NORMATIVE HOROPTER VALUES OF R 0 AND H FOR FIXATION DISTANCES OF 40CM AND 75CM

Jeremy Beatty

Abstract

PURPOSE. No population studies have been done to determine the shape and deviation of the longitudinal horopter for fixation distances of 75cm and 40cm. This study analyzes horopter data from a large sample of young adults, within 21 to 31 years of age and with normal binocular vision. METHOD. Subjects aligned test rods in an apparent frontoparallel plane (AFPP) horopter device. Three trials were taken for each subject at both fixation distances.

RESULTS. For the data, analytical plots as described by Ogle (J.O.S.A. Vol 22, 1932, 538-631) were completed. The tangent ratio R for each experimental point was plotted against the corresponding tan alpha2. The general equation for this graph is R=R0+Htan alpha2. For the 40cm fixation distance study group (n=103) the analytical plot gave the equation R=1.00+0.07tan alpha2. Non-linear regression analysis was performed by plotting the deviation against tan alpha2 to obtain a spatial plot described by y=-13.18x2+0.81x–0.11. For the 75cm fixation distance study group (n=100) the overall analytical equation was R=1.00+0.08 tan alpha2. The equation for the spatial plot was y=1.49x2–0.22x+0.04.

CONCLUSIONS. The R0 value of 1.00 for both the 40cm and the 75cm fixation distances indicates uniform relative magnification in both eyes. The H values 0.07 and 0.08 demonstrate that both horopters fall outside the Vieth-Muller circle with the 75cm horopter being flatter. This data supports earlier work done by Ogle (1932) that indicated that as fixation distance increased the horopter went from concave to flat and then convex.

Details

Year: 2001

Program Number: Poster 45

Author Affiliation: University of Missouri-St. Louis

Co-Authors: Vandana Rajaram, Luisa Neiva, Vasudevan Lakshminarayanan

Co-Author Affiliation: University of Missouri- St. Louis, University of Missouri-St. Louis, University of Missouri-St. Louis

Room: Exhibit Hall C