbyopic eyes were 0.026 and 0.039 D for spherical error. Root-mean-square errors of 0.01 and 0.02 µm, respectively, were observed for primary spherical aberration and horizontal coma (model eye). Foveal and peripheral measures of higher- and lower-order aberrations measured with the Osiris closely matched parallel data collected with the COAS-HD aberrometer both with and without dual-focus zonal bifocal contact lenses. Operator errors of focus and alignment introduced changes of 0.018 and 0.02 D/mm in sphere estimates. CONCLUSIONS: The newly available clinical pyramidal aberrometer provided accurate and repeatable measures of lower- and higher-order aberrations, even in the challenging but clinically important cases of peripheral retina and multifocal optics.

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.

Prediction of accommodative optical response in prepresbyopic subjects using ultrasound biomicroscopy.

PURPOSE: To determine whether relatively low-resolution ultrasound biomicroscopy (UBM) can be used to predict the accommodative optical response in prepresbyopic eyes as well as in a previous study of young phakic subjects, despite lower accommodative amplitudes. SETTING: College of Optometry, University of Houston, Houston, USA. DESIGN: Observational cross-sectional study. METHODS: Static accommodative optical response was measured with infrared photorefraction and an autorefractor (WR-5100K) in subjects aged 36 to 46 years. A 35 MHz UBM device (Vumax, Sonomed Escalon) was used to image the left eye, while the right eye viewed accommodative stimuli. Custom-developed Matlab image-analysis software was used to perform automated analysis of UBM images to measure the ocular biometry parameters. The accommodative optical response was predicted from biometry parameters using linear regression, 95% confidence intervals (CIs), and 95% prediction intervals. RESULTS: The study evaluated 25 subjects. Per-diopter (D) accommodative changes in anterior chamber depth (ACD), lens thickness, anterior and posterior lens radii of curvature, and anterior segment length were similar to previous values from young subjects. The standard deviations (SDs) of accommodative optical response predicted from linear regressions for UBM-measured biometry parameters were ACD, 0.15 D; lens thickness, 0.25 D; anterior lens radii of curvature, 0.09 D; posterior lens radii of curvature, 0.37 D; and anterior segment length, 0.42 D. CONCLUSIONS: Ultrasound biomicroscopy parameters can, on average, predict accommodative optical responses with SDs of less than 0.55 D using linear regressions and 95% CIs. Ultrasound biomicroscopy can be used to visualize and quantify accommodative biometric changes and predict accommodative optical response in prepresbyopic eyes.

Can ultrasound biomicroscopy be used to predict accommodation accurately?

PURPOSE: Clinical accommodation testing involves measuring either accommodative optical changes or accommodative biometric changes. Quantifying both optical and biometric changes during accommodation might be helpful in the design and evaluation of accommodation restoration concepts. This study aims to establish the accuracy of ultrasound biomicroscopy (UBM) in predicting the accommodative optical response (AOR) from biometric changes. METHODS: Static AOR from 0 to 6 diopters (D) stimuli in 1-D steps were measured with infrared photorefraction and a Grand Seiko autorefractor (WR-5100 K; Shigiya Machinery Works Ltd., Hiroshima, Japan) in 26 human subjects aged 21 to 36 years. Objective measurements of accommodative biometric changes to the same stimulus demands were measured from UBM (Vu-MAX; Sonomed Escalon, Lake Success, NY) images in the same group of subjects. AOR was predicted from biometry using linear regressions, 95% confidence intervals, and 95% prediction intervals. RESULTS: Bland-Altman analysis showed 0.52 D greater AOR with photorefraction than with the Grand Seiko autorefractor. Per-diopter changes in accommodative biometry were: anterior chamber depth (ACD): -0.055 mm/D, lens thickness (LT): +0.076 mm/D, anterior lens radii of curvature (ALRC): -0.854 mm/D, posterior lens radii of curvature (PLRC): -0.222 mm/D, and anterior segment length (ASL): +0.030 mm/D. The standard deviation of AOR predicted from linear regressions for various biometry parameters were: ACD: 0.24 D, LT: 0.30 D, ALRC: 0.24 D, PLRC: 0.43 D, ASL: 0.50 D. CONCLUSIONS: UBM measured parameters can, on average, predict AOR with a standard deviation of 0.50 D or less using linear regression. UBM is a useful and accurate objective technique for measuring accommodation in young phakic eyes.

Objective measurement of accommodative biometric changes using ultrasound biomicroscopy.

PURPOSE: To demonstrate that ultrasound biomicroscopy (UBM) can be used for objective quantitative measurements of anterior segment accommodative changes. SETTING: College of Optometry, University of Houston, Houston, Texas, USA. DESIGN: Prospective cross-sectional study. METHODS: Anterior segment biometric changes in response to 0 to 6.0 diopters (D) of accommodative stimuli in 1.0 D steps were measured in eyes of human subjects aged 21 to 36 years. Imaging was performed in the left eye using a 35 MHz UBM (Vumax) and an A-scan ultrasound (A-5500) while the right eye viewed the accommodative stimuli. An automated Matlab image-analysis program was developed to measure the biometry parameters from the UBM images. RESULTS: The UBM-measured accommodative changes in anterior chamber depth (ACD), lens thickness, anterior lens radius of curvature, posterior lens radius of curvature, and anterior segment length were statistically significantly linearly correlated with accommodative stimulus demands. Standard deviations of the UBM-measured parameters were independent of the accommodative stimulus demands (ACD: 0.0176 mm; lens thickness: 0.0294 mm; anterior lens radius of curvature: 0.3350 mm; posterior lens radius of curvature: 0.1580 mm; and anterior segment length: 0.0340 mm). The mean difference between the A-scan and UBM measurements was -0.070 mm for ACD and 0.166 mm for lens thickness. CONCLUSIONS: Accommodating phakic eyes imaged using UBM allowed visualization of the accommodative response, and automated image analysis of the UBM images allowed reliable, objective, quantitative measurements of the accommodative intraocular biometric changes. FINANCIAL DISCLOSURE: Neither author has a financial or proprietary interest in any material or method mentioned.