The component of gaze selection/control in the development of visual acuity in children

Visual acuity was tested for 180 eyes of 90 children in four age groups using three types of test charts. Subjects read the same 10 high-contrast letters in Snellen (line) format, as isolated-letter flash cards, and as repeat-letter flash cards. Group mean line and group mean isolated-letter acuity showed similar progressive improvements with age. A subgroup of 24 of 50 eyes of 4- to 5-year-olds (15 of 25 subjects) and 3 of 50 eyes of 6- to 7-year-old (2 of 25 subjects) had low Snellen acuity. Of this low-acuity subgroup of 27 eyes, 10 scored above average for their age group on the repeat-letter chart. We concluded that abnormal lateral interactions were not the explanation for the immaturity of Snellen acuity in these 10 eyes. We suggest that an important factor in the low acuities of these 10 eyes is delayed development of the selection and/or control of gaze direction. Some eyes with excellent Snellen acuity showed high crowding. For example, there were five such eyes in the oldest group. We suggest that the excellent acuities of at least two of these eyes are limited by minor inaccuracies in gaze selection and/or control rather than by lateral interaction.     

Impact of myopia control spectacle lenses with highly aspherical lenslets on peripheral visual acuity and central visual acuity with peripheral gaze

Purpose

Myopia control spectacle lenses with peripheral lenslets are gaining popularity because they are non-invasive and easy to manage, and ongoing clinical trials have shown promising results. This study aimed to evaluate peripheral and central visual acuity (VA) with peripheral gaze in conditions where the eyes are turned to look obliquely through the lenslets.

Methods

High-contrast (100%) VA was measured at 300 cm and 10 lx. For each test, two lens designs were evaluated in counterbalanced order: a spectacle lens with highly aspherical lenslets (HALs) and a standard single-vision lens (SVL). The target screen was placed at a visual angle of 21.6° to the nasal side of the right eye. Sixteen adults (27–52 years of age; spherical equivalent refraction (SER), −8.75 D to +0.50 D) wearing their habitual visual correction performed all tests monocularly.

Results

Mean (SD) central VAs with peripheral gaze through the SVL and the HAL lens were 0.08 (0.13) and 0.17 (0.12) logMAR, respectively. The HAL lens reduced central VA with peripheral gaze by 0.10 (0.08) logMAR (p = 0.03). No significant correlation was observed between the impact of the HAL lens and other factors, such as age or SER. Peripheral VA was not significantly different through the two lenses (1.09 (0.06) logMAR and 1.09 (0.09) logMAR for the SVL and the HAL lens, respectively; p = 0.86).

Conclusions

Under high-contrast and low-luminance conditions, the HAL lens reduced central VA with peripheral gaze by approximately one line compared with the SVL. The impact on central VA did not vary with gaze direction, age or SER. The HAL lens did not affect peripheral VA in this condition.     

3～11岁视力低常儿童散光与弱视分析

目的探讨3~11岁儿童弱视散光类型、散光度分布、散光轴分布、双眼散光轴关系、散光轴与弱视的关系。方法对门诊3~11岁视力低常儿童266例(503只眼)散光状况进行统计分析。结果复性远视散光居多,占71.07%,依次为复性近视散光11.53%,混合散光8.95%,单纯远视5.17%,单纯近视散光3.18%。散光程度0.50~1.00DC占52.18%,依次为1.25~2.00DC占30.02%,2.25~3.00DC占10.54%,>3.00DC占6.76%。顺规散光占94.23%,逆规散光占2.19%,斜向散光占3.58%。双眼散光中,对称散光占95.43%,不对称散光占4.57%。双眼散光占89.46%,单眼散光占10.54%。结论远视性散光是儿童散光的主要类型,顺规散光为主,双眼散光以对称散光多见,散光与弱视关系密切,科学合理矫正儿童散光眼,有利于儿童弱视防治。     

Psychophysical measurement of eye drifts and tremor by dichoptic or monocular vernier acuity

If the two segments of a vernier target are presented to different eyes, i.e. dichoptically, thresholds are three to four times higher than with presentation to the same eye. This increase in thresholds is mainly due to uncorrelated movements of both eyes, such as tremor and drifts, that occur even under steady fixation. The psychophysically measured thresholds allow one to calculate an upper estimate for the amplitudes of uncorrelated eye movements during fixation. This estimate matches the best results from direct eye position recording, with the calculated mean amplitude of eye tremor corresponding to roughly one photoreceptor diameter. The combined amplitude of both correlated and uncorrelated eye movements was also measured by delaying one segment of the vernier relative to its partner under monocular or dichoptic conditions. Fixation proved to be relatively stable, and trained observers could sustain eye position within a few min arc.     

Longitudinal study of acuity and stereopsis in infants with or at-risk for esotropia

Grating acuity and stereopsis were measured longitudinally in five groups of infants: infantile esotropes, moderate hyperopes, high hyperopes, infants with a family history of strabismus or amblyopia and controls. Grating acuity was measured with a forced-choice preferential looking procedure. Stereopsis was assessed with a random-element stereogram. Testing was conducted when subjects were 3, 6, 9, 12, 18, 24, 30 and 36 months of age. No differences among groups in absolute acuity scores or interocular acuity differences were found until the infants reached 30 and 36 months of age. At these ages, treated infantile esotropes showed acuity scores that were, on average, 0.5 octave poorer than those of controls for both the eye showing the better acuity and the eye showing the worse acuity. Stereopsis testing indicated that few, if any, of the infantile esotropes showed stereopsis at any of the test ages. Over 30% of the high hyperopes developed strabismus by age 3 years, but none of the infants in the moderate hyperopia or family history groups developed strabismus.     

Involuntary lid closure caused by defective healing of facial paralysis and its treatment with botulinum toxin

Unvoluntary lidclosure with movement of the mouth is not so rare in aberrant regeneration of nerve fibers after Bell's palsy. There was no therapy until now. 10 patients with this disease were treated with botulinum-toxin injections into the orbicularis muscle. For an average time of 11 weeks after injection there was a complete absence of synkinesis, followed by a time of 9 weeks of less complaints. Thus 2-3 injections might be sufficient treatment within a year. Complications worth mentioning, especially due to the reduced force of lidclosure, were not observed.     

Utility analysis of disability caused by amblyopia and/or strabismus in a population-based, historic cohort

Background  

Amblyopia (prevalence 3.4%) is in principle treatable, but approximately one quarter of children do not reach reading acuity in the amblyopic eye. Adults with persistent amblyopia and/or strabismus experience a decrease in quality of life. This was now quantified by patient-perceived utility values.     

Cross-coupling between accommodation and convergence is optimized for a broad range of directions and distances of gaze

Accommodation and convergence systems are cross-coupled so that stimulation of one system produces responses by both systems. Ideally, the cross-coupled responses of accommodation and convergence match their respective stimuli. When expressed in diopters and meter angles, respectively, stimuli for accommodation and convergence are equal in the mid-sagittal plane when viewed with symmetrical convergence, where historically, the gains of the cross coupling (AC/A and CA/C ratios) have been quantified. However, targets at non-zero azimuth angles, when viewed with asymmetric convergence, present unequal stimuli for accommodation and convergence. Are the cross-links between the two systems calibrated to compensate for stimulus mismatches that increase with gaze-azimuth? We measured the response AC/A and stimulus CA/C ratios at zero azimuth, 17.5 and 30 deg of rightward gaze eccentricities with a Badal Optometer and Wheatstone-mirror haploscope. AC/A ratios were measured under open-loop convergence conditions along the iso-accommodation circle (locus of points that stimulate approximately equal amounts of accommodation to the two eyes at all azimuth angles). CA/C ratios were measured under open-loop accommodation conditions along the iso-vergence circle (locus of points that stimulate constant convergence at all azimuth angles). Our results show that the gain of accommodative-convergence (AC/A ratio) decreased and the bias of convergence-accommodation increased at the 30 deg gaze eccentricity. These changes are in directions that compensate for stimulus mismatches caused by spatial-viewing geometry during asymmetric convergence.     

Risk of accidents among elderly car drivers with visual acuity equal to 6/12 or 6/15 and lack of binocular vision

To document the risk of road accidents associated with minimal visual acuity (equal to 6/12 or 6/15) and lack of binocularity (stereoacuity = 200 sec arc), 1400 drivers who had had an accident during their 70th year were compared with 2636 controls randomly selected from the 30 000 70–year–old drivers who had had no accident during the same time. Information on visual characteristics and demerit points was obtained for all subjects from the Quebec Automobile Insurance Board. Mileage and prevailing driving conditions were documented through a mail questionnaire. The relative risks of accidents were estimated while controlling for traffic convictions, mileage, time spent and frequency of driving during rush hours. Drivers with minimal visual acuity alone had the same risk of road accidents as other drivers ( OR = 0.97 Cl 95%: 0.68–1.38). The risk of accidents among drivers with both minimal visual acuity and lack of binocularity was moderately higher than among other drivers ( OR = 1.23, CI 95%: 0.88–1.72).     

Increased muscle tension and reduced elasticity of affected muscles in recent-onset Graves' disease caused primarily by active muscle contraction

In 3 patients with Graves' disease of recent onset, length-tension diagrams were made during surgery for squint under eyedrop anesthesia. The affected muscles were found to be very stiff when the other eye looked straight ahead. It was expected that these stiff muscles would be able to shorten to some extent but would be unable to lengthen, due to fibrosis of the muscle. We found that the affected muscles did not shorten very much when the other eye looked into the field of action of the muscle. Unexpectedly however, they lengthenend considerably when the other eye looked out of the field of action of the muscle. This finding implies that the raised muscle tension and reduced elasticity of affected muscles in these cases of Graves' disease of recent onset were primarily caused by active muscle contraction, not by fibrosis.     

角膜塑形镜对角膜作用的可逆性及对青少年近视的控制效果

目的探讨长期配戴角膜塑形镜对角膜的作用是否完全可逆及对青少年近视的控制效果。方法前瞻性队列研究。收集2011年1月至2013年12月在郑州大学第一附属医院眼科中心就诊配戴角膜塑形镜的近视患者55例（110眼,塑形镜组）、配戴单光足矫框架镜近视患者55例（110眼,框架镜组）,随访2年。2年后塑形镜配戴者停戴至少30 d。框架镜组：检查患者戴镜前及2年后等效球镜度（SE）及眼轴长度（AL）。塑形镜组：检查戴镜前及2年后的SE、AL、散光度、角膜平均散光（SimK）、角膜水平及垂直屈光力等以及戴镜前、各随访时间点的裸眼视力（UCVA）。采用配对t检验、独立样本t检验、重复测量单因素方差分析,Pearson相关回归对数据进行分析。结果2年后,框架镜组和塑形镜组完成随访例数分别为46例（92眼）和43例（86眼）。框架镜组和塑形镜组2年SE分别增加（-1.68±0.84）D和（-0.80±1.04）D,差异有统计学意义（t＝25.81,P<0.01）;AL分别增加（0.59±0.48）mm和（0.37±0.34）mm,差异也有统计学意义（t＝20.13,P<0.01）。塑形镜组2年后散光度及SimK较初戴时均有所增加（t=5.83、5.45,P<0.05）,分别为（0.30±0.24）D、（0.28±0.22）D;角膜水平屈光力较初戴时减小（0.31±0.18）D（t=7.43,P<0.05）;戴镜前及戴镜后各时间点UCVA差异有统计学意义,戴镜后UCVA较戴镜前均有明显提高（F=250.80,P<0.01）。结论配戴角膜塑形镜能明显提高近视患者UCVA,与框架眼镜相比,能更好地控制近视增长。长期配戴角膜塑形镜即使停戴后也较戴镜前存在散光略增加、角膜水平屈光力略变平的变化,说明角膜塑形镜作用也许并非完全可逆。     

Missing expression of pRb2/p130 in human retinoblastomas is associated with reduced apoptosis and lesser differentiation

PURPOSE: Although the retinoblastoma gene (RB/p105) has been intensely investigated as a prototype suppressor gene in humans, mutational data on the Rb family member pRb2/p130 (p130) has only recently been reported. A protective role against apoptosis has been suggested for pRb/p105, both in vitro and in vivo. However, only limited information is available on the role of pRb2/p130 in controlling apoptosis. The purpose of this study was to determine the extent of a role of this gene in the neoplasms that give the Rb family its name. METHODS: Forty-two human retinoblastomas were retrospectively examined by immunohistochemical labeling of the Rb-related proteins and the results compared with cellular kinetic characteristics: the apoptotic index (AI) and the mitotic index (MI). RESULTS: The retinoblastomas that did not express p130 showed a significantly lower AI than those that expressed p130. This result was also supported by flow cytometry on a human Saos-2 cell line that was transiently transfected with RB2/p130. The p130(-) tumors displayed a lesser degree of differentiation than the p130(+) ones. CONCLUSIONS: These observations give evidence that expression of p130 is inversely correlated with higher rates of apoptosis in human retinoblastomas and give an additional example of this regulator's role in cellular differentiation.     

Illusory spatial offset of a flash relative to a moving stimulus is caused by differential latencies for moving and flashed stimuli

A flash that is presented adjacent to a continuously moving bar is perceived to lag behind the bar. One explanation for this phenomenon is that there is a difference in the persistence of the flash and the bar. Another explanation is that the visual system compensates for the neural delays of processing visual motion information, such as the moving bar, by spatially extrapolating the bar's perceived location forward in space along its expected trajectory. Two experiments demonstrate that neither of these models is tenable. The first experiment masked the flash one video frame after its presentation. The flash was still perceived to lag behind the bar, suggesting that a difference in the persistence of the flash and bar, does not cause the apparent offset. The second experiment employed unpredictable changes in the velocity of the bar including an abrupt reversal, disappearance, acceleration, and deceleration. If the extrapolation model held, the bar would continue to be extrapolated in accordance with its initial velocity until the moment of an abrupt velocity change. The results were inconsistent with this prediction, suggesting that there is little or no spatial compensation for the neural delays of processing moving objects. The results support a new model of temporal facilitation for moving objects whereby the apparent flash lag is due to a latency advantage for moving over flashed stimuli.