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A Moskowitz

Publications and source records attributed to A Moskowitz.

35 records · Page 2Linked to original sources
PubMed1985

Effect of stimulus orientation on the latency and amplitude of the VEP.

VEPs were recorded using 5.0 c/deg square wave gratings presented at vertical and oblique (45 deg) orientations and phase-alternated at two rates, 6 alternations/sec and 12 alternations/sec. In agreement with previous reports, VEP amplitude was smaller for obliquely oriented gratings than for vertically oriented gratings at both alternation rates. Unlike previous studies, however, the authors found that VEP latency was longer for obliquely oriented gratings at the slower (6/sec) alternation rate.

Adult↗
PubMed1985

Comparison of pattern VEPs and preferential-looking behavior in 3-month-old infants.

Studies of visual acuity in human infants between 1 and 6 months of age using the visual-evoked potential (VEP) and forced-choice preferential looking (FPL) have shown that acuity is one to two octaves higher by VEP estimates than by FPL estimates. In an attempt to study these differences, the authors obtained both VEP and FPL data from 26 3-month-old infants. VEP data were obtained with gratings of 0.31, 0.62, 1.25 and 2.50 cycles/deg, which were counterphase alternated at 2 Hz. FPL data were obtained for stationary gratings using either the method of constant stimuli or a staircase procedure. Our study revealed three major findings: (1) recordable VEPs can be obtained for spatial patterns that are below threshold by behavioral measures; (2) the use of different scoring criteria that yields comparable VEP and FPL group mean acuities does not yield a significant correlation between VEP amplitude acuity and FPL acuity for individual infants, probably because of the inherent "noise" in each technique; and (3) when VEP latency rather than amplitude is used to estimate acuity, there is a significant correlation between electrophysiology and behavior.

Discrimination, Psychological↗
PubMed1983

Developmental changes in the human visual system as reflected by the latency of the pattern reversal VEP.

Pattern reversal visually evoked potentials (VEPs) were recorded from 439 infants and young children ranging in age from 1 month to 5 years in response to large and small checks. Qualitative analysis of the VEP wave form showed that the first major positive component, P1, is consistently present at all ages, while the frequency of occurrence of later positive components is more variable. The proportion of infants showing late positive components increases with age; by 1 year, the frequency of occurrence of late components for large checks is more adult-like than for small checks. The latency of P1 was analyzed quantitatively. Results showed that P1 latency decreases rapidly during the first year of life for both large and small checks and that the time course of the latency change differs as a function of check size. VEPs to large checks attain adult-like P1 latency values by about 1 year of age, while the P1 latency of VEPs to small checks has still not reached adult levels by 5 years of age. Data from 12 infants tested longitudinally between 1 and 7 months of age using both checkerboards and square wave gratings show no difference in P1 latency between checkerboards and gratings comprised of large (30-240 min) pattern elements, but for patterns with small (7.5 and 15 min) elements, P1 latency to checks is significantly longer than P1 latency to stripes. These results are explained on the basis of the difference in the fundamental spatial frequency between checks and stripes.

Attention↗
PubMed1983

Evoked potential estimates of visual accommodation in infants.

Pattern reversal visually evoked potentials (VEPs) were recorded from infants between 2 and 5 months of age in order to measure their accommodative performance over a 9 diopter range (10-150 cm). Accommodation was stimulated by placing minus spherical lenses of increasing power in front of the infant's eyes and by changing the infant's distance from the stimulus. VEP latency measurements indicated that the infant's ability to maintain a zone of clear vision changes with age and pattern element size. For large checks (60 min arc), most 2- to 4-month old infants were able to maintain clear vision over the range of 9 diopters. When small checks (15 min arc) were used, the majority of 4- to 5-month old infants were unable by VEP measures to accommodate beyond 5-6 diopters. This decline in the infant's zone of clear vision with decreasing check size is due primarily to the relatively large depth of focus and poor visual resolution of the infant eye. In a small group of infants, accommodation was assessed both electrophysiologically by VEP recording and behaviorally using a preferential looking technique. Results indicated better accommodation by VEP estimates than by behavioral measures.

Accommodation, Ocular↗
PubMed1983

Evoked potential and preferential looking estimates of visual acuity in pediatric patients.

Pattern visual evoked potentials (VEPs) and behavioral visual acuity measured with forced-choice preferential looking techniques (FPL) were obtained from 172 pediatric patients between the ages of 4 months and 10 years. More children younger than 2 years of age successfully completed monocular testing by pattern VEP than by FPL methods. For children older than 2 years, we were equally successful in completing each of the two tests. Of those children who completed both tests, the VEP results agreed with Snellen, Allen, and "E" acuity measures more often (66%) than did the FPL results (50%). Both tests were more sensitive than Allen single characters in detecting interocular acuity differences in children younger than 3 years of age.

Age Factors↗
PubMed1983

Stresses in a Harrington distraction rod: their origin and relationship to fatigue fractures in vivo.

As illustrated by the case study described in this paper, in-vivo fractures of distraction rods often occur by metallurgical fatigue at the junction between the smooth and ratcheted parts of the rod (i.e., at the first ratchet junction, FRJ). To clarify causative factors of fatigue at the FRJ, stresses are analyzed in a standard 11-in. rod using both experimental and theoretical methods. The analyses reveal how distraction force, eccentricity of loading, rod geometry and material determine the stresses at the FRJ. These stresses can exceed the fatigue endurance limit for certain clinically encountered conditions.

Adult↗
PubMed1983

Recording the contralateral PERG: effect of different electrodes.

A pattern electroretinogram (PERG) can be recorded when the eye wearing the electrode is occluded and the stimulus is viewed with the other eye. We find that this phenomenon occurs when an Arden gold foil electrode is used, but not when either an ERG-Jet lens or a scleral lens electrode is used. Therefore, a corneal-type electrode should be used in PERG recording situations where the fellow eye is not occluded.

Adult↗
PubMed1983

The visual evoked potential in glaucoma and ocular hypertension: effects of check size, field size, and stimulation rate.

In order to determine the optimum stimulus conditions for the detection of optic nerve damage due to glaucoma and ocular hypertension, checkerboard pattern reversal visual evoked potentials (VEPs) were recorded from 20 glaucoma patients, 20 ocular hypertensive patients, and 20 age-matched normals. Two check sizes (12' and 48'), two field sizes (14 degrees and 28 degrees), and two alternation rates (1.9 and 7.5 alt/sec) were used. All subjects had visual acuities of 20/40 or better in each eye and equal pupils of 2 to 5 mm diameter. The largest number of VEP abnormalities were found with large checks (48') reversing at a fast rate (7.5 alt/sec). After correcting for the effects of age, visual acuity, and pupil size, 16 of 30 eyes with glaucomatous visual field defects had abnormally long VEP latencies under this condition (beyond the 99% confidence limit of the normal subjects). Nine of 40 ocular hypertensive eyes also had abnormally long latencies. Increased pattern VEP latency was significantly correlated with both the severity and location of visual field defects and the degree of cupping and pallor of the optic disc. VEP latency was not significantly related to intraocular pressure.

Adult↗
PubMed1982

Color-contingent tilt aftereffect: spatial frequency specificity.

The stimulus specificities of the color-contingent tilt aftereffect resemble those involved in the McCollough aftereffect, with the major exception that the magnitude of the former increases monotonically with the spatial frequency of matched inducing and test gratings; this monotonic increase is not found for the achromatic tilt aftereffect. Like the McCollough aftereffect, the color-contingent tilt aftereffect is tuned to the spatial frequency of the inducing gratings and can be induced on both oblique and main axes of the retina.

Color Perception↗
PubMed1981

Age-related changes in the latency of the visual evoked potential: influence of check size.

Pattern reversal visual evoked potentials were recorded from visually normal adults between 10 and 80 years of age. Two check sizes, 12 and 48 min, were used. The results showed that the latency of the first major positive component, P1, increased with age for both check sizes. This rate of increase was nearly twice as fast for 12 min checks. This difference is most likely a reflection of the differential effects of aging processes on the various spatial frequency channels in the human visual system.

Adolescent↗
PubMed1980

Long-term follow-up of scoliosis fusion.

One hundred and ten scoliotic patients underwent correction and spine fusion by one of us (J. H. M.) at Gillette Children's Hospital between 1947 and 1957. Sixty-one of these patients were evaluated in 1977 for this follow-up study. The evaluation consisted of physical and roentgenographic examination, photographs, and a detailed psychosocial analysis. The aims of the study were to evaluate: (1) the long-term stability of the fusion; (2) the incidence and severity of low-back pain; and (3) the degree of integration of the patient into society. The results showed that a solid fusion had no significant loss of correction with time. Eighty-four per cent of the patients lost only zero to 5 degrees of correction during an average follow-up of twenty-six years. Low-back pain was found to be no more frequent than in the normal population in this age group, and there was less low-back pain than in a comparable series of scoliotic patients without fusion. There was no correlation between the occurrence of low-back pain and the length or magnitude of the fused curve or the lowest extent of the fusion. An unexpected finding was the high incidence of neck pain, the cause of which is unknown. Psychosocial analysis revealed that the patients were productive, active, stable persons who were working and contributing members of society.

Adolescent↗
PubMed1980

Utility of the Arden grating test in glaucoma screening: high false-positive rate in normals over 50 years of age.

The Arden grating test was administered to 64 subjects between 6 and 82 years of age without ocular pathology, to 20 glaucoma patients, and to 21 ocular hypertensives. The results show an age effect, with significantly higher scores (lower sensitivity) in normal subjects over 50 years of age. In addition, there was no significant difference in performance between age-matched normals, glaucoma patients, and ocular hypertensives on the Arden gratings. The results show a high percentage of false-positives in older normal subjects. The Arden gratings should be used cautiously when one is testing patients over 50 years of age.

Adolescent↗
PubMedDate not supplied

Improved bioresorbable microporous intravascular stents for gene therapy.

Drug imbibing microporous stents are under development at a number of centers to enhance healing of the arterial wall after balloon coronary angioplasty procedures. The authors improved the mechanical strength and reservoir properties of a biodegradable microporous stent reported to this Society in 1994. A combined tubular/helical coil stent is readily fabricated by flotation/precipitation and casting/ winding techniques. A two stage solvent swelling technique allows precise adjustment of the surface hydrophilic/hydrophobic balance. These developments permit seven-fold improvement in drug capacity without significantly altering mechanical properties. Stents modified in this manner retain tensile and compressive strength and are suitable for remote deployment. Elution kinetics of these modified stents suggest they are suitable for gene delivery. Successful gene transfer and transmural expression have been demonstrated after implantation of stents impregnated with a recombinant adenovirus carrying a nuclear localizing beta-galactosidase reporter gene into rabbit carotid arteries. These studies suggest that surface modified, bioresorbable polymer stents ultimately may be useful adjunctive devices for gene transfer during percutaneous transluminal revascularization.

Angioplasty, Balloon↗
PubMedDate not supplied

Bioresorbable microporous stents deliver recombinant adenovirus gene transfer vectors to the arterial wall.

The use of intravascular stents as an adjunct for percutaneous transluminal revascularization is limited by two principal factors, acute thrombosis and neointimal proliferation, resulting in restenosis. To overcome these limitations, we have investigated the potential of microporous bioresorbable polymer stents formed from poly(L-lactic acid) (PLLA)/poly(epsilon-caprolactone) (PCL) blends to function both to provide mechanical support and as reservoirs for local delivery of therapeutic molecules and particles to the vessel wall. Tubular PLLA/PCL stents were fabricated by the flotation-precipitation method, and helical stents were produced by a casting/winding technique. Hybrid structures in which a tubular sheath is deposited on a helical skeleton were also generated. Using a two-stage solvent swelling technique, polyethylene oxide has been incorporated into these stents to improve hydrophilicity and water uptake, and to facilitate the ability of these devices to function as drug carriers. Stents modified in this manner retain axial and radial mechanical strength sufficient to stabilize the vessel wall against elastic recoil caused by vasoconstrictive and mechanical forces. Because of the potential of direct gene transfer into the vessel wall to ameliorate thrombosis and neointimal proliferation, we have investigated the capacity of these polymer stents to function in the delivery of recombinant adenovirus vectors to the vessel wall. In vitro, virus stock was observed to readily absorb into, and elute from these devices in an infectious form, with suitable kinetics. Successful gene transfer and expression has been demonstrated following implantation of polymer stents impregnated with a recombinant adenovirus carrying a nuclear-localizing betaGal reporter gene into rabbit carotid arteries. These studies suggest that surface-modified polymer stents may ultimately be useful adjunctive devices for both mechanical support and gene transfer during percutaneous transluminal revascularization.

Adenoviridae↗
PubMedDate not supplied

Pursuit eye movements in late-onset esotropia.

Horizontal, smooth pursuit eye movements were recorded from adults and children with infantile and late-onset esotropia using a remote, video-based, eye-movement recording system. Each subject monocularly tracked a 0.5-degree target moving back and forth on a video monitor at a constant velocity of 10 degrees, over a range of 12 degrees. Each subject's nasal and temporal gain (eye velocity/target velocity) was measured. Confirming the results of previous studies, we found that infantile esotropes had asymmetrical pursuit eye movements (nasal gain greater than temporal gain) while late-onset esotropes had symmetrical gains. However, unlike previous investigators, we found that half of the late-onset esotropes had impaired pursuit gain. The magnitude of the pursuit abnormality and the amount of refractive error were correlated--patients with the highest refractive error had the lowest pursuit gain.

Adult↗