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Biomedical subjects

N Ahmedbhai

Publications and source records attributed to N Ahmedbhai.

3 recordsLinked to original sources

The influence of contact lens wear on the corneal response to ultraviolet radiation.

One eye of each of 15 male pigmented rabbits was fitted with a gas-permeable rigid contact lens. Lenses were worn on a daily basis for an initial period of 7 days with the other eye serving as a control. After this initial period the lenses were removed and both eyes were irradiated with UV-B (305 nm +/- 9 full width half maximum) using either 0.03 J cm-2 or 0.12 J cm-2 which were approximately the epithelial and endothelial damage thresholds for this waveband respectively. The responses of the cornea were followed by microscopy and pachometry. Biomicroscopically there was a dramatic difference in response between contact lens wearing and non-wearing eyes for the higher radiant exposure, whereas little difference was observed at the lower level. For both levels of radiant exposure there was a significantly less corneal thickness increase in contact lens wearing eyes after UV-B irradiation. Recovery patterns were similar.

Animals↗

Stimulus contaminants in visual electrophysiology.

Evoked cortical potentials produced by flash pattern stimulation contain contrast- and luminance-dependent components. In order to elicit contrast-specific responses, reversing checkerboards used to elicit steady-state visually evoked responses (VER's) are designed to have luminance changes in adjacent checks that are equal and opposite so that the net change in the overall checkerboard luminance is zero. Data are presented which demonstrate that commercially available, electronically generated reversing checkerboards on television monitors may contain luminance artifacts sufficiently large to elicit flicker VER's closely resembling genuine contrast VER's. These hidden luminance contaminants may result in erroneous conclusions when assessing visual mechanisms or function.

Accommodation, Ocular↗