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Biomedical subjects

K J Ciuffreda

Publications and source records attributed to K J Ciuffreda.

At least 109 records · Page 6Linked to original sources
PubMed1984

Accommodation dynamics in divergence excess exotropia.

Objective recording of accommodation dynamics was performed in four patients with divergence excess exotropia (two true and two simulated) and in three visually normal control subjects. The accommodative peak velocity/amplitude relationship was normal in the exotropic patients and in the control subjects. Latency for decreasing accommodation was increased significantly, and overshoot frequency was decreased, in the divergence excess exotropes of the true variety, thus demonstrating slightly slowed accommodation dynamics in this diagnostic group. These subtle deviations in response dynamics reflect central rather than peripheral mechanisms.

Accommodation, Ocular↗
PubMed1983

Spatial frequency dependence of accommodative responses in amblyopic eyes.

Monocular, steady-state accommodative responses were measured as a function of spatial frequency of simple sinusoidal gratings presented at high contrast and target vergence levels in amblyopes, as well as in strabismics without amblyopia and in visually-normal control subjects. In general, spatial frequency dependence of the accommodative response was the rule. However, the amblyopic eyes exhibited markedly reduced accommodative responses over most of the spatial frequency range tested, and this was attributed to reduced accommodative controller gain in the sensory pathways involved in the control of accommodation in the amblyopic eye. Due to the diversity of accommodative response spatial frequency profiles found across all groups, the results suggest that reflex, voluntary, and higher-level perceptual aspects of accommodation may interplay in a complex manner in the act of accommodation on a simple sinusoidal grating.

Accommodation, Ocular↗
PubMed1983

Saccadic intrusions contributing to reading disability: a case report.

Horizontal eye movements were recorded during tracking and reading in a patient with probable neurological involvement who complained of periods of oscillopsia and severe asthenopia, especially during reading. Saccadic intrusions occurred during all tracking tasks. Single and multiple saccadic intrusions found while reading, frequently accompanied periods of visual disturbance, and we attribute part of the reading disability to the presence of such abnormal eye movements. Various therapeutic measures were attempted and achieved some degree of success.

Adult↗
PubMed1983

Static aspects of accommodation in human amblyopia.

Static aspects of accommodation in human amblyopia were investigated. Abnormalities uncovered included decrease in accommodative controller gain, decrease in slope of the accommodative stimulus/response curve, decrease in accommodative amplitude, and increase in depth of focus. Orthoptic therapy improved accommodative function in the amblyopic eye. Similar defects, but of lesser magnitude, were frequently found in the nondominant eyes of subjects in related test groups. This included former amblyopes who had received successful orthoptic therapy in their youth, which suggested lack of complete and/or maintained recovery of accommodative function, and strabismics without amblyopia, which suggested that the effects of strabismic suppression contributed to the accommodative deficits found in some strabismic amblyopes. The accommodative abnormalities found in our amblyopes were attributed to the effects of early, prolonged, abnormal visual experience on the sensory visual system.

Accommodation, Ocular↗
PubMed1983

Vision function recovery during orthoptic therapy in an exotropic amblyope with high unilateral myopia.

Orthoptic therapy was instituted in a 6 1/2-year-old patient having deep amblyopia, constant exotropia, and high unilateral myopia. The combination of these factors pointed toward a poor prognosis for attainment of normal monocular and binocular vision function. Rates of recovery of several vision functions were monitored during orthoptic therapy. Results showed marked improvement in most areas, thus providing evidence of neural plasticity at multiple sites in the visual pathways.

Amblyopia↗
PubMed1983

Reduction of asthenopia in patients with convergence insufficiency after fusional vergence training.

Seven patients with convergence insufficiency and related asthenopia underwent automated fusional convergence training. A matched-subjects control group crossover design was used to reduce placebo effects. All patients showed significant increases in vergence ranges with concurrent marked reduction of symptoms after training. All patients showed a flattening of and an increase in the base-out portion of their fixation disparity curve. Our results demonstrated the effectiveness of fusional vergence training in reducing asthenopia in these patients. Subsequent accommodation and vergence training using traditional orthoptic procedures yielded further reduction of asthenopia, as well as an increase in the base-out fusional range.

Adolescent↗
PubMed1983

Oculomotor biofeedback therapy.

Biofeedback therapy refers to the process of gaining voluntary control over some bodily function by the immediate use of information regarding its physiological state. In this paper we review the use of oculomotor biofeedback therapy in three common ocular disorders: nystagmus, strabismus, and amblyopia. Experimental and clinical test results have been encouraging. We believe oculomotor biofeedback therapy should be attempted, either alone or in conjunction with orthoptic and/or surgical procedures, in these and other ocular disorders manifesting an abnormal oculomotor component.

Accommodation, Ocular↗
PubMed1983

Short-term adaptation to the induced effect.

The short-term adaptation (1-4 h) to the induced effect was investigated on four subjects. A 4% meridional afocal magnifier axis 180 was worn before one eye in normal binocular conditions, which produced vertical retinal-image disparity. In certain circumstances this vertical disparity will give rise to the induced effect, i.e. a surface in the objective frontal plane will appear to be rotated around a vertical axis with the apparently closer edge on the same side as the magnifying lens. Adaptation, which is considered as a reduction in the induced effect over time, was measured with a modified Howard - Dolman apparatus. Both the maximal induced effect and the maximal short-term adaptation occurred within the first 30 min and ranged from 40 to 85%. The final level of short-term adaptation to the induced effect ranged from 20 to 45%. These results suggest a rapid recalibration of binocular depth perception by higher-level perceptual centers.

Adaptation, Ocular↗
PubMed1983

Identification of accommodative vergence contribution to the near response using response variance.

An experimental method was developed to isolate accommodative and disparity vergence contributions to coordinated near vergence motor responses. The variability normally associated with the neural control signal was used as an identifying marker or tag. Using this approach, the results showed an increased variability associated with the blur-driven, accommodative vergence component that is particularly noticeable during the latter half of the movement. This indicated that accommodative vergence provides a moderate contribution to the near vergence response primarily in the late and post-transient period when the movement is essentially complete. Presence of this accommodative contribution lends further support to the "dual interactive model" of near triad control.

Accommodation, Ocular↗
PubMed1982

Use of eye movement auditory biofeedback in the control of nystagmus.

Eye movement auditory biofeedback was used in weekly training sessions to control nystagmus in five adult patients. Within the 1st hr of training, all patients were able to reduce nystagmus. Average maximum group reduction of nystagmus amplitude, peak slow-phase velocity, and frequency achieved during training with auditory biofeedback was 82, 86, and 34%, respectively. At periodic intervals during training, audio information was withheld and patients were able to maintain reduced nystagmus for several minutes. In addition, patients were able to reduce nystagmus upon command without audio cues but with conscious effort while engaging in conversation and other tasks with the experimenters. Visual acuity improvement with conscious patient effort to control nystagmus but without auditory biofeedback averaged 10% Snell-Sterling. One of two patients who returned for post-training reevaluation was able to reduce his nystagmus quickly without auditory biofeedback to 50% of the pretraining level, and both patients were able with the aid of auditory cues to reduce their nystagmus rapidly to the level achieved during training. In addition to the improvement in vision, cosmetic and psychological benefits accrued. Eye movement auditory biofeedback should be considered in the treatment of nystagmus, either alone or in conjunction with orthoptic and/or surgical procedures.

Acoustic Stimulation↗
PubMed1982

Results of intensive CAM grating treatment in a strabismic amblyope.

CAM treatment was instituted for an 8-week period in a 10-year-old patient who failed to respond well to conventional amblyopia therapy. A small, consistent, statistically significant improvement in visual acuity was found. This improvement was attributed to a change in fixation locus and to practice effects, and not to spatial frequency/orientation-dependent "reactivation" of cortical neurons involved in the development of amblyopia.

Amblyopia↗
PubMed1982

Stimulus and response AC/A ratios in intermittent exotropia of the divergence-excess type.

Objective infrared recording devices were used to measure simultaneously and continuously both accommodation and accommodative vergence to near stimuli in 4 subjects with intermittent exotropia of the divergence-excess type (2 simulated and 2 true). In addition standard clinically determined stimulus accommodative convergence to accommodation (AC/A) ratios were measured. Results showed the mean group response AC/C ratio to be 5.9/1 (range 4.5-8.0/1) with no differences between true and simulated divergence-excess. Similar AC/A ratios were found after 45 minutes of monocular occlusion. Our results clearly demonstrate relatively normal response AC/A ratios in these subjects. Thus, contrary to what is believed by many clinicians, the reduced ocular deviation at near compared with distance vision cannot be attributed primarily to an abnormally high AC/A ratio. We believe than fusional convergence after-effects and/or proximal convergence effects contribute to inflate the clinically determined stimulus AC/A ratios.

Accommodation, Ocular↗
PubMed1982

Measurement of accommodative amplitude in amblyopia.

Monocular accommodative amplitudes were measured in amblyopic individuals by the subjective minus lens and push-up techniques and by objective dynamic retinoscopy. Accommodative amplitudes were always reduced in amblyopic eyes using the minus lens and retinoscopy techniques, but not with the push-up technique which inflated this measure. Owing to difficulty in detecting defocused stimuli with the amblyopic eye, it is suggested that the objective retinoscopic technique be used by clinicians for accurate assessment of accommodative amplitude in these patients.

Accommodation, Ocular↗
PubMed1981

Dynamic vergence eye movements in strabismus and amblyopia: asymmetric vergence.

This report investigates line-of-sight asymmetric disparity vergence in patients having either intermittent strabismus, constant strabismus with amblyopia, or amblyopia without strabismus. We find an absence of disparity vergence in all patients with strabismus and in some with amblyopia only. Accommodative vergence and saccades place the dominant eye on the targets moving in depth. These accommodative vergence responses have normal dynamic characteristics, thus indicating a properly functioning vergence motor system. We purpose there is a higher-level central defect in which incoming information of one eye is suppressed, so that the disparity vergence system is rendered inoperable.

Adolescent↗
PubMed1980

An unexpected role for normal accommodative vergence in strabismus and amblyopia.

Accommodative vergence was measured using the Müller experimental paradigm in which target movement along the line of sight of the viewing eye results in large movement of the fellow (covered) eye. Our paper demonstrates an unexpected predominance of accommodative vergence over disparity vergence in patients with constant strabismus amblyopia, intermittent strabismus, and amblyopia without strabismus. Comparison of accommodative vergence responses in these patients with responses from normal subjects using symmetrical and asymmetrical targets under binocular and monocular conditions established the normal character of the patients' accommodative vergence and the absence of disparity vergence in most of them. The intermittent absence of disparity vergence in certain of our patients--some with surgically corrected strabismus, some with moderate amblyopia, and some with amblyopia treated with orthoptics--raises questions of clinical and neurophysiological interest. Preliminary results on the effects of amblyopia on accommodative responses are also presented.

Accommodation, Ocular↗
PubMed1980

Unequal saccades during vergence.

An examination of saccades during vergence eye movements (accommodative and disparity) reveals that binocular saccades have unequal magnitudes in each eye, the smaller saccade of each pair opposing the vergence movement. Furthermore, this inequality cannot be explained by linear summation of the saccadic amplitudes onto the ongoing vergence. Saccadic inequalities are usually greater at the start of the vergence; the amplitude of the smaller saccade may be reduced 70% from that of the larger. Using a sixth-order nonlinear model of the eye movement plant and linear summation of saccadic (pulse-step) and vergence (step) control signals to drive the plant, we have produced a reduction in saccadic amplitudes between the two eyes during vergence that is similar to those found in our subjects. These results suggest that the reduction of saccadic amplitudes is due to an interaction in the muscular system moving the eye, not to a nonlinear neuronal interaction more centrally located.

Accommodation, Ocular↗
PubMed1980

Increased drift in amblyopic eyes.

Reports are conflicting on the presence of increased drift in amblyopic eyes. Furthermore, the individual effects of either amblyopia or strabismus alone on ocular drift have not been systematically investigated. We therefore used a photoelectric method to record horizontal eye position during monocular and binocular fixation in patients having amblyopia without strabismus, intermittent strabismus, or constant strabismus amblyopia. Our principal finding was increased drift amplitude (up to 3.5 degree) and velocity (up to 3.0 degrees per second) in amblyopic eyes during monocular fixation. While increased drift was found 75% of the time in amblyopia without strabismus and 50% of the time in constant strabismus amblyopia, it was found only 20% of the time in intermittent strabismus. Amblyopic drift could be either error-producing or error-correcting in nature. Increased drift was not present during monocular fixation with the dominant eye or during binocular fixation in any of our 16 patients. We therefore conclude that amblyopia and not strabismus is a necessary condition for the presence of markedly increased fixational drift. Increased drift amplitude but not velocity may adversely affect visual acuity in the amblyopic eye.

Adolescent↗