Wideband Tympanometry Findings in School-aged Children: Effects of Age, Gender, Ear Laterality, and Ethnicity.

OBJECTIVES: Wideband tympanometry (WBT) measures middle-ear function across a range of frequencies (250 to 8000 Hz) while the ear-canal pressure is varied from +200 to -300 daPa. WBT is a suitable test to evaluate middle-ear function in children, but there is a lack of age-, ear-, gender-, or ethnicity-specific data throughout the literature. The purpose of this study was to investigate the effects of age, ear laterality, gender, and ethnicity on the WBT data retrieved from children aged 4 to 13 years determined to have normal middle-ear function. DESIGN: Data were collected cross-sectionally from 924 children aged 4 to 13 years who passed a test battery consisting of 226-Hz tympanometry, ipsilateral acoustic stapedial reflexes, and pure-tone screening, and without significant history of middle-ear dysfunction. Participants were grouped according to their age: 4 to 6 years, 7 to 9 years, 10 to 13 years. Wideband absorbance values were extracted at 0 daPa (WBA0) and tympanometric peak pressure (WBATPP). RESULTS: The effects of age, frequency, and pressure (WBA0 versus WBATPP) were statistically significant. There were significant differences between WBA0 and WBATPP for all age groups such that WBA0 had lower absorbance at low frequencies (250 to 1600 Hz) and greater absorbance at mid to high frequencies (2500 to 8000 Hz). Statistically significant effects of age were present for WBA0 and WBATPP such that absorbance generally increased with age from 250 to 1250 Hz and decreased with age from 2000 to 5000 Hz. There were no significant main effects of gender, ear, or ethnicity. CONCLUSIONS: Gender-, ear-, and ethnicity-specific clinical WBA0 and WBATPP norms are not required for diagnostic purposes; however, age-specific norms may be necessary. Age-related changes in middle-ear function were observed across WBA0 and WBATPP. The data presented in this study are a suitable clinical reference for evaluating the outer- and middle-ear function of school-aged children.

Speech treatment improves dysarthria in multisystemic ataxia: a rater-blinded, controlled pilot-study in ARSACS.

We aimed to provide proof-of-principle evidence that intensive home-based speech treatment can improve dysarthria in complex multisystemic degenerative ataxias, exemplified by autosomal recessive spastic ataxia Charlevoix-Saguenay (ARSACS). Feasibility and piloting efficacy of speech training specifically tailored to cerebellar dysarthria was examined through a 4-week program in seven patients with rater-blinded assessment of intelligibility (primary outcome) and naturalness and acoustic measures of speech (secondary outcomes) performed 4 weeks before, immediately prior to, and directly after training (intraindividual control design). Speech intelligibility and naturalness improved post treatment. This provides piloting evidence that ataxia-tailored speech treatment might be effective in degenerative cerebellar disease.

Experimental Pain Decreases Corticomuscular Coherence in a Force- But Not a Position-Control Task.

Differences in neural drive could explain variation in adaptation to acute pain between postural and voluntary motor actions. We investigated whether cortical contributions, quantified by corticomuscular coherence, are affected differently by acute experimental pain in more posturally focused position-control tasks and voluntary focused force-control tasks. Seventeen participants performed position- and force-control contractions with matched loads (10% maximum voluntary contraction) before and during pain (injection of hypertonic saline into the infrapatellar fat pad of the knee). Surface electromyography (EMG) of right knee extensor and flexor muscles was recorded. Electroencephalography (EEG) was recorded using a 128-channel sensor net. Corticomuscular coherence was calculated between 4 EEG electrodes that approximated the contralateral motor cortical area, and EMG. Coherence, EEG, EMG, and target performance accuracy were compared between task types and pain states. Before pain, coherence EEG and EMG did not differ between tasks. During pain, EMG increased in both tasks, but the force-control task showed greater pain interference (decreased coherence, higher EEG frequencies, and increased force fluctuations). Neural substrates of motor performance of postural functions are changed uniquely by experimental pain, which might be explained by differences in cortical demands. Our results provide new insights into the mechanisms of motor adaptations during acute pain. PERSPECTIVE: Understanding of the mechanisms underlying adaptations to motor function in acute pain is incomplete. Experimental work almost exclusively focuses on voluntary motor actions, but these adaptations may be inappropriate for postural actions. Our results show less pain-related interference in brain activity and its relationship to muscle activation during position-control tasks.

Cortical activity differs between position- and force-control knee extension tasks.

Neural control differs between position- and force-control tasks as evident from divergent effects of fatigue and pain. Unlike force-control tasks, position-control tasks focus on a postural goal to maintain a joint angle. Cortical involvement is suggested to be less during postural control, but whether this differs between position- and force-control paradigms remains unclear. Coherence estimates the functional communication between spatially distinct active regions within the cortex (cortico-cortical coherence; CCC) and between the cortex and muscles (corticomuscular coherence; CMC). We investigated whether cortical involvement differed between force-control and more posturally focused, position-control tasks. Seventeen adults performed position- and force-control knee extensor efforts at a submaximal load (10 % maximum voluntary contraction). Surface electromyography was recorded from the right knee extensor and flexor muscles and brain activity using electroencephalography (EEG). CCC and CMC in the beta (13-30 Hz) and gamma (30-45 Hz) frequency bands were calculated between combinations of intra- and inter-hemispheric pairs of electrodes, and between four EEG electrodes that approximated the left motor cortical area, and right knee extensor EMG, respectively. Differences in EEG power and muscle activity were also calculated. CCC was greater across distributed regions in the force-control task. Beta EEG power in the left hemisphere was higher for the position-control task. Although averaged CMC data differed between tasks, there was no task difference for individual CMC data. Muscle activity and force did not differ between tasks. The results demonstrate differential cortical contributions to control force- versus position-control tasks. This might contribute to differences in performance outcomes of these tasks that have been shown previously.

Specifying peripheral aberrations in visual science.

PURPOSE: Investigations of foveal aberrations assume circular pupils. However, the pupil becomes increasingly elliptical with increase in visual field eccentricity. We address this and other issues concerning peripheral aberration specification. METHODS: One approach uses an elliptical pupil similar to the actual pupil shape, stretched along its minor axis to become a circle so that Zernike circular aberration polynomials may be used. Another approach uses a circular pupil whose diameter matches either the larger or smaller dimension of the elliptical pupil. Pictorial presentation of aberrations, influence of wavelength on aberrations, sign differences between aberrations for fellow eyes, and referencing position to either the visual field or the retina are considered. RESULTS: Examples show differences between the two approaches. Each has its advantages and disadvantages, but there are ways to compensate for most disadvantages. Two representations of data are pupil aberration maps at each position in the visual field and maps showing the variation in individual aberration coefficients across the field. CONCLUSIONS: Based on simplicity of use, adequacy of approximation, possible departures of off-axis pupils from ellipticity, and ease of understanding by clinicians, the circular pupil approach is preferable to the stretched elliptical approach for studies involving field angles up to 30 deg.

Ocular aberrations in the peripheral visual field.

We modified a commercial Hartmann-Shack aberrometer and used it to measure ocular aberrations twice at each of 38 points across the central 42 degrees horizontal x 32 degrees vertical visual fields of five young emmetropic subjects. Some Zernike aberration coefficients show coefficient field distributions that were similar to the field dependence predicted by Seidel theory (astigmatism, oblique astigmatism, horizontal coma, vertical coma), but defocus did not demonstrate such similarity.

Measuring ocular aberrations in the peripheral visual field using Hartmann-Shack aberrometry.

We have used the Hartmann-Shack technique previously to measure ocular aberrations along the horizontal meridian of the visual field. This requires considerable modifications from the technique for measuring the aberrations corresponding to the fovea. We now further develop the technique so that it can be used for any meridian of the visual field. Allowance is made for any auxiliary optics placed in front of the eye to compensate for the limited range of the Hartmann-Shack technique and for the case where aberrations are estimated at a wavelength other than the measuring wavelength. Zernike wave aberrations are converted to peripheral refractions. Examples are presented showing the developments, and we discuss change in wave aberrations when converting from a circular to an elliptical pupil.

Physiologic development of tongue-jaw coordination from childhood to adulthood.

PURPOSE: This investigation aimed to examine the development of tongue-jaw coordination during speech from childhood to adolescence. METHOD: Electromagnetic articulography was used to track tongue and jaw motion in 48 children and adults (aged 6-38 years) during productions of /t/ and /k/ embedded in sentences. RESULTS: The coordinative organization of the tongue and jaw exhibited changes until the age of 8-11 years and continued to undergo refinement into late adolescence. The tongue-tip and tongue-body were observed to develop unique kinematic relations with the jaw. While tongue-tip movement became increasingly synchronized with jaw movement, tongue-body and jaw retained movement independence but developed a more consistent kinematic relation. CONCLUSION: The present results support the notion that speech motor development is nonuniform, with a refinement period from mid-childhood to late adolescence.

Electropalatographic assessment of tongue-to-palate contact patterns and variability in children, adolescents, and adults.

PURPOSE: To investigate the developmental time course of tongue-to-palate contact patterns during speech from childhood to adulthood using electropalatography (EPG) and a comprehensive profile of data analysis. METHOD: Tongue-to-palate contacts were recorded during productions of /t/, /l/, /s/, and /k/ in 48 children, adolescents and adults (aged 6-38 years) using the Reading Electropalatograph system. RESULTS: A protracted course of development for lingual control was indicated, with significant changes occurring until age 11 years; the adolescent period was in turn characterized by continual refinement of articulatory control. With maturity, a reduction in the amount of palatal contact and an anterior shift in the place of articulation was evident during anterior consonant productions, whereas the tongue-back-to-palate contact pattern became more consistent for the velar stop /k/. CONCLUSION: These results support that maturation of the speech motor system is nonuniform.

EMA assessment of tongue-jaw co-ordination during speech in dysarthria following traumatic brain injury.

PRIMARY OBJECTIVE: To investigate the spatio-timing aspects of tongue-jaw co-ordination during speech in individuals with traumatic brain injury (TBI). It was hypothesized that both timing and spatial co-ordination would be affected by TBI. RESEARCH DESIGN: A group comparison design wherein Mann-Whitney U-tests were used to compare non-neurologically impaired individuals with individuals with TBI. METHODS AND PROCEDURES: Nine non-neurologically impaired adults and nine adults with TBI were involved in the study. Electromagnetic articulography (EMA) was used to track tongue and jaw movement during /t/ and /k/, embedded in sentence and syllable stimuli. MAIN OUTCOMES AND RESULTS: Analysis of group data did not reveal a significant difference in spatio-timing tongue-jaw co-ordination between the control group and TBI group. On an individual basis, a proportion of individuals with TBI differed from non-neurologically impaired participants with regard to articulatory order and percentage of jaw contribution to /t/. CONCLUSIONS: EMA assessment results supported perceptual data; those adults who presented with severe articulatory disturbances exhibited the most deviant spatio-timing tongue-jaw co-ordination patterns. This finding could provide a new and specific direction for treatment, directed at combined movement patterns.

Shape of the retinal surface in emmetropia and myopia.

PURPOSE: To determine and compare the shapes of the retinas of emmetropic and myopic eyes. METHODS: Nonrotationally symmetrical ellipsoids were mathematically fitted to the retinal surfaces of 21 emmetropic and 66 myopic eyes (up to -12 D) of participants aged 18 to 36 years (mean, 25.5) using transverse axial and sagittal images derived from magnetic resonance imaging. RESULTS: The shapes of the ellipsoids varied considerably between subjects with similar refractive errors. The shapes were oblate (steepening toward the equator) in most of the emmetropic eyes (i.e., the axial dimensions of the ellipsoids were smaller than both the vertical and horizontal dimensions). As myopia increased, all ellipsoid dimensions increased with the axial dimension increasing more than the vertical dimension, which in turn increased more than the horizontal dimension (increases in approximate ratios 3:2:1). The relative difference in the increase of these dimensions meant that as the degree of myopia increased the retinal shape decreased in oblateness. However, few myopic eyes were prolate (flattening toward the equator). Independent of myopia, the ellipsoids were tilted about the vertical axis by 11 degrees +/- 13 degrees , and ellipsoid centers were decentered horizontally by 0.5 +/- 0.4 mm nasally and 0.2 +/- 0.5 mm inferiorly, relative to the fovea. CONCLUSIONS: In general both emmetropic and myopic retinas are oblate in shape, although myopic eyes less so. This finding may be relevant to theories implicating the peripheral retina in the development of myopia.

Introducing the pressure-sensing palatograph--the next frontier in electropalatography.

PRIMARY OBJECTIVE: To extend the capabilities of current electropalatography (EPG) systems by developing a pressure-sensing EPG system. An initial trial of a prototype pressure-sensing palate will be presented. RESEARCH DESIGN: The processes involved in designing the pressure sensors are outlined, with Hall effect transistors being selected. These units are compact, offer high sensitivity and are inexpensive. An initial prototype acrylic palate was constructed with five embedded pressure sensors. Syllable repetitions were recorded from one adult female. MAIN OUTCOMES, RESULTS AND FUTURE DIRECTIONS: The pressure-sensing palate was capable of recording dynamic tongue-to-palate pressures, with minimal to no interference to speech detected perceptually. With a restricted number of sensors, problems were encountered in optimally positioning the sensors to detect the consonant lingual pressures. Further developments are planned for various aspects of the pressure-sensing system. CONCLUSIONS: Although only in the prototype stage, the pressure-sensing palate represents the new generation of EPG. Comprehensive analysis of tongue-to-palate contacts, including pressure measures, is expected to enable more specific and effective therapeutic techniques to be developed for a variety of speech disorders.

Hartmann-Shack technique and refraction across the horizontal visual field.

We compared refractions across the horizontal visual field, based on different analyses of wave aberration obtained with a Hartmann-Shack instrument. The wave aberrations had been determined for 6-mm-diameter pupils up to at least the sixth Zernike order in five normal subjects [J. Opt. Soc. Am. A 19, 2180 (2002)]. The polynomials were converted into refractions based on 6-mm pupils and second-order Zernike aberrations (6 mm/2nd order), 3-mm pupils and second-order aberrations (3 mm/2nd order), 1-mm pupils and second-order aberrations (1 mm/2nd order), and 6-mm pupils with both second- and fourth-order aberrations (6 mm/4th order). The 3-mm/2nd-order and 6-mm/2nd-order refractions differed by as much as 0.9 D in mean sphere on axis, but the differences reduced markedly toward the edges of the visual field. The cylindrical differences between these two analyses were small at the center of the visual field (<0.3 D) but increased into the periphery to be greater than 1.0 D for some subjects. Much smaller differences in mean sphere and cylinder were found when 3-mm/2nd-order refractions and either the 1-mm/2nd-order refractions or the 6-mm/4th-order refractions were compared. The results suggest that, for determining refractions based on wave aberration data with large pupils, similar results occur by either restricting the analysis to second-order Zernike aberrations with a smaller pupil such as 3 mm or using both second- and fourth-order Zernike aberrations. Since subjective refraction is largely independent of the pupil size under photopic conditions, objective refractions based on either of these analyses may be the most useful.

The influence of the Stiles-Crawford peak location on visual performance.

We investigated the influence of the Stiles-Crawford peak location on visual acuity, contrast sensitivity and phase transfer with 6 mm diameter pupils in two subjects. Apodising filters were used to move the peak. One subject (SM) had her natural peak 0.9 mm below pupil centre, and visual performance was measured for both this peak position and when the peak was moved to the same distance above pupil centre. The other subject (DAA) had a more centred peak and visual performance was measured for this peak position and when the peak was moved both 2.3 mm temporally and 2.6 mm nasally. Measurements of contrast sensitivity and phase transfer were compared with predictions based on aberration measurements. The peak position had definite influence on performance, but this was mainly noticeable when subjects were defocused e.g. SM's visual acuity was reduced by 0.13 log units under the peak-shifted condition at -2D (hypermetropic) defocus.

Scatter and its implications for the measurement of optical image quality in human eyes.

PURPOSE: To investigate the effect of scatter on measurements of wavefront aberrations and point-spread functions in a model eye. METHODS: The wavefront aberrations of a model eye were measured using Hartmann-Shack wavefront sensing and crossed-cylinder aberroscope techniques and compared with its measured point-spread function in the presence of scattering media of different concentrations. RESULTS: The point-spread functions became broader as the concentration increased. Forward light scatter on both the light path into the eye and the light path out of the eye contributed to this broadening of the point-spread function. Neither the crossed-cylinder aberroscope nor wavefront sensing, which, respectively, measure the ocular wavefront aberrations for light entering the eye and leaving the eye, were affected by the scatter. CONCLUSION: We predict that by minimizing the contribution of the forward light scatter from one or other of these light paths by manipulating the size of the entrance and exit pupils, it should be possible to objectively assess narrow-angle forward light scatter in the eye by measuring and removing any confounding effect from wavefront aberration.

Monochromatic aberrations of human eyes in the horizontal visual field.

We measured the monochromatic aberrations of five subjects' right eyes both temporally and nasally out to 40 degrees from fixation. We used a Hartmann-Shack sensor with modifications to equipment and software to enable off-axis measurements. Results were standardized for 6-mm pupils. There was considerable variation among subjects in the pattern of aberrations. Aberrations were generally greater in the nasal visual field than in the temporal visual field; in the case of third-order aberrations, this was true for all subjects. The contribution of third-order Zernike aberrations to the root-mean-square aberration increased up to four times from the center to the edge of the field, but the contribution of fourth- to sixth-order Zernike aberrations varied little across the visual field. Results were similar to those of a previous investigation using laser ray tracing and were of the order of those predicted by Navarro's finite schematic eye.

Theoretical analysis of peripheral imaging after excimer laser corneal refractive surgery for myopia.

PURPOSE: To explore theoretically the retinal point images in the peripheral fields of eyes that have had excimer laser refractive surgery. University research laboratory. METHODS: Model eyes were based on Navarro's finite schematic eye, the eyes being made myopic by an increase in axial length. To simulate photorefractive keratectomy (PRK), the anterior shape and thickness of the cornea were modified. Variables included pupil size, ablation zone size, preexisting refractive error, and the addition of a blending zone. Image-quality criteria for each retinal point image were its size and the angular separation of the centroids of those parts of the image produced by rays passing through ablated and unablated corneal zones. RESULTS: In the peripheral visual field, the boundary between the ablated and unablated cornea caused a separation of the retinal image of a single point into 2 parts. The separation increased with the preexisting refractive error. Image quality was correspondingly reduced by ablation. As pupil size increased, the field angle at which the retinal image doubling first occurred decreased. Increasing the diameter of the ablation zone or using a blending zone increased the angle at which the doubling first occurred, and the blending zone improved image quality considerably. Chromatic effects appeared to be relatively unimportant. CONCLUSIONS: This analysis provides further evidence of the disadvantages of small central ablation zones in excimer laser refractive surgery and of the advantages of well-designed blending zones in improving postsurgical peripheral image quality. Image quality in the peripheral field of the pseudoemmetropic post-PRK eye is generally worse than in a naturally emmetropic eye, even though the axial image quality may be similar.

Influence of Stiles-Crawford apodization on visual acuity.

The Stiles-Crawford effect (SCE) of the first kind has often been considered to be important to spatial visual performance in that it ameliorates the influence of defocus and aberrations. We investigated the influence of SCE apodization on visual acuity as a function of defocus (out to +/-2 D) in four subjects. We used optical filters, conjugate with the eye's entrance pupil, that neutralized or doubled the existing SCE. With an illiterate-E task, the influence of the SCE was more noticeable for myopic defocus than for hypermetropic defocus, was generally more noticeable for high-contrast than for low-contrast letters, and increased with increase in pupil size. The greatest influence on visual acuity of neutralizing the SCE, across the subjects and range of conditions, was deterioration of 0.06 (4-mm pupil), 0.16 (6-mm pupil), and 0.29 log unit (7.6-mm pupil).

Contrast sensitivity and the Stiles--Crawford effect.

We investigated the influence of the Stiles-Crawford effect (SCE) of the first kind on the contrast sensitivity function using the apodisation model of the SCE. The SCE was measured for the right eyes of two subjects using an increment threshold technique involving a two-channel Maxwellian-viewing system. Filters made of photographic film neutralised or doubled the SCE. Contrast sensitivities were measured with a 6 mm pupil diameter, defocus to +/-2D, and three SCE conditions (normal, neutralised and doubled). Modulation transfer functions were derived after measuring transverse aberrations with a vernier alignment technique, and were used to predict contrast sensitivity functions (CSFs). The measured CSFs were, in general, reasonable matches with the predicted CSFs. In particular, both demonstrated definite undulations ("notches") as defocus level increased. The influences of the SCE-modifying filters were generally of similar magnitude and direction to predictions, thus supporting the apodisation model of the SCE. The magnitudes of SCE influence between SCE-neutralised and SCE-doubled conditions were usually small at about 0.2-0.3 log unit, with a maximum influence of 0.5 log unit. Influences of the SCE were greater for myopic than for hypermetropic defocus. As measured by the CSF and an apodisation model, this study is in agreement with previous theoretical work and one experimental study in indicating that the SCE plays a minor role in improving spatial visual performance.

The Stiles-Crawford effect and subjective measurement of aberrations.

We considered the influence that the Stiles-Crawford effect (SCE) has on the measurement of subjective monochromatic and transverse aberration measurements. The SCE was measured with a two channel Maxwellian-viewing system. Transverse aberrations were measured using a vernier alignment technique in three subjects, with the natural SCE operating, with the SCE neutralised by filters optically conjugate with the eye's pupil, and for one subject with filters that shifted the SCE by more than 2 mm. As pupil diameter increased from 1 to 5 mm diameter, without the filters the slope of the transverse aberration versus position in the pupil decreased, e.g. for chromatic aberration this decreased by approximately 90%. The filters had little influence on transverse aberration. The results indicate that subjects do not use the centroid of the image of a blurred line target for alignment, but may rely very much on other cues.