Biomedical subjects
Publications and source records attributed to F W Fischer.
For 40 years ophthalmologists all over the world have been using the Goldmann perimeter to examine visual fields by various methods. This paper describes and summarizes the constant improvements to the instrument, the development of accessories and attachments, and examination techniques that have been introduced over the years. The Goldmann perimeter has become the accepted standard against which new perimeters are measured.
Areas of defects in the visual field can be investigated with the Goldmann perimeter in greater detail by means of free static threshold perimetry. The areas to be investigated are fixed according to the problem in question, either during or after standard perimetry, and are then checked at the threshold. As a basis the grid of supraliminal pattern perimetry on the Goldmann perimeter is taken, so that checks monitoring changes in defects can be made at the same test points. The combination of the neutral gray filter sets in the Goldmann perimeter allows threshold investigation at stimuli intervals of 1 dB. Examples of findings are used to show how free static threshold perimetry can be employed to check for defects, and particularly for the early stages of glaucoma.
This paper describes a method of supraliminal pattern perimetry for use with a Goldmann perimeter. In this method, the stimuli are adjusted in stages in accordance with the normal physiological sensitivity gradient. The threshold is determined on four meridians located 10 degrees and 30 degrees from the center. These threshold values are used to define three different levels of brightness which exceed the threshold by approximately the same amounts in three sectors of the field of vision extending from 2 degrees to 10 degrees, 10 degrees to 20 degrees and 20 degrees to 30 degrees. The points arranged in a rectangular pattern at intervals of 3 1/3 degrees are used to check for relative and absolute defects in the patient's field of vision. Supraliminal pattern perimetry can be performed manually on the Goldmann perimeter in a manner similar to automatic supraliminal perimetry to detect small defects in the field of vision. Manual perimetry, though, allows the physician to use his clinical experience directly and also makes it possible to combine screening and detection into a single procedure, since it is then possible to alter pattern density and to switch from supraliminal pattern perimetry to kinetic and free static threshold determination during the actual course of the examination. The flexibility of the manual method may well save both physician and patient time and effort, especially in difficult cases. With automatic perimetry, however, such flexibility is hampered by the fact that programs must be run through in succession (with the exception of the Octopus Program 4).
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The use of a uniform pattern for perimetry at the center of the visual field enables scotomas boundaries to be reproduced with almost complete authenticity, and small, isolated losses to be determined. As is the case with several automatic perimeters, the pattern principle can be used manually with the Goldmann projection perimeter; it is only necessary to modify the visual field scheme. The uniform pattern also permits the extent of central visual field loss to be expressed by means of a quotient which is simple to calculate.
The pattern of errors in reading isolated words was studied in two groups of children with respect, particularly, to reversals of letter sequence and letter orientation. One group (the Institute group) consisted of children 8 to 10 years old who had been diagnosed "dyslexic" according to medical and psychoeducational criteria. The other (the School group) included all the children in a second-year elementary school class (see Liberman, Shankweiler, Orlando, Harris and Berti, 1971) who fell into the lowest third on a standard test of reading achievement. Although the Institute children were somewhat poorer in word recognition than the backward readers selected purely on psychometric grounds, the groups did not differ significantly in the incidence of reversal errors. Also, for both groups, reversals represented a small proportion of the total number of reading errors. The performance of the two groups differed in two respects: in relation to directional bias in letter reversals and in the presence or absence of a significant correlation between letter-reversing and word-reversing tendencies. It was concluded from this that directional problems do not loom large in importance in most cases of reading backwardness, but may provide an additional source of difficulty for some dyslexic children. Other aspects of the error pattern were remarkably the same for both groups. The bulk of reading errors made by both groups reflect their common difficulties in phonemic segmentation of words in the lexicon, in phonetic recoding, and in mastery of the orthography--difficulties, in short, with linguistic characteristics of words rather than with their properties as visual patterns.