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Biomedical subjects

J H Bertera

Publications and source records attributed to J H Bertera.

7 recordsLinked to original sources
PubMed1992

Short-term, low-contrast visual acuity reduction associated with in vivo contact lens drying.

Hydrogel contact lens surfaces partially desiccate during extended interblink intervals, producing a microscopically rough and irregular surface that scatters light. Such light scattering could reduce retinal image contrast, elevating thresholds for target perception. To test this idea, we measured low (7%)-contrast visual acuity of subjects who wore: (1) hydrogel contact lenses, (2) rigid gas permeable (RGP) lenses, and (3) no contact lenses when the subjects blinked normally and when they suppressed blinking. Acuity thresholds were determined using computer-generated acuity stimuli and a staircase psychophysical procedure. Cessation of blinking resulted in small reductions in low-contrast acuity for subjects wearing RGP lenses (mean loss: 0.1 line) or no lenses (mean loss: 0.3 lines). Subjects wearing hydrogel lenses, however, generally exhibited substantial reduction of acuity (mean loss: 4.1 lines) when blinking was suppressed.

Adult↗
PubMed1992

Spatial code interference on directional responses.

The interference from an irrelevant position cue was compared in a reaction-time paradigm using voice and manual responses. The subjects were required to say 'left' or 'right' or to press left or right keys in response to arrow directions, and the arrows were presented at left or right side display positions irrelevant to the task. Display position significantly increased latency when it did not match the response to the relevant direction cue for both spatial (key-press) and non-spatial (voice) responses (73 and 59 ms, respectively). When presented alone, the position cue was processed faster than the direction cue for both manual and verbal responses. Results are discussed in terms of a common abstract mediator for left-right responses between modes and the processing speed difference between the relevant and irrelevant cue. The irrelevant left-right position code may occupy some limited-capacity channel ahead of the left-right code derived from processing the relevant direction cue.

Humans↗
PubMed1988

The effect of simulated scotomas on visual search in normal subjects.

A simulated scotoma was stabilized on the fovea of 23 normal human subjects while they searched for acuity targets in arrays of non-targets. Search time doubled with a 20 min arc scotoma, and eye fixation duration increased by about 15% when compared to no-scotoma control conditions. Search difficulty was graded by adjusting acuity target size, search element density and contrast. Search time and eye fixation duration generally increased with display difficulty in no-scotoma conditions. Results are discussed in terms of sensory loss and motor disruption due to the simulated scotoma. The simulated scotoma method may be useful in studying adaptation to visual field loss in patient populations where the size, position and severity of the scotoma can be controlled.

Adolescent↗
PubMed1979

Reading without a fovea.

A visual mask moving in synchrony with the eye obliterated foveal vision during reading under certain conditions. When foveal vision was masked, reading became difficult. In another condition, a window of readable text moved in synchrony with the eye, and parafoveal vision was masked on each fixation. The results point out the importance of foveal and parafoveal vision in reading.

Eye Movements↗
PubMed1978

Impaired visual search in alcoholics.

Visual search performance was studied in detoxified long-term alcoholics, short-term alcoholics, and nonalcoholic controls. Measures of search time and errors indicated that alcoholics had significantly longer search times than controls and that long-term alcoholics had comparatively longer search times and more shape errors in the left visual hemispace than the other groups. The results are consistent with the hypothesis that alcoholism results in subtle frontal lobe and right hemisphere dysfunctions.

Adult↗