The Range of Ocular Torsion in Mass Screening

ABSTRACT

PURPOSE: To determine the range of cyclotorsion in the mass screening of patients by studying the spatial relationship between the optic disc and the fovea. METHODS: We examined the horizontal and vertical distances from the center of the optic disc to the fovea using the fundus photographs of 249 subjects (498 eyes) without a past history of strabismus through mass screening and then calculated the optic disc-foveal angle. We studied the differences in all the measured parameters between the right and left eyes and between men and women. RESULTS: The horizontal distance from the center of the optic disc to the fovea was 2.59+/-0.26 DD (disc diameter) in the right eye and 2.58+/-0.27 DD in the left eye. The mean horizontal distance was 2.59+/-0.26 DD. The vertical distance from the center of the optic disc to the fovea was 0.28+/-0.14 DD in the right eye and 0.30+/-0.13 DD in the left eye. The mean vertical distance was 0.29+/-0.14 DD. The calculated disc-foveal angle was 6.26+/-2.98 degrees in the right eye and 6.69+/-2.84 degrees in the left eye (mean, 6.50+/-2.92 degrees). There were no significant differences between the right and left eyes or between males and females. The 95% range of the location of the fovea was from 0.01 DD to 0.57 DD inferior to the optic disc center. CONCLUSIONS: We concluded that the clinical location of the fovea, as measured in the mass screening, extends from the center of the optic disc to the lower edge of the optic disc.