Is visual memory predictive of below-average academic achievement in second through fourth graders?

PURPOSE: Controversy exists regarding the relation between visual memory and academic achievement. METHODS: A masked investigation of the relation between visual memory and academics was performed in 155 second-through fourth-grade children (mean age = 8.83 years). Visual memory ability was assessed with the Test of Visual Perceptual Skills visual memory subtest. The school administered the Otis-Lennon School Ability Test and Stanford Achievement Test. Age and verbal ability were controlled in all regression analyses. RESULTS: Visual memory score was significantly predictive of below-average word decoding (p = 0.027), total math score (p = 0.031), and Stanford complete battery score (p = 0.018). Visual memory score showed a positive trend in predicting reading comprehension (p = 0.093). CONCLUSIONS: Poor visual memory ability (as measured by the Test of Visual Perceptual Skills) is significantly related to below-average reading decoding, math, and overall academic achievement (as measured by the Stanford Achievement Test) in second- through fourth-grade children, while controlling for age and verbal ability.     

Accommodative facility in eyes with and without myopia

PURPOSE: To compare accommodative facility in eyes with myopia to that in eyes with emmetropia or hyperopia and to determine whether accommodative facility can be used to predict an association with myopia. METHODS: In the Sydney Myopia Study, year-1 school children (6.7 +/- 0.4 years) were assessed for accommodative facility at distance (3 m) and near (33 cm) with semiautomated flippers. Spherical equivalent refractive error (RE) was defined as myopia (< or = -0.50 D), emmetropia (> -0.50 D, but < +1.50 D), and hyperopia (> or = +1.50 D) based on postcycloplegia readings. Only right eye data were considered. Differences between groups were analyzed with the Brown-Forsythe F test after adjustment for age and gender. Multiple comparisons were adjusted with the by the Games-Howell METHOD: RESULTS: Of the 1328 right eyes assessed, 20 (1.5%) eyes were myopic, 977 (73.6%) were emmetropic, and 331 (24.9%) were hyperopic. At distance, mean facility was less for myopic eyes at 5.5 +/- 2.0 cycles per minute (cpm) in comparison to 6.9 +/- 1.7 cpm for eyes with emmetropia or hyperopia (P = 0.005). Myopic eyes recorded greater positive and negative accommodative response times than did emmetropic or hyperopic eyes (P < 0.05). There were no differences among the groups in near facility. The area under the receiver operating characteristic (ROC) curve for distance facility was 0.692 (P = 0.003, 95% CI, 0.580-0.805). CONCLUSIONS: Myopic eyes have reduced accommodative facility at distance, and accommodative responsiveness to both positive and negative defocus is slow. However, accommodative facility as a test does not have sufficient power to discriminate eyes with myopia from other refractive errors.     

Accommodative response during distance optometric test procedures.

The control of accommodation is an essential requirement during the clinical optometric assessment of distance vision. Accordingly, the aim of the present study was to examine the steady-state accommodative response during a number of conventional clinical procedures carried out at a viewing distance of 6m (20 feet). Accommodation was measured subjectively to Snellen letters using a Hartinger coincidence optometer during distance viewing, simulated retinoscopy and following the introduction of cylindrical and prismatic lenses in 13 visually-normal, young adults. No significant change in the mean accommodative response was induced by any of the techniques described, with subjects exhibiting a lead of accommodation of approximately 0.25D for all conditions. The results demonstrate the robustness of accommodation to apparently substantial changes in stimulus conditions.     

白内障超声乳化术后假晶状体眼的调节灵活度

目的探讨白内障超声乳化人工晶状体植入术后的调节灵活度,为临床改善假晶状体眼者生活质量提供依据。方法30人60眼,年龄(62.77±5.27)岁(50～70岁)。其中单眼假晶状体眼16人,双眼假晶状体眼14人,44眼为假晶状体眼。测量调节幅度、近距离调节灵活度。采用SPSS11.0行统计学分析。结果移近法单眼调节幅度(2.35±1.14)D,单眼调节灵活度(13.68±4.47)周/分,双眼调节灵活度(11.76±3.66)周/分,单眼调节灵活度与单眼调节幅度不存在相关(r=0.023,P=0.442)。结论对于白内障超声乳化术后的假晶状体眼患者,调节灵活度是独立于调节幅度的伪调节评价指标。     

两种矫正方式对调节滞后量和调节灵敏度的对比研究

目的研究青少年近视患者在佩戴角膜塑形镜与佩戴框架眼镜后各自调节滞后量和调节灵敏度的变化情况,并进行对比分析,进一步明确角膜塑形镜与框架眼镜对近视患者视功能的影响及对青少年近视的控制作用。方法随机选取60例来我院成功验配角膜塑形镜的青少年近视患者作为实验组,随机选取60例门诊就诊并给予框架眼镜的青少年近视患者作为对照组,观察两组患者屈光矫正前后调节滞后量、调节灵敏度和等效球镜度的变化并进行对比研究。随访时间依次为1个月、6个月、1年。结果 (1)调节滞后量:实验组戴镜前和戴镜后1个月、6个月、1年分别为:1.05±0.28、0.92±0.16、0.62±0.13、0.64±0.18,差异有统计学意义(P<0.05)。对照组戴镜前和戴镜后1个月、6个月、1年分别为:1.03±0.27、1.03±0.19、0.82±0.11、1.08±0.16。两组戴镜前差异无统计学意义(P>0.05),戴镜后差异均有统计学意义(P<0.05)。(2)调节灵敏度:实验组戴镜前和戴镜后1个月、6个月、1年分别为:9.33±2.65、10.82±2.06、10.90±2.48、11.05±2.55,差异有统计学意义(P<0.05)。对照组戴镜前和戴镜后1个月、6个月、1年分别为:9.56±2.32、10.76±1.88、10.85±2.08、9.02±1.97。两组戴镜前差异无统计学意义(P>0.05);戴镜后1个月、6个月两组差异无统计学意义(P>0.05);戴镜后1年两组差异有统计学意义(P<0.05)。(3)观察1年:实验组等效球镜度增加了(0.38±0.35)DS,对照组增加了(0.84±0.56)DS,两组差异有统计学意义(P<0.05)。结论 (1)实验组戴镜后对调节滞后量的改善较明显,并使其逐渐趋于正常化;对照组对调节滞后量改善较慢,不能使其达到正常值,且近视度数增长后调节滞后量会变大。(2)实验组对调节灵敏度的改善更快,对照组较慢,在近视度数没有明显增长的情况下,两组的调节灵敏度相似,近视度数增长后调节灵敏度下降。(3)角膜塑形镜对中低度近视的矫正有效,它较框架眼镜能更有效地控制青少年近视的增长速度,是目前控制近视的一种有效方法。     

Accommodative and fusional components of fixation disparity.

Traditional measurements of fixation disparity, like other binocular measurements, confound influences from both blur-driven and disparity-driven components. Measuring fixation disparity with accommodation open-loop eliminates accommodative interactions, and results show fixation disparity is reduced to about half the value observed normally for high levels of forced vergence. Thus fixation disparity curves are shaped by both accommodative and fusional vergence processes.     

Clinical testing of accommodative facility: part III. Masked assessment of the relation between visual symptoms and binocular test results in school children and adults.

BACKGROUND: Accommodative facility is commonly assessed using +/- 2.00 lenses at 40 cm. Significant differences have been demonstrated on binocular facility testing between symptomatic and asymptomatic children; studies on adults have not replicated these results. We evaluate the relation between symptoms and binocular amplitude-scaled facility (equivalent stimulus for each subject based on individual amplitude). METHODS: Optometry students (N = 98) and school children IN= 152) participated in a vision screening. A 9-question standardized questionnaire quantified symptoms. Binocular accommodative facility was assessed using random presentation of standard and amplitude-scaled facility, without knowledge of symptom level. Subjects with abnormal binocular vision were excluded from data analysis. RESULTS: For children, both amplitude-scaled (p = 0.0004). and standard accommodative facility (p = 0.0055) significantly differentiated symptomatic from asymptomatic responses. For adults, amplitude-scaled responses were significantly different (p= 0.0228) between symptomatic and asymptomatic subjects; standard testing results were not (p = 0.2013). CONCLUSION: Binocular amplitude-scaled facility testing (test distance 45%, lens power range 30% of push-up amplitude) identifies symptomatic adults at high significance level. And both children and adults perform similarly on amplitude-scaled testing. These results suggest that amplitude-scaled binocular accommodative facility should be the test of choice for evaluation of patients between the age of 8 years and the onset of presbyopia. Patients who perform less than 10 cycles per minute are likely to be symptomatic.     

Accommodative facility training with a long term follow up in a sample of school aged children showing accommodative dysfunction

The primary aim of this project was to study the effect of flip lens-training on the accommodative function in a group of children with accommodative dysfunction and subjective symptoms such as asthenopia, headache, blurred vision, and avoidance of near activity. We also wanted to measure the accommodative facility among the children in comparison with a control group. Another aim of the study was whether flip lens-training increased accommodative facility, and to find out if it also had a positive effect on their asthenopia and related problems also in long term. Following the training period the accommodative facility and accommodative function significantly increased and two years after finishing the training period no child had regained any subjective symptoms and the objective findings were almost the same as at the end of facility training period. These results suggest that accommodative facility training is an efficient method built on loss of symptoms among children with accommodative infacility. This revised version was published online in July 2006 with corrections to the Cover Date.     

Accommodative vergence in the alert monkey. Motor unit analysis

The behavior of both abducens nucleus and oculomotor nucleus motoneurons during accommodative vergence eye movements is examined in the alert monkey. This behavior is compared with that of the same neurons during versional eye movements. The behavior is found to be identical, which indicates that oculomotor unit discharge is determined by fixation angle without regard to the type of movement used to reach that angle. Detailed statistical analysis of unit firing rate also suggests that the separate inputs controlling vergence and version are probably combined at some supranuclear level before the motoneuron. The firing rates of motoneurons during the dynamic phase of a vergence movement is examined and compared to that during pursuit movements in an attempt to correlate neuron discharge with the mechanical dynamics of the orbit.     

Binocular and Accommodative Characteristics in a Normal Population

Purpose: To study binocular and accommodative characteristics and their associations with age and gender in an Iranian young adult population.

Methods: In this cross-sectional study, multistage cluster sampling was done from the students of Mashhad University of Medical Sciences. All participants had visual acuity, refraction, and cover tests followed by measurements of the near point of convergence (NPC), amplitude of accommodation (AA), monocular and binocular accommodative facility (MAF and BAF) using ±2.00 diopter (D) flipper lenses, and negative and positive relative accommodation (NRA and PRA). Near and distance fusional vergence reserves were measured using prism bar, and near associated phoria was assessed using the Mallett unit.

Results: The mean age of the participants was 22.5±4.4 years (range: 18-35 years). The binocular and accommodative characteristics and their means in the studied sample included: mean distance dissociated phoria: 1.15 exophoria±2.04 prism diopters (PD), near dissociated phoria: 5.02 exophoria±4.74 PD, near associated phoria: 0.55 base-in±1.02, gradient accommodative convergence/accommodation (AC/A) ratio: 4.66±1.59, NPC: 5.27±3.60 cm, MAF: 11.33±5.58 cpm, BAF: 8.84±4.47 cpm, NRA: 2.08±0.33 D, PRA:-2.92±0.76 D, and AA: 11.14±2.6 D. In the multiple regression model including age and gender, near exophoria was significantly higher in men and levels of near base-out-break and near base-out-recovery were higher in females. Distance exophoria, distance base-in-break, distance base-in-recovery, and NPC increased with age and near base-out-break, PRA, BAF, MAF, and AA significantly decreased with age.

Conclusion: Studied indices in this study significantly differ from available guidelines and these differences must be considered when making diagnostic or therapeutic decisions. Certain indices can be affected by age and gender.     

Tonic accommodation: a review. II. Accommodative adaptation and clinical aspects

Part I of this review considered basic aspects of tonic accommodation (TA). i.e. the accommodative response observed under degraded stimulus conditions. Part II considers accommodative adaptation, i.e. the apparent change in TA following periods of sustained fixation, and clinical aspects of both baseline TA and accommodative adaptation. It is suggested that the apparent post-task shift in TA reflects the slow rate of decay of the stimulus-mediated adaptive accommodative response, while the actual level of tonic innervation to the ciliary muscle remains relatively constant. The clinical implications of both TA and accommodative adaptation are discussed with regard to night, space and instrument myopia and refractive error development, notably nearwork-induced myopia. It is concluded that the evidence for any association between this form of myopia and either TA or accommodative adaptation is equivocal, and furthermore it seems likely that TA plays only a minor role in influencing the closed-loop steady-state accommodative response.     

Clinical testing of accommodative facility: part II. Development of an amplitude-scaled test.

BACKGROUND: Standard accommodative facility testing, using +/- 2.00 D lenses @ 40 cm, stresses a much different proportion of the available accommodation for a 10-year-old patient with a binocular accommodative amplitude of 12 D and a 35-year-old patient with a binocular amplitude of 5 D. This may explain why research using adult subjects has failed to associate reduced accommodative facility with symptoms. METHODS: For 19 adult subjects with normal age-related amplitudes of accommodation, accommodative facility was measured with the standard test (+/- 2.00 D @ 40 cm) and 36 experimental combinations of test distance demand and lens power range, based on percentages of each individual's amplitude. In a masked study. these results were compared to symptom scores, quantified by a 9-item quality of vision questionnaire. RESULTS: The strongest relation of facility with symptoms was for the 75% distance demand/30% power range (p = 0.0216), with six other combinations also significant. The standard test combination did not significantly differentiate symptomatic from asymptomatic subjects (p = 0.1 515). The combination of the 45% distance demand/30% power range was significantly related to symptom score (p = 0.0315; r = -0.47603). CONCLUSION: Amplitude scaled facility testing provides the same percentage test distance and range of amplitude stimulated for all patients. The 45%/30% test combination differentiates symptomatic from asymptomatic subjects better than the standard test (+/- 2.00 D @ 40 cm) and is the one we suggest for future clinical investigation. Care should be taken when testing symptomatic patients over a long period of time, as they may compensate by relying on a predictor operator during the highly repetitive accommodative facility test, thus achieving a more-rapid response.