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PubMed1976

[Device for the objective determination of visual acuity].

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USSR↗

PubMed1984

The development of peripheral visual acuity in human infants. A preliminary study.

In 74 infants, we tested the resolution of gratings centered at 10 degrees in the peripheral visual field. The estimation of acuity was based on the direction of the first saccade from a fixation stimulus toward a peripheral grating stimulus. We also tested the development of the infants' "best acuity", using a method of forced-choice preferential looking (68 infants). Peripheral acuity developed dramatically in the first months of life and reached a plateau at about 4 months. By contrast, "best acuity" continued to increase significantly during the second half of the first year of age. At all ages, peripheral acuity was lower than the resolution evaluated with the same stimuli under free-viewing conditions. We conclude that, in spite of the known immaturity of the fovea in newborns (Abramov et al. 1982), even the youngest infants we tested (2 months old) showed a functional superiority of the central over the peripheral visual field.

Child Development↗

PubMed1985

Spatial frequency sweep VEP: visual acuity during the first year of life.

The grating acuity of 197 infants from 1 week to 53 weeks of age was measured using the visual evoked potential (VEP) in response to counterphase grating stimulation. The gratings were presented as a 10 sec spatial frequency sweep which spanned the acuity limit. The amplitude and phase of the second harmonic response were extracted by discrete Fourier analysis. The VEP amplitude versus spatial frequency function showed narrow spatial frequency tuning with amplitude peaks at one or more spatial frequencies. The phase of the response at medium to high spatial frequencies was generally constant at a spatial frequency peak, followed by a progressive phase lag with increasing spatial frequency. Grating acuity was estimated by linear extrapolation to zero microvolts of the highest spatial frequency peak in the VEP amplitude versus spatial frequency function. This visual acuity estimate increased from a mean of 4.5 c/deg during the first month to about 20 c/deg at 8-13 months of age. The VEP acuities at 1 month are a factor of three to five higher than previously reported for pattern reversal or pattern appearance stimuli. By 8 months VEP grating resolution was not reliably different from adult levels in the same apparatus.

Adult↗

PubMed1992

Visual acuity in the horse.

We assessed the ease with which horses could learn visual discriminations and measured their resolution acuity. We trained three horses to press their noses against one of two large wooden panels to receive a small food reward. Following training on a series of two-choice discrimination tasks, resolution acuity was measured. Although there was some variability between animals, the best acuity obtained was 23.3 c deg-1. Within the margin of error imposed by limited anatomical data, the obtained values are consistent with predictions based on retinal ganglion cell density estimates and posterior nodal distance/axial length ratios. They suggest that the resolution acuity of the horse is limited by ganglion cell density in the temporal portion of the narrow visual streak.

Animals↗

PubMed1996

[Usefulness of a school health program for detecting deficits in visual acuity].

OBJECTIVE: To evaluate the use of the school health programme to detect anomalies in visual sharpness. DESIGN: A descriptive, crossover study. SETTING: Puerto Real Health Centre (Cádiz). PATIENTS: A random sample of school-children included in the school health programme for the first year of EGB (basic) and belonging to schools located in the health district. MEASUREMENTS AND MAIN RESULTS: Visual sharpness was examined using Snellen's optotypes scale. Out of a sample of 300 children, 72 cases of deficiency were detected, 50 of them for the first time. Of 34 children with a previously unidentified deficiency who were surveyed by telephone and checked by the ophthalmologist, 22 had the suspected deficiency confirmed, treatment being prescribed for 19. This meant a minimum effectiveness of 38%, with the cases lost and not checked being considered not confirmed. CONCLUSIONS: Despite the limitations of this study, our effectiveness in detecting visual sharpness during the school health examination is quite acceptable. Therefore, we propose its continuity, incorporating some improvements in quality.

Algorithms↗

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