ABSTRACT
A computer algorithm is described which automatically controls the presentation of visual field targets and analyzes the subject's responses. Data relating to the procedure's reliability and validity are reported along with experience using it with normal subjects on an IBM PC compatible. Suggestions are made for the further development of the microcomputer approach to visual field investigations.
Subject(s)
Conditioning, Operant , Microcomputers , Vision Screening/methods , Visual Fields/physiology , Algorithms , Analysis of Variance , Humans , Reproducibility of Results , Vision Screening/instrumentationABSTRACT
Event-related potentials (ERPs) were recorded from normal right-handed males in visual-matching tasks before and after training to a high level of automaticity. The amplitude and latency of the left and right hemispheric N1 and N2 components were analyzed. While changes of N1 "after training" relative to "before training" were statistically non-significant, the N2 component appeared to be a sensitive indicator of the variability in chronometry and lateralization of cerebral processes modified by training. The N2 results suggest that with practice the physiological processes underlying performance in a visual-cognitive task become more efficient, selective and localized.
Subject(s)
Arousal , Attention , Discrimination Learning , Dominance, Cerebral , Electroencephalography , Form Perception , Memory , Mental Recall , Pattern Recognition, Visual , Adult , Evoked Potentials, Visual , Humans , Male , Overlearning , Reaction TimeABSTRACT
The wetting value is the length of a Schirmer strip wetted in millimetres for a 5 min test period plus the length of time in seconds for dry spots to appear and has been suggested as a better prognostic test than its components in isolation (Fanti and Holly, 1980). Parameters of these procedures are examined and important shortcomings in the derivation of wetting value discussed. Reliability figures are presented for the Schirmer, tear break-up and wetting value tests. The norms obtained for the tear break-up test are substantially different from those usually assumed and we recommend that practitioners should therefore rely on their own norms rather than published values.
Subject(s)
Contact Lenses , Optometry/methods , Tears , Female , Fluorescein , Fluoresceins , Humans , Male , Prognosis , Reference Values , Tears/metabolismABSTRACT
Confidence factor, missed scans and relation junction were confirmed as indices of the Dioptron II's validity. Consequently, a classification of the instrument's measurements was recommended. This gave three classes of finding, first, second and third, and it was subsequently verified that instrument test - retest reliability also related to class of result. Repetition of measurements which were not first-class improved instrument validity but only to a limited degree. The link between confidence factor, and astigmatism and cylinder angle discovered with the Dioptron I was corroborated with this version.
Subject(s)
Ophthalmology/instrumentation , Optometry/instrumentation , Refraction, Ocular , Refractive Errors/diagnosis , Computers , Humans , OphthalmoscopySubject(s)
Aging , Myopia/diagnosis , Ophthalmoscopes , Refraction, Ocular , Refractive Errors/diagnosis , Adolescent , Adult , Age Factors , Aged , Child , Child, Preschool , Humans , Infant , Middle Aged , Ophthalmoscopy/methodsABSTRACT
Two sets of multiple regression equations (prediction systems) were derived from the analysis of ocular biometric data obtained from glaucoma patients (16 open angle; 16 angle-closure) and 75 normal subjects. Discriminant scores were established for both sets of equations which minimised the number of false negatives. One set, the 'Glaucoma Equations' was applied to the data to segregate the glaucoma from the normal subjects. The other prediction system, the 'Classification Equations,' was then applied to the group defined as glaucomatous to discriminate between patients in the angle-closure and open angle categories. The performance of these equations, obtained by comparing the predicted and actual classifications for this sample, was such that between 9 and 12% of false positives and 0 and 3% false negatives were found on the 'Glaucoma Equations' and between 6 and 12% of false positives with no false negatives on the 'Classification Equations.'
Subject(s)
Eye/anatomy & histology , Glaucoma/diagnosis , Regression Analysis , Statistics as Topic , Age Factors , Anterior Chamber/anatomy & histology , Anthropometry/methods , Cornea/anatomy & histology , Female , Humans , Intraocular Pressure , Lens, Crystalline/anatomy & histology , Male , Prognosis , Refraction, Ocular , Sex Factors , Vitreous Body/anatomy & histologyABSTRACT
A method of glaucoma prediction from ocular biometric data has been described previously. A study was undertaken to evaluate the performance of the existing multiple regression equations (prediction systems) on data obtained from an independent sample consisting of 22 angle-closure glaucoma, 29 open angle glaucoma and 44 normal subjects. This performance, found by comparing the predicted and actual classification for this sample, was such that between 2 and 7% false positives and 12 and 27% false negatives were found on the equations differentiating glaucoma from normal subjects; and between 14 and 27% false positives, with 10 to 14% false negatives on the equations classifying the glaucoma subjects as angle-closure or open angle. From these results the efficiency of glaucoma prediction from ocular biometric data would appear to be equal to that of the combined tonography and provocative tests, provocation with corticosteroids and visual field screening.
