Biomedical subjects

S M Code

Publications and source records attributed to S M Code.

3 recordsLinked to original sources

PubMed1992

Multimeridional apparent frontoparallel plane: relation between stimulus orientation angle and compensating tilt angle.

The classical apparent frontoparallel plane (AFPP) setting is typically obtained by having the subject move a series of parallel rods farther or closer until they line up in a plane perceived to be parallel to the face plane. If there is a size difference between the two ocular images, the AFPP setting defined by the rods will exhibit a tilt from the objective frontoparallel plane, about an axis parallel to the rods. The multimeridional apparent frontoparallel plane (MAFPP) is an extension of this procedure to rod orientations other than the vertical meridian. In previous studies, it was found that oblique tilt angle settings corresponding to rod orientations of 45 degrees and 135 degrees are equal to square root 2 times the tilt angle for the vertical rod orientation for the same interocular magnification difference along the meridian perpendicular to the rods. In this study, we measured the tilt angles produced by a series of oblique rod orientations between 15 degrees and 165 degrees, inclusive. Throughout the 150 degrees range tested, the tilt angles were found to be consistently proportional to the cosecant of the rod orientation angle, the factor square root 2 previously used being a specific example of this relation. Within this range, neither empirical cues nor the induced effect cause the cosecant relation to break down. It is suggested that the MAFPP procedure can be applied more extensively than previously anticipated.

Aniseikonia↗

PubMed1986

Objective measurement of binocular fixation misalignment.

The amount of deviation from central fixation during binocular fusion of a vertical border was compared with conventional fixation disparity measured at the same time, forced convergence serving as the independent variable. Fixation eccentricity was measured objectively by monitoring a scleral blood vessel with a video camera and by analyzing the movement, greatly magnified, on a video screen. Fixation disparity was measured conventionally by interocular nonius alignment of vertically dissociated line segments. The results agree well with previous comparisons of these responses, in which the fixation eccentricity was measured by using a technique based on the effect of retinal stimulus location on border enhancement. As in the previous experiment, the fixation misalignment was found to be many times larger than the corresponding disparity for most forced convergence values. The large discrepancy between actual fixation misalignment and fixation disparity has thus been documented objectively as well as subjectively.

Convergence, Ocular↗

PubMed1985

Retinal image quality during oblique gaze through spectacle lenses: plastic vs. glass.

The optical performance of standard plastic and glass spectacle lenses was compared at increasing angles of oblique gaze up to 40 degrees on either side of the optic axis of the lenses. For this purpose, the border enhancement method was used, a method which is suitable for monitoring small order changes in the retinal image. It was found that the enhancement band width increases with obliquity of gaze in all cases, signifying a deterioration in the retinal image. A glass lens will exaggerate this deterioration to some extent, whereas a plastic lens will exaggerate it to the greatest extent. It is shown that the relatively poorer performance of plastic is due to a relatively larger amount of narrow-angle scattering than is produced by glass.

Eyeglasses↗