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Biomedical subjects

K J Ciuffreda

Publications and source records attributed to K J Ciuffreda.

At least 91 records · Page 5Linked to original sources
PubMed1987

Interocular equality of tonic accommodation and consensuality of accommodative hysteresis.

Interocular differences in tonic accommodation were assessed before and after a 10 minute period of sustained monocular fixation. The fixation task was carried out once for each eye using a high-contrast target at near, and once for each eye using an empty illuminated field. Tonic accommodation increased significantly as a result of fixating the high contrast target at near, but remained stable when viewing the empty field. Close correspondence was found between the two eyes with respect to both prefixation tonic level and magnitude of tonic after-effect. Absence of interocular differences clearly demonstrates the consensuality of accommodative hysteresis.

Accommodation, Ocular↗
PubMed1986

Static vergence and accommodation: population norms and orthoptics effects.

The steady-state characteristics of the accommodation and vergence systems can be described by a model with six major oculomotor parameters. These include the system biases (tonic vergence and accommodation) and forward-loop gains (vergence and accommodative gains), as well as the interactive system gains (AC/A and CA/C ratios). We investigated these parameters in two populations: (1) 22 visually-normal asymptomatic individuals, and (2) 21 visually-abnormal symptomatic individuals before and after conventional orthoptic therapy. Two parameters related to system gain differentiated between the symptomatic and asymptomatic individuals: the slope of the fixation disparity curve with accommodation open-looped and the slope of the accommodative response/stimulus curve. Following orthoptic therapy, 4 static model parameters and 1 dynamic clinical parameter showed changes toward the normal mean; this included tonic accommodation, slope of the fixation disparity curve with accommodation closed-loop (2.5D), slope of the accommodative response/stimulus curve, the CA/C ratio, and the +/- 2D monocular accommodative flipper rate.

Accommodation, Ocular↗
PubMed1986

Different rates and amounts of vision function recovery during orthoptic therapy in an older strabismic amblyope.

Orthoptic therapy was instituted in an 11-year-old patient having deep amblyopia, constant small-angle esotropia with anomalous retinal correspondence, and a past history of minimal success with such therapy. This combination of factors pointed toward a poor prognosis for substantial recovery of vision function. Rate of recovery of several monocular and binocular vision functions was monitored during the course of 18 months of intensive orthoptic therapy. Results showed marked improvement in several monocular vision functions, suggesting presence of considerable residual neural plasticity of multiple sites in the visual pathways of this older amblyope.

Accommodation, Ocular↗
PubMed1986

Prognostic value of laser interferometric visual acuity in amblyopia therapy.

There has been no simple clinical test which accurately predicts post-therapy visual acuity in amblyopic eyes. Since grating test patterns generally yield optimal visual acuity in amblyopic eyes, the authors sought to determine if pre-therapy laser interferometric grating visual acuity would predict conventional post-therapy visual acuity in functional amblyopia. In 90% of the patients who completed therapy, the pre-therapy laser visual acuity was within two lines of the post-therapy Snellen visual acuity. Thus, pre-therapy laser visual acuity is a good prognostic indicator of conventional post-therapy visual acuity in amblyopic eyes.

Adolescent↗
PubMed1986

Vision function recovery during orthoptic therapy in an adult esotropic amblyope.

Orthoptic therapy was instituted in a 29-year-old patient having moderate amblyopia, constant small-angle esotropia, and large and steady eccentric fixation. This combination of factors, especially the age, pointed toward a poor prognosis for attainment of markedly improved vision function. Rate of recovery of several monocular vision functions was monitored during one year of orthoptic therapy. Results showed substantial improvement in most areas, thus providing evidence of neural plasticity at multiple sites in the visual pathways in this adult amblyope.

Accommodation, Ocular↗
PubMed1986

Short-term changes in tonic accommodation.

Experiments were performed to determine the diurnal variation of, as well as the influence of total darkness on, tonic accommodation. In general, under both conditions trend analysis showed that variations in tonic accommodation over time were either nonsystematic in nature or could be best described by a simple linear function. Given the relatively small range of mean tonic accommodation values over time (0.5 to 1.1 D), the results demonstrate the robustness and stability of tonic accommodation under naturally occurring viewing conditions during the course of a day. In contrast, during the 2-hr period in total darkness, tonic accommodation exhibited a three-fold increase in mean range (0.6 to 2.5 D) as well as a significant increasing linear trend in some subjects, suggesting less stability of tonic accommodation in the absence of visual stimuli.

Accommodation, Ocular↗
PubMed1986

Quantitative assessment of disparity vergence components.

Earlier evidence suggests qualitatively that at least two control modes may mediate a single vergence response. Thus, in a vergence response to step disparity, the transient component drives the initial fast dynamic portion of the response, while the sustained component maintains the latter slower portion of the response. The authors extended this hypothesis by quantitatively defining the stimulus pattern and dynamics that elicit this dichotomous behavior. The disparity target consisted of vertical lines 2 deg in height presented to each eye. Ramp disparity velocities ranged from 0.7 deg/sec to 36 deg/sec with amplitude of up to 4 deg. Photoelectric recordings of eye movements from both eyes were subtracted to give the vergence response. Fast and slow ramp stimulus velocities were found to elicit transient and sustained component responses respectively. In addition, the finding of staircase-like responses to fast ramp stimuli has strong implications on control mechanisms, indicating a sampling process in the transient component of the disparity vergence system.

Eye Movements↗
PubMed1985

Contrast and accommodation in amblyopia.

Steady-state accommodation as a function of sinusoidal and square-wave grating contrast was measured in amblyopes. The amblyopic eyes exhibited reduced average response levels and required greater contrast to sustain accommodation than the fellow dominant eye or the eyes of visually-normal control subjects. Following therapy, accommodation in the amblyopic eye markedly improved. These results suggest: reduced accommodative controller gain, reduced stimulus effectiveness of target contrast, and considerable residual visual system plasticity with respect to the neurological control pathways of accommodation, in the amblyopic eye.

Accommodation, Ocular↗
PubMed1985

Eye movements during reading: further case reports.

Eye movements during reading and nonreading tasks were measured in four patients having either Friedreich's ataxia, congenital dyslexia, acquired dyslexia with quadrantanopia, or acquired dyslexia with hemianopia. Abnormalities included saccadic intrusions, abnormally large dynamic overshoots, increased fixation duration and number of fixations, and/or reduced reading rate. The results clearly demonstrate the importance of objective eye movement recording for the precise specification of the abnormal reading pattern in patients with neurological dysfunctions.

Adult↗
PubMed1985

Clinical assessment of accommodative facility in symptomatic and asymptomatic individuals.

Clinical assessment of accommodative facility, using +/- 2.00 diopter flippers monocularly, was performed in asymptomatic and symptomatic populations in either single test sessions or multiple daily test sessions. In single session results, there was a trend for the average accommodative flipper rate to decrease as symptom level increased. The cut-off symptomatic/asymptomatic accommodative flipper rate was about 11 cycles per minute. In multiple session results, the average accommodative flipper rate, independent of symptom level, took approximately one week to asymptote to a stable level, with performance remaining at this level two weeks after termination of daily test sessions. Variability in daily flipper rate increased as symptom level increased. These results demonstrate the clinical usefulness of the +/- 2.00 diopter monocular flipper test in the screening for accommodative dysfunction.

Accommodation, Ocular↗
PubMed1985

Effect of instruction and higher level control on the accommodative response spatial frequency profile.

Although the spatial frequency dependence of accommodation is well established, characteristics of the accommodative response profile may vary significantly, thus supporting opposing theories of accommodation control. We demonstrate the pronounced influence of instruction and higher level control on such accommodation profiles. The results suggest that extreme care be taken in the methodological considerations of such experiments, as well as the need for additional systematic investigation of these factors in accommodation studies.

Accommodation, Ocular↗
PubMed1985

Subjective vergence error at near during active head rotation.

There exists some controversy regarding the effects of active horizontal head rotation on vergence error. We used a conventional, Ogle-type, subjective fixation disparity apparatus to measure vergence error at near over a full range of horizontal head-rotation frequencies. Change in vergence error rarely exceeded 10 min arc. This finding demonstrates the adequacy of the vergence system to maintain relatively accurate bifixation at near and to allow for continuous maintenance of binocular sensory-motor integrative ability, even in the presence of system perturbations.

Adult↗
PubMed1985

Orthoptic effects on accommodation and related visual functions in an adult alternating esotrope.

Orthoptic therapy was instituted in an adult, alternating esotrope with asthenopia who exhibited inaccurate static accommodative responses with adequate, clinically determined, accommodative facility. During and following therapy the patient showed considerable improvement in accommodative accuracy and related visual functions, such as contrast sensitivity, in the absence of any change in strabismic deviation. This case provides the first laboratory documentation of orthoptic effects on accommodation in an adult strabismic.

Accommodation, Ocular↗
PubMed1984

Accommodative stimulus/response function in human amblyopia.

Three parameters are essential to describe static accommodative behavior in a comprehensive, quantitative manner: the slope of the stimulus/response curve, the depth of focus, and the tonic response. These parameters were obtained in amblyopes, former amblyopes, strabismus without amblyopia, and normals. Results showed that the accommodative response in the amblyopic eye was characterized by a reduction in the slope of the stimulus/response curve and increased depth of focus. Similar abnormalities but of lesser magnitude were found in the non-dominant eye of some former amblyopes and some strabismus without amblyopia. Orthoptic therapy always increased the slope of the stimulus/response curve in the amblyopic eye. We believe that the reduced accommodative responses found in amblyopic eyes reflect a primary sensory loss over the central retinal region that occurs as a result of prolonged, early, abnormal visual experience associated with the presence of strabismus and/or anisometropia.

Accommodation, Ocular↗
PubMed1984

Reading performance and eye-movements through Varilux 2 and ST-25 lenses.

Reading rate, reading comprehension, and photoelectrically recorded eye movements while reading through Varilux 2 and ST-25 lenses were compared for seven subjects who were predominantly myopic, who ranged from 25 to 60 years of age, and who wore adds of 1.00 to 2.25 D. Tests were done at near (40 cm) and intermediate (57 cm) distances before and after a month of adaptation to the lenses using paragraphs that subtended less than 14 deg. A three-way analysis of variance indicated no significant differences in performance between the two types of lenses.

Adaptation, Ocular↗
PubMed1984

Accommodative disfacility presenting as intermittent exotropia.

Accommodative disfacility and intermittent exotropia are two common clinically-observed ocular abnormalities. However, records of individual system dynamics are rare and mechanisms for possible interactive effects between the accommodation and the vergence system remain obscure in cases of system dysfunction. We present objective, quantitative, static and dynamic records of accommodation, vergence and related system responses in a symptomatic patient having accommodation disfacility and intermittent exotropia and propose that these two conditions worked in a pathogenic symbiotic manner.

Accommodation, Ocular↗