Bjorn Drobe

Change in Peripheral Refraction over Time in Singapore Chinese Children

PURPOSE. Relative peripheral hyperopia has been associated with central myopia. This study was conducted to determine whether baseline relative peripheral hyperopia is associated with an increased risk of developing myopia or myopia progression in young Singapore Chinese children. METHODS. One hundred eighty-seven children who participated in the Peripheral Refraction in Preschool Children (PREP) Study at baseline underwent a follow-up examination. Autorefraction was performed at five eccentricities with an infrared autorefractor after cycloplegia: central axis and 15° and 30° eccentricities in the nasal and temporal visual fields. The primary outcomes were development of myopia among children who were nonmyopic at baseline, and myopia progression in those who were myopic at baseline. RESULTS. The mean age of the children at baseline was 7.2 ± 3.0 years, and the mean duration of follow-up was 1.26 years. At baseline, 96 children were myopic (mean central spherical equivalent [SE] -2.75 ± 1.72 D) and 91 were nonmyopic (mean central SE 0.76 ± 0.81 D). Baseline relative peripheral hyperopia was not associated with a greater likelihood of becoming myopic or myopia progression. At follow-up, children who remained nonmyopic (n = 24) retained relative peripheral myopia at all eccentricities, whereas those who became myopic (n = 67) developed relative peripheral hyperopia at the nasal (+0.44 ± 0.72 D) and temporal 30° (+0.13 ± 0.74 D). The mean change in central SE was -1.51 ± 0.63 D/y for children who developed myopia, -0.82 ± 0.76 D/y for children who were myopic at baseline, and -1.05 ± 0.80 D/y for all children. CONCLUSIONS. Baseline peripheral refraction did not predict the subsequent onset of myopia or influence the progression of myopia.

Peripheral Refraction and Refractive Error in Singapore Chinese Children

PURPOSE Peripheral hyperopia was hypothesized to stimulate axial elongation. This study describes peripheral refraction and its associations with central refractive error in young Singapore Chinese children. METHODS Two hundred fifty children aged 40 months or older recruited from the Strabismus, Amblyopia, and Refractive Error in Young Singapore Children study were included in this analysis. Peripheral refraction was measured after pupil dilation using an infrared autorefractor. A total of five measurements were captured: central visual axis and 15° and 30° eccentricities in the nasal and temporal visual fields. RESULTS The mean age of the participants recruited was 83 ± 36 months. There were 37 children with high and moderate myopia (≤-3 D; 14.8%), 81 with low myopia (-2.99 to -0.5 D; 32.4%), 84 with emmetropia (-0.49 to 1.0 D; 33.6%), and 47 with hyperopia (>1.0 D; 18.8%). Compared with the central axis, children with high and moderate myopia had relative hyperopia at all peripheral eccentricities (P < 0.001), whereas children with low myopia had relative hyperopia only at the temporal and nasal 30° (P < 0.001), but not at the nasal and temporal 15°. Children with emmetropia and hyperopia had peripheral relative myopia at all eccentricities (P < 0.001). A significant correlation between the nasal and temporal refractive error at 30° was noted (Spearsons correlation coefficient = 0.85, P < 0.001). CONCLUSIONS Young myopic Singapore Chinese children had relative hyperopia in the periphery. This study substantiates previous studies in older children and in Caucasian subjects.

Stereoscopic depth perception in peripheral field and global processing of horizontal disparity gradient pattern

This study investigates how the visual system detects a surface deviation from planar, induced by, crossed or uncrossed, horizontal disparities continuously increasing with eccentricity. Binocular disparities increased linearly and concentrically, between two given eccentricities. The thresholds of deformation detection were gathered using a method in which observers halted a dynamic stimulus. The thresholds are substantially higher than those measured by the control experiment using a method of constant stimuli. Results, using the adjustment method, highlight lower discrimination thresholds for uncrossed disparities than for crossed disparities. For the two directions of disparity, thresholds vary similarly as a function of eccentricity, however two observations can be pointed out: thresholds of peripheral start depend on disparity gradient and starting eccentricity; foveal start thresholds do not depend on disparity gradient alone. Data suggests that, in peripheral field, the visual system is more sensitive to uncrossed disparities than crossed disparities, relative to the frontoparallel plane. According to a verbal report from observers, the reference used for the perceptive judgment appears not to be the screen plane but rather the peripheral stimulus. Moreover, in the deformation detection of planar surfaces, horizontal disparities processing depends on the eccentric location of the disparities. It could be global for the peripheral locations and could be based more on depth contrast for the central locations.

The effects of spatial frequency on the accommodation responses of myopes and emmetropes under various detection demands.

The dependence of spatial frequency on accommodation has been investigated extensively. Recently, differences between myopes and emmetropes with respect to accommodative microfluctuations for high spatial frequency targets have been reported. Considering the diversity of accommodative responses (ARs) to sinusoidal gratings among subjects, this experiment was designed to analyze the contrast dependence of ARs to targets with various spatial frequencies (SFs). Here, we continuously measured ARs, microfluctuations, and pupil diameter while emmetropic and myopic adult subjects fixated on sinusoidal grating targets of various SFs under standard and near-detection threshold contrast conditions. We first evaluated the detection contrast thresholds at six SFs (2-16 cpd) using a near-contrast sensitivity function test that simulated the CSV-1000 test with a tablet computer. We found no difference in contrast threshold between emmetropes and myopes. We then measured the dynamic ARs to 24 grating targets: six SFs and four contrasts (standard, detection threshold, subthreshold and suprathreshold) were recorded for 30s. Under standard contrast conditions, we observed a decrease in AR with increasing spatial frequency. Variations in pupil diameter and accommodation were the smallest at 6 cpd. Both the ARs and microfluctuations were higher under near-threshold contrast conditions than under standard contrast conditions, and no variations were found across SFs under near-threshold contrast conditions. No differences in ARs or microfluctuations were found between the two refractive groups at any spatial frequency. These findings provided detailed information on accommodative behavior to spatial frequency targets under normal and high-detection demand conditions.

Comparison of Near Addition Value Prescription Methods for Myopic Children.

Purpose To compare personalized near addition values for myopic children that induce a reasonable phoria (Ph) (meeting Sheards criterion) and induce a null lag of accommodation at near and to evaluate changes in these metrics after lens adaptation. Methods Fifty-three myopic children participated in this study. Accommodative response, Ph, and fusional amplitudes (FAs) were measured at 33 cm through multiple addition lenses (0D, +1.00D, +1.50D, +2.00D, +2.50D, +3.00D). The adaptation effect on measured parameters was evaluated after 6 min of near work with each addition. The FA/Ph ratios were calculated for each addition and fitted using a rational function to obtain the optimal addition value satisfying Sheards criterion (FA/Ph ≥ 2). Lag of accommodation change in association with addition value was assessed using linear regressions to obtain the addition values inducing a null lag. Results Lag of accommodation (r = −0.987, p < 0.001) and Ph (r = −0.999, p < 0.001) decreased linearly with addition value. The 6-min adaptation induced a small but significant increase in accommodative lag and an exophoric shift (p < 0.05). Three FA/Ph patterns with respect to addition lenses were observed based on the near Ph: orthophoria/exophoria, low esophoria, and large esophoria. Addition values based on Sheards criterion (mean ± SD, +2.16 ± 0.79D) were significantly lower than those based on null lag (+2.83 ± 0.44D, t = 19.86, p < 0.001). The FA/Ph ratio was less than 2.0 in 75.5% of subjects with additions determined through null accommodative lag. Additions determined through FA/Ph ≥ 2 induced a lag of accommodation of 0.38 ± 0.42D. Conclusions Personalized near addition values using Sheards criterion were lower than those obtained through null lag of accommodation. These values should allow a better binocular balance especially for exophoric children.

Comparison of three monocular methods for measuring accommodative stimulus–response curves

The aim was to evaluate the repeatability of dynamic measurement of the accommodative stimulus–response curve (ASRC) at three different dioptric speeds using a modified instrument and its agreement with two other methods.

Influence of progressive addition lenses on reading posture in myopic children

Aims To determine the influence of single-vision lenses (SVLs) and progressive addition lenses (PALs) on the near vision posture of myopic children based on their near phoria. Methods Sixty-two myopic children were assigned to wear SVLs followed by PALs. Eighteen children were esophoric (greater than +1), 18 were orthophoric (−1 to 1) and 26 were exophoric (less than −1) at near. Reading distance, head tilt and ocular gaze angles were measured using an electromagnetic system after adaptation to each lens type. Results The lens type did not influence reading distance or head tilt angle (p>0.05 for both), but ocular gaze angle decreased significantly with the PALs (F=9.25, p=0.004). With the PALs, exophoric children exhibited significantly increased head tilt angle (p=0.003) and reduced ocular gaze angle (p=0.004) compared with esophoric children. Near non-exophoric children exhibited similar eye and head postures when wearing SVLs and PALs, whereas exophoric children exhibited reduced ocular gaze angle (t=−3.18, p=0.04) with PALs compared with SVLs. Using PALs for reading, the mean addition power employed by esophoric children was significantly greater than exophoric children (p=0.04). Conclusions The lens type and the near phoria state affected near vision posture. During reading, myopic esophoric children used a lower portion of their PALs compared with exophoric children, resulting in greater addition power. These results may partially explain why myopic children with near esophoria exhibited superior treatment effects in myopia control trials using PALs.

Influence of Near Tasks on Posture in Myopic Chinese Schoolchildren.

PurposeTo investigate near-vision posture in Chinese myopic schoolchildren and compare near-vision posture during different near-vision tasks (i.e., playing video games, reading, and writing). MethodsThe study investigated 120 myopic children (grades 1 through 6 and aged 6 to 13 years). An electromagnetic motion-tracking system was used for continuous measurements of the working distance and head declination of the subjects while they were playing video games or reading or writing at a desk. The reading and writing documents were adjusted by grade level (i.e., grades 1 to 2, 3 to 4, and 5 to 6). For analysis, the subjects were grouped in two refractive groups according to their median spherical equivalent refractive error (−1.50D). ResultsThe myopic schoolchildren used close working distances for all tasks: 21.3 ± 5.2 cm (video games), 27.2 ± 6.4 cm (reading), and 24.9 ± 5.8 cm (writing). The mean head declinations were 63.5 ± 12.2 deg (video games), 37.1 ± 12.8 deg (reading), and 44.5 ± 14.1 deg (writing). Working distance decreased significantly across time for the reading and writing tasks (p < 0.001). Head declination increased significantly across time only for the reading task (p < 0.001). Grade level significantly influenced working distance, but the difference was not significant when working distance was adjusted by the subject’s size. No differences were observed within the refractive or the accommodative lag groups in terms of the posture data (p > 0.05). Working distance was negatively correlated with head declination (r = −0.53, p < 0.001). ConclusionsClose working distances were observed for Chinese myopic schoolchildren. The attention dedicated to each task, the task difficulty, and the page/screen size may affect near working distance and head declination. Handheld video games were associated with the closest working distance, which may be a risk factor for myopia progression, according to previous studies.

Design, methodology, and baseline data of the Personalized Addition Lenses Clinical Trial (pact)

Background: The aim of this study was to describe the design, methods, and baseline characteristics of children enrolled in the Personalized Addition lenses Clinical Trial (PACT). PACT aims to test the myopia control efficacy of progressive addition lenses (PALs) with personalized addition values compared with standard (+2.00 D) addition PALs and single vision lenses (SVLs). Methods: PACT is a randomized, controlled, double-masked clinical trial. Two hundred eleven myopic Chinese children (7–12 years) were enrolled and randomized into 1 of the 3 following groups: personalized addition PALs; +2.00 addition PALs; and SVLs. Personalized addition values were determined based on the highest addition that satisfied Sheard criterion. Axial length and other biometric data were also recorded. Results: At baseline, no differences were found between the right and left eyes for any of the main parameters. The enrolled children were 9.7 ± 1.1 years’ old with cycloplegic autorefraction (right eye [OD]: −2.36 ± 0.64 D), near phoria (1.0 ± 5.0 prism diopter esophoria), lag of accommodation (1.40 ± 0.50 D) and axial length (OD: 24.58 ± 0.74 mm). The personalized addition values ranged from +0.75 to +3.00 (average ± SD: 2.19 ± 0.73 D). Conclusion: PACT is a clinical trial evaluating whether myopia progression in children can be slowed by wearing personalized addition PALs compared with fixed addition PALs and SVLs as measured by cycloplegic autorefraction and axial length. Baseline data were comparable with those of previous myopia control studies in children. Subjects will be followed up every 6 months for 2 years.

Effects of Near Addition Lenses and Prisms on Accommodative Microfluctuations in Chinese Children.

Purpose To investigate the effects of different near addition lenses and prisms on accommodative microfluctuations (AMFs) in Chinese early-onset myopic (EOM) and emmetropic (EMM) children. Methods Twenty-one EMM and 27 EOM children aged between 9 and 14years participated in the study. At near, 23 children were exophoric (exo, <0 &Dgr;), and 25 were esophoric (eso, ≥0 &Dgr;). The AMFs and phoria through multiple addition lenses (−1.00, 0, +1.00, +2.00, and +3.00D on each eye) and prisms (base-in prism power: 3 &Dgr;, 2 &Dgr;, 1 &Dgr;; and base-out prism power: 1 &Dgr; and 2 &Dgr; on each eye) were measured at 25cm under binocular viewing conditions with a Grand Seiko WAM-5500 auto-refractor and a modified Thorington card. Results Higher AMFs were found in EOM than in EMM (EOM, 0.19±0.06D; EMM, 0.16±0.03D; p=0.035). Plus additions from +1.00 to +3.00D reduced the AMFs in both EMM and EOM, except +3.00D for EMM. In both refractive groups, −1.00D additions increased AMFs. Esophores showed greater AMFs compared with exophores (esophores, 0.20±0.01D; exophores, 0.16±0.01D; p=0.012). Prisms increased the AMFs in EMM and did not alter the AMFs in EOM. Conclusions Microfluctuations of accommodation decreased with plus addition lenses and increased with negative addition lenses. Plus addition lenses of +2.00 to +3.00D for EOM and +2.00D for EMM decreased AMFs the least at a 25-cm working distance. Esophores had higher AMFs than exophores, indicating that phoria status influences AMFs.