Jerome Feldman

Random-dot-stereogram performance by strabismic, amblyopic, and ocular-pathology patients in an operant-discrimination task.

Abstract Stereopsis performance was assessed in 88 optometric patients using an operant match‐to‐sample discrimination task involving random dot stereograms (RDSs). All normals passed the RDS test, and all constant strabismics without amblyopia, microtropes, and amblyopic strabismics failed. Only a portion of anisometropic amblyopes, intermittent strabismics, and ocular‐pathology patients passed. The findings were interpreted as indicating that stereopsis with a RDS may be better predicted and explained in terms of binocular fusion and bifoveal alignment than by visual acuity.

Developing visual and reading efficiency in older adults.

The authors hypothesized that adults, ages 62 to 75 years, who are in good health for their age can be trained to read more efficiently using approaches similar to those reported for younger individuals. Recruited successively from the State College of Optometrys primary care clinic, the subjects were 20 volunteers who had minimum corrected Snellen visual acuity of at least 6/9 (20/30) at distance and near, no oculomotor anomalies, and no significant ocular diseases such as diabetic retinitis. After a reading efficiency pretest using the Eye-trac, an infrared eye-movement recording device, the subjects were assigned to either a control group or a reading efficiency training group. Those in the control group were tested again after the control period. All subjects were retested after experimental intervention that consisted of rapid visual processing, oculomotor, and Guided Reading training. The results revealed a statistically significant and clinically meaningful improvement in all aspects of reading efficiency, including reduced number of fixations and regressions per 100 words, increased average span of recognition, and improved reading rate without loss of comprehension, only in those who received training. Our recommendation is that training in reading efficiency should be stressed to a greater extent in reading, educational, and vision therapy programs at all age levels.

Biofeedback of accommodation to reduce functional myopia

Functional myopia may be defined as the refractive condition of the eye due to spasm of the ciliary muscle. As a result of the ciliary muscle spasm, the crystalline lens becomes more convex, creating a myopic refractive condition. The normal increase and decrease in the refractive power of the crystalline lens is known as accommodation and is controlled by the autonomic nervous system innervation to the ciliary muscle. Previous studies have reported that voluntary control of accommodation is possible by biofeedback training (Cornsweet & Crane, 1973; Randle, 1970). The present research investigated the application of biofeedback control of accommodation to reduce functional myopia. A double-reversal, multiple-baseline design was used to conduct the experiment. The results revealed that the three adult male subjects achieved the preset criterion, a 1/2-diopter reduction from initial baseline to a subsequent baseline. Further analysis of the data revealed even greater changes between initial baseline and feedback periods. Although generalization to a nonexperimental environment was not trained, each subject showed a reduction in myopia and an increase in visual acuity. The results of the experiment clearly demonstrated that functional myopia is subject to voluntary control.

Operant conditioning of fusional convergence ranges using random dot stereograms.

Abstract In Experiment 1, four 6‐ to 10‐year‐old strabismic patients, who had failed to improve convergence ranges using traditional vision training techniques, were given convergence training using random dot stereograms (RDS). An integral part of the RDS training procedure was the incorporation of an operant conditioning procedure providing for response‐contingent positive reinforcement, immediate feedback, and preprogrammed systematic changes in convergence demand during discrimination learning. Findings indicated that operant RDS convergence training produced a significant increase in convergence ranges which transferred readily to vectogram tasks and resulted in a change from exotropia to exophoria for at least one patient. In Experiment 2, it was shown that improved convergence ability was a direct result of exposure to RDS of increasing convergence demand. It was concluded that young, uncooperative, language‐deficient, or inattentive patients show improved convergence ranges when such training incorporates proper stimuli and the basic principles of learning and motivation into its training regimen.

Panoramic Viewing, Visual Acuity of the Deviating Eye, and Anomalous Retinal Correspondence in the Intermittent Exotrope of the Divergence Excess Type

Abstract Monocular visual acuities in a binocular field of view, field of view under binocular conditions, and retinal correspondence were investigated in five intermittent exotropes of the divergence excess type. Results indicated that all five intermittent exotropes demonstrated (1) normal visual acuity in the deviating eye without suppressing the fixating eye, (2) a lateral extension of the temporal field of view (panoramic viewing), (3) anomalous retinal correspondence.

Operant conditioning and assessment of stereopsis in young children.

Abstract Stereopsis was assessed in 94 children ages 2‐5 yr using randomdot stereograms (RDSs) and operant conditioning. After five traditional screening tests of stereopsis, all children were trained to perform a match‐to‐sample discrimination task involving RDSs with and without lateral disparity. An added feature of the operant RDS task was the availability of monocular cue‐fading for children who failed initial RDS testing. The operant RDS test facilitated stereopsisbased responding more than the traditional clinical tests did. This finding is interpreted as indicating the importance of such factors as attention, motivation, and language ability in the assessment of stereopsis in young children.

Comparison of refractive error measurements in adults with Z-View aberrometer, Humphrey autorefractor, and subjective refraction.

BACKGROUND The aim of this study was to evaluate whether measurements obtained with the Ophthonix Z-View aberrometer (Vista, California) and a Humphrey autorefractor (Zeiss Humphrey, Dublin, California) correlate with standard subjective refraction measurements, based on visual acuity results. METHODS A retrospective data analysis was completed for 97 patients, age range 18 to 66 years, without evidence of systemic or ocular disease. All data were collected without dilation or cycloplegia. Refractive correction measurements (sphere, cylinder, axis) were converted to power vectors for analysis. RESULTS Differences-versus-means plots show generally excellent agreement between the results of each instrument and subjective refraction, all r(2) > 0.77, with the Z-View consistently exhibiting less variability than the autorefractor (AR). Nonetheless, the Z-View tends to undercorrect myopia, whereas the AR tends to overcorrect myopia, with statistically significant mean differences (±SD) in spherical equivalents with respect to subjective refraction of 0.118 (±0.311) and -0.193 (±0.474) diopters (D), respectively. Both instruments tend to overcorrect astigmatism of less than -1.25 and -0.75 D, respectively, in some cases by as much as -0.87 D. Both instruments also tend to err in cylinder axis measurement for low astigmatism, often by more than 10°. CONCLUSIONS The Ophthonix Z-View aberrometer is a useful objective clinical instrument that provides better accuracy than an AR, and its results can be used as a good starting point for a subjective refraction for most patients. It also measures higher-order aberrations not identified by other techniques. However, as with AR results, a spectacle prescription based solely on its measurements may not be appropriate for all patients.

Accommodative and vergence findings in ocular myasthenia : A case analysis

Myasthenia gravis (MG) is a neuromuscular disorder that affects skeletal muscles, in particular, the extraocular muscles. Response variability is a hallmark sign. Detailed findings are described in a patient with MG in which the presenting sign was accommodative insufficiency. Objective accommodative findings were recorded 3 years before the onset of myasthenia, soon after the initial diagnosis was made, and then after the treatment commenced with pyridostigmine. In addition, clinical measurements were obtained periodically at different times of the day for various binocular motor functions, including near point of convergence, phoria, fusional and accommodative amplitudes, and relative accommodation. The disease adversely affected all accommodative and vergence findings, with fatigue being the primary disturbance. The therapeutic administration of pyridostigmine improved static measurements of accommodation and vergence and reduced asthenopia. The objective dynamic measurements of accommodation, vergence, and versions were less affected. These findings provide a clear demonstration that both intrinsic and extrinsic ocular muscles may be affected in the prepresbyopic myasthenic patient.

Relative strength of central and peripheral fusion as a function of stimulus parameters.

We investigated the role of various stimulus parameters that influence motor fusion responses for peripheral as compared to central fusional stimuli. Results from the initial experiment indicated that a central stimulus equal in size to a peripheral fusion stimulus dominated the response independent of the amount of retinal eccentricity of the peripheral target. A second experiment indicated that the central stimulus dominated even when the peripheral stimulus was larger. However, when the peripheral stimulus was changed in shape so that it became an annulus surrounding the central stimulus, the peripheral stimulus was always stronger. In another phase of the experiment, we found that the extent to which a peripheral stimulus surrounded the central one determined which controlled the response. We concluded that the surrounding perceptual gestalt produced by the peripheral stimulus was the most significant variable determining the relative strengths of central and peripheral fusion stimuli. Clinical implications are discussed.

Comparison of fusional ranges measured by Risley prisms, vectograms, and computer orthopter.

Maximum base-in (Bl) and base-out (BO) fusional vergence ranges were measured in 38 normal subjects using 3 different clinical procedures. These procedures used different instruments, instructions, and vergence stimuli (Risley prisms, vectograms, and video-displayed contour and random dot stereograms) presented at 50.8 cm. Test-retest measures, which were taken on each test for each subject, indicated high positive correlations between test and retest measures for most vergence tests. Paired inter-test correlations among five different tests varied as a function of the pairing as well as type of measure taken (Bl, BO, break, recovery). It was concluded that different methods of measuring vergence provide different kinds of information and such tests may not be used interchangeably