Titre : | High- and Low-contrast Letter Acuity during Image Motion in Normal Observers and Observers with Infantile Nystagmus Syndrome |
Type de document : | article de périodique |
Auteurs : | Harold E. Bedell ; Sop Song |
Année de publication : | 2021 |
Langues : | Français (fre) |
Descripteurs (mots clés) : | [Thésaurus HELB]:Photographie:contrastes [Thésaurus Mesh]Acuité visuelle [Thésaurus Mesh]Enfant [Thésaurus Mesh]Lecture [Thésaurus Mesh]Nystagmus physiologique
|
Mots-clés : | syndrome du nystagmus infantile |
Résumé : | SIGNIFICANCE: High-contrast acuity in individuals with infantile nystagmus syndrome (INS) is poorer than
expected from their ongoing retinal image motion, indicating a sensory loss. Conversely, acuity for larger
low-contrast letters in these observers may be limited by image motion alone.
PURPOSE: The aim of this study was to assess visual acuity for letters of different contrast in normal observers and
individuals with idiopathic INS under conditions of comparable retinal image motion.
METHODS: Visual acuity was measured using projected Landolt C charts in 3 normal observers and 11 observers
with presumed idiopathic INS. Normal observers viewed each chart after reflection from a front-surface mirror that
underwent continuous 4-Hz ramp motion with amplitudes ranging from 4 to 9.6° and simulated foveation durations of 20 to 80 milliseconds. Observers with INS viewed the charts directly. By reciprocally varying the luminance
of the projected charts and a superimposed veiling source, Landolt C's were presented on a background luminance
of 43 cd/m2 with Weber contrasts between −12 and −89%.
RESULTS: Whereas normal observers' high-contrast acuity during imposed image motion depends only on the duration of the simulated foveation periods, acuity for low-contrast optotypes also worsens systematically as motion intensity (frequency amplitude) increases. For comparable parameters of retinal image motion, high-contrast acuity in
all but one of the observers with INS was poorer than in normal observers. On the other hand, low-contrast acuity
in the two groups of observers was similar when the retinal image motion was comparable.
CONCLUSIONS: Reduced high-contrast acuity in observers with INS appears to be attributable primarily to a sensory deficit. On the other hand, the reduction of low-contrast acuity in observers with INS may be accounted for on
the basis of retinal image motion. |
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